Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 080219
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
919 PM EST Sun Mar 7 2021

.UPDATE...
Issued at 919 PM EST Sun Mar 7 2021

00Z APX sounding showed a very narrow mid-level moist layer,
centered on 750mb, and very dry air below (850mb dew pt depression
was some 40C). But the initial shortwave moving thru the area has
increased that moist layer and steepened lapse rates. Convective
mid-level returns continue to cross northern MI, and 20dbZ have
been seen less then 1500ft AGL ne of the radar. Though no precip
has been reported by any ob site, do suspect that some flakes are
reaching the ground in isolated spots. Have added a small chance
of flurries/light snow showers to parts of northern MI this
evening.

Guidance continues to aggressively moisten the mid-, and to some
degree low-, levels overnight in eastern upper MI. Substantial
theta-e advection is driving this deeper moistening, which
also develops an above-freezing warm layer aloft. Actually getting
precip out of this is quite uncertain; the RAP has occasionally
been relatively aggressive is bringing a narrow band of showers
across much of northern MI overnight. But at the present, the RAP
and most other near-term guidance is dry, and only a few weak/
meager returns are noted upstream (moving into ne WI). Will
continue to ride with a small chance for -FZRA overnight in the
Straits area and points north. QPF would be very small, and any
potential impact should be likewise.

&&

.NEAR TERM...(Through Tonight)
Issued at 342 PM EST Sun Mar 7 2021

...Spotty Light Wintry Precip Overnight...

High Impact Weather Potential: Minimal.

Pattern Synopsis/Forecast: Sharp short-wave ridge axis is just
upstream...stretching from the western U.P. down through Illinois.
Short-wave impulse and associated surface trough/boundary follows
close behind, swinging through south-central Canada into the
Upper Midwest with a batch of high level warm advection forced
cloud cover pressing into the western lakes. Also of note, a
narrow line of mid cloud cover is crossing central Upper Michigan
down toward GRB with some spotty radar returns. Line of elevated
weak convection appears tied to advancing mid level theta-e axis
coincident with some steeper lapse rates.

Meanwhile, large area of surface high pressure remains in control
of our weather, stretching from the central lakes southward to
the Gulf with southerly return flow increasing and leaning through
the Upper Midwest into the western lakes.

Dampening short-wave impulse is expected to slide into and
through the northern lakes region through tonight while surface
cold front advances into the far western Great Lakes by early
Monday morning. Axis of low level warm air (>0C at 850 MB) ahead
of the boundary will fold into the region later tonight resulting
in a narrow ribbon of low-mid level warm advection forcing
sliding through.

Primary Forecast Concerns: Precip chances and type through
tonight along with stratus/freezing drizzle possibilities.

Details:

First off, initial narrow line of mid cloud cover and elevated
radar returns will move through the CWA through this evening
(recent NAMNEST/HRRR runs clearly pick up on the elevated
convection). But given the amount of dry low level air in place
right now (single digit dewpoints), I am doubtful that much gets
to the ground. Just mentioning it just in case.

Meanwhile, NAM/GFS guidance remain very bullish in developing low
cloud cover through the Upper Midwest late this afternoon and
further expanding into the northern lakes region tonight.
However, again given the amount of low level dry air entrenched
through the region and no sign of any low cloud development in
the Upper Midwest at this juncture, I am skeptical that we see
much low cloud/drizzle development...at least through tonight
anyway (we could see some post-frontal low cloud/drizzle
development on Monday).

But, spotty light warm advection forced precip is possible late
this evening and through the overnight hours. Warm nose aloft in
concert with slightly steeper lapse rates aloft (pushing 7C/Kg in
the 700-500 MB layer) and below freezing surface temps might bring
some spotty freezing rain drops/sleet pellets across eastern
Upper Michigan and the tip of the mitt. Minimal QPF, so I
anticipate very minimal if any impacts.

&&

.SHORT TERM...(Monday through Wednesday)
Issued at 342 PM EST Sun Mar 7 2021

High Impact Weather Potential: Minimal, except for perhaps some
lingering wintry precip across Eastern Upper...

Pattern Synopsis/Forecast:

Shortwave passing through the flow to our north with attendant
surface reflection looks to be exiting stage right Monday
morning...though perhaps not without lingering a bit of cloud cover
across the area, with light wintry precip exiting the Eastern UP
through the morning hours. As mid-level subsidence presses into the
region ahead of broad upper-level ridging...will look for surface
high pressure to return during the afternoon in conjunction with
temperatures warming to above normals...at least, across much of
northern Lower. A stronger push of warm air looks to enter the
region going into the day Tuesday...as return flow strengthens ahead
of next system upstream in the central Plains. Warm, moist air
advecting into the area through the day Tuesday should lead to
snowmelt...and perhaps fog potential as well later in the day. Warm
air advection Wednesday ahead of the next system should lead to
another warm day...though it will be rainy and breezy as this system
moves into the region.

Primary Forecast Concerns: light wintry precip linger Monday
morning...temperatures Tuesday and Wednesday...precip chances
and gusty winds late Tuesday into Wednesday...

