Quantitative Precipitation Forecast
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000
FOUS30 KWBC 291855
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 PM EDT MON MAY 29 2017

...VALID 21Z MON MAY 29 2017 - 12Z TUE MAY 30 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
CHA 15 E CHA 20 E CHA 25 NNW AVL 15 SSE TNB 20 ESE UKF
10 NE INT TDF 10 WNW LHZ 15 SE RDU 30 NW UDG 30 NE DNL 20 SW HQU
20 ENE CSG 55 NW GZH 25 NNW MCB HEZ 10 NNW HEZ 25 NW HEZ
30 E MLU 35 ENE BQP 25 E GLH 20 WNW GWO 40 WSW TUP 20 NNW TUP
25 WNW MSL 25 NE MSL 15 NW MDQ 10 N MDQ 20 W CHA CHA.


1900 UTC UPDATE

CHANGES TO THE PREVIOUS EXCESSIVE RAINFALL POTENTIAL OUTLOOK ARE
TO REMOVE THE MARGINAL RISK OVER PORTIONS OF SOUTH TX AS
CONVECTION HAS DIMINISHED ACROSS THIS REGION.  NO CHANGES MADE TO
THE OTHER MARGINAL RISK AREA FROM THE LOWER MS VALLEY INTO THE
SOUTHEAST AND SOUTHERN MID ATLANTIC.


1500 UTC UPDATE

CHANGES TO THE PREVIOUS EXCESSIVE RAINFALL POTENTIAL OUTLOOK WERE
TO CONCENTRATE THE LARGEST MARGINAL RISK AREA TO THE EAST AND
NORTHEAST OF THE VORT MOVING EASTWARD ALONG THE CENTRAL GULF
COAST.  THIS AREA WILL HAVE THE BEST LARGE SCALE LIFT IN A REGION
OF FAVORABLE RIGHT ENTRANCE REGION JET DYNAMICS.  THE MARGINAL
RISK AREA WAS EXTENDED SLIGHTLY TO THE NORTH AND NORTHEAST TO
COVER THE MODEL SPREAD ACROSS THESE REGIONS.

A SMALL MARGINAL RISK AREA WAS MAINTAINED OVER SOUTH TX FOR
CURRENT SLOW MOVING CONVECTION FIRING IN THE WAKE OF THE ORGANIZED
ACTIVITY THAT MOVED OFFSHORE EARLIER THIS MORNING.  THIS ACTIVITY
MAY MOVE ACROSS AREAS THAT RECEIVED HEAVY RAINS EARLIER.

ORAVEC

INITIAL DISCUSSION

...WESTERN GULF COAST NORTHEAST THROUGH THE LOWER MISSISSIPPI
VALLEY AND INTO THE SOUTHEAST...

THE SLOW-MOVING MID/UPPER LEVEL LOW ACROSS THE UPPER MIDWEST WILL
MAINTAIN THE CONFLUENT UPPER FLOW AND RESULTANT JET AXIS ACROSS
THE MID MS VALLEY INTO THE NORTHERN MID ATLANTIC-NORTHEAST REGION
DURING THE DAY 1 PERIOD. THIS SETUP WILL CONTINUE TO REINFORCE THE
QUASI-STATIONARY SURFACE BOUNDARY DRAPED FROM SOUTH TX ENE THROUGH
THE LOWER MS VALLEY...TN VALLEY...AND LOWER MID ATLANTIC REGION.
RAINFALL COVERAGE/INTENSITY ALONG AND SOUTH OF THIS BOUNDARY WILL
REMAIN THE PRIMARY FORECAST CHALLENGE...ESPECIALLY GIVEN THE
CONVECTIVE COMPONENT AS MID/UPPER LEVEL PERTURBATIONS (MCV/S)
CONTINUE TO CAUSE WAVES ALONG THE FRONT ALONG WITH A
RE-DISTRIBUTION OF DEEP LAYER FORCING.

THE NON-NAM MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE MORE
PRONOUNCED MCV ACROSS SOUTH TX EARLY MON LIFTING ENE ALONG THE
WESTERN-CENTRAL GULF COAST LATER MON-MON NIGHT. THE NAM MEANWHILE
IS AN OUTLIER SOLUTION IN THAT IT DEPICTS A MORE ELONGATED VORT
LOBE STRETCHING NORTHWARD IN THE LOWER MS/LOWER TN VALLEY. THE
TRACK OF THIS MCV... ALONG WITH ENHANCED DEEP-LAYER
ASCENT/LOW-LEVEL FGEN WITHIN THE RIGHT ENTRANCE REGION OF PERIODIC
UPPER JET STREAKS TRAVERSING THE MID MS VALLEY-OH VALLEY...WILL
MAINTAIN A NON-UNIFORMITY OF FAVORABLE FORCING AND THUS A SOMEWHAT
DISJOINTED PCPN PATTERN ALONG AND SOUTH OF THE SURFACE FRONT. WPC
CONTINUED TO LEAN MORE HEAVILY ON THE HIGH-RES CAMS...WRF-ARW AND
PARALLEL ARW IN PARTICULAR...WITH THE TIMING AND PLACEMENT OF
AMOUNTS.

DESPITE THE FAVORABLE THERMODYNAMIC PATTERN AHEAD OF THE FRONT
(PWS 1.75-2.0+ INCHES...MIXED-LAYER CAPES AOA 1500-2000
J/KG)...ALONG WITH THE DYNAMICAL FORCING AHEAD OF THE MCV AND/OR
WITHIN THE REGION OF FAVORABLE UPPER JET FORCING...THE RELATIVELY
WEAK LOW-LEVEL INFLOW AND NEGLIGIBLE MOISTURE FLUX ANOMALIES WILL
LIMIT THE PERSISTENCE OF HEAVY RAIN AREAS. MOREOVER...THE AIRMASS
BEHIND THE DEPARTING MCV WILL LIKELY REQUIRE SEVERAL HOURS TO
RE-DESTABILIZE. AS A RESULT...WPC WILL MAINTAIN ONLY A MARGINAL
RISK FOR EXCESSIVE RAINFALL...WITH THE ANTICIPATION THAT ANY
SHORT-TERM RUNOFF ISSUES WOULD BE ISOLATED AT MOST CONSIDERING THE
CURRENT SOIL MOISTURE/FFG VALUES.

HURLEY
$$




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