Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 181046

Area Forecast Discussion
National Weather Service Gaylord MI
646 AM EDT Tue Jul 18 2017

.NEAR TERM...(Today through Tonight)
Issued at 320 AM EDT Tue Jul 18 2017

...Classic mid-summer day then perhaps some showers tonight...

High impact weather potential...a few non-severe thunderstorms
late today and tonight.

High pressure extends into lower MI from the se. A healthy surface
low was over Hudson Bay, with a more disorganized low in the central
high plains. A cold front connects these two lows, currently pushing
into ne and central MN. Some weakening deep convection is found
along the front, with decaying showers as close as n central WI
and far western upper MI. Closer to home, skies are mostly clear,
with some cirrus edging in from the nw, and a touch of fog in a
few spots. For the most part, we look to squeeze in another quiet
and warm summer day before precip chances make a legit push into
the area tonight.

Cold front will push into central upper MI by this evening, and will
not quite have exited ne lower MI by 8am Wed. Precip chances will
mostly be associated with fropa. There is a window for some decaying
showers to sneak into eastern upper MI today. This may occur as
ongoing (decaying) convection moves in, and also/later as new
convection fires in central upper MI and cold front interacts with
weak lake breeze activity (pressure gradient ahead of front is
generally too tight to allow for lake breezes, but relaxes in the
vicinity of the front). Otherwise, the sw pre-frontal surface winds
off of Lake MI will provide a stabilizing influence on eastern upper
MI. Will expand chancy pops today across a larger portion of Chip/
Mack Cos, but still keep those pops west of I-75. No precip thru
00z/8pm in northern lower MI, as surface dew points only in the
mid 50s to near 60f will keep instability negligible.

Certainly better precip chances tonight as cold front crosses most
of northern MI. Narrow enhanced-moisture band and associated
instability ridge will fold over across northern MI just ahead of
the front. This will not be at all impressive; MuCape values should
reach the 500-750j/kg range. This instability will be found in
eastern upper MI (especially w of I-75) this evening, push into nw
lower MI toward midnight, and proceed across northern lower MI while
weakening overnight. Precip chances will be highest and last longest
in eastern upper MI, with western Chip/Mack seeing pops decrease
late in the overnight. Sct pops only in northern lower MI, and
mostly after midnight (nw lower MI coast could get in on the action
a touch sooner). Instability only requires a low-end mention of
thunder, and nothing svr is expected. However, some locally heavy
rain is possible, especially in eastern upper MI.

Max temps upper 70s to near 80f eastern upper MI, near 80f to the
mid 80s northern lower. Cooler on some of the beaches, especially
Lake MI. Min temps a bit on the warm side, near 60f in eastern
upper and low/mid 60s northern lower.


.SHORT TERM...(Wednesday through Thursday)
Issued at 320 AM EDT Tue Jul 18 2017

..Occasional chances for showers and a few thunderstorms...

High Impact Weather Potential: Fairly minimal aside from monitoring
thunderstorm threat through the forecast period.

Pattern Forecast: Progressive zonal flow across the northern tier of
the CONUS into southern Canada (sandwiched between strengthening
ridging across the southern CONUS and closed low pressure over
northern Canada) is expected to persist right through the end of the
short term forecast period. Pieces of energy rotating into the Pac
NW will quickly race through the flow, eventually pushing across the
Great Lakes/Ohio Valley during the midweek timeframe accompanied by
at least a chance for a few showers and thunderstorms.

Primary Forecast Concerns/Challenges: Tuesday night`s lead mid level
energy and attendant cold front will continue to push across eastern
sections of the outlook area Wednesday morning. Inherited chance
PoPs through midday Wednesday (mainly south of M-72...highest near
Saginaw Bay) will continue to suffice as unfavorable frontal timing
and limited remaining moisture ahead of the front should warrant
nothing more than lingering isolated to scattered shower activity.
Will continue to keep thunder wording out of the forecast Wednesday
morning as convective trends diminish Tuesday night as a result of
the loss of daytime heating and precip outrunning the greatest
instability upstream. The envelope of solutions widens slightly as
uncertainly grows Wednesday afternoon through Thursday. Current
indications suggest a weak bubble of high pressure sliding overhead
allowing for a partly to mostly sunny Wednesday afternoon and
evening. However, the next wave is progged to quickly approach the
region Wednesday night/Thursday. As was mentioned by the prior
shift, low level jet placement, deep layer moisture and instability
gradient all suggest that the greatest activity will pass to our
south leaving it difficult for moisture transport this far north.
Certainly the threat for scattered showers and perhaps a few rumbles
of thunder can`t be ruled out, but rather low PoPs will do as plenty
of dry time is expected as well.

.LONG TERM...(Thursday night through Monday)
Issued at 320 AM EDT Tue Jul 18 2017

High impact weather potential: Renewed chance of thunder this
weekend; otherwise, minimal.

A rather progressive pattern continues across the northern regions
through the upcoming weekend with several pieces of energy zipping
through the region. At this time, the greatest threat for additional
showers and perhaps thunderstorms appears to arrive Saturday-
Saturday night; however, the details remain far from clear. The
recent guidance trend of a wet bias in the extended period makes it
hard to jump fully on board that northern Michigan experiences
widespread appreciable rainfall this weekend, or anytime through the
end of the period. In fact, either way you slice it, there`s good
guidance agreement that Canadian high pressure sinks into the upper
Mississippi Valley and western Great Lakes to kick of the start of
next week...bringing any threat of wet weather to an end.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 646 AM EDT Tue Jul 18 2017

VFR. Some showers possible tonight.

High pressure is starting to lose its grip on lower MI, but won`t
fully do so until tonight, when a cold front moves in from the nw.
Quiet today; has been a touch of ground fog at MBL, but that
won`t last long. Some showers possible tonight, mainly toward and
after midnight. This will likely fall out of a mid-cloud deck,
and VFR conditions are anticipated, though brief restrictions are
not out of the question.

Sw winds developing today, going light tonight.


Issued at 320 AM EDT Tue Jul 18 2017

S to sw surface winds will persist today and this evening, before
a cold front crosses the region overnight into Wed morning. Parts
of northern Lake MI and Lake Huron will certainly be choppy today,
but conditions should come up short of advisory levels. Lighter nw
winds will occur behind the front Wed, though will be just a touch
breezy near Presque Isle Lt on Lake Huron.




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