Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 230448
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1148 PM EST Sun Jan 22 2017

.UPDATE...
Issued at 949 PM EST Sun Jan 22 2017

Yet another wet...foggy and above normal evening across the
Northwoods as ample low level moisture remains in place...combined
with light winds and a melting snowpack continues to produce
stratus and dense fog across our CWA. Areas of drizzle are also
developing...especially across the NE two-thirds of our CWA with
some aid from orographic upslope via N/NE light low level flow.
This drizzle will continue to slowly expand overnight...and will
eventually increase in intensity to light rain as deeper moisture
pushes northward into the area along the NW edge of the low
pressure system riding up the East Coast. Expect one more night of
temps remaining just above freezing...so all precip should remain
liquid and should not freezing on surfaces.

&&

.NEAR TERM...(Tonight and Monday)
Issued at 345 PM EST Sun Jan 22 2017

...Dense fog again tonight with periods of drizzle...

High Impact Weather Potential...Dense fog expected overnight into
Monday morning.

Pattern Synopsis/Forecast...This morning`s APX sounding revealed a
not-so-steep surface inversion as Saturday, which has allowed for
more daytime mixing to scour out much of the fog and some of the low
stratus across northern Lower. However, a very loose pressure
gradient is keeping winds calm or very light. Later this evening, an
inverted surface trough associated with the strong low over the
Southeast will nose into the region, slowly pivoting westward across
lower Michigan overnight. Surface wind direction will become better
organized as flow turns cyclonic with the passing of this trough,
winds will still remain light. Low level moisture this afternoon is
rather shallow, extending up to only around 850mb. PWATs will
gradually increase from the southeast later this evening and
overnight, which will allow the low levels to moisten up a bit more.
Forecast soundings show the moist low level inversion steepening up
a bit again overnight, so with the increasing moisture and winds
staying light am expecting another night of dense fog development
and some drizzle as well.

Primary Forecast Concerns...Timing and expansiveness of the fog
tonight is the main forecast concern as well as what the impact may
be from some clearing in parts of northern Lower this afternoon.
Going by persistence, there is high confidence in fog redevelopment
overnight considering forecast soundings tonight look at least as
favorable (if not moreso) as this morning`s observed APX sounding.
There`s been some encroachment of drier air aloft across northern
Lower as seen on water vapor imagery this afternoon, and the partial
clearing/mixing in some areas this afternoon has likely has allowed
for a little drying out of the low levels. However, the continued
melting snowpack and increasing PWATs tonight will more than
compensate for any minor loss of moisture during the day. If
anything, this may just delay the onset of fog redevelopment a bit
this evening. In collaboration with neighboring offices, will
continue with the dense fog advisory remaining in effect for the
entire CWA through noon on Monday. Conditions should improve Monday
afternoon.

Forecast soundings overnight look more supportive of drizzle than
shower activity with relatively shallow low level moisture. By
Monday morning/afternoon, potential for showers will increase with
deeper moisture and better forcing from weak isentropic lift comes
into play, especially east of I-75.

&&

.SHORT TERM...(Monday Night through Wednesday)
Issued at 345 PM EST Sun Jan 22 2017

...Mild early then descending back into winter...

High Impact Weather Potential...Accumulating snow and dropping
temperatures midweek.

Pattern Synopsis/Forecast...North America still dominated by fairly
strong longwave troughing across the far eastern Pacific and just
off the west coast, and downstream longwave ridging/warm air through
much of the CONUS and Canada. A wavy and somewhat split flow in the
shorter wavelengths across the CONUS with some semblance of
blocking through eastern Canada and the east coast. Main upper jet
core runs through the southern states with strong shortwave energy
crossing the Gulf states and continues to produce very active and
severe weather through that area. Great Lakes region sort of in
"no mans land" with weak flow aloft, a wandering shortwave pushing
up into Ontario into the upper ridge, baggy surface low pressure
across the region, mild temperatures/stratus and fog the dominant
players.

