000
FXUS63 KGRR 161603
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1203 PM EDT Tue Apr 16 2024

.KEY MESSAGES...

- Sunny this morning, showers/storms tonight

- Strong to severe storms possible Wednesday

- A Period of Rain Thursday Night

- Cooling trend into the weekend

&&

.UPDATE...
Issued at 1202 PM EDT Tue Apr 16 2024

Main update is that we are issuing a Wind Advisory from the GRR
area to the north and west in a zone that will have the potential
for gusts near and over 45 mph late this afternoon and evening.
Multiple high resolution models are showing gusts to potentially
50 mph. BUFKIT overviews via the 3km NAM also support strong wind
gusts this evening with 45 knots in the mixed layer.

High pressure will slide east away from the area this afternoon,
allowing us to become more under the influence of the low pressure
system in the plains. What that means for the afternoon and evening
is an increase in mid and high clouds. Precipitation should mainly
hold off until after 00z per the 12z HREF, but not out of the realm
of possibilities of seeing a few light showers down towards South
Haven towards dusk.

&&

.DISCUSSION...
Issued at 332 AM EDT Tue Apr 16 2024

- Sunny this morning, showers/storms tonight

High pressure over northwest Ontario will provide some sunshine
this morning before high clouds move in from the west this
afternoon. Low pressure over the Plains will move east today and
push a warm front in our direction.

There`s a weak signal for a few showers to develop around mid
afternoon over the southwest cwa before diurnal heating wanes and
the showers dissipate.

This system looks like it will produce two distinct precipitation
events. The first unfolds tonight after 03z as the warm front
noses into the region. Expect the usual elevated showers and
scattered storms. Any storms that develop will be aided by a piece
of vorticity that breaks off the main short wave over IA/MN.
MUCAPE around 700 j/kg point toward a thunder potential but not
severe storms. If we do see storms, it will be during round two on
Wednesday.

- Strong to severe storms possible Wednesday

The severe threat Wednesday is conditional on how worked over the
atmosphere is from any convection that occurs tonight and the
degree of recovery prior to the cold front moving through
Wednesday. Areas south of I-96 are the most likely to see stronger
storms as dynamics are stronger there.

Bulk shear increases to around 50 kts mid morning Wednesday ahead
of the occluding cold front. SBCAPE around 1000-1500 j/kg and a
mid level wind max nosing in from the southwest will help the
cause for stronger storms. The strong shear points toward the
potential for some organization and bowing segments.

Once the front moves east of the cwa during the late afternoon,
the precipitation will diminish.

- A Period of Rain Thursday Night

As a frontal zone approaches from the west later Thursday, a wave is
shown to develop along it while it tracks into MI.  FGEN in the DGZ
will lead to decent lift while upper level diffluence over the
frontal zones supports deeper lift.  A ridge of higher PWAT values
gets drawn into the front as well, supporting an increased potential
for some rain.  Ensemble QPF trends have been going up, but overall
amounts are looking light, generally under a quarter inch.

- Cooling trend into the weekend

A deepening mid level low in Ontario on Friday, lifts up to Southern
Hudson Bay and into Quebec for Saturday.  Northwest winds are shown
to exist westward through the Canadian Prairies which will act to
funnel the cooler air down into MI through the weekend.  Ensemble
temperature trends are lower so a chilly weekend is looking more
likely with time.  An increased potential for near or below freezing
overnight lows is looking more likely with time.  As for a warmup
next week, an Alberta Clipper is shown to be dropping down into the
Upper Plains Monday into Tuesday.  Thus we could see temperatures
drop or hold steady into mid week as this system passes by MI.  We
noted that the ensemble temperature trends for next week are lower
for the most part.  That decreases the potential for any significant
warmup.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 717 AM EDT Tue Apr 16 2024

The pressure gradient will be tightening up today and that will
lead to increasing winds. The low levels remain dry so conditions
will remain VFR during the day, but tonight conditions will
steadily moisten up leading to lowering ceilings. Some rain shower
activity is expected tonight. With weak instability, an isolated
thunderstorm or two is possible. Confidence for thunderstorms was
not high enough to put them in the forecast at this time. We did
add low level wind shear for several sites tonight as the low
level jet moves in increasing the potential for impacts.

&&

.MARINE...
Issued at 332 AM EDT Tue Apr 16 2024

As the strengthening low pressure in the Plains moves in this
direction today, surface winds will increase from the east. A
Small Craft Advisory is in effect south of Grand Haven from 18z
today through 10z Wednesday and will probably need to be extended
further into the morning. North of Grand Haven, A Small Craft
Advisory is in effect from 18z today through 02z when it`s
upgraded to a Gale Warning. This is generally a 6 hr window of
stronger winds over the northern nearshore zones during the
evening and early overnight hours. Once the gales subside after
10z, a Small Craft Advisory will likely takes its place.

&&

.FIRE WEATHER...
Issued at 1202 PM EDT Tue Apr 16 2024

We issued a Red Flag Warning earlier this morning after
coordination with the DNR. Red Flag Conditions will be present
today with highs into the 60s and 70s...increasingly windy
conditions and RH values that will dip into the 20-30 pct range.
Those conditions combined with already dry fuels (Very High Fire
Danger already) prompted the issuance of the Warning.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Red Flag Warning until 8 PM EDT this evening for MIZ037>040-
     043>046-050>052-056>059-064>067.
     Wind Advisory from 5 PM this afternoon to 2 AM EDT Wednesday for
     MIZ037>039-043>045-050-051-056-057.
MARINE...Small Craft Advisory until 6 AM EDT Wednesday for LMZ844>846.
     Small Craft Advisory until 10 PM EDT this evening for LMZ847>849.
     Gale Warning from 10 PM this evening to 6 AM EDT Wednesday for
     LMZ847>849.

&&

$$

UPDATE...Duke
DISCUSSION...MJS/04
AVIATION...MJS
MARINE...04
FIRE WEATHER...Duke