484
FXUS63 KGRR 261058
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
658 AM EDT Sun Apr 26 2026
.KEY MESSAGES...
- Quiet weather expected into Monday afternoon
- Chances for showers and thunderstorms Monday night
- Cooler and mainly dry latter half of work week
&&
.DISCUSSION...
Issued at 358 AM EDT Sun Apr 26 2026
- Quiet weather expected into Monday afternoon
High pressure will bring quiet conditions both today and tonight.
Low clouds should lift and scatter out in the midday hours leaving
partly to mostly sunny skies. High clouds will begin to filter in
from the west this evening a precursor of more impactful weather
to come Monday evening and Monday night. Temperatures will be
above normal for highs both today and on Monday. 60s today and 70s
on Monday will be above seasonal norms.
- Chances for showers and thunderstorms Monday night
A positively tilted upper trough will extend from the Canadian
Prairies on Monday extending southwestward through California. A
shortwave will eject out of this western U.S. trough and emerge in
the Plains tonight. The upper shortwave and its associated
surface reflection will take aim on Wisconsin on Monday. The low
will be a fairly stout 993mb low which will lift a warm front into
Southwest Lower Michigan Monday afternoon and evening followed by
a cold frontal passage late Monday night. An active period of
weather will occur from Monday afternoon through Tuesday morning
with rounds of showers and thunderstorms. Severe weather is
possible.
We are in a SPC Marginal risk for severe weather and given the
wind fields this is reasonable. If instability trends upward, so
will our severe weather risk. 850mb low level jet speeds average
around 60 knots with a speed max in the mid levels pushing 70-80
knots. We are not lacking for deep layer shear (60-70 knots in the
0-6km layer). Models have remained consistent in showing 60F
surface dew points and PWAT values of 1.5 inches. So plenty of
moisture to work with. Models have remained resolute in the fact
that instability will hold at very modest levels...500 to 1,000
j/kg. Given the push of rain/widespread showers and thunderstorms
it is not out of the question that this is more of a rain producer
than a severe weather producer. The lack of instability is the
concern. The items that are going for at least some severe weather
though are 1) the potent upper wave and 2) strong wind fields.
Not a slam dunk threat for severe, but we will be monitoring. We
will know more as the system comes into the HREF and NadoCast
forecast windows with the 12Z runs. Stay tuned...
- Cooler and mainly dry latter half of work week
A secondary wave looks to pass by Lower Michigan on Wednesday on
the southeast edge of the upper trough moving into the Great
Lakes. We look to have rain showers moving through a decent
portion of the forecast area. Beyond Wednesday conditions should
be mainly dry Wednesday night through Saturday. It will be cooler than
normal with highs trending back into the 50s. 850mb temperatures
will be in the zero C to -5C range late in the upcoming work
week. Frost and freeze wording will reappear in our discussions
and forecasts for Wednesday night, Thursday night and Friday
night.
&&
.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 658 AM EDT Sun Apr 26 2026
Low clouds are moving from east to west across Southwest Lower
Michigan at 12Z. These clouds should clear all of the TAF sites by
15Z. We expect VFR weather to then prevail the remainder of the
day and tonight. Tonight high clouds will spread in from the west.
Winds will be easterly at 5-15 knots today.
&&
.MARINE...
Issued at 358 AM EDT Sun Apr 26 2026
Surface high pressure sprawls across much of Ontario and Quebec
this morning with ridging extending southwestward into the Great
Lakes region. This setup will largely remain the case both today
and tonight. This means a continued easterly offshore flow with
limited wave action. Waves should be 2 feet or less through
daybreak on Monday.
Things change on Monday as the high pulls away to the east and
developing low pressure in the plains takes aim at the Western
Great Lakes. In fact a deep low, 990-995mb, will lift northeast
through Wisconsin Monday night. The pressure gradient tightens on
Monday and reaches a peak Monday night. Monday we will see
southeast winds increase to 30 knots with the chance for gale
force winds Monday night out of the south. Waves will steadily
increase Monday and Monday night with waves in excess of 6 feet
likely north of Grand Haven. Will hold off on marine headlines at
this point, but they will be needed going forward.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Duke
AVIATION...Duke
MARINE...Duke
NWS GRR Office Area Forecast Discussion
