Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 300541
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
141 AM EDT Thu Mar 30 2017

.SHORT TERM...(This evening through Thursday)
Issued at 247 PM EDT WED MAR 29 2017

12Z raobs/latest wv imagery and RAP analysis show a split flow
dominating NAmerica, with upr rdging in both the nrn and srn streams
supporting Hudson Bay hi pres centered over nw Ontario extending a
sfc rdg axis into the wrn Great Lks. Despite the presence of this
rdg axis over Upr MI and some dry llvl air shown on the local 12Z
raobs, quite a bit of hi cld streaming to the ne fm closed srn
branch lo over the srn Plains has overspread the area as winds
aloft shift to the sw ahead of a nrn branch disturbance near the
Cndn border moving e thru the Plains. Pcpn on the ne flank of the
srn branch closed lo has moved as far n as far srn MN/sw WI.

Main fcst concerns in the short term focus on how far n pcpn
associated with the srn branch disturbance wl move late tngt/Thu.

Tngt...The srn branch closed lo is progged to move slowly to the ne,
reaching ern Kansas/wrn Missouri by 12Z Thu while the nrn branch
shrtwv/accompanyin dpva lift ne toward the border of Manitoba/far nw
Ontario. While most of the Upr Lks wl remain under an axis of drier
lo/mid lvl air and larger scale h85-5 qvector dvgc btwn these
disturbances, some hier h85-5 rh on the nrn fringes of the mstr
shield ahead of the srn branch disturbance is fcst to impact the
scentral cwa. But since the dry llvl feed of air out of the slowing
departing Hudson Bay hi pres is fcst to persist, the bulk of the
hier res models show pcpn in the form of sn reaching just s of the
city of Menominee by 12Z Thu. Wl retain some lo chc pops only over
far srn Menominee County toward 12Z. Otrw, the combination of
thickening hi/mid clds and a steady e wind wl limit the diurnal temp
fall.

Thu...The short term guidance shows the closed lo moving to near St
Louis by 00Z Fri, with hier mid lvl mstr influencing the se 1/3 or
so of the cwa on the nrn fringes of area of upr dvgc in rrq of h3
jet max within the confluence zone of the separate branch flows. The
rest of the cwa wl remain under the axis of deep lyr qvector dvgc
btwn the larger scale srn branch forcing influencing WI/Lower MI and
the nrn branch disturbance tracking toward Hudson Bay and remain
dry. Expect a sharp gradient of pops over the scentral, where an
upslope e wind may at least minimize the influence of the llvl
drying associated with the slowly departing Hudson Bay hi pres, as
indicated by the 12Z NAM model. Given the pattern featuring a Hudson
Bay hi pres that favors dry wx for Upr MI, tended toward the drier
scenrios for pops fcst. Although the fcst thermal profiles indicate
this pcpn wl fall mainly as sn, the incrsg late March sun angle that
allows sfc temps to rise at least a couple degrees above 32 wl limit
sn accum potential.

.LONG TERM...(Thursday night through Wednesday)
Issued at 256 PM EDT WED MAR 29 2017

The extended looks to be fairly quiet overall with the main focus on
low pressure sliding to the south of the U.P. Thursday night and
another low pressure trough/disturbance sliding across the area
Saturday into Saturday night. Another scattered precipitation event
is possible for early next week, Tuesday into Wednesday. Otherwise,
expect above normal temperatures through the extended with highs in
the 40s to around 50 and overnight lows in the mid to upper 20s.

Thursday night: An area of low pressure sliding across the mid
Mississippi Valley is progged to lift slowly through the Ohio River
Valley through this time period. At the same time, a Hudson Bay high
pressure system will remain nearly stationary or slide very slowly
off to the east. The northern fringes of the moisture associated
with the low will try to work into the U.P.; however, the northward
extent is expected to be limited as the flow around the high
pressure system will be very dry. The easterly winds will steadily
pump dry air in to offset the approaching moisture. At this point,
will continue pushing the pops down across the south central U.P.
and east along Lake Michigan. If precipitation does occur, it will
mostly likely be in the form of light snow or rain/snow mix. Most of
the sounding looks to be below freezing with some ice crystals in
the layer; however, the lower levels are fairly dry at least through
Thursday evening. The rest of the area is only expected to see an
increase in cloud cover through this time period.

Friday through Saturday night: Drier air and a weak ridge will slide
through the area Friday into Friday night allowing for mostly clear
skies across the U.P. The next chance of maybe a few sprinkles will
be Saturday through Saturday night as a quick moving upper-level
shortwave trough slides through the area. At this point, not
expecting much in the way of precip as moisture will be limited. The
best chance of seeing the sprinles will be over the north half and
over Lake Superior.

Monday night through Wednesday: Several disturbances are progged to
slide near or through the Upper Great Lake region, giving a period
of unsettled weather. This would bring at least intermittent chances
of precipitation to the area and/or increased cloud cover through
this time period. There has been a lot of variance in the models for
this time period, as expected with it being toward the end of the
forecast period. The latest EC/Canadian have most of the area dry
through this time period, while the GFS, as the outlier, tries to
bring a system northward along with scattered rain showers. At this
point, will continue to stick with a blend of the models, painting
only marginal chance of precipitation across the area, mainly for
Tuesday into Wednesday. Stay tuned as there is still plenty of
variability in the models.
&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 140 AM EDT THU MAR 30 2017

This fcst period wl be dominated by a good deal of high clds that wl
tend to thicken with time at SAW and likely lower Thu afternoon to
low end VFR and then MVFR by Thu evening. Since the low pressure
system responsible for the clds wl remain well to the s of Upr MI,
pcpn and thus lower vsbys wl tend to remain s of the TAF sites as
well. Maybe some sprinkles could be possible at SAW late Thu
afternoon/evening.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 247 PM EDT WED MAR 29 2017

Ene winds up to 20 to 25 kts will be possible tonight into Fri under
the sharper pres gradient between slowly deparing Hudson Bay hi pres
and a slow moving lo pres that will be drifting from the southern
Plains toward the Lower Great Lakes. Winds for later Fri thru Mon
will be under 20 kts as a weaker pres gradient becomes established
across the western Great Lakes.
&&

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

$$

SHORT TERM...KC
LONG TERM...KEC
AVIATION...Voss
MARINE...KC


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