Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 132039
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
339 PM EST Mon Nov 13 2017

.NEAR TERM...(Tonight through Tuesday)
Issued at 337 PM EST Mon Nov 13 2017

High impact weather potential: Maybe some additional patchy freezing
drizzle in far nrn lower and around the Straits region this evening.

Pattern synopsis and forecast:

A shallow open shortwave was working through the western Great Lakes
this afternoon, spreading some rather insignificant higher level
cloud overhead. The main feature is sfc high pressure entrenched in
nrn Michigan with still relatively deep low level moisture stuck
under an inversion. There is still a weak moisture flux coming in
off Lake Michigan in light westerly flow, and when combined with
some lake aggregate troughing and weak shear at the top of this
moisture, drizzle has been rather common across much of the westerly
flow areas of NW lower. WAA above this inversion has started to kick
in and slowly shallow out the moisture, with the drizzle becoming
more patchy with time. Clouds blanketed all across the region with
temperatures in the upper half of the 30s to some lower 40s.

The light westerly flow will continue into the early evening, before
a shift to more of a WSW direction is seen through the evening
hours. Can foresee patchy drizzle/developing freezing drizzle
continue in the W/WSW flow regimes, possibly impacting the Straits
region and into Mackinac county/DeTour Village areas. However, that
WAA looks to be strong enough to lower the inversion/dry out the low
levels sufficiently from SW to NE through the first half of the
night for all drizzle to come to an end. Skies may also be able to
clear out some by daybreak Tuesday, with patchy fog development.
Tuesday will be fairly uneventful. Any fog that develops will burn
off and lead to some decent sunshine for many, but the next
shortwave starts to work toward the western Great Lakes with
vorticity ejected into nrn Michigan by late in the day. There will
be an increase in mid level clouds through the day, while moisture
flux off Lake Michigan increases with an uptick in SW winds and
remnant overlake instability. This would throw a band of lower level
clouds into portions of the NW lower coast and into eastern upper.

Lows tonight are kind of tough. If we can clear out in spots, maybe
some lying areas could get down into the lower 20s, possibly upper
teens. However, the overwhelming consensus is for mid to upper 20s
most areas, with lower 30s in coastal areas. Highs tomorrow getting
into the lower to middle 40s.

&&

.SHORT TERM...(Tuesday night through Thursday)
Issued at 337 PM EST Mon Nov 13 2017

...Wet mid-week weather...

High Impact Weather Potential...Minimal.

Pattern Synopsis/Forecast...Warm air advection and isentropic lift
will spread across northern Michigan Tuesday night, with H5 heights
falling ahead of some incoming shortwave energy. An stretched out
vorticity maximum over the Northern Plains will interact with a more
potent vorticity maximum /deep shortwave/ dropping southeast out of
southern Saskatchewan. These waves will (somewhat) morph together
into a broad trough over the Upper Great Lakes on Wednesday.
Meanwhile an attendant surface low will strengthen as it treks
across southern Ontario, dragging a cold front across northern
Michigan during the day. A surge of colder air aloft will sweep in
behind the front Wednesday night into Thursday, leading to some
lake enhancement as the system gradually departs.

Primary Forecast Concerns...Widespread precipitation followed some
lake effect.

Respectable increase in atmospheric moisture out ahead of the
developing low Tuesday night into Wednesday. PWATs still looking to
rise to around 0.8 inches Tuesday night as isentropic lift spreads
across northern Michigan. Better forcing for more widespread
precipitation will come with the arrival of the shortwave energy
aloft and the cold front Wednesday morning. Looking like the front
will be on course to track through northern Michigan between late
morning and mid afternoon, taking the bulk of the widespread, steady
rain with it. Precip from this system will fall in the form of rain,
thanks to surface temperatures rising into the low to mid 40s on
Wednesday. Total QPF looks to be on the order of a quarter to a half
inch, highest across eastern Upper and along the northern Lake Huron
shore.

Colder and significantly drier air will settle in behind the front
late Wednesday with 850mb temperatures steadily dropping through
Wednesday night to around -10C. Resultant increase in over-lake
instability and brisk northwesterly winds behind the front will
yield a decent chance of lake effect heading into Wednesday night
and Thursday morning. Forecast soundings would hold off a transition
to snow until after midnight Wednesday night, however, when low
levels cool sufficiently. Canadian surface high ridge will nose into
northern Michigan Thursday afternoon, bringing and end to lake
effect showers and drier air progressively builds into the region.
Thus, only a brief window of opportunity for snow showers and not
much QPF...so little if any accumulation expected over interior
northern Lower and portions of eastern Upper.

&&

.LONG TERM...(Thursday night through Monday)
Issued at 337 PM EST Mon Nov 13 2017

Thursday night into Friday will be precipitation free with high
pressure ridging over the forecast area. As this high pressure moves
off to the east clouds will be on the increase throughout Friday
with WAA precip beginning later Friday ahead of a developing low
pressure system over the Great Plains. Winds will then veer to the
northwest Saturday as the low pressure system moves off to the east
of the forecast area...possibly providing an extended period of lake
effect snow through the remainder of the weekend. Exact timing,
intensity, and snowfall amounts with this storm are very uncertain
at this time as models continue to chance with each run and are not
in agreement. Daytime temperatures will generally be in the 30s with
Sunday being the coldest day...only reaching into the upper 20s.
Lows will be in the 20s except for Saturday morning with the
WAA...only dipping into the low 30s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1225 PM EST Mon Nov 13 2017

Mainly MVFR/low VFR cigs will continue into this evening with
drizzle becoming much more isolated with time. Do think that the
patchy drizzle/freezing drizzle will hang around into the evening
for PLN, while the low clouds are expected to erode through the
night from SW to NE. SSW low level winds do increase very late
tonight into Tuesday morning, which will increase moisture flux
off Lake Michigan into MBL for a potential return to MVFR CIGS.
Winds will remain light/variable thru tonight with speeds under
10kts Tuesday.


&&

.MARINE...
Issued at 337 PM EST Mon Nov 13 2017

No marine concerns through tonight in weak wind regime while sfc
high pressure departs east. Winds increase through the day Tuesday
in tightening pressure gradient, and will result in solid advisory
level speeds for most nearshore waters into Wednesday, with the
potential for low end gales for portions of Lake Michigan and
Whitefish Bay. Low pressure crossing srn Ontario Tuesday night
through Wednesday with warming temperatures, will bring along a
period of rainfall with the stronger winds.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

NEAR TERM...SMD
SHORT TERM...MK
LONG TERM...TL
AVIATION...SMD
MARINE...SMD



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