Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 141844
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
144 PM EST Sun Jan 14 2018

.UPDATE...
Issued at 1109 AM EST Sun Jan 14 2018

Morning surface analysis/satellite imagery reveals elongated
surface ridge axis stretching from the Gulf up through the eastern
Great Lakes region. Upstream deepening short wave trough is
dipping down through the Manitoba/Ontario region with an
associated surface low just crossing the U.S./Canadian border into
western Minnesota. That is our weather maker for later tonight
through Monday.

Meanwhile...low level flow has backed southwesterly over the last
several hours as anticipated...pushing residual lake snow showers
up the Lake Michigan coastline into the straits/Mackinac county.
One healthier lake band has emerged just offshore and extends up
into western Mackinac county...and also still scraping the
shoreline areas from Manistee to Frankfort (FKS was at 3/4SM as of
1015 am). Some additional light snow showers and flurries are also
spreading northeastward in off Lake Michigan...down around the
Grand Rapids/Muskegon area.

Rest of today/tonight...Upstream short wave trough expected to
further deepen and eventually close off while migrating into the
upper Midwest by Monday morning. This system will spread some
light snowfall W-E across the CWA overnight tonight. But main
impact/forecast concerns will be with the evolution of ongoing
lake effect snow. Low level mean flow will continue to back SW->S
this afternoon and eventually southeasterly by Monday morning...
with some of the heavier lake effect cloud/snow shower banding
migrating across western Mackinac county in the process. Given
the cold thermal profile/lower snow->water ratios...snow showers
are still very efficient and substantially reducing VSBYS as
evidenced by FKS ob. So despite relatively lighter anticipated
snow accumulations...am pondering whether or not we need a winter
weather headline through this evening. An SPS at minimum...talking
about low VSBYS in snow showers. Will continue to monitor.

Elsewhere away from the lakes...morning cloud cover should thin
out a bit across interior parts of the CWA (already sunny in NE
lower MI). However...satellite trends suggest that we see a fair
amount of the cloud cover that is downstate right now spread up
into the region this afternoon. Possibly even some flurries as
daytime heating gets involved.

&&

.NEAR TERM...(Today through Tonight)
Issued at 327 AM EST Sun Jan 14 2018

...Continued Cold with chances for snow...

High Impact Weather Potential...Some reduced visibility due to lake
snows near Whitefish Bay and portions of northwest Lower Michigan
this morning. Then, widespread snows begin Sunday night and Monday.

Primary Forecast Concerns...Lingering snowfall over east Upper
Michigan this morning, along with snowfall associated with system
moving into the region to begin the upcoming work week.

Pattern Synopsis/Forecast...The Broad upper trough which settled
over the eastern two thirds of the country Friday and Saturday, will
remain anchored over the Great Lakes through the remainder of the
weekend. Mid level temps in this 500mb trough will moderate a
little, from -24c Saturday to around -16c today. This will help
generate high temperatures around 20 degrees today across northern
Michigan, only slightly warmer than high temperatures in the lower
teens yesterday. At the surface, an area of high pressure over the
Ohio Valley and eastern Great Lakes this morning, will push east of
the region today while a clipper drops out of Canada and into the
Plain states. This clipper will eventually lift slowly toward the
Great Lakes and into southern Michigan Monday.

Overall snowfall across the cwa will be limited today with lake
effects diminishing, and synoptic forcing not increasing until later
Sunday evening. Model soundings showing shallow inversion heights
around 5k feet this morning diminishing to around 2300ft by this
afternoon, with extremely dry mid and upper lvl moisture profiles.
Lake effects this morning will also be hindered by shifting winds,
as sfc-925mb winds shift from northwest to southwest. However, based
on current radar and sat trends, will keep some mention of light
lake snows in northwest and west snow belts through the afternoon.
The best chance for widespread snows with the advancing clipper,
will be after 00z Monday as 850/500mb qvectors show strong
convergence pushing west to east across the cwa. However significant
snows will most likely occur after 12z Monday, as model soundings
show mid and upper lvl moisture struggling to recover.

&&

.SHORT TERM...(Monday through Tuesday)
Issued at 327 AM EST Sun Jan 14 2018

...Widespread snow transitions to lake effect Monday...

High Impact Weather Potential: Accumulating snow through Monday
morning gradually transitions to more lake effect natured snow
through the end of the forecast period.

Pattern Forecast: Broad mid-level troughing remains anchored across
the eastern two-thirds of the CONUS early this morning with well
amplified ridging encompassing the West Coast. Northern hemispheric
water vapor imagery reveals our next system set to cross the region
locally Sunday night-Monday currently taking shape across Yukon/
Northwest Territories. Guidance is in fairly good agreement of that
wave diving southeastward into the northern plains this afternoon,
aiding to carve out renewed deep troughing across the center of the
country while precipitation begins to blossom coinciding with
ongoing surface cyclogenesis. This area of low pressure will trek
eastward across the western Great lakes Sunday night into Monday
accompanied by generally light system snow (embedded with pockets of
enhanced moderate-heavy lake effect) before gradually pressing
toward the northeastern states Monday night.

