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Excessive Rainfall Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0123Z Jul 25, 2014)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
923 PM EDT THU JUL 24 2014

...VALID 03Z FRI JUL 25 2014 - 00Z SAT JUL 26 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NE BLH 45 W EED 30 SW HND 30 NNE LSV 25 NW SGU 30 NE CDC
40 NE BCE 20 NNE 4HV 50 NE U28 40 SE VEL 10 WSW HDN 25 ENE 20V
30 ENE MYP 20 ENE CPW 15 E DRO 70 S 4BL PRC 20 NE BLH.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
50 SSE HSE 50 SE MRH 40 ESE ILM 15 SE EYF FAY POB 10 SE TTA
10 WNW JNX 10 NE ISO 20 E OCW 25 WSW MQI 15 ESE MQI 40 ESE MQI
40 ENE HSE 35 E HSE 50 SSE HSE.


...EASTERN NORTH CAROLINA...

ONLY SLIGHT CHANGES TO SLIGHT RISK AREA ACRS PARTS OF ERN NC WITH
SOME CONTINUED SHORT TERM THREAT OF LOCALLY HEAVY CNVTV RAINS THRU
THE EARLY OVERNIGHT AS ORGANIZED TSTMS CONTINUE TO DROP SEWD ACRS
THE REGION WORKING OFF OF RESIDUAL AFTN CAPES AND HI PWS SOUTH OF
MDTLY STG COLD FRONT.  MAIN THREAT IS WHERE CELL MERGERS MAY ALLOW
STGR CONVECTION TO HANG UP BRIEFLY RESULTING IN SHORT TERM
RAINFALL AMOUNTS OF OVER 2 INCHES IN AN HOUR OR SO.  MOST GUIDANCE
SUGGEST ACTIVITY WILL BEGIN TO WEAKEN AND SHIFT SEWD WITH THE
APCHG COLD FRONT AFTER MIDNIGHT...BUT AT LEAST THRU MIDNIGHT POTNL
WILL EXIST FOR SO PSBL RUNOFF ISSUES FROM STGR ORGANIZED TSTMS
DROPPING SEWD ACRS THE ERN PORTION OF NC.


...COLORADO/UTAH...

PER EARLY MORNING RAOBS...AND SATELLITE AND MODEL ANALYSES...A
MOISTURE PLUME WAS BEING DRAWN UP AROUND THE IMMEDIATE WEST SIDE
OF THE UPPER RIDGE CENTER...AND INTO EASTERN UTAH/WESTERN
COLORADO. NAM/RAP/HRRR FORECASTS INDICATE RESPECTABLE CAPE OF
500-750 J/KG BY MIDDAY...WHILE ASCENT AND INFLOW AT CLOUD BASE
BECOMES SLIGHTLY ENHANCED BY THE DEEP NORTHWESTERN U.S. CYCLONE
BRUSHING ACROSS THE PERIPHERY OF THE UPPER RIDGE. THIS SUGGESTS
SOME ORGANIZATION OF CONVECTIVE STORMS TODAY A BIT GREATER THAN
USUAL...WITH SOME POTENTIAL FOR BACK-BUILDING AND BRIEF TRAINING
EPISODES AS THE ENHANCED 700-600 MB SOUTHWESTERLIES SUPPORT
REDEVELOPMENT ALONG OUTFLOWS. PRECIPITABLE WATER WILL LIKELY
INCREASE TO ABOUT 1.10 INCHES...OR 1.5 TO 2 STANDARD DEVIATIONS
FROM CLIMATOLOGY. THOUGH THIS REGION HAS NOT BEEN PARTICULARLY WET
RECENTLY...BASED ON 14-DAY DEPARTURES FROM NORMAL...THE TYPICALLY
FLASHY TERRAIN FEATURES MAY RECEIVE QUICK DOSES OF 0.75 INCHES OR
MORE OF RAINFALL. GIVEN THE WELL DEFINED SYNOPTIC SITUATION AND
CLUSTERING OF HIGH RESOLUTION MODEL QPFS...WE INTRODUCED A SLIGHT
RISK OF EXCESSIVE RAINFALL FOR UT/CO TODAY.

A SECOND SLIGHT RISK AREA WAS INTRODUCED OVER AZ/NV/CA IN
ANTICIPATION OF AN EVENT FRIDAY AFTERNOON. BOTH THE GFS AND ECMWF
FORECAST A MODERATELY BROAD PLUME OF GREATER PRECIPITABLE
WATER...ABOVE 1.5 INCHES...TO NOSE NORTHWARD INTO THE LOW DESERTS
AND REACHING SOME OF THE MOUNTAINOUS TERRAIN BETWEEN
FLAGSTAFF...VEGAS...AND SOUTHEAST CA. ASIDE FROM INCREASED
CONVECTIVE COVERAGE FRIDAY AFTERNOON...SOME SLIGHT ENHANCEMENT OF
SOUTHERLY INFLOW IS FORECAST NEAR CLOUD BASE...PERHAPS AIDING
UPSCALE GROWTH OF SOUTHWARD PROPAGATING STORM CLUSTERS.


...SD/MN/IA/NEB...

WHILE EARLIER MCS ACTIVITY OVER IA CONTINUES TO WEAKEN..LATEST
HRRR GUIDANCE CONTINUES TO SUPPORT SOME OF THE HI RES GUIDANCE OF
A REDEVELOPMENT OF STG TSTM ACTIVITY OVER PARTS OF SD/NEB/MN/IA
AFTER MIDNIGHT...ESPECIALLY OVER MN/IA WHERE STORMS MAY BECOME
MORE ALIGNED NW/SE WITH THE UPR FLOW SETTING UP POTNL FOR SOME
TRAINING BANDS LATER TONIGHT.  THIS ACTIVITY IS EXPECTED TO EXPAND
OVERNIGHT IN STRENTHENING 85H SWLY JET AND DEEPENING MSTR
SUPPORTING STG MSTR FLUX VALUES ACRS THE AREA AHEAD OF WARM FRONT.
 STILL NOT CLEAR AT THIS POINT WHERE THE MORE ORGANIZED ACTIVITY
MAY DVLP WITH HRRR MODEL RUNS ALONG WITH 12Z HI RES GUID SHOWING
RATHER LARGE MODEL SPREAD..BUT WILL CONTINUE TO MONITOR AREA FOR
POSSIBLE UPGRADE TO SLIGHT RISK.

SULLIVAN/BURKE