Quantitative Precipitation Forecast
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468
FOUS30 KWBC 161459
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1058 AM EDT Wed May 16 2018

Valid 15Z Wed May 16 2018 - 12Z Thu May 17 2018


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 E MTH 20 SSW HST 30 W FXE 20 WSW SUA 20 E FPR 65 ENE SUA.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 WSW ONO 65 ENE LKV 20 ESE LOL 35 WSW NFL TVL 40 N BLU
10 N RDD 30 ENE O87 25 NNW ACV 45 WSW SXT 50 SW RDM 50 NW 5J0
10 SSW ALW 25 WNW PUW 15 W SZT CWJR 10 S CYXC 20 WSW CWGM
45 SSE GPI 20 N MSO 15 SW MSO 40 ENE P69 30 SE P69 30 NNE MYL
35 WSW ONO.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
105 SSE KIPN 80 E KVOA 20 WNW OZR 20 NW OZR 20 ENE RMG
35 SW TRI 20 NNW 6V3 10 S CRW 10 SSW UNI 25 NW UNI 20 S ZZV
20 SSW AOO MUI 15 NW RDG 10 SW BDR 40 SSE MTP 80 ESE MJX
80 SE MJX 25 SSE WAL 25 NNE FFA 10 E HSE 30 SSE MRH 10 W EYF
20 SSW OGB 10 NNW NRB 15 SSE VQQ 30 NW BKV 65 W PIE 145 SW SRQ.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 SE GYH 20 NE AHN 10 SE ATL 20 W CCO 47A 15 WNW 1A5 35 S TRI
15 ESE TNB 10 SE GYH.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 SE 2G4 10 SE THV 15 NNW NEL 30 E MJX 40 SE MJX 45 ESE ACY
30 SSE WWD 10 NE SBY RIC 20 NNW PTB 15 N FVX 15 SSE CHO
10 NNE CHO 25 NW SHD 10 ESE 48I 20 W 48I 25 SSE PKB 10 E PKB
30 NNW CKB 10 SE 2G4.


1500 UTC update

Across the Mid-Atlantic---the slight risk area was extended to the
west from the previous issuance into northwest VA and northeast WV
to cover the lower ffg values across northeast WV into northwest
VA. The latest neighborhood probabilities from the hi res
guidance---arw---nmmb and especially the nam conest show
significant potential for precipitation exceeding the lowered ffg
values across these areas.

Across the Southern Appalachians---a slight risk area was
introduced from northeast Georgia into the Upstate of South
Carolina and western North Carolina.  Large sections of this area
have received heavy rains---3 to 5"+--- over the past 24 and have
the potential for additional heavy totals through the remainder of
the forecast period.  See WPC`s mesoscale precipitation
discussions #0153 and #0154 for additional information across
these areas.

Oravec

...Mid-Atlantic/Central and Southern Appalachians...

Southerly flow along the western periphery of the Bermuda high and
ahead of a weakening trough lifting out of the eastern Gulf of
Mexico will continue to channel deep moisture northward through
the region.  This moisture along with weak mid-level energy
lifting out ahead of the trough is expected to support some
orographically enhanced rainfall totals along the eastern slopes
of the southern to central Appalachians.  Guidance shows a fairly
good signal for south to north oriented training convection
producing some locally heavy amounts along the favored terrain
from far northeast Georgia and western North Carolina, to at least
as far north as southwest Virginia later today.  A Marginal risk
was maintained across a good portion of the Southeast into the
southern Mid-Atlantic and the Appalachians.  However, given the
amounts some of the hi-res guidance has been showing across
portions of the southern Appalachians, an increase to a Slight may
be required later today.

Further to the north, guidance shows a weak wave and associated
area of better organized precipitation moving east across the
northern Mid-Atlantic this morning into the afternoon.  Then as
energy from the south continues to lift out ahead of the southern
trough, additional weak surface to low level wave development will
enhance moisture convergence, which along with some support from
the right-entrance region of the upper jet, may generate
additional rounds of heavy rains later this afternoon and evening
from central and eastern Virginia to along a stationary boundary
draped across the northern Mid-Atlantic.  Given the recent heavy
rains that have occurred across portions of the region, and the
potential for addition heavy amounts, a Slight risk was maintained
from central and northern Virginia to central and southern New
Jersey.

...Southeast...

Onshore flow and low level convergence east of the surface wave
associated with the previously noted upper trough is expected to
support some moderate to heavy amounts across the eastern Florida
panhandle into southern Georgia today.  Heavy rainfall threat is
expected to wane by early Thu as the low weakens and lifts further
north.

...Pacific Northwest/Northern California/Great Basin/Northern
Rockies...

A weak mid-upper level low is forecast to drift northeast from the
northern Great Basin into the northern Rockies this today.
Guidance shows PWS increasing to around an inch (over 2 standard
deviations above normal) near the center.  This moisture along
with daytime heating is expected to support scattered storms with
the potential for locally heavy amounts from central Oregon
northeastward into western Montana.  Meanwhile, an upstream low is
forecast to move into northern California, fostering additional
precipitation further south and west across northern California
into northern Nevada late Wed into early Thu.

Pereira
$$





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