Area Forecast Discussion
Issued by NWS Gaylord, MI

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277
FXUS63 KAPX 251935
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
335 PM EDT WED MAY 25 2016

.SHORT TERM...(This evening and overnight)
Issued at 333 PM EDT Wed May 25 2016

High impact weather potential: Nothing too significant. Perhaps some
brief heavy rains and small hail within non-severe thunderstorms
this afternoon through Thursday.

Pattern synopsis/expected evolution: Warm and increasingly muggy
pattern found across the northern lakes this afternoon as upper
level ridge axis continues to dominate. Combination of increasing
moisture and those warm temperatures kicking off some scattered
showers and thunderstorms this afternoon, making it look and feel
even more like mid-summer. Southwest flow developing down through
the column, with the surface winds the last to respond as quasi-
stationary warm front has set up just to our south. Surface features
will eventually respond to stronger mid and upper level flow regime,
eventually bowing that warm front north into our area by morning.
This front will attempt to mix further north Thursday, but per the
usual, cold lake waters will largely dictate how far north it
eventually makes it. Vicinity of this front and passage of mid level
support will bring additional chances for some much needed rain in
the coming days.

Primary forecast concerns/challenges: Addressing shower and
thunderstorm chances through the period.

Details: Diurnally driven scattered showers and thunderstorms will
will continue to propagate across the northern lower landscape the
remainder of this afternoon and early evening. "Greatest coverage
expected to be south of M-68 and across interior areas where
convergence will be focused via terrain influences and lake breeze
fronts. Not expecting any severe weather given weak wind fields and
marginal instability, but slow propagation could result in some
locally heavy rains, and suppose some very small hail is possible.
Attention this evening and overnight turns to respectable surge of
theta-e advection in strengthening southwest flow regime (enhanced
by passing mid level wave). Broken band of showers should accompany
such, although honestly not very confident on exact timing and
coverage. Decent band of elevated instability, with upwards of 1k
j/kg 0-6km most unstable cape punching into southwest zones
overnight. So, thunder is certainly possible, but given depletion of
surface based instability and only marginal deep layer shear, feel
thunderstorm intensity should remain well below severe limits.

A rather soupy airmass (ok...by northern Michigan standards) spreads
across the area as that warm front slowly mixes north, with
dewpoints pushing the lower 60s. Not much of a deep trigger around,
with the front itself largely devoid of any mid level support.
Still, given progged ml cape development in excess of 1k joules/kg
(think NAM-WRF`s 2k+ is simply too high, as is its mid and upper 60
degree dewpoints), some convection should fire along the front and
any lake/elevation driven convergence maxima. No big severe threat,
although given better instability, any very well organized updraft
may support some brief larger hail.

.LONG TERM...(Thursday through Wednesday)
Issued at 333 PM EDT Wed May 25 2016

Thursday night through Saturday...

Pattern synopsis/Expected evolution: Upper level ridging evident
across the middle of the country this afternoon will gradually push
east through the end of the work week leaving northern Michigan on
the eastern periphery of long wave troughing expected to settle into
the western two-thirds of the CONUS. Several shortwaves of interest
visible on water vapor imagery/upper level analysis with the first
arriving tonight into Thursday morning with several additional
pieces of energy expected to continue off-and-on precip chances
through the upcoming holiday weekend.

Forecast challenges:  PoPs/QPF/precip timing Friday through
Saturday.

Details: A fairly active period expected overall; however, little in
the way of concern at the start of the period (Thursday night) as it
stands now due to a pocket of low-mid level dry air expected to
rotate through the upper Great Lakes. However, more active
conditions are expected to arrive during the day Friday as one of
several shortwaves rotating in from the southwest is expected to
arrive during the late morning-early afternoon hours. Will gradually
increase PoPs/thunder chances from southwest to northeast during the
day Friday, becoming likely (but still in a scattered fashion) late
morning through the remainder of the afternoon hours. Severe weather
parameters look fairly anemic as a whole Friday-Friday night.
Despite 700-1500 J/kg of 0-1 km MLCAPE, bulk shear values under 30
kts will certainly inhibit any long-lived updrafts and limit the
overall severe threat. PWs surge upwards of 1.25-1.50+ inches
providing a heavy rain threat within any thunderstorms.

Precip chances continue Friday night into the day Saturday, both
synoptically driven from another shortwave or two rotating through
the Great Lakes and diurnally driven during the day Saturday. Once
again, just a very limited severe threat, but certainly the heavy
rain threat will continue in any scattered thunderstorms with
similar PWs as Friday, approaching 1.50 inches.

Above normal temperatures are expected to continue through the
period, ranging from the low-middle 70s along the immediate
lakeshores to the middle 80s in downloping locations of northeast
Lower. Unseasonably mild overnight lows are expected with temps 10-
15 degrees above normal, ranging from the upper 50s north to
middle 60s near Saginaw Bay.

Gillen

Extended (Sunday through Wednesday)...

The upper level trough will gradually dampen (fill in) through the
extended forecast period leaving a nearly zonal flow aloft. However,
there will be yet another upper level disturbance that will bring a
decent shot of showers and thunderstorms Sunday. There could be some
diurnally driven convection that pops during mainly Memorial Day
afternoon  (low chance pops). Only a slight chance for more activity
Tuesday followed by chance pops again next Wednesday with perhaps
another upper level disturbance. So overall, a little active but
nothing widespread or prolonged is expected. Humidity/dewpoints
slowly decreases through the period. It will remain very warm to
start the period then temperatures should settle back toward
climatology numbers for early June by the middle of next week.

Sullivan

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 131 PM EDT Wed May 25 2016

Patch of stratus continues to impact KPLN, and looks to do so for
a few more hours. Otherwise, just some cirrus and high based cu
across northern Michigan. These cu will continue to develop, with
isolated/scattered showers and thunderstorms expected this
afternoon. Not convinced these will impact the taf sites, with
most coverage expected across the interior. Band of more organized
showers spreads overhead tonight, although cigs look to be
relatively high based. Will need to monitor for some isolated
heavy rain producing storms, which could cause brief restrictions
at the airports. Another round of stratus and mist late tonight
and early Thursday morning, although once again not completely
sold on how widespread it will be. Some improvement expected
Thursday morning as warming helps raise cigs. Light winds through
the forecast.


&&

.MARINE...
Issued at 333 PM EDT Wed May 25 2016

Rather light winds to continue for the foreseeable future
and stability remains high in an unseasonably warm airmass. Those
same conditions will continue to result in areas of fog, which at
times could be locally dense. Periods of showers and thunderstorms
the next several days, any of which could produce brief gusty winds.

&&

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

$$

SHORT TERM...MSB
LONG TERM...Gillen/Sullivan
AVIATION...MSB
MARINE...MSB



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