Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 221728

Area Forecast Discussion
National Weather Service Gaylord MI
128 PM EDT MON AUG 22 2016

Issued at 946 AM EDT Mon Aug 22 2016

High pressure in the lower Ohio Valley is extending ridging into
lower MI. This is backing our low-level winds to the w this
morning, and sw this afternoon, while ushering in warm advection.
Last batch of lake-induced cloud cover is about to exit se
sections. Associated sprinkles/light showers appear to have ended,
per radar. Airmass is getting too warm for additional lake
contributions, and that trend will only accelerate.

Meanwhile, larger area of warm-advection related cloud cover is
advancing ese-ward across Superior. Some shower activity is noted
(particularly near and north of the Keweenaw), but in general a
downward trend is noted in precip coverage. Showers should
continue to erode as they encounter drier air with se-ward extent,
and feel reasonably comfortable in keeping the forecast dry thru
early evening. Additional shra/tsra development is possible late
this afternoon over western upper MI, thanks to strong heating and
increasing warm advection. This activity may pose a precip threat
for our area after 00z, especially eastern upper MI.

Overall, have fine-tuned cloud forecast for the day, both for an
increasing cloud trend in eastern upper MI, and sct cu elsewhere.
Max temps are fine.


.SHORT TERM...(Today and tonight)
Issued at 354 AM EDT Mon Aug 22 2016

High impact weather potential: Very low/slight chance at a rumble
of thunder late this evening/overnight around the Straits.

Pattern synopsis and forecast:

High pressure was currently centered over the lower Ohio valley
early this morning. Fairly quick WNW flow aloft was overhead, while
a shortwave trough/closed low was over British columbia. The
associated sfc low was in srn Alberta with a cold front trailing
back through WA/OR. A stationary frontal boundary extends east of
the low, through srn Saskatchewan, with steep lapse rates aloft to
the south. There was some very weak and ill-defined vorticity
running through the WNW flow aloft into nrn MN, on the leading edge
of those steep lapse rates. Decent low to mid level WAA via a
weakish LLJ, has resulted in an area of clouds and light rainfall.
Those clouds are trying to push through Lake Superior, but across
nrn Michigan, we have seen most areas go through a gradual clearing
trend. We did still have good overlake instability that has overcome
the drying/clearing over the Manistee/Benzie and Wexford county
areas. Low level WNW flow has continued to produce scattered light
rain showers in this area.

This instability remains present through at least the morning, and
it`s not totally out of the question to see these scattered light
rain showers continue to pester the western GTV Bay region. Gotta
buy into the idea that low level warm advection over this time and
diurnal land based warming will bring about the demise of the
showers after sunrise. In the meantime, the showers in nrn MN are
expected to track well north of eastern upper, while daytime cumulus
and temperatures topping out in the low to mid 70s results in a
perfect summer day.

That weak wave in the WNW flow aloft does continue to march ESE
through upper Michigan this evening and overnight, with the
steepening lapse rates and low to mid level WAA resulting in our
chance for some developing showers. There is some remnant sfc based
CAPE off Lake Michigan, with SW pushing this up into the Straits
region for that very small possibility for a rumble of thunder.
Chance is so low, probably shouldn`t bank on it. lows ranging from
the middle 50s close to Saginaw Bay in the lightest wind flow and
clearest of skies, to the middle 60s in eastern upper under more
clouds and stronger low level winds.

.LONG TERM...(Tuesday through Sunday)
Issued at 354 AM EDT Mon Aug 22 2016

(8/23)Tuesday...As the 500 mb ridge begins to amplify tot he west,
the warm air moves north, forcing the baroclinic zone and the 500 mb
jet streak north and out of the forecast area. This should result in
a mainly sunny day and clear night. However, the return flow will
continue, warming the temperatures to be above normal again through
the night.

(8/24)Wednesday...The return flow looks to pump enough moisture into
the region at the sfc in preparation for the 500 mb shortwave trough
which is upstream of the Upper Great Lakes at 12z. The models have
been backing the timing of the shortwave off over the last several
runs, so now the rain doesn`t start in NW Lower until closer to 15z.
This may still back off more, but based on the current model runs,
have the rain spreading across the forecast area, but 21z with some
decent rains. Thunder will be there, as the instability will be on
the low side with the sfc LI`s of 0c to -2c, depending on the model.
Models then push dry air back into the region post frontal. The
ECMWF is a little slower than the GFS, but both have enough
agreement to go with a quick drying.

Extended (Thursday through Sunday)...As mentioned in the yesterday`s
forecast discussion, the pattern looks fairly progressive with a
decent wave that moves through the Upper Great Lakes every couple of
days. A pattern, that looks like it will continue going out through
through day 14. So Thursday and Friday look dry, with the next wave
moving into the region Saturday/Sunday with another round of rain.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 128 PM EDT Mon Aug 22 2016


High pressure in the Ohio Valley will move off to the east and
northeast. Warmer and eventually more humid air will back into the
region as the high exits. There is some risk for a shower or two
tonight from the Straits region northward, and have a VCSH mention
at PLN for part of the night. Otherwise, daytime cumulus will fade
away this evening, with partly cloudy to mostly clear skies.

Ongoing w to sw winds will becoming more emphatically sw, and will
increase tonight into Tuesday.


Issued at 354 AM EDT Mon Aug 22 2016

Remnant instability and moisture south of Sleeping Bear Point will
result in isolated to scattered rain showers into daybreak.
Otherwise, winds will be ramping back up again this afternoon and
tonight as a tighter SW flow pressure gradient sets up. Good
confidence in advisory level winds easily developing as we will
still have instability over the water. Best advisory level winds
will be over Lake Michigan/Straits and Whitefish Bay through
Tuesday and possibly Tuesday evening. More spotty advisory level
winds are possible in the remaining nearshore waters, mainly
Tuesday night.

Showers are also possible across the Straits region and
Whitefish Bay tonight.


.APX Watches/Warnings/Advisories...
LH...SMALL CRAFT ADVISORY from 5 PM this afternoon to 6 PM EDT
     Tuesday for LHZ345.

LM...SMALL CRAFT ADVISORY from 5 PM this afternoon to 6 PM EDT
     Tuesday for LMZ323-341-342-344>346.

LS...SMALL CRAFT ADVISORY from 5 PM this afternoon to 6 PM EDT
     Tuesday for LSZ321.



SHORT TERM...Dickson
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