388
FXUS63 KGRR 091749
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
149 PM EDT Thu May 9 2024

.KEY MESSAGES...

- Cooler Temperatures and a Chance of Showers Today

- Possible Shower/Storm Saturday and Frost Saturday Night

- Low Confidence in Forecast Details Next Week

&&

.UPDATE...
Issued at 1112 AM EDT Thu May 9 2024

Surface low is situated in Illinois this morning and is forecast
to slide east into Indiana and West Virginia as we work through
the day. The main shortwave in the mid levels is in Iowa and that
will pass well off to the south as well. A band of precipitation
is situated across southern portions of the forecast area towards
I-94. This precipitation is being driven by lift associated with
the circulation at 850mb and 700mb. Strong lift is noted in BUFKIT
overviews in that layer. The axis of lift will shift south this
evening ending the steadier precipitation. We are not expecting
heavy precipitation. Most areas towards I-94 will end up with 0.10
to 0.30 inches by evening. Kalamazoo has picked up 0.11 already.

&&

.DISCUSSION...
Issued at 335 AM EDT Thu May 9 2024

- Cooler Temperatures and a Chance of Showers Today

A low pressure center in the lower levels of the atmosphere will
move across the Ohio river valley region today while a positively
tilted upper level trough sinks south over Michigan from northern
Ontario. East to northeasterly winds will prevail with mostly cloudy
skies. Today will be the start of a few days of cooler than normal
temperatures.

Trends have continued to reduce the probability of precip throughout
the day and also decrease the rain totals over much of the area. The
rain associated with the Ohio valley low may stay mainly south of I-
96 with the heavier amounts south of I-94. The HREF 24 hours ago was
bullish on 0.5 to 1.0 inch QPF over much of the area, but now 0.5
seems unlikely for most while parts of central Michigan may stay
dry. The temperature forecast today has been nudged up slightly,
particularly northwest of Grand Rapids where it may reach the mid
60s. Amid the northeast winds, there may be low topped surface-based
convective showers developing afternoon-evening between Reed City,
Ludington, and Muskegon.

Light winds and clearing skies tonight may let temperatures dip into
the 30s with a chance of frost in the highlands of interior north-
central Michigan, Leota-Tustin area and north.

- Possible Shower/Storm Saturday and Frost Saturday Night

Shortwave trough arrives Friday night with a clipper-type low
bringing showers and a few thunderstorms lingering into the
afternoon given the steeper lapse rates. Cool air in northerly flow
on the back side of the sfc low results in low temperatures in the
upper 30s to lower 40s Saturday night with scattered frost potential
in the colder outlying areas.

- Low Confidence in Forecast Details Next Week

Shortwave ridging on Sunday eventually gives way to another trough
Monday with some showers and a few thunderstorms possible along a
cold front. There continues to be low confidence with forecast
details by the middle of next week as the GFS goes out of phase with
the Euro and GEM. There continues to be a general signal for a
longwave trough forming across the central/eastern CONUS by late in
the week which could bring some showers and storms by Thursday.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 149 PM EDT Thu May 9 2024

There is a low probability for IFR at the terminals overall, but
should it occur, it would most likely be at AZO and possibly BTL today
before 22Z. The chances for VFR at all terminals goes up
significantly after 00Z tonight.

There is a better chance for brief fuel alternate ceilings (cigs)
below 2000 feet at the I-94 terminals (AZO, BTL, JXN) as
suggested by even lower cigs just south of I-94, which we don`t
expect to encroach much farther north. Not expecting visibility to
drop below 3SM at this time. The rainband that`s oriented roughly
along a BIV to DTW line is beginning to pivot counterclockwise as
it shifts eastward, meaning that GRR should start to see
improvement relatively soon, whereas BTL and JXN could be seeing
the longest duration restrictions this afternoon into early
tonight.


&&

.MARINE...
Issued at 335 AM EDT Thu May 9 2024

An east breeze this morning will become north by afternoon with some
gusts to 20 knots. The winds near Big and Little Sable Points may be
marginally hazardous for small craft this afternoon. Northwest winds
on Saturday may build 3-5 foot waves over at least a portion of the
nearshore.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

UPDATE...Duke
DISCUSSION...Ostuno/CAS
AVIATION...TJT
MARINE...CAS