Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 241059
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
659 AM EDT Sun Mar 24 2024

.KEY MESSAGES...

- Accumulating snow expected to gradually develop across
  northern Michigan especially this afternoon and evening.
  Highest accumulations through tonight north of M-68.

- Accumulating snow is eastern upper and tip of the mitt could
  lead to slick roads for Monday morning`s commute.

- Rapid warming Monday leading to above normal temperatures
  through Tuesday.

- Widespread rain chances Monday night through Tuesday with
  breezy to gusty south winds peaking Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Pattern Synopsis/Forecast: Split flow large scale pattern across
North America early this morning...northern branch flow emanating
from a ridge axis across the Canadian Territories...and sweeping
across the northern Plains and into the Great Lakes.  Southern
branch flow swings around an upper low along the Oregon coast...
with a short wave trough moving into southern California.
Subtropical jet streak extends across the southwestern U.S./southern
Plains/lower Mississippi Valley...with another southern branch short
wave trough off the southeast U.S. coast.  Low/mid level warm
advection underway across the northern/central Plains and
Midwest...strong 850mb thermal gradient across the Plains (more
than 20C degree temperature difference from northern Minnesota
into Kansas/Missouri). Still very dry across the upper Lakes
this morning...precipitable water value off 00z APX sounding a
paltry 0.08 inch...and better moisture return flow just getting
underway.

04z surface/composite analysis shows a broad area of high pressure
centered over the Great Lakes/northern Ontario/southern Manitoba
(1027mb).  Thickening mid/high clouds over northern Michigan at the
start of the day...some lake enhanced Sc and perhaps some flurries
over Whitefish Bay and adjacent areas of Ontario. Widespread radar
returns across the mid/upper Mississippi Valley within broad zone of
isentropic ascent...though nothing reaching the ground yet over
western Wisconsin.

Southern California short wave trough will cross the desert
southwest today and move into the central/southern Plains tonight.
This will boost the lee cyclone along the Colorado/Kansas border...
probably on the order of 980mb or so by 00z Monday which would be an
impressive -3 to -4 sigma standardized MSLP anomaly. Low is forecast
to lift northeast across Kansas overnight but may weaken some as it
is forecast to lag its upper level support.  Closer to home...high
pressure currently over the Great Lakes is forecast to slide east
today...allowing a tighter pressure gradient to develop over
Michigan by tonight and resulting in increasing southeasterly
boundary layer flow.

Primary Forecast Concerns:

Snow expected to gradually develop across northern Michigan
especially this afternoon and evening: Radar returns across
Wisconsin will spread across Michigan later this morning...dry low
layers will likely preclude much of this initial batch from reaching
the ground.  Deep layer isentropic upglide expected today but net
adiabatic vertical motion seems to be mostly neutral until this
evening...perhaps a system relative flow issue or lack of
kinematic support (upper level convergence in right exit jet
region). Increasing southeasterly boundary layer flow should
allow from shallow lake Sc to develop and possibly some flurries
especially into western Mackinac county. Current plan is to
increase PoPs during the mid-late afternoon basically west of
the I-75 corridor... then spreading northeast during the early
evening hours coinciding with arrival of best kinematic forcing
to aid isentropic ascent. But as the best forcing arrives this
evening...drier air is forecast to advect into the forecast area
from the south. So precipitation chances expected to wind down
fairly quickly this evening south of the M-72 corridor...with
snow chances diminishing from south to north as the night
progresses. Best accumulations will be from the tip of the mitt
northward given the longest duration of snowfall
tonight...highest probabilities for QPF exceeding 0.10"/12h are
north of M-32...with probabilities of exceeding 0.25"/12h
generally less than 20 percent. So the idea of 0.10-0.25" liquid
equivalent precipitation across eastern Upper and the Straits
is reasonable. As for snow-to-liquid ratio...given the north-
south thermal gradient should be a similar SLR gradient with a
deeper cloud layer warmer than -10C across northern Lower
(suggesting more snowflake growth by accretion/riming and lower
SLR). Used an SLR range from 8:1 to 12:1 south to north across
northern Lower...and 10:1 to 15:1 across eastern Upper which
resulted in snowfall ranges of 2 to 4 inches. 1 to 2 inches
north of the M-68 corridor and less than an inch south. &&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Pattern Synopsis / Forecast: Broad and deep mid to upper level
troughing dominates much of the CONUS to being the short term
forecast period. A developing surface lee side cyclone lifts to the
N/NE as upper level support begins to deepen and aid it Monday. Over
northern MI, winds near the surface will continue to veer and become
S/SE Monday. Warm air advection around 2-5 kft AGL will initially
reach the region, leaving drier air near the surface for Monday
afternoon. Although a stronger inversion exists, winds at the top of
the BL will still be ~30 to 35 mph allowing breezy to low end gusty
conditions near the surface. Afternoon temperatures will
dramatically warm into the 50s for northern lower. Eastern upper
will receive this warmer air later Monday, and could have some snow
to melt which leads to afternoon highs more in the 40s. Monday
afternoon/evening mid to upper level dynamics begin to aid in
spreading warm sector precip northward towards MI. Widespread rain
chances will move from west to east across the CWA Monday evening,
with chances lingering into Tuesday. The mid level closed low will
potentially open and begin to become negatively tilted, as well as
remain favorably stacked over the surface low. This added lift could
bring moderate to occasional heavy rain Monday night into Tuesday
morning.

