Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 220726
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
326 AM EDT Fri Sep 22 2017

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine

.SYNOPSIS...
Issued at 325 AM EDT Fri Sep 22 2017

Expect the hot and humid weather pattern we are in to last into
at least Tuesday. An isolated thunderstorm is possible this
afternoon near I-69 in the mid to late afternoon. After that the
next chance for significant rain is when the cold front finally
comes through in the Wednesday to Thursday time frame. It will
turn significantly cooler late in the week behind the cold front.

&&

.SHORT TERM...(Today through Sunday)
Issued at 325 AM EDT Fri Sep 22 2017

We are in a very stable weather pattern through the short term
forecast period. A closed upper high continues to develop today
and by Sunday covers most of the Great Lakes and Northeast. The
polar jet is well north in central Canada. As a result I see
little chance in our weather through Sunday.

There is a slight chance of an afternoon thunderstorm in the I-69
area this afternoon since there is enough instability and little
in the way of a cap. There is not much a boundary to focus on and
winds are light through a very deep layer so any storms would be
plus type.

As for the temperature, highs got to the mid 90s inland of the
Lake Shore on Thursday. With the thickness (1000/850 and 1000/925)
being nearly the same into Sunday and not expecting much in the
way of clouds, I see no reason highs will not be similar each day.
So I increased the highs above MOS values through Sunday.

It should be noted the latest in the year GRR has had heat wave
(3 days or more in a row), going back to when records started in
1892 was from the 13th through the 15th in 1939. So, if we do have
highs of 90 or more through Saturday this would be yet another
record we could break!



.LONG TERM...(Sunday night through Thursday)
Issued at 325 AM EDT Fri Sep 22 2017

We are looking at this unusual heat for this time of the year to
persist into the first portion of the long term, before we see a
change to more typical fall weather for the latter portion of the
period.

The strong upper ridge that is bringing the hot weather to the area
will only slowly build east through Mon and Tue. This will keep
temperatures well above average with dry conditions persisting.
Temperatures will make more runs at 90 degrees Mon and possibly Tue
with H850 temps around 18C.

The transition will begin on Wed, and we will see below average
temps in place for Thu and Fri. Occasional chances of rain showers
will also be possible. The initial cold front and short wave look to
pass through Tue night. Showers and storms will be possible as this
front moves through.

We will then see the cool air take control of our weather then Thu
and Fri, with occasional chances of rain showers. The long wave
trough will drop down and remain in place. Short wave troughs will
ride through the long term trough and bring the chances for rain
showers. Highs will likely remain only in the 60s by next Friday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 145 AM EDT Fri Sep 22 2017

Only real forecast impact to some of the terminals, will be some
fog this morning. Lighter winds and moist air mass will be
conducive to some fog potential. This is especially the case near
KLAN where they had the most rain yesterday afternoon. We expect
some IFR there with gradually less impacts as you move away from
there. Fog will dissipate quickly in the morning, with a sct
cumulus deck expected to develop inland around 4k feet. Winds
will remain under 10 knots through the day.


&&

.MARINE...
Issued at 325 AM EDT Fri Sep 22 2017

Winds will be light so I do not see any marine issues through
Monday.

&&

.HYDROLOGY...
Issued at 325 PM EDT Thu Sep 21 2017

A few thunderstorms may develop during the afternoon and early
evening to the east of US 131. These storms will have the potential
to produce very heavy rainfall. Coverage of these storms will be low
if development occurs, and most locations will remain dry. Dry
conditions with near-record warmth is then expected Friday through
the weekend. The next chance for rain is late Tuesday night and
Wednesday.

&&

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

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...NJJ
AVIATION...NJJ
HYDROLOGY...HLO
MARINE...WDM



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