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000
FXUS63 KGRR 201941 CCB
AFDGRR

Area Forecast Discussion...CORRECTED
National Weather Service Grand Rapids MI
341 PM EDT Wed Sep 20 2017

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

.SYNOPSIS...
Issued at 330 PM EDT Wed Sep 20 2017

Unseasonably hot and dry weather is expected through the weekend.
There is a weak cold front coming into the area tonight that may
bring some thunderstorms to areas west of Holland to Big Rapids
early Thursday morning. Highs will likely be around 90 to the mid
90s Thurssday and Friday, then in the mid to upper 80s over the
weekend.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 330 PM EDT Wed Sep 20 2017

We do have a cold front with convection associated with it
heading into our CWA overnight. The front will dissipate by midday
Thursday. Even so, we have good moisture transport and
convergence north of MKG after midnight. There is instability and
the nose of the low level jet pokes into the area too so I do
expect thunderstorms between midnight and sunrise over our NW CWA.
Those will dissipate by mid morning and likely will not impact
areas east of US-131.

High pressure rules after that. The 1000/850 thickness and 850
temps suggest highs in the lower to mid 90s Thu and Fri.


.LONG TERM...(Saturday through Wednesday)
Issued at 330 PM EDT Wed Sep 20 2017 to result in dense fog but th

Strong upper ridge with 590+ dm heights will be centered over the
Central Great Lakes through the weekend. Deep layer subsidence will
provide dry weather and mostly clear/sunny skies, and support a
continuation of very warm temperatures. High temperatures on
Saturday look to again approach records, with the expectation of
high reaching the mid 80s to low 90s.

Energy ejecting out of the west coast trough will work through the
Great Lakes midweek, pushing a cold front through Lower Michigan
Tuesday night and Wednesday. This will provide a chance for showers
and thunderstorms, and usher in cooler and more seasonable
temperatures on Wednesday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 134 PM EDT Wed Sep 20 2017

Ridging will maintain VFR conditions and dry weather through the
afternoon and early evening. Low pressure tracking through central
Canada will drive a frontal boundary through the area tonight and
Thursday. This will increase moisture over west Michigan, but the
front will weaken as it encounters the ridge over the area,
keeping chances for precipitation very low tonight. Best
potential still looks to reside at MKG and GRR, but confidence in
occurrence is very low. Increase in cloud cover should help
mitigate the threat for dense fog. Will favor MVFR visibilities
late tonight and Thursday morning for most location, with IFR more
likely to occur at BTL, AZO, and JXN.

&&

.MARINE...
Issued at 330 PM EDT Wed Sep 20 2017

There will be some thunderstorms overnight as the frontal band
moves through so higher winds and waves should be expected near
those storms. After that, from mid day Thursday into the weekend
high pressure means light winds. Dew points should not get high
enough to result in dense fog but that is something to think
about even so.

&&

.HYDROLOGY...
Issued at 330 PM EDT Wed Sep 20 2017

Abnormally dry conditions are expected to continue into next week
aside from isolated pockets of heavy downpours. The most favored
locations for isolated showers and storms Wed night will be near
Lake Michigan, then on Thu in Central Michigan. Thereafter, warm and
dry weather is expected to dominate into early next week.

&&

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

$$

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