Pattern will change across the CONUS this week as longwave troughing
in the far eastern Pacific/west coast eases and allows the
reemergence of strong ridging during the latter half of the week and
through next weekend. This will force downstream troughing back
across the CONUS, particularly the central and eastern CONUS by the
latter half of the week into the weekend, and reopen the cold air
expressway from the pole into the Great Lakes. Transition is
facilitated by strong low pressure system that develops in the
plains and rides up through the Great Lakes around midweek.

Primary Forecast Concerns...Accumulating snow midweek as strong
plains low crosses the region. Lake effect snows thereafter.

Aforementioned strong wave rolling through the Gulf coast states
today, will become negatively tilted while swinging out into the
Atlantic, while main shortwave energy runs up the Atlantic coast
into New England by late Tuesday. Much of the weather action will
remain up the east coast through Tuesday of course. But the western
and central Great Lakes region will find itself within a respectable
deformation/QG-forcing zone between the east coast wave and weaker
shortwave troughing in the upper Midwest, as thermal gradient gets
squeezed overhead. This will likely lead to lighter precip expanding
into the central and western lakes region later Monday and into
Tuesday. Mainly of the rain variety per forecast thermal profiles,
although some light snow may sneak into the picture later Monday
night into Tuesday as the atmosphere cools. Minor accumulations.

A brief reprieve later Tuesday as weak ridging at the surface and
aloft slides through the region. But the beginning of the big change
starts Wednesday as progressive trough off of the west coast
advances through the central CONUS and into the Great Lakes by
Wednesday, along with a deep area of low pressure developing in the
plains and rolling through the Great Lakes through late Wednesday.
Disagreement persists amongst the longer term guidance with regard
to forecast track through the region, which has implications for
forecast P-type. But a period of snow or rain/snow mix is still
anticipated Wednesday, eventually transitioning to all snow and into
a lake effect regime heading into Thursday as cold air begins to
spill into the region.

A couple inches of wet snow accumulation areawide (as a first guess)
is a good bet for Tuesday night through Wednesday with more to
follow in the snowbelts during the latter half of the week. This
does not appear to be a warning headline type event through midweek
(at least not yet). But a smattering of advisories may eventually be
needed. Will see.

.LONG TERM...(Wednesday night through Sunday)
Issued at 345 PM EST Sun Jan 22 2017

High Impact Weather Potential...Yes as much colder air, more
seasonal air, filters back into the Great Lakes through the period.
This will increase the chance for widespread lake snows into the
weekend.

A storm system from the Plains will lift up across the Great Lakes
Wednesday, before exiting northeast and becoming anchored near
Greenland by the end of the work week. At upper lvls, a deep broad
500mb trough over the Plains Wednesday, will push into the region by
Friday and remain anchored over the Great Lakes through the weekend.
This pattern will return wintry condtions to the Great Lakes through
the forecast period. Westerly flow lake effect snows, will become
more pronounced Thursday afternoon and linger into the weekend as
colder 850mb temps flood the region. 850mb temps fall from -4c 00z
Thursday to -12c Friday, before mid lvl temps fall to around -18c
Sunday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1145 PM EST Sun Jan 22 2017

IFR/LIFR conditions are expected at all Northern Lower Michigan
TAF sites overnight thru Monday night as ample low level
moisture...light winds and a melting snowpack continue to produce
widespread stratus and dense fog across all of Michigan. Some
areas of drizzle are also expected overnight into Monday morning
before chances of rain showers begin to increase from east to west
across our area along the NW edge of low pressure tracking up the
East Coast.

&&

.MARINE...
Issued at 414 PM EST Sun Jan 22 2017

Light winds this evening will pick up out of the east late tonight
into Monday, especially across northern Lake Huron. This will lead
to waves building over northern Lake Huron Monday morning, but
winds and waves will decrease Monday night into Tuesday. Patchy
fog (locally dense) and drizzle will develop tonight with showers
likely on Monday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...DENSE FOG ADVISORY until noon EST Monday for MIZ008-015>036-041-
     042.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...MLR
NEAR TERM...MEK
SHORT TERM...TBA
LONG TERM...SWR
AVIATION...MLR
MARINE...MEK



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