Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 211148
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
648 AM EST Tue Feb 21 2017

.NEAR TERM...(Today and tonight)
Issued at 326 AM EST Tue Feb 21 2017

...Rain exiting then warm...

High impact weather potential...none.

Occluded-type front moving east across western upper MI and central
WI. A band of rain is ahead of front, presently crossing parts of nw
lower and eastern upper MI. Helped in part by evap cooling, temps
are hovering near freezing in the mid/upper St Marys Valley, and
freezing rain has been reported at times at Sault Canada. However,
evap cooling potential has been used up, and further warm advection
and mixing down of warmer air from aloft will end any fzra concerns.
Timing the rain band across the area is concern #1. Concern #2: just
how warm will we get today?

Today...front crosses northern MI in the 1st half of the day,
replacing one Pacific airmass with another. Showers will march
steadily ne-ward across northern MI this morning, exiting se
sections by noon-1pm. Rainfall totals from this point will be on the
light side.

Brief period of wnw low-level winds will be seen post-frontal, but
backing toward the sw will already be impinging on northern Lake MI
by dusk. There is a healthy amount of stratus behind the front, with
a back edge nearing far western WI. However, the sun will go to work
on this as the day proceeds, and most model guidance is bullish on
breaking out into sunshine this afternoon, with eastern upper a
partial exception. Will slow the model-blend clearing trend down a
touch. That would still be enough sun to pop temps into the 40s in
the Straits region and eastern upper MI, and the 50s in most of
northern lower.

Some record highs are in serious jeopardy:
 Sault Ste Marie  42
 Gaylord          52
 Alpena           50
 Traverse City    57
 Houghton Lake    57
We should be within a few degrees of all of these.

Tonight...low pressure will continue to spin away on Hudson Bay. An
associated, strung-out cold front in the northern plains will slowly
ooze east toward Superior. It doesn`t get here, but the pressure
tightens just in advance of this feature, producing an uptick in low-
 and mid-level 1000-850mb sw flow and theta-e advection. 700-500mb
lapse rates get a little steep (nearing 7.5 c/km), which will at
least promote some cloud cover. This will be especially the case at
the nose of the stronger flow, over eastern upper and ne lower MI.
Not completely out of the question we could squeeze some sprinkles
out of this, though dry air below 750mb will be a sharp limiting
factor. No mention of precip tonight for now, though clouds will be
on the increase in the evening, before diminishing some toward dawn.
Min temps will be near 30f (the Sault) to the upper 30s (nw lower MI
coast).

&&

.SHORT TERM...(Wednesday through Thursday)
Issued at 326 AM EST Tue Feb 21 2017

...Warm Wednesday with showers late across the north...

High Impact Weather Potential...Minimal

Pattern Synopsis/Forecast...Southwesterly flow will lead to strong
WAA through the day on Wednesday. With a good amount of sunshine
expected across northern Lower during the day, coming off mild
(above freezing) low temperatures Tuesday night, there are signals
Wednesday will shape up to be a very warm day at least across
northern Lower. Temperature anomalies from 925mb to 700mb (2 to 3
standard deviations above the mean) lend further support to an
unseasonably warm Wednesday. As previous shift mentioned, some
record high temperatures could be in jeopardy across northern Lower
as temperatures push well into the 50s...even low 60s across
southeast parts of our forecast area. More cloud cover over eastern
Upper will keep temperatures there locked in the 40s.

An amplifying shortwave will cross the Upper Great Lakes region
Wednesday night as a cold front drops southeast from over Lake
Superior. Impressive fgen forcing develops along the front while
over Lake Superior and eastern Upper, but it weakens considerably as
the front progresses into northern Lower. Highest PoPs are therefore
across eastern Upper, with just a slight chance across far northern
Lower to account for the proximity of the system. Temperatures will
be warm enough for just rain with this system. The cold front will
usher in drier weather for the rest of the day Thursday, but it will
also mark the beginning of a cooling trend for the rest of the week.

