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Excessive Rainfall Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0101Z Sep 29, 2014)
 
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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
901 PM EDT SUN SEP 28 2014

...VALID 03Z MON SEP 29 2014 - 00Z TUE SEP 30 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 SW GNV 35 SSW CTY 25 WSW 40J 20 S AAF 30 WSW AAF 20 S PAM
20 WSW PFN HRT CEW 20 S LSF 20 ENE MLJ 30 ENE AGS 30 SE SSC
40 SSW MYR 20 SSE HXD 15 SSE SSI 10 SW GNV.


SOUTHEAST
~~~~~~~~~
A DIFFUSE UPPER LEVEL TROUGH WILL PUSH SLOWLY EAST OF THE
MISSISSIPPI DURING THE PERIOD, PROVIDING DIFFLUENCE ALOFT AND
CAUSING A POCKET ENHANCED LOW- TO MID-LEVEL FRONTOGENESIS NEAR A
STATIONARY FRONT CLOSE TO THE SOUTHEAST COAST AND SOUTHERN GA. IN
TERMS OF THE QPF DETAILS...MODEL DIFFERENCES REMAIN...WITH
SIGNIFICANT SPREAD IN TERMS OF HOW FAR NORTH AND NORTHWEST
MEASURABLE RAINFALL WILL GET THROUGH 00Z TUE.  SO FAR, THE MORE
NORTH AND NORTHWESTERLY GUIDANCE HAS NOT BEEN VERIFYING.  THE 00Z
WPC QPF TRENDED BACK TOWARDS A MORE COASTAL SOLUTION AS THE 12Z
GFS/18Z NAM/RECENT RAP RUNS SUGGEST THAT THE 850 HPA REFLECTION OF
THE FRONTAL ZONE MAKES VERY LITTLE INROADS INTO GEORGIA OVERNIGHT.
 THE 12Z SSEO MEAN IS ALONG THE LINES OF THE 00Z WPC QPF.  SOME
CIN IS EXPECTED ALONG THE SURFACE BOUNDARY WHICH WOULD CAUSE
CONVECTION OVERNIGHT TO BECOME MORE ELEVATED IN THE 03-15Z TIME
FRAME.  HOWEVER, A CURRENT CONVECTIVE COMPLEX IN THE NORTHEAST
GULF OF MEXICO HAS INTERCEPTED INFLOW WHICH WOULD OTHERWISE BE
AIMED FOR THE EASTERN FL PANHANDLE/SOUTHERNMOST GA.  MUCAPES OF
1000+ J/KG WILL BE SUFFICIENT IN GENERATING AREAS OF HEAVY
RAINFALL (POTENTIALLY EXCESSIVE RAINFALL RATES) AS FAR NORTH AS
THE FL/GA BORDER GIVEN THE THERMODYNAMIC SETUP WITH PRECIPITABLE
WATER VALUES (PWS) OF ~2.25" AND WET BULB ZERO LEVELS ABOVE 14000
FT (FAVORING OPTIMAL PRECIPITATION EFFICIENCY AND WARM RAIN
PROCESSES).  THE LOW-LEVEL INFLOW WILL REMAIN FAIRLY WEAK (~15-20
KTS), SO DO NOT ANTICIPATE THE DEVELOPMENT OF A CONVECTIVE COMPLEX
ACROSS THE REGION, THOUGH TRAINING QUASI-LINEAR BANDS OF
CONVECTION ARE POSSIBLE.  ACROSS SOUTHERN GA, THE HIGHER
RESOLUTION GUIDANCE GENERALLY ADVERTISES LOCALIZED AMOUNTS OF 6-9"
THROUGH MONDAY EVENING (WITH THE HIGH-BIASED 18Z NAM CONEST
SHOWING MAXIMA NEAR 12").  A SLIGHT RISK OF EXCESSIVE RAINFALL WAS
INDICATED IN THIS REGION DUE TO THE LINGERING UNCERTAINTY IN
PRECIPITATION PLACEMENT AND THE ANTICIPATED LIMITED SCOPE OF
CONVECTIVE ORGANIZATION.

SOUTHEAST WYOMING
~~~~~~~~~~~~~~~~~
THE ANOMALOUS DEEP UPPER TROUGH/CLOSED LOW ACROSS THE LOWER GREAT
BASIN WILL WEAKEN AS IT SHIFTS SLIGHTLY EASTWARD...MAINTAINING
FAVORABLE DYNAMIC SUPPORT (UPPER DIFFLUENCE/DIVERGENCE) VIA THE
WARM CONVEYOR BELT (WCB) ALONG WITH THE MOIST...S/SE LOW-LEVEL
FLOW AND UPSLOPE ENHANCEMENT ACROSS THE CENTRAL ROCKIES.  RECENT
RAP RUNS ADVERTISE SOME INSTABILITY (MUCAPES ~500 J/KG) WITHIN A
REGION OF FAVORABLE MOISTURE PROFILES (PWS 2-3 STANDARD DEVIATIONS
ABOVE THE NORM FOR LATE SEPTEMBER).  THE MOST SIGNIFICANT PROBLEMS
IN REGARDS TO DEPICTING A SLIGHT RISK AREA ARE THE LIMITED
MOISTURE (BARELY 1" PWS) AND THE FORWARD PROPAGATION TO THE NORTH
ANY ORGANIZED CONVECTION WOULD HAVE TO FOLLOW WITHIN THIS FAIRLY
DRY (FOR FLASH FLOOD PURPOSES IN THE HIGH PLAINS) AIRMASS.

ROTH