Quantitative Precipitation Forecast
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FOUS30 KWBC 040828
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
327 AM EST SUN DEC 04 2016

...VALID 12Z SUN DEC 04 2016 - 12Z MON DEC 05 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
90 ESE PIL 10 E BRO 45 S MMNL 85 NW MMMV 85 S MRF E38 30 SE SJT
20 SSE PSN 20 NE TVR 15 ENE 1M4 30 NNE 1A5 20 NW 45J 35 SE SSC
30 WSW EZM 65 SW AAF.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 ENE HBG 20 ENE EET 25 SSE RHP AND 20 NE OPN 15 W LSF CEW
10 ESE JKA 20 SE BIX 15 NNE HSA 15 ENE HBG.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
KOPM 20 S BKS 45 NW MMNL 60 WSW DRT 35 ESE 6R6 25 WSW JCT
15 E LHB 30 ESE OCH 20 SSE IER 20 SSE ESF 20 NW LFT 10 NNE KCMB
20 WNW KEHC.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NNW KMZG 15 NNW 5R5 20 E UTS 25 WNW POE 15 N ACP 20 S ACP
10 NNE 7R5 25 SW KCRH.


...TEXAS AND THE LOWER MISSISSIPPI VALLEY INTO THE SOUTHEAST AND
LOWER MID ATLANTIC REGION...

...MODERATE RISK FOR EXCESSIVE RAINFALL WILL PERSIST OVER PORTIONS
THE WESTERN GULF COAST...

BENEFICIAL RAINFALL IS EXPECTED IN THE SOUTHEAST STATES...AREAS
WHERE DROUGHT HAD BECOME WIDESPREAD. THIS MORNING A CLOSED LOW
OVER MEXICO WAS REACHING PERHAPS ITS MOST MATURE PHASE...WITH
GREATEST DEGREE OF AMPLIFICATION AND INFLECTION IN THE
FLOW...LEADING INTO THE STRENGTHENING OF A DOWNSTREAM UPPER JET
OVER THE MIDWEST AND OHIO VALLEY. MEANWHILE... 500 MB HEIGHT
ANOMALIES WITH THE CLOSED LOW OVER THE SOUTHERN SEA OF CORTEZ ARE
BETWEEN 5 AND 6 STANDARD DEVIATIONS BELOW NORMAL. RAINFALL WAS
WIDESPREAD WITHIN THE WARM ADVECTION REGIME IN BETWEEN THE
LOCATION OF THE UPPER JET AND A SURFACE FRONT NEAR THE WESTERN
GULF COAST.

RAINFALL WAS ESPECIALLY FOCUSED WHERE CONFLUENT DEFORMATION AND
RESULTANT STRENGTHENING FRONTOGENESIS BETWEEN 850-700 WERE TAKING
PLACE...FROM THE WESTERN GULF COAST NORTHEAST THROUGH CENTRAL LA
AND INTO CENTRAL-NORTHERN MS...NORTHERN AL...AND MUCH OF TN.
MEANWHILE...THE MORE FAVORABLE THERMODYNAMICAL PROFILE (ANOMALOUS
PWS NEAR 2 INCHES...HIGHER AVAILABLE DEEP-LAYER INSTABILITY...AND
WET BULB 0C HEIGHTS ABOVE 12KFT) WILL AGAIN MAKE FOR MORE
EFFICIENT WARM RAIN PROCESSES AND HIGHEST SHORT-TERM RAINFALL
RATES AND THUS THE BEST POTENTIAL FOR FLASH FLOODING CLOSER TO THE
COAST FROM THE MID-UPPER TX COAST INTO WESTERN LA. ALREADY HIT
HARD FROM THE RECENT HEAVY RAINFALL (LOWERING 1-3 HOURLY FFG
VALUES RATES SIGNIFICANTLY)...A MODERATE RISK FOR ADDITIONAL FLASH
FLOODING WILL ENCOMPASS THE AFOREMENTIONED AREA PER THE NEW DAY 1
EXCESSIVE RAINFALL OUTLOOK. DEPENDING ON HOW MUCH RECOVERY IS
OBSERVED WITH THE RUNOFF AND (THUS) SHORT-TERM FFG WITH ANY BREAKS
IN THE HEAVIER RAINFALL...A HIGH RISK MAY BE NEEDED LATER TODAY
(AS LATER SHIFTS WILL EVALUATE). FARTHER INLAND HAD BEEN MORE
TAME...ALTHOUGH STILL DELIVERING A WIDESPREAD SOAKING TO MUCH OF
THE REGION...AND SETTING UP THE POSSIBILITY OF SOME LONGER
DURATION FLOODING IN THE MORE SUSCEPTIBLE LOCATIONS.

THE COMBINATION OF SUSTAINED FAVORABLE UPPER DIFFLUENCE AHEAD OF
THE SOUTHERN STREAM CLOSED LOW...ALONG WITH THE ELONGATED 850-700
MB FRONTAL ZONE EXTENDING E-NE (SUPPORTED BY THE 130-150+ KT JET
STREAK TO THE NORTH)...WILL MAKE FOR AN EXPANSIVE WARM CONVEYOR
BELT (WCB)...WHERE THE NORTHERN PORTION WILL BECOME SHUNTED MORE
W-E WITH TIME AS THE SOUTHERN PERIPHERY OF THE NORTHERN STREAM
SHORTWAVE LEADS TO STRENGTHENING UPPER LEVEL CONFLUENCE (INCREASED
ZONAL FLOW AND A STRONGER UPPER JET) OVER THE MIDWEST AND OHIO
VALLEY. THEREFORE WILL EVENTUALLY SEE A SHARPER NORTHERN EDGE TO
THE MOD-HEAVY RAINFALL AS THE ACTIVITY SPREADS FARTHER EAST INTO
THE MID ATLANTIC REGION. WPC QPF INCORPORATED A BLEND OF
CONTINUITY (PREVIOUS FORECAST) ALONG WITH A NON-NAM/NON-UKMET
BLEND OF GUIDANCE WHICH ALSO INCLUDED THE WRF-ARW...NMMB...AND
NSSL-WRF. A RATHER LARGE SWATH OF 0.50-1.00+ INCH AREAL-AVERAGE
AMOUNTS IS AGAIN FORECAST FROM THE SOUTHERN HALF OF TX E-NE
THROUGH MUCH OF THE SOUTHEAST AND LOWER MID ATLANTIC REGION.
FAIRLY GOOD MODEL CONSENSUS (ESPECIALLY WITH THE HIGH-RES CAMS)
WOULD SUPPORT MAX TOTALS AGAIN ALONG THE MID-UPPER TX COAST INTO
SOUTHWEST LA (STRONG DEEP-LAYER FORCING WITH MORE FAVORABLE
THERMODYNAMICS) AS WELL AS ACROSS EASTERN LA...SOUTHERN
MS...SOUTHERN-CENTRAL AL...AND NORTHERN GA ALONG THE
AFOREMENTIONED AXIS OF STRONGEST 850-700 MB FGEN.

HURLEY
$$





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