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000
FXUS63 KAPX 050256
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
956 PM EST Thu Mar 4 2021

.UPDATE...
Issued at 944 PM EST Thu Mar 4 2021

Isentropically driven mid clouds spilling out of western upper and
toward Lake Michigan this evening. These clouds will continue to
slide southeast overnight, overspreading much of the area by
sunrise. Low level flow has backed to the northwest and we should
be able to invoke at least a minor lake response later tonight
with 925mb temperatures of -6C to -8C. The combination of
increasing mid level clouds and at least a minor lake contribution
may be enough to trigger some flurries or a few light snow
showers late. You could even argue for a touch of patchy freezing
drizzle given the marginal clouds temps but that appears to be a
somewhat lower probability and will not include in the forecast.

Temperatures will continue to drop steadily for another few hours
before they level off and even come up a bit overnight with the
arrival of the mid clouds.

&&

.NEAR TERM...(Through Tonight)
Issued at 331 PM EST Thu Mar 4 2021

High Impact Weather Potential: Minimal.

Pattern Synopsis/Forecast: 18z surface analysis shows a 1033mb high
centered north of Lake Superior with a ridge axis extending
southward across western Upper/eastern Wisconsin/eastern Illinois.
Michigan on the chilly side of this high but at least skies are
mainly sunny across the board.  A couple of anticyclonically curved
bands of warm advection induced clouds can be found over northwest
Ontario and starting to spill into western Lake Superior.  Meanwhile
multi-band lake convection remains over Lakes Michigan and Huron.

Amplifying large scale pattern expected to strengthen the
northwesterly jet axis across the Great Lakes tonight...with some
weak height falls moving into Michigan Friday. Upstream surface
ridge axis may not make much additional progress eastward...with
time will begin to see some pressure falls back into Michigan from
the northeast as surface pressure gradient expected to tighten up
again going into Friday.

Primary Forecast Concerns: Impacts of increasing isentropic ascent
across the forecast area later tonight...combined with lingering low
level cold air/overwater instability (925mb temperatures in the -6C
to -10C range from west to east).  After a clear start to the
evening expect to see at least some mid clouds spreading/developing
southeast into Upper Michigan later this evening and then into
northern Lower after midnight.  Low level flow is expected to back
more to the northwest this evening (already starting on Lake
Superior per satellite imagery)...though don`t expect an immediate
lake response on Lake Michigan this evening.  Upstream moist layer
is pretty thin but there a few spotty radar returns across northwest
Ontario and the Minnesota Arrowhead...and the combination of this
mid cloud and an increasing lake response overnight may be enough to
get some snow flurries going in spots...or some light snow showers
off Lake Superior. Or maybe even some freezing drizzle depending on
cloud layer temperatures which could be somewhat marginal though not
totally sure on the likelihood of this scenario coming to pass.

Temperatures may tank this evening under initially clear skies...
light winds..and dew points mixing into the single digits this
afternoon.  A few lows in the single digits possible before clouds
roll back in later.

&&

.SHORT TERM...(Friday through Sunday)
Issued at 331 PM EST Thu Mar 4 2021

Primary forecast concerns/challenges: Any lake effect?

No big changes in the guidance since yesterday with a northwest flow
aloft expected to remain in place through Sunday morning. This will
be followed by building heights Sunday afternoon. It`s marginally
cold enough for lake processes to take hold Friday into early
Saturday but the airmass appears to be rather dry so only some lake
clouds and perhaps a few passing flurries are expected. Partly to
mostly cloudy Friday morning, otherwise most spots should see a good
deal of sunshine through the period. Temperatures will be a few
degrees below normal Friday and Saturday with highs ranging from the
upper 20s to mid 30s. Not quite as cold Sunday with highs moderating
into the mid and upper 30s. Lows will be quite cold with the upper
single digits and teens Friday night then with surface high pressure
settling overhead Saturday, lows mainly in the single digits above
zero with a few spots likely dipping below zero.

.LONG TERM...(Sunday night through Thursday)
Issued at 331 PM EST Thu Mar 4 2021

High impact weather potential: None is expected.

Zonal to upper level ridging for the first half of the week leads to
unseasonably mild conditions. Low pressure likely tracking by to our
northwest will then increase chances for rain heading toward
midweek. Not as mild to end the period. Highs are expected to be
well into the 40s to the low 50s Monday then mainly the 50s Tuesday
and Wednesday when a few spots could even hit the 60 degree mark.
Highs Thursday in the upper 30s and 40s. Lows in the mid 20s to low
30s Monday and Wednesday nights and the 30s to low 40s Tuesday
night.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 639 PM EST Thu Mar 4 2021

VFR conditions expected this evening before ceilings lower
overnight into Friday morning. MVFR conditions will become
widespread across much of the area. A few flurries or a light
snowshower will be possible but not enough of a chance to warrant
a mention in the TAF.  VFR conditions will return by Friday
afternoon. Light winds tonight. Winds increasing and becoming
gusty from the northwest on Friday (G20kts).


&&

.MARINE...
Issued at 331 PM EST Thu Mar 4 2021

Increasing wind speeds will be the issue starting tonight as
pressure gradient begins to ramp up again especially on the Lake
Huron side.  Small Craft Advisories have already been issued for the
nearshore zones north of Sturgeon Point Light which is where the
greatest probability of small craft conditions will occur through
Friday.  Will expand Lake Huron SC.A into the remaining zones
starting Friday morning...and will probably need advisories for the
Lake Michigan nearshore zones starting Friday afternoon.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY from noon Friday to 5 AM EST Saturday for
     LHZ346-349.
     SMALL CRAFT ADVISORY until 5 AM EST Saturday for LHZ347-348.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...JK
NEAR TERM...JPB
SHORT TERM...AS
LONG TERM...AS
AVIATION...JK
MARINE...JPB