Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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352
FXUS63 KGRR 190747
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
247 AM EST Sun Feb 19 2017

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

.SYNOPSIS...
Issued at 247 AM EST Sun Feb 19 2017

Very warm weather will continue through Thursday with highs well
into the 50s and even reaching 60 or more farther south.
Rain showers are expected late Monday night into early Tuesday.
Precipitation returns Thursday night through Saturday with
notably colder, but still seasonal, temperatures.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 247 AM EST Sun Feb 19 2017

Some patchy radiation fog will be possible this morning, but we
currently don`t expect anything dense or particularly impactful.

Otherwise no changes to the inherited forecast. Raw model output
has been under-forecasting temperatures pretty significantly
lately and this gets exacerbated in derived MOS guidance that
is calibrated more towards climatology than towards record or
near record temperatures observed yesterday and expected for much
of the coming week. We have accounted for this by bumping guidance
temperatures up a few degrees or more (which still wasn`t enough
Saturday for many locations).

Confidence is growing with timing of upcoming precipitation.
Most rainfall should occur between midnight and noon on Tuesday.
Instability looks too weak //MUCAPE less than 200 J per kg// to
mention thunder at this time.

.LONG TERM...(Tuesday night through Saturday)
Issued at 247 AM EST Sun Feb 19 2017

Well above normal temps will become the norm through the rest of the
work week, but then we will see temps crash Friday night into
Saturday as a strong system drags in much colder air.

The mid week period looks largely quiet with zonal flow.  The
progressive pattern should bring a weak cold front through SW MI Wed
night.  This should bring more clouds into the area, but pcpn looks
minimal as the front may even come through dry.

The pattern gradually changes later in the week as an upper trough
deepens across the western U.S. and cyclogensis occurs over the
Plains by Thursday evening.  A deep SW flow will develop ahead of
this system and this should spread Gulf moisture toward the Great
Lakes. This moisture should be riding north over a stationary front
over the southern Great Lakes.  This should be a set up for a
soaking rain.  Thunder may even be possible, but given the position
of the stationary front, we should remain on the cooler and more
stable side of the system.

The upper trough will progress east by Friday night and pull the
Plains surface low into the Great Lakes.  An impressive surge of
cold air is progged by all the models, with similar timing leading
to more confidence on how this should unfold.  The steady rains
should continue through Friday with the surface low tracking from
near Chicago to Lake Huron by Friday night.  All this points to the
rain changing to snow Friday night and remaining snow into Saturday.
H8 temps plunge from around +6C Friday to around -11C by Saturday.
Some lake enhancement may even occur into Saturday.  All told this
snow will occur on the back side of the surface low, so significant
accums are not expected, but this will be a quick blast that will
return the region to winter.  This system will also come with brisk
WNW winds, bringing wind chill readings down into the teens.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1151 PM EST Sat Feb 18 2017

VFR conditions will continue through the next 24 hours with just
some high cloudiness around. Vsbys will remain unrestricted,
however some isolated fog could occur around daybreak. WNW winds
will remain very light.

&&

.MARINE...
Issued at 247 AM EST Sun Feb 19 2017

No concerns in the short term, however winds become southerly and
increase significantly Monday into Monday night. So small craft
advisory headlines may be needed at this time at least for
northern zones where larger waves will be possible with the longer
fetch.

&&

.HYDROLOGY...
Issued at 250 PM EST Sat Feb 18 2017

Light rain late Monday night into early Tuesday is
expected...though this result in no hazardous hydrologic
concerns.

&&

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

$$

SYNOPSIS...TJT
SHORT TERM...TJT
LONG TERM...JK
AVIATION...JK
HYDROLOGY...Maczko
MARINE...TJT



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