743
FXUS63 KGRR 190135
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
935 PM EDT Fri Apr 18 2025
.KEY MESSAGES...
- Warm with periods of showers/storms tonight
- Another wet and breezy system Sunday through Monday
- Mild with small chances of rain Tuesday through Thursday
&&
.UPDATE...
Issued at 930 PM EDT Fri Apr 18 2025
The radar is starting to perk up again as expected. Storms that
fired over Wisconsin along the cold front have moved
northeastward, crossed the lake, and are now moving over the
northwest cwa. The cores in these storms are a bit more robust
than earlier today and may end up being a bit stronger too. It`s
still possible we could see a severe storm or two with 1 inch
hails and wind gusts to 60 mph. GRR VWP shows 50 kts at 4k ft and
a stronger storm could bring that down to the surface.
The cold front remains to the west and the thunder threat will
continue tonight until the front moves across the cwa, which will
come after midnight.
No big changes to the forecast, but tweaked the PoPs a bit timing
wise.
&&
.DISCUSSION...
Issued at 340 PM EDT Fri Apr 18 2025
- Warm with periods of showers/storms tonight
Low confidence forecast with respect to severe weather potential
and coverage this evening. Warmer, more humid air continues to
flow in from the south with temps in the 70s and dew pts in the
mid to upper 50s. Despite lingering cloud cover, some sfc based
cape is now developing south of I-96 and that is expected to grow
and expand farther north with time through this evening. However
RAP guidance continues to show 200-300 J/KG of CIN persisting for
several hours.
Mid level lapse rates of 8-9 C/KM are present over srn Lwr MI so
if the cap can be broken by either the shortwave approaching from
the southwest and/or the cold front slowing leaning in from the
northwest then strong to severe storms could quickly develop.
Large hail and damaging winds are the main threat. Will have the
highest pops early this evening north and west of a MKG to MOP
line, expanding/moving south and east with the slow moving cold
front through the night.
Shower and storm threat ending late tonight or Saturday morning
as the cold front settles south of the state but considerable
cloudiness lingering, especially south.
- Another wet and breezy system Sunday through Monday
Shower potential ramping up again later Sunday and Sunday night
as wound-up low tracks from the Plains toward Wisconsin. Best
shower and storm potential should be 06Z-18Z Monday when the sfc
occlusion and negative tilt upper trough is swinging through,
although some wrap-around showers will linger in the cold
advection Monday afternoon and night. Another aspect from this
system will be winds; with brisk easterly flow preceding it and
strong westerly flow on the back side.
- Mild with small chances of rain Tuesday through Thursday
Tuesday and beyond features occasional (but for now low) shower
chances with ripply zonal flow aloft and decent baroclinicity
overhead/nearby. There are no major cold intrusions shown and
temperatures for the mid to late week period are expected to be a
bit above normal.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 730 PM EDT Fri Apr 18 2025
Additional convection and LLWS are the concerns tonight.
A cold front in western IL will move east this evening and another
round of showers/storms are possible late this evening and the
early overnight. LLWS remains a concern this evening due to the
presence of a strong low level jet aloft. Once the cold front
moves through, there may be a brief period of IFR cigs before
conditions improve to MVFR after 09z.
Cigs will slowly but steadily lift throughout the day Saturday.
&&
.MARINE...
Issued at 340 PM EDT Fri Apr 18 2025
We`re seeing a lull in winds and waves currently but will keep
the small craft advisory going into Saturday morning since the
cold frontal passage tonight will bring a period of increased
northerly winds. Occasional thunderstorms are also expected over
Lk MI tonight.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 11 AM EDT Saturday for LMZ844>849.
&&
$$
UPDATE...04
DISCUSSION...Meade
AVIATION...04
MARINE...Meade
NWS GRR Office Area Forecast Discussion
