066
FXUS63 KAPX 050345
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1145 PM EDT Thu Jul 4 2024

.KEY MESSAGES...

- Increasing rain threat...mainly late tonight and moreso into Friday.

- Severe thunderstorm possibilities Friday? Day 2 SPC Marginal severe
  risk now encompassing most of northern Michigan.

- Fluctuation temperatures with periodic shower chances through
  the extended.

&&

.UPDATE...
Issued at 949 PM EDT Thu Jul 4 2024

Vertically-stacked low pressure continues to develop over
Minnesota late this evening...generating several areas of
showers and thunderstorms currently impacting portions of
Minnesota...Wisconsin and Iowa. Closer to home...spotty showers
have tried to develop during the afternoon and early evening
with limited luck due to dry low level northeasterly flow. Loss
of diurnal heating/instability has brought any spotty shower
activity to an end. However...still do expect low levels will
gradually moisten overnight to allow upstream shower activity to
make steady west to east progress into our CWA. Limited
instability (MUCAPES of up to 500 J/kg) will lend to some
embedded thunder...but weak wind fields will preclude any strong
to severe storms overnight. Overnight lows will cool into the
50s across Eastern Upper Michigan and into the lower 60s across
Northern Lower Michigan.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 331 PM EDT Thu Jul 4 2024

Pattern Synopsis/Forecast:  Pretty disorganized (read: summertime)
surface pattern across the Great Lakes and Midwest this afternoon.
Broad area of low pressure over western Minnesota into western
Iowa...main center probably along the state line where 2-3mb/3h
pressure falls occurring.  Warm front extends east across southern
Minnesota into southern Wisconsin.  Weak pressure gradient across
the upper Lakes allowing for widespread lake breeze development this
afternoon.  This is occurring ahead of a short wave trough over the
eastern Dakotas/Nebraska...with several embedded vorticity centers
in water vapor imagery over southwest Minnesota and southern
Wisconsin.

High level overcast across northern Michigan at mid afternoon along
with a scattered Cu field at least (hard to tell with the
intervening Ci layer).  Some nominal MLCAPE  (~100-200J/kg) has
developed along the southeast shore of Upper Michigan...right along
the Lake Huron shore south of Thunder Bay...as well as west of the M-
37 corridor...due to onshore flow off the lakes and/or moisture
pooling along the lake breeze (in the U.P. and northeast Lower
case...where there are some hints of enhanced Cu on radar).

The short wave trough moving through the northern/central Plains
will arrive over the upper Lakes Friday morning along with its
associated surface wave (~1005mb).  These features will cross
Michigan Friday/Friday night...probably with secondary cyclogenesis
occurring over Lower Michigan Friday afternoon.

Primary Forecast Concerns:

Increasing rain threat...mainly late tonight and moreso into Friday:
Aside from the wannabe showers trying to form near Saginaw Bay...
upstream precipitation is concentrated around the short wave trough
over the eastern Dakotas/southern Minnesota...as well as over
central Wisconsin though that seems to be higher based.  Current
thinking is that the bulk of the measurable precipitation won`t
arrive until after midnight.  Passage of lead vorticity center over
Wisconsin may bring some virga or very light rain/sprinkles this
evening given relatively dry lower levels...but expect rain to
expand/develop eastward Friday morning with arrival of better
moisture/forcing.  Rain will likely be more persistent the farther
north you go on Friday...across central Lower Michigan potential is
for more a more showery/convective nature (and perhaps heavier from
a QPF standpoint) to the precipitation along the occluded boundary/
secondary cyclogenesis forecast to occur over central Lower Friday
afternoon.  Which leads to our next concern...

Severe thunderstorm possibilities Friday?  Day 2 SPC Marginal severe
risk now encompassing most of northern Michigan:  Greatest threat
area for severe storms Friday probably more confined to northern
Lower (maybe even south of M-32) closer to the occluded front and
secondary cyclogenesis where better instability (perhaps getting
close to 1000J/kg MLCAPE) and better deep layer shear will reside
(strongest shear expected over southern Lower but forecast
hodographs look pretty stretched out in our neck of the woods).

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 331 PM EDT Thu Jul 4 2024

Pattern Synopsis/Pattern Forecast:

Rather amplified upper level flow regime (especially for summer) set
to further establish itself as we head through the weekend into
early next week...featuring western NOAM heat dome/deep layer ridge
axis upstream of broad Great Lakes centered troughing. Such a
pattern supports no prolonged periods of heat and periodic shower
chances across the Great Lakes region.

Primary Forecast Concerns/Challenges:

Shower potential and temperature trends through the entirety of the
long term period.

Details:

Beyond Friday (see Friday`s details in the short term section
above), the rest of the weekend shaping up to be rather uneventful.
While departure of moisture rich primary shortwave Friday evening
ends the most widespread rain potential, lingering troughiness does
support at least some scattered light shower concerns through the
day Saturday. Still, trends definitely support much of the time and
most of the area remaining dry through Saturday, with any showers
past Friday evening remaining fairly light and scattered. Kinda the
same story for Sunday...although some support for a passing
shortwave ridge during the morning in mid-range guidance may
suppress moist convection even further. Again, cannot completely
rule out an afternoon shower or storm...especially where lake breeze
convergence axes are maximized.

Weather potentially gets a bit more active yet again heading into
next work week, with growing support for a rather robust shortwave
trough to visit the region. Of course, overall strength, timing, and
moisture availability all remain in question at this early juncture.
Unfortunately, forecast will display this uncertainty by showing an
extended duration of rain potential...when in all likelihood, the
actual duration of better rain chances will fall int a much shorter
time period. What transpires with the early week system (mainly
speed and depth) will have a lot to say on how the remainder of the
week unfolds.

As mentioned earlier, long wave flow regime does not support any
prolonged heat up here in the Northwoods. Expect temperatures to
fall well within the range of what is considered normal for this
time of year.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1145 PM EDT Thu Jul 4 2024

Vertically-stacked low pressure will slowly slide thru the
Western Great Lakes region thru Friday night. Chances of
showers and thunderstorms will steadily increase overnight thru
Friday. Prevailing conditions will remain VFR for the next 24
hours...but may briefly drop to MVFR/IFR within any heavier
showers/storms. Light/variable surface winds overnight will
become easterly under 10 kts on Friday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

UPDATE...MLR
SHORT TERM...JPB
LONG TERM...MSB
AVIATION...MLR