Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 220105
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
905 PM EDT THU AUG 21 2014

...VALID 03Z FRI AUG 22 2014 - 00Z SAT AUG 23 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 E HEI 15 SSE HEI 10 E 2WX 55 WSW 2WX 35 ESE MLS 15 NNW GDV
15 SW ISN 20 ENE KS25 15 SSE KHZE 35 E HEI.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 ENE IND 15 WSW MQB 20 SE CNC 10 SSW DSM 15 E AMW 15 SE MRJ
35 WSW MKG 10 NNW TOL 10 NW BJJ 20 E PHD AFJ 15 NE MGW
25 SSW 2G4 10 SSE EKN 30 NNE LWB 20 NNE BKW 20 NNW I16 25 SE HTS
35 WNW HTS 15 SSE ILN 10 NNW HAO 15 ENE IND.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 NNE BIL 40 WSW BIL 15 S LVM 20 SSE BZN 35 SSE HLN 20 WNW HLN
40 NNE 3DU 40 S 8S0 30 SSW CTB 25 ESE CTB 55 N GFA 40 SSW HVR
50 NNE LWT 35 ENE LWT 15 NNE BIL.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 S RUT 20 E GFL 15 NE SCH 15 WSW PSF 10 WSW DXR NYC 15 SW EWR
15 SSE MPO AVP 40 NW AVP 25 SE ELM 10 W BGM 20 NNE SYR
25 ESE GTB 30 SE OGS 15 W SLK 15 SSE SLK 20 SW BTV MPV
15 NNE LEB LEB VSF 20 S RUT.


MID MS VALLEY/MID WEST---TOWARD THE UPPER OH VALLEY/CENTRAL
APPALACHIANS


OVERALL---NO BIG CHANGES MADE TO THE PREVIOUS SLIGHT RISK AREA
DEPICTED FROM THE MID MS VALLEY TOWARD THE UPPER OH VALLEY/CENTRAL
APPALACHIANS REGION.
AN ACTIVE CONVECTIVE PATTERN EXPECTED IN THE VICINITY OF A FRONTAL
BOUNDARY AND ASSOCIATED AXIS OF ABOVE AVERAGE PW VALUES---1 TO 2
STANDARD DEVIATIONS ABOVE THE MEAN---STRETCHING FROM THE MID MS
VALLEY/LOWER LAKES TOWARD THE UPPER MS VALLEY THIS PERIOD.
CONFIDENCE HAS DECREASED WITH RESPECT TO THE DETAILS OF THE TIMING
OF AREAS OF CONVECTION AS THERE IS LARGE MODEL TO MODEL
DIFFERENCES AND LARGE RUN TO RUN DIFFERENCES---ESPECIALLY IN THE
HI RES GUIDANCE WHICH OFTEN WILL DEPICT THESE ORGANIZED CONVECTIVE
REGIONS BETTER.  MOIST WEST SOUTHWESTERLY FLOW INTO THIS BOUNDARY
AND ENHANCED UVVS ASSOCIATED WITH SHORTWAVES MOVING ALONG THE
SOUTHERN EDGE OF THE WESTERLIES WILL SUPPORT ADDITIONAL CONVECTIVE
DEVELOPMENT ALONG THIS FRONT.  THERE IS POTENTIAL FOR TRAINING OF
CELLS IN A GENERAL WEST NORTHWEST TO EAST SOUTHEAST DIRECTION THIS
PERIOD---SUPPORTING HEAVY TO ISOLATED EXCESSIVE RAINFALL AMOUNTS.
ALONG WITH THE DIFFERENCES IN TIMING AMONG THE MODELS---THERE IS
DIFFERENCES LATITUDE WISE WITH THE MAX QPF AXES.  THE FARTHER
SOUTHWARD OVERALL AXIS OF THE NAM WAS FAVORED -ALTHOUGH AMOUNTS
WERE INCREASED GIVEN TRAINING POTENTIAL.  WHILE THERE IS A LOT OF
DIFFERENCES IN QPF AXES---THERE IS A SIGNAL FOR POTENTIAL OF VERY
HEAVY RAINFALL TOTALS IN THE HI RES GUIDANCE.  IN AREAS OF
TRAINING---ISOLATED TOTALS OF 1-2"+ IN AN HOUR AND TOTALS OF 3-5"+
POSSIBLE.

