Quantitative Precipitation Forecast
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FOUS30 KWBC 171810
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
203 PM EDT WED SEP 17 2014

...VALID 18Z WED SEP 17 2014 - 00Z FRI SEP 19 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 45 SW GNT 30 NNW GNT 30 WSW AEG 15 E ABQ 10 ENE 4MY
25 SW LVS 10 SE LVS 45 W AMA 40 ESE LBB 40 SSW RPH 10 SE SEP
10 NE UTS 20 WSW BPT GLS 10 NE BYY 25 NNW T82 30 SSE SJT
45 WSW SJT 30 N FST 50 WSW PEQ 55 SE MMCS 40 SSW MMCS
100 SW MMCS 80 SE DUG 70 WSW OLS 30 S YUM 20 ENE IPL 25 SSE TRM
20 SW NJK CZZ 30 N RNM 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 85 SSW DMN 25 S DUG 30 WSW OLS
90 SSE GBN 50 SSE GBN CGZ 50 S SOW 50 E SJN 15 S GNT 50 SSE GNT
45 NE TCS 35 SSW 4MY 30 NNW 4CR 40 ENE 4CR 35 ENE ROW 25 ESE ATS
35 W CNM 50 NW GDP 40 SSE ALM.

SOUTHWEST/SOUTHERN PLAINS/TEXAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
LARGE SLIGHT TO MODERATE RISK AREAS WERE MAINTAINED ON THE LATEST
EXCESSIVE RAINFALL POTENTIAL OUTLOOK FROM THE SOUTHWEST INTO TEXAS
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 THROUGH TX.  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.  INSTABILITY SHOULD BE LESS OF AN ISSUE TODAY AS
AREAS OF NORTHERNMOST MEXICO, WESTERN TX, AND SOUTHEAST NM HAVE
BEEN SUBJECT TO DAYTIME HEATING, WHICH HAS INCREASED MIXED LAYER
CAPE VALUES TO ROUGHLY 1000 J/KG PER THE MOST RECENT SPC
MESOANALYSIS.

CONSIDERING THE AVAILABLE MOISTURE, HOURLY RAIN RATES UP TO 3" ARE
POSSIBLE ANYWHERE WITH THIS REGION.  THE HOUSTON/GALVESTON TX
OFFICE REPORTED RAIN RATES OF 1.28" IN 30 MINUTES WITHIN THE
INITIAL THUNDERSTORMS THAT FORMED LATE THIS MORNING.  THERE IS A
STRONG MODEL SIGNAL FOR HEAVY TO EXCESSIVE RAINFALL AMOUNTS ACROSS
SOUTHEASTERN AZ---SOUTHERN NM---LEADING TO HIGH CONFIDENCE ACROSS
THESE AREAS.  THE MOST RECENT MESOSCALE GUIDANCE INDICATES LOCAL
AMOUNTS OF 5-8" IN THIS REGION FROM THIS AFTERNOON INTO THURSDAY.

MODEL SPREAD CONTINUES CONCERNING EXACTLY WHERE HEAVY RAIN
DEVELOPS ACROSS TEXAS.  THE MESOSCALE MODELS ARE QUITE EMPHATIC
ACROSS THIS AREA, BUT UNCERTAINTY IN LOCATION HAS PREVENTED THE
INCLUSION OF A MODERATE RISK.  WITH THE ABOVE MENTIONED HIGH PW
AXIS AND MODEL FORECASTS OF UPPER DIFFLUENCE MAXIMUM UNDER AN
UPPER LEVEL HIGH 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
35 SE FYV 30 WNW PPF 25 SSE MHK LWC SZL TBN ARG 15 W SRC
35 SE FYV.

PORTIONS OF MO/AR/KS
~~~~~~~~~~~~~~~~~~~~
THE WESTERN EXTENT OF THE SURFACE FRONTAL BOUNDARY SHOULD REMAIN
STATIONARY TODAY, WHICH SHOULD CONTINUE TO POOL PWS OF 1.50-1.75"
PER RECENT RAP RUNS.  SHORTWAVE ENERGY IN THE NORTHWEST FLOW ALOFT
MAY SPAWN A COUPLE ROUNDS OF CONVECTION NEAR AND TO THE NORTHEAST
OF THIS BOUNDARY.  CONFIDENCE IS NOT HIGH WITH THE AXIS OF MAXIMUM
AMOUNTS---BUT THERE IS A GENERAL MODEL CONSENSUS FOR MAXIMUM
AMOUNTS NEAR THE KS/OK/MO BORDER JUNCTION.  WIDESPREAD MODERATE TO
HEAVY RAINS ARE POSSIBLE FROM ORGANIZED CONVECTION MOVING
SOUTHEASTWARD WITHIN THIS AXIS.  SINCE FLASH FLOOD GUIDANCE HAS
BEEN LOWERED DUE TO RECENT ACTIVITY, WILL CONTINUE TO INCLUDE A
SLIGHT RISK OF EXCESSIVE RAINFALL IN THIS AREA.


COASTAL CAROLINAS
~~~~~~~~~~~~~~~~~~
DUE TO RECENT CONVECTIVE EVOLUTION AND A RECENT SAB/NESDIS
BRIEFING SHOWING TWO SMALLER FOCI FOR AFTERNOON CONVECTION ACROSS
THE COASTAL CAROLINAS, DOWNGRADED THE SLIGHT RISK AREA TO A "SEE
TEXT" HIGHLIGHT.  A SURFACE FRONTAL BOUNDARY WILL BE SINKING
SOUTHEASTWARD THROUGH SOUTHERN MID-ATLANTIC AND INTO THE
SOUTHEAST.  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 THE CAROLINAS.

ROTH
$$





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