Quantitative Precipitation Forecast
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FOUS30 KWBC 311457
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1056 AM EDT TUE MAY 31 2016

...VALID 15Z TUE MAY 31 2016 - 12Z WED JUN 01 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 SE HBR 20 ESE OUN 25 N MLC 20 ESE AQR RBD HLR 30 NNW ALI
20 NE HBV 10 SE LRD 10 SE MMPG 30 WNW DRT 55 SW 6R6 40 W 6R6
25 E FST 10 SE MDD 45 SSW LBB 10 NNW CVS 20 NE CQC 20 NE SAF
15 NNE SKX 15 ENE ALS 35 ENE MYP 10 SE APA 25 SSE SPD 35 WNW CDS
20 SE HBR.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 E LNR CID 10 ESE OXV 10 SSW DSM 15 W CCY 10 ESE LVN
10 NNE PNM 10 SW HZX 20 NNW ASX 15 NNW AIG 20 SW PCZ 15 E LNR.


...WISCONSIN AND EASTERN MINNESOTA AND IOWA...

A NARROW INSTABILITY AXIS EXTENDED UP THROUGH EASTERN IOWA INTO
ADJACENT WI/MN THIS MORNING...AND SHOULD REMAIN IN PLACE WHILE
DAYTIME HEATING ACTS TO REMOVE INHIBITION AHEAD OF AN APPROACHING
UPPER LOW AND ASSOCIATED SURFACE WAVE. MOISTURE/INSTABILITY MAY
BECOME POOLED ALONG A QUASI-STATIONARY OR WARM FRONT STRETCHED
ACROSS EASTERN MN AND SOUTHWEST WI. THIS BOUNDARY MAY ALSO LEAD TO
ENHANCED CONVERGENCE / CONVECTIVE CELL REGENERATION AND/OR DEVIANT
MOTION LATER TODAY AS SURFACE-BASED THUNDERSTORMS DEVELOP. THIS
COULD ENHANCE THE POTENTIAL FOR LOCAL FLASH FLOODING...WITHIN A
REGIME OTHERWISE CHARACTERIZED BY THE POTENTIAL FOR SSW TO NNE
TRAINING...AS 0-6 KM MEAN WINDS VARY LITTLE FROM THE PREDICTED
CORFIDI VECTORS FOR FORWARD PROPAGATING SYSTEMS. BOTH GLOBAL MODEL
RUNS AND LATEST HI RES MODELS POINT TOWARD AREA FROM ERN IA INTO
THE WRN HALF OF WI AND FAR EASTERN MN FOR THE HEAVIER RAIN
AMOUNTS. HI RES GUIDANCE INDICATES SOME SHORT TERM LOCAL 2+ INCH
RAINS COULD OCCUR...WHICH WOULD APPROACH OR LOCALLY EXCEED SOME OF
THE LOWER EXISTING FLASH FLOOD GUIDANCE VALUES.


..OKLAHOMA/TEXAS/SE CO/NE NM...

