385
FXUS63 KGRR 290640
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
240 AM EDT Mon Apr 29 2024

.KEY MESSAGES...

- Cold Front brings rain/thunder on Monday

- Multiple Chances for Showers and Storms This Week

- Warm Temperatures Through The Saturday

&&

.UPDATE...
Issued at 1007 PM EDT Sun Apr 28 2024

Minimal instability remains south of the warm front tonight.
Mainly showers are expected overnight but some thunder can`t be
ruled out. A steadier batch of showers is indicated by the 00z
HRRR to arrive in the 06z-12z time frame. This activity is
currently located across eastern Missouri but will head our way
overnight. Looks like a wet morning commute especially along and
west of a Big Rapids to Battle Creek line.

&&

.DISCUSSION...
Issued at 352 PM EDT Sun Apr 28 2024

- Cold Front brings rain/thunder on Monday

Extensive cloudiness into this afternoon has so far muted any
strong updrafts, although a few showers and towering cu have
managed to form in the past couple hours across the southern half
of the forecast area. Cannot rule out a few strong storms into
early evening with deep layer shear values of 25 to 30 knots.
Breaks in the clouds and surface heating could overcome the
stabilizing influence of the extensive rain showers from last
night into this morning.

For tonight, we will watch whatever showers/storms are able to
develop but they should diminish after sunset as sfc based
instability diminishes, then look for showers and storms pushing
in ahead of the advancing cold front overnight into Monday
morning. Expect the bulk of those showers to come through between
roughly 8 AM and noon on Monday with the potential for some
stronger storms across the eastern forecast area as the airmass
destabilizes. Scattered showers persist along and behind the cold
front into Monday evening before drying works in from the west.

- Multiple Chances for Showers and Storms This Week

Tuesday will be the best chance for dry weather in the long term
portion of the forecast thanks to a surface ridge and upper-level
ridging forecast to move overhead. Ensemble probabilities have
trended downward with precipitation chances for the Tuesday night
into Wednesday timeframe due to questions on low-level moisture even
with a vorticity maximum swinging through. An isolated shower can`t
be ruled out north of M20 but given low confidence will leave the
dry NBM PoPs as is.

Showers and Thunderstorms more likely Wednesday into Thursday as a
surface low to our west lifts a warm frontal boundary across Lower
Michigan. Thursday could be the most active day of the long term
period as MUCAPE values increase near to above 1000 J/kg Thursday
afternoon in both ECMWF and GFS guidance with a 30-40 knot low-level
jet. A shortwave then swings through the area Thursday night into
Friday driving a front through keeping rain chances going.

Predictability in the longwave pattern decreases notably into next
weekend. While there are signals in cluster analysis and model
guidance for a trough to setup over the central United States by
next weekend, there is considerable variation in both the positioning
and amplitude of this feature.

- Warm Temperatures Through The Saturday

Highs in the 60s are expected for Tuesday as a weak thermal trough
quickly passes through the region. Temperatures warm for the mid to
late work week into the 70s, with the 80s not out of the question,
as southwest flow brings plenty of warm air into the Central Great
Lakes.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 241 AM EDT Mon Apr 29 2024

TAF sites are situated with a warm front along Interstate 96 and a
cold front upstream over Iowa. The I-96 TAF sites are located
right near the warm front and as such have been going in and out
of IFR conditions. The warm front will move a bit north and VFR
conditions develop and it drops south and 400 foot ceilings
develop. Model forecasts show the front pushing north this morning
so the IFR potential may just be for a few hours early this
morning 06Z to 10Z or so.

We will see some rain spread in from the southwest towards or
around 09Z to 10Z. Several hours of rain are expected at any one
TAF site, ending towards 16Z. VFR Weather should dominate after
that with the cold front sweeping through mainly dry this evening.

Winds will become southwest at 15 to 25 knots today after the
morning rain.

&&

.MARINE...
Issued at 352 PM EDT Sun Apr 28 2024

Webcams and satellite do not show any extensive areas of dense fog
over Lake Michigan this afternoon as winds have apparently been
able to prevent its formation. We will keep mention of patchy fog
in the marine zones for this evening.

Winds and waves increase Monday afternoon and a Small Craft
Advisory may be needed although conditions looks marginal.

&&

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

&&

$$

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