Primary Forecast Concerns...Still considerable variance between
models in terms of the late Wednesday system`s timing and intensity.
Some recent NAM and ECMWF runs had developed a rather wound-up
system with a potent surface low, but the latest trend among
deterministic models seems to be more of an open wave aloft with a
weaker surface low. Have discounted the Canadian as its last several
runs have handled this system rather erratically. Pinning down
timing remains somewhat of a challenge, but consensus would point
towards a late afternoon arrival, with the rain departing by
daybreak Thursday.

.LONG TERM...(Thursday night through Monday)
Issued at 326 AM EST Tue Feb 21 2017

High Impact Weather Potential...Strong system will bring gusty
winds, accumulating snow, and possibly a wintry mix to northern
Michigan for the end of the week.

Intensifying system over the Central Plains Thursday night will
become vertically stacked and occluded as it lifts northeast towards
the Great Lakes on Friday. Though there is decent general agreement
among the various deterministic models this many days out, they are
still (not surprisingly) struggling to some extent with pinning down
some important details such as timing, intensity, and track of the
system. At this time, WAA-induced precipitation shield looks to lift
into northern Lower Thursday evening, overspreading northern
Michigan by Friday morning. More or less steady precip looks to be
the rule during the day Friday, and then parts of the area will be
dry-slotted Friday evening/night before wrap-around precip works its
way into northern Michigan for Saturday. Last few GFS and ECMWF runs
have remained consistent with showing a few hundred J/kg of MUCAPE
extending into northern Lower Friday afternoon/evening, so have
introduced a chance of thunder for southeast portion of the forecast
area during that timeframe. In terms of ptype, expecting primarily
snow Thursday night with a transition over to rain across northern
Lower during the day Friday, then back to all snow Friday night into
Saturday. Certainly can`t rule out a wintry mix during the
transitions, but have not included this in the forecast due to low
confidence this many days out. Most of the area could see up to an
inch of snow Thursday night with an additional 1 to 2 inches
possible across eastern Upper and Tip of the Mitt by Friday
afternoon. Amounts are subject to change over the coming days,
however. Better accumulating snow potential will come in the wrap
around precip on Saturday, and blowing snow will likely become an
issue as winds ramp up out of the NW during the day, becoming quite
gusty by midday as the low departs.

We then head into a much colder lake effect snow pattern Saturday
night through early Monday as much colder 850mb air plunges into the
Upper Great Lakes (down to -15 to -20C per latest GFS). However,
forecast soundings reveal not-so-favorable low level moisture will
be in place during this timeframe, so that will be a limiting
factor. Winds direction also shifts around a bit, so accumulations
will likely be fanned out across a larger area. Despite the limited
moisture, increasing confidence in lake effect snows warranted
bumping PoPs up to likely in the snowbelts. Highs over the weekend
into Monday will range from the 20s to 30s across northern
Michigan...winter will most definitely make a comeback.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 648 AM EST Tue Feb 21 2017

MVFR to IFR at times this morning.

Band of showers continues to move east across northern lower MI,
just ahead of an occluded front exiting eastern WI. Rain will exit
by midday, though areas of lower cigs will linger a few hours
longer. Still, expect all sites to be VFR by early/mid afternoon.

Current southerly winds will veer sw to w today behind the front,
then back south again tonight.

&&

.MARINE...
Issued at 326 AM EST Tue Feb 21 2017

Ongoing se to s flow will relent somewhat and veer sw as an
occluded front passes. Still, in some areas advisory-level
winds/waves could linger deeper in the morning, and will be taking
a harder look at that shortly. Another uptick in southerly winds
will be seen late tonight in Wednesday, though at this time this
does not appear to warrant advisories.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 7 AM EST this morning for LHZ345-
     347>349.
     SMALL CRAFT ADVISORY until 10 AM EST this morning for LHZ346.
LM...SMALL CRAFT ADVISORY until 7 AM EST this morning for LMZ323-342-
     344>346.
     SMALL CRAFT ADVISORY until 10 AM EST this morning for LMZ341.
LS...NONE.
&&

$$

NEAR TERM...JZ
SHORT TERM...MEK
LONG TERM...MEK
AVIATION...JZ
MARINE...JZ



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