SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0150 AM CST Mon Dec 16 2024 Valid 171200Z - 181200Z ...Synopsis... Quasi zonal mid-level flow is expected to quickly amplify as ridging develops over the Western US D2/Tues. In the wake of a cold front moving across the central US the day prior, surface high pressure will quickly build over the Great Basin. The high pressure will allow for moderate offshore winds and elevated to near-critical fire-weather concerns over portions of southern CA. ...Southern California... As high pressure intensifies behind the cold front across the Great Basin and interior West, moderate offshore flow is expected to develop D2/Tues into D3/Wed. Santa Ana winds of 15-25 mph will overlap with low RH values of 10-20% across parts of Los Angeles and Ventura counties for several hours. Elevated to near-critical fire-weather conditions appear likely amid dry fuels across portions of southern CA, particularly overnight D2/Tues into D3/Wed. Some uncertainty remains regarding the strength of the winds and minimum RH values in the absence of stronger upper-level support. The best overlap of strong winds and low RH is expected late D2/Tues into early D3/Wed morning. However, if winds trend stronger and earlier as some guidance suggests, critical highlights may be needed sooner. ..Lyons.. 12/16/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0147 AM CST Mon Dec 16 2024 Valid 161200Z - 171200Z ...NO CRITICAL AREAS... ...Synopsis... Fire-weather concerns across the CONUS are minimal. A cold front trailing a strong low in southern Canada will cross the central US, allowing a much cooler air mass to settle over the western US and Rockies. Despite strong mid-level flow supporting downslope winds, poor overlap of strong winds and low humidity is expected outside of brief gusty offshore winds in southern CA. Otherwise, precipitation ahead of the front and from the prior day will augment fuels such that little or no fire-weather risk is expected. ..Lyons.. 12/16/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0147 AM CST Mon Dec 16 2024 Valid 161200Z - 171200Z ...NO CRITICAL AREAS... ...Synopsis... Fire-weather concerns across the CONUS are minimal. A cold front trailing a strong low in southern Canada will cross the central US, allowing a much cooler air mass to settle over the western US and Rockies. Despite strong mid-level flow supporting downslope winds, poor overlap of strong winds and low humidity is expected outside of brief gusty offshore winds in southern CA. Otherwise, precipitation ahead of the front and from the prior day will augment fuels such that little or no fire-weather risk is expected. ..Lyons.. 12/16/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 AM CST Mon Dec 16 2024 Valid 171200Z - 181200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are expected from the southern Plains to the Lower Ohio and Tennessee Valley vicinities and across Florida on Tuesday. Severe-thunderstorm chances are low at this time. ...Eastern OK/ArkLaTex/Ozarks Vicinity... An upper trough will deepen as it moves across the Plains to the MS Valley vicinity on Tuesday. A 500 mb jet max around 50-70 kt will become oriented from eastern OK into the Ohio Valley/lower Great Lakes area after 06z, and stronger height falls are not expected to overspread the region until the nighttime hours. At the surface, 50s to low/mid 60s F dewpoints are expected across south/east TX into the Mid-South vicinity. A strong cold front will track southeast across KS/OK during the evening, and by 06z be positioned from northern AR into southeast OK and north-central TX. This boundary will become a focus for increasing isentropic ascent and isolated to scattered thunderstorms during the overnight/early Wednesday period. Neutral height tendencies will likely suppress convection during the day across much of the area. As convection develops along the advancing cold front overnight, uncertainty remains regarding any surface-based instability overlapping with stronger vertical shear (which decreases rapidly with southward extent). Forecast soundings vary across forecast guidance, but at least weak elevated instability is expected driven by cooling aloft. Stronger elevated cores could produce small hail, given forecast lapse rates around 6.8-7 C/km amid 30+ kt effective shear magnitudes (especially from southeast OK into AR). Overall, severe potential appears quite conditional for the last 3-6 hours of the forecast period. Will hold off on including low-end hail probabilities, though a Marginal (level 1 of 5) risk may be needed in later outlooks depending on forecast trends. ...FL Peninsula... Isolated thunderstorms are expected on Tuesday as a moist airmass and at least weak instability overspread the region. Onshore, easterly low-level flow will provide convergence along an inverted surface trough. Given sufficient destabilization, this will support development of thunderstorms moving onshore through evening. Weak 0-6 km bulk shear (less than 20 kt) will preclude organized convection, and severe storms are not expected. ..Leitman.. 