Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 240446

Area Forecast Discussion
National Weather Service Gaylord MI
1146 PM EST Thu Nov 23 2017

Issued at 1008 PM EST Thu Nov 23 2017

Evening satellite...upper air and surface maps reveal short wave
troughing and colder air retreating eastward out of the Great
Lakes. Low amplitude ridging noted upstream across the plains and
into the Rockies and well defined low-mid level thermal ridging
stretches up through the central CONUS...nosing into the upper
Midwest. Surface low pressure is over south-central Canada with a
tight P-gradient and increasing low-mid level warm advection
flow/forcing edging into the northern lakes region. Several small
pockets of warm advection forced showers already noted spreading
westward across western upper Michigan this evening along the
eastward edge of the advancing warm air.

Rest of tonight into early Friday...pulse of low-mid level warm
advection forcing spreads across the northern lakes region over
the next several upstream thermal ridge axis folds into
the western Great Lakes and warmer air begins to flood into the
region. Given the upstream radar trends...certainly looks like a
few light showers/sprinkles will make it into and across eastern
upper MI/tip of the mitt areas after midnight or so...and have
pushed PoPs into those areas a little quicker than inherited
forecast. Given how quickly temperature profiles (sfc and aloft)
warm to above freezing over the next next several hours...anything
that does reach the ground should mostly be of the liquid
variety...although it could be close. In any event...very minimal
QPF anticipated with little or no impact.


.NEAR TERM...(Tonight through Friday)
Issued at 238 PM EST Thu Nov 23 2017

...Milder yet for Friday...

High impact weather potential...Minimal over land. Gale force wind
gusts expected across Lake Michigan and on portions of Lake Huron

Pattern synopsis/forecast...Remarkably progressive pattern continues
(with no end in sight), with one shortwave trough on the way out,
with yet another set to arrive Friday. Lack of moisture with today`s
passing wave well evident, with just some spotty morning drizzle and
weakish lake effect, especially off Lake Superior. Wave arriving
Friday looks to have a bit more moisture to work with, perhaps
enough to drum up a bit of light rain as it passes.

Primary forecast concerns/challenges: Temperature and cloud trends
through the forecast. Addressing that light rain potential Friday.

Details: Warm air advection strengthens with time tonight as
southwest flow intensifies well ahead of that next approaching wave.
Dry conditions expected much of the overnight, with that deepening
warm air advection perhaps kicking off some light showers late
across eastern upper Michigan. With warming thermal profiles and a
deep elevated above freezing layer, suspect any precipitation that
does occur will remain liquid.

And, that waa regime continues right through Friday out ahead of a
deepening area of low pressure and its attendant cold front. Rain
showers are expected, particularly across the north where deeper
saturation will be realized. Increasingly gusty southwest winds will
do a number to temperatures, with afternoon readings expected to top
out well into the 40s, with even some lower 50s near Lake Michigan.
If more sun is realized, can see 50s a bit more common even further


.SHORT TERM...(Friday night through Sunday)
Issued at 238 PM EST Thu Nov 23 2017

...Seasonably cool with a wintry mix early followed by some light
snow to end the weekend...

High Impact Weather Potential: wintry mix or drizzle Saturday
trending toward snow Sunday, increasing the threat for some slippery
driving conditions.

Primary Forecast Concerns/Challenges: Precipitation type Friday
night and Saturday with dry air aloft.

Pattern Synopsis/Forecast...At upper levels, a 500mb trough dropping
south into the northern Plains Friday, will settle over the Great
Lakes Saturday, before pushing east toward the north Atlantic Sunday
night. Mid level temperatures in this pattern will drop from around
+8c Friday night in advance of the approaching 500mb wave, to around
-12c Saturday as the upper trough swings over the state. 850mb temps
recover slightly to around -5c to -7c Sunday evening as the upper
trough pushes east. At the surface, a strong storm system pushing
across Canada and into Ontario Friday, will sweep a cold front
across the Great Lakes Friday night as the storm sytem lifts into
Quebec. This front will exit the region Saturday night. A narrow
area of high pressure will sweep over the state Sunday morning,
before a clipper quickly drops out of Ontario and into the Great
Lakes Sunday evening.

Overall, model soundings showing a thermal temperature profile
sufficient for an all rain event across northern Michigan Friday
evening, with freezing levels over 8k ft in advance of approaching
cold front. However low lvl temp profiles drop significantly between
06z and 12z Sat on the backside of the exiting boundary, with the
freezing level dropping to under 1400 ft. Additionally, model
soundings show mid and upper lvl mstr decreasing rapidly by 12z Sat
across northern Michigan, while abundant low lvl mstr remains
trapped below the inversion into early Sunday, in a temp profile
between 0c and -9c. This will increase the likelihood of drizzle or
freezing drizzle across much of the forecast area Saturday and
Saturday night. Any lingering drizzle early Sunday should transit to
all snow during the day, as upper lvl mstr increases with
approaching shortwave, helping ice crystal seeding from aloft
(though mid levels seem to remain dry).

.LONG TERM...(Sunday night through Thursday)
Issued at 238 PM EST Thu Nov 23 2017

Pattern remains similar to what we have been seeing for the past few
days, with height rises and warming temperatures building in getting
briefly disrupted by clippers passing near or through the region.
Timing is often difficult with these energetic setups, but right now
it looks like precipitation chances will be tied to systems moving
through mid-week as well as late in the week. Expect above normal
temperatures through the period, with the brief cool downs serving
to get temperatures closer to normal.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1146 PM EST Thu Nov 23 2017

...VFR through the day Friday then a quick transition to IFR...

Mainly VFR conditions tonight through the day Friday. Incoming
surge of warm air is/has touched off several pockets of light
showers across upper Michigan. Light showers will slip through the
tip of the mitt over the next several hours with a little light
rain/sprinkles possible at PLN. Additional showers will expand
across upper Michigan on Friday Precip will eventually sag down
into lower Michigan late in the day and Friday evening as a cold
front slips down through the region. Colder airmass will bring a
quick transition to MVFR->IFR conditions at the terminal sites
Friday evening.

Bigger issue resides with winds. Strong southerly flow will
develop late overnight and persist through much of Friday. This
will lead to some gustier winds during the day Friday. But a
fairly strong low level temperature inversion will lead to LLWS
conditions at all terminal sites...late overnight and through the
day Friday. Winds veer northwesterly Friday night behind the front
and remain gusty.


Issued at 238 PM EST Thu Nov 23 2017

Widespread gale and small craft advisory conditions expected
through Friday as strong low pressure develops and advances across
the northern Lakes. Gale gusts expected to hold off until very late
tonight for northern Lake Michigan, with gale conditions expected on
Lake Michigan and areas down near Saginaw Bay on Lake Huron during
the day Friday. While gales come to an end Friday evening, small
craft advisory conditions expected to continue on all waters through


LH...SMALL CRAFT ADVISORY until 10 PM EST Friday for LHZ345>347.
     GALE WARNING from 4 AM to 10 PM EST Friday for LHZ348-349.
LM...GALE WARNING from 4 AM to 10 PM EST Friday for LMZ323-341-342-
LS...SMALL CRAFT ADVISORY until 10 PM EST Friday for LSZ321-322.


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