Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 221751
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
151 PM EDT Fri Sep 22 2017

LATEST UPDATE...
Aviation

.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 18Z TAFS through 18Z Saturday afternoon)
Issued at 151 PM EDT Fri Sep 22 2017

Two items to keep an eye on the next 24 hours in regard to
aviation. The first will be the chance for some isolated showers
and thunderstorms at KAZO, KBTL, KLAN and KJXN this afternoon and
early evening. Best chances (albeit small) for precipitation are
between 19z and 01z. At this point given the isolated threat of
precipitation have only included VCSH wording. A few thunderstorms
are certainly possible however given the amount of instability
present today. Shower and thunderstorm chances should end by 02z
at the latest.

The next item of concern is some light fog late tonight. MVFR
visibilities of 3-5SM are possible at KAZO, KBTL, KLAN and KJXN
between 09z and 14z.

Otherwise expecting VFR weather the remainder of the time with
mostly clear skies. There will likely be some broken ceilings
though across South Central Lower Michigan this afternoon with
bases around 5,000ft.

&&

.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 1054 AM EDT Fri Sep 22 2017

Rivers are running around normal to below normal for the time of
year. Meanwhile, the US Drought Monitor is indicating dry conditions
across Southern Lower Michigan. Isolated thunderstorms may develop
during the afternoon and early evening near I-69. Near-record warmth
is expected today through the weekend. The next chance for rain is
Wednesday. No river issues are expected through next week.

&&

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

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...NJJ
AVIATION...Duke
HYDROLOGY...63
MARINE...WDM


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