Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 200926
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
526 AM EDT TUE SEP 20 2016

.SHORT TERM...(Today and tonight)
Issued at 525 AM EDT TUE SEP 20 2016

WV imagery and RAP analysis indicated a mainly zonal pattern across
the northern CONUS/Southern Canada with a 130 knot 250-300 mb
jet from the Northern Rockies into the Upper Great Lakes.  A
shortwave upstream was producing a cluster of storms over the ND/SD
border along MUCAPE gradient approaching 1000 j/kg, steep mid-lvl
lapse rates and at nose of fairly strong 850 mb moisture transport.
Over the Upper Great Lakes broad sfc high pressure has resulted in
generally cloud-free skies early this morning. Early morning temps
have fallen into the 40s over the interior west half and into the
50s east half and along the Great Lakes shores.

Today, a dry airmass will prevail with sfc ridging in place over the
region. Under mostly sunny skies through most of the day temps will
remain above normal with forecast soundings supporting highs in the
mid 70s and perhaps even higher in a few spots. Mid and high clouds
will gradually spread into the area from the west during the afternoon
with a waa pattern developing in advance of a trough over the plains.

Tonight, Waa continues tonight with a northward push of 850 mb warm
frontal boundary into Northern Wi and expect clouds to increase into
Upper Mi. Models suggest convection could initiate along warm frontal
boundary over Nrn Wi with hint of a weak shortwave moving through the
area. Will include some slight chc pops for showers late tonight far
south central in case convection over Northern Wi brushes Wi Border
counties.

.LONG TERM...(Wednesday through Monday)
Issued at 432 AM EDT TUE SEP 20 2016

An increasingly amplified pattern will be developing across N
America for the remainder of this week. Ridge/positive height
anomaly currently moving across the Gulf of Alaska will strengthen
as it shifts across the Northwest Territories to Nunavut by the end
of the week. The magnitude of the positive height anomaly at 500mb
will reach 3 standard deviations above the long term late Sept avg.
To the s of this anomaly, a trof will amplify over the western CONUS
this week. Ahead of this developing western trof, shortwave energy
in the vcnty of southern CA will be kicked ne, reaching the western
Great Lakes Wed evening. This energy will bring the next opportunity
of widespread pcpn Wed into Thu. What happens late week and thru the
weekend continues to be uncertain. One aspect that has generally
been favored in the last day or so is for increased se Canada
troffing late week, which seems reasonable based on the strength of
the north central Canada positive height anomaly and based on this
anomaly linking up with the ridging farther s ahead of the western
CONUS trof. This argues for a drier period late week as sfc high
pres associated with the sharp ridge builds se into northern Ontario
and the Upper Great Lakes. Until that happens, right entrance of the
upper jet associated with the se Canada trof may continue to support
some shra into Fri. Over the weekend into early next week, attention
turns to the fate of the western CONUS trof. As CMC/GFS ensembles
and some operational medium range models began to show a day or so
ago, guidance is overall converging toward the solution of dropping
much of the energy in the western trof into the sw CONUS. Building
heights to the n of this feature will weaken/shift the mid continent
ridge e as a shortwave is forced se into the Upper Lakes late
Sun/Mon downstream of the building heights over the w. This will
provide the next good chc of shra. As for temps, after the recent
warmth, readings will be trending back to normal or a little blo
normal this week as fcst area ends up under low-level ne to e winds
btwn frontal boundary to the s and high pres building toward
northern Ontario. Coolest conditions may end up occurring early next
week behind the shortwave pushing thru the area late Sun/Mon.

Wed-Fri...shortwave energy lifting ne from the sw states ahead of
the deepening western CONUS trof will result in sfc frontal boundary
settting up from the Plains across the Great Lakes with weak low
pres waves rippling along it. Combination of shortwave energy, upper
divergence from right entrance of 120kt upper jet across northern
Ontario into Quebec, frontal boundary and precipitable water
increasing to around 1.25 inches will support pcpn development
across the Upper Mississippi Valley and Upper Great Lakes Wed into
Thu. Given avbl moisture, mdt/hvy rainfall is a possibility. Better
chc of the heavy rainfall will be s of the fcst area in WI, closer
to frontal boundary, but southern Upper MI could certainly see some
heavier rainfall at times. While 00z guidance has mostly trended
slower to push pcpn s of the area Thu into Fri, fcst will maintain
closer continuity to previous fcst in trending drier later Thu into
Fri. Pops will drop to low chc across the s into Fri while the n
trends to dry weather. Proximity of the right entrance of 120kt
upper jet leads to low confidence for the drying trend, but
eventually, sharp ridge thru central N America will support sfc high
pres building into the Upper Great Lakes, pushing pcpn s and w of
the fcst area.

Heading into Sat, the ECMWF is most aggressive with right entrance
of upper jet aiding renewed pcpn development back into Upper MI. For
now, confined chc pops to western Upper MI, in better aggreement
with the GFS/CMC.

Models show poor continuity in timing of the shortwave that reaches
the Upper Lakes early next week. Due to the inconsistencies, a
consensus of recent runs was utilized, resulting in chc pops
spreading across the area Sun/Sun night and lingering over the e on
Mon.
&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 140 AM EDT TUE SEP 20 2016

Expect VFR conditions at all taf sites through the period. West winds
will gust from 20-25 knots by late Tue morning into late afternoon,
strongest over the more exposed CMX site.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 525 AM EDT TUE SEP 20 2016

West southwest winds to 25 knots will diminish to 20 knots or less
tonight into Wed as the pres gradient weakens with the Canadian low
lifting farther ne across Hudson Bay. Winds will remain blo 20 kts
into Saturday under a weak pres gradient across the Upper Lakes. &&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement until 2 PM EDT this afternoon for MIZ006.

Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...Voss
LONG TERM...Rolfson
AVIATION...07/JV
MARINE...Voss



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