609
FXUS63 KAPX 051215
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
815 AM EDT Fri Jul 5 2024

.KEY MESSAGES...

- Multiple rounds of showers and storms expected into this
  evening. Low chances for severe storms this afternoon.

- Periods of Rain/storms through the weekend

- Rain/storm potential Monday/Tuesday?

&&

.UPDATE...
Issued at 812 AM EDT Fri Jul 5 2024

Inherited forecast seems to be largely on track. Showers are
beginning to fill in across northwest lower and EUP this
morning. These showers will spread west to east through the
morning before another round of showers /storms pass through
later this afternoon into this evening. The potential for severe
storms continues to be low with the main hazard expected to be
lightning with possible gusty winds and large hail. Main
forecast challenge will be the timing of showers/ storms this
afternoon as guidance has been trending a later arrival time
than previously suggested... The showers and clouds passing
through this morning will largely influence how/ when the
afternoon showers will develop: If showers and clouds linger
into the afternoon hours, the environment will take longer to
destabilize, and therefore, the arrival/ timing of the
showers/storms will be later in the day and the potential for
severe storms continues to decrease. As such, be sure to stay
weather aware today and have multiple ways to receive weather
alerts, especially if you are participating in any outdoor
activities!

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 356 AM EDT Fri Jul 5 2024

Pattern Synopsis:

Longwave troughing will gradually pivot across the north-central
CONUS into this weekend as a seasonably strong jet rounds its axis
and punches over the southern Great Lakes today. Forcing provided by
this feature aloft will support a deepening cyclone that is expected
to trek across the lower peninsula this afternoon and evening,
eventually departing east of the region later tonight.

Forecast Details:

Multiple rounds of showers and storms, low chances for severe --
Scattered showers across parts of northern Michigan will continue to
expand in coverage from west to east this morning as the
aforementioned system moves closer to the region. While some rumbles
of thunder cannot be ruled out with activity this morning, numerous
showers and storms are expected to form across the area beginning
shortly after noon. Thunderstorm clusters are expected to be more
disorganized in nature with relatively weak effective shear (~20-25
kts) in place given relatively low ELs/tropopause height. While
forecast hodographs do display streamwise vorticity in the lowest
few kilometers, weak low-level shear (~10 kts 0-1km shear) should
lead to shrunken hodographs with <100 m2/s2 0-1km SRH -- leading to
very low confidence in any tornado potential despite the potential
for some weakly rotating storms should any become more organized.
Damaging wind gusts and large hail will be possible with any strong
storms, but confidence remains low in these hazards as well.
Aforementioned low cloud tops will keep the majority of the profile
warmer than -10 to -20 C, making it even more difficult for large
hail formation given already relatively weak effective shear. Strong
wind gusts will be possible, but <20 kt flow through the lowest
several kilometers of the profile also decreases confidence in this
potential. The primary hazard will most likely be lightning given
the fact that there is an influx of people across northern Michigan
here to enjoy outdoor activities for the holiday weekend. Those
planning any outdoor activities should be paying close attention to
the forecast, and have multiple ways of receiving weather
information and warnings -- primarily this afternoon and early
evening when thunderstorms are most likely. Thunder chances will
diminish into tonight with lingering chances for showers lasting
into Saturday morning.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 356 AM EDT Fri Jul 5 2024

PATTERN SYNOPSIS/FORECAST:

Broad troughing over the northern Plains attm...with ridging over
the West Coast...and southeastern US. Southwesterly flow crossing
the central US; abundant moisture (pwats of 2in or more) and some
convection along and ahead of a surface boundary stretching from TX
into the OH Valley. PV max over MN within broader troughing; this
feature has spawned some convection upstream amid slightly better
moisture and better forcing...along and ahead of a low over
MN with small warm front over S. WI...and cold front extending back
into northern TX. Otherwise...a rather nebulous pattern over the
Upper Great Lakes...with a NW-SE oriented cold front well to our
north in Canada. It remains reasonably mild, however, with 850mb
temps in the 15C range...and temps yesterday topped out largely in
the low 80s as a result.

