FXUS63 KGRR 210425

Area Forecast Discussion
National Weather Service Grand Rapids MI
1225 AM EDT Tue May 21 2019


Issued at 330 PM EDT Mon May 20 3309

-Frost likely tonight north of I-96

-Not as cold Tuesday but considerable clouds

-Scattered showers and storms late Tuesday night and Wednesday
morning; another round late Wednesday night and Thursday morning

-Turning warmer and more humid later in the week. Highs near 80
Thursday through Saturday


.DISCUSSION...(This evening through next Monday)
Issued at 330 PM EDT Mon May 20 3309

Arrival of sfc ridge will clear out the low clouds from northwest
to southeast later this afternoon and evening, and winds will
become light or calm tonight. This will set the stage for a cold
night with areas of frost north, and no changes are planned to
the existing Frost Advisory. One concern is the arrival of high
level cloudiness from the southwest tonight holding temps up,
although this should be mostly thin cirrus especially north.

Considerable mid and high level cloudiness is anticipated on
Tuesday. The NAM is trying to produce measurable precip south of
GRR, but this may be difficult considering the low levels are
quite dry with an amplifying upper ridge present aloft. Probably
mostly a virga/sprinkle event.

Late Tuesday night and Wednesday we have the warm front lifting
back north as plains upper low lifts north and pushes
out/flattens the upper ridge ovhd. This leads to a period of
scattered showers and tstms aided by a 45 kt low level jet with
MUCapes near 1500 J/JG. These would be elevated storms in the late
night/early morning hours, and are not expected to be severe at
this time.

A weakening cold front/trough slips in from the west late
Wednesday night and Thursday morning, offering another chance of
scattered convection. That chance appears to end by Thursday
afternoon as the sfc front settles south of the state.

The temp and precip fcst for the upcoming Memorial Day weekend
will hinge on the location of a wavering sfc boundary, which leads
to a low confidence fcst at this time. Currently showers and
storms appear likely on Friday night/early Saturday but beyond
that it is unclear whether the front will position itself south of
the state or buckle/waver north again.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday)
Issued at 1215 AM EDT Tue May 21 2019

VFR conditions will continue at all the terminals through
Tuesday evening with wind speeds aob 10 kts through then. A few
showers may develop at the KMKG terminal by late Tuessday evening.
Rain will develop at the rest of the terminals after 06Z


Issued at 330 PM EDT Mon May 20 3309

While wave heights are only running 2-4 feet, northwest winds are
still reaching 20-25 kts so will let the Small Craft Advisory run
until 5 pm. Winds will be offshore on Tuesday and Wednesday so
minimal wave action expected.


MI...Frost Advisory from 2 AM to 8 AM EDT Tuesday for MIZ037>040-



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