Area Forecast Discussion

FXUS63 KMQT 280843

Area Forecast Discussion
National Weather Service Marquette MI
343 AM EST Fri Feb 28 2020

.SHORT TERM...(Today and tonight)
Issued at 315 AM EST FRI FEB 28 2020

Right on schedule water vapor satellite shows deeper moisture and IR 
satellite shows colder cloud tops pivoting southward across the 
eastern half of Lake Superior early this morning. This enhancement 
on satellite corresponds to inverted troughing in the mid levels on 
the NW side of the deep upper low over Quebec. The result will be 
continued deep lake-enhanced/lake-effect over the eastern U.P. 
today. So far LES has taken the form of a scattered or broken, 
almost popcorn-like precip shield, which often limits accumulations 
relative to when more significant longer-fetch convergence bands 
form. However as this deeper moisture pivots in, there is some 
indication that a more cohesive band exists out there, now clipping 
parts of Luce County. It's too far out from nearby radars (the 
Environment Canada radar in Montreal River actually provides the 
best picture although even it is overshooting it somewhat) but along 
with the aforementioned satellite appearance and visibility down to 
1/2 mile to 1 mile between Newberry and the Soo, it's likely that 
some heavier, more persistent snow is falling out there this 
morning. None of the CAMs resolve a heavier, more stand-out band 
like this so therefore it's uncertain how long it will persist and 
thus if the current snowfall forecast - which is derived from more 
or less the WPC/CONSShort QPF and a 20:1 SLR - ends up being too 
low. At the opposite end of the spectrum, lake-effect precip has 
shut off entirely over the west, per satellite showing bands only 
forming right near the shoreline rather than at about the midpoint 
of the short axis of the lake and 10+ F T/Td spreads at Ironwood and 
Houghton. Models seem to have this resolved well with increasingly 
dry low levels expected through the morning. Therefore, have removed 
POPs for today anywhere west of a line from about Rapid River to 
Ishpeming to Copper Harbor.

For the rest of today, models are in good agreement that lake-
enhanced/lake-effect snow will persist throughout the day over the 
east with temps aloft continuing to be well supportive and deep 
moisture/lift aiding traditional lake-effect processes. Expecting 
less than 1" in Marquette to about 2" in Manistique to 4-8" 
additional from Munising to Seney to Newberry, with the higher end 
of that range being in the northern half to 2/3rds of Luce County. 
Given the models this morning show the deeper moisture hanging on 
until about 00z-03z, have extended the Winter Weather Advisories 
until 00z this evening. Even if the snowfall intensity drops off 
before the end time of the advisory, winds sustained around 15 mph 
and gusting to 30 mph inland and to 35-40 mph along the immediate 
Lake Superior shoreline will continue to lead to areas of blowing 
snow into the evening that could continue to make travel difficult. 
Have also kept the Lakeshore Flood Advisory running until 21z as 
previously scheduled as waves on Lake Superior are still expected to 
flirt with the 12 ft advisory threshold through early afternoon.

Tonight ridging builds in form the west and skies are expected to 
clear from west to east, except over the east where lake-effect 
clouds (and much lighter lake-effect snow showers) should persist 
through the night. With winds going light as well, it should be a 
chilly night. Went with the 25th percentile for low temps in the 
cloud-free areas, which works out to be about -2 to +5 F over the 
interior west, though it would not be a shock if this still ended up 
being too warm. Lows should stay closer to 10 above along the
lakeshores and across the east where cloud cover hangs on.

.LONG TERM...(Saturday through Thursday)
Issued at 329 AM EST FRI FEB 28 2020

Models indicate that a progressive almost quasi-zonal flow pattern 
will prevail from this weekend through much of next week. The mid-
level trough over the Great Lakes region will continue to push east 
this weekend giving way to ridging by late Saturday into Sunday as 
temps rebound back above normal by Sunday. By early to mid next 
week, a couple of weaker, moisture challenged, zonal flow shortwaves 
will move through the Upper Great Lakes with only light pcpn 
expected as temps stay generally above normal.  

Sat, lingering light nw flow LES should end Saturday morning over 
the east as the sfc ridge moves in, winds become lighter and back, 
low-level convergence weakens and 850 mb temps gradually moderate. 
Under partial sunshine WAA will boost temps into the upper 20s to 
lower 30s on Sat. 

Sun, WAA clouds increase ahead of an approaching shortwave and 
associated cold front although the best forcing and deeper moisture 
for pcpn stays well north of the cwa per fcst soundings and model q-
vector convergence fields. Model guidance suggests high temps 
reaching near 40F as morning clouds potentially erode a bit in the 
afternoon with WAA weakening.   

Mon, CAA behind cold fropa Sun night into Monday barely marginal 
enough to support isolated wnw flow LES on Monday as 850 mb temps 
lower to maybe -12C. High temps will fall back into the 30s, 
although still above normal for early March. 

Tue-Thu, a couple of weaker shortwaves move through during this time 
frame, although model timing is still rather uncertain at this 
point. There may be a period of light nw flow LES behind the last of 
these shortwaves into Thu. For now, model blend low chc pops will 
suffice with the hope that model timing/resolution improves over the 
next several runs. High temps through this period should remain 
above normal with readings generally in the 30s.

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1229 AM EST FRI FEB 28 2020

Northwest flow LES will gradually diminish with conditions improving 
to near or just above MVFR thresholds overnight as drier air filters 
into the west half of Lake Superior and Upper Michigan. Cigs near 
MVFR should then lift by Friday afternoon.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 343 AM EST FRI FEB 28 2020

NW gales and heavy freezing spray continue today over the eastern 
half of the lake, both subsiding tonight. After that, next period of 
potentially stronger winds 20-30 kts looks to be Sunday night behind 
a cold front. Winds then expected to be 20 kts or less through the 
middle of next week.

Upper Michigan...
  Winter Weather Advisory until 7 PM EST this evening for MIZ006-

  Lakeshore Flood Advisory until 4 PM EST this afternoon for 

Lake Superior...
  Heavy Freezing Spray Warning until 1 AM EST Saturday for 

  Gale Warning until 10 PM EST this evening for LSZ249>251-266-267.

  Heavy Freezing Spray Warning until 7 PM EST this evening for 

  Gale Warning until 7 PM EST this evening for LSZ243-244-264.

Lake Michigan...