Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 210557
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
157 AM EDT Tue Mar 21 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.

&&

.UPDATE...
Issued at 1014 PM EDT Mon Mar 20 2017

Updated to remove precipitation from the forecast as it looks like
we will remain dry through the night. Added the mention of fog to
the southern CWA as some low clouds and fog have developed.
Residual moisture hangs on across the south in a very light wind
regime. Some wind (north 10-15 knots) does develop after 06z just
off the surface so the thinking is the fog should not get too out
of hand. BTL is the anomaly at this point with a 1/4SM visibility
at 10pm. Again, expecting this to improve overnight down along
I-94.

&&

.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 06Z TAFS through 06Z Tuesday night)
Issued at 157 AM EDT Tue Mar 21 2017

Low level moisture and clearing skies have resulted in fog that
is periodically sending vsbys down near 1/4SM at southern TAF
sites. Otherwise, we are generally hovering between 1-3SM. This
should only last for the next few hours or so. Better mixing is
expected to result in gradually improving conditions. MVFR and
VFR is expected to return through dawn Tuesday morning.

VFR conditions are expected through Tuesday. Winds will shift out
of the northwest and increase to 10-15 kts. Gusts of 15-25 kts
are possible through the afternoon. Mixing heights remain elevated
through the evening. Therefore, gusts of around 20 kts could
extend near/past dusk Tuesday evening.

&&

.MARINE...
Issued at 1014 PM EDT Mon Mar 20 2017

Multiple runs of the wave models have some waves increasing
Tuesday midday. A SCA level wave event should persist into midday
on Wednesday. We have therefore issued a Small Craft Advisory from
noon on Tuesday through noon on Wednesday. Waves should peak
Tuesday evening in the 4 to 6 foot range.


&&

.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...Small Craft Advisory from noon today to noon EDT Wednesday for
     LMZ844>849.

&&

$$

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



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