Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 212011
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
410 PM EDT SUN AUG 21 2016

...VALID 21Z SUN AUG 21 2016 - 12Z MON AUG 22 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 SSE CWYQ 25 WSW PQI WVL ORH 35 ESE MJX 15 ENE WAL ISO
15 NNW CUB 10 SSW RMG HKY 25 N FVX MPO 10 NE CMHN.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
85 S YUM 25 WSW BLH 70 N LSV 45 WNW MLF 35 NNE BCE 35 S PGA
65 SE PGA GUP 40 NW 4SL 25 ENE DRO 25 WNW CPW 20 SE GUC 35 W FCS
20 S PUB 35 NNW TCC 15 SW CVS 20 ESE HOB 20 NW E29 10 SSW 6R9
35 ESE ACT 20 SE BAD 30 NNE PIB MOB 30 NNE KVKY 10 E KXPY
20 NW KCRH KMZG 35 ESE MMMA 120 NNE MMTM.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 NE TPH 30 E BIH 45 W MMH 15 E BLU 60 S NFL 60 W P68
30 NE TPH.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
80 ESE DUG 20 SSW SVC 45 NNW TCS 20 SSW SAF 25 NNW LVS
55 WNW CVS 35 E ATS 30 ESE GDP 80 N MMCU.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
150 ESE MMCU 85 SSW 6R6 30 SW 6R6 25 ENE 6R6 20 SE ERV
20 NW UTS 30 W IER 15 NE ESF 35 SE ESF 15 S ACP 35 W BPT
15 S BYY 15 SE KRP 75 SW MMRX.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
65 NW MMMV 75 SW MMPG 35 WNW MMPG 15 W UVA 10 W SKF 20 SE HYI
3T5 30 ESE 3T5 20 NNW 5R5 VCT 10 W ALI 15 S HBV 55 S MMNL
40 WNW MMAN.


SOUTH TEXAS
~~~~~~~~~~~
WIDESPREAD CONVECTIVE RAINS OVERNIGHT HAD CONTINUED TO FEED BACK
ONTO THE HEIGHT FIELD...REINFORCING A BROAD CIRCULATION...WHILE
SMALLER SCALE MCVS WERE SHED EASTWARD. THE LARGER SCALE MCV WAS
DRIFTING WESTWARD PER RADAR IMAGERY...BUT THIS ENTIRE REGION OF
MID/UPPER LEVEL FORCING SHOULD GENERALLY BEGIN TO SHEAR OUT AS A
NORTHERN STREAM DEEP TROUGH STARTS TO PULL AWAY FROM THE
REGION...AND RETURN FLOW STARTS TO SET UP AHEAD OF A TROUGH OVER
THE SOUTHWEST STATES. THE NET EFFECT OF THESE CHANGES WILL BE TO
LESSEN THE DEGREE OF ORGANIZATION TO THE CONVECTION OVER DEEP
SOUTH TEXAS...WHERE THE REMAINING FORCING WAS ALSO SHOWING LESS
OVERLAP WITH THE AVAILABLE INSTABILITY POSITIONED CLOSER TO THE
COAST. STILL...SMALL SCALE STORMS CONTAINING HEAVY RAIN RATES WILL
OCCUR ALONG THE FORCING / INSTABILITY INTERFACE...AND MAY BE
EVENTUALLY REINFORCED OR REPLACED BY SEA BREEZE ACTIVITY.
THEREFORE...WE MAINTAINED A MODERATE RISK TO ACCOUNT FOR ONGOING
FLOODING AND CONTINUED MODERATE TO LOCALLY HEAVY RAIN IN AREAS OF
WET ANTECEDENT CONDITIONS.


LOUISIANA
~~~~~~~~~
WEAK BUT PERSISTENT UPPER DIVERGENCE ALONG THE INTERFACE BETWEEN
THE NORTHERN STREAM TROUGH AND THE TEXAS CIRCULATION ALONG WITH
OUTFLOW BOUNDARIES SET IN MOTION FROM LAST NIGHT`S CONVECTION WILL
SHIFT LOUISIANA THIS AFTERNOON AND EVENING. TYPICALLY THIS LOOSELY
ORGANIZED PATTERN WOULD WARRANT ONLY A MARGINAL RISK OF EXCESSIVE
RAINFALL...BUT GIVEN RECENT HEAVY RAINFALL...SIX TIMES CLIMATOLOGY
OVER THE PAST SEVEN DAYS...AND ONGOING RIVER FLOODING...WE
EXPANDED A SLIGHT RISK INTO THIS REGION.  CHANGES WERE MADE PER
RECENT RADAR TRENDS.


