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000
FXUS63 KGRR 200525
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
125 AM EDT Sat Apr 20 2024

.KEY MESSAGES...

- Cold stretch; low temps near to below freezing

- Increased fire weather and freeze potential next week

- Chance of showers or storms Tuesday

&&

.DISCUSSION...
Issued at 336 PM EDT Fri Apr 19 2024

- Cold stretch; low temps near to below freezing

Upper troughing/deep cyclonic flow will maintain chilly conditions
over the weekend, with H8 temps bottoming out around -8C Saturday
morning. The incoming air mass is quite dry with dew points
falling into the lower 20s and the main concern is the risk of
freezing temps with blooming vegetation now more vulnerable.

As of today we will begin frost and freeze headlines as necessary
for all but the northern row of counties in the GRR CWFA. See the
latest Public Information Statement (PNSGRR) for more info.

For tonight the risk of a frost/freeze is marginal since the
winds stay up around 10 mph for most of the night plus we may see
some clouds floating in related to a shortwave pivoting in from
the northwest. Given expected low temps mostly 33-35 (inland from
Lk) and any dips to 30-32 more localized/brief, will not issue a
freeze warning tonight. This was coordinated with the DTX office.

After highs only in the mid 40s on Saturday, a better chance for
a freeze exists on Saturday night when winds should be a bit
lighter and guidance temps are a few degrees colder.


- Increased fire weather and freeze potential next week

Fuels (dead or drying live vegetation) will become more prone to
spreading fires as dry and breezy daytime conditions continue into
Sunday and Monday. Sunday may be on the cusp of Red Flag Warning
conditions in mid-Michigan.

On the nighttime side, Sunday night will be another to be on guard
for sub-32 degree temperatures. Just before milder air returns for
Monday and Tuesday, the ridge of surface high pressure will be over
Michigan Sunday night, which should allow winds to go light or calm
under clear skies. This may be a freeze setup that is easier to
mitigate given the calm winds and a sharp temperature inversion
forming in the lowest 100 feet above ground (cold air settling at
ground level with warmer temperatures above).

Wednesday night also has the potential to bring an impactful freeze
with high pressure moving over post-cold-front. The magnitude of the
cold air is still questionable among the model ensembles, as it
depends on whether the core of coldest air from the Hudson Bay
region spills into Michigan or is routed farther to our northeast.

- Chance of showers or storms Tuesday

An upper-level low in the lee of the Canadian Rockies on Monday
opens up into a trough as it progresses east-southeast toward
Michigan on Tuesday. Showers are likely to develop in the vicinity
of a surface cold front. The amount of instability available for
thunderstorms is not settled among the ensembles, but enough for a
mention of a chance of a thunderstorm.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 121 AM EDT Sat Apr 20 2024

Broken to scattered VFR clouds will continue to flow in from the
northwest into tonight. It`s possible that an isolated -rw/sw
occurs during this time but the forecast coverage does not warrant
including them in the forecast at this time. Gusty winds will
continue for the remainder of the night and into Saturday. The
general flow will be from the west northwest. The pressure
gradient weakens slightly tonight so we will allow for the winds
to drop off during the late afternoon into evening hours.

&&

.MARINE...
Issued at 336 PM EDT Fri Apr 19 2024

Brisk westerly flow of 15-25 kts and waves 3-6 ft will persist
tonight and Saturday so the Small Craft Advisory has been extended
through the end of the day Saturday. Conditions should fall a bit
below criteria Saturday night but may come up again to advisory
levels on Sunday. Hazardous winds and waves also look possible
Monday through Wednesday as the next weather system impacts the
area.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 6 PM EDT this evening for LMZ844>849.

&&

$$

DISCUSSION...Meade/CAS
AVIATION...
MARINE...Meade