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FXUS63 KAPX 060359
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1159 PM EDT Fri Jun 5 2020

.UPDATE...
Issued at 931 PM EDT Fri Jun 5 2020

Broad upper level cyclonic flow combined with lingering lake
breeze boundaries and residual synoptic moisture have resulted in
the development of a few showers and isold thunderstorms across
western Mackinac county and far Northern Lake Michigan late this
evening. Have noted a general downward trend over the past few
frames as the sunset sets and daytime instability wanes. Expect
this trend will continue over the next hour or so...with all
shower/storm activity coming to an end by midnight. Expect a
mostly clear...cool and calm rest of our night...providing plenty
of great full moon viewing. Eastern Upper Michigan will see some
increasing clouds toward daybreak as a secondary cold front drops
into the far Northern Great Lakes.

&&

.NEAR TERM...(Through Saturday)
Issued at 153 PM EDT Fri Jun 5 2020

...Cool Start to the Weekend...

High impact weather potential: Minimal. Perhaps a few thunderstorms
yet this afternoon.

Pattern synopsis/forecast:

Mid level impulse in broader zonal flow regime racing east across
the northern Great Lakes this afternoon. As is typical in the warm
season, surface response not nearly as robust as the mid level
parent, with weak surface low sliding by north of Lake Superior and
its attendant surface trough/weak cold front working its way across
our area. Ragged band of showers along this front into northern
Michigan, producing just minimal rainfall amounts.

Current shortwave trough will exit steadily stage right tonight into
Saturday morning, taking rain chances along with it. Mid and upper
level flow regime undergoes quite the amplification process this
weekend, driven in large part by strong shortwave and dual upper
level jet cores punching into western NOAM. This, in turn, forces
steady height rises into the Northern Plains and southern Prairie
lands of Canada...establishing dry and seasonably cool northwest
flow into the Great Lakes along its downstream flank.

Primary forecast concerns/challenges: Lingering shower and
thunderstorm chances this afternoon. Cloud and temperature trends
through Saturday.

Details:

Initial concern centers on the potential for thunderstorms to
develop the remainder of this afternoon, especially down near
Saginaw Bay where warming has been maximized. SPC mesoanalysis shows
mixed layer cape slowly increasing across that area. Enhanced
convergence along front and lake breeze driven convergence axes
supports the potential for thunderstorm development. Not expecting
anything severe, but definitely wouldn't rule out some small hail
and brief gusty winds...as well as some locally heavy rainfall.
Otherwise, exit of front this evening will end the shower threat.
Not overly confident with regards to cloud trends tonight with at
least some hint low level moisture rotating southeast out of Canada
will bring some lower clouds along with it...especially across
eastern upper Michigan.

Any lower clouds Saturday morning expected to morph into a scattered
shallow cu field as low level mixing increases. Pressure gradient
will gradually tighten as high pressure works its way southeast out
of Canada...resulting in somewhat gusty northwest winds. These winds
will usher in a drier and cooler airmass, with highs struggling
through the mid and upper 60s across eastern upper and northwest
lower Michigan. Tad warmer conditions expected across northeast
lower where downsloping will help the cause.

&&

.SHORT TERM...(Saturday night through Monday)
Issued at 218 PM EDT Fri Jun 5 2020

High Impact Weather Potential: Low...Widely scattered showers
possible across eastern upper Monday.

Pattern Synopsis:

A vigorous shortwave will quickly move north and eject over the
northern Great Plains Saturday night as the associated longwave
longwave trough pivots into the Rocky Mountain West through Monday.
This shortwave will amplify the ridging across the Midwest and Great
Lakes into early next week. At the surface, a seasonably strong
cyclone looks to develop underneath favorable divergence aloft
provided by the aforementioned shortwave. This cyclone is expected
to move north into Saskatchewan as high pressure centered over
Hudson Bay continues to build down into the Great Lakes through
Monday. Additionally, a second cyclone looks to develop in the lee
of the Rockies in the central Great Plains towards the end of the
period as what is currently forecast to be Tropical Storm Cristobal
begins to move inland along the Mississippi River Valley.

Forecast/Details:

A very pleasant end to the weekend appears to be ahead. Highs in the
low 70s are expected on Sunday with light easterly surface winds.
Winds will continue to veer going into Monday, resulting in S/SW low-
level winds advecting warm, moist air back into the region. Partly
to mostly sunny skies are still expected on Monday, which will aid
temperatures reaching into the low to mid 80s across northern lower.
These temps would be around 10 degrees warmer than seasonal
averages. There is a chance for scattered showers to move into
eastern upper Sunday night into Monday morning as a subtle embedded
speed max in the main flow moves overhead. However, precipitation
may struggle to reach the ground as the low level airmass across
that area looks to be fairly dry. Additionally, confidence is low in
thunder chances with this precipitation.

.LONG TERM...(Monday night through Friday)
Issued at 218 PM EDT Fri Jun 5 2020

High Impact Weather Potential: Extratropical remnants of Cristobal

A complex, challenging forecast is in store for the middle of next
week as Cristobal is expected to undergo extratropical transition
and move northward along the Mississippi Valley towards the Great
Lakes. It is important to emphasize that specific impacts are still
highly uncertain and hinge greatly on the timing of Cristobal moving
onshore and the progression of a seasonably impressive longwave
trough that is expected to be positioned over the Rocky Mountain
West at the start of the period. The current forecast from the
National Hurricane Center has Cristobal making landfall along the
Gulf Coast Sunday night and moving into the mid-Mississippi Valley
region in the Monday night/Tuesday morning timeframe. Current
confidence lies in the track generally following the Mississippi
River northward into the northern Great Lakes. Recent guidance
suggests that after Cristobal moves inland and gets picked up by the
trough that impressive dynamic forcing aloft would eventually
further deepen the cyclone as it moves northward.

A few main uncertainties present themselves with the current
guidance solutions. The first is that this would an exceedingly rare
event all things considered. Second, confidence wavers in the how
well model guidance handles what would be a large influx of latent
heating into the existing ridge across the central CONUS. Guidance
may be under-representing this, and this would in turn work to
further amplify the ridge and hinder the forward progression of the
trough across the CONUS. Lastly, this would result in greatly
differing potential impacts across the area as the timing of key
systems interacting would be shifted. Regardless, the possibility of
a strong system impacting northern Michigan the middle of next week
is being closely monitored with many uncertainties at hand. The main
concerns would be very strong wind gusts and heavy rain, but both of
these are far from certain at this time. Confidence will increase as
next week nears. Additionally, the other focus next week will be
high temperatures on Tuesday. Strong warm advection is expected to
continue, resulting in highs possibly reaching 90 and above during
the afternoon.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1158 PM EDT Fri Jun 5 2020

Cooler and drier air will continue to move into the Western Great
Lakes region thru Saturday. Solid VFR conditions are expected at all
Northern Lower Michigan TAF sites over the next 24 hours.
Light/variable winds overnight will become N/NW at 10 to 20 kts on
Saturday.

&&

.MARINE...
Issued at 153 PM EDT Fri Jun 5 2020

A few showers this afternoon gives way to the return of dry weather
tonight into this weekend. Light winds expected through this evening
as weak pressure gradient remains. This gradient begins to tighten
late tonight into Saturday, and winds will be more solid out of the
northwest. Gonna keep speeds under advisory levels due to overlake
stability, but there could some some isolated gusts to impact small
crafts. Speeds weaken a bit into Saturday night, as higher pressure
sneaks into the region.


&&

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

$$

UPDATE...MR
NEAR TERM...MB
SHORT TERM...DJC
LONG TERM...DJC
AVIATION...MR
MARINE...MB
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