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Excessive Rainfall Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1834Z May 04, 2015)
 
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Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
234 PM EDT MON MAY 04 2015

...VALID 18Z MON MAY 04 2015 - 00Z WED MAY 06 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 N FST 10 SW PEQ 30 ESE GDP 25 WSW CNM 25 WNW ROW 30 NNE 4CR
25 NNW CQC 20 NNE SKX 30 NNW VTP 35 ESE MYP 35 SE CCU 20 WSW BJC
15 WSW FNL 10 NNW DEN BKF 15 NE MNH 15 SE MNH 20 NNE PUB
15 ESE PUB 35 S LHX 15 ENE SPD 20 N PYX 30 ESE HHF 55 S CDS
30 ESE BPG 35 S BPG 40 SSE MAF 10 N FST.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NE PVW 40 WSW CDS 55 E LBB 25 NW SNK 35 NW BPG 35 NNW ODO
10 ESE HOB 30 WNW HOB 40 ENE ATS 60 NNW HOB 35 ESE CVN 25 NE PVW.


...FRONT RANGE OF THE ROCKIES SOUTHEASTWARD INTO THE SOUTHERN HIGH
PLAINS OF TX/OK/NM...

NO MAJOR CHANGES FROM PREVIOUS FCST AND REASONING ACRS THIS
REGION.  AS A SOUTHERN STREAM SHORTWAVE STRENGTHENS AND APPROACHES
FROM THE WEST...FLOW FIELDS AND MOISTURE TRANSPORT WILL
INCREASE...LEADING TO WIDESPREAD PRECIPITATION. SEASONABLY STRONG
HEATING AND SURFACE DEWPOINTS INCREASING TO THE UPPER 50S TO NEAR
60 DEGREES WILL CONTRIBUTE TO CAPE VALUES PEAKING AT THE LOWER END
OF MODERATE...AROUND 1000-1250 J/KG. THE MODELS HAVE CONSISTENTLY
ADVERTISED AN ORGANIZED HEAVY RAIN EVENT IN THIS AREA.  THE LOW
LEVEL JET IS FORECAST TO INCREASE ABOVE 50 KNOTS FROM THE SSE
AFTER 00Z UNDER INCREASINGLY FAVORABLE UPPER DIFFLUENT PATRN
BETWEEN SLIGHTLY NEG TILT UPR TROF AND STGR SUBTROPICAL JET WINDS
TO THE SOUTH.THE MODELS HAVE CONSISTENTLY PLACED THE MAXIMUM CAPE
AXIS AND 850 MB MOISTURE TRANSPORT OVER FAR SE NM AND SW
TX...BETWEEN LUBBOCK AND MIDLAND IN THE 00-09Z TIME FRAME. SMALL
LATITUDE DIFFERENCES REMAIN WITH PLACEMENT OF HEAVIER QPF MAX WITH
MOST GLOBAL MODELS A BIT NORTH OF THE 12Z HI RES GUIDANCE WITH THE
EXCEPETON OF THE GFS WHICH IS CLOSER TO HI RES GUIDANCE AXIS BUT
ALSO APPEARS TO BE SUFFERING FROM GRID SCALE FEEDBACK.   HAVE
STAYED CLOSER TO SRN END OF GUIDANCE ALONG WITH
CONTINUITY...TOWARD OPTIMUM UPR DIFFLUENCE AND INFLOW WITH MODELS
SUGGESTING AREAL AVG AMOUNTS IN EXCESS OF 3 INCHES WITH LOCALIZED
AMOUNTS IN EXCESS OF 5 INCHES WHERE CONVECTION BECOMES ANCHORED OR
SLOWER MOVING SUPPORTING A  MODERATE RISK OF RAINFALL EXCEEDING
FLASH FLOOD GUIDANCE.

A BROAD SLIGHT RISK AREA SURROUNDS THE MODERATE...AND INCLUDES
MUCH OF EASTERN NM AND THE OK/TX PANHANDLES. SLOW MOVING
SUPERCELLS WILL POSE SOME RISK OF HEAVY RAIN EARLY IN THE PERIOD
OVER NM...AND MOISTURE AND FORCING MECHANISMS INCREASE UP THROUGH
THE PANHANDLES OVERNIGHT.

A SECONDARY HEAVIER QPF MAX IS PSBL ALONG THE FRONT RANGE OF CO
WITH PERSISTENT ELY UPSLOPE CONDS THAT ARE EXPECTED TO LINGER
THROUGHOUT MUCH OF THE DAY 1 PD AS AXIS OF 5H TROF EVENTUALLY
LIFTS NEWD INTO THE SRN ROCKIES BY LATE TUE.  SOME EMBDD
CONVECTIVE ELEMENTS ARE LIKELY GIVEN INCREASING COLD POOL ALOFT
WHICH COULD RESULT IN LOCALIZED HEAVIER RAINFALL AMOUNTS AND A
RISK OF RUNOFF ISSUES AS A RESULT OF LOWER FFG VALUES ACRS THE
AREA.

...MO VALLEY/MIDWEST...

WELL DEFINED VORT OVER NCNTL KS EARLY THIS AFTN IS FORECAST TO
MOVE SLOWLY NEWD THEN EWD OVER CREST OF UPR RIDGE OVER THE MID MS
VALLEY LATE MON AFTN AND OVERNIGHT.  THE VORT IS EXPECTED TO TRACK
MORE OR LESS PARALLEL OR NEARLY PARALLEL TO WEAK FRONTAL BNDRY
THAT IS EXPECTED TO BECOME QSTNRY AND A BIT MORE E/W ORIENTED THRU
MON NIGHT/TUE MRNG.  THIS WILL LIKELY ENHANCE LIFT INTO THE BNDRY
WHERE POOLING OF 1.25 TO 1.5 INCH PWS IS EXPECTED ALONG WITH BROAD
20 TO 30 KT S TO SWLY 85H INFLOW.   HEATING SOUTH OF THE FRONT
WILL LEAD TO INCREASED INSTABILITY INTO THE BNDRY WITH CAPES FCST
TO APCH 1500 J/KG ACRS NE KS INTO SRN IA/NRN MO BY AFTN/EVEN.  ALL
THIS COULD LEAD TO INCREASING CONVECTION WITH POTNL FOR REPEAT
ACTIVITY/BACKBUILDING WITH BEST LOW LEVEL JET/INSTABILITY
CONTINUING TO FEED INTO THE BNDRY EVEN BEHIND PASSAGE OF MID LEVEL
VORT THOUGH THE MON OVERNIGHT PD.   FEEL GREATEST POTNL FOR
HEAVIER RAINS WILL BE FROM NE KS INTO SRN IA/NRN MO..PSBLY
EXTENDING INTO PORTIONS OF NRN IL..WITH POTNL FOR 1 TO 2 INCH
RAINFALL AMOUNTS.  FELT BLEND OF WRF ARW..NMM..AND NSSL WRF WERE
REASONABLE ACRS THIS AREA WHILE MOST OF THE GLOBAL MODELS WERE A
TAD FAR NORTH WITH THERE AXES. AT THIS TIME BELIEVE ANY FF THREAT
WILL BE RATHER ISOLD BUT WILL CONTINUE TO MONITOR.

SULLIVAN