Severe Weather 4-14 through 4-15-23

[cheese007]

After a bit of a lull on the severe front we have a couple 15% contours out for Friday/Saturday. Friday in particular looks interesting due to th mention of all modes severe and the sig severe contour

t Discussion

   SPC AC 120722

 

   Day 3 Convective Outlook  

   NWS Storm Prediction Center Norman OK

   0222 AM CDT Wed Apr 12 2023

 

   Valid 141200Z - 151200Z

 

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF

   EASTERN KANSAS...CENTRAL/EASTERN OKLAHOMA...AND NORTH TEXAS...

 

   ...SUMMARY...

   Severe thunderstorms capable of all severe hazards, including very

   large hail, are possible over portions of eastern Kansas,

   central/eastern Oklahoma, and north Texas on Friday.

 

   ...Portions of the Southern and Central Plains...

   Broad upper troughing over the western CONUS will continue to

   gradually move eastward on Friday. A shortwave trough embedded

   within this larger upper trough is expected to eject into KS/NE

   during the afternoon, continuing northeastward through the Mid MO

   Valley during evening. 

 

   At the surface, a low initially over the western KS/NE border

   vicinity will likely develop southward/southwestward. A dryline will

   extend southward from this low across central KS and western OK into

   western parts of central TX throughout much of the day. Robust

   low-level moisture advection is anticipated east of this dryline,

   with low 60s dewpoints likely reaching central OK by Friday evening.

   Strong capping will be in place during much of the day, but

   continued moisture advection amid strong diurnal heating is expected

   to weaken the cap enough for isolated convective initiation during

   the late afternoon/early evening along the dryline. Moderate bulk

   shear and steep mid-level lapse rates will support the potential for

   discrete supercells capable of all severe hazards, including very

   large hail. Any storms that develop should be able to persist

   eastward for a few hours before succumbing to nocturnal

   stabilization. A few strong to severe thunderstorms are possible

   farther north from eastern NE into eastern KS along the cold front

   during the evening.

 

   ...Southern Appalachians into the Mid-Atlantic...

   A shortwave trough will likely track northeastward from the AL/GA

   vicinity into the Mid-Atlantic on Friday. Modest low-level moisture

   will be in place ahead of this shortwave and a weak associated

   surface low, supporting thunderstorms across the region. However,

   limited diurnal heating and poor lapse rates should temper the

   overall buoyancy, keeping the severe potential low.

 

   ..Mosier.. 04/12/2023

 

   CLICK TO GET WUUS03 PTSDY3 PRODUCT

 

   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z

   CURRENT UTC TIME: 1732Z (12:32PM), RELOAD THIS PAGE TO UPDATE THE TIME

 

 

ZCZC SPCSWOD48 ALL

   ACUS48 KWNS 120900

   SPC AC 120900

 

   Day 4-8 Convective Outlook  

   NWS Storm Prediction Center Norman OK

   0400 AM CDT Wed Apr 12 2023

 

   Valid 151200Z - 201200Z

 

   ...DISCUSSION...

   A extensive cold front is forecast to stretch from northwest WI

   southwestward into the TX Hill Country early D4/Saturday.

   Medium-range guidance suggests mid 50s dewpoints will extend into

   southern WI ahead of this front, with low 60s dewpoints reaching

   into southern IL and mid 60s dewpoints reaching the Mid-South. Steep

   mid-level lapse rates (i.e. about 7 deg C per km from 700 to 500 mb)

   will likely cover much of the Mid MS Valley and Mid-South. These

   lapse rates coupled with mid-60s dewpoints will result in moderate

   to strong buoyancy ahead of the front. Vertical shear is not

   expected to be overly strong, but should still support severe

   storms. Discrete severe storms ahead of the main cold front appear

   possible, with additional storms likely along the front itself. The

   best overlap of forcing, shear, and buoyancy is anticipated from the

   Mid-South into the Lower OH Valley, where a 15% outlook area was

   delineated.

 

   Thunderstorms are possible over the Upper OH Valley and Mid-Atlantic

   along this front on D5/Sunday as it continues eastward. Low 60s

   dewpoints may reach as far north as southern PA ahead of the front.

   A negatively tilted shortwave trough may be moving into the northern

   Mid-Atlantic as this time as well. Even with these favorable

   dynamics and moderate low-level moisture, instability is still in

   question given the poor lapse rates and likely limited heating.

   These factors limit the predictability at this forecast range.

 

   Given the moisture scouring from the previous frontal passage, the

   severe potential appears low on D6/Monday. Low-level moisture may

   begin returning on D7/Tuesday ahead of a low-latitude shortwave

   trough, suggesting some severe potential may materialize early next

   week.

 

   ..Mosier.. 04/12/2023

 

   CLICK TO GET WUUS48 PTSD48 PRODUCT

[Quincy]

Not too impressed by Friday 4/14. Current guidance suggests the dryline remains capped. The exception may be near the cold front, dryline, triple point vicinity. That’ll probably be up in Kansas or near the Kansas/Oklahoma border. 

[andyhb]

Moisture killed by cutoff low over the SE, next.

[Chinook]

An 2-d cross section across Colorado and Kansas. The development of the nighttime low-level jet goes from the 20's knots range (3-hour forecast, not shown), to 34 knots (first picture) to 46-48 knots (second picture) tonight. There are not thunderstorms expected, so this is showing that the low-level jet is a common feature, whether the moisture is there or not. It has this way of speeding up to the east of the Rockies that's probably unlike a lot of other places in the world.

 

GFS 6-hr forecast

 

GFS 9-hour forecast

 

normal view

[yoda]

Day 2 ENH up for Saturday

[Ed, snow and hurricane fan]

The loud (not severe then, now severe in South Central Los Angeles) storms at 5 am locally were not forecast.  3 km NAM has storms at peak heating IMBY.  No shear but 5000 J/Kg CAPE, it should only be pusle severe unless there is some enhanced low level vorticity on the outflow boundary from morning storms or the Gulf breeze.

[Ed, snow and hurricane fan]

^^SPC mentions 4000 J/Kg MLCAPE, weak shear, and possible out flow boundary and sea breeze triggers.   40% watch issuance.  Several HRRR runs have shown big updraft helicity SE of Houston, where the Gulf boundary would be.  https://www.spc.noaa.gov/products/md/md0526.html