12/16/2024 Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 AM CST Mon Dec 16 2024 Valid 171200Z - 181200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are expected from the southern Plains to the Lower Ohio and Tennessee Valley vicinities and across Florida on Tuesday. Severe-thunderstorm chances are low at this time. ...Eastern OK/ArkLaTex/Ozarks Vicinity... An upper trough will deepen as it moves across the Plains to the MS Valley vicinity on Tuesday. A 500 mb jet max around 50-70 kt will become oriented from eastern OK into the Ohio Valley/lower Great Lakes area after 06z, and stronger height falls are not expected to overspread the region until the nighttime hours. At the surface, 50s to low/mid 60s F dewpoints are expected across south/east TX into the Mid-South vicinity. A strong cold front will track southeast across KS/OK during the evening, and by 06z be positioned from northern AR into southeast OK and north-central TX. This boundary will become a focus for increasing isentropic ascent and isolated to scattered thunderstorms during the overnight/early Wednesday period. Neutral height tendencies will likely suppress convection during the day across much of the area. As convection develops along the advancing cold front overnight, uncertainty remains regarding any surface-based instability overlapping with stronger vertical shear (which decreases rapidly with southward extent). Forecast soundings vary across forecast guidance, but at least weak elevated instability is expected driven by cooling aloft. Stronger elevated cores could produce small hail, given forecast lapse rates around 6.8-7 C/km amid 30+ kt effective shear magnitudes (especially from southeast OK into AR). Overall, severe potential appears quite conditional for the last 3-6 hours of the forecast period. Will hold off on including low-end hail probabilities, though a Marginal (level 1 of 5) risk may be needed in later outlooks depending on forecast trends. ...FL Peninsula... Isolated thunderstorms are expected on Tuesday as a moist airmass and at least weak instability overspread the region. Onshore, easterly low-level flow will provide convergence along an inverted surface trough. Given sufficient destabilization, this will support development of thunderstorms moving onshore through evening. Weak 0-6 km bulk shear (less than 20 kt) will preclude organized convection, and severe storms are not expected. ..Leitman.. 12/16/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1154 PM CST Sun Dec 15 2024 Valid 161200Z - 171200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe storms are not expected today or tonight. ...Synopsis... A progressive mid-level trough over the northern Plains is forecast to move eastward and intensify over the Great Lakes tonight. As the upper trough strengths, so too will an attendant surface cyclone moving across southern Canada. As the low moves east, an accompanying cold front will be in place from Ontario to the ArkLaTex. This front will move east southeastward through much of the day before weakening and stalling across northeast TX this evening into early Tuesday. Scattered to numerous thunderstorms are expected from the lower OH Valley to the ArklaTex, with isolated storms possible across western OR and southern FL. ...Ozarks and the ArkLaTex... Along and south of the front, low-level advection of a seasonably moist air mass will support scattered to numerous storms overnight, prior to the Day 1 period across eastern OK and the Ozark Plateau. These storms, a few of which could be stronger, will likely continue through daybreak as residual buoyancy and moderate deep-layer shear slowly weaken. Any strong storm activity should quickly wane as the upper trough departs to the northeast and storms begin to move north of the more buoyant warm sector. Convection should gradually redevelop across northern LA, central/southern AR, into northeast TX later this afternoon into the evening. While muted from lingering cloud cover, forecast soundings show a modest increase in buoyancy as surface temperatures warm to near 70 F amid mid 60s F dewpoints. A stronger storm or two may pose a risk for an occasional strong gust as the front moves slowly southeast. However, decreasing large-scale ascent with mid-level height rises and weakening vertical shear suggest limited potential for storm organization and longevity. This, along with modest low and mid-level lapse rates should keep severe potential below 5%. ..Lyons/Grams.. 12/16/2024 Read more

