Quantitative Precipitation Forecast
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000
FOUS30 KWBC 180100
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
900 PM EDT Thu May 17 2018

Valid 01Z Fri May 18 2018 - 12Z Fri May 18 2018


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 ESE RXE 15 ESE JAC 15 NW BPI 35 NE LGU 25 NNE ENV 20 E B23
35 WSW AWH 10 NW TWF 40 NNE BYI 15 ESE RXE.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 E IEN 20 N BFF 45 NE SIB 40 NE IKA 40 SE DIK 10 SE JMS
15 SW FSE 15 SW DTL 15 SE KGWR 50 WSW ABR 25 NW ICR 35 E IEN.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SW RPH 20 SSW SWW 40 SSW LBB 35 W PVW 20 SSE AMA 15 SSE FDR
25 SW RPH.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 E CWJI 35 ESE CWAQ 15 N SDY 15 ENE GDV 45 E JDN 15 W JDN
55 NNE BIL 10 ENE BIL 10 W BIL LWT 40 ESE HVR 45 NE CWVN.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 SW JKA 35 SSE PQL GPT 20 N HSA 20 WSW PIB 25 N PIB
30 NNE PIB 30 SE NMM 45 NNW GZH 20 NE GZH 10 NW CEW 45 SSE NPA.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 E RSW 30 NNE PGD 10 E GIF 40 WSW VRB 45 WNW PBI 30 WNW OPF
35 W TMB 30 E APF 15 E RSW.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
105 SE MRH 95 ESE SUT 35 SE SUT ILM 10 NNE ILM 15 SE ISO
20 W EDE 10 WNW RZZ BUY SVH GYH 10 W GVL 10 WSW MGE 25 ENE OPN
30 E MLJ 30 ENE AGS 10 NNE MMT 25 SW FLO 35 N CHS 15 NNE NBC
15 NE LHW 25 WSW BQK 25 NW VQQ 40 W VQQ 30 ENE 40J VAD 35 NE MGR
25 N ABY 35 SE LSF 25 SSW LSF 25 SSW AUO ALX 25 W ANB 25 SE 3A1
10 E 1M4 40 SW TUP 35 SSW GWO 25 NNE GLH 35 SE M19 40 ENE UNO
10 NW SAR 15 S MVN 20 S EHR GLW 15 ENE K8A3 20 E CSV 40 ENE CHA
10 N 1A5 15 SSE VJI 10 NNE BLF 15 NNW EKN 25 NW MRB 95 SSE BID.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 WSW PHP 20 NNW CDR 50 WNW CDR 40 NW RCA 25 ENE HEI 30 W K2D5
40 NW ABR 35 SSW MBG 20 WSW PHP.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
115 ESE OXB 25 SE MFV PTB 10 S MTV MWK 15 SSE LWB 15 ESE W99
15 NNE DOV 75 ESE MJX.


Day 1...

...Mid-Atlantic States...

See MPD 0161 issued near 01Z for updated information as of mid
evening. Ongoing rainfall with some convective enhancement and
some upslope enhancement is cause for concern in the mountainous
terrain of southwest Virginia. Overnight continued synoptic ascent
should support additional rainfall and perhaps embedded thunder in
the elevated frontal zone farther north. This activity may overlap
with the now saturated portions of northern Virginia, D.C.,
central to southern Maryland. WPC therefore maintained a Slight
Risk of excessive rainfall in this area, the only limiting factor
being the relative lack of instability overnight.


...Southern / Eastern U.S...

Here beneath a broad upper low there were very few pockets of
instability remaining as of mid evening. A few cell mergers or
repeat cells could lead to short-lived and isolated bouts of high
water and/or flash flooding, mainly near the Ohio/Mississippi
River confluence...and down near the central Gulf Coast where
northwesterly flow has led to a rapid succession of two lines of
convection over the same area.

Although as of 01Z most activity in the Southeast was waning,
there is strong model signal for some precipitation streamers to
come ashore into eastern North Carolina overnight, and given the
quality of available moisture some isolated heavy rain totals
owing to shallow, warm-rain-process convection could occur.


...Northern Plains / Eastern Montana...

A sliver of Slight Risk remains here to cover ongoing activity
that was widespread and slow moving. With difluent flow aloft and
growing cold pools, the instability should gradually be consumed
through the late evening hours. Slow cell motions, some mergers,
and mid-range FFG lead to the possibility of multiple locations
exceeding FFG. The event will eventually run out of real estate as
low level moisture and CAPE values drop off over eastern South
Dakota.

In Montana a small Marginal Risk remains in place near a warm
front where easterly low level flow will contribute to very slow
cell motions until instability diminishes / is consumed.


...Great Basin / Eastern Snake River Valley...

A convective event in the eastern Snake River Valley this evening
had tended toward severe mode, but cells were aligned such that
mergers and brief training could lead to isolated heavy rain
through about 02Z.


...Texas...

Clusters of storms had formed in the post-frontal upslope flow
over the Texas Panhandle and TX South Plains. Model forecasts had
performed well as the more organized and lasting activity took
hold over western north Texas, wedged between Childress and
Lubbock, and heading downstream to the east. This area has lower
FFG owing to recent rainfall. Overall the convective event is
expected to be short-lived as storms outdistance the more
supportive upper flow environment to the west, but there is a
Marginal Risk of excessive rainfall through the late evening.

Burke
$$





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