799
ACUS02 KWNS 180525
SWODY2
SPC AC 180524

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1224 AM CDT Tue Jun 18 2024

Valid 191200Z - 201200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
THE SOUTHERN HIGH PLAINS...FROM PARTS OF IOWA INTO SOUTHERN
WISCONSIN...AND OVER FAR SOUTHERN TEXAS...

...SUMMARY...
Locally strong gusts may occur with storms over the southern High
Plains, and from parts of Iowa into southern Wisconsin. A brief
tornado cannot be ruled out over far southern Texas late Wednesday
and Wednesday night in association with Potential Tropical Cyclone
1.

...Synopsis...
The tail end of an upper trough will sweep across the northern
Plains and upper MS Valley during the day, with primary speed max
well into Ontario. Meanwhile, a strong upper ridge will extend from
the OH Valley into the Northeast, with rising heights and subsidence
developing over the Plains and south of the departing wave.

At the surface, a cold front will decelerate into WI, becoming
stationary during the evening westward into KS and toward northeast
NM. While a moist air mass will exist ahead of this front, warming
temperatures aloft and weakening lift will minimize severe potential
across those areas. However, easterly upslope flow may result in a
few strong storms into NM.

Farther south, a very moist air mass will push west across the
western Gulf of Mexico with upper 70s F dewpoints across southern
TX. Overall wind fields are likely to increase as Potential Tropical
Cyclone 1 develops, and possibly becomes a TS per NHC guidance.

...From southern WI to northeast NM...
Areas of thunderstorms are likely to be ongoing Wednesday morning
over parts of the central Plains, potentially producing strong
outflow winds. This convection is expected to weaken during the day,
with a rejuvenation along portions of the boundary during the
afternoon.

The most likely areas for isolated severe gusts appear to be over
the IA to WI/IL portion of the boundary in closer proximity to the
exiting upper wave, and in the upslope region over eastern NM. In
both areas, neither shear nor instability will be particularly
strong, but the front should provide a focus for development in a
marginally unstable environment. In addition to gusty winds, cells
over northeast NM into the OK/TX Panhandles may produce marginally
severe hail as veering winds with height favor cellular storm mode.

...Far southern TX...
Substantial convection with the potential tropical cyclone will move
westward from the Gulf of Mexico and into southern TX, providing
heavy rainfall and increasing winds. Official NHC guidance brings
the system to tropical storm strength prior to landfall over Mexico
early Thursday morning, which will maintain moist easterly winds
across TX.

Forecast soundings from various models depict upper 70s F dewpoints
will favor sufficient SBCAPE for a few strong storms given 30-50 kt
winds through the lowest few km AGL, veering with height. The
combination of a very moist air mass with potentially strong
low-level shear may favor a minimal tornado risk over the region,
and low tornado probabilities have been introduced.

..Jewell.. 06/18/2024

$$