Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 111902

Area Forecast Discussion
National Weather Service Grand Rapids MI
302 PM EDT Tue Aug 11 2020


Issued at 154 PM EDT Tue Aug 11 2020

- Most areas won`t see any rain through Friday

- Chance for showers and storms returns this weekend


.DISCUSSION...(This evening through next Tuesday)
Issued at 301 PM EDT Tue Aug 11 2020

-- Most areas won`t see any rain through Friday --

Ensemble guidance supports a predominantly dry period from
Wednesday through Friday. Sfc-850 mb flow looks E/SE and the ECMWF
RH layer analysis reveals a pretty dry airmass in place through
Friday. There may be an isolated shower Friday especially near
the lakeshore with some sfc wind convergence aiding any cumulus
field that develops, but soundings look rather dry, and 0-6 km
shear values of 10 knots or less would ensure anything that does
develop would not be sustained for long.

-- Chance for showers and storms returns this weekend --

An upper level jet moves into the Midwest/Great Lakes region this
weekend and mid level height falls will begin Saturday. A surface
cold front could approach as early as Saturday night but more
likely sometime on Sunday, with an increase in dew points / PWAT
values ahead of the front across the region. Depending on the
timing of the front, there would be a risk for thunderstorms
especially if it holds off until Sunday afternoon. The 12z ECMWF
is a bit quicker now with this front and pushes it through Sunday
morning, and the ECM mean follows this trend (at least the 00z/06z
runs). The 51-member ensemble mean probability of CAPE > 1000
J/kg on Sunday is currently 20-30%. So, it is possible we would
just be looking at a band of showers moving through late Saturday
night into Sunday, but subtle changes in timing could increase
thunderstorm chances.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1246 PM EDT Tue Aug 11 2020

We`ll see mainly clear skies through the period. JXN may see some
fog for a couple of hours around sunrise.


Issued at 301 PM EDT Tue Aug 11 2020

The lake will be pretty tranquil the next several days with little
in the way of wave action. Conditions look favorable for small
craft activities at least into Friday.




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