Quantitative Precipitation Forecast
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FOUS30 KWBC 171356
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
954 AM EDT WED SEP 17 2014

...VALID 15Z WED SEP 17 2014 - 12Z THU SEP 18 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 ENE INW 20 SSE GNT 35 NNE 4CR 35 SSE LBB 7F9 15 SE PWG
15 NNW 62H AUS 25 N JCT 45 WSW SJT 30 N FST 50 WSW PEQ
55 SE MMCS 40 SSW MMCS 100 SW MMCS 70 SE DUG 60 S OLS 95 WSW OLS
100 SE YUM 30 SSW NYL 30 SW BLH 20 SE TRM 30 ENE RNM 25 ESE RIV
35 SSW DAG 15 ENE DAG 45 SSW DRA 15 N DRA 45 NNE DRA 45 WSW SGU
SGU 30 SE CDC 25 SW PGA 40 E GCN 35 NNW INW 30 ENE INW.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 SSE ALM 10 SSW LRU 40 SSW DMN 80 SSW DMN 45 SE OLS
40 SSW OLS 60 WSW OLS 80 WSW OLS 100 W OLS 90 S GBN 70 WSW TUS
40 NNW DMA 45 ESE IWA 60 WNW SAD 40 S SOW 25 SSE SOW 45 SE SJN
50 NW TCS 10 NNW SRR 25 E SRR ATS 20 SSW ATS 50 NW GDP
40 SSE ALM.


SOUTHWEST INTO THE SOUTHERN PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
LARGE SLIGHT TO MODERATE RISK AREAS WERE MAINTAINED ON THE LATEST
EXCESSIVE RAINFALL POTENTIAL OUTLOOK FROM THE SOUTHWEST INTO THE
SOUTHERN PLAINS AS WIDESPREAD HEAVY TO EXCESSIVE RAINFALL IS
LIKELY THIS PERIOD, PARTIALLY ASSOCIATED WITH THE CIRCULATION OF
ODILE.  WELL TO THE EAST OF THIS CIRCULATION, A MUCH ABOVE AVERAGE
PRECIPITABLE WATER (PW) AXIS WILL STRETCH FROM SOUTHERN
CA/SOUTHERN NV---EASTWARD INTO AZ---NM AND INTO THE SOUTHERN
PLAINS.  OBSERVED PW VALUES ACROSS THESE AREAS ARE NEAR THE 99TH
PERCENTILE (NEAR RECORD VALUES) FOR MID-SEPTEMBER AND THE
ANOMALOUS MOISTURE SHOULD REMAIN IN PLACE INTO THURSDAY MORNING.
MORE INSTABILITY SHOULD BE AVAILABLE TODAY AS AREAS OF
NORTHERNMOST MEXICO, WESTERN TX, AND SOUTHEAST NM ARE STARTING OUT
THE DAY WITH MINIMAL CLOUDINESS, WHICH SHOULD ALLOW DAYTIME
HEATING TO INCREASE MIXED LAYER CAPE VALUES >1000 J/KG AND
TRANSITION THE EVENT FROM A LONGER DURATION FLOOD EVENT TO MORE OF
A FLASH FLOOD EVENT WITH TIME.  THERE IS A STRONG MODEL SIGNAL FOR
HEAVY TO EXCESSIVE RAINFALL AMOUNTS ACROSS SOUTHEASTERN
AZ---SOUTHERN NM---LEADING TO HIGH CONFIDENCE ACROSS THESE AREAS.
FARTHER TO THE EAST FROM THESE AREAS--THERE IS MORE MODEL SPREAD
CONCERNING HOW QUICKLY HEAVY PRECIPITATION BREAKS OUT INTO THE
SOUTHERN PLAINS.  THE MESOSCALE MODELS ARE MORE EMPHATIC ACROSS
THIS AREA BUT STILL HAVE SOME SIGNIFICANT NORTH-SOUTH DIFFERENCES
WITH THEIR RESPECTIVE AXES.  CONFIDENCE IS LOWER HERE--BUT WITH
THE ABOVE MENTIONED HIGH PW AXIS AND MODEL FORECASTS OF UPPER
DIFFLUENCE MAXIMUM IN THIS HIGH PW AXIS---FAVOR THE IDEA OF
SPREADING HEAVY TO LOCALLY EXCESSIVE RAINFALL AMOUNTS EASTWARD
QUICKER.  WHILE MODELS DO NOT DEPICT MUCH PRECIPITATION ON THE
NORTHWESTERN PORTION OF THE ANOMALOUS PW AXIS FROM SOUTHERN CA
INTO SOUTHERN NV AND NW AZ---SCATTERED CONVECTION LIKELY AGAIN
ACROSS THESE AREAS--WITH LOCALLY HEAVY TO EXCESSIVE RAINFALL
AMOUNTS POSSIBLE.



SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NNW RUE 35 WNW CNU 25 SSE MHK LWC SZL 25 SSE TBN 30 W ARG
25 NW SRC 25 NNW RUE.

PORTIONS OF MO/AR/KS
~~~~~~~~~~~~~~~~~~~~
THUNDERSTORMS DEVELOPED THIS MORNING WITHIN A WARM ADVECTION
REGIME, FOCUSED JUST NORTHEAST OF A STATIONARY FRONT DUE TO SOME
CIN ALONG THE BOUNDARY.  INFLOW AT 850 HPA IS MODERATELY BROAD AND
ON THE ORDER OF 25-30 KTS ACROSS THE REGION.  MOST UNSTABLE CAPE
VALUES OF 1000-2000 J/KG LIE UPSTREAM ACROSS EASTERN KS AS WELL AS
SOUTHWEST MO.  PRECIPITABLE WATER VALUES ARE JUST OVER 1.5" PER
RECENT RAP GUIDANCE, WHICH SUPPORTS HOURLY RAIN RATES UP TO 2".
THE FORECAST IS FOR THE CONVECTION TO DROP SOUTHEAST INTO AR
BEFORE WANING BY MIDDAY.  SEE MPD #0378 FOR MORE DETAILS ON THIS
AREA THROUGH 16Z.

THE WESTERN EXTENT OF THE SURFACE FRONTAL BOUNDARY SHOULD REMAIN
STATIONARY TODAY.  SHORTWAVE ENERGY
IN THE NORTHWEST FLOW ALOFT MAY SPAWN A SECOND ROUND OF CONVECTION
TO THE NORTHEAST OF THIS BOUNDARY LATE WEDNESDAY NIGHT INTO EARLY
THURSDAY.  CONFIDENCE IS NOT HIGH WITH THE AXIS OF MAXIMUM
AMOUNTS---BUT THERE IS A GENERAL MODEL CONSENSUS FOR AN AXIS FROM
EASTERN KS INTO SOUTHERN MO---FAR NORTHEAST OK AND INTO NORTHERN
AR, CLOSE TO WHERE CONVECTION HAS FORMED/MOVED THIS MORNING.
WIDESPREAD MODERATE TO HEAVY RAINS ARE POSSIBLE FROM ORGANIZED
CONVECTION MOVING SOUTHEASTWARD WITHIN THIS AXIS.  SINCE FLASH
FLOOD GUIDANCE SHOULD LOWER DUE TO THE ONGOING ACTIVITY, WILL
CONTINUE THE SLIGHT RISK OF EXCESSIVE RAINFALL IN THIS AREA.



SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 SW HXD SVN 10 NW SAV 20 SE JYL 25 WNW NBC 30 SE OGB 40 E OGB
45 NNE CHS 40 WSW MYR 40 SSW MYR 30 E CHS 10 SW HXD.

COASTAL SOUTH CAROLINA
~~~~~~~~~~~~~~~~~~~~~~
A SLIGHT RISK REMAINS ACROSS COASTAL SOUTH CAROLINA FOR THE
POTENTIAL OF ANOTHER DAY OF SCATTERED CONVECTION.  A SURFACE
FRONTAL BOUNDARY WILL BE SINKING SOUTHEASTWARD THROUGH SOUTHERN
MID-ATLANTIC AND INTO THE SOUTHEAST THIS PERIOD.  WIDELY SCATTERED
CONVECTION REMAINS POSSIBLE WITHIN AN AXIS OF INCREASINGLY
UNSTABLE CONDITIONS WEDNESDAY AFTERNOON/EARLY EVENING.  PW VALUES
HAVE LOWERED FROM THE PREVIOUS DAYS---AS THE INITIAL FRONTAL
BOUNDARY HAS PUSHED SOUTHWARD BUT REMAIN NEAR SEASONAL LEVELS IN
THE 1.50-1.75" RANGE.  WITH WELL-DEFINED FRONTAL/PRE-FRONTAL
CONVERGENCE FORECAST ACROSS THE COASTAL SOUTHEAST WITH SEA BREEZE
BOUNDARIES ALSO POTENTIALLY AT PLAY TO REINFORCE SYNOPTIC FEATURES
IN THE AREA -- ADDITIONAL LOCALLY HEAVY TO ISOLATED EXCESSIVE
RAINFALL AMOUNTS ARE POSSIBLE FOR THE COASTAL CAROLINAS WHERE
HEAVY RAINS HAVE OCCURRED OVER THE PAST SEVERAL DAYS.  ISOLATED
2-4" AMOUNTS ARE POSSIBLE ACROSS COASTAL SECTIONS OF SOUTH
CAROLINA.

ROTH/ORAVEC
$$




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