Quantitative Precipitation Forecast
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143
FOUS30 KWBC 220828
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
327 AM EST Thu Feb 22 2018

VALID 12Z Thu Feb 22 2018 - 12Z Fri Feb 23 2018

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 N 48I 30 N MDQ 10 NW POE 25 SSE 11R AUS RBD 25 ESE FYV
20 NNE BMG 10 WSW BJJ 10 W YNG DUJ 20 S FIG 25 WNW HGR
35 NNE SHD 15 N 48I.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 N POF 25 N HNB 15 NW CVG 25 N FFT 25 N GLW 40 N TUP
25 ESE BQP 20 S MLU UTS 10 NNW CLL 25 ESE ACT SLR 35 NNW MWT
35 N POF.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 NW M19 CGI 15 SE CUL 10 E EVV 25 SSW OWB 40 E MKL 30 SE OLV
20 NE BQP 30 E BAD 10 SW 4F4 30 E DEQ 10 NW M19.


Northeast TX---lower MS valley---lower TN valley---OH valley

A broad slight and moderate risk areas were maintained for the
upcoming forecast period for what will likely be another round of
widespread heavy to excessive precipitation from northeast
TX---into portions of the lower MS valley---lower TN valley and
into the OH valley.  There is expected to be no big changes to the
broad southwest mid to upper level flow from the southern plains
northeastward into the lower to mid MS valley---Great Lakes and
into the northeast this period.  PW values in this southwest mid
to upper level flow will remain highly anomalous with values 3-4+
standard deviations above the mean.  The current axis of heavy
precip from northeast TX into the lower MS valley---lower TN
valley into the OH valley is expected to weaken after 1200
Thursday.    Precip is then expected to refocus late this
afternoon into Thursday night-early Friday morning in an axis
farther to the northwest from the current early morning activity
as low level flow re-strengthens out of the south and into the
frontal boundary stretching northeast from northeast TX across the
lower MS valley and into the OH valley.  Differences in model QPFs
revolve around the latitude of this next max axis.  Day 1 QPF
leaned toward the solutions that were farther to the south and
east---trending approx 40-60nm farther to the southeast from the
previous forecast.  There is a lot of run to run variability with
the QPF details at the shorter forecast intervals.  While the
second round of precip will likely overrun the above mentioned
frontal boundary fairly far to the north---WPC continued to favor
the max QPF axis solutions that were farther to the southeast
closer to the greater instability near the frontal boundary.
There will likely be another round of potentially training
convection between 0000-1200 utc Friday from northeast
TX---northeastward into AR---northwest MS---western TN---far
southeast MO into the lower OH valley as the low level flow
becomes focused out of the southwest in a region of favorable
right entrance region jet dynamics.  While the next precip event
is expected to be farther to the northwest than the current
activity---there will be potential for overlap of the two heavy
events across portions of northeast TX---northern LA---southern
AR..nw MS---western TN---far southeast MO into western KY.

Oravec

$$





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