Aggregator

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1029 AM CST Mon Jan 16 2023 Valid 171200Z - 181200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not currently expected on Tuesday. ...Synopsis... An upper trough over the Southwest will pivot east to the central High Plains and southern Rockies vicinity by Wednesday morning. Cold midlevel temperatures and moderate southwesterly deep-layer flow will support weak elevated instability and a few lightning flashes will be possible across the Four Corners region. This elevated instability will spread east into portions of the central High Plains overnight atop a sub-freezing boundary-layer. A flash or two could accompany winter precipitation across parts of southwest NE and northwest KS in an area of strong ascent Tuesday night into early Wednesday. However, the probability of thunder with this activity is too low to include a 10 percent general thunder delineation. Further east, an upper ridge will slide east toward the MS Valley and southerly low-level flow will bring Gulf moisture northward across coastal and eastern TX into the central Gulf coast vicinity, especially overnight into Wednesday morning. While increasing boundary-layer moisture will aid in weak instability, warm midlevel temperatures appear to limit convective potential through early Wednesday morning. Enough elevated instability and large-scale forcing may exist near a warm front across northern OK to produce a couple of lightning flashes the last hour or two of the period, but probabilities are too low to include a 10 percent general thunder delineation. ..Leitman.. 01/16/2023 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1026 AM CST Mon Jan 16 2023 Valid 161630Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS EASTERN IA...NORTHWEST IL...AND THE SOUTHERN GREAT BASIN... ...SUMMARY... A couple brief tornadoes and marginally severe hail will be possible in a portion of eastern Iowa to northwest Illinois through sunset. Marginally severe hail and wind will also be possible over the southern Great Basin this afternoon into early evening. ...Eastern IA and northwest IL... Favorable wind profiles for low-topped supercells will be present in the southeast quadrant of a 994-mb surface cyclone tracking from southwest to northeast IA. Surface temperatures have warmed into the mid 50s to low 60s in a confined corridor centered on LWD-CDJ before broadening across central MO, with relatively ample insolation beneath the mid-level dry slot. The 12Z NAM and most HREF members appear much too cool within the thermal axis compared to 16Z observations. The RAP/HRRR-based guidance appear closer to reality but may be a bit too moist given an even narrower corridor of low 50s surface dew points from southwest to north-central MO. But further mixing and poleward moisture advection may be just enough, given the mid-level cold pocket of -22 to -24 C at 500 mb, to support meager MLCAPE approaching 500 J/kg towards mid-afternoon. While it is plausible that convection may fail to adequately intensify this afternoon, observational trends along with HRRR/RRFS guidance suggest the threat for a couple brief tornadoes and marginally severe hail is large enough to warrant low severe probabilities. Convection will subside quickly after sunset as it outpaces the narrow plume of weak surface-based instability. ...Southern Great Basin... A shortwave impulse centered over central CA will move east into the southern Great Basin through this evening. Ascent ahead of this wave appears favorably timed with the diurnal heating cycle to support at least isolated thunderstorm development this afternoon. However, abundant cloud coverage suggests surface warming will be limited. Nevertheless, the presence of surface dew points in the 40s should still yield meager buoyancy with MLCAPE of 250-500 J/kg. Combined with effective shear near 40 kts, the setup could support a couple updrafts with weak mid-level rotation. Marginally severe hail and wind appear to be the primary threats. ..Grams/Wendt.. 01/16/2023 Read more

MD 0066 CONCERNING WINTER MIXED PRECIPITATION FOR PARTS OF DOWNEAST INTO NORTHERN MAINE
Mesoscale Discussion 0066 NWS Storm Prediction Center Norman OK 0949 AM CST Mon Jan 16 2023 Areas affected...Parts of Downeast into northern Maine Concerning...Winter mixed precipitation Valid 161549Z - 162045Z SUMMARY...A mixture of sleet and freezing rain is expected through much of today across parts of eastern/northern Maine. DISCUSSION...A slow moving upper-level low should continue northeast today. A broad area of precipitation is noted in parts of Downeast/mid-coast Maine. This area of precipitation is moving northwestward and will eventually impact parts of the Highlands and northern Maine. Sleet and freezing rain has already been reported. With favorable surface trajectories from the northeast/north, cold air at the surface should remain for most areas through the day. The observed 12Z CAR sounding showed a warm nose at near 800 mb and model forecast soundings show this profile structure generally persisting. A mixture of primarily sleet and freezing rain is expected. Snow is also possible and will be more favored with northern extent. Temperatures in Downeast Maine are nearing freezing and other areas near the coast may do so as well. A transition to rain is possible for these southernmost areas later today. Precipitation should eventually diminish in coverage as the low continues eastward and short-wave ridging aloft builds in by this evening. ..Wendt.. 01/16/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...CAR...GYX... LAT...LON 47276789 45376727 44946727 44526854 44456943 44836986 45566987 47196885 47226835 47276789 Read more

No watches are valid as of Sun Jan 15 19:42:02 UTC 2023.

