Quantitative Precipitation Forecast
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FOUS30 KWBC 251443
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1042 AM EDT MON MAY 25 2015

...VALID 15Z MON MAY 25 2015 - 12Z TUE MAY 26 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 SE UTA 10 N JAN 20 E MCB 25 NNW ASD 30 N HSA 35 SSE MEI
40 NW GZH 10 NW PNS 30 SSE KVOA 20 WSW KIPN 15 SW KMYT
25 ESE SRN 10 N KCRH 15 E KBQX 15 SE NGP ALI 35 NE COT 25 NW UVA
10 S JCT 25 W 6R9 20 S 7F9 15 N DYS 35 S F05 10 NE TQH
10 WSW UNO 25 E POF 35 E DYR 45 SE UTA.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
50 N RBO 20 SE SSF 25 NW HYI 10 E ACT 10 SE OSA 25 SW PBF
20 SSE GLH 20 WNW HEZ 7R3 15 NW KVBS 15 SSE PSX 50 N RBO.


1500 UTC UPDATE

CHANGES TO THE PREVIOUS DAY 1 EXCESSIVE RAINFALL POTENTIAL OUTLOOK
WERE TO EXPAND THE MODERATE RISK AREA BACK TO THE NORTH AND
NORTHWEST ACROSS NORTHEAST TEXAS INTO FAR SOUTHEAST OK AND
SOUTHWEST AR.  THIS WAS FOR CURRENT RADAR TRENDS THAT DO SHOW
ORGANIZED CONVECTION FORMING AHEAD OF THE WELL DEFINED VORT
FORECAST TO LIFT NORTHEASTWARD FROM WEST TX INTO CENTRAL OK
MONDAY---AND FOR THE IN SITU LOWER FFG VALUES ACROSS THESE AREAS.
AS MENTIONED IN THE PREVIOUS DISCUSSION---THERE ARE DIFFERENCES IN
THE CURRENT MODELS WITH RESPECT TO WHETHER THERE WILL BE ONE---OR
TWO PRECIPITATION MAXIMUM OVER THE SOUTHERN PLAINS.  THE HI RES
ARW AND NSSL WRF---WHICH WERE EMPHASIZING MORE THE SOUTHERN
MAXIMA---DO NOT APPEAR TO BE HANDLING THE CURRENT CONVECTION
MOVING OUT OF SOUTHWEST TO WEST TX.  THE CMC GEM---NAM CONEST DO
SEEM TO HANDLE THE CURRENT NORTHERN MAX WELL---GIVING MORE
CONFIDENCE THAT THERE MAY BE HEAVIER TOTALS IN THE NORTHERN MAX
AND A GREATER RISK OF PRECIP TOTALS EXCEEDING FFG VALUES.  THIS
DOES NOT PRECLUDE THAT A SOUTHERN MAX WILL DEVELOP---WHICH DOES
HAVE SUPPORT IN THE HI RES NMMB AND MANY OF THE HI RES ENSEMBLE
MEANS AND THE HI RES ARW AND NSSL WRF.

OTHER CHANGES TO THE PREVIOUS OUTLOOK WERE TO EXPAND THE EASTERN
EDGE OF THE SLIGHT RISK AREA INTO MOST OF EASTERN MS AND WESTERN
AL. SLOW MOVING AREAS OF CONVECTION OR CONVECTION TRAINING IN A
GENERAL SOUTH TO NORTHERLY DIRECTION MAY PRODUCE ISOLATED RUNOFF
ISSUES DESPITE RELATIVELY HIGH FFG VALUES.

ORAVEC



...SOUTHERN PLAINS EAST INTO THE LOWER MS VALLEY AND SOUTH TOWARD
THE WESTERN AND CENTRAL GULF COAST...

