Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Gaylord Michigan
644 am EST Thursday Nov 27 2014

Synopsis...
issued at 405 am EST Thursday Nov 27 2014

Another shot of Arctic air along with snow showers will make for a
chilly Thanksgiving day and night. Milder air trying to overrun the
Arctic air in place Friday into Friday night will bring a period of
snow to the region. Mild conditions are then expected Saturday and
Sunday out ahead of yet another shot of cold air that is due in
early next week.

&&

Short term...(today through tonight)
issued at 405 am EST Thursday Nov 27 2014

Overview: deep...progressive trough axis extends from Hudson Bay to
the Gulf this morning. Stronger middle level short wave within the flow
now advancing through the Tennessee Valley while secondary short
wave trough axis (leading edge of our next core of Arctic air) is
now dipping down into the North-Western Great Lakes.

Meanwhile...overnight surface analysis revealing a bit more convoluted
pattern with broad/weak-ish low pressure stretching from the Great
Lakes to the southeast states. Surface cold front stretches from eastern Upper
Michigan down across Lake Michigan...getting shoved eastward by
strong high pressure building into the upper Midwest this morning.
Mainly light snow occurring with the front itself. But lake induced
snow showers have ramped up overnight in response to increasing qg
forcing and better moisture.

Ahead of the front...an overall light flow pattern has initially
allowed more mesoscale dominance with a lake aggregate inverted
trough axis extending up across Lake Huron to the NE lower Michigan
coastline. Resulting strong low level convergence across the lake is
driving beefier snow showers from NE lower Michigan around Thunder
Bay into Lake Huron. Also a bit of a lake vortice noted around
Thunder Bay/Alpena slowly sagging southward along the coast brining
a very localized enhancement to that area. On Michigan and
Superior...incoming cold front has/is scooping up ongoing lake snow
showers and pushing them into the usual snow belts.

Today...surface cold front/upper trough/pocket of qg-ascent swings
through the region this morning with an overall batch of light snow
progressing through the region. But...aforementioned lake convection
will bring some heavier snows to the snow belts. Heaviest still
expected to be right along the Lake Huron coast from Alpena
southward to Oscoda as low level trough/lake induced vortice slides
down through that area. Always tough to gauge snowfall rates off
Lake Huron. But based on surface observation and past experiences that area is
probably seeing up to inch per hour type snows that will persist
through late morning...although spread out down along the coastline.
Think another 2-4 inches is possible along that sliver of coast this
morning on top of whatever has fallen overnight...and will keep
advisory going for Alpena and Alcona counties through it/S scheduled
18z end time. However...trimming Presque Isle out of the advisory as
most persistent heavier snow is south of that County.

For the usual snow belts...after frontal passage northwest flow snow showers will
ramp up for time this morning as -17c 800 mb air or colder slides over
the lakes and low level lapse rates steepen substantially.
But...strong drying/lowering inversions quickly take over this
afternoon as upstream high pressure builds into the region. There
will probably be a few hours of dicier winter weather across the
snow belts of eastern upper and northwest lower Michigan through middle-late
morning...but I dont think it is advisory worthy.

Tonight...dries out substantially as surface ridge axis builds across
the state by morning. Northwest flow and lake instability will maintain
lighter snow showers over the usual snow belts this evening with
minor accumulations. Veering flow overnight pushes remaining light
snows up along the Lake Michigan shoreline to The Straits.
Again...minor accumulations of an inch or less anticipated through
the night.

Temperatures will essentially remain flatline through today and even drop
off through the afternoon after frontal passage. Very cold tonight with lows
dipping into the single digits to the teens.

Long term...(friday through wednesday)
issued at 405 am EST Thursday Nov 27 2014

It still looks like highly variable conditions over the next several
days as northern Michigan is expected to remain in the Battle Ground
between Arctic air to the north and milder air to the south. As a
result there will likely be at least a few rounds of snow
showers...with lake enhancement from time to time. It even looks
like it will warm up enough Saturday into Saturday night to bring
any precipitation in the form of mainly rain. The main long term
forecast concerns revolve around probability of precipitation through the period as well as
snowfall accumulations Friday into Friday night.

Friday into Friday night....strong warm advection/isentropic ascent
(i-290k) develops as milder air overruns the Arctic air in place. In
addition...moisture increases while the flow becomes southerly
leading to convergent flow into western Mackinac County which will
likely lead to a beefy band of lake enhanced snow off of Lake
Michigan...where lowered visibilities and locally heavy snowfall are
possible. Elsewhere...widespread light to possibly moderate snow
overspreading the region during the day into at least the first half
of Friday night. Have increased probability of precipitation to categorical except for
across southeast zones where likely probability of precipitation are in order. In
addition...increased snowfall accumulations...could see general 2 to
4 inch amounts with locally up to 6 or more inches across western
Mackinac County where an advisory may end up being required.

Saturday into Saturday night...decreasing over lake instability as
the milder air appears to temporarily win out...with just the chance
for a few warm advection driven snow or even rain showers (as 850 mb
temperatures push past 0 c...especially across northern lower).

Sunday through Wednesday...Arctic air will spill back into the
region later Sunday allowing for one more mild day. Could see a band
of snow with the front followed by north northwest flow lake effect
behind it for Sunday night into Monday (but probably nothing
significant as moisture appears to be lacking). The roller coaster
ride of temperatures continues with cold conditions Monday followed
by another mild surge Tuesday...followed by another possible front
and snow showers along with colder temperatures Tuesday night or
Wednesday.

Highs only in the lower to middle 20s Friday...the milder middle 30s
to lower 40s Saturday...the almost balmy middle 30s to middle 40s
Sunday. This will be followed by the colder lower to middle 20s
Monday...the upper 20s to lower 30s Tuesday and Wednesday (though if
the faster timing of another front of the European model (ecmwf) pans out Wednesday
would be colder once again).

&&

Aviation...(for the 12z tafs through 12z Friday morning)
issued at 644 am EST Thursday Nov 27 2014

Cold front will slide through northern lower Michigan this morning
turning winds into the northwest and becoming a bit gusty for the day
with gusts into the lower 20 knot range. Winds diminish tonight to
under 10 knots and gradually back SW-west by Friday morning.

Weather-wise...light snow and largely MVFR conditions will be
found across northern lower Michigan this morning...although pockets of
heavier snow will result in brief IFR conditions at tvc/mbl/apn.
High pressure and much drier air build into the region this
afternoon through tonight. Lake snow showers will persist in the
snow belts...but become light later this afternoon and especially
tonight leading to a return to largely VFR conditions.

&&

Marine...
issued at 405 am EST Thursday Nov 27 2014

Cold front will pass through northern Michigan this morning with gusty
northwest winds developing on the lakes...and Small Craft Advisory
conditions anticipated into tonight. High pressure builds into the
region later tonight into Friday with winds weakening back below
Small Craft Advisory criteria while veering more west/SW by Friday
morning. But southerly winds ramp back up again later in the day
Friday and another round of small craft headlines may be needed
again.



&&

Apx watches/warnings/advisories...
Michigan...Winter Weather Advisory until 1 PM EST this afternoon for miz024-
030.

LH...Small Craft Advisory until 5 am EST Friday for lhz347>349.

Lm...Small Craft Advisory until 11 PM EST this evening for lmz323-342-
344>346.

Ls...Small Craft Advisory until 11 PM EST this evening for lsz321.

&&

$$

Synopsis...Sullivan
short term...Adam
long term...Sullivan
aviation...Adam
marine...Sullivan

National Weather Service Glossary of Abbreviations