Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 201527

Area Forecast Discussion
National Weather Service Gaylord MI
1127 AM EDT Tue Aug 20 2019

Issued at 1127 AM EDT Tue Aug 20 2019

High clouds from the blow off of the ongoing MCSs south and west
of the forecast area. This is affecting the warm front that looks
to be struggling to move north as thought earlier. If the high
clouds (mainly south of M-72) can thin out and allow more sun,
then the warm front may move into the region. The more northerly
MCS has light rain showers streaming off its northern periphery
and heading our way. The NMM and ARW seem to be handling this
reasonably well, but a tad slow. The ideas is that the showers
break out along the warm front and move into the region east of
I-75 and south of M-72. This would be between 18z and 21z this
afternoon. HRRR agrees with this general idea as well. So will try
some blending of the pops. So the expectation is that isolated
showers will occur with the scattered rain being one outcome and
nothing being the other outcome.


.NEAR TERM...(Today through Tonight)
Issued at 433 AM EDT Tue Aug 20 2019

...Rain chances minimal through tonight...

High Impact Weather Potential: Minimal.

Pattern Synopsis/Forecast: Midnight surface/composite analysis shows
a wavy stationary frontal boundary (the cold front that crossed
northern MI last night) lying across the lower Great Lakes/southern
Lower MI/northern IL/far northeast MO.  Boundary delineating a
moisture gradient with dew points above 20C south of the front...0-
1km mean mixing ratios greater than 15g/kg stretches from IL/MO and
into the central Plains as far north as eastern SD.  00z APX
sounding was dry in both a relative and absolute sense...with dew
point depressions at or above 10C below 300mb...and a precipitable
water of 0.68 inch (compared to 1.25 inch at DTX).  Dry air and
general large scale subsidence contributing to mainly clear skies
across northern MI early this morning...some convection has been
developing near and south of the front across the Ohio
well as across parts of the Dakotas/southwest MN/northwest IA within
strong low level theta-e gradient/advection and aided by a short
wave trough evident in water vapor imagery.  Generally zonal flow
across the upper Midwest/Great Lakes region.

Stationary boundary over southern Lower early this morning is
expected to gradually lift north during the day...not much of a wind
shift along it but certainly a low level moisture/theta-e gradient
that gets up toward US-10 by this evening.  Meanwhile...zonal flow
will begin to amplify a bit with resulting height falls into the
upper Midwest/Great Lakes tonight.  A weak lead impulse will cross
the forecast area tonight...along with a surface cold front that
will probably lie across northern Lower by Wednesday morning.

Primary Forecast Concerns: Precipitation potential with encroaching
front from the south this afternoon and approaching cold front from
the northwest tonight.  For today...not much potential through at
least mid afternoon with scattered activity across southern Lower
along boundary and developing buoyancy gradient aided by weak short
wave trough passage.  Northern edge of instability gradient pushes
toward the M-55 corridor by evening.  Some question as to what
surface dew points will do this afternoon across northern Lower...
evolution of very dry layer between 850-700mb on 00z GRB sounding
may be a player as that advects across the region on westerly flow.
Dew points will likely sink into the 40s if mixed layer can tap into
that (which isn`t unreasonable)...RAP is really dry with some upper
30s across far northeast Lower.  But think dew points in the 40s are
not unreasonable...with more humid air getting into southern
portions of the forecast area by late afternoon.  Can`t rule out
some showers in the Saginaw Bay vicinity where capping will be
weakest...possibly aided by lake breezes though mixed layer likely
to be fairly deep so uncertain whether lake breeze circulation can
shove a parcel up to the LFC (which may be above 800mb).

Another weak short wave trough expected to slide across the forecast
area this evening...still not sure forcing will be enough to
generate showers except near Saginaw Bay.  Could end up being that
best chance for precipitation will be along the cold front after
midnight with a decent signal for low clouds/drizzle across eastern
Upper/northwest Lower.  Bottom line is that precipitation chances


.SHORT TERM...(Wednesday through Thursday)
Issued at 433 AM EDT Tue Aug 20 2019

High impact weather potential: None

Pattern synopsis and forecast:

A weak cold front associated with a low pressure system over the
James Bay region will sweep into the forecast area late Tuesday
night into Wednesday. This slow moving boundary may trigger some
more showers Wednesday afternoon, mainly closer to the Saginaw Bay
region where diurnal heating and possible lake breezes may aid in
the development. Although some high pressure builds back into the
region later Wednesday, wouldn`t be surprised if the upper level
troughing and available moisture produce more cloud cover than is
forecast at this time. Winds will become southwesterly ahead of the
aforementioned cold front Tuesday afternoon and veer to the
northwest behind the front Wednesday and Thursday. With the CAA...
winds could become gusty Wednesday afternoon, especially over the
lakes and eastern upper. Winds will become lighter late Thursday and
begin to veer more northerly by Friday morning. Temperatures will be
cooler Wednesday once again with the CAA behind the said boundary,
reaching into the low to mid 70s for most locations...closer to
Saginaw Bay may see low 80s. As colder air continues to filter in on
northwesterly flow, some locations may only reach into the mid 60s
Thursday, while temperatures will moderate a bit thereafter,
reaching into the low to mid 70s once again on Friday.

.LONG TERM...(Thursday night through Monday)
Issued at 433 AM EDT Tue Aug 20 2019

High Impact Weather...None is expected.

The long term models are in agreement with this period mostly being
under surface high pressure with the exception of yet another weak
cold front and attendant upper level wave dropping down from central
Canada during the late weekend/Monday timeframe. This will most
likely be the only precipitation chances during this forecast
period. Temperatures will moderate a bit each day, beginning in the
mid to upper 70s Saturday and reaching near 80 through the remainder


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 433 AM EDT Tue Aug 20 2019

Fog formed at MBL beginning at 03Z. Expect IFR fog development
overnight at APN/PLN as well. Fog will quickly burn off in the
morning, with VFR conditions after that. Increasing mid clouds on
Tuesday, maybe a stray shower or two in the evening.

Light winds, with onshore lake breezes Tuesday afternoon.


Issued at 433 AM EDT Tue Aug 20 2019

Marine winds will be dominated again by local effects today as
overall pressure gradient not particularly strong.  Cold front will
cross the nearshore zones tonight...which will shift winds to
north/northwest Wednesday morning.  Cold advection/mixing will allow
for gusty winds in marine areas Wednesday...possible for a round of
Small Craft Advisories later Wednesday afternoon/night.




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