Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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097
FXUS63 KGRR 270721
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
321 AM EDT Thu Jul 27 2017

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

.SYNOPSIS...
Issued at 321 AM EDT Thu Jul 27 2017

A cold front will move through Lower Michigan today with only
scattered showers and thunderstorms then drier conditions can be
expected into the weekend as high pressure builds in.

&&

.SHORT TERM...(Today through Saturday)
Issued at 321 AM EDT Thu Jul 27 2017

Forecast issues in the near term are for POPs today as cold front
moves through with a few showers and thunderstorms, then the
potential for some diurnally enhanced showers and isolated
thunderstorms on Friday as upper low comes through.

For today, showers across the northern forecast area early this
morning will gradually move south this morning and forecast
soundings show enough instability for thunderstorms across the
central and southern zones through the day. Drying behind the
front begins this evening with showers ending across the southern
zones by midnight.

Heights fall and lapse rates steepen on Friday morning as an upper
low moves across the central Great Lakes with showers and
thunderstorms diurnally enhanced into the afternoon. Superblend
POPs seemed a bit low given the good model agreement on the
strength of this feature and were adjusted up and if trends
continue could be bumped up further in the future.

The upper low departs Friday night with strong sfc ridging and
height rises meaning dry weather Friday night and Saturday.

.LONG TERM...(Saturday night through Wednesday)
Issued at 321 AM EDT Thu Jul 27 2017

A high pressure ridge will continue in control of the wx pattern
Saturday night through Sunday night and bring fair wx with
seasonable temperatures. High temps Sunday will reach 80 to 85
degrees with min temps mainly in the 50`s.

The overall wx pattern continues to look quite dry through next week
as a high pressure ridge will continue to dominate the wx
pattern. A weak cold front moving in from the northwest will
bring a chance for a few showers and storms by late Wednesday or
Thursday but significant rainfall is unlikely as this system will
have very little moisture to work with. Temps will continue
to average near normal through the long range fcst period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1130 PM EDT Wed Jul 26 2017

Vfr conditions will continue overnight before gradually
deteriorating to Mvfr during the early morning hours Thursday due
to patchy fog and low clouds. Conditions will improve back to vfr
at all the terminals by mid morning with vfr then anticipated
through the afternoon and evening.

Scattered showers will develop at our southern terminals Thursday
afternoon but conditions should remain primarily vfr. Cannot rule
out potential for isolated thunderstorms Thursday afternoon that
could cause very brief reductions to mvfr/ifr but there is not
enough potential for thunderstorms at our southern terminals
Thursday afternoon to warrant mention in those terminal fcsts at
this time.

&&

.MARINE...
Issued at 321 AM EDT Thu Jul 27 2017

North winds to 20 knots will build waves to 2 to 4 feet across
the nearshore waters north of Whitehall by late this afternoon.
Some 3 to 5 foot waves are possible near Little Sable and Big
Sable points this afternoon. Winds and waves will decrease
overnight.

&&

.HYDROLOGY...
Issued at 324 PM EDT Wed Jul 26 2017

Thunderstorms rolling along the US-10 / M-20 corridors early this
afternoon have produced rainfall amounts between a half to one inch.
Given PW values around 1.75 inches in that area, any convection will
have efficient rainfall rates. Additional storms developing upstream
in Wisconsin will affect some of the same areas through this
evening. Much of the area has been dry over the last two weeks, so
this rain is beneficial. WPC indicates only a marginal risk of
excessive rainfall, and it is easy to agree with that. There is
chance of showers and storms in the southern portion of Lower
Michigan Thursday into Friday morning, but the questionable coverage
of convection will keep the risk of excessive rain very low.

&&

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

$$

SYNOPSIS...Ostuno
SHORT TERM...Ostuno
LONG TERM...Laurens
AVIATION...Laurens
HYDROLOGY...CAS
MARINE...Ostuno



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