836
FXUS63 KAPX 230134
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
934 PM EDT Sat Jun 22 2024

.KEY MESSAGES...

- Heavy rain threat continues into the night.

- Strong to severe storms remain possible into the evening.

- Near seasonal temperatures with periodic shower and
  thunderstorm chances next week.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 411 PM EDT Sat Jun 22 2024

PATTERN SYNOPSIS/FORECAST:

PV maxima shoving its way through WI...with surface low centered
just SW of GRB at 18z. Complex boundaries across the area...with a
warm/stationary front wrapping from the surface low over the Door
and Leelanau Peninsulas and draping down into the Saginaw Bay
region. Subtle surface convergence from TC to near Lake City...and
another potential wind shift from near GRB toward LDM. 40+kt LLJ not
entirely perpendicular to the strengthening boundary...but enough
for some continued theta-e advection, particularly with swath of SW-
NE oriented nearly 2" pwats aligning with the LLJ. Dry slotting
developing on the SW corridor of the surface low over central
WI...with some signals of more cellular/surface-based development
there amid better convective instability. Broad area of generally
stratiform rain moving overhead attm...though slightly more
convective signals developing in spots, particularly in the vicinity
of that convergence zone within the warm sector.

Upstream PV niblet and its attendant dry slotting over WI expected
to move into the area this evening/tonight...dragging a cold front
into the region behind the surface low expected to trek across
northern Lower (likely the Tip of the Mitt) tonight. Continued
efficient rain expected with this; severe weather still remains a
possibility into at least the evening with decent deep layer shear
and potential for better instability hanging on into at least part
of the night. Expecting cooling and drying behind the cold front
into Sunday morning from NW-SE...with slightly gusty northwesterly
winds developing on the back of the system. Think we will get some
wrap around nonsense over NE Lower and the EUP Sunday afternoon as
another wave drops in...which could generate a few more
showers or even storms, though these may not be very robust either.

Primary Forecast Concerns:

Heavy rain threat continues into tonight...Think the heavy rain
threat will hang on over the M-32 corridor and south through the
evening...actually, through the bulk of the period, as the next
batch of forcing moves in with the pv max tonight...focusing things
more over NE Lower and points toward M-55/Saginaw Bay. A lot of
uncertainty in the placement of bullseyes, but still not out of the
question that some areas could see a localized additional 1-2" of
rain overnight given the environment and additional forcing expected
to drive through. Still some concern for either a northern shift in
the bullseyes tonight, and/or a secondary QPF max over the EUP/Tip
of the Mitt tonight into Sunday morning with the surface low driving
through...particularly noting some signals in guidance for the
surface low to track across the Tip of the Mitt. Do not have high
confidence in the QPF forecast that`s going out, as it effectively
shows signals for where the higher totals could be...but just low
confidence in placement...as well as potential for much higher
amounts than currently forecast. Additionally concerned that we may
have to watch for subtle areas of training convection.

Severe threat continues...Cohorts in the office attm watching some
embedded spinnies along a subtle convergence boundary down near
central Lower...which was one of the concerns mentioned in the AM
update: that embedded spin-ups in the atmosphere may just end up
being the primary severe concern. Not sure that much in the way of
wind will get to the surface this afternoon/tonight over our region,
apart from any downbursts with stronger convection toward Saginaw
Bay where there is a better shot at mixing things down to the
surface. Think this idea will hang on through the afternoon. May
have to watch areas back toward NW Lower (CAD to MBL) as clouds
attempt to break up in the wake of the convection with some dry
slotting slipping in ahead of the PV max. While there could be some
downward momentum transfer...soundings suggest we`ll have a strong
inversion in place around 800mb which could keep winds from becoming
too much of a problem...though suppose some hail threat may develop
if storms end up getting elevated like this.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 411 PM EDT Sat Jun 22 2024

Pattern Synopsis/Pattern Forecast:

Large scale flow regime completely unlocks this week, with full
retrogression of sub-tropical ridge axis into the Desert Southwest
and penetration of northern stream flow into the northern Conus and
Great Lakes region. This sets the stage for more seasonable
temperatures and periodic shower and thunderstorm chances across
northern Michigan.

Primary Forecast Concerns/Challenges:

Temperatures trends and addressing additional shower and
thunderstorm concerns through next week.

Details:

As mentioned above, much more northern stream influences into the
Great Lakes region next week. Several shortwave troughs set to crest
western ridge and drop southeast into the region, each accompanied
by what appears to be appreciable forcing and a decent pre-frontal
moisture environment. While still some subtle timing differences
with these waves (definitely to be expected in such an aggressive
flow regime), decent agreement amongst all mid-range guidance that
first such wave arrives during the Monday night-Tuesday period. Much
too early to get into any specifics regarding storm potential, but
what looks to be decent deep layer shear and respectable moisture
profiles through the vertical does at least raise an eyebrow to
brief heavy rain and severe concerns. Will continue to monitor of
course. More energy set to arrive the latter portion of the week,
again supporting more shower and storm potential. Multi-period
mention of rain chances through the extended centers on the
remaining timing uncertainty of these passing waves. Actual rain
chances will likely be relegated to a much shorter time
window...with those specifics working themselves out as we head
further into next week. Definitely not seeing any evidence of
prolonged heat in such a pattern. Temperatures will vary of course
based off frontal passages, but overall flavor to temperatures
should be well within the range of what is considered normal for
this time of year.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 934 PM EDT Sat Jun 22 2024

Low clouds expanding again tonight, then improving Sunday.

Low pressure will cross northern MI tonight. An additional round
or two of SHRA/TSRA will occur, with low vsbys at times, and
lowering cigs. IFR/LIFR conditions will become increasingly
common. Showers will diminish somewhat Sunday, and cigs will
slowly improve.

Winds will become nw on Sunday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...Flood Watch through Sunday morning for MIZ016>018-020>036-041-
     042-099.
MARINE...None.

&&

$$

SHORT TERM...FEF
LONG TERM...MSB
AVIATION...JZ