Quantitative Precipitation Forecast
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FOUS30 KWBC 221408
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1008 AM EDT MON MAY 22 2017

...VALID 15Z MON MAY 22 2017 - 12Z TUE MAY 23 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
50 SSE KMZG 15 NNW KOPM 15 SSW NQI 25 N ALI 35 SE BAZ 45 W IER
20 SW GTR 15 E 8A0 15 WNW IPJ 20 SE NCA 30 WNW CHS 10 NNW VAD
10 WSW AAF 75 ENE KIPN.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 SE KBQX 15 SE 2R8 25 NNW RKP 25 WNW 5R5 35 E CXO 10 SW AEX
25 NE HEZ 15 SSW TCL 20 NNE ALX 25 E TOI CEW 20 N KVOA
10 WNW RAM 20 SW KMYT.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 SSW SRN 10 N KXIH 25 W BPT 25 S ACP 25 N BTR HBG 40 N MOB
15 NE BFM 20 N KMIS 20 NNE S58.


15Z UPDATE...

ONLY MINOR ADJUSTMENTS WERE MADE TO PREVIOUS EXCESSIVE RAINFALL
OUTLOOK..MAINLY ALONG THE WEST END ACROSS TX WHERE THE HEAVIER
RAIN THREAT CONTINUES TO DIMINISH AS VEERING 85H FLOW CONTINUES TO
DIRECT HIGHER PWS TOWARD THE VERY UPPER TX COAST AND POINTS EWD.
HI RES MODELS CONTINUE TO STRUGGLE WITH MORNING CONVECTION ACROSS
THE NORTHERN GULF WITH NO CLEAR WINNER WITH REGARD TO SHORT TERM
MODEL TRENDS.  STRONGER CONVECTION CONTINUES TO HOLD JUST EAST OF
THE MID TEXAS COAST AS OF 13Z WHICH WAS LIMITING WELL ORGANIZED
CONVECTION ALONG THE WARM FRONT WHICH HAS WORKED SLOWLY INLAND
INTO THE UPPER TX COAST AND SW LA.  ELEVATED CONVECTION WELL TO
THE NORTH OF THE FRONT HAS PRODUCED AVERAGE 3 HOURLY RATES OF .25
TO .50 INCH MOST AREAS ACRS ERN TX INTO WCTNL LA THROUGH THE
MORNING HOURS WITH SPOTTY LOCALIZED HEAVIER AMOUNTS.  THOUGH
TIMING OF STRONGER AND MORE ORGANIZED SURFACE BASED CONVECTION
REMAINS A CHALLENGE...STILL EXPECT HEAVIER RAINS TO BECOME BETTER
ORGANIZED BY AFTERNOON INTO THE OVERNIGHT HOURS ACRS THE EXTREME
UPPER TX COAST EWD THROUGH SRN LA INTO SRN MS AS LOW PRES BEGINS
TO DVLP ALONG THE RETURNING WARM FRONT AND ENHANCES CONVERGENCE
INTO THE BNDRY.  WITH PWS EXPECTED TO BE NEAR 2"..SO SLOW MOVING
CONVECTION WITH HEAVY RAIN RATES ARE LIKELY...WITH POTENTIAL
MAXIMA OF 5"+ POSSIBLE WHERE TRAINING OF CELLS OCCURS.  SULLIVAN
PREVIOUS DISCUSSION FOLLOWS.


MID TO UPPER TX COAST---CENTRAL GULF COAST/LOWER MS VALLEY INTO
THE SOUTHEAST

THERE WERE ONLY SOME MINOR CHANGES MADE TO THE PREVIOUS EXCESSIVE
RAINFALL POTENTIAL OUTLOOK FOR THE UPCOMING DAY 1 PERIOD FROM THE
MID TO UPPER TX COAST---EASTWARD ACROSS THE LOWER MS
VALLEY/CENTRAL GULF COASTAL REGION AND INTO THE SOUTHEAST. A BROAD
RISK REGION MAINTAINED IN THE VICINITY OF THE SURFACE FRONTAL
BOUNDARY THAT IS EXPECTED TO REMAIN NEARLY STATIONARY THIS
FORECAST FROM SOUTH TX EASTWARD ALONG THE CENTRAL GULF COAST AND
THEN NORTHEASTWARD INTO THE SOUTHEAST/SOUTHERN APPALACHIANS.
WITH PW VALUES EXPECTED TO REMAIN MUCH ABOVE AVERAGE IN THE
VICINITY OF THIS FRONT--1.5 TO 2+ STANDARD DEVIATIONS ABOVE THE
MEAN---AND STRONG LARGE SCALE LIFT ASSOCIATED WITH HEIGHT FALLS
PUSHING EASTWARD IN THE VICINITY OF THIS FRONT FROM SOUTH
TX---ALONG THE GULF COAST AND INTO THE SOUTHEAST---THERE IS A
STRONG MODEL SIGNAL FOR WIDESPREAD HEAVY TO LOCALLY EXCESSIVE
RAINFALL AMOUNTS.  THERE ARE STILL SOME SIGNIFICANT DIFFERENCES
WITH THE MAX QPF AXES AMONG THE MODELS.  THE FARTHER SOUTHWARD
AXES OF THE ARW---NMMB AND THEIR PARALLEL VERSIONS---ALONG WITH
THE NAM CONEST AND CMC GEM WERE PREFERRED OVER THE FARTHER
NORTHWARD GFS AND EC SOLUTIONS.  THE NAM AND GFS HAVE BEEN SHOWING
A SOUTHWARD TREND OVER THE PAST FEW RUNS WITH THEIR MAX QPF
AXIS---TOWARD THE FARTHER SOUTHWARD HI RES RUNS. THE
ECMWF---HOWEVER---HAS SHOWN THE OPPOSITE.  WHILE CONFIDENCE IS NOT
GREAT WITH THE SHORTER TERM DETAILS---EXPECT AN INITIAL AREA OF
HEAVY RAINS TO SPREAD EASTWARD MONDAY MORNING FROM COASTAL TX INTO
THE CENTRAL GULF COAST---PUSHING INTO THE SOUTHEASTERN U.S. LATER
MONDAY INTO MONDAY NIGHT.  IN THE WAKE OF THIS
ACTIVITY---ADDITIONAL CONVECTION MAY FIRE ALONG THE STATIONARY
FRONT FROM COASTAL TX INTO THE CENTRAL GULF COAST.  TRAINING OF
CELLS PARALLEL TO THE FRONT POSSIBLE AS MOIST WEST SOUTHWESTERLY
LOW LEVEL FLOW PERSISTS PARALLEL TO THIS FRONT INTO EARLY TUESDAY.
 WIDESPREAD 1-3" AREAL AVERAGE AMOUNTS DEPICTED DAY 1 ACROSS THESE
AREAS---WITH POTENTIAL FOR MAXIMA OF 5"+ WHERE TRAINING OF CELLS
OCCURS WITH BOTH ROUNDS OF ORGANIZED PRECIP.  SEE WPC`S MESOSCALE
PRECIPITATION DISCUSSION #0258 VALID UNTIL APPROXIMATELY 1400 UTC
FOR ADDITIONAL INFORMATION ON THE DEVELOPING CONVECTION ALONG THE
TX GULF COAST.


ORAVEC

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