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Excessive Rainfall Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0816Z Feb 25, 2018)
 
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Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
316 AM EST Sun Feb 25 2018

VALID 12Z Sun Feb 25 2018 - 12Z Mon Feb 26 2018


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 SSE 7R3 KCRH 10 SW KGVX 15 S PKV PKV 15 W CXO 30 ENE LFK
30 ESE BQP 25 ESE 1M4 15 NE CHA 10 E TYS 40 NW AVL 20 SE 1A5
15 NW OPN 35 W OZR 25 N 1B7 30 SSE 7R3.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 WSW MSY 10 NNE KVNP KCMB 15 NNE KGVX 20 SE BYY BYY
20 ENE 5R5 10 N IAH 25 NW POE 20 NNE HEZ 35 W MEI 40 E NMM
60 ESE NMM 50 W GZH 25 N MOB 10 NNE BIX 10 WSW MSY.


Upper coast of TX---lower MS valley---central Gulf coast into the
southern Appalachians


The excessive rainfall threat along and ahead of the surface
frontal boundary pushing eastward from the OH/TN valleys will
continue to decrease prior to the beginning of the upcoming day 1
period.  The focus for heavy rains during the upcoming day 1
period will be shifting farther to the south and west from the
upper coast of TX---eastward across the lower MS valley/central
gulf coastal region into the southern Appalachians.  The western
extent of the surface front pushing eastward through the northeast
this period is expected to be much slower moving---becoming nearly
stationary during Sunday along the western to central Gulf Coast
into the southeast as it becomes aligned parallel to the southwest
mid to upper level flow.  There is the potential for additional
convection in the vicinity of this front which will remain in a
favorable right entrance region of the upper jet and in an axis of
above average pw values---1.5-2.0+ standard deviations above the
mean.  There are differences with respect to the axis of the
heaviest precip in the vicinity of the front.  The hi res models
are on the farther south end of the guidance---with non hi res
guidance generally supporting a farther northward max axis.  The
day 1 WPC QPF leaned toward the farther south
solutions---depicting a heavy precip axis from the upper coast of
TX---across central to southern LA---central to southern
MS---central to southern AL and into the southern Appalachians of
northwest GA and far southwest NC.  This expected QPF axis is
across areas that have not received as heavy amounts of rain as
points farther north---with FFG values relatively high. 
Subsequently---believe the excessive rainfall threat will be lower
compared to previous days for points farther north.  The broad
slight risk from previous forecasts that stretched across large
portions of the central Gulf Coast was suppressed to the south and
decreased in size---aligned with the expected max axis from the
upper coast of TX into central to southern LA and southern MS. 
The marginal risk area was maintained northeastward into the
southern Appalachians.

Oravec