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Excessive Rainfall Discussion
 
(Latest Discussion - Issued 0116Z Sep 20, 2014)
 
Version Selection
Versions back from latest:  0   1   2   3   4   5   6   7   8   9   10   
 
Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
915 PM EDT FRI SEP 19 2014

...VALID 03Z SAT SEP 20 2014 - 00Z SUN SEP 21 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 W MRF 45 NW MRF 35 SSE GDP 10 W GDP 35 SW ATS 35 WNW ATS
15 N ROW 55 S CVS 25 SE CVN 35 NNW PVW 15 W CDS 65 N ABI
35 NNE ABI 15 SW 6R9 15 NNW HYI 15 ESE 62H 35 NW BPT 15 ENE BPT
10 SE 7R5 25 W KVBS 20 SW GLS 30 S PSX 15 E 2R8 30 WNW ALI
45 SSE MMPG 15 W DRT 35 SSW 6R6 65 SSW 6R6 105 SW 6R6 60 SSW MRF
45 W MRF.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 SE PEQ 30 WNW PEQ 20 SSE CNM 20 ENE CNM HOB 25 WSW LBB
20 NNE LBB 50 ESE PVW 25 ENE SNK SWW 40 NW SJT 50 S MAF
20 SE PEQ.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 WNW GLS 15 SE LBX 15 SE PSX 10 E PKV 5R5 10 W HOU 10 WNW GLS.


03Z UPDATE...
ONLY CHANGE TO PREVIOUS OUTLOOK WAS TO REDUCE THE SLIGHT RISK ACRS
PARTS OF NM/NW TX WHERE ORGANIZED HEAVY RAIN THREAT APPEARS TO
HAVE DIMINISHED WITH SLOW EWD PROGRESSION OF WEAK 7H/5H SHEAR AXIS
(SUBTLE REMAINS OF ODILE).  LIKEWISE THE MDT RISK WAS TRIMMED
TOWARD CURRENT AREAS OF VERY LOW FFG VALUES AND EXPECTED HEAVIER
RAIN AXES ACRS W TX/EXTREME SE NM.  SULLIVAN   PREVIOUS DISCUSSION
FOLLOWS...   



SOUTHEAST NM/WESTERN TEXAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A DEEP MOISTURE PLUME ASSOCIATED WITH ODILE -- WITH PWS OF
1.50-1.75" -- ALONG WITH ANOTHER ANOMALOUS PW AXIS SETTING SAIL
WELL TO THE NORTH AND NORTHEAST OF T.S. POLO INTO WESTERN TX, WILL
CONTINUE TO OVERWASH A STALLED W-E STATIONARY FRONT ACROSS
SOUTH-CENTRAL AND SOUTHEAST TX THROUGH THE PERIOD. SOUTH TO
SOUTHEAST LOW-LEVEL FLOW WILL CONTINUE AHEAD OF ODILE'S
SLOW-MOVING CENTER OF CIRCULATION -- CURRENTLY VOYAGING THROUGH
SOUTH-CENTRAL NM -- WITH THE INFLOW WEAKENING DURING THE DAY TODAY
AND SATURDAY AND RESTRENGTHENING SOMEWHAT OVERNIGHT DUE TO THE
NOCTURNAL LOW-LEVEL JET.  WEAK ANTECEDENT UPPER-LEVEL FORCING
WITHIN THE BROAD UPPER RIDGE WILL GET A BOOST AHEAD OF THE
ODILE-RELATED CIRCULATION AND WITH INCREASED UPPER LEVEL
DIFFLUENCE.  SATURATED SOILS BEDEVIL THE REGION -- THEY CANNOT
STAND ANY ADDITIONAL RAINFALL FROM ANY SORT OF THUNDERSTORM,
REGARDLESS OF ITS CONVECTIVE MODE.  THUNDERSTORMS WHICH FORM
WITHIN THE REGION COULD ORGANIZE AS 0-6 KM BULK SHEAR IS NEAR 25
KTS.  CONVECTION SHOULD BECOME MORE PERIPHERAL TO THE CIRCULATION
DURING THE DAY AND CLOSER TO ITS CIRCULATION CENTER OVERNIGHT. 
PER THE MOST RECENT MESOSCALE QPF GUIDANCE... LOCALIZED AMOUNTS OF
4-8 INCHES ARE POSSIBLE -- MOST LIKELY OVER THE TRANS-PECOS AND
BIG COUNTRY PORTIONS OF TX AND SOUTHEAST NM WHERE THE MODERATE
RISK FOR EXCESSIVE RAINFALL WAS PLACED -- AS THE OVERALL
MOISTURE-RICH ENVIRONMENT (WARM RAIN PROCESSES) WILL CONTINUE TO
SUPPORT RAINFALL RATES UP TO 2.5" PER HOUR.