First thing to deal with will be the potential for that light wintry
precip to linger over the area Monday morning for a time. Moisture
depth appears to get even shallower with time going through the day
Monday...though model derived soundings indicate there may be some
potential for low clouds to linger around through part of the day
Monday as we`re marginally sideswiped to the north by a weak,
latitudinally-oriented cold boundary late Monday into Monday night.
Not entirely sure how well that idea will pan out...given that some
models are currently having a hard time with upstream low clouds
(i.e., too cloudy vs reality)...so continued with an idea of
clearing at least in the afternoon, though clouds should stick
around through at least the early part of the day. Either
way...temperatures across Eastern Upper should approach and/or
exceed the freezing mark by mid-late morning/early afternoon, which
should serve to mitigate the frozen precipitation potential. Even
so...Monday morning commuters across northern portions of the
area...especially north of the Bridge...may want to leave a little
extra time in case of slick spots (or having to run the defrosters).

Temperatures Tuesday into Wednesday may not be entirely as
straightforward as they seem...though the idea of much warmer air
seems quite plausible given warm advection not only at the
surface...with surface high pressure across the southeastern US and
low pressure in the Plains...but also through a majority of the
column...as flow through the vertical turns primarily southwesterly
ahead of troughing aloft. Looks as though perhaps consensus guidance
is not as bullish with warmth today as in previous days...though
still warm, with highs potentially into the 50s. Warm, moist
advection, as mentioned above, may serve to melt at least a portion
of the snowpack, with potential for dewpoints to rise above freezing
by mid-week. This may throw a bit of fog potential into the
forecast, though confidence is not extremely high in this attm.
Currently looks like best chance for that would be later Tuesday
into Wednesday with the warmest and moistest air closest to
saturation. Will have to keep an eye on this going forward. Even
so...will still look for temperatures to be warm and springlike,
even if the weather outside looks grungy.

There is some uncertainty in exactly how the pattern for Tuesday and
Wednesday unfolds...though there seems to be pretty good agreement
in two systems moving through the central Plains...the first one, a
bit further west, which attm keeps the majority of its precipitation
along or north of the Canadian border. Can`t rule out that we won`t
see anything with it, though...especially later in the day
Tuesday...as its cold front approaches. As upper level troughing
moves eastward...and another shortwave moves through the
flow...looks like that second low pressure to develop in the central
Plains will ride up the cold front/baroclinic zone left by the first
low...allowing the second system to set its sights a little more
firmly on Michigan. Since this second system will be a little
further east than the first...we should be in a better position for
warm/moist advection...and do note that moisture transport is
stronger and more anomalous across the Great Lakes area...with pwats
near or above climatological maxes for March 10-12th. Not a
surprise...given the wide open Gulf...strong southwesterly
flow...and potential for some upper level ascent working in our
favor with upper level speed max to our north placing us in a
position favored for divergence aloft and upward motion. Bottom
line:  Wednesday looks like a pretty wet day overall. It should be
relatively breezy/gusty as well, as pressure gradient increases
between high pressure to our southeast...and low pressure
encroaching from the west.

.LONG TERM...(Wednesday night through Sunday)
Issued at 342 PM EST Sun Mar 7 2021

High Impact Weather Potential: Minimal for now...

Looks like precipitation will likely continue into Thursday as
well...as it looks like the cold front with this system will be
moving through during the day. There are some differences between
the models for Thursday and beyond...which will determine how much
cold air will get into the region behind the system as strong,
latitudinally-oriented jet sets up somewhere in the vicinity of the
Great Lakes....with troughing across the southwestern US. This lends
itself to a fair amount of uncertainty in the forecast beyond Friday
(actually, beyond Thursday, for what it`s worth), so will hold off
on playing around too much with the long term until models can
settle their differences. One thing does look reasonable despite the
uncertainty, though:  it should be cooler in the latter half of the
week than in the first half of the week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 646 PM EST Sun Mar 7 2021

Some MVFR cigs possible late Monday. LLWS tonight.

VFR conditions out there now, with cirrus overhead and a few
patches mid clouds edging in. High pressure is moving off to the
east, and southerly flow will increase tonight ahead of cold front
now in MN. Expect mid/high clouds to thicken further, but expect
VFR conditions thru most of Monday. Some potential for MVFR cigs
to develop late Monday, but for now only the APN TAF has this
outright.

Southerly winds increase tonight, with LLWS overnight. Sw to w
breezes on Monday.


&&

.MARINE...
Issued at 342 PM EST Sun Mar 7 2021

South to southwest gustiness increases tonight ahead of a cold
front that folds into the region late tonight into Monday. Gusts
sufficient for small craft advisory headlines for most of the Lake
Michigan and Huron nearshore waters into Monday morning.
Winds/waves diminish through the day Monday and all headlines will
likely be allowed to expire as planned.

No additional marine headlines anticipated through Tuesday at this
juncture.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 7 AM EST Monday for LHZ346.
     SMALL CRAFT ADVISORY until 11 AM EST Monday for LHZ347>349.
LM...SMALL CRAFT ADVISORY until 7 AM EST Monday for LMZ323-342-
     344>346.
LS...NONE.
&&

$$

UPDATE...JZ
NEAR TERM...ADAM
SHORT TERM...FEF
LONG TERM...FEF
AVIATION...JZ
MARINE...ADAM


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