Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 221510
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1110 AM EDT Thu Jun 22 2017

.UPDATE...
Issued at 1029 AM EDT Thu Jun 22 2017

The departure of a shortwave and it`s forcing through nrn Lake
Huron, has brought an end to the first wave of showers and storms.
We had a plethora of forcing, highlighted by LLJ warm/moist
advection ahead of a warm front just off to our SW and upper
divergence under 110+kt jet to our north. The air mass is already
quite moist with PWATS around 1.5", but will get even more
saturated as the warm front blows through today, ushering in near
2" PWAT air. Tough to discern, but latest RUC anaylsis showing
several weak perturbations in the fast westerly flow aloft. In
such a moist air mass, the next several hours or most of the
afternoon is certainly a non-zero chance for seeing additional
showers/storm potential. Not much of a focus/feature to attach
decent chances to however, and likely only seeing a few rogue type
showers. This will be until an upstream cold front nears the
western CWA by later this afternoon and especially this evening.
Gotta still love the ongoing forecast of widespread activity
developing during the evening, when the next shortwave/upper
divergence/LLJ arrive. Trends have supported a farther south
expectation for potentially heavy rainfall, more from the GTV Bay
region to Alpena, and areas south of there, where amounts
exceeding an inch is possibly in many areas. Still have a small
chance for a few storms to maybe become severe, closer to the M-55
corridor, with damaging winds and large hail being the threats.
However, locally heavy rainfall seems like a better chance at this
point, but convection can be finicky, so we`ll see.

&&

.NEAR TERM...(Today through Tonight)
Issued at 237 AM EDT Thu Jun 22 2017

...Periods of showers and thunderstorms...some possibly heavy...

High impact weather potential...Heavy rain concerns through tonight.
Some severe thunderstorms possible.

Pattern synopsis/forecast...Weather becoming more active across the
region, initially made so by robust low level jet developing to our
west. Impressive surge of deep layer moisture advection tied to this
jet axis, and when coupled with forced ascent through jet nose
convergence within a steepening instability gradient, is resulting
in a developing area of showers and thunderstorms across the western
Lakes at this early hour. Developing warm front also coming into
play is it begins northeast pivot into central Wisconsin. Further
upstream, organizing cold front making its way across Minnesota,
with a bands of showers associated with it.

Plenty coming into play to drive some decent rains into our region,
with the first round expected early this morning, likely followed by
additional development later today and tonight. Impressive moisture
advection and veering of that low level jet will drive this mornings
activity, with some of the storms perhaps becoming intense as that
same jet ramps up deep layer shear within increasing elevated
instability gradient. Additional development today and tonight will
be tied to that passing warm front, followed by a slow moving cold
front crossing the region tonight. Deep moisture plume (precipitable
water values in excess of 1.75 inches) and persistent mid level jet
core atop these surface features sure supports some heavy rain
potential, along with isolated severe thunderstorm concerns.

Primary forecast concerns/challenges...Addressing that heavy rain
concern and severe thunderstorm potential.

Details...Per the usual with convection, it is a high
uncertainty/low confidence type of forecast. Still expecting
blossoming area of showers and thunderstorms to move across the
region early this morning, tied to that veering and gradually
weakening low level jet. Only a small area near Manistee remains
clipped by latest SPC Day One marginal risk, with that hinging on
possible development of convective line segments and attendant gusty
wind potential. Forecast after this intial passing area of showers
remains a very formidable challenge. Cold front slowly settles south
into far northern lower Michigan by evening, with a very moisture
rich environment out ahead of it. However, that moisture may result
in quite a bit of cloud cover, which could significantly hamper
boundary layer cape development. Most guidance remains steadfast in
developing additional activity this afternoon along and ahead of the
front. Those same guidance progs really ramp up mean layer cape
which, as mentioned, might be overdone given the expected cloud
cover. Simple amount of moisture and increasing surface based
convergence supports at least some additional shower and
thunderstorm potential. Deep layer flow becoming increasingly
aligned with the surface boundary definitely supports some heavy
rain concerns, as does those pwat values and an increasingly deep
warm cloud layer. This trend continues into tonight with passing mid
level support, attendant weak low pressure riding northeast along
the front, and an increasingly defined cape gradient only adding to
the heavy rain potential. Now, where the primary axis of heavier
showers align remains much in doubt, with congealing convective
driven cold pools perhaps reinforcing the actual surface front and
forcing a more southward displaced area of max surface convergence
with time. Latest WPC excessive rain outlook has pretty much all of
northern lower Michigan under a slight risk. Hard to argue with this
idea for now, with the potential definitely there to see isolated
amounts in excess of 2 inches by morning. Don`t think areal coverage
of heaviest rains is enough to justify any type of flood watch, but
will continue to highlight this concern in all our hazardous weather
products.

Second order of business is addressing severe weather potential.
Marginal risk extends a touch further north with latest SPC update,
running roughly along and south of M-72, with a slight risk now
clipping far southern areas from Manistee to Gladwin again just
clips the far southern part of our area. Given wind fields and
potential for high intensity precip loading cores, any significant
mean layer cape development will definitely support some severe
weather concerns. Really just a wait and see approach for now.

&&

.SHORT TERM...(Friday through Saturday)
Issued at 237 AM EDT Thu Jun 22 2017

...Turning cooler...

High impact weather potential...None expected.

Any lingering showers and storms from Thursday night`s system should
head off to our east Friday morning. However, a few instability
driven showers may make a return during the afternoon, especially
across eastern upper and northeast lower. Friday night looks
precipitation free then energy moving through the long wave trough
aloft (which will be in place for a few days) could spawn more
showers Saturday, especially in the afternoon. Thunder is also
possible especially across northeast lower. Winds aloft are fairly
light so the main threat (if any) would be for some small hail with
low freezing levels (under 8,000 feet and wet bulb zero heights only
about 7,000 feet). Not as warm Friday then noticeably cooler
Saturday.

.LONG TERM...(Saturday night through Wednesday)
Issued at 237 AM EDT Thu Jun 22 2017

Long wave troughing continues across the Great Lakes region into
early next week. Just about when this trough begins to relent and
move off to our east another one looks like it comes in behind it
for the middle of next week. This means more chances for showers and
thunderstorms, especially in the afternoons. Temperatures should
remain below average for late June through early next week before
moderating toward the end of the period.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 711 AM EDT Thu Jun 22 2017

Challenging aviation forcast through this period. Band of low
level jet driven showers will spread across and out of our area
through this morning. Brief periods of restrictions expected with
any heavier showers and thunderstorms. May see some low clouds
build in for a time behind this lead rain, especially at KPLN.
Shower and thunderstorm threat returns later this afternoon, and
especially this evening, as a slow moving cold front drops through
the region. Any storms during this period will be capable of
producing very heavy rain and gusty winds. MVFR/IFR conditions
with these heavier showers. Low clouds likely to build south
across the taf locations as primary axis of rain pivots off to the
east later tonight.


&&

.MARINE...
Issued at 237 AM EDT Thu Jun 22 2017

Winds veer to south and become a bit gusty this morning,
with southwest winds slowly decreasing in speed this afternoon. May
see some brief small craft advisory wind gusts for a time this
morning. Light winds expected tonight, increasing in speed a bit on
Friday as they become west. Bigger story will be increasing
thunderstorm potential this morning, with the threat for additional
thunderstorms again this afternoon and overnight. Any thunderstorms
will be capable of producing brief gusty winds and very heavy
rainfall.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...SMD
NEAR TERM...MSB
SHORT TERM...AJS
LONG TERM...AJS
AVIATION...MSB
MARINE...MSB



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