Quantitative Precipitation Forecast
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FOUS30 KWBC 240335
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1135 PM EDT SAT MAY 23 2015

...VALID 0335Z SUN MAY 24 2015 - 12Z SUN MAY 24 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NNE MCI 25 SSW SZL 35 ESE FYV 25 ENE LBR 30 WSW PSN
10 NW BYY 20 N KMIU 30 ESE PIL 15 WSW MMMA 60 NE MMMY 55 SW MMNL
65 NE MMMV 45 S MMPG 15 SE MMPG 25 WSW UVA 15 SSE ECU 10 W JCT
30 NNW JCT 20 E SJT 40 NNW SJT 15 WSW SWW 25 N SWW 45 NE SNK
40 S CDS 15 SE CDS 30 NW LTS 20 W JWG 25 W END 25 ENE AVK
25 S HUT 20 SW MHK 30 SSW FNB 20 NNE MCI.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
50 NE DGW 25 SSW CDR 35 S AIA 30 SE SNY 30 NE AKO 25 NW AKO
25 NNE GXY LAR 25 ESE RWL 25 SSW PAT 10 SW TMH 50 NE DGW.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 N RBO 10 ENE HBV 15 SE MMNL 15 WSW MMNL 35 WNW MMNL
35 SE MMPG 25 N UVA 20 E JCT 40 NNE JCT 50 E SJT 45 S DYS
20 SSW DYS 30 NE SWW 65 NNE SWW 40 SSE CDS 25 WSW LTS 10 NE HBR
15 WSW GOK 20 E WLD 40 W CNU 25 S UKL 20 N CNU 20 ENE CNU
20 E PPF 25 SE CFV 15 S GCM 25 SSE OKM 15 WSW MLC 15 SW AQR
10 NW GYI AFW 15 WSW GDJ 05F 20 E AUS 40 NNW VCT 10 N RBO.

HIGH RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 SW ADH 35 ESE SPS 20 NW RPH 50 W RPH 60 SSW F05 40 SW F05
15 NNW F05 20 E HBR 15 NNE CHK 20 NNW SNL 15 SSE CQB 20 N ADH
20 SW ADH.

HIGH RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 SSW SSF 30 NE LRD 10 NNE LRD 15 NW LRD 40 NNW LRD 35 S UVA
25 WSW ERV T82 20 E T82 10 N SAT 35 SSW SSF.



...HEAVY RAINFALL EVENT ACROSS MUCH OF THE SOUTHERN TO SOUTH
CENTRAL PLAINS...

CHANGES THIS ISSUANCE WERE TO TRIM OFF WESTERN PARTS OF THE
PREVIOUS AREA WHERE HEAVY RAIN HAS ENDED..BUT MORE IMPORTANTLY TO
ADD A "HIGH" RISK TO PARTS OF SOUTHERN OK/NORTHERN TX..WHERE SOME
VERY INTENSE/VERY HEAVY
RAIN/RAINFALL RATES ARE LIKELY FOR AT LEAST THE NEXT 3-6 HOURS.

IN THIS NEW "HIGH" RISK AREA..ORGANIZED CONVECTIVE CELLS MOVING
NORTHWARD THRU NORTHERN TX INTO SOUTHERN OK WILL MERGE WITH THE
QUASI-STATIONARY LINE STRETCHING FROM ABOUT OKC SOUTHWESTWARD TO
BETWEEN CDS AND F05..LIKELY RESULTING IN VERY INTENSE RAINFALL
RATES.  VERY HIGH MOISTURE..A MODERATELY STRONG LOW LEVEL JET AND
LARGE SCALE ASCENT ARE ALREADY A GIVEN THRU THE ENTIRE SOUTHERN
PLAINS REGION..AND LIFT WILL LIKELY BE ENHANCED WITHIN THE "HIGH
RISK" AREA BY A NORTHEASTWARD MOVING MESO-VORT NOW EAST-SOUTHEAST
OF LBB.  BETWEEN THE MERGING CELLS..VERY SLOW MOVEMENT TO THE MORE
ORGANIZED LINE..THE HIGH PWS AND IMPROVING LIFT..FELT CONFIDENT IN
THIS UPGRADE TO HIGH.  SOME OF THE HIRES GUIDANCE..INCLUDING THE
ECMWF AND A HRRR RUN FROM SEVERAL HOURS AGO..ARE HITTING THIS AREA
HARD THRU THE EVENING AND INTO THE LATER SATURDAY NIGHT HOURS.  A
RECENT HRRR RUN INDICATED A 7-8 INCH RAINFALL MAXIMA WITHIN THE
HIGH RISK AREA BETWEEN 23-05Z.  WOULD NOT DISCOUNT THIS
POSSIBILITY AND DO SEE THE THREAT FOR AT LEAST GREATER THAN 5 INCH
RAINS DURING THE REMAINDER OF THE NIGHT.


