918
FXUS63 KAPX 151920
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
320 PM EDT Sun Sep 15 2024

.KEY MESSAGES...

- Persistence forecast for tonight/Monday (some fog tonight?
Warm/dry Monday with elevated fire danger).

- Continued warm and dry through this upcoming week.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 320 PM EDT Sun Sep 15 2024

Pattern Synopsis/Forecast: Pretty non-descript Sunday afternoon
across northern Michigan...other than the fact that temperatures are
running 5 to 15+ degrees above normal for mid September and that a
couple of record highs have gone down this afternoon (GLR 85/PLN
88).  Deep layer high pressure centered over the northeast CONUS the
culprit for our current stretch of late summertime warmth...though
it has been a bit too dry as month-to-date precipitation departures
showing a large swath of northern Lower having received less than 10
percent of normal rainfall and just about the entire forecast area
is below 25 percent of normal.  Skies are mostly sunny across
northern Michigan at mid afternoon with just some Ci overhead.
Convective clouds are bubbling up across northwest Wisconsin/western
Upper where dew points are in the mid-upper 60s.  Water vapor
imagery shows a couple of vorticity centers linked up along an
elongated PV anomaly that extends from the central Plains through
Upper Michigan/ central Lake Superior.  One circulation was drifting
into western Upper...with the second over northwest Missouri. MLCAPE
is increasing and capping decreasing across western/central Upper so
we`ll see if some convection can develop along that feature later
this afternoon.

Deep layer anticyclone not expected to budge through Monday...so a
continued dry anticyclonic trajectory into the upper Lakes means
more of the same for the first half of the week.

Primary Forecast Concerns:

Persistence forecast for tonight/Monday (some fog tonight? Warm/dry
Monday with elevated fire danger): Main issue tonight will be more
fog potential...which will probably be all dependent on the winds.
Last night had a wide range in low temperatures (49 HTL/50 PLN and
APN...with 60 ANJ/64 TVC and FKS).  Temperature/dew point spreads
likely to be similar to Saturday afternoon...and a few spots (APN)
went in the tank early. But 1000mb geostrophic winds around the
magic 15kt threshold may be just enough to keep things stirred up.
Not much of a signal to go on...eastern Upper and the northeast
Lower shoreline where onshore flow keeping dew points up should be
the areas most susceptible. SREF/HREF visibility probabilistic
guidance also hinting at these areas so will utilize some
combination of SREF 3mi visibility and HREF 4mi visibility
probabilities (and some pencil whipping) to get the idea in the
forecast (directly manipulating the PotFog grids rather than
deriving probs via visibilities).  Outside of that again expect a
wide range of lows tonight...with low lying areas of northern Lower
being coolest as the most likely areas to decouple.

A couple of record highs going down today and see no reason why a
few more records won`t be in jeopardy tomorrow as drying soils and
deepening boundary layer feeds back on itself.  Record highs for
tomorrow are: GLR (88/1955)...ANJ (85/2017)...HTL (88/1927)...TVC
(90/1955)...APN (90/1955)...PLN 89 (1955).  Record high at APN
stands the best chance of hanging on depending on how lake breeze
flow evolves during the afternoon.  Minimum relative humidity values
will likely drop below 30 percent with a similar dew point
trajectory as today I would imagine.  So will continue to hit the
elevated fire danger in the Hazardous Weather Outlook for the next
couple of days with fire danger ratings in the High to Very High
category.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 320 PM EDT Sun Sep 15 2024

Pattern Synopsis and Forecast:

Above normal height anomalies through much of this week will shunt
any appreciable rain threats to the south and/or west of northern
Michigan. In addition, sfc temperatures will remain above normal for
this time of year, even with dropping a couple of degrees into the
upper 70s to low 80s after Monday. Perhaps signs of the pattern
aloft beginning to soften a bit this upcoming weekend but this still
does not support any substantial precipitation threats, with above
normal temps remaining.

Earlier in the long term period, the combination of warm daytime
high temperatures and dewpoint temperatures in the low to mid 50s
will result in very dry conditions during the afternoon hours.
Afternoon humidity values will drop into the low to mid 30s across a
good chunk of interior northern lower on Tuesday, thus facilitating
high fire danger. Light winds are the only saving grace but
anamously warm and dry low level atmospheric conditions, in
conjunction with dry fuels, could facilitate erratic and dangerous
fire weather behavior nonetheless.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 114 PM EDT Sun Sep 15 2024

A mostly persistence forecast for this forecast cycle with
little change in the overall pattern/air mass. Aviation concerns
revolve around fog potential...which if the winds end up calm
overnight could see some visibility issues at KCIU/KPLN/KAPN.
There may just be enough of a gradient to keep things mixed
enough to prevent much fog...but temperature/dew point spreads
will be similar to yesterday when KAPN quickly went in the tank
once the sun set. But the light breeze potential is preventing
much of a fog signal in the both the deterministic and
probabilistic guidance. For this TAF cycle will carry some
overnight TEMPO groups for IFR visibilities at the above
mentioned terminals to at least get the idea in the forecast.

&&

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

&&

$$

SHORT TERM...JPB
LONG TERM...JLD
AVIATION...JPB