Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 210001
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
801 PM EDT Mon Mar 20 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 307 PM EDT Mon Mar 20 2017

After precipitation exits the region early this evening, quiet
weather is expected into Thursday, with highs Wednesday only in
the 30s. Thursday night through the weekend looks wet and mild
with highs Friday getting up into the 60s.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 307 PM EDT Mon Mar 20 2017

Some rain showers are still noted upstream, but both PoPs and
the thunder threat continue to wane. Therefore have trimmed late
afternoon / early evening PoPs even more with this update.

After this evening, there is high certainty for quiet weather
through the period. An unseasonably strong surface high //max
pressure close to 1040 mb// will dominate the area with seasonably
cool temperatures. Model predictability is excellent for these
scenarios, so there is high certainty that we will not see any
impactful weather.

.LONG TERM...(Thursday through Monday)
Issued at 307 PM EDT Mon Mar 20 2017

A soggy period begins Thursday night as sfc high moves east with
overrunning pattern developing. Residual cold air is eroded by
southerly flow but some wet snow could mix in across the interior
northeast zones at the outset of the precip Thursday evening.

A sfc front stalls across Lower Michigan in zonal flow regime on
Friday and Saturday. There could be a sharp temperature gradient
from north to south both of those days, although Friday looks to be
the warmer day as the front is further north. Shallow cold air is
expected across the northern forecast area by early Saturday. There
is even a chance of an icy mix across the far northern zones by
Saturday evening under continued low level cold advection.

Sfc low occludes and weakens by Sunday as it tracks into northern
Illinois with low level easterly flow continuing across Lower
Michigan and shallow cool air inversion probably holding in the low
clouds and drizzle through Monday. Tweaked daytime maxes down from
Saturday through Monday to account for clouds, precip and shallow
low level colder air.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 800 PM EDT Mon Mar 20 2017

A cooler and drier airmass will gradually filter into the region
over the next 24 hours, which should take away any threat for low
clouds and fog over time. That said, residual moisture down
towards I-94 tonight will allow for MVFR conditions to redevelop
in terms of light fog. IFR visibilities are not out of the
question, but did not put these in the TAF just yet.

Ceilings should remain VFR through the period with a gradual
clearing taking place through the course of tonight. Mainly clear
skies are expected on Tuesday, but during the afternoon we may see
stratocumulus clouds develop. Bases should be around 3500ft with
some help from Lake Michigan with over lake instability
increasing.

Northerly winds will be common the next 24 hours becoming gusty
Tuesday afternoon in the 10-22 knot range.

&&

.MARINE...
Issued at 307 PM EDT Mon Mar 20 2017

Recent WaveWatch3 guidance shows waves exceeding small craft
advisory criteria Tuesday afternoon into evening with strong
northerly winds behind the cold front. Details and exact timing are
still a little fuzzy. A small craft advisory will be needed, but
will let subsequent shift hammer out details with newer model
guidance.


&&

.HYDROLOGY...
Issued at 140 PM EDT Mon Mar 20 2017

Generally 0.05 to 0.25 inches of precipitation fell Monday morning.
Scattered showers could produce similar amounts in portions of the
area this afternoon and evening. Flooding is not expected. Tuesday
through Thursday looks dry. Later this week and into next week,
there are indications of mild temperatures returning and several
rounds of showers and thunderstorms being possible.

&&

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

$$

SYNOPSIS...TJT
SHORT TERM...TJT
LONG TERM...Ostuno
AVIATION...Duke
HYDROLOGY...CAS
MARINE...TJT


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