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000
FXUS63 KGRR 262325
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
725 PM EDT Fri Apr 26 2024

.KEY MESSAGES...

- Showers and Thunderstorms Tonight

- Slight Risk of Severe Weather Saturday evening

- Multiple Rounds of Showers and Storms Through Mid Week

&&

.DISCUSSION...
Issued at 325 PM EDT Fri Apr 26 2024

- Showers and Thunderstorms Tonight

An area of isentropic ascent in strong warm advection pattern is
bringing showers and embedded thunder into northern Illinois this
afternoon and this will be moving northeast through Lower Michigan
tonight. The storms are expected to remain elevated overnight. By
Saturday morning the steadier rain is done with just isolated
showers through the day as the warm front will focus shower
activity north of the forecast area.

- Slight Risk of Severe Weather Saturday evening

Convection will be limited across much of the forecast area
through Saturday afternoon under shortwave upper ridging, with a
capping inversion noted in model soundings, but we will have to
watch the northwest zones for initiation of convection during the
evening along a prefrontal trough aligned across central or
northern Lake Michigan. There is 30 knots of shear present in this
area along with 500 to 1000 J/kg of CAPE, so any convection that
initiates could become organized enough to present a severe
threat. Main threat at this point would be hail and isolated wind.

There could be an isolated tornado threat with some model
guidance showing potential for a triple point low across the
northwest zones during the evening.

- Warm With Multiple Rounds of Showers and Storms Through Mid Week

Additional showers and storms are likely Sunday into Monday
associated with forcing from an upper-level jet streak and aided by
a frontal boundary sitting across northern Michigan and a shortwave
from the parent trough ejecting through the region. Convection will
be favored across Central Lower for our CWA closer to the warm
frontal boundary, with MUCAPE values north of 500 J/kg suggesting
there will be an attendant thunder risk. SPC currently has us in
general thunder which is reasonable given that the favored region
instability is separated from deep later shear and the highest
likelihood of showers/storms.

Widespread showers then expand into the remainder of the CWA Sunday
night and continue into early Tuesday as a cold front drifts across
the area. MUCAPEs suggest thunder chances continue. Rainfall by the
time all is said and done Monday night looks to be from 0.3-0.4
inches in the southeast CWA to 1-1.5 inches up towards Ludington.

Dry conditions then take over later Tuesday. as a high pressure
system quickly pushes through the area. Conditions then become more
active Wednesday as we see a cold front driven through Lower
Michigan by a northern stream shortwave followed by additional rain
chances into Thursday as a surface low ejects north into the upper
Ohio Valley.

Temperature wise, highs in the 70s are expected to continue into mid
week. By late week, expect highs to fall back to near normal in the
60s as a thermal trough slides into the central Great Lakes.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 725 PM EDT Fri Apr 26 2024

Showers will continue to gradually develop from southwest to
northeast across the area through the mid to late evening hours.
Conditions will start out VFR but will gradually deteriorate to
primarily MVFR overnight due to lowering cigs and steadier rain
showers. Isolated thunderstorms may develop overnight with the
relatively best chance for a storm coming after midnight through
around daybreak.

SE winds will stay up around 15 to 20 kts with higher gusts to
around 25 kts overnight. MVFR cigs are likely to linger Saturday
morning before gradually improving to VFR in the afternoon. Southerly
winds will stay up at around 15 to 25 kts Saturday. A few showers
and storms may develop late Saturday afternoon and early evening
but there is not enough potential for it to include mention in any
of the terminal forecasts. The better chance for rain and convection
will hold off until after 00Z Sun.

&&

.MARINE...
Issued at 325 PM EDT Fri Apr 26 2024

Hoisted a Small Craft Advisory for later tonight through Saturday
night. Southwest winds should hit 25 knots and perhaps 30 knots at
times. Marine fog is possible as well with dew points in the mid
to upper 50s although the winds may be able to mix out the
inversion and disperse the fog to some extent.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 2 AM Saturday to 8 AM EDT Sunday for
     LMZ844>849.

&&

$$

DISCUSSION...Ostuno/Thomas
AVIATION...Laurens
MARINE...Ostuno