Area Forecast Discussion
Issued by NWS Gaylord, MI

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607
FXUS63 KAPX 231449
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
949 AM EST Thu Nov 23 2017

.UPDATE...
Issued at 935 AM EST Thu Nov 23 2017

Band of low level moisture, partially lake augmented, still
producing areas of drizzle/freezing drizzle across portions of
northern lower Michigan. Seeder-feeder mechanisms from passing mid
level moisture resulting in mainly light snow/flurries for areas
north of the big bridge. Moisture expected to thin out as we head
through the day, ending the widespread very light precipitation. Not
seeing much evidence for any lake effect off Lake Michigan for this
afternoon, with an increasingly shallow convective boundary
layer...which is all warmer than -10c. Touch better conditions for
lake processes off Lake Superior, although even there shallow
convective boundary layer should keep snow shower coverage and
intensity limited.

&&

.NEAR TERM...(Today through Tonight)
Issued at 213 AM EST Thu Nov 23 2017

...Some lake snow showers today then quiet tonight...

High Impact Weather Potential...Minor additional accumulations of
lake effect snow today.

Pattern Synopsis/Forecast...High pressure remains centered south and
east of Michigan early this morning...extending from the Mid
Mississippi Valley thru the Ohio Valley into the Eastern Great Lakes
region. Meanwhile...a weak area of low pressure is making its way
eastward out of the Northern Plains toward the Western Great Lakes
region attm. Area of scattered light snow showers continues to
develop over Southern Wisconsin east of the low center in an area of
limited synoptic moisture and isentropic lift. Closer to home...
latest KAPX base ref loop combined with local obs suggest some
increase in mid level moisture/clouds...along with some lake clouds
streaming into locations impacted by SW low level flow. Otherwise...
no precip is occurring across our CWA attm.

Upstream low will steadily fill/weaken as it heads eastward thru
Wisconsin and Michigan today. Initial area of scattered snow showers
will slide south of our CWA this morning...diminishing as it does
so. Narrow area of limited synoptic moisture will combined with weak
over-lake instability to produce some lake enhanced snow shower
activity today...targeting mainly the Straits area and far Northern
and NW Lower Michigan under the direction of SW low level flow. Any
new snow accumulations will be relatively minor (i.e. an inch or
two) with the highest POPs focused on the Tip of the Mitt. High
temps warming into mainly the mid 30s will also limit snow
accumulations.

Narrow ridge axis will briefly build over Michigan this evening...
quickly pushing east of our state overnight. Southerly flow and low
level WAA will commence on the back side of the ridge axis as a
tight pressure gradient sets up ahead of strong low pressure
developing over South Central Canada. Mainly dry but mostly cloudy
wx is expected for today...with the exception of a few lingering
light snow showers across Chippewa county. Overnight lows will cool
back into the upper 20s for most locations.

&&

.SHORT TERM...(Friday through Saturday)
Issued at 213 AM EST Thu Nov 23 2017

...Active weather returns to start the weekend...

High Impact Weather Potential: Accumulating lake effect snow
possible Saturday-Saturday night.

Pattern Forecast: By Friday morning, nearly zonal flow aloft will
quickly be replaced by shortwave troughing as a well pronounced wave
and attendant surface low race across southern Canada Friday through
Friday night. Warm air advection will be underway across northern
Michigan throughout the day Friday with gradually increasing
precipitation chances Friday afternoon through Friday evening before
a cold front sweeps across the region. Post cold frontal passage,
much colder air is expected to spill into the area with lake effect
snow chances increasing as a result.

Primary Forecast Concerns/Challenges: PoPs Friday gradually
transitioning to lake effect snow chances as early as Saturday
morning.

Warm advection is firmly underway Friday morning with a narrow
window for a brief isentropically driven wintry mix to develop
across far northern locales, but by and large, the majority of
precip through early Friday afternoon should remain to our north
over Ontario. Precip chances, however, do increase from northwest to
southeast across the entire forecast area Friday mid-afternoon into
the evening (likely to fall as all liquid) ahead of the system`s
cold front set to cross the area Friday night.

Significantly colder temperatures to follow the frontal passage with
Friday`s highs in the mid 40s to low 50s falling to the 30s for high
temps on Saturday. In addition, over-lake instability is expected to
be sufficient for lake effect process to ramp up in the typical
northwest flow lake belts off of both Lake Michigan and Superior,
perhaps as early as early Saturday morning continuing through
Saturday evening. Guidance remains far from impressive with respect
to available moisture and synoptic support, along with anemic
inversion heights generally sub 5kft. Accumulations on the order of
an inch or two seem like a good bet, along with gusty winds creating
some concern for patchy blowing snow in spots.

.LONG TERM...(Saturday night through Wednesday)
Issued at 213 AM EST Thu Nov 23 2017

High impact weather potential: Minimal.

Any lingering lake effect snow activity gradually diminishes
Saturday night into early Sunday as heights rise aloft and low level
flow backs southwesterly around high pressure centered across the
Tennessee Valley. Above normal temperatures are anticipated to start
next week (highs in the 40s) before the next system spins up across
the central/northern plains...perhaps impacting northern Michigan as
early as Tuesday afternoon with initial liquid precip transitioning
to more frozen by Tuesday night-Wednesday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 600 AM EST Thu Nov 23 2017

Scattered lake effect snow showers will impact much of NW Lower
Michigan (PLN/TVC/MBL) today under the direction of low level W/SW
flow. Conditions will drop to MVFR within these snow showers. Snow
showers will end by this evening with solid VFR conditions
expected tonight. SW winds of 10 to 20 kts will become westerly
this afternoon...and will then back to the SW again later tonight.


&&

.MARINE...
Issued at 213 AM EST Thu Nov 23 2017

Winds and waves will continue to reach SCA criteria across our Lakes
Michigan and Huron nearshore areas generally thru the end of the
week. Some lake effect snow showers are expected today...mainly for
the Straits area and along our Lake Michigan nearshore areas under
the direction of Sw low level flow. Rain showers will develop Friday
and Friday night as warm moist are surges into Michigan ahead of an
approaching low pressure system.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 5 PM EST this afternoon for
     LHZ345>349.
LM...GALE WATCH from late tonight through Friday evening for LMZ323-
     342-344>346.
     SMALL CRAFT ADVISORY until 5 AM EST Friday for LMZ323-342-
     344>346.
     SMALL CRAFT ADVISORY until 5 PM EST this afternoon for LMZ341.
LS...NONE.
&&

$$

UPDATE...MB
NEAR TERM...MR
SHORT TERM...MG
LONG TERM...MG
AVIATION...MR
MARINE...MR



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