Quantitative Precipitation Forecast
Issued by NWS

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843
FOUS30 KWBC 140940
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
538 AM EDT THU SEP 14 2017

...VALID 12Z THU SEP 14 2017 - 12Z FRI SEP 15 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NNW RQE 55 NNW INW 15 W FLG 50 NW PRC 55 NNE IGM 15 SSE SGU
SGU 30 NW SGU 75 NW SGU 50 SW ELY 20 SSW EKO 30 W JER 25 NNW JER
25 WNW S14 25 N WYS 40 NNW COD 30 W SHR 20 WSW IDV HLD 35 S BVR
45 E VEL 35 N HDN 10 N 20V 15 SSE GUC 10 N E33 35 SE FMN
25 NNW RQE.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 WNW CMX 25 E BFW 10 NNE MZH 15 SSW PWC 20 N PKD 20 WNW FOZ
30 SSW CWCH 20 ESE CWDV 15 SW CXCA 45 E CWEC 30 NNW P59
45 WNW CMX.


...GREAT BASIN INTO THE NRN ROCKY STATES...

A COMPACT CLOSED LOW NOW OVER CA WILL LIFT NORTHEASTWARD INTO THE
GREAT BASIN TODAY AND INTO THE NRN ROCKIES BY EARLY MONDAY.
OVERALL...THERE IS STILL GOOD MASS FIELD AGREEMENT WITH THE
EVOLUTION OF THIS FEATURE IN THE LATEST GUIDANCE. WELL DEFINED
UPPER DIFFLUENCE IN AN AXIS OF ABOVE AVERAGE PW VALUES AHEAD OF
THIS CLOSED LOW WILL SUPPORT INCREASING PRECIPITATION COVERAGE
THROUGH THE GREAT BASIN. NRN STREAM HEIGHT FALLS DIVING SHARPLY
SOUTHEASTWARD THROUGH THE PAC NW WILL MEANWHILE STRONGLY AMPLIFY A
NRN STREAM UPPER TROF OVER THE N-CENTRAL GREAT BASIN AS SRN STREAM
SYSTEM APPROACH ENHANCES MOISTURE TRANSPORT INTO THE REGION. LARGE
SCALE LIFT AHEAD OF THESE HEIGHT FALLS COMBINED WITH POST FRONTAL
NORTHEASTERLY FLOW FROM THE NRN HIGH PLAINS INTO THE NRN ROCKIES
WILL SUPPORT SOME MODERATE TO LOCALLY HEAVY PRECIP TOTALS OVER THE
NRN ROCKY STATES. A COMBINATION OF WPC CONTINUITY AND MESO-MODEL
CONCENSUS SEEMED REASONABLY WELL CLUSTERED.A NRN ROCKIES PRECIP
CHANGE OVER TO SNOW WILL OCCUR IN RESPONSE TO LOWERING HEIGHTS
FROM THE AMPLIFYING TROF AND LOWER ATMOSPHERIC COOLING AND WINTER
WEATHER WATCHES AND ADVISORIES ARE ALREADY IN EFFECT. THE WPC
MARGINAL EXCESSIVE RAINFALL RISK COVERS AREAS FROM THE CENTRAL
GREAT BASIN TO THE NRN ROCKY STATES ALONG/SOUTH OF THE
COOLING/STABILIZING FRONT.

...NRN MN...

A STRENGTHENING SURFACE FRONTAL BOUNDARY WILL SINK SLOWLY
SOUTHEASTWARD THROUGH UPPER MS. SOUTHERLY LOW LEVEL FLOW IS
EXPECTED TO STRENGTHEN INTO THIS BOUNDARY THURSDAY AHEAD OF A
FRONTAL WAVE/UPPER IMPULSE. THIS WILL SUPPORT INCREASING PRECIP
CHANCES INTO FRIDAY FROM NRN MN AND FAR UPPER GREAT LAKES INTO
ONTARIO...INCLUDING A SW-NE SWATH OF MODERATE AMOUNTS UPWARDS TO
IN EXCESS OF ONE INCH WITH TRAINING. A WPC CONTINUITY AND
MESO-MODEL CONCENSUS SEEMS REASONABLY WELL CLUSTERED AND OFFERS
SOME MARGINAL EXCESSIVE RAINFALL THREAT.

SCHICHTEL

$$





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