Low over WI expected to slowly meander ENE-ward through the start of
the actual weekend...not fully departing the region till later
Saturday afternoon as a secondary trough axis slips through, leaving
the potential for showers and storms in the forecast to start the
weekend. Break in the action behind this may only be brief...with
chances for activity poised to return Sunday afternoon as another
niblet of energy swings in...though not a full washout by any means.
Will then be looking for another round to approach the area going
into Monday...as upstream trough axis strengthens; this feature is
currently progged to swing across the Upper Midwest (including
Northern Michigan) Tuesday...as remnants of T.C. Beryl meander
inland somewhere over the southern portion of the continent. Beyond
this...expecting upstream pattern to break down and allow ridging to
spread eastward into the central US going into the middle of next
week and beyond.

Primary Forecast Concerns:

Periods of rain/storms through the weekend...

Saturday...not necessarily the most impressive setup, but appears we
could be unstable enough to get some convection to redevelop,
especially along and ahead of the secondary trough axis swinging in
Saturday afternoon...especially if we get enough diurnal heating to
destabilize the lower levels enough to overcome somewhat more stable
layers in the mid-levels. It will also help if we end up more moist
from rain today/tonight...as this could further boost
destabilization potential with diurnal heating. Probabilistic
guidance currently points toward development of a few hundred joules
of CAPE attm, which is worth keeping an eye on, noting the abundance
of outdoor activities going on over the region today. This would
more likely be skinny CAPE, which could promote better rainfall
rates, with freezing levels still up around 3km or so. Do wonder if
these will be soggy showers moreso than thunder threats, though
thunder will still be a threat, particularly if we are able to get
better surface heating during the afternoon ahead of the front. Weak
shear/wind profiles Saturday suggest a general lack of organized
severe threat, though not impossible some could pulse up and produce
some small hail and/or gusty downbursts. Additionally, think storm
motion/propagation could end up driven more by mesoscale/storm-scale
outflow boundaries than anything else (e.g., not impossible we could
get a lake breeze on the Lake Huron coast Saturday afternoon), such
that storm motion may not be as predictable as normal, which could
be problematic for people out and about this weekend. Furthermore,
if cells are able to sit over an area for an extended amount of
time, not impossible it could lead to some localized flooding
concerns at worst-case scenario. This idea also remains unclear
depending on how this event ultimately ends up evolving...but is
also worth keeping an eye on.

Sunday...think the better organized activity will remain to our
west, closer to better forcing...though environment still supports
potential for diurnally-driven showers and perhaps a rumble of
thunder or two over interior northern Lower in particular. Another
day with generally weak flow suggests these, too, will be the kind
of showers/storms that just meander here and there, moving
relatively slowly, and periodically pulsing up in intensity as
outflow boundaries from other storms move through (and/or lake
breeze development helps boost things). Kind of a stereotypical
summer storm idea.

Rain/storm potential Monday/Tuesday?...Though it`s still quite a
ways out...think we`ll have to keep an eye on Monday/Tuesday of next
week for our next major chance of rain/storms. Current setup
suggests southwest flow into the Upper Midwest; with some potential
to tap into tropical moisture depending on where Beryl ends up
tracking, think heavy rains could again become a concern if this
idea holds going forward. However...there are currently some signals
the axis of moisture transport could remain to our south, which
could shift the focus out of our area. Certainly something to keep
an eye on as we look forward into the start of next week, though
again...at this hour, nothing definite yet by any means.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 659 AM EDT Fri Jul 5 2024

Mainly VFR conditions are expected across northern Michigan into
this evening. Light showers will continue to work from southwest to
northeast this morning before scattered to numerous storms are
anticipated this afternoon into this evening. VCTS is included in
the TAFs to account for this. Temporary drops to MVFR/IFR will be
possible should any storms move over TAF sites. Otherwise, CIGs are
expected to drop to IFR -- and potentially LIFR -- later tonight
across most of the area.

&&

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

&&

$$

UPDATE...NSC
SHORT TERM...DJC
LONG TERM...FEF
AVIATION...DJC