Severe Storm Outlook Narrative (AC)
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ACUS02 KWNS 240457
SWODY2
SPC AC 240456

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1156 PM CDT Mon Apr 23 2018

Valid 251200Z - 261200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are expected over a part the southern Plains
and lower Mississippi Valley as well as the Middle-Atlantic area on
Wednesday.

...Synopsis...

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 TN Valley. This low will move
northeast through the Mid-Atlantic as an upstream shortwave trough
continues southeast through the lower Mississippi and TN 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
TX 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 TX pre-frontal warm sector.
Modest instability is expected with a corridor of 1000-1500 J/kg
MUCAPE from southwest through west central TX 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 TX 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.

..Dial.. 04/24/2018

$$


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