Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 200808
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
407 AM EDT TUE SEP 20 2016

...VALID 12Z TUE SEP 20 2016 - 12Z WED SEP 21 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SSE OLS 55 SW OLS 80 S GBN 75 SW GBN 40 SE YUM 15 SSW NYL
25 SE IPL 25 ESE CZZ 10 SW CZZ NRS NZY 10 NW RNM 25 NE NFG
15 E RIV 25 NNW PSP 10 WSW NXP 20 E NXP 45 ENE NXP 25 WSW EED
15 N EED 20 NW IGM 45 N IGM 55 S SGU 45 SE SGU 45 ESE SGU
55 SSW BCE 35 S BCE 20 WSW PGA 30 E GCN 35 NNE FLG 20 ENE FLG
15 SW INW 25 SSE INW 10 WSW SOW 35 S SOW 35 NW SAD 30 W SAD
40 SW SAD 40 NNE FHU 15 E FHU 25 SSE OLS.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 SE HSE 10 SSE NKT 20 SW OAJ 15 S MEB 15 SSE VUJ HBI 15 N BUY
PTB 35 ESE MFV 55 ESE WAL 85 ESE OXB.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
ALO 15 S MCW EST 10 E OTG 20 NW MWM RWF 10 SSW HCD 10 WSW FCM
25 N ONA 10 NW VOK 10 NNE DLL EFT 15 ESE MXO ALO.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 ENE HSE 15 NE EWN ISO JNX 15 N LHZ FKN 40 E NTU 75 SE MFV.


NORTHEAST NORTH CAROLINA INTO FAR SOUTHEAST VIRGINIA

AN UPPER LOW EXPECTED TO CLOSE OFF AND BECOME NEARLY STATIONARY
OVER EASTERN SC TUESDAY INTO EARLY WEDNESDAY. THIS SHOULD HELP
ANCHOR WEAK SURFACE LOW PRESSURE OFF SOUTHEAST NC AND MAINTAIN
MOIST CYCLONIC FLOW---PW VALUES 2.00-2.25"+... INTO EASTERN NC AND
FAR SOUTHEAST VIRGINIA.  WITH THE EXPECTED SLOW MOTION OF THIS
CLOSED LOW AND SUSTAINED CYCLONIC FLOW---HEAVY PRECIP TOTALS
LIKELY TO THE NORTH AND NORTHWEST OF THIS CIRCULATION
CENTER---IMPACTING AREAS FROM FAR SOUTHEAST VIRGINIA INTO
NORTHEAST NORTH CAROLINA.  AS PER THE PMDHMD---THE GFS IS AN
OUTLIER WITH THE PLACEMENT OF THE LOW ALONG THE NC COAST AND IS
FARTHER TO THE NORTHEAST WITH ITS QPF---NOT BRINGING HEAVY TOTALS
BACK INLAND AS PER THE MODEL CONSENSUS. ISOLATED RUNOFF ISSUES MAY
DEVELOP OVER NORTHEAST NC AND FAR SOUTHEAST VIRGINIA WHERE THE
MOST PERSISTENT RAIN BANDS SET UP.  IN AREAS WHERE THE RAIN BANDS
PERSIST...ISOLATED TOTALS OF 4-6"+ POSSIBLE.  A SLIGHT RISK OF
EXCESSIVE RAINFALL AMOUNTS WAS MAINTAINED FROM CONTINUITY OF THE
OLD DAY 2 FORECAST.

SOUTHERN CALIFORNIA INTO ARIZONA

WHILE TROPICAL STORM PAINE IS EXPECTED TO WEAKEN...AS PER THE
LATEST NHC DISCUSSION...MUCH ABOVE AVERAGE PW VALUES WILL CONTINUE
TO BE DRAWN NORTHWARD IN THE MID LEVEL SOUTHERN FLOW BETWEEN THE
SOUTHERN PLAINS UPPER HIGH AND THE CLOSED LOW OFF THE SOUTHERN
CALIFORNIA/NORTHERN BAJA COAST.  WIDESPREAD SCATTERED SHOWER
ACTIVITY LIKELY FROM SOUTHERN CALIFORNIA INTO THE SOUTHWEST.
WITH CLOUD COVER WIDESPREAD---INSTABILITY MAY BE LIMITED--LIMITING
THE PRECIPITATION POTENTIAL.  THERE IS A LOT OF MODEL QPF
DIFFERENCES LEADING TO LOW CONFIDENCE---WITH THE IN HOUSE PSEUDO
BIAS CORRECTED MEAN USED TO MITIGATE THOSE DIFFERENCES.  ISOLATED
HEAVY PRECIP TOTAL AND RUNOFF ISSUES POSSIBLE WHERE ANY LESSENING
CLOUD COVER WILL INCREASE INSTABILITY.  A BROAD MARGINAL RISK AREA
WAS MAINTAINED FROM SOUTHERN CA INTO MOST OF ARIZONA.

UPPER MS VALLEY

LOW LEVEL SOUTHWESTERLY TO WESTERLY FLOW EXPECTED TO STRENGTHEN
TUESDAY EVENING INTO THE EARLY HOURS OF WEDNESDAY ALONG AND INTO
THE STRENGTHENING WARM FRONTAL BOUNDARY FORECAST TO STRETCH FROM
THE NORTHERN PLAINS INTO THE UPPER MS VALLEY THIS PERIOD.  THIS
WILL SUPPORT INCREASING CONVECTION ALONG AND NORTH OF THIS
FRONT--WITH ACTIVITY STRETCHING FROM SOUTHERN MN---INTO NORTHEAST
IA AND SOUTHWEST WI.  THIS WILL BE THE FIRST DAY OF A POTENTIAL
MULTI DAY ACTIVE CONVECTION PATTERN ALONG AND NORTH OF THIS
BOUNDARY.   FOR THIS FIRST DAY---MODEL CONSENSUS IS FOR MODERATE
TO LOCALLY HEAVY PRECIP TOTALS---WITH INCREASING PRECIP POTENTIAL
DURING THE DAY 2 TIME PERIOD.  STILL---CAN`T RULE OUT A PERIOD OF
ORGANIZED CONVECTION AND ISOLATED RUNOFF ISSUES IN AREAS WHERE
TRAINING OCCURS---WITH A MARGINAL RISK AREA DEPICTED FOR THIS OVER
SOUTHERN MN---NORTHEAST IA INTO SOUTHWEST WI.

ORAVEC
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