Alabama Protected by the Cap Today

Outstanding mesoscale discussion by Matt Grantham at the NWS Birmingham.

He discusses how warming aloft, or a capping inversion, is limiting all deep convection east of the squall line, or QLCS.

Here it is represented on the morning balloon launch from the Shelby County Airport.

The cap is represented by the 8.8C rise in temperature (the red line).

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
917 AM CST FRI MAR 3 2023

…NEW MESOSCALE UPDATE…

.MESOSCALE UPDATE FOR THE ONGOING SEVERE WEATHER THREAT…
ISSUED AT 917 AM CST FRI MAR 3 2023

MESOSCALE UPDATE.

THE ATMOSPHERIC CONDITIONS WILL BE QUITE UNUSUAL TODAY AS A
POWERFUL SHORTWAVE MOVES FROM THE LOWER MISSISSIPPI VALLEY TO THE
OHIO VALLEY. EXTREMELY STRONG WIND FIELDS WILL ACCOMPANY THIS
SYSTEM THROUGHOUT THE COLUMN AS A SURFACE LOW DEEPENS TO AROUND
978 MB NEAR PADUCAH AT NOON TODAY. THE WARMTH AND QUALITY OF
MOISTURE ALREADY IN PLACE ACROSS ALABAMA WOULD NORMALLY POINT TO A
TORNADO OUTBREAK. HOWEVER, THERE IS ONE SIGNIFICANTLY NEGATIVE
INGREDIENT TODAY WHICH MAKES THIS SETUP SO UNIQUE, WARM ADVECTION
AT 600 MB. IT IS NOT OFTEN THAT HIGH SEVERE WEATHER PARAMETERS ARE
WASTED IN ALABAMA, ESPECIALLY IN THE PRESENCE OF HEIGHT AND
PRESSURE FALLS. HOWEVER, IT APPEARS THAT NEARLY ALL PRE-FRONTAL
DEVELOPMENT WILL BE RESTRICTED BY THIS WARM LAYER. HEALTHY
UPDRAFTS SHOULD BE CONFINED ALONG THE COLD FRONT WHERE A QLCS IS
CURRENTLY BEING OBSERVED IN EASTERN MISSISSIPPI. THE QLCS IS
QUICKLY APPROACHING THE AL/MS STATE LINE AND WILL CROSS INTO OUR
NORTHWESTERN COUNTIES BY 10 AM. AS THIS MOVES ACROSS OUR FORECAST
AREA, THE MAIN IMPACTS SHOULD BE ACROSS OUR NORTHERN TWO ROWS OF
COUNTIES, CLOSER IN PROXIMITY TO THE UPPER-LEVEL SUPPORT AND
SLIGHTLY COOLER MID-LEVEL TEMPERATURES. WITH STRONG WIND FIELDS IN
PLACE, THESE STORMS MAY BE RATHER EFFICIENT AT PRODUCING WIND
GUSTS OF 60-70 MPH. A COUPLE OF LINE-EMBEDDED TORNADOES ARE ALSO
POSSIBLE. FARTHER SOUTH, THE MID-LEVEL WARM LAYER WILL BECOME
INCREASINGLY PROHIBITIVE TO UPDRAFT DEVELOPMENT, SO MUCH SO, THAT
DEWPOINTS OF 70F WILL NOT BE SUFFICIENT FOR DEEP CONVECTION.

87/GRANTHAM

Category: Alabama's Weather, ALL POSTS, Severe Weather