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000
FXUS63 KGRR 252030
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 PM EST Thu Feb 25 2021

LATEST UPDATE...
Synopsis/Discussion/Marine

.SYNOPSIS...
Issued at 330 PM EST Thu Feb 25 2021

- Mixed Precipitation late Friday into Saturday morning

- Warm Air Sunday then cooler Temps Monday

- Overall Warms Trend will continue through next week


&&

.DISCUSSION...(This evening through next Thursday)
Issued at 330 PM EST Thu Feb 25 2021

- Mixed Precipitation late Friday into Saturday morning


 The mild weather of today and tomorrow will give way to a robust
trough moving the the upper levels, brining a warm nose of air
out ahead of it.

 The models are in fair agreement in bringing this trough through
Friday night into Saturday.The biggest driver of this system will
be the isentropic lift with a nose of warm air out ahead of the
system. The rising temperatures overnight will bring mainly rain
to the south,though there could initially be some snow. There will
be a better chance of snow up north, however, due to the warm air
advection, there is some potential for freezing rain. Any
freezing rain will lift quickly northward, as does the system
which should exit southwest Michigan by Saturday afternoon.

 The latest runs continue to speed up the system and has lightened
up the QPF.  The latest EC has the best moisture between 06Z to
12Z which corresponds to the left exit region of an upper level
jet and the 500 mb vort max that will be traversing the northern
half of lower Michigan corresponding to the passing short wave
trough.

- Warm Air Sunday then cooler Temps Monday

In the wake of the aforementioned system there will be a warm up
Sunday which could bring max temperatures into the upper 40s and
potentially 50 all depending on the timing of the approaching cold
front.

 That cold front will correspond with another shortwave trough
swinging through the region Sunday night into Monday. This will
bring a return to colder temperatures and potentially some light
mixed precipitation. However the best moisture will be to the
north so any accumulations should be light.

- Overall Warms Trend will continue through next week

The wave of colder air will swing through Monday and Tuesday
though this will be short lived. The warm air will continue to be
the trend mid to late week and latest CPC trends continue to show
above normal temperatures in the 60 to 10 and 8 to 14 day
outlooks. Expect a melting of snowpack through this timeframe,
especially with any rainfall.


&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1253 PM EST Thu Feb 25 2021

Diurnal cumulus deck that is currently forming inland from Lake
Michigan around 2500ft AGL should lift to VFR levels abv 3000 ft
soon. Mainly clear/VFR conditions this evening expected to give
way to some patchy fog/stratus formation overnight into early
Friday, although confidence is low at this time in regards to the
coverage/extent of any lower vsbys/cigs.

For now have went with MVFR vsbys 06Z to 15Z Friday, but can`t
rule out some localized IFR or lower conditions during the Friday
morning rush period. Any fog/stratus that does form should mix
out toward 15Z Friday with VFR following. West-southwest winds
10-20 kts this afternoon becoming light to calm tonight, then
gradually increasing out of the south on Friday.


&&

.MARINE...
Issued at 330 PM EST Thu Feb 25 2021

Gusty flow will shift to the south and will increase on Friday
ahead of an approaching system. During that time, from Friday 18Z
to around 06Z Saturday, winds and waves could reach the 3 to 5
range north of Whitehall. The strongest waves however will be off
shore and as Saturday evening continues the winds will shift the
the east which will allow for the nearshore waves to decrease into
Saturday morning.

 Winds will shift to the west during the daytime on Saturday which
could allow for an increase of waves into marginal conditions
Saturday afternoon.

Ice shelves along the Lakeshore will continue to be unstable as
we see mild temperatures through the weekend and into next week.


&&

.HYDROLOGY...
Issued at 325 PM EST Thu Feb 25 2021

Overall conditions for the next week look nearly ideal for a slow
and steady melt, and the chances for widespread flooding are
decreasing. The big exception to this will be if any ice jams form
as the ice breaks up over the next few days.

Significant ice jams typically require a substantial increase in the
amount of water in the rivers to break the ice up before it`s had a
chance to weaken very much. Thankfully, with every day that goes by
this year the river ice is able to weaken more and more.
Nevertheless, this is the time of year when things can happen
unexpectedly on the rivers, so anyone living along or near our
beautiful West Michigan rivers should watch carefully over the next
week, and have a plan of action in case the waters do start to rise
rapidly.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

SYNOPSIS...Ceru
DISCUSSION...Ceru
AVIATION...Meade
MARINE...Ceru
HYDROLOGY...AD