Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 251200

Area Forecast Discussion
National Weather Service Marquette MI
800 AM EDT Sat Mar 25 2017

.SHORT TERM...(Today and tonight)
Issued at 514 AM EDT SAT MAR 25 2017

...Another bout of freezing rain tonight into Sun morning...

Generally quiet this morning. Upper low over central plains and
associated sfc low slowly will move toward western Illinois late
tonight. Could see some clearing in low clouds today as east low-
level winds pull in drier air with high over northern Ontario to
Quebec. Best chance of significant clearing will be over eastern
cwa closer to sfc high and due to downslope flow off Ontario. Max
temps today in the mid to upper 30s most areas. Lowest dwpnts
bottoming out around 20F over east cwa which will come into play
for ptype tonight.

Scattered rain on the northern edge of the Central Plains low will
slowly lift toward Upper Great Lakes late this aftn and more so into
this evening. Expect rain to increase in coverage and intensity as
h85 moisture transport increases/southerly h85 flow strengthens.
Upper lakes also resides within right entrance region of jet streak
over northern Ontario late tonight which will enhance the precip.
Models in decent agreement with this overall scenario. Some
difference on western extent of moderate qpf, but prefer the GEM,
GFS and EC showing heaviest qpf late tonight focusing over far east
cwa on nose of strongest moisture advection. Even though flow at h85
is strong southerly tonight allowing max wet bulb temps +4c or
higher (leading to liquid for pytpe), low level flow remains east-
northeast on flank of large high over Ontario and Quebec. Therefore,
low-levels will be dry/cold with warm air streaming in aloft.
Pattern looks favorable for freezing rain, especially over interior
east cwa closer to departing high (greater chance of lower wet bulb
temps with lower dwpnts today) and over higher terrain of ncntrl
where east wind will enhance upslope lift/cooling. Latest WPC winter
weather probabilities (consensus of various model and ensemble data)
fit this idea well with very high probabilities over 80 pct of most
cwa seeing ice accums up to 0.10 inch tonight into early Sun
morning. Highest chances of seeing 0.10 to 0.25 inch of ice (50-60
pct probabilities at this time) are focused over interior central
and east cwa. Primary freezing rain/icing hazard begins later this
evening and continues through the overnight hours.

Still a bit of time for dayshift to assess sfc temp trends today and
where heaviest rain sets up tonight as both factors will dictate
where most significant icing occurs. Thus, after coordinating with
WFOs DLH, GRB and APX, decided to let dayshift make final call on
headlines for tonight. For now, continued to mention in morning
hazardous weather outlook.

.LONG TERM...(Sunday through Friday)
Issued at 420 AM EDT SAT MAR 25 2017

Medium range model guidance continues to indicate that split flow
will dominate the CONUS/southern Canada thru the upcoming week with
pcpn over the Upper Lakes mostly tied to southern stream energy that
drops into the sw CONUS and then tracks ene across the CONUS. One
system currently getting kicked e over the Plains by the next
shortwave trof arriving over the western CONUS will weaken as it
lifts into the Great Lakes region over the next couple of days. This
will lead to an unsettled couple of days with periodic -ra and even
some -fzra at times Sun/Mon as the lead energy and trailing
shortwave trof affect the area. After a dry period midweek, a pair
of southern stream shortwaves will probably bring one or more
opportunities for 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 above normal temps across the Upper Lakes on
most days for the next 1-2 weeks. Latest CPC week 3-4 experimental
outlook (Apr 8-21) suggests a continuation of a pattern that should
favor above normal temps overall.

beginning Sun thru Mon night, mid-level low currently centered over
OK will be near St Louis Sun morning and will weaken/open up as it
moves to the Lower Lakes by Mon morning. Meanwhile, upstream trof
currently moving onshore over the western CONUS will weaken as it
reaches the western Great Lakes by Mon evening. Deep moisture
associated with the first system will return to the area tonight and
will persist until the second shortwave trof passes Mon night.
Result will be damp conditions Sun/Mon with periodic -ra. 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 850mb temps
well above 0C, allowing for the potential of more -fzra, mainly
during the night/early morning. Fortunately, forcing is weak thru
the period, so pcpn amounts should be light overall, preventing any
significant icing. Best potential of icing will be tonight into the
morning hrs on Sun as temps should fall a few degrees blo freezing
tonight over much of the area before pcpn arrives, and then only
slowly rise thru Sun morning.

Shortwave trof that reaches the western Great Lakes late Mon will
shift e of the area by Tue morning, shunting deep moisture out of
Upper MI. Hudson Bay sfc high pres will then ridge s into the Great
Lakes in association with northern stream mid level ridge shifting e
across s central Canada, supporting a return of dry weather for

Thu thru Sat, there is a plenty of model uncertainty with the GFS
moving significantly different from the ECMWF. The GFS is putting
more emphasis on northern stream energy and makes the northern
stream the more dominant influence on Upper Lakes weather, keeping
southern stream energy well s of here. The ECMWF maintains a more
influential southern stream with energy over the southern Rockies on
Tue lifting into the Great Lakes late in the week. The CMC and UKMET
lend support to the ECMWF, which has been a bit more consistent over
the last couple of runs than the GFS, and it probably represents a
somewhat better solution for late in the week. That said,
confidence, which is never particularly high in the latter part of a
7 day fcst, is quite a bit lower than typically the case. Chc pops
will cover much of the Thu-Sat time frame. While ptype will likely
be mostly rain, not out of the question that there could again be
issues with fzra. Some snow may be possible as well.

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 800 AM EDT SAT MAR 25 2017

High pressure over Ontario and Quebec and low pressure over the
plains will result in easterly winds through the period, most gusty
tonight at CMX. IFR to MVFR cigs should scatter out this aftn and
early evening at CMX and SAW, but will remain in place at IWD.
Expect cigs to lower late tonight as rain/freezing rain moves in
from the south. Cigs at all sites late tonight should drop to IFR or
LIFR. Vsby will drop to MVFR to IFR as the steadier rain/freezing
rain moves in.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 514 AM EDT SAT MAR 25 2017

No gales expected through the period as the shipping season gets
underway on Lake Superior. East to northeast winds up to 30
knots are expected today, strongest over far western portion of
the lake as winds will funnel parallel to the shoreline into
northern Wisconsin and Minnesota. Winds become east to southeast
tonight into Sun, with the strongest winds over north central to
eastern sections. Winds for the upcoming week look to remain at 20
kts or less as high pressure settles across the region.

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


LONG TERM...Rolfson
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