MD 2269 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PARTS OF NORTHEASTERN OKLAHOMA...NORTHWESTERN ARKANSAS...SOUTHERN MISSOURI
Mesoscale Discussion 2269 NWS Storm Prediction Center Norman OK 1001 PM CST Sun Dec 15 2024 Areas affected...parts of northeastern Oklahoma...northwestern Arkansas...southern Missouri Concerning...Severe potential...Watch unlikely Valid 160401Z - 160630Z Probability of Watch Issuance...5 percent SUMMARY...A substantive increase in thunderstorm development appears likely across the Ozarks Plateau vicinity into adjacent lower Ohio Valley during the Midnight-3 AM CST time frame. Initially this may include widely scattered strong storms posing a risk for marginally severe hail, particularly across parts of northeastern Oklahoma into southwestern Missouri and adjacent northwestern Arkansas. DISCUSSION...Seasonably moist low-level return flow is in the process of veering from a southwesterly to more of a westerly component in the 925-850 mb layer across eastern Oklahoma through southern Missouri. However, as moisture quality continues to increase during the next few hours, this is still forecast to lead to substantive destabilization, as mid-level heights gradually begin to fall across the southern Great Plains through Ozark Plateau vicinity. Large-scale ascent and cooling aloft appear likely to weaken inhibition sufficiently to support increasing thunderstorm development in a corridor as far east as southern Illinois and adjacent portions of the lower Ohio Valley by 08-09Z. Based on forecast soundings, destabilization across much of this swath will remain rooted above a generally cool and stable boundary layer. However, modestly steep mid-level lapse rates might contribute to sufficient conditional and convective instability to support small to marginally severe hail in widely scattered stronger initial cells, before convection becomes more widespread. Storms capable of producing severe hail may be most concentrated (in a relative sense) across northeastern Oklahoma into southwestern Missouri and adjacent northwestern Arkansas, where surface dew points are increasing to around 60F. Although destabilization may become rooted close to the surface across this area (in close proximity to the surface troughing), guidance suggests that this may coincide with low-level hodographs shrinking and trending more linear. ..Kerr/Smith.. 12/16/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LZK...SGF...TSA... LAT...LON 36909531 37979203 36299139 35469436 35769607 36909531 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0650 PM CST Sun Dec 15 2024 Valid 160100Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN OK INTO THE OZARKS... ...SUMMARY... Isolated severe hail, strong/gusty winds, and perhaps a brief tornado may occur tonight through early Monday morning from parts of eastern Oklahoma and the Ozarks. ...Synopsis... Early evening water-vapor imagery shows a pronounced shortwave trough embedded within mostly zonal westerly flow slowly amplifying across the central and northern Plains states. Stronger westerly flow south of the main shortwave is expected to expand eastward this evening, as a subtle perturbation crosses the southern Plains and moves into the Ozarks tonight. This subtle forcing for ascent will allow increasingly strong northward advection of a partially modified Gulf air mass into portions of the southern Plains, Ozarks and lower OH River Valley ahead of a cold front. ...Eastern OK and the Ozark Plateau... Weak low-level warm advection is occurring across the ArkLaTex early this evening as evidenced by showers and several weak thunderstorms from northeast TX into western AR. This should continue before intensifying with the approach of the stronger deep-layer ascent tonight. A 30-45 kt low-level jet will support moderate isentropic ascent centered over eastern OK and western AR mainly after 03z. Low to mid 60s F surface dewpoints should reach as far north as the AR/OK/MO border region supporting moderate destabilization despite poor low-level lapse rates. Delayed by the late arrival of modest large-scale forcing for ascent, convective initiation is expected late this evening into the overnight hours near the cold front from northeast OK into southwest MO, and farther southeast within the warm sector. Initial activity may be supercellullar, given 35-40 kt of deep-layer shear and 1000-2000 J/kg of MUCAPE. This suggests the stronger storms may initially be capable of some severe hail, especially with any persistent rotating updrafts. Strong low-level shear is also suggestive of a non-zero tornado and damaging wind gust threat through early Monday morning. However, this is conditional upon more unstable near-surface based parcels, which, given the poor low-level lapse rates and saturated air mass, is uncertain. Overall, the severe threat with any convection that develops should remain rather isolated, will maintain level 1 Marginal with low-end probabilities for all hazards. ..Lyons.. 