Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 141732

Area Forecast Discussion
National Weather Service Gaylord MI
132 PM EDT Mon Aug 14 2017

Issued at 1050 AM EDT Mon Aug 14 2017

High pressure has been dislodged, with low-level southerly flow in
place ahead of a complex frontal zone that stretches from northern
Ontario into the central high plains. A few showers have been
percolating this morning, mainly in n central and ne lower MI,
though with a few also seen up by Whitefish Bay. More widespread
shower activity is w of Lake MI. Thickest cloud cover in near
Saginaw Bay, with at least some breaks elsewhere.

Gist of the forecast is largely unchanged. Upstream shortwaves
will move toward central Superior and central WI by early evening.
Resulting height falls aloft, combined with diurnal heating, will
support further shower development this afternoon, especially away
from Lake MI. Various CAMs are in strong agreement with this
scenario, with showers/t-storms most numerous east of I-75 in
northern lower MI.

Stronger mid-level flow is decidedly downstate, though 0-6km bulk
shear values will try to perk up toward 30kt in northern lower MI.
MlCape will peak at around 1k j/kg in spots late this afternoon
(centered on 21z/5pm HRRR/Nam runs). There will be locally
enhanced low-level shear along lake breeze boundaries, though
cells will move over an increasingly stable BL soon after
encountering said boundaries. This all suggests that some stronger
storms are well within the realm of possibility.


.NEAR TERM...(Today through Tonight)
Issued at 336 AM EDT Mon Aug 14 2017

...Increased shower/thunderstorm chances today...

High Impact Weather Potential...thunderstorms are likely today
into this evening. A few stronger storms possible.

Pattern Synopsis/Forecast...Some semblance of an omega blocking
pattern is in place across NOAM this morning with the eastern
anchoring closed low still in the Hudson Bay region. Broad surface
high pressure spans much of the eastern CONUS with overall quiet
weather continuing across northern Michigan...although quite a bit
of high cloud cover is streaming through the region and there is
some spotty elevated radar returns on radar due to increasing
warm advection forcing.

Meanwhile...a couple short waves of interest within the broader
trough pattern. One fairly strong wave (and attending showers/storms)
is moving eastward through Minnesota...and a second wave (with
additional showers/storms) slipping southward through far western
Ontario. These two waves will phase but dampen while moving
through the Great Lakes later today and tonight.

Primary Forecast Concerns...Shower and thunderstorm chances
through tonight.

Today starts out fairly quiet with a fair amount of high cloud
cover...although there may be some spotty warm advection
showers/sprinkles already moving through the region this morning.
Aforementioned short wave phasing will be slow to develop...with
the main vorticity axis/QG-forcing for ascent and attending precip
just moving through Wisconsin by the end of the afternoon.
But...we will see increasing southerly flow/warm and moist
advection ahead of the trough into the region...kicking surface
dewpoints into the upper 50s/lower 60s with the higher dewpoints
pooling across NE lower Michigan. Forecast soundings this
afternoon suggest as much as 1200 J/KG MLCAPE across NE lower
Michigan. Larger scale synoptic forcing remains upstream through
the afternoon. But with the development of the typical smaller
scale low level convergence axis across NE lower Michigan...showers
and some thunderstorms are certainly a good bet...particularly
east of I-75.

Severe thunderstorm threat is not great...but better than in
recent days with not-to-shabby instability...mid level winds
increasing through the day to 20 to 30 knots...freezing levels
hovering around 10K FT and a bit of an inverted V look at the
bottom of the soundings supportive of gusty winds. SPC DAY 1
outlook keeps us in general thunder...but I will mention a few
stronger storms possible this afternoon across NE lower Michigan.

Tonight...phasing short wave trough slated to cross through the
region later this evening and overnight. With daytime heating...
anticipate additional/renewed convective development across
Wisconsin into Iowa/Illinois today ahead of the wave...with
diminishing convection crossing through lower Michigan tonight.
Hi-res guidance suggests this will be mainly south of M-72...but
we will just have to see how things evolve as we go through the


.SHORT TERM...(Tuesday through Wednesday)
Issued at 336 AM EDT Mon Aug 14 2017

Perhaps a leftover shower across eastern zones Tuesday morning,
otherwise ridging at the surface and aloft through Wednesday morning
should ensure precipitation free conditions. The next trough will
start to bring chances for showers across southwest zones late
Wednesday. Continued temperatures of right around climo (some spots
a little above Wednesday).

.LONG TERM...(Wednesday night through Sunday)
Issued at 336 AM EDT Mon Aug 14 2017

...Potential for heavy rain Wednesday night into Thursday...

Pacific energy is expected to carve out another trough which will
increase shower and thunderstorm chances through Friday. There is
even a decent chance for heavy downpours Wednesday night into
Thursday as precipitable water values climb to near 2 inches.
Another northern stream trough may lead to a few showers Saturday as
well. Short wave ridging will likely end the precipitation threat
for Sunday. Temperatures should be within a couple of degrees either
side of climo.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 132 PM EDT Mon Aug 14 2017

Shra/tsra near APN this afternoon/early evening. Some fog tonight

Showers and t-storms are already developing early this afternoon
in n central and ne lower MI. This activity will continue to
percolate, largely staying inland of PLN/TVC/MBL, but sporadically
impacting APN. Additional activity in WI will slide eastward,
perhaps approaching MBl tonight. PLN/APN most likely places to see
fog tonight (especially APN).

Light westerly winds replaced by lake breezes this afternoon.
Light winds tonight and Tuesday.


Issued at 336 AM EDT Mon Aug 14 2017

Winds and waves will remain below small craft advisory criteria
through midweek. Thunderstorm threat will increase on Lake Huron
this afternoon with a few stronger storms possible...which could
produce locally higher winds and waves. Diminishing shower/
thunderstorm threat tonight into Tuesday.




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