- Day Three
acus02 kwns 240457
Storm Prediction Center ac 240456
Day 2 convective outlook
National Weather Service Storm Prediction Center Norman OK
1156 PM CDT Mon Apr 23 2018
Valid 251200z - 261200z
..no severe thunderstorm areas forecast...
isolated thunderstorms are expected over a part the Southern Plains
and lower Mississippi Valley as well as the middle-Atlantic area on
A couple of shortwave troughs will move through the broad synoptic
upper trough that will remain situated over the eastern two thirds
of the country on Wednesday. One such feature is a near-stationary
closed upper low located over the Tennessee Valley. This low will move
northeast through the mid-Atlantic as an upstream shortwave trough
continues southeast through the lower Mississippi and Tennessee Valley
regions. At the surface a cold front will move southeast through the
Southern Plains, while farther east an occluded low will lift
northward along the eastern Seaboard in association with the
northeast-ejecting shortwave trough.
..Southern Plains through lower Mississippi Valley...
Cold front should extend from the Great Lakes region into southwest
Texas early Wednesday and continue southeast during the day. A recent
Gulf frontal intrusion and persistent offshore flow resulting from
circulation around a low pressure area over the southeast states
suggest only partial Gulf boundary-layer modification and modest
moisture return through most of the Texas pre-frontal warm sector.
Modest instability is expected with a corridor of 1000-1500 j/kg
MUCAPE from southwest through west central Texas where modifying
Continental-polar air will have returned northwestward beneath
steeper mid-level lapse rates. Given the marginal thermodynamic
environment and weak forcing in warm sector, current indications are
that most storms will remain confined to cool side of the
southeast-advancing cold front. While a few instances of small to
marginally severe hail cannot be ruled out from southwest through
west central Texas where steeper 700-500 mb lapse rates will reside,
overall severe threat is expected to remain limited.
..middle Atlantic through a portion of the northeast states...
Isolated thunderstorms will remain possible where cooler air aloft
and slightly steeper lapse rates will reside in association with the
northeast-advancing upper low circulation. Other thunderstorms will
be possible within zone of isentropic ascent and weak
destabilization along northeast advancing occluded/warm front.