Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 200701

Area Forecast Discussion
National Weather Service Marquette MI
301 AM EDT Mon Mar 20 2017

.SHORT TERM...(Today and tonight)
Issued at 301 AM EDT MON MAR 20 2017

Upper air pattern consists of a 500 mb ridge across the central and
southern plains with a broad trough across central Canada skirting
the northern plains this morning. This broad trough slowly digs into
the upper Great Lakes today with a shortwave near Lake Winnipeg by
00z Tue. This shortwave moves through the area tonight. Nam shows
some deeper moisture and some 850-500 mb q-vector convergence moving
through tonight. Overall, did not make too many changes to the going
forecast. Have some chance pops in for northwest lake effect snow
belts late tonight as cold air comes in aided by some deeper
moisture and dynamics behind the shortwave.

.LONG TERM...(Monday night through Sunday)
Issued at 249 PM EDT SUN MAR 19 2017

Models suggest that a progressive pattern will prevail into next
weekend. After a brief cooldown from Tue into Wed with n-nw flow
LES, moderating conditions will follow by Thursday into Friday as a
low pressure system with widespread precipitation moves affects the
region. Temperatures will drop behind the system but should still
remain at or above normal.

Monday night through Wednesday, a shortwave trough sliding through
nrn Ontario will drag an arctic front through the nrn Great Lakes
Tuesday morning with much colder air dropping into the area on nnw
winds. 850 mb temps are expected to fall to around -18C by 00z/Wed
which will provide enough instability for LES development. However,
LES intensity will be limited by relatively low inversion heights
around 4k-5k ft with a very dry 850-700 mb layer and very dry low
level air upstream. The LES should diminish Wed morning as winds
become light and anticyclonic as the dry airmass associated with
1040 mb high pres builds into the region. Expect Snowfall amounts in
the 1 to 2 inch range per 12 hours at most and SLR values above 20/1
with DGZ through the convective cloud layer.

Thursday-Sunday, Model/ensemble spread is still relatively high with
the evolution of the cntrl plains shortwave and sfc low heading
toward the Great Lakes. The ECMWF and CMC slide the stronger 500 mb
low more to the east. There is still decent moisture transport
toward the cwa and support for pcpn with a nrn stream shrtwv and
fgen associated with the right entrance of the jet from nrn Ontario
into Quebec. This would still keep the heavier pcpn and warmer air
farther south compared to the GFS/GEFS. However, there is enough
agreement to maintain high pops for mixed pcpn that would likely
change to rain Friday as a warm layer spreads into the cwa. Some
snow or lake enhanced snow may be possible as colder air moves in
behind the system.

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 112 AM EDT MON MAR 20 2017

Low pres trof will sweep across the area overnight/this morning.
Ahead of the trof, combination of earlier pcpn and diminishing low-
level winds may allow for fog and/or low clouds to develop at KSAW.
Potential appears less likely now, but will maintain some MVFR vis
in BR at KSAW for a time this morning. With the passage of the trof,
conditions will improve quickly to VFR mid to late morning with VFR
continuing thru the remainder of the fcst period as dry air mass
dominates in the low to mid levels. At KIWD/KCMX, VFR conditions
will prevail thru the fcst period.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 301 AM EDT MON MAR 20 2017

With the cold air moving across the lake, north gales to 35 knots
are expected Tue morning across the central and eastern lake. There
could be a little freezing spray tonight into Tue morning. These
would be the strongest winds forecasted for this forecast period.

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


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