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000
FXUS63 KAPX 231738
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
138 PM EDT Fri Jul 23 2021

.NEAR TERM...(Today through Tonight)
Issued at 319 AM EDT Fri Jul 23 2021

Impactful weather: Chances for showers and thunderstorms. Severe
storms not expected.

Pattern synopsis and forecast:

Upper level troughing was over the NE conus and in western Canada/NW
conus early this morning, with ridging from the SW conus through the
upper Midwest and central Canada. At the sfc, low pressure was in
nrn Alberta/Saskatchewan, with a warm front extending SE through
ND/MN/srn Lake Michigan. While the stronger forcing from DPVA and
upper jet divergence were well off to the north and west, there was
broad theta-e convergence along and north of the warm front,
resulting from weakish LLJ activity tapping deeper atmospheric
moisture (PWATs greater than 1.75"). This was resulting in in some
spotty showers and thunderstorms from the upper midwest and into the
western Great Lakes. Some of this activity was trying to get going
in nrn Michigan.

The mid level ridge moves in today, before pushing eastward tonight,
making way for the upstream troughing to carve into upper midwest
and western Great Lakes. This will gradually allow the warm front to
lift into nrn Michigan by Saturday morning, while DPVA and upper jet
divergence increases with the shortwave trough. There will be
several chances for convection over this time, especially late
tonight. Elevated convection will continue to pester nrn Michigan
into this morning, before the activity becomes more diurnally driven
this afternoon, and focused on lake breeze convergence zones. Fcst
soundings show no capping in place, so feel decently in seeing
convective action today. This will mainly be in nrn lower, closer to
deeper moisture and best instability of several hundred j/kg, to
greater than 1000j/kg across portions of NW lower Michigan.
Convective coverage will dwindle through this evening with loss of
heating and lake breezes, before chances ramp up late tonight in the
strengthening forcing/dynamics ahead of the wave. MUCAPES are likely
to remain below 1000j/kg late tonight. Effective bulk shear isn`t
overly impressive, but does increase tonight, but even when coupled
with the aforementioned instability, severe storms are not expected.

High temperatures will largely be in the lower half of the 80s, with
lows tonight largely in the mid to upper 60s.

&&

.SHORT TERM...(Saturday through Sunday)
Issued at 257 AM EDT Fri Jul 23 2021

...Thunderstorms Today and Saturday...

High Impact Weather Potential...Possible severe weather/heavy rain
Saturday.

Isolated severe weather possible Saturday morning. Upper ridge
remains over the west with westerlies across SW Canada and across
the Great Lakes. Leftover convection/remnants of MCS drop across the
area Saturday morning. Could be some isolated hail/damaging tstorms
winds as is normal with MCS remnants. PWAT values approach 2" over
the area showing the extent of high moisture over the region. Brief
heavy rain will also be a possibility.

Severe weather is possible Saturday afternoon/evening. A cold front
moves through Saturday night/Sunday morning. Ahead of the front very
moist air (~70F Td) and daytime peak heating will combine to bring
high CAPE values (2000+J/kg) and instability. 35kt 850mb jet
approaches from the Midwest providing convergence and descent low
level shear (bulk shear 40kts) while general diffluence in the upper
levels will enhance lift for the possibility of severe weather.
Afternoon lake breezes could trigger some better thunderstorms.
However best chance for severe weather seems to be just south of the
area more in line with the nose of the 850mb jet. SPC has a marginal
(5%) risk northwest and slight (15%) risk southeast.

.LONG TERM...(Sunday night through Thursday)
Issued at 257 AM EDT Fri Jul 23 2021

Upper ridge shifts slowly east through the period. Great Lakes
remain in warmer and higher humidity air. Warmest temperatures
occur Sunday and Monday. Frontal system moves in midweek with off
and on shower/tstorm chances.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1259 PM EDT Fri Jul 23 2021

Main concern in the next 12 hours will be the shower activity, and
whether the CIGs will lift to MVFR/VFR. CIGS near MBL have been in
and out of IFR most of the morning, with some IFR CIGs upstream in
Wisconsin. This may continue, although as temperature warm,
lifting CIGS are expected. The rain, based on the radar trends,
is expected to diminish a bit, before the next round of rain
restarts a little more inland, and moves east.

For the next second 12 hours of the TAFs (06z-18z/Sat) the main
concern is the thunderstorms and resulting CIGs and VSBYs.
Computer models have the thunderstorms moving in from the UP and
affecting TVC and PLN between 09z and 12z/Sat with IFR CIGs, and
possibly some MVFR VSBYs as the fog may begin to restrict VSBYs
with the rain. MBL and APN would be affected by the line sometime
between 10z and 13z with the same issue.

The rain is expected to continue through the morning with MVFR
Vsbys, and IFR to MVFR CIGs through 18z, before clearing.


&&

.MARINE...
Issued at 319 AM EDT Fri Jul 23 2021

A warm front will gradually spread into nrn Michigan today into
tonight, before a cold front crosses Saturday and Saturday evening.
This will bring chances for showers and thunderstorms, with the
greatest chances late tonight and Saturday, with chances for severe
storms Saturday. The pressure gradient tightens up tonight into
Saturday, with the potential for low end advisory wind speeds out of
the S/SE tonight, turning more westerly through Saturday. Will not
issue any advisories attm.


&&

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

$$

NEAR TERM...SMD
SHORT TERM...KF
LONG TERM...KF
AVIATION...JL
MARINE...SMD