Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 241739

Area Forecast Discussion
National Weather Service Marquette MI
139 PM EDT Fri Mar 24 2017

.SHORT TERM...(Today and tonight)
Issued at 512 AM EDT FRI MAR 24 2017

WV loop and RAP analysis indicates WSW flow aloft downstream of
upper low over the southern Rockies. Feed of deep moisture, warm
air advection and stronger shortwave resulted in widespread light
to moderate rain and freezing rain Thu evening til early this
morning. Treated roads stayed wet but untreated roads and other
surfaces such as parking lots and sidewalks became very icy as of
early this morning.

Another batch of rain and freezing rain tied to h85-h7
frontogenesis, steeper mid-level lapse rates and persistent warm air
advection aloft is currently lifting across mostly cntrl Upper
Michigan, running btwn Marquette and Iron Mountain/Escanaba though
additional rain and isold tsra developing northeast of Twin Cities
should clip Iron Mtn and Escanaba in the next few hours. Overall
current radar and high res short term models suggest that areas
south of line from Watersmeet to Marquette will see the heavier
rain/freezing rain through the morning though west and northwest cwa
could still see some drizzle/freezing drizzle. Have seen a few
lightning strikes far scntrl and could see a few more in those same
areas this morning. Temps most areas are within two degrees of
freezing mark and since sfc warm front is well to southwest (only
progged to enter southern WI by 12z this morning) sfc temps will
only slowly warm through the morning and the icing hazard will stay
in place. Current winter wx advy going through 15z looks good as
after that point precip diminishes and temps warm into the mid to
upper 30s.

For tonight, appears that northern edge of light precip sliding
along and north of warm front lifting across cntrl Great Lakes could
affect far scntrl and southeast cwa. Otherwise models have trended
toward drier forecast with confluent flow aloft which leads to more
influence from strong high pressure building across northern
Ontario. East winds and moist layer blo h9 as shown by NAM, GFS and
GEM could result in light drizzle/freezing drizzle for upslope areas
of Keweenaw and north central cwa. Intensity should be pretty light
though, especially compared to precip seen over cwa since Thu
evening. With plenty of cloud cover and limited cold air temps
will only bottom out in the upper 20s to lower 30s.

.LONG TERM...(Saturday through Thursday)
Issued at 428 AM EDT FRI MAR 24 2017

Split flow will dominate the CONUS/southern Canada thru the upcoming
week with pcpn largely tied to southern stream energy that drops
into the sw CONUS and then tracks ene across the CONUS. One system
emerging over the western Plains today will weaken as it is kicked
ne to the Great Lakes early next week by the next shortwave trof
reaching the western CONUS. This will lead to rain and some fzra at
times Sat night thru Mon as the lead and trailing shortwave trof
affect the area. After a drier period midweek, a pair of southern
stream shortwaves may bring more pcpn late next week/weekend.
Overall, it appears pcpn amounts will generally be on the lighter
side. As for temps, split flow across N America will keep arctic air
bottled up way to the n, resulting in overall above normal temps
across the Upper Lakes for the next 1-2 weeks.

Beginning Sat, strong sfc high pres building across northern Ontario
today/tonight will become centered near James Bay by Sat evening.
Dry air emanating from this high will suppress pcpn associated with
warm front extending into the Lower Lakes from southern stream mid-
level low that will reach MO. However, there is a push of moisture
and weak isentropic ascent from the s during the aftn which may aid
a northward advancement of -ra into southern Upper MI during the
aftn. Prior to that, despite the strong sfc high pres passing by to
the n, which would normally suggest significant low-level drying,
fcst soundings show considerable low-level moisture blo about 4kft,
especially over roughly the w half of Upper MI, farther from the
departing sfc high. Not out of the question that there could be some
-dz/-fzdz during the morning where low-level easterly flow upslopes.

Sat ngt thru Mon ngt, mid-level low over MO Sat evening is fcst to
open up/weaken as it lifts across Lower MI to southern Ontario and
the Lower Lakes. This occurs in response to upstream shortwave trof
moving across the Plains Sun and reaching the Mississippi Valley
late Mon. As a result, deep moisture will expand across the area
with all model guidance indicating periodic pcpn. The main fcst
challenge is that the low-level flow will remain easterly thru Sun
before backing northerly into Mon. This will act to maintain some
colder near sfc air blo an elevated warm layer with h85 temps above
0C, allowing the potential of more -fzra, mainly at night.
Fortunately, forcing is weak, so pcpn amounts should be light
overall, and there should not be any significant icing.

With shortwave trof over the Mississippi Valley late Mon shifting e
of the area by Tue morning, expect dry weather to return for Tue/Wed
as Hudson Bay sfc high pres builds into the Upper Great Lakes.

Wed night/Thu, there is uncertainty on the the strength/track of a
northern stream shortwave running roughly along the U.S./Canadian
border. 00Z ECMWF has significantly backed off on the strength of
this wave, and now does not generate any pcpn. 00Z CMC still
maintains a stronger wave with pcpn while the 00Z GFS is similar to
the ECMWF. With some weighting from previous model runs, fcst will
reflect a chc of pcpn Wed night into Thu.

Late week, at least one batch of southern stream energy may make a
run toward the Great Lakes, but there is little model agreement or
consistency at this point.

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 138 PM EDT FRI MAR 24 2017

Conditions this afternoon vary from MVFR to LIFR, with KIWD
continuing to see the lowest ceilings and visibilities as onshore
flow continues out of the northwest. Further north, winds have veer
around more northerly and has allowed the better upslope flow to
weaken. Across KSAW, the combination of moist onshore and upslope
flow out of the north has allowed the IFR ceilings and visibilities
to remain in place. Tonight, expect the lower ceilings to linger at
KSAW and KCMX with winds veering around to the east-northeast
providing good onshore/upslope flow. Soundings suggest enough low-
level lift and saturation will take place at KCMX for some light
snow, and possibly some light freezing drizzle, to develop later
tonight. Soundings show that cloud top temperatures may be just cold
enough to support snow rather than freezing drizzle, so opted to
just mention light snow for now. We may see a brief increase in
visibilities at KSAW later this afternoon, but expect the lower
visibilities to return with upslope flow developing overnight. As
winds veer to the east-northeast, KIWD will see improving conditions
as downsloping flow should allow ceilings to rise gradually to the
MVFR category.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 559 AM EDT FRI MAR 24 2017

Light winds to begin the day will become N to NE and increase to 20
to 30 kts late today through Tonight as high pressure builds across
northern Ontario and low pressure over the Plains extends a trough
to the central Great Lakes. E winds 20 to 30 kts will continue on
Sat then diminish to 20 kts or less Sun and into early next week as
pressure gradient weakens.

Upper Michigan...
  Winter Weather Advisory until 2 PM EDT this afternoon for MIZ006-

Lake Superior...
Lake Michigan...


LONG TERM...Rolfson
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