Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 212204
QPFERD

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

...VALID 2203Z 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
80 SE YUM 20 W NYL 45 S HND 90 WNW SGU 25 SSE ELY 25 N MLF
35 NNE BCE 25 ENE BCE 65 NNW RQE 20 SSW FMN 25 WNW CPW 20 SE GUC
35 W FCS 20 S PUB 45 NNW TCC 10 WNW CVS 20 ESE MDD 35 WSW 05F
10 WSW JSO 25 NE JAN 35 ENE JAN 25 E ANB 15 S AHN 10 ESE HQU
15 NNW VDI 15 NNE MGR 45 SSW DTS 30 S KMIS 20 NNW S58 20 NW KCRH
KMZG 30 ESE BRO 20 SSE MMRX.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 SSE CWYQ 25 WSW PQI WVL 15 N WST 25 SE MJX 30 SSE MFV
10 SW GSB 10 SE HFF AKH 15 SSE FVX 15 NW 2W6 10 ENE MSV CYMX.

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
90 SW MMCS 70 E DUG 40 S GNT 30 SSE ABQ 20 SE 4CR 15 NW CNM
35 NNW MRF 70 W MRF.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 S MMPG MMPG 25 NE MMPG 20 N HDO 30 S BMQ GTU 20 ENE AUS
25 ESE HYI 25 WSW CLL 20 WSW CLL 11R 20 W 5R5 10 SSW ALI
25 S HBV 55 S MMNL 40 SW MMNL.


SOUTH TEXAS & GULF COAST
~~~~~~~~~~~~~~~~~~~~~~~~
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 SOUTHERN
TEXAS...WHERE THE REMAINING FORCING WAS ALSO SHOWING LESS OVERLAP
WITH THE AVAILABLE INSTABILITY POSITIONED CLOSER TO THE COAST.
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.  WE MAINTAINED A
SLIGHT RISK TO ACCOUNT FOR ONGOING FLOODING AND CONTINUED MODERATE
TO LOCALLY HEAVY RAIN EXPECTED OVERNIGHT IN AREAS OF WET
ANTECEDENT CONDITIONS.

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.  OTHER LOOSELY
ORGANIZED THUNDERSTORMS LIE ACROSS SOUTHERN MS AND SOUTHERN AL,
WITH OTHER ACTIVITY IN NORTHERN GA DROPPING SOUTHWARD.  LOCAL
AMOUNTS IN THIS REGION OF 2-4" WOULD NOT BE A SURPRISE.  CHANGES
WERE MADE PER RECENT RADAR TRENDS.


NEW ENGLAND/MID ATLANTIC/NORTH CAROLINA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.  CHANGES TO THE
AREA WERE MADE PER RECENT RADAR TRENDS.


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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