Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 190815
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
315 AM EST Mon Feb 19 2018

LATEST UPDATE...
Synopsis/Short Term/Long Term

.SYNOPSIS...
Issued at 254 AM EST Mon Feb 19 2018

A low pressure system developing in eastern Colorado will track
northeast through the western Great Lakes Region through Tuesday.
Rain showers will be on the increase across the area along with a
few thunderstorms. The rainfall will be heavy at times which could
lead to some flooding. A large area of high pressure will build in
from the west on Wednesday...drying the airmass out here in
Michigan.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 254 AM EST Mon Feb 19 2018

Overall the pattern has not changed much...still supportive of
several rounds of heavy rain through Tuesday night. Thus no major
changes to the forecast at this time. Will keep the flood watch as
is.

Elevated showers and thunderstorms were tracking through Illinois
and Indiana. These may clip the far southern zones...where I did
add the potential for a morning storm. Overall not much QPF is
forecasted for the morning. Morning temperatures were starting
out near freezing for interior parts of Lower MI...so will
maintain a low risk for freezing rain.

As the Gulf moisture continues to stream this afternoon and
evening...the showers will pick up in coverage and intensity.
Elevated instability will be around...so will maintain the risk
for a few thunderstorms. Fog should be on the increase as
well...especially tonight.

For Tuesday into Tuesday night...very high pwat values around the
region support rain showers heavy at times. The presence of elevated
instability suggests a few storms as well. The deep southwest
flow does support some training of the showers and storms. Where
that does set up will likely be where the higher impacts occur.
Highest QPF values are forecasted to be south of a Muskegon to
Alma line. Given the convective nature...there is still
uncertainty on the exact amount and location of the heaviest
rain. The highly anomalous moist pattern is still supportive of a
flood watch for the entire region.

.LONG TERM...(Wednesday night through Sunday)
Issued at 254 AM EST Mon Feb 19 2018

High pressure will build into the northern Great Lakes region
Wednesday night through Thursday and bring fair wx with near normal
temperatures. A low pressure system moving will move northeast and
bring potential for a mix of light pcpn Thursday night into Friday
before thermal profiles moderate sufficiently enough for pcpn to
transition to plain rain showers later in the day Friday.

A gradual moderating trend of temperatures is forecast Friday
through the weekend and temps by the weekend will average around 10
to 15 degrees above normal for this time of year. High temperatures
will reach well into the 40`s this weekend. Another high pressure
ridge will build in to briefly bring fair weather before the next
system brings potential for another mixed pcpn event late Saturday
into Sunday.


&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1115 PM EST Sun Feb 18 2018

VFR conditions will continue overnight before gradually
deteriorating to MVFR then IFR Monday morning as low clouds move
in and patchy fog develops. Conditions will deteriorate further
to LIFR Monday afternoon through Monday evening as very low cigs
develop along with areas of denser fog.

In addition scattered showers will develop and there is also
potential for some thunderstorms to develop by late afternoon
through the evening. Conditions should remain predominantly LIFR
through at least 06Z Tue.


&&

.HYDROLOGY...
Issued at 330 PM EST Sun Feb 18 2018

As a strong area of high pressure sets up over the Southeast U.S., a
solid stream of gulf moisture is expected to flow northward into the
Great Lakes. Guidance continues to suggest rainfall from Monday
through Wednesday with periods of heavy rain possible.

Widespread rainfall amounts ranging from 1 to 3 inches are expected,
with locally with excessive amounts of over 3 inches, especially
from Southwest Michigan to Saginaw Bay. Coupled with recent
snowmelt, a frozen ground, and continued high river levels, rainfall
will result in bankfull streams and rivers. Some locations are
looking at minor flooding, especially those immediately near and
adjacent to rivers.

A positive light in all of this is that temperatures in the 50s and
60s will reduce the presence of ice on rivers. High water flows are
likely to flush waterways, freeing up streams and preventing
immediate concern for ice jams, if temperatures were to return to
well below freezing territory in the future.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Flood Watch from noon EST today through Wednesday afternoon for
     MIZ037>040-043>046-050>052-056>059-064>067-071>074.

LM...None.
&&

$$

SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...Laurens
AVIATION...Laurens
HYDROLOGY...JAM


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