255
FXUS63 KAPX 172301
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
701 PM EDT Fri May 17 2024

.KEY MESSAGES...

- Warm Saturday.

- Weakening cold front arrives Saturday night...dwindling rain threat
  along it.

- Sunday afternoon lake breeze convection near Lake Huron? (Definitely
  a non-zero probability)

- Weather more unsettled starting Monday...strong storms maybe Tuesday
  night?

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 351 PM EDT Fri May 17 2024

Pattern/Synopsis: Decaying surface front has progressed into ne
lower MI. After that washes out, broader and warm southerly flow
gets established tonight and especially Saturday, well ahead of low
pressure in s central Canada.

Forecast: With stronger surface heating finally being realized,
convection has sprouted in ne lower MI, where moisture is pooled
near the decaying front. SPC mesoanalysis has a skinny axis of circa
1k j/kg of MlCape extending into ne lower MI. First couple cells of
the day had no problem getting strong, with one become marginally
severe. Now outflow air covers a good portion of this area, though
there is time for recharging. Additional cells should also cook off
along the westward-moving outflow boundary, though instability is
weaker with westward extent (BL moisture is less...59f dew point at
APN now, vs 50 at GLR and 48 at TVC). Convection will continue to be
extremely averse to moving out over chilly Lk Huron.

Spotty convection should continue in ne and perhaps n central lower
MI, well into evening. Have stretched out those pops a little
longer. A n-s convergence line is also progged to form down the
spine of central lower MI over the next few hours, thanks to
continued heating. A number of HRRR runs generate convection here by
early evening, then propagate it east with some marginal upscale
growth. Another reason to stretch out pops a hair longer.

Otherwise, diurnal cu will diminish. Light surface winds will allow
for good radiational cooling. Low-level moisture will be less than
this morning (except potentially for where it rains). Do have plenty
of low clouds (and fog) returning to eastern upper and ne lower MI
by morning. Fog/stratus should be more localized in nw lower MI.

Min temps upper 40s to lower 50s.

Fog/stratus should be somewhat faster to erode Saturday. Ne lower MI
coastal counties, and eastern Chip/Mack Cos, could see clouds until
almost lunchtime. Otherwise, mostly sunny skies, and with warm
advection beginning, it`ll be toasty (away from the big lakes).
Highs were boosted into the lower 80s across much of northern lower
MI, with 70s along the coasts and in eastern upper MI.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 351 PM EDT Fri May 17 2024

Pattern Forecast: Several pieces of short wave energy lined up in
the northern branch wave train extending across the Pacific.  First
feature of interest is over the Pacific Northwest this afternoon
that will swing across the upper Midwest and into northern Ontario
Saturday...with another wave on its heels Sunday but this trough
will dig/amplify over the western U.S. to start next week. Southwest
flow aloft will predominate across the Great Lakes...with a spell of
warmer and potentially more unsettled weather by midweek as a
result.

Lead short wave moving into Ontario will push a cold front into
Michigan Sunday though it will likely tend to wash out.  After that
evolution of western trough and its impact on the surface pressure
pattern starting Monday as an intial lee cyclone that develops as it
tracks into the upper Midwest and (perhaps) the upper Lakes Tuesday
but there is spread in the ideas of system evolution which will
dictate timing of cooler air back into Michigan (roughly Wednesday
vs. Thursday).

Primary Forecast Concerns:

Weakening cold front arrives Saturday night...dwindling rain threat
along it:  Expect a line of convection to develop along the front
over western Upper/Wisconsin Saturday afternoon/evening...with the
remnants moving toward northern Michigan Saturday night along a
narrow low level theta-e axis coincident with the front.  Better
rain probabilities are indicated across eastern Upper but can`t
really rule out some rogue showers popping anywhere overnight into
Sunday morning (northeast Lower).

Sunday afternoon lake breeze convection near Lake Huron? (Definitely
a non-zero probability):  Cold front looks to fall apart across
Lower Michigan Sunday but a weak gradient expected to allow for lake
breeze development with strongest convergence near Lake Huron.
Coincidentally looks like a west-east moisture gradient is going to
set up (boundary layer mean mixing ratios ranging from around 4g/kg
eastern Upper to 11g/kg near Saginaw Bay.  As a result dew points
will likely remain in the 55-60F range roughly east of an HTL-APN
line.  This should generate several hundred J/kg MLCAPE values...
enough to justify at least some PoPs over parts of northeast Lower
(same area mentioned above).  NBM probabilities are hinting at this
but have blended in higher SREF PoPs to better get the idea in the
forecast.

Weather more unsettled starting Monday...stronger storms maybe
Tuesday night?: Surge of deep moisture into the Great Lakes ahead of
the digging upper trough (precipitable water values 1.25+ inch) will
begin to increase rain chances on Monday (evolution of this may
revolve around upstream convection which always complicates things).
But arrival of the surface low and attendant warm sector into the
upper Lakes on Tuesday certainly portends the potential for more
significant weather...especially on the other side of Lake Michigan
as usual but a nice nocturnal squall line passage could be in the
offing Tuesday night.  At least the setup is good for it...the devil
is in the details of course. SPC Day 5 15% severe probability
knocking on western Lower`s door...along with the Day 5 marginal
risk the WPC Excessive Rainfall Outlook which is not unreasonable
given the potential magnitude of moisture advecting northward.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 700 PM EDT Fri May 17 2024

Weak high pressure centered over Eastern Upper and Lower Michigan
will slowly push eastward tonight into Saturday. Meanwhile...an
upstream cold front will slide into the Western Great Lakes
region Saturday afternoon and night. Dry wx is expected across
our area tonight thru Saturday evening...before chances of
showers and storms begin to increase late Saturday night. In the
meantime...VFR conditions will persist thru this evening...
before areas of low stratus/fog/IFR conditions develop late
tonight into early Saturday across Eastern Upper and far
Northern/NE Lower Michigan. VFR conditions will return to this
area later Saturday morning and afternoon as daytime mixing
helps to lift/dissipate the low status and fog. Light/variable
winds tonight will become SE under 10 kts on Saturday...lending
to lake breeze development along our shoreline areas.

&&

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

&&

$$

SHORT TERM...JZ
LONG TERM...JPB
AVIATION...MLR