Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 170139

Area Forecast Discussion
National Weather Service Grand Rapids MI
939 PM EDT Tue May 16 2017


Issued at 328 PM EDT Tue May 16 2017

Unseasonably warm weather will continue through Thursday before a
cold front moves through late Thursday. Scattered showers and
thunderstorms are possible Thursday. A cooler airmass will move in
for Friday. Another chance for showers and thunderstorms will come
for the weekend.


Issued at 939 PM EDT Tue May 16 2017

Have raised tonight`s low temperature in many areas, particularly for
the Lakeshore counties. Typically with a breezy south wind all
night in this type of pattern, temps do not fall as much -
especially at the lakeshore. The latest Lamp guidance supports
this notion.


.SHORT TERM...(This evening through Thursday night)
Issued at 328 PM EDT Tue May 16 2017

Primary short term fcst concerns involve determining convective
potential Wednesday through Thursday.

12Z short range guidance trends indicate somewhat better
potential for scattered showers and thunderstorms to develop
Thursday along and just ahead of the cold front.

The relatively best chc for convection should come mid to late
Thursday afternoon over our se fcst area where sb cape values
will potentially reach around 1000-2000 j/kg just ahead the front
at max heating.

Severe wx is not expected given lack of stronger instability or
forcing from the front and with more favorable upper level
dynamics staying north of our area.

Unseasonably warm weather will continue tonight through Wednesday
as fairly strong southerly winds continue to advect a warmer and
more humid airmass into our area. High temperatures will reach the
middle 80`s across most of our fcst area again tomorrow. A low
pressure system approaching from the west will bring potential for
a few showers late Wednesday night.

.LONG TERM...(Friday through Tuesday)
Issued at 328 PM EDT Tue May 16 2017

Main feature in the long term will be an upper low that ejects out
of the western trough on Friday. The upper low is then forecast to
move through the upper midwest over the weekend. Friday looks to be
dry day as we will be in between systems. Showers and possibly a few
storms are expected from Saturday into Sunday. The surface low will
pass well off to our west, but a warm front Saturday night followed
by a cold front on Sunday will bring our chances for precipitation.
Thunder chances do not look high as instability is somewhat limited.
Enough instability and forcing will likely be present though to keep
the mention in the forecast. Upper troughing will persist for Monday
into Tuesday with scattered showers possible.

Highs in the 60s on Friday will warm into the lower 70s over the
weekend, before cooling back into the 60s for early next week.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 755 PM EDT Tue May 16 2017

Main aviation impact over the next 24 hours will be the wind.
South to southwest sfc winds may diminish a bit this evening as
daytime mixing ceases. However winds are progged to increase to
40-45 kts at 2000 ft by midnight which could lead to LLWS

On Wednesday sfc winds will become strong/gusty once deeper
daytime mixing commences by mid morning. Sustained winds of 20 kts
with gusts to 30 kts will be common Wed afternoon.

Otherwise confidence is high that VFR/dry weather will continue
tonight and Wednesday within warm sector air mass.


Issued at 328 PM EDT Tue May 16 2017

South winds of 15 to 25 knots are anticipated through Wednesday
night which will result in wave heights of 3 to 5 feet. A small
craft advisory remains in effect through Wednesday night.


Issued at 328 PM EDT Mon May 15 2017

Rivers are running well within banks. Rain still looks on track for
the weekend. Basin average rainfall currently looks to be about
0.50"-1.00" but with locally higher amounts possible. Some river
rises are likely with this rain but not expecting flooding at this
time. Smaller streams and rivers may need to be watched for above
bankfull rises. Main stem rivers should be able to handle this
rainfall fine unless guidance trends upward.


LM...Small Craft Advisory until 6 AM EDT Thursday for LMZ846>849.



SHORT TERM...Laurens
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