REMAINDER OF THE PREVIOUS DISCUSSION UNCHANGED...
I UPGRADED THE EXCESSIVE RAINFALL RISK TO HIGH OVER PARTS OF SOUTH
TEXAS BASED ON INCREASING AGREEMENT AMONG THE HIGH RESOLUTION
MODELS OF HEAVY RAIN THERE WITH FAVORABLE AVAILABLE INSTABILITY
AND ANOMALOUSLY HIGH AVAILABLE MOISTURE/HIGH FORECAST MOISTURE
FLUXES...AND ANOTHER RECENT ROUND OF SHOWERS/STORMS TO LOWER THE
RAINFALL NEEDED TO CAUSE FLOODING. MULTIPLE HIGH RESOLUTION MODELS
INCLUDING THE NAM CONEST...WRF-ARW...WRF-NMMB...NSSL-WRF BRING
HEAVIER RAINFALL AMOUNTS ACROSS SOUTH TEXAS AND HAVE BEEN JOINED
BY THE 10-11Z HIGH RES RAPID REFRESH RUNS.  THE HIGH RES MODELS
FORECAST THE HIGHEST TOTALS IN SOUTH TEXAS OF 3-6 INCHES...WITH
LOCALLY HIGHER TOTALS.

THE INITIAL CLUSTER OF SHOWERS AND STORMS MOVES OUT ACROSS OK THIS
AFTERNOON AND TONIGHT. THEN THERE IS EXPECTED TO BE A LARGE
SCALE...SLOW MOVING BAND OF HEAVY SHOWERS AND THUNDERSTORMS THIS
EVENING AND OVERNIGHT IN CENTRAL TO SOUTHERN TX. CONSIDERING THE
ANTECEDENT SATURATED SOILS AND LOW FFG ON BOTH SIDES OF THE RED
RIVER ACROSS SOUTHERN-CENTRAL OK AND NORTHERN TX AND ALSO IN
SOUTHERN TEXAS...THE POTENTIAL FOR ADDITIONAL FLASH FLOODING OVER
THESE AREAS WILL BE ENHANCED.

INCREASED S-N UPPER CONFLUENCE EAST OF THE UPPER TROUGH WILL
INDUCE AN ANOMALOUS 90-100 KT SOUTHERLY 250 MB JET STREAK ACROSS
THE SOUTHERN-CENTRAL HIGH PLAINS...ONE WHICH BY LATE IN THE PERIOD
WOULD PROVIDE AN ADDITIONAL BOOST TO THE ALREADY ROBUST UPPER
LEVEL DIVERGENCE AND DEEP-LAYER ASCENT WITHIN ITS RIGHT ENTRANCE
REGION ACROSS THE SOUTHERN PLAINS.

THE MESOSCALE GUIDANCE SUGGESTS MULTIPLE ROUNDS OF CLUSTERED
CONVECTION. THE STRENGTHENING LOW LEVEL INFLOW (45-50 KT SOUTHERLY
LLJ ~850 MB) AND ANOMALOUS 850-700 MB MOISTURE TRANSPORT FROM THE
WESTERN GULF WILL BOOST PW VALUES BETWEEN 1.75-2.00+ INCHES...OR
2-2.5 STANDARD DEVIATIONS ABOVE THE NORM PER THE SREF/GEFS
ENSEMBLES. MODERATE DEEP-LAYER INSTABILITY (MUCAPES 1000-2000
J/KG) WILL BE IN PLACE THIS EVENING AND OVERNIGHT ACROSS THE
SOUTHERN PLAINS...SO CELLS DEVELOPING IN THE REGION WILL HAVE
POTENTIAL TO PRODUCE RAINFALL RATES TO 2 INCHES PER HOUR.


...HIGH PLAINS OF NORTHEAST CO/WESTERN NEBRASKA/SOUTHEAST WY...

I EXPANDED THE SLIGHT RISK AREA SOUTH IN NORTHEAST CO AS THE FRI
NIGHT CLUSTER OF HEAVY SHOWERS/STORMS MAKE THE AREA MORE
VULNERABLE TO FLOODING TODAY AND TONIGHT...WITH THE MODELS
FORECASTING ADDITIONAL ROUND OF SHOWERS/POSSIBLE STORMS THIS
AFTERNOON AND EVENING.

AMPLIFYING UPPER TROUGH INCREASES THE UPPER DIFFLUENCE. THE
DEVELOPING S-N UPPER LEVEL JET STREAK ACROSS THE SOUTHERN-CENTRAL
HIGH PLAINS ON THE EASTERN EDGE OF THE TROUGH WILL ENHANCE THE
UPPER DIVERGENCE AND DEEP-LAYER ASCENT ACROSS THE OUTLOOK AREA IN
THE LEFT EXIT REGION. THE FAVORABLE DYNAMICAL PROFILE ALONG WITH
THE 20-30 KT SOUTHEASTERLY (UPSLOPE) LOW-LEVEL INFLOW...ANOMALOUS
MOISTURE FLUX/PW VALUES...AND AVAILABLE DEEP-LAYER INSTABILITY
(MUCAPES 500-1500 J/KG) WILL LEAD TO AREAS OF HEAVY TO POTENTIALLY
EXCESSIVE RAINFALL.  ADDITIONAL SHOWERS/STORMS ARE EXPECTED THIS
AFTERNOON AS 700 MB CONVERGENCE MAXIMA MOVE THROUGH THE AREA.
AREAL-AVERAGE AMOUNTS ARE EXPECTED TO RANGE AROUND 1-1.25 INCH.
PER THE HIGHER RESOLUTION GUIDANCE...ISOLATED HIGHER AMOUNTS OF
2-3+ INCHES WITHIN A 6-12 HOUR PERIOD WOULD LEAD TO LOCALIZED
RUNOFF ISSUES CONSIDERING THE RELATIVELY LOW FFG VALUES IN THE
AREA.

TERRY/PETERSEN/HURLEY
$$




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