Quantitative Precipitation Forecast
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FOUS30 KWBC 162232
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
632 PM EDT Wed May 16 2018

Valid 2232Z Wed May 16 2018 - 12Z Thu May 17 2018


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
55 SW RDM 50 NW 5J0 15 ENE ALW 20 ENE DEW 20 NE CWJR 15 N CXBR
10 S CPFI 20 SSW CWOE 35 ENE GFA 15 WSW BTM 20 E ONO 40 SSW REO
20 NE LOL 15 SSE NFL 40 ESE TVL 15 NW TVL 40 N BLU 10 N RDD
30 ENE O87 25 NNW ACV 45 WSW SXT 55 SW RDM.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
75 SSW PAM 20 ENE KVOA 40 N KVKY 30 SE HBG 35 N PIB 20 SE TVR
20 SSW MLU 30 NE BAD 20 SSW DEQ 15 SSW DEQ 35 WSW RKR 10 ESE TQH
ASG 25 SW FLP 10 NE SRC 20 W AWM 20 ESE NQA 50 NNW MSL 40 SW MQY
15 SW GLW 15 SE KI68 30 SSW HLG 20 SSW AOO MUI 15 NW RDG
10 SW BDR 45 SSE BID 120 SSE FOK 55 ESE WWD 20 E FYJ RDU
10 ENE OGB SSI 20 ESE COF 15 ENE PBI 25 ENE HST 25 SSW HST
25 SW HST 45 ESE APF 30 ENE PGD 20 NNW GIF 25 NNW BKV 65 SSW CTY.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
GMU 15 ESE ATL 15 SW FTY 30 NNW GVL 25 SSE TRI 15 ESE TNB GMU.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NNW SHD 10 SSE 48I 25 WNW 48I 15 S PKB 25 ENE PKB MGW
20 ENE CBE 20 ESE THV 15 NNW NEL 35 E MJX 50 ESE ACY 40 ESE WWD
10 NW OXB 10 WNW FYJ 25 E FVX 20 N FVX 15 SSE CHO 10 NNE CHO
25 NNW SHD.


2100 UTC Update..

Quite an expansive area of what would be considered a "marginal"
risk across the Deep South into the Southeast and mid Atlantic
region. Outside of a portion of the mid Atlantic region
(WV-MD-northern/central VA), the 0-6km bulk shear values are less
than 25 kts. Therefore, continue to expect mainly pulse-type
convection with highly-efficient rainfall rates given the deep
subtropical moisture feed (PW anomalies 2-3 standard deviations
above normal). Otherwise, the forecast thinking noted in the
discussion below remains relevant going through the evening.

Hurley


...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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