Quantitative Precipitation Forecast
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127
FOUS30 KWBC 241858
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 PM EDT FRI MAR 24 2017

...VALID 21Z FRI MAR 24 2017 - 12Z SAT MAR 25 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SSE IRK 15 SE UIN 20 SSE PPQ 15 NNE FAM 25 SE JBR 15 W M97
30 NE LLQ 25 WSW TVR 25 WSW HEZ 20 S ESF 25 NNW BPT 10 ESE CXO
20 E CLL 30 S PSN 15 NW 4F4 25 WSW DEQ 15 NW RKR 15 SE GMJ
40 NW SGF 10 SSE SZL 45 NNE DMO 25 SSE IRK.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 S OFF 15 S ICL 10 S IXD 30 SSW IXD 20 NNE WLD 20 WSW ICT
35 SSW MHK 20 ESE HJH 15 SW LNK 15 S OFF.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
60 WNW SFO CCR 10 NNW WVI 90 W MRY.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 NE DEQ 15 WSW UNO 20 SE VIH 10 W FAM 10 ESE ARG 20 SSW SRC
15 NNE ELD 35 SSW MLU 20 WSW AEX 15 WSW JAS 25 SSW LFK
15 NNW LFK 20 SE GGG 20 ESE GGG 20 E GGG 20 ENE GGG 15 NE DEQ.


19Z UPDATE...

ACRS THE NCNTL CA COAST...THERE REMAINS A SMALL WINDOW OVER THE
NEXT COUPLE HRS OF HEAVY RAIN NEAR THE SFO BAY REGION AS FRONTAL
BNDRY CONTS TO PUSH SLOWLY SEWD.  HRLY RAINFALL RATEES UP TO .25
INCH OR SO HAVE BEEN NOTED...AND IMPROVING CONDS ARE EXPECTED ACRS
THIS AREA BY LATER THIS AFTN.

HAVE EXPANDED SLIGHT AND MARGINAL RISK AREAS ACRS PORTIONS OF THE
LOWER MS VALLEY/ERN TX WHILE ALSO ADDING A MARGINAL RISK AREA TO
PORTIONS OF SE NEB/ERN KS/NW MO/SW IA.   ACRS THE LATTER
AREA...STORMS DVLPG IN THE WARM SECTOR ACRS ERN KS WILL CONTINUE
TO BUILD NWD INTO WELL DEFINED NE/SW COLD FRONT ANCHORED ACRS SE
NEB.  FRONT WILL ACT AS ADDED FOCUS/LIFTING MECHANISM TO
CONVECTION AND AS ACTIVITY WILL MOVING IN COL REGION...STORMS HERE
COULD BE RATHER SLOW MOVING..CAPABLE OF PRODUCING SOME LOCALIZED
HEAVY RAINS.  RECENT HRRR RUNS..SUPPORTED BY MORNING HI RES RUNS
SUGGEST POTNL FOR LOCAL 2-3 INCH RAINS ACRS THIS REGION SUPPORTING
THE ADDITION OF A MARGINAL RISK OF EXCESSIVE RAINS.

FARTHER SOUTH...MORNING HI RES RUNS HAVE ALL CAUGHT ONTO THE IDEA
OF HEAVIER QPF POTNL ACRS ERN TX INTO NRN LA EXTENDING NEWD INTO
SRN MO WITH GREATEST THREAT OF HEAVY RAIN LIKELY ACRS ERN TX INTO
NRN LA/SRN AR IN RESPONSE TO WELL DEFINED VORT LOBE EXPECTED TO
MOVE ACRS CNTL TX THIS AFTN/EVENG.  ASSOCD HEIGHT FALLS AND
INCREASING DIFFLUENCE ALOFT WILL INTERACT WITH 40-50 KT SSWLY LOW
LEVEL JET AND PWS INCREASING TO 1.5 INCHES AND MODEL MUCAPES NEAR
2 THSD J/KG TO LIKELY LEAD TO A WELL DEFINED SQ LN DVLPMENT THAT
WILL PUSH SLOWLY ACRS THE REGION OVERNIGHT.  LOCAL RAINFALL RATES
OF 1 TO 2+" IN AN HOUR OR SO WILL BE PSBL WITH STORM TOTAL AMOUNTS
IN EXCESS OF 3 INCHES PSBLY LEADING TO RUNOFF ISSUES LATER THIS
AFTN AND DURING THE OVERNIGHT.  SULLIVAN  PREVIOUS DISCUSSION
FOLLOWS...


