Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 221728
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
128 PM EDT Tue Aug 22 2017

.UPDATE...
Issued at 1017 AM EDT Tue Aug 22 2017

Secondary cold front/trough swinging through Northern Lower
Michigan this morning with a band of mainly showers and possibly a
rumble of thunder. Fairly tight gradient with fropa and have seen
some gusty winds of 30-40 mph along the nearshore waters. The
gustier winds will be translating across the rest of the CWA over
the next few hours, highest along some of our coastal locations. I
raised POPS across much of the area for the next few hours as the
front moves through. Quite a bit of subsidence/dry air coming in
for the afternoon hours, so clouds should scatter out with
increasing sunshine for most areas. Temperatures fairly steady for
the afternoon hours. The most noticeable difference for the
afternoon hours will be steadily lowering dewpoints - much less
humidity!

&&

.NEAR TERM...(Today through Tonight)
Issued at 342 AM EDT Tue Aug 22 2017

High impact weather potential: Thunderstorms early this morning.

Pattern synopsis and forecast:

Upper level troughing was working into the western Great Lakes early
this morning, with an associated sfc low pressure deepening while
tracking into eastern Lake Superior. The system cold front extended
from this low back through eastern Wisconsin and Iowa. Showers and
some isolated thunderstorms have finally developed over the last
couple of hours as low level convergence and DPVA have increased
within a region of 400-900 j/kg of MUCAPE. Latest RUC analysis also
suggests that maybe some right entrance region dynamics from 100+kt
jet are in play. Quite the warm/muggy morning with temperatures and
dew points in the middle 60s to lower 70s.

Upper troughing settles in over the region through the day with the
sfc low lifting into Quebec, while dragging the cold front through
nrn Michigan this morning into early afternoon. The forcing
continues to increase through daybreak with showers and isolated
storms likely to continue to increase in coverage. No severe storms
with not much instability around and lapse rates not all that
impressive at less than 6c/km. A secondary sfc trough axis looks to
follow behind the cold front, resulting in a band of lighter rains,
especially into the higher terrain of nrn lower. There is likely to
be some afternoon cumulus, but the overall air mass dries through
this evening. As cold advection continues through the night however,
temperatures get cold enough for overlake instability, almost to
850mb. Gotta believe that lake effect clouds in NW flow will be
common by daybreak Wednesday.

Highs not really going anywhere through the day with middle 60s to
lower 70s, slightly higher in downsloping areas of NE lower. Lows
tonight in the middle 50s most areas with less humidity.

&&

.SHORT TERM...(Wednesday through Thursday)
Issued at 342 AM EDT Tue Aug 22 2017

...Cool weather for midweek...

High Impact Weather Potential: Minimal.

Pattern Forecast: North American pattern features a decent short
wave trough for late August moving through the Midwest and adjacent
portions of Manitoba/Ontario.  Overall pattern from the Midwest back
into the eastern Pacific has become more amplified over the past 36
hours with short wave ridging having developed over British Columbia
downstream of a compact upper low south of Alaska.  Associated with
the Midwest short wave trough is a 1008mb surface low over northeast
Minnesota...with an eastward extending warm front across Upper
Michigan and into southern Quebec...and a trailing cold front back
into northwest Iowa/Nebraska.  Plenty of humidity south of the warm
front with dew points well into the 60s/precipitable water values in
the 1.50-2.00 inch range (1.58 inches on 00z APX sounding).

Cold advection into the mid level short wave trough moving through
the Midwest suggests continued deepening of this feature...
eventually closing off north of the Great Lakes later today.  The
result will be deep layer cyclonic flow across Michigan for the
midweek period...followed by rising heights for the end of the week
as short wave ridging crosses the prairie provinces.  Impressive
surface low for late August will drag cooler air across the Great
Lakes...followed by high pressure building in for Thursday/Friday.
Thermal troughing will ensure a much cooler pattern.

Primary Forecast Concerns: Cold air getting pulled across the lakes
should bring about a good deal of lake plus diurnally induced cloud
cover Wednesday.  Some scattered light rain showers also possible
within typical northwest flow lake effect areas at least into early
afternoon.  Breezy day expected with gusts 20-25+mph...winds should
subside by Wednesday evening.  Highs Wednesday will be mostly stuck
in the 60s...generally 8-12 degrees below normal.

No real issues for Thursday outside of some nuisance cloud issues
between thermal trough in place and short wave trough rotating
across the area from the north...again probably through early
afternoon with decreasing clouds north to south.  Probably another
afternoon with highs in the 60s...and chilly Friday morning where
some of the typical cold spots will probably drop into the 30s.

.LONG TERM...(Thursday night through Monday)
Issued at 342 AM EDT Tue Aug 22 2017

High Impact Weather Potential: Minimal.

Great Lakes looks to be stuck in split flow between ridging across
northern Ontario and a southern branch weakness that develops over
the Mississippi Valley this weekend.  The result is fairly weak
upper level flow across Michigan for the weekend.  High pressure
will be in place Friday...and given lack of "direction" from above
will probably linger through the weekend though a couple short wave
troughs may slide across Michigan.  How weakness in the southern
branch of the split flow evolves early next week is uncertain.
Overall weather looks quiet through the weekend...with a moderating
trend in temperatures.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 122 PM EDT Tue Aug 22 2017

A cold front has pushed through the area, with generally MVFR CIGS
in its wake. Drier air is working into the area from the northwest
and this will continue through the afternoon hours, resulting in
clouds gradually scattering out. This evening will likely be
fairly clear, before cold air advection over the warm lakes
begins to produce lake clouds overnight. These clouds will
persist through the first half of Wednesday. VFR cigs are
generally expected at this time, with pockets of MVFR possible. A
few light lake effect rainshowers are also possible.

Northwest winds will be gusty both this afternoon and Wednesday,
with a strong gradient across the Great Lakes. Gusts of 20+ kts
are expected this afternoon, subsiding some tonight, with gusts
of 20+ kts expected again on Wednesday.

&&

.MARINE...
Issued at 342 AM EDT Tue Aug 22 2017

A cold front will sweep across the region this morning into early
afternoon, with winds shifting out of the NW and becoming quite
gusty due to a tight gradient and developing overlake instability.
Widespread advisory winds, with low end Gales expected in Whitefish
Bay and through Presque Isle light for this afternoon and evening.
Advisory speeds will be common in most nearshore waters into
Wednesday before higher pressure approaches Wednesday night into
Friday. Showers and isolated non severe storms ahead of the front
this morning.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT through late tonight for MIZ016-019>021-
     025-031.
LH...SMALL CRAFT ADVISORY until 6 PM EDT Wednesday for LHZ345-346-349.
     GALE WARNING until midnight EDT tonight for LHZ347-348.
LM...SMALL CRAFT ADVISORY until 6 PM EDT Wednesday for LMZ323-341-342-
     344>346.
LS...SMALL CRAFT ADVISORY until 6 PM EDT Wednesday for LSZ322.
     GALE WARNING until midnight EDT tonight for LSZ321.
&&

$$

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



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