Quantitative Precipitation Forecast
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
000
FOUS30 KWBC 230045
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
845 PM EDT Tue May 22 2018

Valid 01Z Wed May 23 2018 - 12Z Wed May 23 2018


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 NE TYS 15 SSE TRI 10 SSW TNB MRN 15 SE GSP 25 N JYL 15 W LHW
DQH 15 NNW 11J 10 E JKA 20 N BIX 30 NE NMM 25 NNW 4A9 10 NE TYS.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 N HEI 25 N BIS 25 SSE JMS 10 WNW ETH 10 NE MKT 20 SW DEH
10 WSW VTI 15 SW EBS 20 S FSD 20 SSW HON 10 ENE PIR 30 NNE IEN
25 NNW IBM 10 SE VDW 35 N ARL 30 SW PAT 20 SSE BIT 25 NW CMS
25 E U78 15 WNW PIH 40 SE MUO 15 WNW MUO 25 SW SNT 50 ESE LLJ
25 E S14 15 SSW BZN 20 SSE 3HT 60 SW MLS 60 S MLS 30 W 2WX
30 N HEI.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 E EZF 10 E OXB 35 E WAL LFI 25 S LYH 30 NW FVX 20 E EZF.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 SE RWF 20 SSW AUM 30 WNW ALO 15 W CAV 15 ESE SHL 20 W PQN
15 N BKX 15 SE RWF.


...01z Update...

Given the 12z model trends and recent runs of the operational and
experimental HRRR, did extend the Slight risk a little further to
the east across northern Iowa.  But overall the outlook across the
northern and central Rockies to the upper Midwest remains
relatively unchanged from the previous.  See previous the
discussion for further details.

Across the Ohio valley, Mid-Atlantic and Southeast, pared away
areas of the previous marginal risks where the heavy rainfall
threat has waned.

Across the Southeast, individual cell motions have been fairly
progressive as they move in the vicinity of a weak, slow-moving
low centered over Alabama.  However, merging cells have helped
produce some locally heavy totals.  With the loss of daytime
heating, expect convection to wane as the evening continues.

Further to the north, leading round of convection will continue to
push south and east across central and southeast Virginia.
Training cells along the trailing edge may continue to produce
heavy rainfall threat and isolated flash flooding concern across
south central to southeast Virginia over the next few hours.

Expect convection to continue to fire further to the northwest
ahead of the synoptic scale cold front.  Here too, expect storms
to be generally progressive.  However, training line segments may
produce a locally heavy rainfall and isolated flash flooding
threat across portions of the Ohio valley into the central
Appalachians this evening.

Pereira

Previous discussion...

...SD/MN/IA border junction...
Tonight appears to be a good setup for an axis of elevated
convection across portions eastern SD into southwest MN and
northwest IA, though not terribly so as MUCAPE values are expected
to start in the 1500-2000 J/kg range and the best 850 hPa wind
convergence/confluence appears to be near the SD/IA border.  The
850 mb moisture transport increases and persists through the night
downwind of the instability pool.  Storm motion vectors are at a
right angle to the low-level inflow expected, suggesting that
storms could regenerate and train for a period from west-northwest
to east-southeast. Still a good amount of uncertainty with model
placement, though there is a strong enough signal for 3-5" totals
in the mesoscale guidance to elevate to a slight risk.

...Central and Northern Rockies...
The approach of the mid/upper level trough will increase
convective chances across the Rockies into the Plains. Upper level
flow will become very divergent over WY by this afternoon, while
the low-level flow is upslope across southern MT.  Across ID,
activity could be enhanced more than usual near the Snake River
valley.  Combined with increasing instability,and the presence of
a low level boundary, scattered convective development is
expected. Instability should be high enough to fully take
advantage of the anomalous PWATs and produce some locally intense
rates.  Storms will generally be progressive in nature off to the
north; multiple rounds of storms are possible given the favorable
synoptic environment.  At least a localized flash flood risk
exists across WY into southern MT. Eventually these cells should
take a turn to the right and move into the northern Plains, with
one or more convective clusters likely. Low confidence on how this
evolves, but locally heavy rains are possible into SD/ND as
convection moves across.  Southwest SD could be interesting as
storms that initiate off the Black Hills could merge with
convection moving northeast out of WY/NE. Should this happen a
more focused flash flood risk could develop.

Roth/Chenard
$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.