ACUS01 KWNS 200602

SWODY1

SPC AC 200600



Day 1 Convective Outlook  

NWS Storm Prediction Center Norman OK

0100 AM CDT Thu Aug 20 2026



Valid 201200Z - 211200Z



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

THE MID ATLANTIC...THE MIDWEST AND CENTRAL PLAINS....



...SUMMARY...

Scattered severe storms are possible today and tonight across parts

of the Mid Atlantic, posing a risk for damaging wind gusts. Large

hail and isolated wind damage will be possible with severe storms

from Nebraska into northwest Wisconsin.



...Mid Atlantic and central Appalachians...

A shortwave trough embedded within broader northwesterly flow aloft

is forecast to move eastward from the OH valley into the Mid

Atlantic through today. Embedded within a broader upper trough over

the eastern Great Lakes, this shortwave perturbation will serve as a

focus for convective development across the Mid Atlantic and central

Appalachians this afternoon. As ascent overspreads the area, a warm

front is forecast to lift northward across southern PA, northern MD

into NJ and southern NY.



South of the front, a very moist air mass (dewpoints in the 70s F)

will lift northward. Despite poor low and mid-level lapse rates,

moderate buoyancy is expected south of the front and ahead of a

trailing lee trough into southern VA. Ongoing storms from a remnant

morning cluster may reintensify as they cross the Appalachians late

morning and early afternoon. Additional, possibly discrete,

development may occur east of the Blue Ridge and across the higher

terrain of southern PA and northern MD near the front by late

morning. 40-50 kt of deep-layer shear ahead of the front is forecast

to support a mix of supercells and line segments. Damaging winds and

isolated severe gusts appear probable. Enlarged low-level hodographs

near the front may also support a couple of tornadoes and marginally

severe hail with any more robust QLCS segments or supercells.



...Central Plains...

Strong northwesterly flow aloft will overspread a cold front moving

southward from the western Great Lakes into the central Plains.

Ahead of the front, warm temperatures and dewpoints in the mid to

upper 60s F will support moderate to large buoyancy by mid

afternoon. A shortwave impulse within the broader trough should

overspread the destabilizing air mass and aide in convective

development along the front across MN and SD, and farther south near

the front and surface trough intersection in central NE.



Forecast soundings show supercell wind profiles, with

elongated/straight hodographs aloft. Isolated to widely scattered

storms will develop by late afternoon/early evening, posing a risk

for large hail, severe wind gusts and perhaps a tornado. Some

significant hail (greater than 2 inch diameter) is possible across

the southern risk area given steeper mid-level lapse rates/cool

temperatures aloft and somewhat deeper low-level moisture. Some risk

for isolated damaging gusts may persist into the early overnight

across southern NE and northern KS if clustering can occur.



...Southeast...

South of the primary upper wave over parts of the Western Carolinas

and TN Valley, a surface trough in the lee of the Appalachians may

focus convective development during the afternoon. A few stronger

clusters with damaging gusts are possible, though weaker flow aloft

suggests more limited storm organization.



Additional scattered thunderstorms are expected again this afternoon

within a seasonably hot and humid air mass across the southeast and

lower MS Valley. Convective coverage is likely to focus along a

weakening cold front sagging southward across parts of AR/LA and

western MS and near a weak MCV across the central Gulf Coast. With

PWATs upwards of 2 inches, some potential for wet microbursts are

possible with the stronger storm clusters through early evening.



...AZ...

Strong heating beneath a prominent upper ridge will support another

round of scattered thunderstorms this afternoon and evening.

Seasonably rich monsoon moisture (dewpoints in the upper 50s to 60s

F) will support moderate destabilization amid modest easterly

mid-level flow. A few high-based clusters are possible, initially

over the higher terrain, before expanding west and south into the

lower elevations. This could support a few severe gusts given steep

lapse rates.



..Lyons/Thornton.. 08/20/2026



$$