UPDATE
Issued at 1013 PM EDT Sun Sep 15 2024

Pronounced ridging remains locked across the Great Lakes region late this evening. Strong subsidence and dry air thru the column continue to result in mainly clear skies and calm conditions.
Certainly expect some patchy fog development overnight. Low temps will cool into 50s.

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/HRRR visibility probabilistic guidance also hinting at these areas so will utilize some combination of SREF 3mi visibility and HRRR 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 /00Z TAFS THROUGH 00Z MONDAY/
Issued at 700 PM EDT Sun Sep 15 2024

Persistent high pressure still centered off the New England Coast will continue to hold in place...maintaining pronounced low level ridging extending back thru the Great Lakes region.
Some patchy fog will again develop overnight in our usual spots...otherwise expect VFR conditions thru Monday night. Light SE winds tonight will become S/SW AOB 10 kts on Monday.

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