SOUTHERN TIER OF NY--NORTHERN NY INTO NORTHERN NEW ENGLAND

EXPANDED SLIGHT RISK AREA SWD INTO NRN NJ BASED ON RADAR/SFC DATA
WHICH SHOWS BAND OF TSTMS EXTENDING FROM NRN NJ INTO NE PA THAT
WERE CONTINUING TO FEED OFF ON NARROW PLUME OF MODEST MLCAPES
ALONG FAVORABLE LOW LEVEL CONFLUENT BNDRY.  SOME HIGH RES GUIDANCE
SUGGESTS A LOCAL MAXIMA OVER THE SRN PORTION OF THE SLIGHT RISK
AREA WITH LOCAL AMOUNTS IN EXCESS OF 3 TO 4 INCHES.  THIS
CERTAINLY IS PSBL GIVEN AREA IS IN LEFT EXIT REGION OF JET STREAK
WHICH MAY AID BROAD SCALE ASCENT OVER THE AREA DURING THE
OVERNIGHT INTO EARLY FRI.  FARTHER NORTH....TRIMMED NRN PORTION OF
EARLY SLIGHT RISK AREA WHERE MID LEVEL CIRC CONTS TO WEAKEN ALONG
WITH GRADUAL DIMISHING CONVECTION..BUT STILL COULD NOT RULE OUT
SOME SPOTTY STGR STORMS THROUGH MIDNIGHT.


NORTHERN ROCKIES INTO THE NORTHERN PLAINS

ONLY SLIGHT CHANGES FROM PREVIOUS ISSUANCE.  THE MEAN TROF ACROSS
THE NORTHWESTERN U.S. WILL AMPLIFY DAY 1 IN RESPONSE TO SHORTWAVE
ENERGY DIVING SOUTHEASTWARD FROM OFF THE B.C. COAST INTO THE
PACIFIC NORTHWEST TONIGHT AND EASTWARD ACROSS THE NORTHERN ROCKIES
FRIDAY.  MODEL CONSENSUS IS FOR TWO PRIMARY AREAS OF PRECIPITATION
WITH THIS AMPLIFYING TROF.  AN INITIAL BATCH OF PRECIP ASSOCIATED
WITH A LEAD SHORTWAVE EJECTING OUT OF THE MEAN TROF POSITION
TONIGHT INTO THE NORTHERN HIGH PLAINS---EAST NORTHEASTWARD INTO
THE REMAINDER OF THE NORTHERN PLAINS DURING FRIDAY.  THIS WILL BE
FOLLOWED BY ANOTHER ORGANIZE AREA OF PRECIPITATION FORMING
UPSTREAM ACROSS THE NORTHERN ROCKIES/NORTHERN HIGH PLAINS IN
RESPONSE TO THE MID TO UPPER TROF AMPLIFICATION AND STRENGTHENING
LOW LEVEL EASTERLY TO NORTHEASTERLY FLOW. WITH FFG VALUES
RELATIVELY LOW ACROSS THESE AREAS---ISOLATED RUNOFF ISSUES MAY
DEVELOP WITH EACH ROUND OF ORGANIZED PRECIPITATION.

SOUTHWEST---SOUTHERN ROCKIES INTO THE SOUTHERN HIGH PLAINS

TO THE SOUTH OF THE AMPLIFYING UPPER TROF OVER THE NORTHWEST--THE
CLOSED LOW INITIALLY OFF THE SOUTHERN CA COAST WILL BE KICKED
INLAND THROUGH THE SOUTHWEST AND TOWARD THE SOUTHERN
ROCKIES/SOUTHERN HIGH PLAINS.  WIDESPREAD SHOWERS EXPECTED TO
CONTINUE AHEAD OF THIS CLOSED LOW IN A REGION OF WELL DEFINED
UPPER DIFFLUENCE AND ABOVE AVERAGE PW VALUES.  ISOLATED HEAVY TO
EXCESSIVE PRECIPITATION TOTALS POSSIBLE THIS PERIOD AHEAD OF THIS
TROF--ALTHOUGH CONFIDENCE ON PLACEMENT IS LOW.

ORAVEC/SULLIVAN
$$





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