Primary Forecast Concerns/Challenges: Gradually diminishing system
snow continuing Monday morning along with embedded potentially heavy
lake effect snow across portions of northern Michigan.

Low-mid level south-southeast winds continue early morning morning
ahead of the aforementioned approaching low pressure...progged to be
centered across southern WI/northern IL. Generally light
synoptically driven snow will be the rule across the bulk of
northern Michigan through Monday morning with a general 0.5-1.5" of
new snow expected area-wide. Early morning wind gusts approaching 20-
25 mph (highest in coastal locations) may yield a bit of blowing
snow and a further reduction to visibility.

Complications arise across both western and eastern Mackinac County
(along with eastern Chippewa) as lake enhanced snow is expected to
pose greater impacts in parts of these areas. For western Mackinac,
ongoing lake enhancement Sunday night is expected to affect areas
primarily west of M-117 into the first half of Monday morning before
shifting further west. However, building ice coverage across far
northern Lake Michigan may inhibit overly heavy snowfall and keep
the QPF bullseye centered over portions of Schoolcraft/Delta
counties...as is hinted at by the majority of the 14/00z guidance
suite. Across eastern Mackinac/Chippewa, synoptic support
approaching far eastern reaches of the CWA by mid-Monday morning
should aid in kicking off potentially intense lake effect snow
convection expected to run southeast to northwest across central
Lake Huron and initially impacting locations east of M-48 including
Drummond Island...perhaps as far north as Sugar Island and Sault
Ste. Marie. Forecast model soundings from Drummond Island Monday
morning suggest plenty of over lake instability with delta Ts
nearing 20 C/lake induced CAPE near 600 J/kg, inversion heights
around 7 kft, omega pegged directly in the DGZ, and ample
synoptically supported moisture above the boundary layer. While all
of this lends itself to increased confidence in a period of
potentially heavy snowfall and several inches of additional
accumulation, exact locations to see potential impacts will
certainly depend on the prevailing wind direction and is worth
monitoring in future outlooks over the next 24 hours.

By early Monday afternoon into Monday evening, low level flow is
gradually expected to back more east-southeasterly as low pressure
treks across southern Michigan...allowing the primary threat areas
for heavy lake enhanced snow to shift further inland across Mackinac
County (generally near and east of the bridge/I-75), along with
potentially pressing into sections of northeast lower (Cheboygan,
Presque Isle and Alpena counties at greatest risk).

Flow turns more northerly Monday night into early Tuesday with the
bulk of any lingering lake enhanced snow ending, although the
potential for additional, mainly light, north flow lake induced snow
showers lingers...primarily across the GTV Bay region and points
west, and across the immediate Lake Huron shoreline of far northeast
lower.

.LONG TERM...(Wednesday night through Sunday)
Issued at 144 PM EST Sun Jan 14 2018

High Impact Weather Potential...

High pressure across most of the eastern CONUS will bring moderating
temperatures through the extended. Quiet weather is expected through
much of the period, with the next widespread precipitation chances
tied to a system moving out of the southern Plains. There is a good
bit of uncertainty with this, especially in the timing. Guidance
divergence in the track isn`t quite as substantial as the timing,
but could be the difference between seeing all snow, or some rain as
well. This will be something to keep an eye on over the next few
days.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 144 PM EST Sun Jan 14 2018

VFR conditions have returned to most of the terminal sites today.
Only exception continues to be MBL...where lake snow
showers/clouds continue to skirt through that area leading to MVFR
and occasional IFR weather. Snow showers will eventually push out
of there as well as winds continue to back S->SE.

VFR conditions persist through much of tonight. However...next
weather system will be sliding through the western Great Lakes
region overnight through the day Monday. This will spread light
snow and MVFR conditions back into the region during that time.
Some lake enhancement is possible at the APN terminal site Monday
afternoon.


&&

.MARINE...
Issued at 327 AM EST Sun Jan 14 2018

Small craft advisory winds will develop across portions of the Lake
Michigan nearshore waters today and tonight, as southerly winds
increase in advance of an approaching clipper. Lake snows will
diminish this morning, before widespread snow overspreads northern
Michigan Sunday night and Monday, the result of the clipper lifting
into southern Michigan.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...SMALL CRAFT ADVISORY until 1 PM EST Monday for LMZ323-342-
     344>346.
LS...NONE.
&&

$$

UPDATE...BA
NEAR TERM...SR
SHORT TERM...MG
LONG TERM...AM
AVIATION...BA
MARINE...SR


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