THE NEXT UPPER LEVEL JET STREAK AND ASSOCIATED SHORTWAVE ROUNDING
THE BASE OF THE BROAD TROUGH IS CURRENTLY DIVING ESE TOWARD THE TX
BIG BEND. IN RESPONSE TO THE APPROACHING WAVE...LOW-MID LEVEL
WARM/MOISTURE ADVECTION DEVELOPS IN WEST TEXAS AND INCREASES
HEADING INTO CENTRAL TEXAS THIS AFTERNOON.  RAINFALL AMOUNTS AND
COVERAGE INCREASE AS THE AFTERNOON PROGRESSES...WITH AN AREA OF
MODERATE TO HEAVY RAIN EXPECTED TO DEVELOP.

THE MODEL GUIDANCE IS SPLIT IN TERMS OF WHERE THE AXIS OF HEAVIEST
RAIN WILL FALL. THE GLOBAL GUIDANCE CONTINUES TO BE FARTHER NORTH
ACROSS THE ARKLATEX NORTHEAST TOWARD THE THE MO/AR BORDER. MUCH OF
THE MESOSCALE GUIDANCE IS FARTHER SOUTH TOWARD THE GULF COAST...IN
LIGHT OF THE INCREASING LLJ OVERNIGHT AND (THUS) MORE UPWIND
PROPAGATION (S-SW) TOWARD THE GULF COAST WHERE THE GREATER
DEEP-LAYER INSTABILITY WILL RESIDE (MODEL MUCAPES BECOME 2X AS
HIGH NEAR THE GULF COAST COMPARED TO AREAS FARTHER NORTH). PRIOR
TO THE UPTICK IN LOW-LEVEL FLOW (NOCTURNALLY-ENHANCED OVERNIGHT).
PER THE NSSL-WRF AND WRF-ARW SIMULATED REFLECTIVITY GUIDANCE...
CELL MOTION FARTHER NORTH (ARKLATEX NORTHWARD) WILL BE MORE
NORTHEAST OR DOWNWIND PROPAGATING...MORE IN LINE WITH THE MEAN
850-300FF MB FLOW...GIVEN THE NOT-AS-ROBUST LOW-LEVEL INFLOW.

THE MODELS DO SHOW ENHANCED QG FORCING OVER THE AFOREMENTIONED
NORTHERN AREA...I.E. ENHANCED UPPER DIVERGENCE AND ASSOCIATED
LOW-MID LEVEL FRONTOGENESIS WITHIN THE RRQ OF A DEVELOPING (ALBEIT
SUBTLE) UPPER LEVEL JET STREAK ACROSS THE MIDWEST. FOR THIS
REASON...COULD CERTAINLY SEE AREAL-AVERAGE AMOUNTS WITHIN THE
0.50-1.5+ INCH RANGE ALONG THE ARKLATEX NORTHEAST TOWARD THE MO/AR
BORDER...HOWEVER...GIVEN THE TRENDS (GROWING CONSENSUS) AMONG THE
MULTIPLE HIGH RESOLUTION MODELS...HAVE NOTED A BROADER HIGHER
MAXIMA (1.5-2.5+ INCHES) FROM EASTERN TX ALONG THE GULF COAST INTO
WESTERN LA.

BECAUSE OF THE SPREAD IN THE GUIDANCE...WPC WILL MAINTAIN A BROAD
"SLIGHT RISK" REGION FOR EXCESSIVE RAINFALL ACROSS EASTERN
PORTIONS OF THE SOUTHERN PLAINS INTO THE LOWER MS VALLEY FOR THE
NEW DAY 1 EXCESSIVE RAINFALL OUTLOOK (12Z MON - 12Z TUE).
HOWEVER...HAVE DROPPED THE NORTHERN EDGE OF THE MODERATE RISK AREA
A BIT SOUTH FROM THE PREVIOUS (DAY 2) OUTLOOK...AGAIN BASED ON THE
SIGNAL OF WHERE THE BULK OF THE HEAVIEST RAINFALL RATES AND CELL
TRAINING WILL OCCUR WITH THE ANTICIPATED MCS LATER THIS AFTERNOON
INTO EARLY TUE.

HURLEY
$$





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