12/16/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0650 PM CST Sun Dec 15 2024 Valid 160100Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN OK INTO THE OZARKS... ...SUMMARY... Isolated severe hail, strong/gusty winds, and perhaps a brief tornado may occur tonight through early Monday morning from parts of eastern Oklahoma and the Ozarks. ...Synopsis... Early evening water-vapor imagery shows a pronounced shortwave trough embedded within mostly zonal westerly flow slowly amplifying across the central and northern Plains states. Stronger westerly flow south of the main shortwave is expected to expand eastward this evening, as a subtle perturbation crosses the southern Plains and moves into the Ozarks tonight. This subtle forcing for ascent will allow increasingly strong northward advection of a partially modified Gulf air mass into portions of the southern Plains, Ozarks and lower OH River Valley ahead of a cold front. ...Eastern OK and the Ozark Plateau... Weak low-level warm advection is occurring across the ArkLaTex early this evening as evidenced by showers and several weak thunderstorms from northeast TX into western AR. This should continue before intensifying with the approach of the stronger deep-layer ascent tonight. A 30-45 kt low-level jet will support moderate isentropic ascent centered over eastern OK and western AR mainly after 03z. Low to mid 60s F surface dewpoints should reach as far north as the AR/OK/MO border region supporting moderate destabilization despite poor low-level lapse rates. Delayed by the late arrival of modest large-scale forcing for ascent, convective initiation is expected late this evening into the overnight hours near the cold front from northeast OK into southwest MO, and farther southeast within the warm sector. Initial activity may be supercellullar, given 35-40 kt of deep-layer shear and 1000-2000 J/kg of MUCAPE. This suggests the stronger storms may initially be capable of some severe hail, especially with any persistent rotating updrafts. Strong low-level shear is also suggestive of a non-zero tornado and damaging wind gust threat through early Monday morning. However, this is conditional upon more unstable near-surface based parcels, which, given the poor low-level lapse rates and saturated air mass, is uncertain. Overall, the severe threat with any convection that develops should remain rather isolated, will maintain level 1 Marginal with low-end probabilities for all hazards. ..Lyons.. 12/16/2024 Read more

No watches are valid as of Sun Dec 15 22:15:02 UTC 2024.

No Mesoscale Discussions are in effect as of Sun Dec 15 22:15:02 UTC 2024.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0310 PM CST Sun Dec 15 2024 Valid 171200Z - 231200Z Zonal upper-level flow across the CONUS will begin to amplify Tuesday into Wednesday. An upper-level ridge will develop across the West with shortwave troughs progressing through areas east of the Divide. With colder air and precipitation potential for many areas east of the Rockies, fire weather concerns will generally remain low. Some portions of the central High Plains vicinity will not observe much precipitation. Dry and windy conditions are possible in both the post-frontal environments as well as when surface lows deepen in the Plains. Given the antecedent cooler temperatures, it is not clear more than locally elevated conditions will occur. Fire weather concerns will primarily be focused in southern California as high surface pressure intensifies in the Great Basin Tuesday into Thursday. ...Southern California... Model guidance remains consistent in an enhanced offshore pressure gradient maximizing Tuesday night into Wednesday morning. There is moderate confidence in at least a low-end critical offshore pressure gradient, though models have tended to back off on the magnitude slightly over the past couple of days. The greatest level of uncertainty exists with how low RH will fall. Available high resolution guidance from the CANSAC WRF suggests 15-20% RH will be most typical. That being said, the most widespread critical fire weather may hold off until Wednesday morning when some heating will occur and winds will still be moderately strong. A brief period of critical fire weather could occur very late Tuesday and trends in guidance will continue to be monitored. Given the remaining uncertainty, 40% critical probabilities will be maintained this outlook. ..Wendt.. 