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ACUS01 KWNS 141954

SWODY1

SPC AC 141952



Day 1 Convective Outlook  

NWS Storm Prediction Center Norman OK

0252 PM CDT Sun Apr 14 2024



Valid 142000Z - 151200Z



...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EASTERN

OHIO EAST-NORTHEASTWARD ACROSS PENNSYLVANIA...



...SUMMARY...

Severe thunderstorms are expected to develop late this afternoon in

a narrow corridor across the upper Ohio Valley into Pennsylvania and

vicinity. Damaging winds should be the main threat. Severe hail and

perhaps a couple of tornadoes also appear possible as this activity

spreads southeastward into this evening.



...Discussion...

Aside from minor line tweaks in the northern Ohio area, the

severe-weather risk areas remain unchanged, with prior forecast

reasoning -- highlighting development of strong to severe storms

this afternoon -- still valid.



For additional short-term forecast information in this region,

please refer to SWOMCD #435.



Elsewhere, the portion of the thunder area across Nevada is being

removed in this update.



..Goss.. 04/14/2024



.PREV DISCUSSION... /ISSUED 1129 AM CDT Sun Apr 14 2024/



...Ohio Valley into the Mid-Atlantic and Northeast...

Surface analysis late this morning shows the northeastern rim of 50s

dewpoints over northern KY/southwest OH being quickly advected

east-northeastward on a 40-kt west-southwesterly LLJ.  The Upper OH

Valley is located immediately downstream of a mid-level vorticity

maximum over Lake Michigan.  This disturbance will continue to move

into the base of the larger-scale eastern Canada/Northeast U.S.

mid-level trough.  An accompanying weak low will migrate eastward

from the Great Lakes across NY, while a weak cold front extends to

the west-southwest and is forecast to push east-southeast across the

Lower Great Lakes before weakening and becoming draped across the

Upper OH Valley late. 



Continued low-level moist advection will likely result in upper 40s

to low 50s surface dewpoints within a narrow corridor along

and south of a cold front from OH into PA and southern NY.  Steep

700-500 mb lapse rates due in part to cool mid levels (i.e., -18 deg

C at 500 mb) and heating will yield 500-1250 J/kg MLCAPE by mid-late

afternoon.  Surface-based thunderstorm initiation across this region

will likely be delayed until 20-21Z or later, as lingering MLCIN and

a cap gradually erodes. Initial development should be focused along

the front across parts of eastern OH into western/central PA, with

additional development eventually occurring into eastern PA and

parts of southern NY.  Given strong deep-layer shear and favorable

lapse rates, large hail may occur with the more robust cores

initially. Some threat for a couple of tornadoes may also exist with

quasi-discrete supercells early in the thunderstorm life cycle, as

sufficient low-level shear will be present for updraft rotation. 

But, with the surface front aligned mostly parallel to the enhanced

westerly low/mid-level flow, upscale growth into small bowing

clusters will likely occur as additional storms develop and cold

pools merge as the band of storms moves southeastward.  Scattered

damaging winds will then likely become the main threat with these

clusters through the early evening.  As instability wanes after

sunset, the wind threat will gradually decrease with

southward/eastward extent.



$$