Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 250547

Area Forecast Discussion
National Weather Service Marquette MI
147 AM EDT Thu May 25 2017

.SHORT TERM...(This evening through Thursday)
Issued at 325 PM EDT WED MAY 24 2017

No major weather impacts expected through the short-term portion of
the forecast.

Tonight through Thursday: No major changes in the forecast through
this time period. Upper-level troughing across much of the Great
Lakes will slowly sag to the south through this time period as a
surface low remains nearly stationary over much of the Ohio River
Valley. The main impact that this will have on the U.P. weather will
be continue wrap-around moisture sliding across mainly the eastern
half of the area through tonight and early Thursday. The west half
will likely see clouds begin to slowly break tonight into Thursday
as drier high pressure begins to very slowly slide into the western
U.P., especially aloft. This may result in some fog development
overnight, depending largly on how quickly the cloud cover
diminishes. Dewpoints are expected to remain in the upper 30s to
near 40, which should keep enough moisture near the surface for at
least some fog potential. As the moisture axis slides farther east
during the day Thursday, the sun may actually break out for the
afternoon hours with the drier air moving in with the high pressure
system. If that does happen, temperatures will quickly warm into the
upper 60s to around 70 over the west half as 850mb temperatures are
progged to be around 10C. The east half may be a bit cooler with a
little more lingering moisture, thanks to a quick moving shortwave
sliding just east of that area.

.LONG TERM...(Thursday night through Wednesday)
Issued at 325 PM EDT WED MAY 24 2017

Although there may be some dry times, a slow moving closed upr lo
within a mean upr trof that wl dominate the Great Lks this coming
week wl bring above normal precip to Upr MI this fcst period. Fri
and Sat wl likely feature aoa normal temps, but then cooler wx wl
prevail later in the weekend into mid next week as the closed lo/
deep upr trof dominate.

Thu ngt into Sat...A shrtwv rdg/sfc hi pres wl bring dry wx to
the cwa thru at least Thu evng before the rdg axis passes slowly to
the e and some waa ahead of an aprchg cold fnt attendant to the slow
moving lo pres in scentral Canada brings more clds and at least a
chc of showers to the wrn cwa as early as late Thu ngt. Since the
closed lo wl remain nearly stnry close to Lk Winnipeg, the area of
waa/axis of qvector cnvgc ahead of the slow moving fnt are fcst to
drift only slowly thru the Upr Lks on Fri/Fri ngt, prolonging the
chc for showers. H85 temps up to 10C on Fri in waa pattern ahead of
the aprchg fnt wl allow temps to rise aoa 70 away fm the cooling
influence of mainly Lk MI. Although most of the medium range
guidance shows the fnt passing the ern cwa by 12Z Sat with the
arrival of weak sfc rdging/dry slotting ending the pcpn, some of the
slower guidance indicates a later fropa with shower chcs lingering
over mainly the e half thru at least part of Sat. Coonsidering the
sluggish closed lo near Lk Winnipeg, this slower scenario is
possible. Given the uncertainty, did not change the consensus fcst.
Because the airmass following the fropa on Sat wl not be a cool one
with h85 temps near 10C, highs on Sat should exceed 70 at some
places over the scentral with a downsloping w wind.

Sat ngt into Tue...While most of the longer range guidance indicates
the closed lo wl drift slowly to the se and near the Upr Lks during
this period, there are disagreements on the timing of not only the
main feature but also on other weaker shrtwvs rotating thru the deep
cyc flow and the impact on the mslp field. A few of the extended
models have hinted a deeper sfc lo may dvlp over the lower Great Lks
on Sun and drift nwd just to the e of the cwa on Mon in the sly flow
alf ahead of the aprchg closed lo. This scenario would result in a
more wdsprd rain and stronger cyc nly flow/very cool daytime temps.
On the other hand, the guidance that shows a less developed sfc lo
pres would support a more sct, diurnal heating driven shower
pattern. The 12Z models have trended toward the fcst of a weaker sfc
lo pres. Although the details are still far from certain at this
point, the wx during the second half of the upcoming Holiday weekend
may not be ideal for outdoor activities.

Tue/Wed...Depending on the intensity of the sfc lo and how quickly
the closed lo/cyc nw flow in its wake exit to the ne, some drying
may return as early as Tue. But the models that show a slower,
deeper sfc lo indicate drying ahead of trailing sfc hi pres may not
arrive until sometime on Wed. If the sfc hi pres arrives by Wed
under the faster scenario, more sunshine wl allow for a warmer day
with h85 temps rebounding toward 10C.

That`s it...signing off!

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 143 AM EDT THU MAY 25 2017

Shallow radiational fog will likely affect KIWD at times thru the
night. While prevailing MVFR vis is expected, conditions may vary
from VFR to IFR and to potentially as low as LIFR. VFR conditions
will return soon after sunrise and continue thru the rest of the
fcst period. At KCMX, VFR conditions will prevail thru the fcst
period. At KSAW, VFR conditions should prevail thru the fcst period.
However, if clouds happen to clear out overnight, fog may develop at
KSAW, dropping vis to IFR or even LIFR. Winds thru the period will
be under 10kt at all terminals.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 325 PM EDT WED MAY 24 2017

Expect winds under 20 kts at least into the weekend as a relatively
flat pres gradient dominates the Upper Lakes through that time. If a
deeper lo pres develops over Lower MI on Sun/Mon, a stronger n-ne
flow is possible later in the forecast period.

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


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