...ERN SRN PLAINS AND MID-LOWER MS VALLEY...

GUIDANCE REASONABLY AGREES THAT AN AMPLIFIED MID-UPPER LEVEL
TROUGH/CLOSED LOW WILL STEADILY PROGRESS FROM THE CENTRAL HIGH
PLAINS TOWARD THE MID-MS VALLEY DAY1. A WELL DEFINED COMMA
HEAD/DEFORMATION PRECIPITATION BAND WILL LIFT FROM ERN COLORADO
NEWD ACROSS THE CENTRAL PLAINS. FARTHER SOUTH UNDERNEATH...A
FAVORED GUIDANCE COMPOSITE FAVORING THE ARW AND WPC CONTINUITY
SHOWS A SWATH OF FAVORABLE INSTABILITY AND GULF OF MEXICO MOISTURE
ADVECTION AS PER AN ENHANCED/POTENT LLJ THAT WILL FUEL DEVELOPMENT
OF ORGANIZED BANDS OF STRONG TO SEVERE CONVECTION AS PER SPC AHEAD
OF A TRAILING ASSOCIATED COLD FRONT SLATED TO PUSH EASTWARD ACROSS
THE S-CENTRAL PLAINS AND MID-LOWER MS VALLEY. SUSPECT THAT
HEAVIEST RAINFALL WITH SOME TRAINING/RUNOFF ISSUE POTENTIAL WILL
FLOURISH OVER ERN OK/NERN TX AND THE MID-LOWER MS VALLEY FRI/FRI
NIGHT WHERE SOME LOCALLY HEAVY 2-4" AMOUNTS ARE
POSSIBLE...ESPECIALLY WITH SOME LOCAL TERRAIN LIFT INTO THE
OUACHITA AND OZARK MOUNTAINS.


N-CENTRAL CALIFORNIA COAST

BLENDED TPW LOOPS SHOW A LONG FETCH DEEPENED MOISTURE PLUME FROM
NORTH OF HAWAII TO THE WEST COAST WITH EMBEDDED DERIVED RAINFALL
RATES RANGING UP TO .25-.35" PER HOUR OFFSHORE WITH LOW/WAVE
POOLING. STRENGTHENING ONSHORE FLOW AND INCREASING PW VALUES ARE
EXPECTED TO PUSH SOUTHWARD OVER NRN AND CENTRAL CA ASSOCIATED AS A
SERIES OF IMPULSES WITHIN AN AMPLIFIED AND STEADILY PROGRESSIVE
ERN PACIFIC TROUGH APPROACH AND MOVE INLAND. THE GREATEST PW
ANOMALIES AND STRONGEST ONSHORE FLOW WITH THIS UPCOMING
ATMOSPHERIC RIVER EVENT ARE SLATED FOR THE N-CENTRAL CA COASTAL
RANGES THAT MAY LEAD TO RUNOFF ISSUES WHERE PW ANOMALIES WILL
REACH UPWARDS OF 2.5 STANDARD DEVIATIONS ABOVE THE MEAN.
WIDESPREAD HEAVY RAINFALL TOTALS OF 1-2"+ ARE LIKELY...WITH
DURATION MAX TOTALS OF 5"+ POSSIBLE THIS PERIOD IN THE FAVORED
UPSLOPE REGIONS.

SCHICHTEL
$$





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