HIGH CONFIDENCE...AT LEAST IN THE SENSE OF MODEL AGREEMENT...AS TO
WIDESPREAD CONVECTIVE OVERTURNING THAT WILL TAKE PLACE WITHIN A
REGION OF STRONG INSTABILITY...SEASONABLY RICH MOISTURE...AND WEAK
TO MODERATE DEEP LAYER FORCING OVER THE SOUTHERN PLAINS AND
UPSLOPE AREAS OF CO/MN. SPECIFIC EVOLUTION OF CONVECTION IN THIS
AREA IS LESS CERTAIN. FOR THIS OUTLOOK WE TRIMMED AWAY AT NORTHERN
AND CENTRAL OKLAHOMA...WHERE THE RAP/HRRR SUGGEST RAIN-COOLED
OUTFLOW AND NORTHERLY WINDS WERE HERE TO STAY. WE EXPANDED THE
SLIGHT RISK OVER THE UPSLOPE AREAS...AND CONNECTED THIS WITH THE
BROAD SLIGHT RISK AREA OVER TEXAS/SOUTHERN OKLAHOMA. LARGE SCALE
SYNOPTIC FORCING WOULD SEEM TO FAVOR THE NEXT ROUND OF SURFACE
BASED CONVECTION FORMING ALONG THE HIGH PLAINS NM/TX THIS
AFTERNOON AND PROPAGATING TOWARD A CORRIDOR OF ENHANCED 850 MB
SOUTHERLY FLOW ACROSS THE PERMIAN BASIN AND WESTERN END OF THE
EDWARDS PLATEAU. IN FACT...THE MULTI-CYCLE TRENDS HAVE BEEN FOR
QPF TO COME SOUTHWARD...MORE OF IT EXITING OKLAHOMA...WITH
INCREASED CONFIDENCE OF MODERATE TO HEAVY RAIN OF WESTERN/CENTRAL
TEXAS. STILL SOME QUESTION AS TO HOW THIS EVOLVES ACROSS CENTRAL
AND WESTERN NORTH TEXAS...HOWEVER...WITH MORE RECENT HRRR RUNS
SEEMING TO SUGGEST THAT WARM ADVECTION RELATED TO A LOW AMPLITUDE
LEAD WAVE THIS MORNING TAKES ROOT AND STARTS TO PROPAGATE DOWN
INTO CENTRAL TX THIS AFTERNOON. REGIONAL SOUNDINGS SHOW MID LEVEL
TEMPS JUST WARM ENOUGH AND LOW LEVELS JUST DRY ENOUGH...THAT
SUBSTANTIAL SURFACE-BASED CONVECTION MAY HOLD OFF UNTIL
TEMPERATURES REACH THE UPPER 80S. WE SUSPECT THE MODELS MAY BE A
LITTLE FAST TO EVOLVE THINGS...BUT THAT EVENTUALLY THE REGION
WITHIN THE SLIGHT RISK WILL SEE CLUSTERS OF ORGANIZED CONVECTION
AND LOCALLY HEAVY RAIN...WHICH WILL CARRY A RISK OF FLASH FLOODING
GIVEN THE LONG TERM WET ANTECEDENT CONDITIONS ACROSS THIS REGION.

00Z HI RES GUIDANCE SUGGESTS POTNL FOR LOCALIZED 3 HR RAINFALL
AMOUNTS IN EXCESS OF 3 TO 4 INCHES ACROSS TX/OK. MOISTURE IS NOT
AS GREAT ACROSS NM/CO...BUT DEWPOINTS REACHING THE MIDDLE 40S AT
HIGH ELEVATION MAY BE SUFFICIENT FOR A FLASH FLOOD THREAT GIVEN
SLOW CELL MOTIONS.


...MIDDLE PORTION OF THE EASTERN SEABOARD...

SLOW MOVING POST-TROPICAL BONNIE WAS LOCATED NEAR THE SC COAST
THIS MRNG AND WILL CONTINUE TO SLOWLY DRIFT NEWD THIS PD. THE CIRC
REMAINS WEAK BUT SUFFICIENT MSTR REMAINS AROUND THE CIRCULATION TO
SUPPORT BANDS OF MDT PCPN...MAJORITY OF WHICH HAVE REMAINED OVER
THE OPEN WATERS DURING MON NIGHT...BUT WITH ANY BREAKS IN OVERCAST
TO INCREASE INSTABILITIES...COULD SEE SOME INCREASE INLAND AS WELL
THIS AFTN AND TUES NIGHT. MANUAL QPF TOOK A CONSENSUS APCH WITH
.50 TO 1 INCH AREAL AVG AMOUNTS THRU ERN NC INTO THE UPR SC COAST
BUT ISOLD NARROW AREAS OF HEAVIER RAINS WILL BE PSBL...LEADING TO
AN ISOLD THREAT OF RUNOFF PROBLEMS GIVEN THE RECENT HEAVIER RAINS
ACRS THIS REGION.

BURKE/SULLIVAN
$$




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