Quantitative Precipitation Forecast
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934
FOUS30 KWBC 290051
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
850 PM EDT THU APR 28 2016

...VALID 01Z FRI APR 29 2016 - 12Z FRI APR 29 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 S SHV 20 ENE TRL 35 WNW GLE 20 SSE F05 45 SW F05 55 SSW CDS
35 SSE AMA 20 WNW AMA 10 SE DUX 25 NNE BGD 20 ENE HHF 30 SW JWG
15 E OUN 15 E RKR 10 NNE M89 15 NE ELD 30 S ELD 20 S SHV.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 E DPL 15 SSE HRJ 10 SW IGX 15 N HNZ 10 S FKN 20 SSE ECG
25 WNW HSE 10 NNE NKT 10 E DPL.


...SOUTHERN PLAINS...

A RISK OF EXCESSIVE RAINFALL REMAINS IN THE VICINITY OF THE WEST
TO EAST ORIENTED FRONTAL BOUNDARY THAT IS FORECAST TO DRIFT
NORTHWARD INTO THE THE RED RIVER VALLEY AND ARKLATEX TONIGHT. RICH
MOISTURE IS POISED TO MAKE A QUICK RETURN INTO THIS AREA AS HEIGHT
FALLS PULL OUT OF THE ROCKIES...AND 850 MB LOW LEVEL FLOW VEERS TO
SOUTHERLY WHILE ACCELERATING TO 25-40 KNOTS BY MORNING. AT 22Z WE
NUDGED OR EXPANDED THE RISK AREA NORTHWARD INTO MORE OF EASTERN OK
AND SOUTHWEST AR...GIVEN THE SIGNAL IN THE 12Z HI-RES GUIDANCE.
THE 22 AND 23Z HRRR MAINTAINED A SIGNAL FOR CONVECTION TO FORM
WITHIN THE SLIGHT RISK AREA...ALTHOUGH CONFIDENCE IN MEANINGFUL
COVERAGE IS LESS TOWARD THE DALLAS-FORT WORTH AREA...WITH MOST OF
THE MODEL GUIDANCE LEANING TOWARD SOUTHERN OKLAHOMA AS THE AXIS
FOR THIS ELEVATED CONVECTIVE EVENT. FORCING WILL BE DOMINATED BY
WARM ADVECTION...WHICH DOES TEND TO ALLOW FOR MORE OF A NORTHWARD
DRIFT. STORMS ARE LIKELY TO BE LOOSELY ORGANIZED FOR A SEVERAL
HOUR PERIOD. FOCUSED DEEP ASCENT AND DEEP COLD POOL FORMATION
HOLDS OFF UNTIL CLOSER TO 12Z AND BEYOND IN RECENT HRRR RUNS..

FARTHER WEST...A SEPARATE MAXIMUM OF RAINFALL IS EXPECTED OVER THE
EASTERN TEXAS PANHANDLE...WHERE STRONGER UPPER DIFLUENCE OVERLAPS
WITH THE INSTABILITY GRADIENT AT THE WESTERN END OF THE NORTHWARD
LIFTING SURFACE BOUNDARY. MODELS SUCH AS THE NSSL WRF AND GEM
REGIONAL FIRST SHOWED A PRONOUNCED MAXIMUM HERE...AND EVENING RUNS
OF THE HRRR HAVE JOINED IN...WITH STRONGLY BACKED NEAR-SURFACE
INFLOW AND INCREASINGLY DEEP MOISTURE. A FLASH FLOOD RISK MAY
BECOME EVIDENT...ESPECIALLY AT THE SOUTHERN FLANK OF WHAT COULD BE
ONE ORE MORE SMALL MESOSCALE SYSTEMS...GIVEN THE INCREASING DEEP
LAYER LIFT IN A REGION OF SUFFICIENT AND IMPROVING INSTABILITY.
THE RISK OF HEAVY RAIN IS LESS CERTAIN ACROSS PARTS OF WESTERN
NORTH TEXAS AND SOUTHWEST OKLAHOMA AROUND SPS-LAW...BUT SUPERCELLS
WERE PROPAGATING TOWARD THAT AREA AT 00Z...AND THE HEAVY RAIN
SIGNAL IN THE HRRR HAS INCREASED OVER SOUTHWEST OKLAHOMA.
RAINFALL IN THIS AREA IS SEVERAL INCHES ABOVE AVERAGE OVER THE
PAST TWO WEEKS...SETTING THE STAGE FOR INCREASED SURFACE RUNOFF.


...NORTHEAST NC...

STRONG BUT OUTFLOW DOMINANT CONVECTION WAS SCATTERED AROUND
SOUTHERN VA AND CENTRAL TO NORTHEAST NC THIS EVENING. CELLS WILL
CONTINUE TO ROLL THROUGH AN AREA THAT RECEIVED HEAVY RAINFALL
WITHIN THE PAST 24 HOURS. FLASH FLOOD GUIDANCE VALUES ARE
RELATIVELY LOWER...WITH 2 INCHES IN AN HOUR OR 2.5 INCHES IN 3
HOURS ESTIMATED TO CAUSE BANKFUL CONDITIONS. A FEW CELL MERGERS
AND GROWTH OF SMALL SCALE OUTFLOWS MAY LOCALLY BOOST RAINFALL
AMOUNTS ABOVE FFG...BUT GENERALLY THE DEEP WESTERLY FLOW IN PLACE
SHOULD ENSURE FORWARD PROGRESSION...AND WITH THE LOSS OF DAYTIME
HEATING...EXPECT A DECREASING TREND IN STORM INTENSITY LATE THIS
EVENING.


...WEST VIRGINIA...

WARM ADVECTION AND STRONG WESTERLY FLOW JUST NORTH OF THE UPPER
JET AXIS HAD SUPPORTED ORGANIZED THUNDERSTORMS INTO THE EARLY
EVENING HOURS. REGIONAL RADARS CONTINUED TO ESTIMATE LOCAL RAIN
RATES ABOVE ONE INCH PER HOUR BENEATH THE STRONGEST CELLS IN
SOUTHEAST OHIO AND NORTHERN WEST VIRGINIA. FARTHER
SOUTH...CONVECTION HAD BEGUN TO DISSIPATE WITH NOT ONLY THE LOSS
OF HEATING...BUT THE UPPER JET AXIS LIFTING NORTHWARD ONTO THE
COOL SIDE OF THE INSTABILITY GRADIENT. ANY REMAINING FLASH FLOOD
THREAT WILL AFFECT ONLY A SMALL AREA...AND THE RISK SHOULD SUBSIDE
BEYOND 03Z.

BURKE
$$





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