000
FXUS63 KGRR 241708
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
108 PM EDT Wed Apr 24 2024

.KEY MESSAGES...

- Widespread Freezing Temperatures Tonight into Thursday morning

- Rounds of Precipitation in the Forecast Friday Night through Monday

- Warmer Weather Expected This Weekend into Early Next Week

&&

.UPDATE...
Issued at 1043 AM EDT Wed Apr 24 2024

Strong cold air advection is underway with temperatures
struggling to rise into the 40s this morning. Max temps this
afternoon were cut back several degrees given current obs and
upstream temperatures still in the 20s in the Upper Peninsula.

Hard freeze on track for tonight with most places dropping into
the 20s.

&&

.DISCUSSION...
Issued at 309 AM EDT Wed Apr 24 2024

- Widespread Freezing Temperatures Tonight into Thursday morning

Bottom line up front: In coordination with Detroit have decided to
upgrade the freeze watch to a freeze warning for Wednesday night
into Thursday morning.

Gusty Northwesterly flow continues with cloudy skies and strong
cold air advection behind the cold front. Downsloping flow will
continue today into tomorrow as dry, cold air settles over the
region as the day progresses. Dewpoints will drop today and
overnight into Thursday. Clearing skies follow from north to south
today as cold dry air mass pours in, with sunny skies emerging by
early afternoon as sfc dew pts drop into the teens north and 20s
south.

Guidance has been consistently showing high probabilities for sub
freezing temperatures early Thursday morning as sfc high settles
overhead with sfc dew pts of 15 to 20 in place. While some
questions of cloud cover remain, latest CAMS and ensemble guidance
have very few if any low to mid clouds with any high clouds
predominately in the far southwest. Winds are expected to drop
shortly after sunset so the calm winds will only aid in lowering
temperatures.

Latest NBM has dropped temps even colder. Coldest temps look to be
in the low 20s along the US 10 corridor with the mid to upper 20s
through most of the area. The warmest temps will be west of US 131
near the lakeshore. for these reasons have gone with a warning.

As the upper level ridge builds over the region expect clear and
dry conditions to continue through Thursday. Temperatures will
rebound with highs on Thursday in the upper 50s.

- Rounds of Precipitation in the Forecast Friday Night through Monday

An active spring time pattern is shaping up in the longer term of
this weekend into next week. A trough aloft will be replaced by deep
southwest flow as we head into the weekend...which means rounds of
precipitation. The first upper wave will swing through the region
Friday night into Saturday. At the surface a warm front will surge
through as well. Given a deep southwest flow plenty of moisture will
be available making both showers and thunderstorms likely. GFS and
ECMWF most unstable CAPE progs indicate values in excess of 1,000
j/kg. Rainfall amounts with this first event will likely be above a
half inch. Another rain event looks likely for Sunday into Monday as
we will be in the warm sector initially followed by a cold frontal
passage on Monday. Some shower activity may linger into Monday
night. We look mainly dry for Tuesday into Wednesday.

- Warmer Weather Expected This Weekend into Early Next Week

The deep southwest flow will bring much warmer air into the region.
850mb temperatures will largely be in the +10C to +14C range this
weekend into next week. Highs in the 60s and 70s are expected which
is well above normal highs which are around 60. In the warm sector
on Sunday its not out of the realm of possibilities to make a run at
80. The ECMWF MOS guidance actually has a high of 80 on Sunday at
GRR.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 108 PM EDT Wed Apr 24 2024

The MVFR cloud deck across Lower Michigan continues to erode with
the MVFR cigs about to clear GRR in the coming hour. All sites
will transition to VFR over the next few hours with skies clearing
out this evening. A few cirrus clouds pass through tonight before
skies clear fully again into tomorrow. Winds today will be from
the north at 5-15 knots becoming northeast around 5 knots into
Thursday as high pressure moves in.

&&

.MARINE...
Issued at 330 AM EDT Wed Apr 24 2024

 Small Craft Advisory remains in effect until 8 PM Wednesday.
Strong, downsloping northerly flow will continue through the
daytime. Winds will begin to have a northeasterly off shore component
this afternoon and will slacken late this afternoon. Winds and
waves should subside quickly Wednesday night into Thursday as
surface high pressure builds over the area.

Southerly flow should prevail over Lk MI through most of the
upcoming weekend as a warmer/more humid air mass arrives. It`s
quite possible the southerly winds will be strong enough to
require small craft advisories, at least at times. Other marine
threats over the weekend could include occasional thunderstorms
and areas of fog as dew points above 50 arrive atop chilly water
temps in the mid 40s.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Freeze Warning from midnight tonight to 8 AM EDT Thursday for
     MIZ043>046-050>052-056>059-064>067-071>074.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LMZ844>849.

&&

$$

UPDATE...Ostuno
DISCUSSION...Duke/Ceru
AVIATION...Thomas
MARINE...Ceru