12/15/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0310 PM CST Sun Dec 15 2024 Valid 171200Z - 231200Z Zonal upper-level flow across the CONUS will begin to amplify Tuesday into Wednesday. An upper-level ridge will develop across the West with shortwave troughs progressing through areas east of the Divide. With colder air and precipitation potential for many areas east of the Rockies, fire weather concerns will generally remain low. Some portions of the central High Plains vicinity will not observe much precipitation. Dry and windy conditions are possible in both the post-frontal environments as well as when surface lows deepen in the Plains. Given the antecedent cooler temperatures, it is not clear more than locally elevated conditions will occur. Fire weather concerns will primarily be focused in southern California as high surface pressure intensifies in the Great Basin Tuesday into Thursday. ...Southern California... Model guidance remains consistent in an enhanced offshore pressure gradient maximizing Tuesday night into Wednesday morning. There is moderate confidence in at least a low-end critical offshore pressure gradient, though models have tended to back off on the magnitude slightly over the past couple of days. The greatest level of uncertainty exists with how low RH will fall. Available high resolution guidance from the CANSAC WRF suggests 15-20% RH will be most typical. That being said, the most widespread critical fire weather may hold off until Wednesday morning when some heating will occur and winds will still be moderately strong. A brief period of critical fire weather could occur very late Tuesday and trends in guidance will continue to be monitored. Given the remaining uncertainty, 40% critical probabilities will be maintained this outlook. ..Wendt.. 12/15/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0155 PM CST Sun Dec 15 2024 Valid 152000Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTH TEXAS TO THE OZARKS... ...SUMMARY... Isolated severe hail, strong/gusty winds, and perhaps a tornado may occur tonight through early Monday morning from parts of north Texas to the Ozarks. ...20Z Update... The previous forecast (see below) remains on track, and no changes were needed with this update. The latest guidance indicates some potential for embedded/loosely organized cells tracking northeastward across southeast MO during the early morning hours -- mainly capable of producing small hail and/or locally strong gusts. It is unclear if this activity will be surface-based, and given marginal midlevel lapse rates/instability, severe potential appears too low to expand probabilities. ..Weinman.. 12/15/2024 .PREV DISCUSSION... /ISSUED 1030 AM CST Sun Dec 15 2024/ ...Synopsis... Gradual amplification and consolidation of upper troughing will occur through the period across parts of the northern Plains and Upper Midwest. The southern fringe of this upper trough will begin to influence and overspread portions of the central/southern Plains late this evening and overnight. The primary surface low will develop towards the international border region of northern MN/southern Canada, while partially modified Gulf moisture continues to gradually stream northward over portions of the southern Plains into the Ozarks ahead of a cold front. ...Eastern Oklahoma into Western Arkansas and Southwest Missouri... Convective initiation will likely be delayed until 03Z or later this evening across eastern OK/western AR vicinity, as low-level warm/moist advection aids in the northward transport of a moist low-level airmass. Once convection develops as glancing ascent from the approaching upper trough overspreads the warm sector, convective mode may quickly become messy, as generally southwesterly low/mid-level flow encourages updraft interactions and mergers. Even so, around 1000-2000 J/kg of MUCAPE, aided by modestly steepened mid-level lapse rates, should support robust updrafts. Coupled with sufficient (around 30-40 kt) deep-layer shear, some of this initial development could produce marginally severe hail on an isolated basis. Based on latest guidance trends showing convective initiation farther north across parts of northern OK into southwest MO, the Marginal Risk has been expanded northward to account for this initial hail threat. Poor/neutral low-level lapse rates and a generally saturated boundary-layer shown in various NAM/RAP forecast soundings limit confidence to some extent in the potential for truly surface-based thunderstorms tonight across the warm sector. Still, the presence of a 35-45 kt southwesterly low-level jet, with associated 0-1 km SRH sufficient for low-level updraft rotation, suggests a non-zero threat for a tornado along with some potential for occasional strong/gusty winds as convection spreads eastward across eastern OK into western AR and the Ozarks through early Monday morning. The potential for sustained supercells appears limited by a weakness in the flow/hodograph forecast around 700 mb, with the southward-moving cold front also encouraging a more linear/cluster mode with time. Overall, the severe threat with any convection that develops should remain rather isolated, but within a conditionally somewhat favorable environment. