Quantitative Precipitation Forecast
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000
FOUS30 KWBC 291411
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1011 AM EDT WED MAR 29 2017

...VALID 15Z WED MAR 29 2017 - 12Z THU MAR 30 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 WNW DVN 15 SSW MUT 10 WNW EOK 40 NE COU 30 NE VIH 30 WSW FAM
15 NW POF 25 WNW NQA 20 ENE GLH 25 SSW ACP KGVX 10 E KBQX
35 NW KBBF 10 S PKV 15 WNW SGR 15 WNW GGG RKR 15 SSE GMJ
25 N CNU 30 S MHK 20 E CNK 15 WNW BIE 10 N OMA 10 NW CIN
20 WSW FOD 20 SSE MCW 10 WNW PDC 20 S MRJ 20 N SFY 15 WNW CWI
15 WNW DVN.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SE FSM 30 ESE FSM 30 N ROG 45 SSE OJC 10 NE LWC 35 NW TOP
30 S BIE 10 S OFF 20 SE CIN 25 NW MIW 20 ESE MIW 10 ENE TNU
10 NNE CNC 25 SSE CNC 25 NNW IRK IRK 40 NNW COU 20 N AIZ
45 ENE UNO 35 N ARG 20 SE M19 20 WNW GLH 20 SSW MLU GLS
20 NW LBX 15 S TXK 25 WSW MWT 25 SE FSM.


1500 UTC UPDATE

CHANGES TO THE PREVIOUS EXCESSIVE RAINFALL POTENTIAL OUTLOOK WERE
TO EXTEND THE MARGINAL AND SLIGHT RISK AREA SOUTHWARD INTO THE
UPPER COASTAL AREAS OF TX.  THIS WAS TO ACCOUNT FOR THE ORGANIZED
AREA OF CONVECTION ON THE SOUTHERN END OF THE PRE-FRONTAL SQUALL
LINE.   RADAR ESTIMATES ARE SHOWING HOURLY TOTALS OF 1.5"+ WITH
THIS LINE.  IT APPEARS THIS ACTIVITY WILL BE MOVING ACROSS THE
HOUSTON METRO AREA OVER THE NEXT SEVERAL HOURS---WITH URBAN RUNOFF
ISSUES INCREASING ACROSS THESE AREAS.  THERE STILL IS A LOT OF
UNCERTAINTIES WITH THE DETAILS OF HOW CONVECTION WILL EVOLVE
THROUGH TODAY AND INTO ANOTHER POSSIBLE ENHANCEMENT LATER THIS
AFTERNOON INTO THE OVERNIGHT HOURS OF EARLY THURSDAY.
SUBSEQUENTLY---NO CHANGES WERE MADE NORTHWARD THROUGH AR---MO AND
IA.  THE WESTERN END OF THE COMMA HEAD REGION WAS TRIMMED OVER
WESTERN TO CENTRAL KS.

ORAVEC

PREVIOUS DISCUSSION

...S-CENTRAL PLAINS AND MID-LOWER MS VALLEY...

AN IMPRESSIVE CONVECTION/RAINFALL AREA ONGOING ACROSS THE
S-CENTRAL US AS A 50+KT LLJ PUMPS PWS UPWARDS OF 1.25-1.5" UP
THROUGH THE PLAINS. THIS IS NEAR 3 STANDARD DEVIATIONS ABOVE
NORMAL. EXPECT A CONTINUED HEAVY RAIN THREAT WILL PERSIST WED INTO
THU AS A MAIN CLOSED TROUGH LOW AND SURFACE LOW/FRONTAL SYSTEM
STEADILY TRACKS FROM THE SRN PLAINS TOWARD THE MID MS VALLEY. WAVY
LEAD CONVECTIVE MESO BOUNDARIES WILL SET NEW LOW LEVEL CONVERGENCE
FOCI TO REFORM CONVECTION DURING THE PERIOD. COMMA SHAPED WRAPPED
HEAVIER PCPN ENHANCED BY DEFORMATION TO THE NORTH OF THE CLOSED
LOW...HEIGHT FALLS/INSTABILITY AS PER SPC...AND LEAD THETAE
ADVECTIONS AND EMBEDDED MCVS NOW ON RADAR OVER TX/OK/KS WILL
OVERALL LIKEWISE SHIFT NEWD AND EWD...FURTHER AIDED BY CONVECTIVE
COLD POOL TRANSLATION AND RENEWED CONVECTIVE DEVELOPMENTS THROUGH
DAY 1. THIS SHOULD SUPPORT A WRAP-AROUND/PIVOT AXIS OF SOME 1" TO
SPOTTY 3" RAIN AMOUNTS FROM W-CENTRAL KS NEWD INTO IA/NRN MO AND
AN AXIS OF MORE UNCERTAIN TO TIME/PROGRESS STRONG CONVECTION FROM
ERN KS/OK/TX INTO THE MID-LOWER MS VALLEY WED INTO THU. SOME
ELEMENTS MAY MERGE/TRAIN WITHIN THIS MORE N-S ORIENTED AXIS
ALIGNED WITH A CONTINUED POTENT FLOW OF SRLY LLJ ENHANCED MOISTURE
TO PRODUCE SOME LOCAL 2-4" TOTALS THAT MAY OFFER ADDITIONAL FOCUS
WITH TERRAIN. USED A BLEND OF WPC CONTINUITY AND THE 00 UTC NMMB
THAT MESHED REASONABLY WELL.

...NWRN US...

GUIDANCE HAS REMAINED REASONABLY CONSISTENT OVERALL WITH MASS
FIELDS AND INDICATIONS THAT LEAD IMPULSES RIDING ALOFT OVER AN
ENHANCED PLUME OF ERN PACIFIC MOISTURE WILL SUPPORT A PERIOD OF
MODERATE TO HEAVIER PCPN SPREAD INLAND FROM THE PAC NW TO THE NRN
INTERMOUNTAIN WEST/ROCKIES TODAY. AN 50+ KT WSWRLY LLJ WILL FEED A
PLUME UPWARDS OF 1.25" PWS INTO THE WA/OR/NWRN CA COASTLINE AND
LATEST STLT PASSES SHOW SOME EMBEDDED .25"/HOUR RAINFALL RATES
WITH WAVE DEVELOPMENT OFFSHORE IN THE MAIN MOISTURE PLUME WITH
LONG FETCH CONNECTION WELL BACK TO THE NORTH OF HAWAII. THIS MAY
TRANSLATE TO SOME LOCALLY TERRAIN ENHANCED LIQUID AMOUNTS WED OF
1-3+ OVER COASTAL RANGES INLAND TO THE CASCADES AND TO A LESSER
EXTENT THE BLUE...SAWTOOTH...AND BITTEROOT RANGES WHERE SOME
RUNOFF ISSUES ARE POSSIBLE. HEIGHT FALLS WITH STRONGER EPAC
SHORTWAVE TROUGH APPROACH ARE EXPECTED TO SWEEP INTO THE PAC NW
LATER WED INTO THU...PROVIDING STRONG DYNAMICS AND CONTINUED
UNSETTLED CONDITIONS AS THE DEEPER MOISTURE CUTS OFF/SHIFTS SEWD.

SCHICHTEL
$$




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