Marine Weather and Tide Forecast for Frankfort, MI

SHORT TERM /THROUGH TONIGHT/
Issued at 340 AM EST Sat Dec 7 2024

Pattern/synopsis: A shortwave will amplify somewhat as it races ese-ward across Lk Superior this evening. Surface low pressure in southern Manitoba will organize and deepen as it passes by northern Superior this afternoon. Warm/moist advection is increasing into the northern/western lakes early this morning.

Forecast: A few wnw-flow flurries in the area this morning, with a somewhat stronger band off of Rogers City. A shield of synoptic returns is advancing across Lk Superior and western upper MI. The leftover lake aggregate trof in its classic position morphs into a surface warm front.

The entire system is advancing quickly se, and intensifying.
Strong 850-700mb theta-e advection will support a precip shield crossing the area today. Initial precip elements will move into western Chip/Mack Cos and Beaver Isl before dawn. Most of the precip will stay ne of a Leland-TVC-Lake City line. Though warm advection is substantial today, 850mb temps start out at -8C over northern Lake MI at 12Z. Lake enhancement will occur this morning, especially early, with sw flow off the Lake. 850mb temps will jump above 0C by 18Z. Total QPF will range from a third- to half-inch from Emmet Co north across eastern upper MI.
Snow-liquid ratios will deteriorate as the warmer air moves in.
In fact, an outright switch to rain will occur this afternoon, over and downwind of Lake MI. By sunset, the most widespread precip has exited, but what is left will be mainly liquid, with a mix still possible in central and northern Chippewa Co.

Snow amounts today in eastern upper MI range from 4" in Naubinway to 7" near the Sault. Lake enhancement, and some hills to work with, will also generate 2-5" inch accums in central/northern Emmet Co. Advisories will be issued for only the above counties (so not Cheboygan Co, nor Beaver Isl).

Tonight, deeper moisture is departing eastward. The low levels remain moist, with some spotty DZ and light rain showers for part of the evening. Winds veer nw behind the departing system, and colder air returns overnight. 850mb temps lower to -8C over eastern Superior. Light snow showers and perhaps -FZDZ may develop in eastern upper MI overnight.

Max temps today 30s to lower 40s. Lows upper 20s to mid 30s.

LONG TERM /SUNDAY THROUGH FRIDAY/
Issued at 340 AM EST Sat Dec 7 2024

PATTERN SYNOPSIS/FORECAST:

Cyclonic flow remains in place over the eastern portion of the continent, with upper low centered over Hudson Bay and anomalous low pressure over northeastern Canada...and Rex block still hanging on across the western US. Some energy still managing to crest the ridge, however...with 140+kt upper level jet crossing into the central Canadian Prairies...helping advect anomalous moisture eastward across this same region into the Upper Midwest: pwats of 0.5-0.7 inches running at 2-3 standard deviations above the mean. PV maxima over Manitoba in the exit region of the aforementioned jet...with strengthening thermal gradient and attendant surface warm front stretching across Lake Superior into southeastern Ontario...where a weak surface low is located, associated with a subtle PV wave. 850mb temps finally warming toward -10C over the Upper Great Lakes, even northern Michigan...with the 0C line as close as the Upper MS Valley.

Niblet of energy skirts by to our northeast tonight into Sunday...dropping another zonal BCZ over the area as the next system already starts to strengthen over the western US. Think Sunday should be rather dreary, with (briefly) stagnant flow following warm, moist advection over the existing snowpack (great setup for fog). System begins to wind up over the northern Plains Sunday night into Monday...at the same time as remnants of Desert SW troughing advects eastward into the OH Valley. For now, expecting these two features to stay largely separate...but if by some chance they don't...it could open the door for even deeper moisture to get into our region (beyond the anomalous moisture left behind by today's system). Will become breezier going into Monday as the upstream system winds up...and warm advection should largely keep gustiness to a minimum in the warm sector of the system...but could be a little gustier where the boundary layer remains influenced by overlake instability (i.e., the EUP). Anyhow, will expect warm front to lift through the region ahead of this system Monday...with potential for the rain/snow line to hang out across the Tip of the Mitt/Straits region. Occluded low will be slow to move through Monday night into Tuesday...as troughing sharply digs over the central Plains/MS Valley. Sharp trough axis swings through the eastern US midweek, driving development of an east coast system...and keeping things cold and cyclonic (lake effect-y) for the middle portion of the week
Beyond Thursday
increasing uncertainty in how the pattern evolves, though there are general signals for things to remain a bit more progressive (perhaps milder?) and active into the latter part of the upcoming week.

Primary Forecast Concerns:

Wintry mix possible Sunday night into at least Monday... Think there could be some drizzle/freezing drizzle around Sunday afternoon...but with top-down saturation on the increase from the west...think there is a shot this could transition over to some snow toward dusk.
However...if there ends up being mid-level dry slotting overnight, as some guidance soundings suggest...we could fluctuate back and forth between snow/drizzle for a decent chunk of Sunday night across northern Lower; freezing drizzle is a distinct possibility as surface temps could remain at or below freezing over the interior in particular...and my forecast may be a little on the bullish side toward this idea because of this. Best chance for things remaining mostly or all snow (likely a slick, wetter snow) will be across the EUP...though a stronger northward surge of the warm nose aloft could shunt p-type issues deeper into the Yoop...particularly given easterly low-level flow that could drag colder/drier air into the EUP...and persist this idea longer. If things remain all snow longer for the EUP, probabilistic guidance hints at the potential for greater than 4 inches for the Soo area by Monday evening. Guidance points strongly toward the potential for a dry slot through the bulk of the column Monday during the afternoon with the passage of a cold front; do have some concerns the lingering boundary layer moisture from the melted snow could keep things from clearing too aggressively, though. Think we could be looking at the potential for a band of rain/snow right along a secondary trough axis swinging in late Monday/Monday evening. Guidance soundings suggest some potential for more vigorous convective activity with this band, particularly if we do break out of the clouds during peak heating...noting some potential for surface-based cape and/or weaker stability aloft.

Lake effect returns Tuesday and beyond...Falling temps aloft Tuesday should increase overlake instability and lead to the return of lake effect. Not impossible some areas could remain warm enough to not achieve ice nucleation and thus hang onto the mixy/freezing drizzly idea a bit longer into Tuesday. However, as cold air pours southward into the sharpening trough axis going into Wednesday...will expect we will be cold enough by then (highs in the teens?) to have all snow...some of which could be beefy at times as deeper synoptic moisture accompanies the better synoptic lift to enhance any ongoing lake effect.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
Issued at 628 AM EST Sat Dec 7 2024

Snow is invading the area this morning. The most substantial snow is expected at CIU (LIFR for a few hours this afternoon), and to a lesser degree PLN/APN (IFR for part of today).
Otherwise MVFR cigs will prevail into this evening, with some places seeing improvement late tonight.

Southerly winds today become westerly tonight.

APX WATCHES/WARNINGS/ADVISORIES
MI...Winter Weather Advisory until 5 PM EST this afternoon for MIZ016-086>088-095>097.
MARINE...Small Craft Advisory from 10 AM this morning to 7 AM EST Sunday for LHZ345>349.
Small Craft Advisory until 7 AM EST Sunday for LMZ323-341-342- 344>346.
Small Craft Advisory from 10 PM this evening to 10 AM EST Sunday for LSZ321.