MESOSCALE PRECIPITATION DISCUSSION 0437
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
144 PM EDT MON AUG 10 2015
 
AREAS AFFECTED...NORTHEAST NM & SOUTHEAST CO 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 101743Z - 102343Z
 
SUMMARY...AFTERNOON CONVECTION IS EXPECTED TO EXPAND IN COVERAGE
AND INTENSITY DUE TO BUILDING INSTABILITY.  FLASH FLOODING IS
POSSIBLE.

DISCUSSION...THE BEGINNING OF UPSLOPE FLOW BEHIND A COMPOSITE
SURFACE BOUNDARY, BEING REINFORCED BY OUTFLOW FROM OVERNIGHT
CONVECTION IN KS, HAS LED TO INCREASING MOISTURE INTO THE REGION
PER TRENDS IN GPS PRECIPITABLE WATER VALUES (PWS).  PWS ARE CLOSE
TO 1.25", WHICH ARE CLOSE TO TWO STANDARD DEVIATIONS ABOVE THE
NORM FOR MID-AUGUST.  CIN ACROSS THE REGION HAS NEARLY ERODED PER
SPC MESOANALYSES, WITH MLCAPES CURRENTLY AROUND 1000 J/KG. 
NORTHEAST FLOW OF 10-15 KTS EXISTS AT 850 HPA/NEAR THE SURFACE,
WHILE A CONVERGENCE ZONE AT 700 HPA IS SEEN IN RAP GUIDANCE ACROSS
NORTHEAST NM.  A FEW SHOWERS AND THUNDERSTORMS HAVE BEGUN TO
DEVELOP BETWEEN THE VARIOUS SURFACE BOUNDARIES WITH NEW LIGHTNING
ACTIVITY NOTED, PARTICULARLY NEAR THE TERRAIN ACROSS NORTHEAST NM
AND SOUTHERNMOST CO.

THE EXPECTATION IS THAT CONVECTION SHOULD INCREASE IN COVERAGE AND
INTENSITY AS UPSLOPE FLOW SLOWLY INCREASES IN MAGNITUDE WITH
SURFACE WINDS TURNING MORE SOUTHEASTERLY WITH TIME.  CONVECTIVE
PROPAGATION IS EXPECTED TO BECOME EAST-NORTHEAST AT ~10 KTS. 
OVERALL, THE CELL MOTION COMBINED WITH THE LOW-LEVEL FLOW SHOULD
YIELD CLOSE TO 25 KT CLOUD BASE INFLOW.  AS LOW-LEVEL INFLOW
INCREASES, THE MEAN 850-400 WIND WILL BE EASILY EXCEEDED AS ITS
MAGNITUDE IS ONLY 5 KTS, WHICH COULD LEAD TO PRECIPITATION
EFFICIENCY.  THE MESOSCALE QPF GUIDANCE SUGGESTS LOCAL AMOUNTS IN
THE 2-4" RANGE, WHICH COULD FALL QUICKLY.  HOURLY RAIN RATES OF
1.5" ARE POSSIBLE GIVEN THE AVAILABLE MOISTURE, WHICH COULD OCCUR
WHERE CELLS MERGE AND/OR TRAIN.  THE 06Z SSEO NEIGHBORHOOD
PROBABILITIES SUGGEST THE RAMPING UP OF CONVECTIVE ACTIVITY
PARTICULARLY AFTER 21Z, WHEN THERE IS AN EXPANDING AREA OF A 50%+
CHANCE OF EXCEEDING THE THREE HOUR FLASH FLOOD GUIDANCE VALUES
WITHIN THIS REGION.  AS CONVECTIVE COVERAGE COULD BE SPOTTY WITHIN
THIS AREA, USED THE FLASH FLOODING POSSIBLE CATEGORY.

ROTH

ATTN...WFO...ABQ...PUB...

ATTN...RFC...ABRFC...WGRFC...

LAT...LON   37720500 37500337 36470312 35760404 35300586 
            36520591 37240582