Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 200500
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
100 AM EDT WED JUL 20 2016

.UPDATE...
Issued at 942 PM EDT Tue Jul 19 2016

Very quiet. High pressure is centered over southern Lake Huron,
drifting se. Diurnal cu is gone. Deep convection is occurring
upstream over nw MN, and a touch of associated cirrus will spill
into the region overnight. Differential temp advection will
contribute to steepening 700-500mb lapse rates very late over
eastern upper MI and northern lake MI, nearing 7.5c/km after 08z.
Some potential for some well-elevated convective elements,
resulting in virga and just maybe a few sprinkles toward dawn?
Won`t be including those at the moment, as certainly are concerns
that the Nam is returning too much moisture too far just to our w
and nw.

&&

.SHORT TERM...(This evening and overnight)
Issued at 256 PM EDT Tue Jul 19 2016

Upper ridge centered over the plains. Upper low over Quebec with
trough extending down the east coast. Another upper low just off
of Washington. Over the next couple days...ridge expands north and
east while Washington low lifts northeast through Canada. At the
surface...high centered over the Great Lakes. Low pressure over
the northern Rockies with a warm front extending into Iowa. This
warm front will lift north over the next couple days.

Not much sensible weather through early Wednesday with the high
moving across the Great Lakes. Warm front approaches from the
southwest but far enough away to keep precipitation chances out of
the forecast through early Wednesday. MCS looks like it will develop
along/north of the warm front across MN/WI overnight ahead of 40kt
LLJ. The MCS should drift SE through the night...possibly spreading
mainly high clouds into our region.

.LONG TERM...(Wednesday through Tuesday)
Issued at 256 PM EDT Tue Jul 19 2016

High impact weather potential: Very warm temperatures with heat
indices in the mid-upper 90s possible. Thunderstorms possible at
various times throughout the period.

Pattern synopsis/expected evolution: Northern Michigan sits in a
transition zone this afternoon between a strengthening ridge over
the center of the country and troughing over the northeast. However,
ridging will build northeastward tonight through Saturday providing
a return to very warm and humid conditions through the period as
~590 dam heights center overhead. Several waves are progged to ride
up and over the ridge in a typical "ring of fire" pattern, providing
several chances for showers and thunderstorms to impact the region.
A well-defined upper-level shortwave is expected to move through
southern Canada late in the weekend resulting in lowering heights,
additional precip chances, and a relief in temperatures.

Forecast concerns/challenges: High temperatures/heat indices
Thursday-Friday. Precip timing, coverage, and QPF.

Wednesday - Wednesday night: Heights continue to rise across the
northern Great Lakes, fueling the start of our return to warm
temperatures and increasing humidity levels as associated low-level
moisture advection ramps up. Surface high pressure gradually shifts
off to the east throughout the day, aided by a shortwave currently
visible on water vapor imagery over the Pacific NW, expected to move
through aforementioned ridging and into southern Ontario by midday
Weds. The last several guidance runs continue to show a weakening
trend to convection ongoing over western Upper/WI during the morning
hours, completely decaying before it arrives over northern Michigan
thanks to a lack of instability and a stubborn pocket of mid-level
dry air overhead. Will back off on PoPs for much of the day as
it certainly looks as if the majority of the day should remain dry.
Another complex/MCS is progged to move from WI toward Lake Michigan
during the late evening/early overnight, but will again struggle to
cross the lake into our area. Will bump PoPs down slightly Wed
night, but will hold off on removing completely until confidence
increases. Highs rising to near 80 across eastern Upper and along
the lakeshores with mid-80s the rule inland.

Thursday through Friday: Expansive ridging continues to strengthen
through the end of the work week. Northern Michigan sits on the
northeastern periphery of ridging, putting us as risk for additional
upstream MCS development to roll across portions of the area. While
large scale run-to-run variability continues to some degree, perhaps
the best chance for thunderstorm activity arrives late Thursday-Thu
night as an amplifying shortwave moves through southern Ontario as
upstream convection may dive southeastward into the area. To what
degree any complex holds together remains to be seen, but steepening
mid-level lapse rates promoting ample instability (MLCAPE of 2,000+
J/kg), deep layer moisture in place with sfc dew points near 70
degrees, a theta-e axis nosing into nrn MI, and a pocket of better
low-mid level forcing (although the best forcing lies north of the
international border), will all promote the threat for storms to
survive/develop late Thursday into Thu night. Deep layer shear
values of 35-45 kts over the entire area may promote a damaging wind
threat, which jives well with SPC`s Day 3 MRGL outlook for all of
nrn MI. Sfc high pressure noses in from the west late in the day
Friday, likely bringing an end (at least briefly) to any unsettled
weather across the area. Very warm temperatures expected Thursday
and Friday with highs ranging from the upper 80s to middle 90s. Heat
indices are expected to approach the middle 90s for many both Thu
and Fri afternoons. The only wrench we can throw into the
temperature forecast at this point would be any daytime convection
and or debris clouds sent across Lake Michigan from WI, which could
ultimately keep some areas from reaching their maximum heating
potential.

Dry and very warm/hot weather continues on the day Saturday as the
ridge is locked into the region. Sunday the pattern begins to
transition ahead of an 500mb trough that is ejecting from Manitoba
down into the Northern Plains. As a result a sfc low pushes into the
Great Lakes Sunday afternoon with cooler temperatures back to around
normal and increasing rain chances Sunday. The 500mb low stalls out
for the start of the work week with slight chance of an isolated
shower Monday and Tuesday.

Temperatures will cool down to the upper 70s and low 80s after
Saturday as the upper level low stalls out. This will keep our temps
near normal before temps heat back up next Wednesday. No severe
weather is expected for the time frame with our best chance at any
thunder is Sunday with the passing of the frontal boundary.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 100 AM EDT Wed Jul 20 2016

VFR conditions will persist at all Northern Lower Michigan TAF
sites through tonight as strong high pressure continues to slide
east away from Michigan. S/SW low level winds will begin to advect
warmer air into the region today...but wind speeds will remain AOB
10 kts thru tonight. There is a small chance of showers and
thunderstorms tonight...but the chance is too small to include in
the TAF for now.

&&

.MARINE...
Issued at 256 PM EDT Tue Jul 19 2016

With high pressure overhead...light winds
continue through tonight. Winds shift southerly for Wednesday and
Thursday although remain below Small Craft Advisory criteria.
Shower and thunderstorm chances arrive Wednesday afternoon as a warm
front approaches the region.

&&

.APX Watches/Warnings/Advisories...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...JZ
SHORT TERM...Farina
LONG TERM...Gillen/BPH
AVIATION...MLR
MARINE...Farina


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