Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 160355
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1155 PM EDT Sat Jul 15 2017

.NEAR TERM...(Tonight through Sunday)
Issued at 229 PM EDT Sat Jul 15 2017

...A few thunderstorms through early this evening...

High impact weather potential...Small chance for an isolated severe
thunderstorm across parts of northwest lower and Lake Michigan.

Pattern synopsis/forecast...Remarkably persistent NOAM pattern going
through another amplification phase as Intermountain West ridge
expands further north. Initial front-side shortwave trough and
attendant cold front diving quickly southeast into the northern
Lakes within mean overhead troughing this afternoon, with secondary
and stronger wave quickly on its heels in central Ontario. Brief
moisture return ahead of the lead wave has spread across the area,
although core of deepest moisture remains to our west across
Wisconsin. Combine that with warming temperatures, and the
destabilization process has begun, with once again most of that
taking place on the other side of the big pond. Cold front/mid level
support about set to catch up to this instability axis, and suspect
convection will soon fire across central upper Michigan and northern
Wisconsin. Mid level flow remains very progressive through the near
term, with intial mid level wave exiting stage right quickly this
evening. Attendant cold front slows in the process, waiting for
arrival of that secondary stronger piece of energy to amplify and
dig into our area later tonight and Sunday to get a more definitive
push off to the south.

Primary forecast concerns/challenges...Addressing severe
thunderstorms concerns through early this evening. Cloud and
temperature trends through the remainder of the period.

Details...Placement of instability gradient and deep layer flow
suggests much of this late afternoon/early evening showers/storm
activity should stay just to our west, although western extent of
developing squall line type feature is likely to clip parts of
northwest lower Michigan as it drops south. Per trends, it looks
like areas southwest of the Grand Traverse Bay region will be most
under the gun, particularly near Manistee and into northern Lake
Michigan. That area remains under a marginal risk, and if
convection/cold pools become as organized as some hi-res guidance
suggests, definitely could be looking at a few severe wind gusts in
that region. Just not overly confident of shower/storm coverage
further east along the front as moisture and instability fall off
quickly. While main activity ends quickly this evening, may see a
few additional lighter showers develop overnight along slowly
southward dropping cold front and with arrival of stronger mid level
dynamics tied to approach of that secondary wave.

Sunday continues to look like another one of those rather raw and
cool days as mid level wave further amplifies on its southeast
journey just to our northeast. Pattern recognition as well as cross
section moisture analysis suggests plenty of low clouds once again,
especially across north central and northeast lower Michigan. While
moisture falls off quickly above the H8 level, moisture in the near-
surface layer looks deep enough to support some potential
sprinkle/drizzle activity at times. Drying is much more aggressive
north of the big bridge, suggesting skies will become mostly sunny
across that area during the afternoon. While temperatures don`t look
quite as cool as the most recent cool-down, expected highs in the
upper 60s/lower 70s is still several degrees below normal for this
time of year.

&&

.SHORT TERM...(Sunday night through Tuesday)
Issued at 229 PM EDT Sat Jul 15 2017

Any lingering low clouds should dissipate Sunday evening as high
pressure/subsidence promote clearing skies. In addition, diminishing
winds are expected to lead to excellent radiational cooling
conditions overnight Sunday. Will undercut the blend with low lying
spots likely dropping down into the middle 40s. High pressure in
control Monday into much of Tuesday. This is expected to lead to
warming temperatures and clear to partly cloudy skies. Humidity
levels will be on the rise Tuesday afternoon as precipitable water
values approach 1.50 inches. An approaching weak cold front could
spark a shower or thunderstorm across western Chippewa/Mackinac
Counties by late Tuesday. Highs Monday in the comfortable middle
to upper 70s. Lows Monday night mainly in the 50s with highs
Tuesday in the increasingly muggy upper 70s to middle 80s.

.LONG TERM...(Tuesday night through Saturday)
Issued at 229 PM EDT Sat Jul 15 2017

...More Rain?...

High impact weather potential...Another extended period of wet
weather possible Tuesday night through Thursday.

Problem with the day 4 thru 7 forecast is that a cold front looks
like it will drop into the region Tuesday night/Wednesday and then
stall. Front will be a focus for precipitation in the Tuesday night
through Thursday timeframe. So details depend on where the front
stalls and will be hard to pin down next several model cycles.

Cold front drops into region Tuesday night/Wednesday and stalls as
it runs into upper ridging across the southern U.S. Model soundings
show good amount of CAPE (1000 - 2000 j/kg) ahead of the front. Wave
develops along the front over the northern Midwest Wednesday night
and pushes into the NW great lakes region. Thunderstorms ahead of
the wave drop into WI/W UP and then drop SE into MI Thursday. Front
finally pushes all the way through CWA Thursday night with strong
but compact high moving in Friday. At this time, Friday and much of
Saturday appear precipitation-free.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1154 PM EDT Sat Jul 15 2017

Low pressure is across the Straits with a cold front stretching
down through central Wisconsin. Narrow line of thunderstorms ahead
of the front continues to sag down through Wisconsin...with a few
showers still moving through parts of northern lower Michigan.
Showers and perhaps a thunderstorm or two remain possible into the
overnight hours...until the front moves through.

Otherwise...VFR conditions persist. Cold front will slip down
through northern lower Michigan overnight. Behind the front...guidance
continues to suggest low cloud cover (MVFR to IFR) developing/expanding
through the region late overnight with arrival of shallow cool
airmass...and persist through a chunk of Sunday. Some lower cloud
cover is noted behind the front across upper Michigan...but not
widespread and not as low as guidance suggests...for the moment
anyway. We will see.

&&

.MARINE...
Issued at 229 PM EDT Sat Jul 15 2017

Southwest winds, at times a bit gusty this afternoon and
early evening, are expected to veer quickly to the north overnight
as a cold front crosses the region. This wind-shift will be
accompanied by a few showers and thunderstorms, with the greatest
threat for thunderstorms expected across northern Lake Michigan
through early this evening. Besides lightning, any storms that do
form will be capable of producing brief very gusty and erratic winds
as well as enhanced wave action. North winds, at times gusty,
continue on Sunday. Small craft advisories may be needed on Lake
Michigan Sunday, especially along and south of Sleeping Bear Dunes.
Lighter north to northeast winds expected Sunday night and Monday.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...SMALL CRAFT ADVISORY from 8 AM to 6 PM EDT Sunday for LMZ344>346.
LS...NONE.
&&

$$

NEAR TERM...MB
SHORT TERM...AS
LONG TERM...MB
AVIATION...BA
MARINE...MB



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