Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 290856

Area Forecast Discussion
National Weather Service Marquette MI
456 AM EDT Wed Mar 29 2017

.SHORT TERM...(Today and tonight)
Issued at 443 AM EDT WED MAR 29 2017

Confluent upper level flow in the northern stream and associated sfc
Hudson Bay high will continue to affect weather in the short term.
Upper low and developing sfc low in the southern plains this morning
will only slowly make run toward the Great Lakes next couple days.
East to northeast flow out of the sfc high and increasing moisture
in lowest 1000 ft agl and additional moistening off Lk Superior
has led to localized low clouds and fog overnight mainly over the
east and occasionally for the north central. Kept mention for
sct-bkn low clouds early on closer to Lk Superior, but still
uncertain how widespread low clouds and any fog will end up. If
low clouds increase, dry air from the high and shallow nature of
clouds/fog would still allow skies to clear out later this
morning. A lot of very high clouds upstream over MN and western WI
but trends from satellite and short range models indicate thicker
high clouds that would do a better job at dampening out the sun
and affecting high temps will not really arrive til mid to late
aftn. So, even though temps aloft are a few degrees cooler than
Tue aftn, have went with highs around warmest NAM based guidance.
Temps could reach over 50 degrees along WI border and also over
the interior east away from the weak onshore flow near the Great
Lakes shores. Coolest readings upper 30s to near 40 will be close
to Lk Superior, especially Keweenaw and north central.

Upper low and sfc lows remain well southwest of Upper Great Lakes
tonight, with upper low center along KS/MO border and sfc low only
as far east as central MO by daybreak on Thu. However, broad mid
level lift and moisture advection/isentropic ascent and enhanced
lift within right entrance of broad upper jet streak from northern
Ontario to New England should support light precip (taking mainly
the form of snow due to evaporative cooling) lifting toward Upper
Michigan late tonight. Based on soundings showing dry air with east
flow out of departing sfc high, only have pops through 12z over far
scntrl and did not go with any likely pops as dry air will still be
hampering precip coverage and intensity at that point. Ran with
temps staying a couple degrees either side of freezing over central
and east, but with clearing skies late over the west as sfc ridging
holds there and high clouds begin to shift east, went for mins in
the mid 20s which is closer to the cooler MOS guidance.

.LONG TERM...(Thursday through Tuesday)
Issued at 456 AM EDT WED MAR 29 2017

Medium range model guidance continues to indicate that split flow
will dominate for the next 7 days with the southern stream very
active. Pcpn that occurs over the Upper Lakes will largely depend on
whether any of the active southern stream systems track far enough n
to affect the area as weaker northern stream energy tracking mostly
thru southern Canada won`t produce any pcpn of note for the Upper
Lakes. The first southern stream system of interest is currently
moving out of NM into w TX. As this energy lifts ene, ejected by the
next shortwave trof dropping into the sw CONUS, some pcpn will
likely brush portions of Upper MI Thu/Thu night. As the new sw
energy moves out over the southern Plains/Lower Mississippi Valley
early next week, weaker northern stream energy will pass over or
near the area with little risk of pcpn. Heading into the middle of
next week, attention will turn to the next shortwave trof that
reaches the southern Rockies on Mon. This energy may lead to
unsettled weather here in the midweek period, which could include
wintry pcpn. As for temps, split flow will keep any really cold air
from plunging s thru Canada into the Great Lakes, resulting in temps
overall above normal thru this fcst period. Looking farther ahead,
CPC and NAEFS 8-14day outlooks valid Apr 5-11 suggest a continuation
of above normal temps.

Beginning Thu/Thu night...mid-level low lifting thru the southern
Plains today will reach the Lower Ohio Valley by Fri morning. While
quite far s, additional weak energy lifting farther n from this low
should help push isentropic ascent far enough n to spread at least
some light pcpn into southern portions of Upper MI Thu/Thu night.
However, high pres currently over Hudson Bay will be over Quebec on
Thu, providing a feed of drier air from the e which may work to hold
off pcpn. Since the high is displaced well to the ne, believe the
persistent isentropic ascent will overcome the dry air at least over
s central Upper MI and e along Lake MI. Fcst soundings support ptype
as snow. Given light intensity of snowfall and temps generally above
freezing, any snow accumulations will be light, probably not more
than around 1 inch. A few models indicate pcpn amounts upwards of
around 1/3rd of an inch in Menominee County. Seems high given the
weak forcing, but will be something to monitor in later model runs.
Elsewhere, expect mostly cloudy skies. With thinner cloud cover w,
temps may still top out well into the 40s over far western Upper MI
on Thu while the -sn is occurring over the s central.

Fri/Sat...a couple of northern stream shortwaves will track across
northern Ontario and the Upper Lakes. With first shortwave on Fri
passing well to the n of here, not expecing any pcpn. In the wake of
that shortwave, sfc high pres ridge will build into the western
Great Lakes for Sat even though second shortwave approaches. Weak
forcing suggests very little risk of pcpn on Sat either, so fcst
will reflect dry weather Fri and Sat. Steady n to ne wind on Fri
will lead to a cool day, especially near Lake Superior. Increasing
sunshine from the w will allow temps to rise into the 40s in the
interior w half. Will still be cool near Lake Superior on Sat but
with lighter gradient winds across the lake, temps will be higher
than Fri. Well inland, temps should reach 50F or higher.

Another northern stream shortwave will reach northern Ontario late
Sun. Better forcing and waa/isentropic ascent will pass n of here,
so again not expecting any pcpn. With winds veering around to a
southerly direction, it will be warmer near Lake Superior on Sun.
Warmest conditions will be over the w where temps should reach the
mid 50s.

Mon thru southern stream shortwave should pass well s and
se of here Mon/Tue with attention turning to the next one that will
be over the southern Rockies. This system may interact with the next
upstream shortwave that will track farther e into N America before
dropping se (rather than dropping into the sw CONUS per previous
waves), a result of an amplifying trof developing over the ne
Pacific. The 00z ECMWF has backed off on interaction that led to a
potentially significant snow for portions of Upper MI on Tue as
shown by the 12z run. However, 00z CMC ensembles show a few more
members than the 12z run supporting a potentially wrapped up Great
Lakes storm system midweek. Will be something to monitor in the
coming days, but for now, nothing supports more than some chc pops
in this period with ptype mainly rain.

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 137 AM EDT WED MAR 29 2017

Expect VFR conditions and light winds to prevail at IWD through the
forecast period. However, shallow low level moisture over Lake
Superior could lead to stratus/IFR conditions tonight at CMX and SAW
under light upslope e to ne winds. Although confidence is still
limited, since satellite has has showed progress of fog/stratus
toward n cntrl Upper Michigan from Lake Superior, opted to mention a
period of bkn IFR cigs and some MVFR fog late tonight into early
Wednesday for SAW but just go with scattered clouds at CMX. Will
continue to monitor and update as needed. Any fog and low clds will
burn off by late morning.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 443 AM EDT WED MAR 29 2017

No gales expected as first week of the 2017 shipping season
continues on Lk Superior. Winds into Thursday may reach 25 kts,
especially with enhanced NE winds over far western Lk Superior and
with stronger SE winds over eastern and north central Lk Superior on
Thu as pressure gradient tightens between large high over eastern
Canada and low pressure system crossing the Ohio Valley. Winds
diminish by Fri though and will remain at 20 kts or less through
next Monday as pressure gradient diminishes.

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


LONG TERM...Rolfson
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