No Mesoscale Discussions are in effect as of Sun Jan 15 19:42:02 UTC 2023.

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0137 PM CST Sun Jan 15 2023 Valid 152000Z - 161200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not forecast through tonight. ...20z Update... The previous outlook remains on track and no changes are needed with the 20z update. See previous discussion below for details. ..Leitman.. 01/15/2023 .PREV DISCUSSION... /ISSUED 1019 AM CST Sun Jan 15 2023/ ...Discussion... A quiet pattern for lightning production is expected to persist through tonight, with thunderstorm probabilities appearing to be less than 10 percent. A lightning flash or two is possible this afternoon in lower elevations around the Four Corners area attendant to a shortwave trough ejecting towards the southern Rockies. Amplification of this wave is anticipated tonight as it ejects across the central Great Plains towards the Lower MO Valley. Given the poor low-level moisture sampled by 12Z soundings this morning over the central states to the western Gulf Coast, elevated thunder potential in the warm conveyor region ahead of the wave will likely hold off until after 12Z. Low-topped convection will also redevelop tonight ahead of yet another shortwave trough impinging on the central CA coast. Instability is expected to remain negligible through early morning and casts doubt on lightning occurring along the coast prior to 12Z. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1043 AM CST Sun Jan 15 2023 Valid 161200Z - 171200Z A small Elevated area was introduced from the southeastern TX Panhandle east-southeastward across parts of southwest OK and northwest TX. Through this corridor, efficient diurnal heating and continued strong downslope-flow trajectories should allow temperatures to warm into the mid/upper 60s to lower 70s -- despite weak low/mid-level cold air advection behind the front. With increased confidence in these temperatures supporting 20-25 percent RH amid 20 mph sustained westerly surface winds, the Elevated highlights are warranted -- especially with fine fuels being further conditioned today/Sunday. ..Weinman.. 01/15/2023 .PREV DISCUSSION... /ISSUED 0157 AM CST Sun Jan 15 2023/ ...Synopsis... On Monday, the mid-level trough and surface cyclone will move east into the Midwest. In the wake of this system, some gusty westerly winds are expected across the central and southern Plains. However, cool temperatures will arrive behind the cold front and keep relative humidity too high to support a significant fire weather threat. Elsewhere, a combination of moist or cool conditions will preclude any fire weather concerns. ...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 1041 AM CST Sun Jan 15 2023 Valid 151700Z - 161200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SOUTHERN AND CENTRAL HIGH PLAINS... The forecast remains on track, and only minor adjustments were made to the ongoing Elevated and Critical areas based on the latest observations and high-resolution guidance. As expected, widespread mid/high-level clouds have stunted boundary-layer heating/mixing over the risk area thus far. However, strengthening downslope flow and at least pockets of heating amid cloud breaks should still yield a few hours of 15-20 percent RH with strong/gusty surface winds this afternoon. ..Weinman.. 01/15/2023 .PREV DISCUSSION... /ISSUED 0156 AM CST Sun Jan 15 2023/ ...Synopsis... As a mid-level trough advances across the Plains today, strong lee cyclogenesis is expected across eastern Colorado/western Kansas. This deepening cyclone will result in a tight pressure gradient and strong winds across much of the central and southern High Plains. The strongest winds are expected from far west Texas into the Texas Panhandle and southwest Kansas where deep mixing is anticipated. This will result in some stronger flow mixing to the surface and increasing sustained winds to 25 to 30 mph. In addition, dry conditions will be in place with relative humidity around 15 percent. Large fuels are still somewhat moist across this region, but fine fuels are dormant and there has been minimal precipitation in the past few weeks. Therefore, fine fuels should be sufficiently dry to support large fire potential. