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000
FXUS63 KAPX 231919
AFDAPX

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

.NEAR TERM...(Through Tonight)
Issued at 317 PM EDT Fri Jul 23 2021

...Showers and Thunderstorms...

High Impact Weather Potential...Thunderstorms, Possibly severe,
but more likely after 12z Saturday.

Pattern Synopsis/Forecast...A warm front, along the 500 mb jet, has
been kicking off showers, and a little thunder over the SW counties
this morning, and afternoon. Most of the action has been south of
MBL, with rain showers around FKS to CAD, and MBL. CAMs have been
showing that the axis of instability and the precipitation should
move into the rest of the state later this afternoon/evening before
we lose the heat of the day after 00z/Sat. However, the models have
really been keying on the activity that should develop NW of the
region along the cold front that will move out of Minnesota tonight
and into the UP. The initial line looks to affect E Upper between
06z and 09z, then locations north of a line front TVC to APN,
between 09z and 12z, then the rest of the forecast area by 12z or a
little after.
&&

.SHORT TERM...(Saturday through Monday)
Issued at 317 PM EDT Fri Jul 23 2021

...Storm chances continue over northern Michigan...

High impact weather potential: Severe storms possible Saturday, with
damaging winds being the primary threat...large hail to a lesser
extent, but still possible. An isolated tornado is also not out of
the realm of possibilities.

The forecast period begins with a north to south oriented warm front
associated with a low pressure system to the west of Hudson Bay
draped through northern Michigan. The southwesterly flow behind the
aforementioned warm front will advect warm and very humid air into
the forecast area with dewpoints near and possibly above 70 degrees
with PWATs progged to be between 1.75" and 2.00". The main threat
area for severe storms Saturday should be northeast
lower...especially closer to the Saginaw Bay area. This will be
where the best synoptic forcing will be located with the warm front,
shortwave trough, and diurnal heating all helping to boost
instability. Forecast soundings show around 1000 J/kg MLCAPE, 600-
700 J/kg DCAPE, and around 50 kts at 850 mb. Wind will be the
primary threat in any severe storm that does develop during the
early part of the day as there is not much shear to have a more
"organized" supercell develop to produce large hail...especially in
such a warm airmass. Stronger storms could also develop behind the
warm front during the day Saturday with another severe threat, with
some 0-6km bulk shear of around 40 kts, some drying in the mid-
levels, and MUCAPE of 2000+ J/kg...these could produce some severe
storms that produce large hail and isolated tornados along with the
earlier threat of damaging winds. Very heavy rainfall will be a
threat in any stronger showers and storms that develop throughout
Saturday. Of course all of this discussion on severe threats will be
dependent on cloud cover from the early morning convection to allow
max destabilization during the afternoon. Rain chances will diminish
through the late evening/early overnight hours as the deeper
moisture departs to the east and the weak moisture starved cold
front moves overhead. A 1014mb high pressure and accompanied drier
air centered over Illinois is then progged to build into northern
Michigan...producing a less humid, but still warm day on Sunday,
with no rain chances.

Winds will be southwesterly Saturday morning and veering to more
westerly throughout the day. Wind gusts of 15-20 mph are expected.
Winds diminish in intensity during the overnight hours. Winds then
veer to more west-northwesterly behind the weak cold front with some
gusts of up to 25 mph possible...especially during the afternoon
hours Sunday.

Temperatures will be in the low to mid 80s, but with the very humid
airmass, heat indices will be in the upper 80s to low 90s.
Temperatures will be warmer Sunday, but be less humid, with highs
reaching into the mid 80s to near 90. Overnight lows Saturday night
will drop into the upper 50s to low 60s.

&&

.LONG TERM...(Monday night through Friday)
Issued at 317 PM EDT Fri Jul 23 2021

High Impact Weather Potential...Minimal.

Typical summer weather for northern Michigan. High pressure will
dominate the weather Monday producing rain-free weather and warm
temperatures. Beyond Monday there are some hints of weak
disturbances that may produce chances of showers at times, but all
in all, rain-free weather will most likely be the predominant
winner. As these disturbances become closer, timing, duration, and
intensity will be more fine tuned. Daytime high temperatures appear
to be in the 80s, with some locations nearing 90...especially Monday
and Tuesday over the far southeastern forecast area.

&&

.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 317 PM EDT Fri Jul 23 2021

Tonight through Sunday...Winds will begin increasing tonight as the
gradient begins to tighten up overnight with the approach of the
cold front. there may be some brief gusts on Lake Michigan that
could get to small craft criteria, by Saturday morning, but think
that the main winds won`t be until after the front goes through,
probably Saturday night. However, the winds don`t look to increase
Saturday night and Sunday, as the front moves through high pressure
builds in, and the gradient relaxes for the night, and into
Sunday.

&&

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

$$

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