Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 201134
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
634 AM EST Mon Nov 20 2017

.NEAR TERM...(Today through Tonight)
Issued at 255 AM EST Mon Nov 20 2017

High impact weather potential: None.

Pattern synopsis and forecast:

Lake effect snows across nrn Chippewa county were just scraping nrn
Chippewa county early this morning, as winds have backed to almost a
due west direction. They will come to a complete end over the next
few hours, as winds continue to back to out of the SW, and warm
advection gradually kills all but some shallow overlake instability.
There was a batch of flurries that was developing over NW lower
Michigan, seemingly associated with a weak increase in DPVA and LLJ
in the WAA. Further upstream, a more defined shortwave trough and
associated low pressure was pushing through Saskatchewan, and was
working with minimal moisture, and was producing little to no
synoptic precipitation.

Heading through this morning, the lake effect will push north out of
Chippewa county, while a period of stratus may develop over Lake
Michigan, with shallow moisture flux increasing due to strengthening
winds and that shallow overlake instability. Also, the batch of
flurries is expected to end as they track NE, after the passage of
weak vorticity and the DPVA. The Saskatchewan shortwave will be
pushing ESE and eventually into the western Great Lakes by late
tonight, while the associated low pressure crosses into Ontario and
it`s cold front laying out across nrn Michigan. Skies will just be
increasing in higher level cloud today and into this evening,
particularly in the nrn CWA, and then over all of nrn Michigan by
late tonight. Again, this wave will be working with minimal
moisture, and not much moisture advection out ahead of it. Doubt
there will be any precipitation, despite much stronger DPVA and
frontal forcing.

&&

.SHORT TERM...(Tuesday through Wednesday)
Issued at 250 AM EST Mon Nov 20 2017

...Another shot of cold air and lake effect snow return Tuesday...

High Impact Weather Potential: Accumulating snow possible Tuesday
afternoon through early Wednesday, primarily in the typical lake
belts of northwest lower and eastern upper.

Pattern Forecast: Weak ridge axis aloft is expected to cross the
western Great Lakes on Monday along with high pressure centered over
the Tennessee Valley nosing into the region from the south. However,
changes are in store for the Tuesday-Wednesday time frame as a well-
defined shortwave and attendant developing surface low pressure trek
from British Columbia to near the arrowhead of Minnesota by Monday
afternoon and into Ontario Monday night-early Tuesday. This will
ultimately drag a cold front across northern Michigan Tuesday
morning with another shot of cold air renewing lake effect snow
chances Tuesday afternoon through Wednesday morning.

Primary Forecast Concerns/Challenges: Minimal shower threat
along/ahead of Tuesday morning`s cold front before quickly
transitioning to lake effect snow chances/amounts Tuesday afternoon
through Wednesday morning.

Potent cold front tied to low pressure over central Ontario is
expected to be making its way southeastward across the forecast area
come Tuesday morning, which could be accompanied by an isolated A.M.
shower or two, but by and large, most of the area is expected to
remain precip-free. The same can`t be said for the afternoon as
another shot of cold Canadian air will quickly spill back into the
region. Pre-frontal H8 temps near 0 C are expected to quickly fall
to -8 to -11 C by mid-afternoon. Thus, over-lake instability (delta
Ts pushing 20 C) combined with several weak perturbations within the
parent trough are expected to become sufficient for northwest flow
lake processes to ramp up. Tightening pressure gradient on the
backside of aforementioned low pressure will also result in gusty
winds at times...pushing 20 mph inland/25 mph in coastal areas.

No glaring reason for snow shower activity to diminish Tuesday
night; however, by early Wednesday morning, the loss of any
lingering synoptic support/moisture coinciding with weak mid level
warm air advection and heights gradually rising aloft should begin
to transition any lingering light snow to more westerly oriented LES
zones before diminishing across the bulk of northern MI by midday.

In terms of potential snow accumulation between Tuesday afternoon
through Tuesday night, northwest flow favored locales of eastern
upper and northwest lower stand the best chance to see 1-3 inches of
fresh powder...particularly across northern Chippewa and sections of
Charlevoix, Antrim, Otsego and Kalkaska counties. Lesser amounts
elsewhere, and amounts will certainly become more refined over the
next 24 hours. As was alluded to by the prior shift, the combo of
freshly falling snow and occasionally gusty winds may result in
slick travel for some and as of right now, a low chance of another
round of headlines.

.LONG TERM...(Wednesday night through Sunday)
Issued at 250 AM EST Mon Nov 20 2017

High impact weather potential: Light snow showers possible Thursday
with more rain/snow chances this weekend.

Next threat for precip arrives Thanksgiving day in the form of light
snow showers tied to a cold front expected to swing across northern
Michigan. At this point, it doesn`t look to pack too much impact,
but worth monitoring with busy holiday travel underway.

Warm air advection ramps up across the region late Thursday night-
Friday ahead of the next system expected to bring rain/snow to the
area Friday night into Saturday. All signals point toward yet
another shot of much cooler air arriving into northern Michigan for
the second half of the upcoming weekend with potentially another
round of accumulating snow.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 634 AM EST Mon Nov 20 2017

VFR. LLWS Monday night.

Mid and high clouds were crossing the region early this morning,
along and ahead of a developing warm front in the western Great
Lakes. While conditions will prevail at VFR, there is some
opportunity for a period of MVFR CIGS at TVC/PLN/APN at times
today due to shallow overlake shallow instability and increasing
winds shifting from W to SW. A cold front arrives late in the TAF
period and will shift gusty winds more west then NW into Tuesday
with lake effect kicking in again.

The SW winds today will increase considerably just off the
surface for tonight, leading to LLWS at PLN/TVC/MBL.

&&

.MARINE...
Issued at 250 AM EST Mon Nov 20 2017

A brief weakening in wind speeds is occurring attm, with some rogue
advisory level winds still out there on the nearshore waters. Winds
quickly ramp back up again through today and tonight, out ahead of
low pressure tracking into Ontario. Winds will remain strong through
Tuesday behind the passage of a cold front, weakening but remaining
gusty into Tuesday night as a weaker pressure gradient starts moving
in. Gale force winds will develop tonight into Tuesday morning on
Lake Michigan, and possibly other areas, but advisory level winds
are at least a lock. Lake effect rain and snow develops behind the
cold front, turning to all snow late Tuesday into Tuesday night.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 6 AM EST Wednesday for LHZ345>349.
LM...GALE WARNING from 6 PM this evening to 11 AM EST Tuesday for
     LMZ323-341-342-344>346.
LS...SMALL CRAFT ADVISORY until 6 AM EST Wednesday for LSZ321-322.
&&

$$

NEAR TERM...SMD
SHORT TERM...MG
LONG TERM...MG
AVIATION...SMD
MARINE...SMD


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