NEW ENGLAND/MID ATLANTIC/SOUTHERN APPALACHIANS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A WELL DEFINED/AMPLIFIED UPPER TROUGH WILL SWEEP INTO THIS REGION
TODAY. A NARROW AXIS OF ABOVE AVERAGE PW VALUES...2 TO 2.5
STANDARD DEVIATIONS ABOVE THE MEAN...WILL PERSIST ALONG AND AHEAD
OF THE ASSOCIATED FRONT. STRONG FRONTAL CONVERGENCE IN THIS HIGH
PW AXIS WILL SUPPORT POTENTIAL FOR ORGANIZED FRONTAL/PRE-FRONTAL
CONVECTION AND MODERATE TO HEAVY PRECIPITATION RATES. THE QUICK
MOVEMENT OF THE FRONT AND ASSOCIATED CONVECTION SHOULD BE A
LIMITING FACTOR FOR VERY HEAVY TOTALS. INSTABILITY IS ALSO
QUESTIONABLE...WITH EXTENSIVE HIGH CLOUDINESS DURING THE MORNING
AND EARLY AFTERNOON HOURS HERE...OWING TO WARM ADVECTION NORTH OF
A RETREATING FRONT LOCATED IN NORTH CAROLINA / VIRGINIA. THESE
LIMITING FACTORS HAVE KEPT THE PROBABILITY OF EXCESSIVE RAINFALL
AT ANY GIVEN POINT DOWN IN THE MARGINAL CATEGORY.  REMOVED THE
SLIGHT RISK DUE TO THE STRATIFORM NATURE OF THE RAINFALL AND
LIMITED INSTABILITY ACROSS EASTERN NY AND NEW ENGLAND.


GREAT BASIN/DESERT SOUTHWEST/SOUTHERN HIGH PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A STREAM OF SHORTWAVE ENERGY STRETCHING FROM SOUTHERN CALIFORNIA
INTO THE SOUTHWEST AND SOUTHERN HIGH PLAINS WILL SUPPORT ANOTHER
ROUND OF WIDESPREAD SCATTERED CONVECTION ACROSS THESE AREAS THIS
FORECAST PERIOD. MODEL CONSENSUS FOR PLACEMENT OF MAX TOTALS IS
FROM SOUTHWEST TX INTO CENTRAL TO WESTERN NEW MEXICO IN THE
VICINITY OF THE STATIONARY FRONTAL BOUNDARY. AREAL AVERAGE
MODERATE TOTALS DEPICTED...WITH LIKELIHOOD OF HEAVIER TOTALS AND
ISOLATED RUNOFF ISSUES IN THE VICINITY OF THIS FRONT. ISOLATED
RUNOFF ISSUES ALSO POSSIBLE OVER INTO CENTRAL TO SOUTHERN ARIZONA
WITH THE NEXT ROUND OF SCATTERED CONVECTION ACROSS THIS REGION
LATE SUNDAY INTO THE EARLY MORNING HOURS OF MONDAY.  A SMALL
POCKET OF CONVECTION ACROSS WESTERN NV AND EASTERN CA HAS ALSO
RECENTLY POPPED UP, WHICH COULD CAUSE ISSUES IN ANY NEARBY BURN
SCARS.

ROTH/BURKE/ORAVEC
$$





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