Area Forecast Discussion
Issued by NWS Gaylord, MI

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536
FXUS63 KAPX 151949
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
349 PM EDT Sun Jul 15 2018

.NEAR TERM...(Through Tonight)
Issued at 347 PM EDT Sun Jul 15 2018

...More Stability, Less Boundaries...

High Impact Weather Potential...Thunderstorms, but less likely and
more like showers expected if anything.

Pattern Synopsis/Forecast... There is still a weak boundary over the
region. It has seemed to orient itself a bit differently over the
region. It looks more like a warm/stationary front within the sfc
high over the state, stretched northwest to the low in Manitoba.
However, a wave is forming on the front, and has a cold front
attached to it over the N Plains.

The cold front is expected to push through the Upper Great Lakes
later tonight, and through Monday. As the front moves through,
thunderstorms will be expected late overnight/early Monday morning.
In the meantime, with the somewhat drier conditions, than yesterday,
and the increasing tighter pressure gradient overnight (winds will
increase), will expect patchy fog over the region with most of it
near Saginaw Bay. There will be marine fog as well with the
dewpoints around the water temperature and the presence of the fog
already today going into tonight.

Primary Forecast Concerns...The concerns are minimal, but if there
were any it would be the enhanced reflectivity areas where the lake
breeze boundaries are colliding and possibly forcing some showers.
CAPEs this morning on the sounding, and in the forecasted soundings
were less than 100 J/kg through most of the day. The only time it
jumped was around 00z/Mon, but it was MUCAPE and it was elevated.
However, it doesn`t look like a kicker moves into the region to take
advantage of the elevated instability until after the instability
axis moves through. So showers are possible.

&&

.SHORT TERM...(Monday through Wednesday)
Issued at 347 PM EDT Sun Jul 15 2018

...Scattered showers/storms Monday, then dry and much cooler...

High Impact Weather Potential...Chance of thunderstorms on Monday,
especially across northern Lower, with a marginal risk of severe
storms near Saginaw Bay.

Pattern Synopsis/Forecast...A cold front will be pushing southeast
through the forecast area Monday morning, with a secondary cold
front hot on its heels later in the day. Cold air advection then
ramps up Monday night as a strong Canadian surface high settles over
the Upper Midwest by daybreak Tuesday...eventually sliding over
Michigan on Wednesday. A much drier airmass will accompany this
high, leading to a period of quiet, cooler weather.

Primary Forecast Concerns...Lingering shower/storm chances on
Monday.

A plume of more favorable moisture arriving late tonight will push
PWATs in excess of 1.5" out ahead of the front Monday morning. With
0-6km bulk shear vectors oriented neither parallel nor perpendicular
to the front, expect a broken line of showers and some thunderstorms
to develop along the boundary as it drifts southeast across northern
Lower. Likely not everyone will see rain from this system, and QPF
not looking all that impressive for those areas that do get some.
Guidance not really showing indications of an expansive, thick
mid/high cloud deck spilling off the convection that might otherwise
significantly limit destabilization. So think there may be a brief
window for respectable insolation to occur Monday morning over our
southeastern counties prior to frontal passage, likely pushing highs
into the mid 80s there. This would lead to moderate instability
(MLCAPEs upwards of 1500 J/kg) developing by early afternoon roughly
southeast of a line from Cadillac to Alpena, which would bode well
for the highest thunderstorm chances over our southeastern counties.
However, marginal deep layer shear along and ahead of the front (~30
knots or less) will generally hinder storm intensity/organization.
Another potential limiting factor would be if the front moves
through earlier or more quickly than expected, which would mean less
available instability. However, there is fairly good agreement among
CAMs for the initial front to move through our southeast in the late
morning-early afternoon timeframe. Wouldn`t rule out the possibility
for an isolated stronger storm or two down towards Saginaw Bay (see
SPC Day 2 marginal risk), but think greater severe threat will
reside more in southeast Lower. Favorable DCAPEs perhaps approaching
1000 J/kg suggest localized damaging winds would be the main threat,
though marginally severe hail may also be possible.

May see some additional isolated showers try to fire up along the
secondary front before it also exits our southeast in the early
evening. Thereafter, expect mostly clear skies through the rest of
the period and cooler than normal temperatures with highs in the 70s
both Tuesday and Wednesday. Tuesday will also be a tad breezy while
we reside out ahead of the strong surface high.

&&

.LONG TERM...(Wednesday night through Sunday)
Issued at 347 PM EDT Sun Jul 15 2018

High Impact Weather Potential...Thunderstorms possible at times
across northern Michigan Friday into next weekend, mainly during the
afternoon and early evening hours.

The surface high will begin to break down as it drifts east of the
area Wednesday night into Thursday. A pronounced shortwave trough
over the Upper Midwest is progged to morph into a cutoff low as it
drifts into the Great Lakes region on Friday. This feature will
remain overhead through next weekend, likely resulting a period of
unsettled, wet weather as it interacts with a moist airmass to
produce occasional showers and thunderstorms. Temperatures look to
warm back to near normal for the second half of the week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 222 PM EDT Sun Jul 15 2018

Fog has cleared out of the land areas. The main concern for the
afternoon is the low level moisture, heat, boundary collisions.
While today seems a bit less unstable, there is still a low chance
that showers could get going. Radar this afternoon, is showing
that some boundary collisions are beginning to become "enhanced"
at some locations along the Lake Huron lake breeze boundary. Main
threat comes Monday morning as a cold front moves through the
forecast area kicking off the thunder chances through the
afternoon.


&&

.MARINE...
Issued at 347 PM EDT Sun Jul 15 2018

Light winds and a trapped shallow layer of moisture have allowed
areas of dense fog to persist over portions of northern Lake
Michigan and central Lake Huron this afternoon. Have extended marine
dense fog advisories into tonight due to expectation of delayed
visibility improvement.

SW winds will pick up later tonight ahead of an approaching cold
front that will push through the region late tonight into Monday,
accompanied by a broken line of showers and embedded storms. Winds
will back to the WNW/NW behind the front on Monday, and in its wake
much cooler air and an increasing pressure gradient will lead to
somewhat gusty conditions for Monday night into Tuesday. Will
continue to monitor potential need for a small craft advisory in
some nearshore zones for that timeframe, but at this time conditions
look marginal.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...DENSE FOG ADVISORY until 11 PM EDT this evening for LHZ348-349.
     DENSE FOG ADVISORY until 5 AM EDT Monday for LHZ345.
LM...DENSE FOG ADVISORY until 5 AM EDT Monday for LMZ341-342-344>346.
LS...NONE.
&&

$$

NEAR TERM...JL
SHORT TERM...MK
LONG TERM...MK
AVIATION...JL
MARINE...MK



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