Quantitative Precipitation Forecast
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FOUS30 KWBC 251512
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1011 AM EST Sun Feb 25 2018

VALID 15Z Sun Feb 25 2018 - 12Z Mon Feb 26 2018


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 S BFM 20 E NBG 10 S 7R4 30 NE GLS 20 E 5R5 15 S 3T5 20 E AUS
15 W LHB 15 S JSO 25 SSW SHV 20 WNW MLU 30 SSW GWO 25 ESE 1M4
15 NE CHA 10 E TYS 40 NW AVL 20 SE 1A5 15 NW OPN 35 W OZR
15 S BFM.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 ESE ACP 15 N BPT 10 SSE DWH 15 W CXO 10 NNE UTS 10 SSW OCH
40 ENE OCH 25 NNE IER 10 SSW MLU 20 NW TVR 15 N HKS 25 SSE JAN
20 W MCB 30 ESE ACP.


Water vapor imagery shows a wave moving northeast across TX this
morning, with the area also continuing to see upper level
divergence in the right entrance region of the jet to the north.
850 mb moisture transport has increased ahead of this wave...and
while not extreme in nature...has been strong enough to result in
an uptick in convective activity over southeast TX. This
convection is forming in an area where 850 mb moisture convergence
and roughly 500-1000 j/kg of elevated CAPE intersect. The axis of
850 mb moisture convergence should persist through the day along a
corridor from southeast TX into central and northern LA and
portions of southern and central MS. Recent RAP runs suggest that
this stronger activity over southeast TX should tend to move out
of the better instability as it moves east into far east TX and
LA. This may tend to result in a decrease in intensity and rates
as it moves into this more stable airmass. However a few hundred
j/kg of cape should still exist...which combined with near record
pwats...will still support some locally heavy rates. Soil
conditions also become more saturated across far east TX into
central and northern LA. Thus at least some flash flood threat
exists into the early afternoon hours with this activity over TX/LA

Showers and embedded thunderstorms may tend to persist through the
day and into this evening over portions of far east TX into LA.
However by later today elevated instability should be even
less...resulting in the likelihood of lower rainfall rates than
the morning and early afternoon storms. Still given soil
conditions...an additional flood risk may persist.

With this update we went ahead and shifted the slight risk a bit
northward across southeast TX into LA. This coincides with the
axis depicted by the new 12z high res guidance...while also
agreeing with recent radar trends...and encompassing an area that
has been quite wet over the past week. Given recent radar/model
trends and soil conditions think the slight risk further south
along the Gulf Coast can be made a marginal. The marginal risk
will be maintained across portions of MS/AL and into the southern
Appalachians. Some higher rates are possible in southern MS where
some instability is progged...however given drier antecedent
conditions here...think a marginal should be fine for now. Further
north and east still looking at 1-2" or so of rain...however drier
antecedent conditions and lower rates should keep the threat
marginal at best.

Chenard




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