Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 250809
QPFERD

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

...VALID 12Z 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 SSE OLV 30 N MCB 25 ESE PQL 10 WSW KVOA 25 SW KIKT KMYT
25 N GSM 15 NNW KCRH KBQX 10 WSW NGP 30 NNE COT 25 WNW UVA ECU
10 ESE JCT 20 NE 6R9 10 SSE SEP 25 WSW 1F0 15 ENE MKO 10 N BPK
25 E POF 35 E DYR 45 SSE OLV.

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.


...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
0.50-1.0+ 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 HIGHER MAXIMA
(1.5-3.0+ 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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