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000
FXUS63 KGRR 210221
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1021 PM EDT Wed Sep 20 2017

LATEST UPDATE...
Update

.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 Thursday and Friday, then in the mid to upper 80s over the
weekend.

&&

.UPDATE...
Issued at 1021 PM EDT Wed Sep 20 2017

Still expect upstream convection over WI to weaken, however
latest short term guidance and radar trends suggest higher pops
may be warranted for the Mason/Oceana county area for a least a
few hours... roughly 04Z-07Z. MU Capes near 2000 J/KG and good
moisture transport/convergence via 30-35 kt low level jet should
allow convection to work into this area and/or promote development
of new cells soon ahead of the current line.

Meanwhile will have a dry fcst tonight south of a Muskegon to Mt
Pleasant line where upper ridge is in control. Risk of fog is
lower than previous nights with a bit more wind in the boundary
layer.

&&

.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

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 00Z TAFS through 00Z Thursday evening)
Issued at 805 PM EDT Wed Sep 20 2017

Other than a period of MVFR fog (vsbys 3-5SM) from roughly 09z-
14z, predominately VFR weather is expected the next 24 hours.

The line of tstms currently over WI is expected to weaken as it
crosses lake MI later this evening, but could still impact MKG
before dissipating. A brief period of gusty/erratic winds may
occur overnight as whatever is left of that line moves through
MKG.

Isolated storms may develop Thursday afternoon, especially east
of GRR, but did not include thunder in any of the TAFs due to
very low probability/limited coverage.


&&

.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.
&&

$$

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