Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 190004

Area Forecast Discussion
National Weather Service Marquette MI
804 PM EDT Wed Apr 18 2018

.SHORT TERM...(This evening through Thursday)
Issued at 309 PM EDT WED APR 18 2018

Clouds have been quick to clear this afternoon as a very dry airmass
advects into the area. Gusty winds of 15-25 kts have developed in
response to the pressure gradient from the high/low in western
Ontario/southern Great Lakes. Winds are expected to relax this evening
except across the far east as temperatures drop to the 20s. A shallow
layer of clouds is expected to redevelop along the north central Lake
Superior shore this evening but the dry low-level airmass, relative
shallow depth of the cloud deck, and little mechanical mixing atop the
cloud top should prevent any freezing drizzle.

Thursday looks quite splendid with mostly sunny skies and highs in the
40s top near 50 along the Wisconsin border.

.LONG TERM...(Thursday night through Wednesday)
Issued at 302 PM EDT WED APR 18 2018

An extended period of quiet weather is shaping up for the Upper
Lakes with temperatures returning to more typical mid/late April
values. The quiet weather will be ideal for allowing a more gradual
runoff of the melting snowpack under warmer conditions and high
spring sun angle. A warming trend will be underway thru the upcoming
weekend with the expected development of positive height anomalies
across s central Canada ensuring no buildup of late season cold air
to the n. Looks like a steady warmup with snow cover not really
inhibiting warming given the high sun angle working on the forested
Upper MI landscape on mostly sunny days.

There are no major weather concerns for this fcst cycle. Mean
mid/upper level ridging over s central Canada to Hudson Bay will
support sfc high pres over the Upper Mississippi Valley on Thu and
then over the Great Lakes region Fri thru Sun, resulting in dry
weather. The GFS remains the model outlier printing out some light
pcpn Fri aftn and Sat aftn in central counties along the lake breeze
convergence zone, a result of too much low-level moisture from
melting snow. This has been a bias seen in the model in recent
weeks. Outside of some high clouds at times, generally sunny days
and clear nights are expected, a fairly typical spring time scenario
for Upper MI. Winds will be on the light side Fri thru Sun with high
pres over the Great Lakes region and meso highs setting up each
afternoon over the waters, particularly Fri/Sat, leading to lake
breezes and cooler temps near the Great Lakes each aftn (temps in
the 30s near the shores). Gradient nw wind on Thu ahead of the
approaching sfc high will spread cooling from Lake Superior well
inland. Away from lake cooling, high temps will be in the mid/upper
40s Thu and the 50s Fri thru Sun. Wouldn`t be surprised to see some
locations reach near 60F Sat/Sun. Best chance of seeing more
widespread max temps at or above 60F will be on Mon with sw waa flow
ahead of approaching cold front. With good radiational cooling
nights coming up will continue to favor the bias corrected global
CMC for mins as it is typically a superior performer on such nights.
Dry air mass and little cloud cover will support large diurnal temps
swings, especially while snow cover is still consistent across the
landscape. Interior mins should fall to the teens Thu night, around
20F Fri night and low/mid 20s Sat night. Will also side on the lower
end of model dewpoint guidance into the upcoming weekend.

The GFS and ECMWF still advertise a cold frontal passage Mon night
or Tue. However, nothing more than schc/chc pops are warranted as a
southern stream system moving from the Lower Mississippi Valley to
the SE States will effectively block Gulf moisture return. Might see
some -shra/-shsn on Wed under mid-level trough passage.

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 741 PM EDT WED APR 18 2018

Low pressure system currently traversing out of IA along the WI/IL
border is the reason for the more extensive cloud cover across the
southern two-thirds of the Upper Peninsula. However, high pressure
to the north and associated drier air is sinking southward into
the northern portions of the U.P., allowing for the cloud cover to
not be as extensive. That said, look for VFR conditions to prevail
tonight with some lowered ceilings possible at KSAW around dawn.
Generally northerly winds will dominate through this TAF period.


.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 309 PM EDT WED APR 18 2018

Winds will remain between 20 to 30 knots through Thursday morning.
A few gale force gusts to 35 knots can`t be ruled out across the
eastern half of Lake Superior this afternoon. Winds will then
relax below 20 knots from west to east on Thursday, remaining
relatively calm through the weekend.

Issued at 302 PM EDT WED APR 18 2018

Snowpack will begin to melt in the coming days as a warming trend
gets underway with temps rising to around normal under mostly sunny
days. With nighttime temps falling blo freezing and dewpoints likely
low, ripening of snowpack will be slow, leading to a gradual
melting/runoff. Early next week, min temps may not fall blo freezing
for a night or two, increasing runoff potential, though dewpoints
will likely remain low, keeping melting of snow slower than would
otherwise occur. The addition of notable rainfall would be the
biggest concern to increase flooding potential. Fortunately, there
will be no pcpn thru the weekend and only a small chc of light pcpn
early next week when a cold front passes. The following temporary
cool down will then slow down the snow melt. Overall, these
conditions don`t suggest any significant concerns with the snow melt
over the next 7 days. While melting will likely be relatively
controlled given the forecast, rivers will begin to respond this
weekend and minor flooding is quite possible at some point down the
road on the usual rivers that experience spring flooding.

Upper Michigan...
Lake Superior...
Lake Michigan...


SHORT TERM...Borchardt
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