Tuesday, precipitation chances will linger through much of the day
as the mid level open wave accelerates northward along its negatively
tilted path. Gusty S/SE winds will be seen much of Tuesday as strong
winds aloft move overhead and warmer air aloft erodes allowing
mixing heights to rise a little more. The surface cold front will
move through Tuesday late afternoon/evening, turning winds west.
Snow chances will be seen along the Lake MI shore and NW Lower
snowbelts late Tuesday night into early Wednesday morning as colder
air returns.

Primary Forecast Concerns: Overnight snow showers Sunday night into
early Monday morning could lead to slick spots on the roads where
snow has the best chance of accumulating. Most precipitation should
be moved out by the start of the short term forecast period, however
temperatures will still be sub-freezing. Rapidly warming
temperatures Monday morning (especailly after dawn) will allow any
impacts to be short lived. As far as rain amounts go for Monday &
Tuesday, it is still too early for confident amounts as Ref PW
values still have ~0.5" range in values across the CWA. At this
time, guidance favors the heaviest accumulations west of MI
however CAMs are just beginning to trickle in for Monday-Tuesday
timeframe. Trying to narrow down exact wind speeds for Tuesday
at this time is tough due to multiple features needing to align
on day 4 of the forecast (there is more than enough time for
track/timing changes of these features). Global ensembles do
show more confidence in the general upper level pattern, leading
to confidence in Monday night- Tuesday being generally breezy.
However, more agressive guidance might be overdoing how high
mixing heights are able to rise. Initial estimates of a more
windy scenario could be sustained 20 to 30 mph with gusts up to
40+ mph peaking in the early afternoon hours, with 52% of global
ensemble guidance leaning towards this.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
LES snow chances will likely be brief, lingering through Wednesday
mid-day as drier air quickly moves in. Chances could linger through
Wednesday night for eastern upper, however drier air could work to
limit accumulations. Early Thursday morning, a mid level closed low
will bottom out over the Great Lakes region, keeping west winds
breezy and reintroducing snow chances. There is very high
uncertainty with this next round of winter precipitation, with large
run to run changes and deterministic/ensemble disagreement. High
uncertainty with the large scale pattern at the end of the work week
results in large uncertainty for next weekend as well.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
VFR start to today will eventually give way to lowering ceilings
and snow moving across northern Michigan from late afternoon
into this evening. Worst flight conditions expected at KCIU with
MVFR conditions around 21z and LIFR conditions in at least
moderate snow after 01z ending around 08z. IFR conditions also
expected at PLN and TVC after 21z.

&&

.MARINE...
Tightening pressure gradient tonight will lead to small craft
conditions developing within all nearshore zone through Monday on
Lake Michigan/Straits of Mackinac...and through Monday night
elsewhere. Winds to gale forecast are possible Tuesday in the
Lake Superior and Lake Huron nearshore zones.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 8 PM this evening to 8 AM EDT
     Tuesday for LHZ345>349.
     Small Craft Advisory from 8 PM this evening to 8 AM EDT
     Tuesday for LMZ341.
     Small Craft Advisory from 8 PM this evening to 8 AM EDT
     Tuesday for LSZ321-322.

&&

$$

NEAR TERM...JPB
SHORT TERM...ELD
LONG TERM...ELD
AVIATION...JPB
MARINE...JPB


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