Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 182040
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
440 PM EDT Sat Mar 18 2017

.SHORT TERM...(This evening through Sunday)
Issued at 359 PM EDT SAT MAR 18 2017

Primary upper trough is well by the area over the lower Great Lakes,
but sfc low pressure trough is lingering from lower great lakes to
eastern Lk Superior. Low-level moisture extends to about 4kft agl
which is borderline for getting to -8c to -10c so there have been
snow showers today mainly in nw flow areas along Lk Superior but
also some drizzle. In last couple hours, low-level drying has
generally resulted in more snow than dz and that will probably
continue to be the trend into the evening. Any light precip should
end overnight, departing last over east cntrl cwa. Low clouds may
diminish overnight over west as winds become variable then south.
Interior west may see lows drop to mid teens before increasing mid
clouds late. Mid clouds continue to spread over rest of cwa on Sun,
though warming in low-levels may allow max temps to still reach well
into the 40s over west and cntrl. S winds off Lk Michigan will keep
eastern cwa in upper 30s to around 40 for max temps. Warm front
moving in late aftn along with steeper lapse rates and moisture
advection 925mb-700mb could support showers developing over west
cwa. Better chances of showers will move in on Sun night.

.LONG TERM...(Sunday night through Saturday)
Issued at 439 PM EDT SAT MAR 18 2017

After warming this weekend as a ridge shifts e into the Great Lakes
region, a trof will amplify into se Canada/ne CONUS Mon-Wed,
bringing a period of colder weather as the Upper Great Lakes are
brushed by a late season arctic air mass that will bring very cold
conditions to Quebec where 850mb temps will drop to sub -30C. Temps
will then moderate to around normal during the last half of the week
as ridging shifts to the eastern CONUS and arctic branch retreats n.
As for pcpn, a pair of shortwaves and associated cold fronts will
bring the colder conditions during the early part of next week,
though pcpn will be light. Pcpn with first fropa Sun night will
likely be just -shra. Second fropa may be accompanied by sct -shsn
Mon night with sct light LES to follow Tue into early Wed as 850mb
temps fall to -15 to -20C. Late week, attention will shift to
shortwave energy swinging thru the sw CONUS. Snow or mixed pcpn
could arrive as early as Thu as weak lead energy lifts ne toward the
Great Lakes. Main shortwave then arrives in the western Great
Lakes/lwr Ohio Valley on Sat, probably with more mixed of pcpn. At
this point, it does not look like a strong, wrapped up system.
Looking farther ahead, CPC/NAEFS outlooks in the 8-14 day period
(Mar 25-31) indicate temps probably not far from late Mar normals.
Into early Apr, recent days CFSv2 ensemble means have been
suggesting a preference for above normal temps across the Upper
Lakes.

Beginning Sun night/Mon, a vigorous shortwave trof will swing into
northern Ontario with associated cold front sweeping across Upper MI
roughly in the late Sun evening to early Mon morning time frame. Out
ahead of the front, a minor shortwave and a narrow axis of
instability are indicated by most models, potentially a few hundred
j/kg of elevated cape. Along with steep mid level lapse rates
upwards of around 7.5c/km and 40kt low-level jet, a narrow band of
isold to sct -shra may push across the area, and not out of the
question that there could be a few rumbles of thunder. Stong low and
mid level drying follows fropa into Mon though the NAM in particular
suggests some low clouds may occur for a short time after fropa.
Otherwise, with high clouds departing, expect a trend to sunny skies
on Mon which will aid temps rising into the 40s, and even lwr 50s s
central. Close to Lake Superior where w to nw winds have
trajectories across the lake, temps will be lower. Second cold front
then drops s across the area Mon night. With moisture limited, not
expecting much more than sct -shsn, especially closer to Lake
Superior.

Incoming dry air mass and increasingly anticyclonic flow as
influence of high pres over Manitoba expands into the Upper Lakes
will be strong negatives for LES on Tue despite 850mb temps falling
to -15 to 18c. Stronger mid/late Mar daytime heating will also
disrupt LES processes. Expect sct -shsn, mainly off the e half of
Lake Superior due to longer fetch and the lower 850mb temps in that
area. High temps Tue will range from roughly the upper 20s to
around 40F, warmest s central.

Light LES will linger Tue night, mainly off eastern Lake Superior,
before ending by Wed aftn as high pres moves over the Upper Lakes.
Expect min temps Tue night into the single digits/teens with max
temps on Wed into the mid 20s/30s.

Late week, as mentioned above, shortwave energy swinging across the
sw CONUS will move toward the Great Lakes/Ohio Valley. 00z ECMWF/CMC
were in fairly good agreement on late week evolution with both being
slower and more consolidated/farther s with the main energy in the
trof than the GFS. Unfortunately, the 12z ECMWF trended farther s
with the main energy, far enough s that most, if not all, of the
pcpn will stay s of the fcst area after some pcpn with lead weak
shortwave Thu/Thu night. Since bulk of Canadian ensembles still
support something more along the lines of the 00z ECMWF, fcst will
still retain high pops in the late week period. While likely not
becoming a well developed, wrapped up storm system, there certainly
could be decent pcpn amounts spreading well n into the Great Lakes
given a good tap of gulf moisture. At some point, cooling may become
sufficient to change rain and/or mixed pcpn to all snow as well.
Cooling will be determined to some degree by track/speed of arctic
branch shortwave dropping across Hudson Bay as following arctic high
pres building toward northern Ontario would provide a feed of
colder/drier air into the area at the lower levels.
&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 204 PM EDT SAT MAR 18 2017

At IWD and CMX, conditions are beginning to improve (cigs lifting
toward MVFR and vsby at times up to 10sm) as dry air works over
western Upper Michigan from the west. Expect IWD to continue to
improve to VFR conditions by this evening with just mid clouds later
tonight into Sun morning. At CMX, cigs will remain around 010 into
tonight with lingering moist layer trapped below subsidence
inversion and since winds stay off of Lk Superior. Lo cigs should
scatter out late tonight or Sun morning with broken mid clouds
moving across.

For SAW, NW-N winds off Lk Superior will continue IFR cigs and a
light mix of dz and sn into this evening with light snow showers
then lingering there through much of the night. Low clouds should
finally break out Sun morning though with S-SE winds developing off
Lk Michigan the low clouds may be slower to depart.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 359 PM EDT SAT MAR 18 2017

Winds through the period look to stay 30 kts or less. Strongest
winds will be late Mon into Tue as cold air moves back across Lk
Superior. At this time, no gales or heavy freezing spray is
expected into next week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...JLA
LONG TERM...Rolfson
AVIATION...JLA
MARINE...JLA



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