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0134 PM CST Sun Dec 15 2024 Valid 161200Z - 171200Z ...NO CRITICAL AREAS... No changes to the ongoing forecast. ..Wendt.. 12/15/2024 .PREV DISCUSSION... /ISSUED 0155 AM CST Sun Dec 15 2024/ ...Synopsis... A progressive and mostly zonal mid-level flow pattern is expected over the CONUS D2/Mon. A pronounced shortwave trough within the stronger westerly flow will move quickly eastward over the northern third of the CONUS. At the surface, cyclone associated with the mid-level trough will move along the US/Canadian border, trailing a cold front over the central US. In the wake of the front, a much colder air mass and modest high pressure are likely over the western 2/3rds of the US. This should keep winds relatively light and RH values elevated. Additionally precipitation ahead of the front and from the prior day will augment fuels, such that little or no fire-weather risk is expected. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0134 PM CST Sun Dec 15 2024 Valid 161200Z - 171200Z ...NO CRITICAL AREAS... No changes to the ongoing forecast. ..Wendt.. 12/15/2024 .PREV DISCUSSION... /ISSUED 0155 AM CST Sun Dec 15 2024/ ...Synopsis... A progressive and mostly zonal mid-level flow pattern is expected over the CONUS D2/Mon. A pronounced shortwave trough within the stronger westerly flow will move quickly eastward over the northern third of the CONUS. At the surface, cyclone associated with the mid-level trough will move along the US/Canadian border, trailing a cold front over the central US. In the wake of the front, a much colder air mass and modest high pressure are likely over the western 2/3rds of the US. This should keep winds relatively light and RH values elevated. Additionally precipitation ahead of the front and from the prior day will augment fuels, such that little or no fire-weather risk is expected. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2268 CONCERNING WINTER MIXED PRECIPITATION FOR PORTIONS OF WEST VIRGINIA INTO WESTERN MARYLAND AND SOUTHWESTERN PENNSYLVANIA
Mesoscale Discussion 2268 NWS Storm Prediction Center Norman OK 0930 AM CST Sun Dec 15 2024 Areas affected...portions of West Virginia into western Maryland and southwestern Pennsylvania Concerning...Winter mixed precipitation Valid 151530Z - 152030Z SUMMARY...Freezing rain should gradually increase into the late morning and early afternoon hours, with some sleet or snow also possible. Up to .06/3 hr ice accretion rates cannot be ruled out, especially in higher-terrain areas. DISCUSSION...A pronounced mid-level trough is progressing eastward across the OH Valley, encouraging low-level warm air/moisture advection over portions of the Appalachians. Here, QG ascent is supporting a broad shield of precipitation, which is beginning to approach a wedge of sub-freezing low-level temperatures over higher-terrain areas. Surface observations from Hardy County, WV to Cambria County, PA show temperatures around or below freezing, with wet bulb temperatures well below freezing over several locales. 15Z mesoanalysis continues to show 925-850 mb CAA over the higher terrain, which will further support freezing rain potential, perhaps with some sleet or snow mixed in. The best chance for .06/3hr ice accretion rates, as well as some sleet or snow, will be late this morning into the afternoon hours, as also shown by the latest HRRR and HREF probabilistic guidance. ..Squitieri.. 12/15/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...CTP...LWX...PBZ...RLX... LAT...LON 38687964 39297928 39857927 40527896 40647851 40497812 40037806 39357826 38937852 38677891 38547926 38687964 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0130 PM CST Sun Dec 15 2024 Valid 171200Z - 181200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are expected from the southern Plains to the Mid-Mississippi Valley and across Florida on Tuesday. Severe thunderstorms appear unlikely at this time. ...Synopsis... On Tuesday, a fast moving jet streak will move from the Inter Mountain West to the central Plains. This will lead to some weak lee cyclogenesis with this surface low drifting south along the Front Range through the day. The positively tilted upper trough will sharpen by Tuesday evening, and a surface low will start to develop into the Plains and eventually move somewhere near the Mid-Mississippi Valley by the end of the period. A reservoir