Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 251636
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1236 PM EDT Tue Jul 25 2017

.UPDATE...
Issued at 1020 AM EDT Tue Jul 25 2017

Debris clouds from upstream convection over WI/MN starting to
spill into our southwestern counties at this hour, and not eroding
much as it does so. Have increased cloud cover forecast a bit for
late morning into the afternoon to account for this, but still
expect a decent amount of sunshine across most of northern
Michigan. Last few runs of the HRRR and RAP have been wanting to
bring some decaying showers from central WI into our southwestern
counties early this evening, but think the airmass overhead will
still be dry enough to erode any encroaching weak showers. Latest
regional radar loop confirms this is currently the case as showers
move into drier air over eastern WI. Moisture advection won`t
really get going until this evening across northern MI. Inherited
forecast otherwise largely on track for today with highs in the
mid 70s over eastern Upper and near the lakeshores, around 80
over interior northern Lower.

&&

.NEAR TERM...(Today through Tonight)
Issued at 352 AM EDT Tue Jul 25 2017

...Increasing shower chances tonight...

High Impact Weather Potential...Minimal. Thunderstorms possible
late mainly in eastern upper Michigan. Severe threat low.

Pattern Synopsis...Overnight upper air/satellite and surface
analysis reveals surface high pressure squarely over
Michigan...just downstream of low amplitude mid level ridging
pressing into the western Great Lakes. Hence plenty of clear skies
out there for the moment. Upstream...compact short wave and
attending surface low evident over the Saskatchewan/Manitoba
region with suppressed heights and trailing cold front pressing
into the northern high plains. Secondary surface low is in the
Dakotas with a narrow corridor of moisture/instability nosing
through the northern plains and a couple clusters of storms
ongoing.

Primary Forecast Concerns...Minimal through the near term. High
pressure will continue to dominate the region today and this
evening as it drifts into the eastern lakes and we pick up a bit
of a southerly flow with warmer temperatures anticipated. Lots of
sunshine overall...although some mid and high cloud cover
(convective debris from upstream) will be passing through the
region.

Meanwhile...aforementioned upstream short wave and surface low
pressure will advance into northern Ontario by Wednesday morning...
while upstream instability axis and cold front begin to fold into
the western Great Lakes. Will likely see renewed convective
development in the upper Midwest later this evening and into the
overnight hours that will make a run at the northern/western part
of the CWA toward morning. Decent low-mid level shear profiles
develop overnight particularly across upper Michigan owing to
strong mid level flow (around 50 knots) along the southern
periphery of the upper low. However...in typical fashion...only
modest elevated instability makes it into the region through early
Wednesday morning with MUCAPE values maybe around 500 J/KG just
poking into the CWA. So while shear profiles are rather
impressive...severe weather probabilities (through early Wednesday
anyway) will remain rather low as depicted in the current SPC Day
One outlook.

&&

.SHORT TERM...(Wednesday through Thursday)
Issued at 352 AM EDT Tue Jul 25 2017

...Severe potential Wednesday?...

High Impact Weather Potential...There is a chance for severe
thunderstorms on Wednesday.

Pattern Synopsis/Forecast...The cold front looks to be on target to
move through the forcast area sometime during Wednesday evening. So
the intial round of storms will move through the forecast area,
during the late afternoon. GFS model soundings still show a cloud
cover out ahead of the front so the CAPE, while good
(SBCAPE>1000J/kg) the winds are leaving us in a marginal situation
with the sfc-6km around 29kt and the 500 mb wind around 30 knots, as
a jet streak of 50 knots moves east of the region before the
instability gets here. Otherwise, the cold front continues to push
south, slowly, so that rain showers will continue into Thursday
afternoon in portions of N Lower. High pressure then builds into the
region for Thursday night.

Primary Forecast concerns...The question will be whether there will
be severe weather on Wednesday. With the models showing that cloud
cover ahead of the front, and the shear values being marginal, think
that severe storms are possible, but not likely.

.LONG TERM...(Thursday night through Monday)
Issued at 352 AM EDT Tue Jul 25 2017

...High pressure looks to dominate the weekend...

High Impact Weather Potential...Elevated fire weather conditions
possible for Friday, Saturday, and Sunday but that is probably a low
chance probability.

Extended (Friday through Monday)...As has been said the last few
nights, the region is dominated by high pressure for Friday through
Sunday evening on all of the models. The issue we run into is that
the GFS is continuing bring showers and thunderstorms in Sunday
night through Monday. The ECMWF however, gets us into a Rex block
on Sunday and Monday and keeps the rain out of the region.

Otherwise, the main thing through this period is that temperatures
will rise from the cool down on Thursday back to normal by Saturday
and continue on to Monday.

Also as was mentioned yesterday, things will dry out as far as the
min RH is concerned for Friday and Saturday. As was stated last
night, the RH doesn`t look like it drops below 30% at this point, so
will continue to watch how this scenario through the coming days,
especially if the ECMWF Rex Block shows up and allows things to dry
out for Monday, and possibly into Tuesday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1227 PM EDT Tue Jul 25 2017

High pressure starting to drift east of the area this afternoon
with some cirrus spilling into parts of northern Michigan from
upstream convection over WI. Also a bit of diurnal cu starting to
pop across the area. Light and variable winds early this afternoon
will soon transition to southerly as the high pushes east, but
will remain around 10 knots or less the rest of today.

Heading into tonight, low pressure over central Canada will drag a
cold front into the Upper Midwest. Increasing SW flow out ahead of
the front will likely lead to some LLWS overnight, particularly
affecting the northern terminals. Showers and thunderstorms will
develop out ahead of the front, likely holding off until late
tonight at PLN. Rain chances will then progressively spread east-
southeast across the rest of northern Lower MI through Wednesday
morning with a better chance of thunderstorms Wednesday afternoon.

&&

.MARINE...
Issued at 352 AM EDT Tue Jul 25 2017

Light winds this morning will give way to increasing southerly
flow later today and particularly tonight...as a cold front
presses into the region from the west. Small craft advisory
winds/waves are likely to develop tonight...particularly on Lake
Michigan and Whitefish Bay and continue into Wednesday.
Winds/waves will gradually diminish through the day Wednesday and
Wednesday night.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...SMALL CRAFT ADVISORY from 2 AM to 8 PM EDT Wednesday for LMZ323-
     341-342-344>346.
LS...NONE.
&&

$$

UPDATE...MK
NEAR TERM...BA
SHORT TERM...JL
LONG TERM...JL
AVIATION...MK
MARINE...BA



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