Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 251957
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
300 PM EST Sun Feb 25 2018

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

.SYNOPSIS...
Issued at 300 PM EST Sun Feb 25 2018

High pressure will build in and bring fair weather tonight through
Tuesday. Temperatures will average much above normal for this time
of year from early to midweek. A low pressure system will bring
potential for a mix of rain and snow Thursday.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 300 PM EST Sun Feb 25 2018

Short term fcst concerns are minimal. Wind speeds will slowly
diminish late this afternoon and evening and a high pressure ridge
will build into the lower Great Lakes region and bring fair wx
tonight through Tuesday.

Temperatures will continue to average above normal for this time
of year reaching well into the 40s Monday and into the middle to
upper 50s Tuesday as winds become southerly on the back side of
the departing ridge.

There is a small chance for scattered very light rain showers to
develop late Tuesday night in the sw flow warm air advection
pattern and in an area of isentropic ascent.

.LONG TERM...(Wednesday through Sunday)
Issued at 300 PM EST Sun Feb 25 2018

Looks like a significant storm is still possible from Wednesday
night into Thursday night. Teleconnections to a strong block over
southern Greenland suggest the low will be blocked from moving
further north than currently forecast. With the subtropical jet and
warm conveyor belt staying well off to the south and east, this does
not look like a heavy rain event and QPF values should remain below
an inch liquid.

The forecast problem is how much of the precip will be liquid and
how much will be wet snow. Forecast soundings show the DGZ saturated
through Thursday night as colder air wraps in behind the low and we
expect a transition over to snow Thursday evening given the current
forecast path of the low. Some accumulation of heavy wet snow is
possible so this will have to be watched for further refinements to
the thermal profiles.

Only minor changes were made to other periods, with max temps
lowered a bit on Wednesday as clouds and light rain showers should
hold temperatures below guidance.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1252 PM EST Sun Feb 25 2018

VFR conditions will prevail except for a few areas of MVFR this
afternoon. West winds will gust over 30 knots at times this
afternoon before decreasing below 20 knots this evening.


&&

.HYDROLOGY...
Issued at 300 PM EST Sun Feb 25 2018

The Grand River crest is moving through Kent County this weekend and
will move through Ottawa County early in the week. This crest
will likely stay below the levels seen in April 2013. The crest
of the Kalamazoo River is moving out of Kalamazoo and into Allegan
county. Kalamazoo / Comstock Twp river level reached record high
levels, surpassing other historic crests of 2008, 1985, and 1947.
The Thornapple River has crested at levels not seen since at least
1985. River levels in Battle Creek and Lansing were the highest seen
since 1975. Even after river levels crest, flooding will persist
along many rivers for a number of days. Flood impacts/extent in
some communities may differ compared to similar historic crests due
to recent flood mitigation projects or other development, and it
will take rigorous documentation and analysis to adjust flood
expectations for future events along the many river points that have
been affected.

Rainfall Saturday night will amount to a quarter inch and possibly
less. This will not have much impact on river levels, but could
slightly prolong the duration of flooding on some rivers. The next
precipitation event to monitor will be on Thursday. Model guidance
is suggesting the possibility for around an inch of precip (though
perhaps not all of it will be rain).

Please see the latest flood warning/advisory statements or river
hydrographs for details. Hydrographs are available by going to
weather.gov/grr and clicking on the "Rivers and Lakes" link above
the map of flood warnings.

&&

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

LM...None.
&&

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...Ostuno
AVIATION...Ostuno
HYDROLOGY...CAS/Ostuno



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