Pretty strongly worded AFD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
206 PM CDT FRI MAY 22 2020
.SHORT TERM... /NEW/
/THIS AFTERNOON THROUGH SATURDAY/
THE OVERNIGHT PLAINS CONVECTION MADE A RUN AT NORTH TEXAS, BUT
ALL THAT REMAINS IS A STATIONARY OUTFLOW BOUNDARY ALONG A LINE
FROM GRAHAM TO DENTON TO BONHAM. VISIBLE SATELLITE LOOP SHOWS
GRAVITY WAVES CONTINUE TO PROPAGATE SOUTHWARD THROUGH THE CUMULUS
FIELD INTO CENTRAL TEXAS, WHICH IS A SIGN OF A VERY STRONG
CAPPING INVERSION. THIS INVERSION IS VERIFIED ON RECENT AMDAR
SOUNDINGS, AND WE'LL BE SENDING UP A BALLOON WITHIN AN HOUR OR SO
TO SAMPLE THE EVOLUTION OF THE THERMODYNAMIC AND MOISTURE PROFILE.
OBVIOUSLY THE OUTFLOW BOUNDARY WILL BE AN IMPORTANT MESOSCALE
FEATURE THAT WILL IMPACT NOT ONLY CONVECTIVE INITIATION, BUT ALSO
STORM MODE AND HAZARDS. THE BACKING OF WINDS BEHIND THE BOUNDARY
HAS SERVED TO INCREASE DEEP LAYER SHEAR VALUES NOTABLY, RESULTING
IN AN ENVIRONMENT NOW SUPPORTIVE OF PROLONGED SUPERCELL STRUCTURES
NEAR AND NORTH OF THE BOUNDARY. MEANWHILE INSOLATION HAS BEEN
EXCELLENT ACROSS THE REGION AND LOW LEVEL INSTABILITY CONTINUES TO
INCREASE WITH MLCAPE LIKELY TO EXCEED 3500 J/KG THIS AFTERNOON.
GIVEN THE HIGH INSTABILITY AND PREDICTION OF SLOW EASTWARD RIGHT
MOVING SUPERCELLS, IT IS LIKELY THAT ACTUAL SUPERCELL MOTIONS WILL
BE EVEN MORE RIGHTWARD OR DUE SOUTH. THIS IS IMPORTANT AS IT WILL
IMPACT THE STORM COVERAGE AND EVOLUTION. IN THE LAST FEW HOURS
WE'VE SEEN THE HRRR TREND TOWARD MORE SUPERCELLULAR COVERAGE WHICH
IS INHERENTLY MORE SCATTERED AND THEREFORE SUGGESTS LESS STORM
COVERAGE THAN A MULTICELL CLUSTER OR LINE WOULD HAVE PRODUCED.
THIS MORE SUPERCELLULAR STORM MODE IS ALSO VERIFIED BY THE WOFS
WHICH IS HIGHLIGHTING THE SUPERCELL THREAT PRIMARILY OVER THE
NORTHWESTERN ZONES OVER THE NEXT 4 HOURS WHERE WE HAVE ALREADY
SEEN A FEW FAILED ATTEMPTS AT INITIATION.
SINCE MATURE STORM MOTION MAY TEND TO TAKE IT SOUTHWARD, IT MAY
BE A WHILE BEFORE STORMS CAN INITIATE FARTHER EAST (EAST OF
I-35/I-35E AND NORTH OF I-30) WHERE STORM COVERAGE IS MORE IN
QUESTION. SPC HAS ISSUED A SEVERE THUNDERSTORM WATCH FOR OUR
NORTHWESTERN COUNTIES THROUGH 8 PM. WE'VE AGREED TO WATCH HOW
TRENDS EVOLVE BEFORE GOING TOO FAR EAST WITH A WATCH. LIKEWISE
WE'RE CONCERNED THAT THE ENVIRONMENT MAY BECOME MORE FAVORABLE FOR
TORNADOES AROUND SUNSET, SO THIS WATCH EXPIRING AT 8 PM ALLOWS AN
ASSESSMENT OF THOSE TRENDS THIS EVENING. FOR NOW THE PRIMARY
THREAT LOOKS LIKE VERY LARGE HAIL - POSSIBLY UP TO BASEBALL SIZE -
AS WE ANTICIPATE THAT WE'LL HAVE MORE SUSTAINED SUPERCELL
STRUCTURES THAN WE WERE EARLIER. GIVEN THE ALREADY SLOW MOTION OF
SUPERCELLS, WOULD NOT BE SURPRISED TO SEE SOME NEARLY STATIONARY
OR STALLED CELLS EITHER WHICH COULD RESULT IN LOCALIZED MULTI-INCH
RAINS AND FLASH FLOODING.
BY THIS EVENING WE DO EXPECT MORE COVERAGE OF STORMS AND EVENTUALLY
ENOUGH OF A COLD POOL SHOULD DEVELOP TO HELP SEND CELLS
SOUTHEASTWARD EITHER AS A MULTICELL CLUSTER OR BROKEN LINE. THE
EVENING HOURS PROBABLY REPRESENT MOST OF THE DFW METROPLEX'S BEST
SHOT AT SEVERE WEATHER. THIS ACTIVITY SHOULD MOVE SOUTH OF I-20 BY
MIDNIGHT INTO CENTRAL TEXAS, BUT THE INTENSITY/COVERAGE SHOULD
DECREASE AS THE ENVIRONMENT BECOMES INCREASINGLY MORE STABLE.
THERE REMAINS A POSSIBILITY OF ELEVATED SCATTERED STORMS
DEVELOPING IN THE OVERNIGHT HOURS NORTH OF I-20, AS THIS IS
ADVERTISED BY A COUPLE OF THE MODELS. SO WE CAN'T SAY FOR SURE
THAT ONCE THE FIRST ROUND MOVES THROUGH THAT NORTHERN AREAS WILL
BE DONE WITH THE EVENT.
THE ATMOSPHERE SHOULD BE WORKED OVER FOR ADDITIONAL STORMS ON
SATURDAY AND HAVE KEPT POPS LOW BUT ADVERTISED LOTS OF CLOUD
COVER. HIGHS WILL BE IN THE 80S BUT IT SHOULD BE VERY MUGGY WITH
LIGHT TO MODERATE SOUTHERLY FLOW PREVAILING.
TR.92