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000
FXUS63 KAPX 242016
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
416 PM EDT Wed Apr 24 2024

.KEY MESSAGES...

--Chilly tonight; record lows possible...

--Quiet and dry Thursday.

--Potential for rounds of showers and thunder present from Friday
night through Monday.

--Non-zero chance for severe thunderstorms, particularly later
Saturday into Saturday night.

&&

.SHORT TERM /THROUGH THURSDAY/...
PATTERN SYNOPSIS/FORECAST:

Ridge axis to our west...and high pressure to our north...with
development of usual mesoscale/diurnally driven low over the US-131
corridor this afternoon; already seeing lake breeze development
across the coastal areas. Otherwise...cold and very dry airmass
overhead...with dewpoints in the single digits across much of the
EUP and parts of the Tip of the Mitt. Weak bit of PV over Manitoba
into Ontario attm.

Expecting a chilly night tonight as high pressure settles in...with
lows dropping into the teens, making a decent run at record lows
tonight. High pressure to remain in place going into Thursday, with
continued dry air and light flow overall...with return flow on the
way for later Thursday afternoon.

Primary Forecast Concerns:

Cold temps tonight...High pressure oozing south with very dry air
mass in place, noted by dewpoints this afternoon in the single
digits in many areas (e.g. 3F at Harbor Springs, 7 at Grayling,
etc). Think we will largely decouple...though with that weak
disturbance to our northwest progged to slip by to our north late
tonight...do have to wonder if this will keep pressure gradient just
tight enough to preclude fully decoupling in some areas...which
could bust the current low temperature forecast. Highs today
struggling through the 40s (or to even reach the 40s in some spots),
which, with a typical climo diurnal temp swing, would suggest lows
in the teens....and I may not be cold enough...particularly if we
bottom out as much as current dewpoints suggest. This being
said...did struggle to find guidance as cold as I have in the
forecast, and I ended up manually adjusting per the above ideas as a
result...which does bother me a bit, that even some MOS guidance is
not terribly supportive of much colder than perhaps the 20s or upper
teens. Think the entire column should remain below freezing
tonight...suggesting that even attempting to mix inversions would
not be helpful for anyone trying to mitigate freeze concerns.

Temperatures to recover into the 50s Thursday with high pressure
overhead, and slight return flow suggests we won`t be /quite/ as dry
as we have been today. That being said...still expecting critical
RHs over much of the area, particularly favored for areas that may
downslope on background S/SE flow. However...expecting flow to
remain light, with little in the way of wind aloft to mix
down...such that fire weather concerns may be tempered a little bit
compared to perhaps Friday (see long term discussion)...though lake
breezes will still be a concern.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Pattern Synopsis / Forecast: Quick turnaround from the more trough
dominant regime in the cards as we head into the weekend. Pacific
wave and associated surface low pressure just east of the Rockies
will drive a stout ridging response into the weekend, drawing in
warmer and more moist air with time as a baroclinic zone establishes
itself from the southern Rockies into Lake Superior. This zone will
be the focus for numerous ejecting waves, the first being the
aforementioned system east of the Rockies, set to be heavily
occluded and moving into a hostile environment Friday night into
Saturday as it approaches the upper Great Lakes. Surface warm
frontal boundary will be on the move, passing through at least part
of the region Friday night into Saturday and forcing dominant high
pressure east into the northern Appalachians. The result will be a
period of showers and storms Friday night into early Saturday. The
primary surface low then passes through Lake Superior later
Saturday, forcing a cold frontal boundary farther south into the
region and bringing about another chance for a round of showers and
thunder. Looking farther ahead, active baroclinic zone is set to
generate another convectively charged wave and associated surface
low pressure that passes through the region Sunday into Monday,
bringing about yet another chance for a round of showers and
thunder. Long term guidance wants to bring in a more seasonable
airmass behind this final wave as we progress into the middle of
next week.

Primary Forecast Concerns:

Before we get into the more active / wetter period of the forecast,
thing to watch will be a tightening pressure gradient increasing
flow at the surface. With the breezy nature of the day, coupled with
lots of dry air in the low levels may contribute to some favorable
wildfire growth conditions as we continue through pre-greenup and
attain sustained winds of 10-20mph, with some gusts up to 25-30mph.
Still some uncertainty as to how high we gust considering this is a
warm air advection setup (inversion aloft suppresses deeper mixing),
but diurnal heating may allow for just enough of a steepening low
level lapse rate to mix some higher gusts to the surface. In
addition, drier air aloft may be mixed to the surface, which could
crater dewpoints into the 20s and perhaps upper teens, especially in
downsloping locales in SE flow (this in particular favors NW lower).

Dry influences from high pressure will be offset by incoming
moisture surge Friday evening into the overnight hours associated
with northward surging surface warm frontal boundary. Stable layer
beneath axis of elevated instability should help the cause in
generating at least some showers Friday night into Saturday.
Questions arise with the depth and magnitude of any elevated
instability, but some guidance members still support some semblance,
which puts a couple of rumbles of thunder in play too. As far as the
steadier rain goes, drier flow from the departing high pressure
probably puts a dent on initial intrusion attempts of more
stratiform rainfall, leaving the most appreciable rainfalls
influenced heavily by any convective processes.

Current consensus with guidance wants to rocket the surface warm
front all the way to the Soo by Saturday morning, which would open
the gates for warmer air to surge into the region. Still some
uncertainty with this warm frontal position considering climo
tendencies for these fronts to struggle with the cold lakes,
especially with a colder high pressure to the northeast... but in
this case, high pressure will be more situated north and west as the
ridging axis amplifies well into Quebec. This should lead to
lessened resistance to the warmer air for the day Saturday...
potentially well into the 70s if we can get some breaks in the
clouds. How this frontal positioning and temperature trend goes will
be paramount to how things evolve farther down the line Saturday
evening.

Secondary impulse of forcing associated with the surface low and
cold frontal boundary progged to make a passage through the region
late Saturday into Sunday. Somewhat unfavorable timing, but with
aggressive southerly windfield and dewpoints likely ballooning well
into the 50s and (maybe even the lower 60s), probably not much
diurnal cooling on the table. This unstable airmass gives potential
for another round of showers and thunder, potentially severe (as
pointed out by previous forecaster) given ample forcing and
favorable dynamics with this system passing through northern
Wisconsin (a favorable severe weather track for northern Michigan,
especially with a deepening low, but in this case, we will not have
a deepening low). Still some uncertainty as to how these impulses
will affect the Northwoods, so more updates to be had.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
High pressure continues to slip in. Little to no clouds expected
through the next 24hrs with very dry air mass in place. Winds drop
off tonight, with most areas going light and variable. Have
explicitly included offshore (easterly) flow in TAF for KMBL
overnight given greatest confidence there; could also be possible at
APN and TVC but less certainty in direction. Winds become more
southerly after sunrise Thursday morning through the rest of the
day...though still not expecting much in the way of cloud cover till
well beyond this TAF period.

&&

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

&&

$$

SHORT TERM...FEF
LONG TERM...HAD
AVIATION...FEF