Quantitative Precipitation Forecast
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000
FOUS30 KWBC 261444
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1043 AM EDT MON SEP 26 2016

...VALID 15Z MON SEP 26 2016 - 12Z TUE SEP 27 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
145 WNW MMMV 50 SSE E38 45 WSW SJT SJT 15 NE SJT 35 ENE SJT
45 S ABI 20 W BWD 15 SSW BWD 20 SSE 7F9 25 WNW 05F 15 NW GRK
10 W AUS 40 WNW VCT 20 NE VCT 25 NNW 5R5 10 S DWH 10 ENE IAH
40 ENE IAH 35 WNW BPT 20 WNW BPT 10 WNW BPT 10 WSW BPT
20 SSW BPT 15 NE KXIH.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
70 SSW 6R6 10 ENE 6R6 40 NE 6R6 45 NE 6R6 35 WSW E29 15 W E29
25 ENE E29 35 NW JCT 30 ESE SJT 30 E SJT 45 ENE SJT 40 WSW BWD
25 SW BWD 30 SSE BWD 40 SE BWD 35 WSW 05F 20 NW GRK 15 W GRK
10 NNE BMQ 10 SSE BAZ 35 ESE SSF 35 SE SSF 55 N ALI 15 S HBV
55 WNW MFE 65 S MMNL 45 S MMNL 30 S MMNL 15 S MMNL LRD
30 NNE LRD 15 E COT 35 NE COT 15 SE HDO HDO UVA 15 WSW UVA
20 E MMPG 25 SE MMPG 50 S MMPG.


1500 UTC UPDATE

CHANGES TO THE PREVIOUS EXCESSIVE RAINFALL POTENTIAL OUTLOOK WERE
BASED MOSTLY ON THE LATEST FFG VALUES THAT HAVE LOWERED ACROSS
SOUTH CENTRAL TO SOUTH TX FROM RECENT HEAVY RAINS.  THE SLIGHT
RISK AREA WAS EXPANDED EASTWARD INTO THE FAR SOUTHEASTERN PORTION
OF WFO SJT---FAR SW PORTION OF FWD---EASTWARD INTO THE CENTRAL EWX
WFO---WESTERN CRP AND FAR NORTHWEST BRO.  MODEL CONSENSUS IS FOR
THE BEST CHANCE OF RUNOFF ISSUES AT THE BEGINNING OF THIS FORECAST
PERIOD WHERE ADDITIONAL ISOLATED HEAVY TOTALS ARE
POSSIBLE---ESPECIALLY FROM EASTERN EWX INTO SOUTHEASTERN SJT WHERE
THE CURRENT AREA OF SLOW MOVING PRECIPITATION CONTINUES TO LINGER.
  LATEST VIS SATELLITE IMAGERY IS SHOWING SOME BREAKS IN THE
OVERCAST OVER SOUTH TX---POSSIBLY ENHANCING INSTABILITY AND
CONVECTIVE POTENTIAL.    BY LATER THIS AFTERNOON INTO THE
OVERNIGHT---MODEL CONSENSUS IS FOR THE AXIS OF HEAVIEST PRECIP TO
SINK SOUTH OF THE U.S./MEXICO BORDER---WITH A LESSENING OF THE
EXCESSIVE RAINFALL THREAT AT THIS TIME.

ORAVEC

PREVIOUS DISCUSSION

...SOUTH TEXAS...

CLOSED MID/UPPER LOW WILL REMAIN NEARLY STATIONARY ACROSS NW
MEXICO AND BAJA THIS PERIOD...WHILE THE NORTHERN STREAM TROUGH
CONTINUES TO AMPLIFY INTO A MID-UPPER CLOSED LOW ACROSS THE UPPER
GREAT LAKES. THE MODELS CONTINUE TO SHOW WEAK SUPPORT FOR UPPER
FORCING ACROSS TX IN BETWEEN THESE TWO SYSTEMS... WITH AN UPPER
LEVEL SHEAR AXIS AND A QUASI-STATIONARY SURFACE BOUNDARY OVER
SOUTH TX AND WEAK UPPER DIFFLUENCE EAST OF THE UPPER LOW ACROSS
SOUTHERN AZ/NM INTO WEST TX. MEANWHILE...THE MORE ANOMALOUS PWS
(2.00+ INCHES) WILL CONTINUE TO PRESS SOUTH WITH TIME TOWARD THE
TX GULF COAST...WHILE MODEST PW ANOMALIES (AROUND 1.5 STANDARD
DEVIATIONS ABOVE NORMAL) ALIGN W-E ACROSS SOUTHERN AZ/NM INTO WEST
TX. INSTABILITY WILL ALSO BECOME MORE CONFINED TOWARD SOUTH TX AND
THE GULF COAST WITH TIME DURING THE PERIOD...WITH ONLY MIN MAL
CAPES (200-400 J/KG) ACROSS FAR SOUTHERN AZ NORTH OF THE UPPER
LOW. IN TERMS OF THE QPF...THE 00Z GFS AND ESPECIALLY ECMWF HAVE
TRENDED LIGHTER DURING THE DAY 1 PERIOD ACROSS SOUTH-CENTRAL TX
AND AREAS WEST INTO THE SOUTHWEST...WHICH IS NOT SURPRISING GIVEN
THE WEAKENING SYNOPTIC SUPPORT AND LACK OF DEEP INSTABILITY.
HIGHEST AREAL-AVERAGE TOTALS FROM 12Z MON-12Z TUE WERE BETWEEN
0.50-1.0" ALONG THE RIO GRAND EAST OF THE BIG BEND FROM DRT TO
LRD...WITH A SECONDARY AXIS ALONG THE SOUTH TX GULF COAST BETWEEN
CRP AND BRO WHERE THE INSTABILITY AND 2+ INCH PWS WILL PERSIST.
THE HIGH-RES CAMS SHOW LOCALIZED 3-5" TOTALS ON THE MEXICAN SIDE
OF THE RIO GRANDE...WITH A FEW POCKETS OF 3-5" AMOUNTS ALONG THE
LOWER AND MIDDLE TX COAST. OUTSIDE OF THE ARES ALONG THE RIO GRAND
(NEAR DRT) HIT HARD BY THE RECENT HEAVY RAINS (THUS HAVING LOWER
FFG)...THE RISK FOR FLASH FLOODING DURING DAY 1 APPEARS TO BE
MARGINAL AT BEST.

HURLEY
$$




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