Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 190214

Area Forecast Discussion
National Weather Service Gaylord MI
1014 PM EDT Mon Sep 18 2017

Issued at 1014 PM EDT Mon Sep 18 2017

Subtle troughiness has set-up across the northern plains/upper
Midwest and just into the western Great Lakes. Upper jet core is
sliding up through Ontario with associated entrance region forcing
producing a stretched out but decaying band of precip from
Wisconsin up through parts of the U.P. Better defined short wave
is moving through the Midwest kicking off another area of
showers/storms through Illinois/Indiana. We are stuck in between
for the moment...with surface high pressure and a very deep dry
layer over the northern lakes.

Rest of tonight...jet forced precip still looking to decay and
slide up through the U.P. overnight...largely missing this CWA.
That said...current regional radar trends do suggest that tail end
of light precip might just clip parts of eastern upper MI
overnight into Tuesday morning...although given the bone dry
airmass...perhaps not much more than sprinkles. May end up adding
a low end chance for a shower/sprinkle up that way.

Otherwise...increasing mid/high cloud cover anticipated overnight
as that decaying band of precip slides on up through the region.


.NEAR TERM...(Tonight through Tuesday)
Issued at 306 PM EDT Mon Sep 18 2017

...A bit cooler warm-up begins Tuesday...

High impact weather potential...Nothing.

Pattern synopsis/forecast...High pressure centered directly overhead
this afternoon, bringing dry conditions and rather comfortable mid-
September temperatures along with it. A few clouds crossing the
landscape, a combination of some shallow diurnally-driven cumulus
and a few higher clouds. Southwest flow prevails aloft, with next
low amplitude shortwave trough within this flow regime punching up
through the Central Plains. Decent area of shower and thunderstorms
tied to this wave, making slow progress into the Corn Belt.

Overhead high pressure will slide off to the east tonight and
Tuesday as that Central Plains shortwave makes a run into the
Southwest Lakes by later Tuesday. Impressive low and mid level dry
air plume and dampening out of the wave itself will have plenty to
say on just how far north any attendant showers make it.

Forecast challenges through the near term center on
temperature/cloud trends and addressing that low end shower
potential on Tuesday.

Details: While high and mid level clouds will be on the increase
tonight, lack of forcing and a non-yielding sub H5 dry layer looks
to prevent any showers activity. Some clearing this evening and
breaks in the clouds overnight should allow for a decent nocturnal
temperature response, allowing temperatures to fall well into the
40s for most interior locations. These readings may just be cool
enough to kick off a bit of early morning field fog.

Guidance has really backed off on rain chances Tuesday, which makes
plenty of sense given shearing mid level support (overall trend will
be for slowly increasing heights with time despite approaching
shortwave) and maintenance of low and mid level dry air. Possible we
may see a few sprinkles scrap areas down near M-55, but definitely
should be no big deal. Clouds look to thin from northwest to
southeast, allowing solar insolation and an increasingly modified
airmass to bring temperature back up into the 70s, which is several
degrees above normal. This is only the beginning of the warm-up,
with much warmer readings set to arrive the second half of the week.
See the short term section below for those details.


.SHORT TERM...(Tuesday night through Thursday)
Issued at 306 PM EDT Mon Sep 18 2017

...Warming back up with a chance for some rain...

High Impact Weather Potential...Thunderstorms possible Wednesday
night into Thursday.

Pattern Synopsis/Forecast...Deepening cyclonic flow over the Pacific
Northwest and Hurricane Jose stalling somewhere off the East Coast
through the latter half of the week will lead to an amplifying upper
ridge developing in between over the Upper Great Lakes. An occluding
low over the Canadian Prairies is expected to push a weakening
frontal boundary into northern Michigan late Wednesday night into
Thursday, along with a weak shortwave rippling around the periphery
of the ridge.

Temperatures will gradually warm through the period (and even
beyond) with 700-500mb heights and 925-850mb temperatures climbing
to +2 to 3 standard deviations by Thursday. This will translate into
highs climbing through the 70s across eastern Upper and low to mid
80s for most of northern Lower.

Primary Forecast Concerns...Rain chances Wednesday night into

It remains to be seen how the weakening frontal boundary and
shortwave will interact with the anomalous upper ridge over the
region Wednesday night into Thursday. Increasing southerly flow will
efficiently draw Gulf moisture up into the Upper Great Lakes region
with PWATs climbing in excess of 1.5 inches and dewpoints in the
upper 60s Thursday...yes, upper 60s for late September in northern
MI. So there will be plenty of moisture available for rain and,
along the same line, sufficient instability. Forcing becomes the big
question and whether it will be strong enough to overcome the stable
layer of warm air just off the surface and subsidence aloft. Think
Wednesday night will provide the better chance for any rain with
only a small chance for a few showers and storms possibly
redeveloping on Thursday. Models are all in fairly good agreement
with at least a broken line of rain materializing, so there is
increased confidence in parts of northern Michigan seeing at least
some rainfall...certainly not a lot, though, and some areas may stay
dry altogether. Looking like enough instability to continue with
thunder in the forecast grids.

.LONG TERM...(Thursday night through Monday)
Issued at 306 PM EDT Mon Sep 18 2017

Well above normal temperatures will be the story through the
extended period as strong ridging builds across the eastern CONUS.
Still looks like we could make a run at record highs in some
locations. The main concern remains an earlier than progged break
in the block downstream that could allow the troughing over the
western CONUS to move in earlier than currently expected, and
bring temperatures closer to normal. But current indications
remain for well above normal temperatures to persist at least
through the weekend.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 800 PM EDT Mon Sep 18 2017

Solid VFR conditions will prevail across northern lower Michigan
tonight...with light winds and some high cloud cover moving
through. On Tuesday...short wave energy pushing into the Midwest
this evening will skirt through the lower lakes/Ohio Valley
region. This will push some thicker low cloud cover up into the
region as we go through the day...particularly up through NE lower
Michigan. Some light rain may work up into the Saginaw Bay/NE
lower Michigan area...but is expected to remain out of the
terminal sites.


Issued at 306 PM EDT Mon Sep 18 2017

No significant marine issues expected as both winds and waves
look to stay below advisory levels through at least Tuesday night.
North to northeast winds today, at times a bit gusty, will
steadily veer to a more easterly direction tonight and Tuesday.




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