Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 180532

Area Forecast Discussion
National Weather Service Grand Rapids MI
1232 AM EST Sat Feb 18 2017


Issued at 322 PM EST Fri Feb 17 2017

A warm front will move north through Lower Michigan tonight and set
the stage for a few days of mild weather. Highs in the 50s are
expected this weekend along with some sunshine. The next chance of
rain comes Monday night when low pressure moves east across the
Upper Mississippi Valley.


.SHORT TERM...(This evening through Sunday night)
Issued at 322 PM EST Fri Feb 17 2017

Forecast concerns are minimal this afternoon. Latest vis loop shows
clear skies across the cwa which reveal the snow line...roughly along
and north of M-46. Sfc obs reveal a warm front near Chicago moving
north. Temps south of this front are in the mid 60s today.

The warm front will move north tonight and higher dewpoints will
arrive with it. The higher moisture crossing the colder sfc temps
north of the snow line may result in some patchy fog, so we have
that in the night time grids for the next couple of nights.
Otherwise not much sensible weather to speak of as high pressure
camps out over the Upper Mississippi Valley.

Temps will climb into the 50s over the weekend and we`ll see a fair
amount of sunshine too.

.LONG TERM...(Monday through Friday)
Issued at 322 PM EST Fri Feb 17 2017

GFS broke continuity again and trended faster with the timing of
precip arrival for the northern stream low late Monday into Tuesday.
Prefer the consistently slower ECMWF here based on persistence of
shortwave ridging ahead of the low. POPs from the model blend were
dropped for Monday afternoon across the far western zones and
lowered for Tuesday night. Precip should be light as the low remains
separate from the southern stream so not much Gulf moisture is drawn
north. P-type looks to be all rain even up north as suggested by
thickness tools and forecast thermal profiles.

Another low tracks north of Lake Superior late Wednesday but any
precip with this should be inconsequential and limited to the
northern forecast zones. A trailing front from this low lays out
across Lower Michigan on Thursday as Plains cyclogensis is underway.
Overrunning precip breaks out along the front and intensifies
Thursday and Thursday night with the main low arriving Friday.
Precip should be mostly rain except for a mix Thursday night across
the north as cold air holds on in easterly flow.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1232 AM EST Sat Feb 18 2017

VFR conditions will continue through the next 24 hours. Even so,
there are a couple of aviation concerns. Low level wind shear will
be possible until close to daybreak. Winds near the surface are
only around 10 knots, while they increase rapidly to around 45
knots just 1K ft above the ground. This wind core moves through
quickly, so the LLWS threat should be moving out prior to

The surface southwest winds will remain brisk at 10-15 knots until
late afternoon when they will finally diminish.

Another issue for aviators could be the development of fog toward
midnight Saturday night. Low winds, and high dew points over the
frozen ground could produce fog. Some IFR may develop toward the
end of this TAF period and toward I-96.


Issued at 322 PM EST Fri Feb 17 2017

Southwest winds 10-20 knots will result in wave heights 2-4 ft
during the next couple of days.


Issued at 1141 AM EST Fri Feb 17 2017

Precipitation chances will remain low through Monday across the
region. Area rivers will continue to fall slowly as a result. The
precipitation event late Monday into Tuesday could cause new
rises to develop. Temperatures will remain warm enough to prevent
ice formation.




LONG TERM...Ostuno
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