ACUS01 KWNS 201939

SWODY1

SPC AC 201937



Day 1 Convective Outlook  

NWS Storm Prediction Center Norman OK

0237 PM CDT Fri Mar 20 2026



Valid 202000Z - 211200Z



...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE UPPER OH

VALLEY AND CENTRAL APPALACHIANS...



...SUMMARY...

Strong to locally severe thunderstorms are possible across parts of

the Upper Ohio Valley and central Appalachians this evening.



...20Z Update...

No changes needed to the level 1-MRGL risk. Ongoing rain swath with

very isolated thunder coverage should continue shifting

southeastward from the northern/central Appalachians. Severe

potential should be confined to its wake as the northern extent of a

modest boundary-layer moisture plume reaches the Upper OH Valley by

early evening. Despite latitudinal differences in guidance since 12Z

with placement of redevelopment this evening, the southern envelope

appears more probable given the degree of rain-cooled air to the

northeast. Convection should struggle to readily deepen/intensify

with such meager buoyancy. But hodograph elongation amid

northwesterly speed shear within the cloud-bearing layer will favor

a threat for isolated, marginal severe storms before convection

wanes overnight.



..Grams.. 03/20/2026



.PREV DISCUSSION... /ISSUED 1115 AM CDT Fri Mar 20 2026/



...Upper Ohio Valley into the Central Appalachians...

Midday water-vapor imagery indicates a mid-level shortwave trough

over Lower Michigan as a belt of strong west-northwesterly flow is

maintained across the north-central U.S. eastward to the

Mid-Atlantic and New England coastal vicinity.  This disturbance is

forecast to quickly move to the Delmarva/NJ by midnight.  



The northern extent of a moisture plume, and an airmass still

undergoing modification over the Gulf Basin, will protrude northeast

into the upper OH Valley by late afternoon.  Forecast guidance shows

surface dewpoints perhaps reaching near 50 deg F near the OH-WV-PA

border region towards 00z.  Cold 500-mb temperatures and diurnal

heating will act to partially compensate for modest moisture and

contribute to weak buoyancy.  Isolated to widely scattered

low-topped thunderstorms will probably develop along a

southeastward-moving cold front during the evening. Elongated

hodographs support updraft organization but the overall limited

moisture will act to constrain otherwise greater storm coverage. 

Marginally severe hail and perhaps a couple of damaging gusts are

the primary hazards with the stronger storms.



$$