Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 261917

Area Forecast Discussion
National Weather Service Gaylord MI
317 PM EDT Fri May 26 2017

.NEAR TERM...(Tonight through Saturday)
Issued at 317 PM EDT Fri May 26 2017

...At least the holiday weekend will start out nice...

High impact weather potential...none.

A narrow ridge of high pressure is crossing MI today, separating a
departing system (over New England) and an incoming frontal zone
(MN/Iowa/MO). Deep convection persists with the upstream system over
eastern Iowa/nw IL, while a few showers are also present over
western Superior and the MN arrowhead. Closer to home, a decent
enough day is in progress, with varying amounts of stratocu away
from lake shadow areas. Some marine fog/stratus also persists over
the still-chilly Great Lakes, thanks to surface dewpoints in the 50-
55f range. There may be some small precip chances as shortwaves
split around the forecast area to the north and south. But the start
of the weekend still looks like the best part of the weekend.

Tonight...prominent MCV is expected to drive an intensifying cluster
of storms eastward across the southern lakes this evening. Forcing
associated with this vort max is already contributing to some virga,
seen on APX radar over central Lake MI. There is an ENE-ward
movement with the convective cluster presently, but a trend toward a
due-east movement is expected as it blasts thru a 500mb ridge axis.
Still, northernmost fringe of the MCS has a shot of clipping far
southern portions of this forecast area. Not a great shot, but will
maintain a slight chance for showers for the 1st half of the night
for the Frankfort-Lake City-Gladwin areas and points south.

Otherwise, will see an expansion in layered mid/high clouds, as
shortwaves transit the southern Lakes and Lake Superior from w to e.
That will to some degree limit potential fog/stratus redevelopment
(a concern given most temp/dew point spreads are less than 20f).
However, will still add a mention of patchy fog in some areas of
northern lower MI for late tonight.

Min temps upper 40s to around 50f.

Saturday...bubble high will still be over lower MI and se Ontario to
start the day. Incoming front will help dislodge that, and will edge
its way toward eastern WI and central upper MI by the end of the
day. Outside of any early morning fog/stratus, a solidly partly
sunny day is anticipated, with a reasonably healthy cu field
appearing in the afternoon. Nam is likely overdoing BL moisture and
associated sbCape, and anticipate Cape values struggling to reach
triple digits. With lake breezes charging inland during the
afternoon, it is not completely out of the question we could cook
off a stray shower in the interior of northern lower. But this
chance is not large enough to include in the forecast at this time.
A somewhat better chance exists in far western Chip/Mack Cos, very
late in the day. Remnant convection might try to sneak in from the
west (where a somewhat more moist airmass exists), and where the
front serves as a potential trigger.

Still looks like the warmest day of the weekend, with highs mainly
in the 70s, cooler on the beaches. Would not be surprised to see a
stray 80f or two in northern lower MI.


.SHORT TERM...(Saturday night through Monday)
Issued at 317 PM EDT Fri May 26 2017

...Cooler and showery for Sunday and Memorial Day...

High impact weather potential...Minimal. Chance of thunderstorms
Sunday and Monday with a marginal risk for a severe storm near
Saginaw Bay on Sunday.

Pattern Synopsis/Forecast...Weak upper ridge axis will push east of
the Upper Great Lakes Saturday evening. Upper flow then turns SW as
a digging trough drops into the Upper Midwest, carrying a few weak
vort maxes across northern Michigan through daybreak Sunday. The
main trough axis and an associated weak surface low will rotate
across northern MI Sunday afternoon/evening. As another wave of
energy drops south from Central Canada and is absorbed into the
parent trough Sunday night into Monday, the system will morph into a
closed upper low that will rotate across Upper Michigan/Lake
Superior, resulting in another period of unsettled weather. Moisture
looks to be ample (at least on Sunday), with PWATs climbing above
1". Slightly drier air will sweep in Sunday night into Monday with
PWATs around 0.75"...still sufficient for lingering shower activity.

Mostly cloudy skies, showers, and cooling 850mb temperatures will
result in a cooler day on Sunday with highs lucky to reach 70
degrees across interior northern Lower. 60s near the lakes and
across eastern Upper. The upper low will result in an influx of
cooler air aloft on Memorial Day with highs a few degrees cooler.

Primary Forecast Concerns...Shower/thunderstorm chances through the
latter half of the holiday weekend.

Weak vort maxes lifting northeast across the area Saturday night are
not expected to produce enough lift to support more than a few
showers. Moisture will be increasing from west to east, but the lift
just doesn`t look very strong. Sunday continues to look like the
wettest day of the holiday weekend as the main upper trough and a
surface low move across northern MI. Strongest omega from DPVA and
divergence aloft will occur from afternoon into evening coincident
with the strongest daytime heating. That being said, cloud cover
will be fairy extensive on Sunday, which will limit diurnal
instability. Depending on the track of the surface low, which will
limit northward advection of higher theta-e air (considerable model
differences with regard to this), SBCAPEs could be a few hundred
J/kg or slim to none. General model consensus seems to be converging
towards a solution tracking the low through Saginaw Bay which would
keep the bulk of the instability just to our south. Still, the
strong lift, favorable moisture, marginal instability, and decent 0
to 6km bulk shear would make it tough to rule out a few
thunderstorms, including perhaps a better organized storm down
towards Saginaw Bay. SPC does have our far southeast CWA clipped by
a Day 3 marginal risk.

Once the main upper trough and surface low exit the area late Sunday
evening, the drier air and loss of lift should lead to a break in
rain for most areas the rest of the night (slightly better chances
lingering across eastern Upper). Vort maxes rotating around the
closed low on Memorial Day will lead to scattered shower activity
again, though likely less widespread than Sunday. Can`t rule out a
few thunderstorms, but forcing will be weaker than Sunday.


.LONG TERM...(Monday night through Friday)
Issued at 317 PM EDT Fri May 26 2017

Unsettled weather continues into the first half of the extended
period.  A closed low will set up shop between Superior and Hudson
Bay, rotating occasional waves over the Great spokes
around a wheel.  So timing the "wet" vs. "dry" periods will be the
forecast challenge Monday night through Wednesday.  The location of
this low will also be ideal (or "unideal" depending on your
perspective) for dragging cooler Canadian air down across the
lakes...keeping us cooler than normal through the aforementioned
time frame.  On the bright side, it looks like a ridge of high
pressure will build in from the west for Thursday and Friday...and
kick this low eastward so we can end the work week on a dry note,
with temperatures moderating to just shy of climo.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 131 PM EDT Fri May 26 2017

Some potential for brief MVFR conditions tonight and Sat morning,
but mostly VFR.

Narrow ridge of high pressure will cross MI today, while an
incoming front makes only slow progress across MN/Iowa/MO. Main
area of shower/tsra activity with the incoming system will pass to
our south tonight. Low levels remain moist, and with the Great
Lakes still chilly, marine fog/stratus may start to expand out
again tonight. For now, localized MVFR conditions (mainly cigs)
are the main concern.

Light winds.


Issued at 317 PM EDT Fri May 26 2017

Weak high pressure will be the main player into early Saturday.
This will keep winds/waves unimpressive, with lake breezes the
dominant influence each afternoon/evening. Winds will become
westerly by late Sunday as a front passes, though mainly light
winds are still expected. Marine fog/stratus will continue to
bedevil some of the nearshore waters.




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