515
FXUS63 KGRR 210525
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
1225 AM EST Thu Nov 21 2024
.KEY MESSAGES...
- Rain Mixing with Snow Tonight
- Snow/Rain and Winds on Thursday
- Rain Showers Sunday night into Monday
&&
.UPDATE...
Issued at 900 PM EST Wed Nov 20 2024
Scattered rain showers continue in progress across our area attm.
A consensus of latest high res model guidance continues to
suggest that rain showers will become mixed with snow showers late
this evening as thermal profiles cool. Pcpn will then transition
to mainly snow showers during the early morning hours Thursday
across much of our area. The exception to this is near the Lake MI
shoreline where the west winds off relatively mild lake waters
will keep low level thermal profiles a bit milder there. No
significant fcst changes are necessary this evening.
&&
.DISCUSSION...
Issued at 323 PM EST Wed Nov 20 2024
- Rain/Snow Tonight into Thursday
Will hold off on a Winter Weather Advisory after coordination with
surrounding offices. Surface temperatures are marginal and
confidence is low in snow being heavy/persistent enough to
overcome road temps above freezing.
The only change in the forecast was a slight westward shift in the
axis of heavier QPF. This did not affect storm total snow amounts
that much. The two areas of concern remain the high ground of
Osceola County where the mesoscale bands of snow associated with
enhanced f-gen forcing pivot and snow rates will combine with
lower skin temps to allow potential accumulations in the 2 to 4
inch range, along with the Kalamazoo area where lake enhanced
snow in west-southwest flow could result in 1 to 4 inches from
late tonight into Thursday afternoon. There could be some minor
impacts to travel in those areas for the morning commute.
The upper low is expected to rotate through tonight with
secondary sfc cyclogenesis to the east, resulting in a dissipating
sfc low across western Lower Michigan by Thursday afternoon. The
area of f-gen forcing weakens as it moves south and the steadier
snow and rain tapers off to showers during the afternoon. Travel
impacts are expected to be minor as precip winds down and sfc
temperatures are above freezing by the evening commute.
Lake effect snow and rain showers Thursday night will be in north
to northwest flow, so most of the precip will be close to or
offshore of Lake Michigan.
- Rain Showers Sunday night into Monday
A mid level wave is shown to dig down into the Great Lakes Region on
Monday from the Northern Plains on Monday. Warm air advection ahead
of this feature will shift the rain/snow line north of the CWA.
Moisture from the Gulf of Mexico gets drawn into the system as
modeled PWAT values make a run at an inch along the MI/IN border.
The moisture deepens up ahead of this wave Sunday night into Monday
so there will be a high probability for rain. However a noticeable
dry slot is seen at 500 mb to perhaps later in afternoon or more so
Monday night the precipitation will diminish. Most ensemble QPF
members show values remaining under a quarter inch.
The cold air that is shown to advect in behind this system for
Monday night into Tuesday does not look favorable for much in the
way of lake effect. Temps at 850 mb only drop down to -8 deg C or
so.
&&
.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1220 AM EST Thu Nov 21 2024
Local radar shows rain and snow showers across western Lower.
Surface obs show mostly snow at the terminals and that will
continue overnight. A mix of IFR/MVFR can be expected as
precipitation increases overnight as low pressure near the Straits
moves south over the lake. Precipitation will be snow but may end
as light rain at MKG during the early afternoon. We`ll see slow
improvement of both ceilings and visibilities after mid afternoon.
&&
.MARINE...
Issued at 323 PM EST Wed Nov 20 2024
No changes to the SCA/Gale Watch. We are looking at strong winds
and potential gales from tomorrow persisting into Saturday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 7 AM EST this morning for LMZ844>849.
Gale Watch from 7 AM EST this morning through late tonight for
LMZ844>849.
&&
$$
UPDATE...Laurens/RAH
DISCUSSION...MJS/Ostuno
AVIATION...04
MARINE...Ostuno
NWS GRR Office Area Forecast Discussion