SOUTH-CENTRAL/SOUTHEAST TX
~~~~~~~~~~~~~~~~~~~~~~~~~~
A SEA OF ANOMALOUSLY HIGH MOISTURE, IN THE 2-2.5" PW RANGE, NEAR
TO ABOVE THE 90TH PERCENTILE FOR MID-SEPTEMBER, LIES CLOSER TO THE
SURFACE BOUNDARY OVER AN INCREASINGLY SATURATED AREA.  ACROSS
SOUTH-CENTRAL TX, CONVECTIVE ORGANIZATION IS POSSIBLE CONSIDERING
25 KTS OF 0-6 KM BULK SHEAR ADVERTISED BY RECENT RAP GUIDANCE. 
INSTABILITY CAUSED BY DAYTIME HEATING IN LEAGUE WITH THE AVAILABLE
MOISTURE SUPPLY SHOULD GUARANTEE THUNDERSTORM ACTIVITY WITH HEAVY
RAINFALL THIS AFTERNOON AND EVENING.  OTHER THUNDERSTORMS ARE
POSSIBLE ACROSS SOUTHEAST TX THIS AFTERNOON IF SUNNY SKIES BREAK
OUT LATER TODAY.  OVERNIGHT, ANOTHER BATCH OF THUNDERSTORMS IS
EXPECTED ACROSS THE MIDDLE AND UPPER TX COASTLINES NORTH OF THE
FRONTAL ZONE, WHICH SHOULD HAVE SOME ASSOCIATED CIN BY THAT TIME. 
HOURLY RAIN RATES IN THIS MOIST ENVIRONMENT COULD REACH 3" AN
HOUR.  SOME OF THE MESOSCALE GUIDANCE INDICATED THAT LOCAL AMOUNTS
OF 3-6" ARE POSSIBLE IN THIS REGION, SO MAINTAINED A MODERATE RISK
OF EXCESSIVE RAINFALL IN THIS REGION.


ARIZONA
~~~~~~~
PRECIPITABLE WATER VALUES (PWS) OF 1.75" COMBINED WITH DAYTIME
HEATING TODAY SHOULD LEAD TO TYPICAL MONSOON-LIKE THUNDERSTORM
DEVELOPMENT EARLY TONIGHT ACROSS SOUTHEAST AZ.  THE 0-6 KM BULK
SHEAR (20 KTS OR LESS) AND MAGNITUDE OF THE 700 HPA INFLOW (10
KTS) IMPLY SINGLE CELL/PULSE CONVECTION TODAY OVER ANYTHING
ORGANIZED.  HOURLY RAIN RATES UP TO 2" ARE POSSIBLE WHERE CELLS
MERGE, WHICH COULD LEAD TO A FEW POCKETS OF FLASH FLOODING THIS
AFTERNOON AND EVENING.  LIMITED FLASH FLOODING/DEBRIS FLOWS COULD
OCCUR AGAIN TOMORROW AFTERNOON AND EVENING AS WELL ACROSS THE
MOGOLLON RIM AND SOUTHERN WASATCH AS MOISTURE RETURNS INTO THE
REGION.  AREAL AVERAGE AMOUNTS OF 0.10-0.25" WERE DEPICTED FOR THE
MOST PART, IN LINE WITH THE 00Z GEFS- AND CLIMATOLOGY-BASED QPF
REFORECAST.

ROTH