637
FXUS63 KAPX 271936
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
336 PM EDT Sat May 27 2017

.NEAR TERM...(Tonight through Sunday)
Issued at 336 PM EDT Sat May 27 2017

...Slightly cooler Sunday with rain chances returning...

High impact weather potential...Minimal with a chance of
thunderstorms Sunday.

Pattern Synopsis/Forecast...A broad 500mb ridge axis currently
sitting overtop northern Michigan will slowly push east this
evening. Despite the expansive growth of a fair weather cumulus
field across interior northern Lower from favorable low level lapse
rates, subsidence from the ridge has been limiting vertical growth
and inhibiting any shower activity in our neck of the woods. Lake
breezes have been keeping coastal areas largely cloud free.
Convection has initiated over the central UP in the vicinity of a
weak mid level vort max currently riding up the ridge. Expect this
activity to stay west of our area and to gradually fizzle out
towards sunset. Better forcing will lift into northern Michigan
later this evening as a stronger shortwave currently generating
storms out over Iowa rides northeast along the ridge. The shortwave
will become more sheared out and lose some strength by the time it
approaches northern Lake Michigan, but it should still be sufficient
to trigger some showers over eastern Upper overnight...possibly a
few showers impacting northwest Lower. Temperatures will fall into
the low to mid 50s tonight.

Deep upper trough and closed low will drop from central Canada into
the Upper Midwest on Sunday. Broad trough of low pressure at the
surface will extend from the parent low over central Canada to a
secondary less-organized surface low lifting northeast through the
Ohio Valley. These features will generate scattered showers and
possibly some thunderstorms across northern Michigan during the day.
The best instability will come into play late morning and afternoon
before the surface trough causes southerly winds to veer westerly.
Deterministic models yield several hundred J/kg of SBCAPE mainly
over northern Lower, perhaps up to around 1000 J/kg in some areas.
Those higher numbers may be too optimistic if cloud cover is more
expansive and limits daytime heating. But a decent plume of theta-e
looks to nose into northern Lower with little to no capping in place
and PWATs climbing above 1", so expecting a shot at some
thunderstorms. Main limiting factor will be the lack of strong
forcing, as lift from the trough looks moderate at best. Lake
breezes will be a possibility once again and could contribute some
low level convergence. Assuming thunderstorms develop, severe
potential looks low for northern Michigan given limited instability
and forcing. Depending on the model, wind shear will be weak to
modest at best...so the threat of organized storms appears low. With
more clouds and cooling 850mb temperatures, Sunday will be a bit
cooler with highs in the 60s to low 70s.

&&

.SHORT TERM...(Sunday night through Tuesday)
Issued at 336 PM EDT Sat May 27 2017

...A little cooler and a little damp...

High impact weather potential...few non-severe t-storms early Sunday
night and again Monday afternoon/early evening.

Upper low will slowly drop over Superior on Monday, then eject out
to the ne equally slowly. Surface low over far northern Ontario will
move relatively little. Low heights will support cool temps, while
deep cyclonic flow and moisture will support precip. Precip and
temp trends are the main concerns.

Sunday night/Monday...cold front will finish crossing northern MI
Sunday night. Sct to perhaps numerous shra will accompany it, with a
stray non-svr t-storm still possible in the evening (with muCape
values still near 500j/kg). Some model differences re: exact timing,
but potential for a relative break in precip chances overnight as
dry slotting works in. Moisture wraps back in from the w and nw on
Monday, which will combine with diurnal heating to produce
increasing shower coverage as the day proceeds. In fact, model-
progged mlCape values are pushing back to the 500-700j/kg range
(aided by cool temps aloft). So a few thunderstorms could get going
again in the afternoon/evening, especially away from the Lake MI
shadow (wsw surface winds). But for now, sct pops will suffice.

Min temps mainly near 50f. Max temps low 60s eastern upper, mid
60s to lower 70s northern lower.

Monday night/Tuesday...cooler air continues to seep into the region.
Diurnal component to precip will fade out, and in general pops will
decrease Monday night. Eastern upper may be an exception, closer to
the deeper moisture spiraling around the low to our north. Return of
diurnal heating Tue will help expand pops again, but again no higher
than chancy/sct. Instability is getting shallower as cooler airmass
invades, and will refrain from mentioning thunder for now.

Min temps mainly upper 40s. Max upper 50s to mid 60s.

&&

.LONG TERM...(Tuesday night through Saturday)
Issued at 336 PM EDT Sat May 27 2017

...Remaining cool with decreasing shower chances...

High Impact Weather Potential...None.

Upper level trough continues to spit out weak disturbances leading
to more isolated to scattered showers through Wednesday. This trough
continues across the region through the period but becomes centered
more off to our northeast by late in the week into next weekend.
Meanwhile, weak surface high pressure builds in from the northwest.
This should lead to mainly precipitation free conditions starting
Thursday but with cooler than normal temperatures. The dry weather
is not a slam dunk however as additional energy could still easily
move through the northwest flow aloft which is why shower chances
return Friday night/Saturday. We just can`t seem to break this
pattern and no pronounced or prolonged warmth foreseen over at least
the next 7 to 10 days. Highs mainly in the 60s, though a few lower
70s are possible Friday and Saturday. Lows in the cool lower and
middle 40s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 148 PM EDT Sat May 27 2017

Extensive fair weather cu field has developed across interior
northern Lower this afternoon but lake breezes are keeping coastal
areas, including most TAF sites, largely cloud free. VFR conditions
will continue through the period with light winds. Scattered showers
expected to push in from the west Sunday morning after daybreak
with increasing cloud cover.

&&

.MARINE...
Issued at 336 PM EDT Sat May 27 2017

Lake breezes will diminish tonight with winds becoming light and
variable overnight. In the absence of any strong features moving
through, a rather weak pressure gradient will again allow for
lake breeze development on Sunday, becoming a tad gusty in the
afternoon over the waters. Rain chances will increase through the
day. Gustier southwest winds expected to develop on Monday.

&&

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

$$

NEAR TERM...MEK
SHORT TERM...JZ
LONG TERM...AJS
AVIATION...MEK
MARINE...MEK