Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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167
FXUS63 KGRR 232029
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
329 PM EST Tue Jan 23 2018

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

.SYNOPSIS...
Issued at 329 PM EST Tue Jan 23 2018

Cooler air will rest over the region through mid week.  A few snow
showers will linger tonight through Wednesday night, especially near
Lake Michigan, but accumulations will be minimal.  By Thursday it
will be slightly warmer and quiet.  By Friday night a system will
bring some rain that should change to snow Sunday.

The Thursday warming trend will carry into the weekend with highs
climbing into the 45 to 50 degree range Friday and Saturday.  Cooler
weather then returns for early next week with highs returning to
around 30 Sunday through Tuesday.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 329 PM EST Tue Jan 23 2018

Rather quiet for much of the short term, although a couple of short
waves will bring periodic lake effect and/or weak synoptic snow.

Lingering light snow over the SE CWA will finally come to an end
later this evening.  No additional accums are expected.

Late tonight the lake effect should increase a bit.  A couple of
short waves come through, one around mid day Wed, and a second Wed
evening.  These should support weak lift and additional moisture
over the lake.  Air aloft finally become cold enough to expect snow
showers toward daybreak Wed. The snow will still be rather light
given that we just barely become cold enough. The short waves will
help keep the light snow going into Wednesday night.  The flow will
be northwest initially, becoming more westerly into Wed night.  All
told however, this event will be quite light, with accums likely
under an inch through the 24-30 hour period (late tonight through
Wed night). Will keep POPs low.

By Thursday warm advection will commence, bringing an end to any
lake effect.  An upper ridge moves from the Plains and into the
Western Great Lakes by Thursday night.  It will be a quiet and
warmer day with highs 35 to 40.  Low level moisture scours out very
slowly, so expect a partly sunny day.

.LONG TERM...(Friday through Tuesday)
Issued at 329 PM EST Tue Jan 23 2018

Overall, fairly quiet weather is expected in the long term. No major
systems affect our weather during the period. High temperatures in
the 40s on Friday and Saturday will cool into the 30s for Sunday
through Tuesday. The coldest days look to be Sunday and Monday when
the thermal trough is overhead. A progressive flow is in place at
500MB`s through the long term. A ridge is in place aloft over the
Great Lakes on Friday which transitions into troughing over the
weekend. Ridging returns by next Tuesday.

Differences remain in regard to the long term models with the
handling of a frontal passage on Saturday and whether or not we see
a low develop on the front. The GFS pushes mainly a dry frontal
passage through the area with no low developing along the boundary.
The ECMWF has more precipitation along the front, but does not
develop a low on the front until it is well east of us. The trend in
the ECMWF is for less in the way of precipitation and a quicker
frontal passage like the GFS. The Canadian is similar to the ECMWF
with precipitation quickly moving east. The trend seems to be the
way to go here which is less precipitation. The highest chances for
precip in the forecast is 40-50 percent Saturday night. As for
precip type, we look to be mainly rain from Friday night into
Saturday. Rain transitions to snow on Saturday night with some light
lake effect snow for Sunday into Monday. Tuesday looks dry with
ridging building back in.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1252 PM EST Tue Jan 23 2018

A band of snow is working through the TAF sites at 18z.
Visibilities are in the 3 to 5 mile range within the band with the
possibility of brief dips in visibility to around 1 mile. KLAN
stands the best chance at seeing the lowest visibilities. The snow
was weakening though and is shifting fairly rapidly to the east.
By 20z, the heavier snow is expected to be over with. During the
late afternoon hours, 20z to 00z, some flurries can be expected
but overall visibilities should be VFR.

Ceilings the next 24 hours look to be solidly in the 1000-2000ft
range. As we move into Wednesday, ceilings may try to rise into
the 2000-3000ft layer.

Winds will be gusty from the west-northwest (280-300 degrees)
this afternoon in the 15-30 knot range. Winds will diminish
considerably to below 10 knots this evening between 01z and 04z.

&&

.HYDROLOGY...
Issued at 329 PM EST Tue Jan 23 2018

It appears that rivers will not produce flooding of significance
beyond just low lying areas near the banks. Substantial
precipitation is not expected until at least this weekend, so water
will have time to move through the river system. Smaller and rapid
response rivers are near crest while main stem rivers will crest
over the next several days. The only wild card is the potential for
ice jams. These can cause quick fluctuations in river levels.
Observations from Comstock Park and Robinson Twp report a lot of
open water with some ice anchored and some ice broken up and
flowing. Ice jam potential seems not as high as it could be, but
will have to be monitored. Mild air will encourage ice melt again
Friday and Saturday.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...Duke
AVIATION...Duke
HYDROLOGY...CAS



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