of moderate instability will be present across the southern half of Texas on Tuesday morning with slow northward movement toward the Red River through the day. Neutral to slightly rising heights aloft will likely keep thunderstorm activity limited during the day. However, during the evening and overnight hours as the upper trough sharpens and ejects into the Plains, height falls and increasing vorticity advection combined with increasing isentropic ascent should provide ample lift for scattered thunderstorm activity Tuesday night. Forecast soundings show weak to moderate elevated instability and moderate mid-level lapse rates. As mid-level flow strengthens with the approaching jet streak, 30 to 35 knots of effective shear will likely be present along and to the north of the front. Isolated large hail may be possible in this zone after 03Z. The better chance for surface based thunderstorms will be farther south near the ArkLaTex. However, forecast soundings show weak shear that far south which would likely limit storm intensity even if surface-based convection can develop within a more unstable environment. A marginal risk may be needed for portions of the southern Plains/Ozarks in later outlooks if overlap between forcing, instability and shear becomes more clear. ..Bentley.. 12/15/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0130 PM CST Sun Dec 15 2024 Valid 171200Z - 181200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are expected from the southern Plains to the Mid-Mississippi Valley and across Florida on Tuesday. Severe thunderstorms appear unlikely at this time. ...Synopsis... On Tuesday, a fast moving jet streak will move from the Inter Mountain West to the central Plains. This will lead to some weak lee cyclogenesis with this surface low drifting south along the Front Range through the day. The positively tilted upper trough will sharpen by Tuesday evening, and a surface low will start to develop into the Plains and eventually move somewhere near the Mid-Mississippi Valley by the end of the period. A reservoir of moderate instability will be present across the southern half of Texas on Tuesday morning with slow northward movement toward the Red River through the day. Neutral to slightly rising heights aloft will likely keep thunderstorm activity limited during the day. However, during the evening and overnight hours as the upper trough sharpens and ejects into the Plains, height falls and increasing vorticity advection combined with increasing isentropic ascent should provide ample lift for scattered thunderstorm activity Tuesday night. Forecast soundings show weak to moderate elevated instability and moderate mid-level lapse rates. As mid-level flow strengthens with the approaching jet streak, 30 to 35 knots of effective shear will likely be present along and to the north of the front. Isolated large hail may be possible in this zone after 03Z. The better chance for surface based thunderstorms will be farther south near the ArkLaTex. However, forecast soundings show weak shear that far south which would likely limit storm intensity even if surface-based convection can develop within a more unstable environment. A marginal risk may be needed for portions of the southern Plains/Ozarks in later outlooks if overlap between forcing, instability and shear becomes more clear. ..Bentley.. 12/15/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1110 AM CST Sun Dec 15 2024 Valid 161200Z - 171200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorm potential is expected to be low on Monday. ...Synopsis... A mid-level trough will amplify as it advances from the central Plains to the Great Lakes on Monday. A strong surface low associated with this trough will deepen across northern Ontario with a surface front extending southward through the Great Lakes and into the southern Plains. This front will become more diffuse and eventually stall from eastern Texas to central Tennessee as the primary forcing moves into the Great Lakes. Thunderstorms will likely be ongoing at the beginning of the period from northeast Texas across southeast Oklahoma and Arkansas. While these storms may pose some severe threat before 12Z, minimal threat is expected to continue after 12Z as heights rise across the region and instability weakens through the morning. Additional instability is forecast to develop farther south across east Texas and Louisiana during the afternoon as temperatures warm into the mid 70s with dewpoints in the mid 60s. However, forcing is expected to remain weak which should keep any storm development isolated. In addition, if storms can develop, weak mid-level flow will keep deep-layer shear muted and thus limit much severe weather threat during the afternoon. ..Bentley.. 12/15/2024 Read more