MESOSCALE PRECIPITATION DISCUSSION 0949
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
115 PM EST FRI DEC 22 2017

AREAS AFFECTED...SOUTHERN AR...NORTHERN MS...SOUTHWEST TN

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 221815Z - 222315Z

SUMMARY...RELATIVE LULL IN DEEP CONVECTION SHOULD REDUCE OVERALL
THREAT AND COVERAGE. HOWEVER MODERATE SYNOPTIC FORCING/MOISTURE
AND WET SOILS MAY LEAD TO ISOLATED FF RISK THROUGH THIS EVENING
WITH SOME SCATTERED ACTIVITY.

DISCUSSION...INITIAL ROUND OF CONVECTIVE RAINS CONTINUES ACROSS
FAR N MS...EXTENDING BACK TOWARD PBF ALONG OUTFLOW WITH TRAINING
ELEMENTS.  HOWEVER...SHORTWAVE AND JET MAX ASSOCIATED WITH THAT
ACTIVITY HAS PROGRESSED INTO CENTRAL W TN LEAVING S AR IN A
SHORT-TERM LULL WITH REDUCED INFLOW/MST CONVERGENCE.  WEAK FLATTER
WAVES CAN BE SEEN IN RADAR/GOES-WV LOOP OVER SE OK AND NE TX
LIFTING NORTHEAST.  THE WEAK DPVA IS SUPPORTING A SFC LOW NEAR
OK/AR/TX INTERSECTION...BUT ALSO SUPPORTING LOW LEVEL CAA TO PRESS
THE COLD FRONT SOUTH THROUGH FWD CWA TOWARD HOUSTON.

GOES-16 VISIBLE LOOP ALSO DEPICTS CLEARING AHEAD OF THE FRONT IN
NE TX/NW LA AND S AR BEHIND THE DYING OUTFLOW BOUNDARY...AS SUCH
INSTABILITY IS ONCE AGAIN REGAINING AND WITH UPPER 60S AT 70/71
TDS...TEMPS SHOULD INCREASE AND SFC SOUTHERLY FLOW WILL INCREASE. 
MODERATE LOW LEVEL VEERING ACROSS NE TX BECOMES HIGHLY CONFLUENT
NEAR TXK KEEPING THE MAIN INSTABILITY/MOISTURE AXIS ALIGNED FROM
TXK TO PBF TOWARD MEM/UTA. THE WEAK S/W IN NE TX WILL AMPLY AND
WITH RECHARGING CAPES TO 1000-1500 J/KG THERE IS A GOOD CHANCE THE
ELEVATED CONVECTION ACROSS NE TX WILL SHIFT EAST AND ROOT MORE
INTO THE BOUNDARY LAYER AND POTENTIALLY EXPANDING.  STILL THE WAVE
IS WEAK ENOUGH TO NOT HAVE STRONG ENOUGH FORCING FOR EXPANSIVE
CONVECTION BUT ANY ISOLATED CELL TO TRACK THROUGH NEVADA TO
PHILLIPS COUNTY WILL ONLY RESTART FLASH FLOODING CONDITIONS.

THIS SCENARIO IS PRESENTED THROUGHOUT MUCH OF THE HI-RES GUIDANCE
PROVIDING FAIRLY HIGH CONFIDENCE BUT IS BEST VERIFYING BY THE 12Z
ARW AND RECENT HRRR.  AS SUCH SUGGESTIVE OF AN ADDITIONAL 1-2" IS
EXPECTED THROUGH 00Z ACROSS S AR WITH 2-3" ISOLATED 4" ACROSS SE
TN/N MS GIVEN THE CURRENT ONGOING ROUND AND SCATTERED BUT
OCCASIONALLY INTENSE ONES THROUGH THE LATE AFTERNOON/EVENING
HOURS.  GIVEN PRECISE UNCERTAINTY THAT THE CONVECTION WILL ALIGN
WITH THE FLOODED AREAS...FLASH FLOODING IS CONSIDERED POSSIBLE
ELSEWHERE DUE TO LOWER MAGNITUDES/SHORTER DURATION/RATES.    

GALLINA

ATTN...WFO...JAN...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...SERFC...

LAT...LON   36048814 35018821 34448829 33848915 33119273
            32749425 33559434 33969392 34199374 35039193
            35838932