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1034 AM CST Sun Jan 15 2023 Valid 161200Z - 171200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorm potential appears low on Monday. ...Mid-MS Valley vicinity... A compact mid/upper shortwave trough and developing upper low will lift northeast from the central Plains to the upper Great Lakes on Monday. A surface low attendant to the shortwave trough will be located over southeast NE early Monday, while tracking northeast into WI by early Tuesday. Strong southwesterly deep-layer flow will overspread the Lower MO/Mid-MS Valleys into the upper Great Lakes vicinity, while southerly low-level flow facilitates minor boundary-layer moistening into IL/IA and vicinity. Quite a bit of spread exists in forecast guidance regarding surface temps/dewpoints. The HRRR is the most aggressive with low 50s T/Tds into central IA/northwest IL. The other end of the spectrum is the NAM with temps and dewpoints about 10-13 degrees cooler. Given that dewpoints in the 50s are still in the vicinity of the TX Coast as of Sunday morning, it appears unlikely the HRRR solution will be realized as substantial airmass modification would be needed. As a result, destabilization is expected to be very weak with little if any surface-based instability expected. Furthermore, some areas across the southeast MN/northern IA vicinity still have quite a bit of snow pack. Additionally, timing of the ejecting wave appears ill-timed with peak heating, with strongest ascent likely during the morning and early afternoon before spreading northeast. Given large model spread, little signal amid machine learning/ensemble guidance and very low probability of surface-based convection, the Marginal risk has been removed. ..Leitman.. 01/15/2023 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1019 AM CST Sun Jan 15 2023 Valid 151630Z - 161200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not forecast through tonight. ...Discussion... A quiet pattern for lightning production is expected to persist through tonight, with thunderstorm probabilities appearing to be less than 10 percent. A lightning flash or two is possible this afternoon in lower elevations around the Four Corners area attendant to a shortwave trough ejecting towards the southern Rockies. Amplification of this wave is anticipated tonight as it ejects across the central Great Plains towards the Lower MO Valley. Given the poor low-level moisture sampled by 12Z soundings this morning over the central states to the western Gulf Coast, elevated thunder potential in the warm conveyor region ahead of the wave will likely hold off until after 12Z. Low-topped convection will also redevelop tonight ahead of yet another shortwave trough impinging on the central CA coast. Instability is expected to remain negligible through early morning and casts doubt on lightning occurring along the coast prior to 12Z. ..Grams/Wendt.. 01/15/2023 Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0136 PM CST Sat Jan 14 2023 Valid 142000Z - 151200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR A PORTION OF THE SAN JOAQUIN VALLEY... ...SUMMARY... A couple low-topped supercells are possible in the San Joaquin Valley of central California between about 5 to 9 PM PST, and may yield a brief weak tornado. ...20z Update... The ongoing forecast remains on track and no changes are necessary with the 20z update. A couple of briefly strong/severe storms will be possible late this afternoon/evening. For more details, see the previous discussion below. ..Leitman.. 01/14/2023 .PREV DISCUSSION... /ISSUED 1028 AM CST Sat Jan 14 2023/ ...San Joaquin Valley... A broad rain swath across the Central Valley to the central CA coast will shift east within the warm conveyor region ahead of a shortwave trough that is west of the CA/OR border area. In its wake, a short-duration period of weak boundary-layer heating coupled with cooling mid-level temperatures/steepening lapse rates will aid in scattered low-topped convection redeveloping by early evening. Low-level winds during this time frame should be in the process of weakening while also becoming veered towards the west, but marginally adequate 0-1 km SRH may persist in the eastern portion of the valley. Speed shear above 800 mb may prove adequate for a couple discrete cells with weak mid-level updraft rotation. A funnel cloud or two, with potential for a brief weak tornado, along with small hail are the most likely hazards. Read more

