Area Forecast Discussion
Issued by NWS Gaylord, MI

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330
FXUS63 KAPX 300243
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
943 PM EST Tue Nov 29 2016

.UPDATE...
Issued at 933 PM EST Tue Nov 29 2016

Weak shortwave trough sliding through southern Michigan this
evening with isentropic upglide helping to produce a few showers
on the nose of developing 850mb theta-e ridge. Even a strike of
lightning over far southern Michigan earlier this evening. A few
showers may brush southeast corner of our area (South and east of
West Branch) over the next several hours as shortwave moves toward
Lake Huron.  Will keep a low chance of thunder in this area as
well given plume of steeper mid level lapse rates working toward
Saginaw Bay.  Lower clouds and areas of fog likely developing
behind this trough heading into Wednesday morning.  Low
temperatures tonight generally in the upper 30s to middle 40s
(which is warmer than our average high temperatures for this time
of year - Wow!).

&&

.NEAR TERM...(Tonight)
Issued at 243 PM EST Tue Nov 29 2016

...Cooling trend from midweek onward...

High impact weather potential: Low. Gusty winds into the early
evening and a low end thunder threat over NE lower Michigan.

Pattern Synopsis/Forecast: Deep stacked low pressure system
continues to spin over the northern plains, inching into Minnesota,
with elongated surface low pressure stretching into Lake Superior.
Main surface cold front stretches from western Iowa to a secondary
wave over Missouri, while much of the state sits within a well
defined dry slot/axis of warmer air and steep lapse rates aloft
stretching up through lower Michigan into Canada. Looking upstream,
batch of bubbly cloud cover (ACCAS) is spreading up into the
midwest(Illinois/Indiana), apparently driven along by another pulse
of weak warm advection/isentropic ascent taking shape across
that area.

Primary Forecast Concerns: Shower and low end thunder chances
tonight.

Tonight: Pulse of warm advection forcing is forecast to slide up
through lower Michigan during the course of the evening and into the
overnight hours, just skirting across NE lower Michigan. Coupled
with axis of steep mid level lapse rates already in place, may be
enough to kick of scattered showers and an isolated thunder threat
as highlighted in current SPC day one outlook. Not overly impressed
with thunder chances but will put it into the forecast as a slight
chance with no severe weather potential.

&&

.SHORT TERM...(Wednesday and Wednesday night)
Issued at 243 PM EST Tue Nov 29 2016

High Impact Weather Potential...None

Primary Forecast Concerns... Cloud/precip chances Wednesday.

Lower cloud cover and patchy fog lingers through the
morning hours. Then, stronger wave/associated forcing will punch up
through lower Michigan later in the morning and the afternoon hours
as the upstream cold front swings into the region. This will bring
increasing shower chances, particularly across NE lower michigan
where stronger QG forcing will be found.

.LONG TERM...(Thursday through Tuesday)
Issued at 243 PM EST Tue Nov 29 2016

High Impact Weather Potential...None.

Departing low leaves the region in north to westerly flow with
gradually cooling lower levels. No strong push of cold air in the
wake of the storm but increasingly colder into the weekend. 1000-
850mb layer temps only drop a couple degrees between 12z Thu and 12z
Fri. Lower layers are quite moist with mid level waves moving
through the flow...that and with some enhancement from the lakes
/lake induced CAPES near 500J-kg/ will continue the chance of
showers Wednesday night through Friday night. Showers look to be
mostly rain thru Thursday based on BUFKIT soundings with mix or
change to snow Thursday night.

A broad mid-level trough will develop over the northern Great Lakes
Friday night into Saturday, allowing for persistent general NW flow.
Combined with 850 mb temperatures around -7C and water temperatures
around 10C, this will be supportive of lake effect rain/snow showers
at times through Saturday night. Forecast soundings show somewhat
deeper instability downwind of northern Lake Michigan as compared to
Lake Superior, so have gone with higher PoPs across northern Lower.
A shift to southerly winds will bring an end to the lake effect
Sunday morning, but the break in precipitation won`t last long as a
tilted mid level trough pivots into the area Sunday afternoon and
brings a better chance for more widespread rain in the afternoon,
changing to snow by evening. The 29.12Z ECMWF has come into better
agreement with recent GFS runs, now developing a cutoff low over the
Desert SW that remains there through Sunday night before ejecting
northeast. This has resulted in a dramatic change in ECMWF surface
features depicted for Monday, with the latest run eliminating the
strong surface low that was earlier progged to travel through the
Ohio Valley and bring northern MI the potential for some decent snow
early next week. Instead, Monday is looking fairly dry, followed by
another system bringing chance PoPs for Monday night into Tuesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 621 PM EST Tue Nov 29 2016

Weak short wave over the mid Mississippi River Valley will slide
up through lower Michigan...ahead of a strong cold front moving
into the upper midwest tonight.  Along with steeper lapse rates
aloft/marginal instability, may kick off some showers that will
skirt parts of NE lower Michigan mainly during the overnight
hours.  Some of the model guidance hints at a batch of low (MVFR)
cloud cover and some fog developing upstream ahead of the front
and spreading up into northern lower Michigan overnight, then
persisting through Wednesday as the front eventually slides
through the region.  Will have to see how that unfolds as we go
through the evening, but for now have flight conditions lowering
toward (or below) MVFR at all terminal sites overnight through
Wednesday morning.


&&

.MARINE...
Issued at 632 PM EST Tue Nov 29 2016

Gradient relaxing overnight, with winds falling below SCA levels.
Therefore all marine nearshore headlines have been dropped.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...JK
NEAR TERM...TBA
SHORT TERM...TBA
LONG TERM...MEK/KJF
AVIATION...JK
MARINE...JK



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