Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 150547

Area Forecast Discussion
National Weather Service Grand Rapids MI
147 AM EDT Thu Mar 15 2018


Issued at 249 PM EDT Wed Mar 14 2018

High pressure will retreat southeast tonight allowing a cold front
to drop through the region. Most of the area is expected to remain
dry, however portions of West Michigan may see a few lake effect
snow showers or flurries behind the front late tonight and
tomorrow. Temperatures on Friday will run cooler than normal, with
highs in the 30s. Dry weather is expected Thursday night through
Friday as high pressure builds over the area once again.


.SHORT TERM...(This evening through Friday night)
Issued at 249 PM EDT Wed Mar 14 2018

Shortwave energy stretched from Upper Michigan through Hudson Bay
will drop through Lower Michigan tonight. Northern extent of
surface ridge centered over the Central/Southern Plains that has
brought the quiet weather today will retreat south this evening as
surface trough tied to this energy works southeast across the
area. This will pull a cold front through Central and Southern
Michigan this evening and early tonight. Frontal forcing does not
look strong enough to make much headway in antecedent dry airmass,
especially given weak theta-e advection signal and lack of
instability shown in forecast models. Will therefore keep the
forecast dry through the frontal passage early tonight. More
challenging portion of the short term forecast then comes in the
colder airmass behind the front, especially with regard to cloud
cover and precipitation late tonight and Thursday. Models are
keying in on low-level moisture over Ontario seeping down into
Michigan behind the frontal passage overnight. This should help
boost cloud cover and small chances for precipitation as lake
effect processes also become a factor. H850 temps fall to between
-11 and -14, increasing lake to H850 delta T values into the mid
 teens. Although inversion heights will climb to 5-6kft Thursday
 morning, moisture within the DGZ will be paltry per all
 GFS/NAM/RAP/SREF forecast soundings. Any snow showers should be
 light and fairly isolated, limited to northern portions of the
 forecast area and the lakeshore. Rain/sprinkles may mix in

Northwest flow will also keep temperatures on the cool side
tomorrow. High temperatures will run into the 30s, with gusty
winds holding wind chills in the 20s to low 30s.

High pressure will build into the area Thursday night through
Friday evening, providing dry conditions. Despite sunshine,
subsidence inversion near or below 3000 feet will limit mixing
heights and not allow warming aloft to be realized at the surface.
High temperatures will remain crisp, in the mid to upper 30s.

.LONG TERM...(Saturday through Wednesday)
Issued at 249 PM EDT Wed Mar 14 2018

Main forecast concern is precipitation Monday and Monday night, when
we currently advertise a chance of rain changing to snow Monday and
Monday night. This will be mainly south of I-96 with greater
probabilities farther south towards I-94.

A sizable majority of ECE members keep precipitation south of the
forecast area altogether. Nonetheless, we felt it was worth keeping
chances intact. Highs on Monday could get well into the 40s near I-
94. Cold and dry northeast surface flow Monday night combined with
overrunning precipitation could make light freezing rain a
possibility with the Tuesday morning commute. However, pavement
temperatures could still be fairly warm which would mitigate the
threat. Of course, all of this is highly speculative at this
forecast range. Suffice to say, it will be one of the more
interesting features to be monitored over the otherwise
uneventful coming days.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 147 AM EDT Thu Mar 15 2018

Mid clouds based around 6-7k feet are floating through the
terminals at issuance time this morning. These clouds are
associated with a cold front working through the area. Winds will
be switching to the NW. As colder air comes in and with help from
the lake, lower clouds will be gradually developing through mid
morning. These clouds could initially be around the MVFR category.
A few flurries will also be possible.

Cigs will lift to VFR toward this afternoon as some diurnal
mixing takes place. As the mixing develops, winds will also become
gusty. Wind gusts will peak in the mid 20 knot range. Winds will
die off toward sunset as mixing subsides. Clouds will likely
dissipate inland with the loss of the diurnal component, but
remain in place closer to the lake.


Issued at 1247 PM EDT Wed Mar 14 2018

River levels will continue to fall into next week. The Portage River
near Vicksburg is the only site remaining above flood stage and has
a history of falling very slowly. A fairly dry weather pattern will
develop this afternoon and last into next week.




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