Quantitative Precipitation Forecast
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000
FOUS30 KWBC 200107
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
906 PM EDT Sat May 19 2018

Valid 01Z Sun May 20 2018 - 12Z Sun May 20 2018


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
60 WSW DRT 35 SSW E29 30 ESE SJT 50 NNE JCT 15 NW SKF
15 WSW COT 65 SSW MMPG.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
WWR 30 NE EWK 20 NE LXT 30 ESE VIH 40 ENE UNO 25 SE FYV
10 NNE AQR 15 S MWL 40 SSW SWW 35 NNW ODO 40 SE CVN 15 SE AMA
WWR.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 SSW BKW 15 NNE 48I 25 SW 2G4 20 ESE W99 30 NW FVX 10 SW DAN
EXX 10 NNW FQD 35 SSW TRI 15 S 1A6 15 S LNP 15 SSW BKW.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
65 SSE CHS 20 S CHS 35 NNE CHS 25 ENE FLO CTZ OAJ 15 SSE NCA
20 SSE NCA 30 ESE SUT 70 SSE MYR.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
60 SE HST 55 SSE HST 35 NNE MTH 50 E RSW 15 NNW VRB 60 E COF
110 ENE VRB 80 NNE MYGF.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 SE HST 30 S HST 15 SW HST 25 WNW OPF 30 WNW PBI 10 WNW SUA
15 E FPR 45 ENE SUA.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
INT 10 W MRN 15 WSW TNB 15 S MKJ PSK 15 NE HSP 15 SW SHD
10 NNE LYH INT.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 ENE PVW 15 NNE HBR 25 ESE AAO 40 W AIZ 15 SE BVO 35 WNW GLE
20 W RPH 35 NW BPG 30 SW LBB 40 ENE PVW.


...Southern Plains...

See MPD 0173 and any future MPDs for details. There is a Slight
Risk of excessive rainfall which has been repositioned a bit over
western north Texas, and then stretched up through central to
northeast Oklahoma to connect with an area of lowered Flash Flood
Guidance in parts of KS/MO. This entire region was located along a
surface frontal zone. A broadly supportive synoptic flow regime,
along with moderate to strong CAPE - noting little CINH on the 00Z
KOUN sounding - and enhanced convergence with the low level
jet...should lead to clusters of strong storms with locally heavy
rain overnight. Some recent HRRR runs and an average of hi-res
runs, such as the HREF Mean, look close to reality with respect to
QPF.

Meanwhile, a separate convective cluster near the Rio Grande may
raise some local concern for heavy rainfall if outflow can become
established, leading to a few repeat cells over a small area.

...NC/VA Appalachians and Piedmont...

The 00Z KRNK sounding was fairly unstable while also predictably
moist given the ongoing regime. At 01Z low-topped convection was
likely producing efficient rainfall / warm rain process / in spite
of its relative lack of depth. This combined with exceptionally
wet antecedent conditions will support a continuation of Slight
Risk for a few more hours until the showers subside with the loss
of heating and passage of an upper level shortwave trough. Any
additional rain could lead to renewed flash flooding and
associated impacts.


...Florida...

Low level southeasterlies are forecast to increase in strength
overnight, with potential to carry increasingly unstable tropical
air onshore into southeast Florida and up along the east coast of
Florida. Convergence downwind of the Bahamas along with a weakly
difluent upper level flow pattern would suggest that some
organized streamers of convection and heavy rainfall could occur
overnight, though the hi-res model signal is somewhat variable as
to whether this occurs inland or just offshore. Given the
uncertainty, we saw no reason to modify the existing Slight Risk.

...Eastern Carolinas...

Here we downgraded to a small Marginal Risk area. The daytime
convective streamers had not been too efficient with rainfall.
Additional activity is expected overnight, and owing to tropical
origins / deep moist profiles, locally heavy rain could be the
result, per some of the hi-res guidance. High FFG values, however,
will keep the probability of exceedance low.

Burke
$$





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