152
FXUS63 KGRR 281726
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
126 PM EDT Sun Apr 28 2024

.KEY MESSAGES...

- Showers and Storms Continue into Sunday and Monday

- Multiple chances for rain exist from Monday night and beyond

- Near to above normal temperatures continue this week

&&

.UPDATE...
Issued at 1001 AM EDT Sun Apr 28 2024

The POPs/Weather grids have been updated per the latest radar
trends and HRRR forecast. Steadier rain will lift north this
morning but the wavering surface front will remain across the
central forecast area as it has been reinforced by outflow from
this mornings showers. Partial clearing this afternoon across the
southern half of the forecast area could create enough sfc-based
instability to pop some storms, as indicated by the HRRR during
the late afternoon. This would most likely occur along the
residual outflow boundary/sfc front across the central forecast
area in the general vicinity of GRR to LAN.

&&

.DISCUSSION...
Issued at 356 AM EDT Sun Apr 28 2024

- Showers and Storms Continue into Sunday and Monday

A surface low ejecting out of the southern plains will carry a warm
frontal boundary into lower Michigan today. This front will stall
over central lower this afternoon keeping showers mainly north of I-
96. Though the bulk of the instability will be mainly south of the
frontal boundary and convection, storms will be possible. Severe
weather does not look likely. HREF probability matched mean
values continue to advertise local patches of 1 to 1.5 inches of
rain from now to Monday morning, suggesting some training of
storms may be possible.

The upper trough associated with the surface low to our west moves
into Ontario providing better upper support for an approaching cold
front. Widespread showers encompass the CWA Sunday night and Monday.
Storms will be possible as modest instability ahead of the front
builds with bulk shear values up to 35 to 45 knots. Showers exit
east late Monday leading to a dry Tuesday.

- Multiple chances for rain exist from Monday night and beyond

The upper system responsible for our chances for rain this weekend
exits the Great Lakes into Canada Monday night. The rain will end
Monday evening and we will be dry the remainder of the night and
through Tuesday. A vort lobe pivots through the Great Lakes Tuesday
night into Wednesday morning with another chance for rain. This
chance for rain appears to be quite light as the upper system is
located well west of the area.

Another active weather period looks to be Thursday into Saturday as
an upper trough moves into and through the area. Showers and
thunderstorms are both in the forecast during this time frame as
surface dew points surge into the 60s F. Most unstable CAPE values
reach the 1000-2000 j/kg range on Thursday which could be the most
active weather day of the upcoming work week. Bottom line the 7 day
forecast remains active and wet with WPC QPF values through next
Sunday morning on the order of 1.00 to 2.00 inches.

- Near to above normal temperatures continue this week

Normal highs are in the lower 60s this time of year and we are
forecast to be above that through the the 7 day forecast. The
warmest day of the period will be Thursday where we could hit 80
along I-94.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 126 PM EDT Sun Apr 28 2024

The shield of MVFR clouds affecting all TAF sites at present will
make its way north over the next few hours bringing all sites to
at least low VFR. Tonight the I96 TAF sites drop back to MVFR with
some IFR possible at MKG (but to low confidence to include IFR in
the TAF) because of the warm frontal boundary that will remain
draped across the area. Multiple chances for showers and storms
are expected the next 24 hours including a low chance for
thunderstorms this afternoon. Enough confidence for VCTS at GRR
and MKG but all other sites did not have the confidence at this
time. Additional showers overnight will affect MKG and GRR and
bring patchy fog potential to these terminals. Moisture increases
Monday morning bringing MVFR potential back to AZO and BTL and
showers possible but just low enough confidence in affecting the
terminals to leave out at present. Winds today and tomorrow will
be 10-15 knots gusting to 20 at times and 7-12 knots overnight.

&&

.MARINE...
Issued at 356 AM EDT Sun Apr 28 2024

A moist airmass remains in place today and Monday with dewpoint
values into the mid to upper 50s. This moist air over cold water
will produce dense fog along the lakeshore, therefore a Marine Dense
Fog Advisory is in effect. Meanwhile, winds and waves should stay
low through today and much of Monday. A cold front will approach the
area late Sunday into Monday and may bring hazardous wind gusts as
well as showers and storms.

&&

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

&&

$$

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