337
FXUS63 KAPX 132346
AFDAPX
Area Forecast Discussion
National Weather Service Gaylord MI
646 PM EST Thu Feb 13 2025
.KEY MESSAGES...
- Accumulating west/northwest flow lake effect snow tonight with
areas of low visibility and slick roads.
- More snow for this weekend...starting Friday night.
- Turning colder for Monday along with lake effect snow showers
(the unrelenting winter continues ad nauseam).
&&
.SHORT TERM /THROUGH FRIDAY/...
Issued at 346 PM EST Thu Feb 13 2025
Pattern Synopsis: Upper low continues to slide east tonight as mid
level ridge pushes toward the western lakes. Lake effect snow
tonight, diminishing late tonight with lowering inversions and drier
air arriving.
Forecast Details: A favorable window for lake effect snow in
west/northwest flow areas for late afternoon into the first half of
tonight as a mid level shortwave slides across the area. Very good
LES parameters: 80+% RH in the 850-700mb layer, inversion heights of
7-8k and forcing focused within the DGZ. The window of favorable
parameters is relatively short, as the environmental conditions
become more hostile after midnight as the upstream ridge axis
approaches with rising heights, lowering inversions and drier mid
level air. Deeper moisture and better low level convergence signals
in northwest parts of Chippewa County (mainly north of M-123) will
result in 3 to 5" of snow by Friday morning. Over northwest lower,
1-3" in the favored snowbelts with localized higher amounts
possible. Snowfall amounts generally below advisory criteria but
some impact to travel with areas of low visibility/blowing snow
around some of the heavier snow showers. Will issue an SPS and
handle potential impacts with graphics. Lows in the single digits
(below zero eastern upper) with wind chill readings below zero.
Friday should be a relatively quiet weather day during the daylight
hours. Possibly some lingering snow shower activity toward
Whitefish Point in eastern upper to start the day but that should
push northward during the morning as winds back in advance of the
next system. Likely some sunshine during the first half of the day
for most locations with increasing and thickening clouds during the
afternoon. Any snow associated with our next system should hold off
until evening. Highs in the 20s but it will feel more like the
single digits at times given the wind.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 346 PM EST Thu Feb 13 2025
Pattern Forecast: Strongly -NAO pattern with a strong blocking
ridge over Greenland bridging across the pole to another strong
height anomaly north of Alaska. This has split the polar vortex
into two separate lobes...one of which is centered along the
western shore of Hudson Bay. Long wave trough axis extends south
into the southern Plains...getting pushed east by another
potent short wave trough heading into California. Colder/drier
air spreading into the upper Lakes in the wake of yesterday`s
snow event...with cold high pressure spanning the Plains and
extending into northwest Ontario.
Long term period starts Friday night with high pressure having
shifted from the central CONUS to the east coast...with lee
cyclogenesis over Kansas/Oklahoma as Pacific short wave trough moves
through the desert southwest. In between southerly return flow
brings warm air and moisture northward and sets up the next round of
accumulating snow across Michigan for Friday night into Saturday
night. Cyclone over Oklahoma/Kansas Saturday morning will swing up
through the Ohio Valley Saturday night and track into New England
Sunday. Tightening pressure gradient as the low draws closer and
deepens should result in an increase in winds Saturday night and
colder air getting pulled in for Sunday/Monday.
Primary Forecast Concerns:
More snow for this weekend...starting Friday night: Evolution of
snow event for this weekend the main forecast issue...and this looks
somewhat drawn out though the details will depend on mid level
evolution of the system (wrapping moisture back across northern
Michigan for the latter half of the weekend). At the very least
snow is expected to develop/propagate into the forecast from the
southwest Friday evening...there are indications of a wedge of dry
air above the boundary layer that will need to be saturated before
things can really get going. So heavier QPF will be overnight into
Saturday. Some curiosity about lake enhanced potential in southeast
trajectory off Lake Huron Saturday which would target Drummond
Island/southeast Chippewa county initially...and eventually into
northeast Lower Saturday night as winds back more easterly. Will
hint at this idea in the snowfall forecast. Current thinking is
that snow intensity (and perhaps coverage) will wane Saturday night
with the exception of northeast Lower with potential for continued
enhancement off Lake Huron. South be a north-south gradient in
QPF...and an opposite gradient in snow-to-liquid ratio with
decreasing ratios over time as warmer air continues to advect north.
So with all of that...current 36h snowfall totals (00Z Saturday-12Z
Sunday) range from 5-8 inches east of I-75 in northeast Lower...4-7
inches west of I-75...and 3-6 inches across eastern Upper with
highest amounts around the mouth of the St. Mary`s River. So
looking at this point at potentially a solid advisory event...did
mull issuing a watch east of I-75 but held off; probabilities of
exceeding warning criteria snowfall roughly 30-50 percent for areas
east of US-131/south of M-68 (where warning criteria is 7"/24h).
Light snow will likely continue to wrap back into northern Michigan
on Sunday.
Turning colder for Monday along with lake effect snow showers (the
unrelenting winter continues ad nauseam): In the wake of the weekend
system another shot of lake modified Arctic air will spill across
the upper Lakes. Still looking at some potential for single digit
highs Monday though forecast has trended slightly warmer...but
double digit below zero wind chills are still in the cards Tuesday
morning. Of course this will be accompanied by lake effect snow
showers in northwesterly flow...though 850mb temperatures below -20C
will have impacts on snowflake size. But will worry about the
details on this later.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 635 PM EST Thu Feb 13 2025
MVFR to IFR producing lake snow showers will gradually come to
an end this evening. Rest of the period will be dominated by VFR
conditions, with both rising cig heights and a scattering out of
clouds. High level clouds will be on the increase on Friday. No
significant wind concerns through the period.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 7 AM EST Friday for LHZ347.
Small Craft Advisory until 5 PM EST Friday for LMZ344>346.
&&
$$
SHORT TERM...JK
LONG TERM...JPB
AVIATION...MSB/JK
NWS APX Office Area Forecast Discussion