Area Forecast Discussion
Issued by NWS Gaylord, MI

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946
FXUS63 KAPX 241925
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
325 PM EDT SUN JUL 24 2016

.SHORT TERM...(This evening and overnight)
Issued at 322 PM EDT Sun Jul 24 2016

High impact weather potential: Lingering thunderstorm concerns
through this evening.

Pattern synopsis/expected evolution: One moist airmass across the
area this afternoon, with precipitable water values pushing 2 inches
and surface dewpoints around 70. This moist airmass is ahead of a
steadily east marching cold front which is now pushing into eastern
Wisconsin. Main complex of storms from earlier has slid by to our
south, with just a batch of lighter showers and thunderstorm riding
the M-55 corridor. Otherwise, all that low level moisture has
resulted in plenty of low clouds, with even some patchy mist and
drizzle across eastern upper and the tip of the mitt counties.

Front is expected to continue east, pushing across our area this
evening. Question is will enough instability be realized to allow
additional showers and thunderstorms to develop prior to its passing.

Primary forecast concerns/challenges: Shower and thunderstorm
evolution and intensity into this evening.

Details: Trends have definitely been downward with regards to
potential for additional shower and thunderstorm development later
this afternoon and evening. Problem is one of lack of instability
and very limited mid and upper level support. Some breaks in the
overcast starting to once again develop, although these are rather
short-lived as stcu quickly fills in through the development of
shallow instability. Latest SPC mesoscale analysis shows only 500
j/kg of ml cape nosing into northwest lower Michigan, with plenty of
cinh to overcome given warm off the deck thermal profiles.
Instability will have to increase substantially within the next few
hours to kick something off. Cannot completely rule it out given
ample moisture and those earlier mentioned breaks in the cloud
cover. Will continue to carry just chancy wording into this evening,
ending all threat overnight after frontal passage. If, and a BIG if
it is, instability can continue to climb, not entirely impossible
for an isolated severe storm or two to develop given modest deep
layer shear and hints of good cape through the hail growth zone.
Area remains in marginal risk...all conditional on development of
greater ml cape values.

As mentioned, threat for showers and storms ends later this evening.
Clouds will be slower to depart, although it does appear skies will
be clearing by morning. Sure not a lot of caa behind the front,
with lows by morning only dropping into the 60s.

.LONG TERM...(Monday through Sunday)
Issued at 322 PM EDT Sun Jul 24 2016

Monday through Wednesday...

(7/25)Monday...Sfc high pressure builds into the Upper Great Lakes,
with 500 mb heights building as well. This will keep the region dry,
with temperatures around the normal highs. Skies will clear out
during the day and remain that way through the night.

(7/26)Tuesday...The high pressure pressure remains over the region
through the day, keeping the region dry with light winds. The models
show that it may have some clouds moving in from Wisconsin late in
the afternoon, so it looks partly sunny by the afternoon. In the
evening, the GFS pushes rain into the N Lower, especially the
Straits area. NAM and ECMWF are fairly dry with the rain to the
west. Think that it will mainly stay dry, as the majority of the
models in the dry camp. So have chance pops along Lake Michigan for
now. Overnight, the impulse that is supposed to set off the rain
fizzles with the main impulse, well west with the sfc trough in the
Upper Mississippi Valley. So have slight chance pops in portions of
the forecast area.

(7/27)Wednesday...As the sfc trough approaches the Upper Great
Lakes, the thunderstorm potential will increase, however, it looks
like the main action will still be primarily in Wisconsin, closer to
the 500 mb shortwave trough, and the better moisture convergence.
ECMWf is on board with this scenario, with the sfc/850 mb moisture
maxes in N lower as this system moves into the region. With the 500
mb winds only 25 knots max, not anticipating much in the way of
severe weather. However, it does look like they could be slow movers
along the sfc trough. So will have to watch for possible heavy rain
issues as this gets closer in time.

JSL

Wednesday night through Sunday...

Temperatures will return closer to normal late in the week as we
start to see a pattern change. Height falls working into the Great
Lakes beginning around mid-week will continue to dig towards the
Tennessee Valley through the weekend, and ushering in the cooler
temperatures. This will also push the broad ridging that has been
setup across the southern CONUS to the west. Temperatures should
start to rise again as the weekend comes to a close, as the ridging
from the west folds into the Great Lakes, and the broad upper high
once again spans across much of the CONUS going into next week. With
a few shortwave disturbances moving through the flow, expect to see
some cloudiness and perhaps some scattered showers across the area
through the period, though large amounts of rain are not expected.
There could be a more substantial rainfall with the passage of a
more pronounced trough, but there is a great deal of uncertainty
with this feature, and amounts are still likely to be under a
quarter of an inch.

ALM

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 137 PM EDT Sun Jul 24 2016

Plethora of cig heights out there this afternoon, ranging from
mostly clear skies to mvfr causing stcu. This trend should
continue through the remainder of the afternoon. Confidence is
very low with regards to additional shower and thunderstorm
development later today into the evening as a cold front crosses
the taf sites. Will cover with vicinity wording for now. Of
course, any storms that do impact taf locations will temporarily
result in gust winds and lower cigs/vis. Band of mvfr clouds to
briefly follow this front tonight, with trends supporting rather
aggressive clearing towards morning. Mostly sunny and a touch
breezy heading through Monday morning.

&&

.MARINE...
Issued at 322 PM EDT Sun Jul 24 2016

Marginally gusty south winds to continue into this evening,
with winds veering more westerly and decreasing in speed overnight
as a cold front passes. May see a few showers and thunderstorms
later this afternoon and evening, with any that do form capable of
producing brief gusty winds. West to northwest winds pick up in
speed Monday, which may require additional sca`s on some nearshore
waters...particularly along the northeast lower coastline. Light
winds return Monday night, with light winds continuing through at
least the middle of the week.

&&

.APX Watches/Warnings/Advisories...
MI...NONE.
LH...NONE.
LM...SMALL CRAFT ADVISORY until 6 PM EDT this evening for LMZ342-
     344>346.

LS...SMALL CRAFT ADVISORY until 6 PM EDT this evening for LSZ321.

&&

$$

SHORT TERM...MSB
LONG TERM...JSL/Mayhew
AVIATION...MSB
MARINE...MSB



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