No watches are valid as of Sat Jan 14 19:40:01 UTC 2023.

No Mesoscale Discussions are in effect as of Sat Jan 14 19:40:01 UTC 2023.

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0134 PM CST Sat Jan 14 2023 Valid 151200Z - 161200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SOUTHERN HIGH PLAINS... The primary change with this update was to expand the Elevated highlights northeastward across southwest and central KS to I-70, where below-average precipitation has supported drying of fine fuels (60th-75th percentile ERCs). While widespread mid/high-level cloud coverage will limit boundary-layer heating/mixing to an extent, strong deep-layer west-southwesterly downslope flow should compensate for this, and 20-25 percent minimum RH is possible. Given the potential for these dry boundary-layer conditions and 35-45 mph gusts, the Elevated highlights are warranted. Elsewhere, only minor adjustments were made to the Elevated and Critical highlights based on the latest high-resolution guidance. ..Weinman.. 01/14/2023 .PREV DISCUSSION... /ISSUED 0107 AM CST Sat Jan 14 2023/ ...Synopsis... Lee cyclogenesis will intensify across southeast Colorado during the day Sunday as the mid-level trough advances into the Plains. As this occurs, strong winds will develop across the southern High Plains. Sustained winds of 25 to 30 mph are expected across portions of the southern High Plains where heating and deeper mixing is maximized. Upper-level clouds may stunt heating somewhat and keep relative humidity somewhat higher. However, guidance is consistent enough with relative humidity of 15 to 20 percent. These meteorological conditions combined with dormant, dry fine fuels will support critical fire weather conditions. ...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 1058 AM CST Sat Jan 14 2023 Valid 141700Z - 151200Z ...Southern Plains... A small expansion of the Elevated area was made into southwest KS, western OK, and northwest TX. Mostly clear skies (outside of thin cirrus clouds) and at least a component of downslope flow off the southern Rockies should support around 25 percent minimum RH over these areas. These dry conditions, coupled with strengthening southerly surface winds (sustained near 20 mph) atop modestly receptive fuels will favor elevated conditions. ...East-central into Southeast FL... An Elevated area was added along the FL east coast roughly from Melbourne southward through Homestead, where rainfall has been below average over the last month. Water vapor and visible satellite imagery show a dry, post-frontal airmass over the Peninsula. Clear skies/efficient boundary-layer mixing and continued north-northwesterly (down-Peninsula) flow should yield 30-40 percent minimum RH. Given breezy/gusty surface winds amid the drying boundary layer, elevated conditions are expected. While locally elevated conditions are also possible farther north into northern FL this afternoon, these conditions appear too brief for highlights. ..Weinman.. 01/14/2023 .PREV DISCUSSION... /ISSUED 0106 AM CST Sat Jan 14 2023/ ...Synopsis... Lee cyclogenesis will lead to strengthening winds across portions of the central and southern Plains on Saturday. These strong winds will overlap relative humidity of 15 to 20 percent across portions of eastern New Mexico, west Texas, the TX/OK Panhandle and far western Oklahoma. Winds around 20 mph with relative humidity of 15 to 20 percent amid somewhat receptive fuels supports an Elevated delineation across this region. Some dry and breezy conditions are expected with down-peninsula flow in Florida. However, relative humidity and fuels are only marginally receptive. Therefore, no Elevated area is warranted. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1034 AM CST Sat Jan 14 2023 Valid 151200Z - 161200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not forecast on Sunday. ...Synopsis... A mid/upper trough over the western U.S. Sunday morning will shift east into the Plains by early Monday morning. This will lead to deepening lee cyclogenesis over the central High Plains, with the low tracking northeast toward the MO Valley overnight. Resulting southerly return flow will transport modest Gulf moisture northward, but 60s F dewpoints will mainly be confined to the TX coast vicinity. Nevertheless, modest boundary-layer moisture beneath cooling temperatures aloft, and increasing ascent with the ejecting mid/upper trough could foster a few lightning flashes near the surface low across northwest MO/southwest IA and vicinity during the overnight hours into early Monday morning. Warm temperatures just above 850 mb will maintain a capping inversion during the period, and despite moderate to strong deep-layer southwesterly flow, severe thunderstorm potential will remain very low. Isolated thunderstorms also will be possible Sunday morning/afternoon across parts of the Four Corners as the mid/upper trough ejects eastward. Another midlevel shortwave impulse and surface low will impinge on the CA coast by early Monday morning, and a few lightning flashes are possible as a front approaches the coast toward the end of the forecast period. ..Leitman.. 01/14/2023 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1028 AM CST Sat Jan 14 2023 Valid 141630Z - 151200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS A PORTION OF THE SAN JOAQUIN VALLEY... ...SUMMARY... A couple low-topped supercells are possible in the San Joaquin Valley of central California between about 5 to 9 PM PST and may yield a brief weak tornado. ...San Joaquin Valley... A broad rain swath across the Central Valley to the central CA coast will shift east within the warm conveyor region ahead of a shortwave trough that is west of the CA/OR border area. In its wake, a short-duration period of weak boundary-layer heating coupled with cooling mid-level temperatures/steepening lapse rates will aid in scattered low-topped convection redeveloping by early evening. Low-level winds during this time frame should be in the process of weakening while also becoming veered towards the west, but marginally adequate 0-1 km SRH may persist in the eastern portion of the valley. Speed shear above 800 mb may prove adequate for a couple discrete cells with weak mid-level updraft rotation. A funnel cloud or two, with potential for a brief weak tornado, along with small hail are the most likely hazards. ..Grams/Wendt.. 01/14/2023 Read more

No watches are valid as of Fri Jan 13 17:12:02 UTC 2023.