Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 181127

Area Forecast Discussion
National Weather Service Marquette MI
727 AM EDT Mon Sep 18 2017

.SHORT TERM...(Today and tonight)
Issued at 519 AM EDT MON SEP 18 2017

Water vapor imagery and RAP analysis show sw flow into the Upper
Great Lakes early this morning btwn a mid-level low over far
northern Ontario and ridging extending from the western Gulf of
Mexico to southern Quebec. Upstream, a weak shortwave trof over the
Plains will be the next feature of interest as it lifts ne. With sfc
high pres building over the area, it`s been a quiet, cool night.
Patchy/shallow fog has developed in the interior. Temps have fallen
to the low to mid 30s at traditional interior cold spots, so there
will be some patchy frost early this morning as well.

Shortwave trof over the Plains will lift ne, reaching the western
Great Lakes this evening. Radar imagery early this morning shows
shra/tsra across the Plains associated with the wave, and this pcpn
appears to be tied closely to the right entrance upper divergence
zone associated with upper jet extending from western Nebraska
toward southern Hudson Bay. Following progression of the upper jet,
the upper divergence should support a band of shra streaking ne
across western Upper MI as vast majority of model guidance shows.
Fcst will thus show chc pops spreading across western Upper MI this
aftn with some likely pops toward the MI/WI state line. Recent
hourly RAP/HRRR runs are insistent on the spread of pcpn ne into the
area. Will continue to monitor those runs in addition to 06z runs of
CMC/NAM/GFS to see if an update to higher pops is warranted. Shra
will be moving into a drier air mass over the Upper Lakes, so shra
should tend to diminish as they spread ne into the area. Expect high
temps in the 60s today. A few spots in the e where there will be
less cloudiness may touch 70F.

Shra will dissipate tonight, possibly without ever reaching the
eastern fcst area. Lingering cloud cover will keep min temps higher
than observed early this morning. Mid 40 to mid 50s should be the

.LONG TERM...(Tuesday through Sunday)
Issued at 303 AM EDT MON SEP 18 2017

Overall we will see a warming trend, with temperatures expected to
climb back up into the 80s by Friday. There will be periodic chances
for showers and thunderstorms, but confidence is highest Wednesday
night into Thursday as a cold front slowly pushes across the area.

Tuesday looks like it will be the coolest day in the extended with
near-normal temperatures as afternoon highs climb into the 60s
across the area. Cloud cover will be on the increase from the west
ahead of an approaching cold front, but expect Tuesday to remain dry
as surface ridging slowly exits the area. The warming trend will
continue Wednesday and Thursday, with high temperatures expected to
climb into the 70s. Precipitation chances will increase late on
Wednesday through Thursday as a cold front slides southeast across
Upper Michigan. Certainly looks like the instability and deep-layer
shear will be favorable for strong to possibly severe thunderstorms
later in the day on Wednesday. During the day on Thursday, the cold
front will slow its southward progress and retreat back northward as
strong warm air advection quickly returns to the area. As the front
pushes back north, a few showers and thunderstorms will be possible
through the early part of the day on Thursday.

Friday and Saturday look to be the warmest days of the week. As the
above mentioned warm air advection continues to stream northeast
across Upper Michigan, 925-850mb temperatures soar into the teens
and possible near 20 C. These warm temperatures aloft coupled with
ample downslope south-southwest winds should easily allow
temperatures to climb 10 to 20 degrees above normal for this time of
year. As we will be firmly within the warm sector, expect the
humidity to increase as well. Precipitation wise, cannot rule out a
few showers and thunderstorms associated with the return of warm air
advection and subtle shortwave activity.

Towards the end of the weekend and early next week, precipitation
chances will increase as a cold front to our west finally begins to
push eastward. Given the upper-air pattern and the general trend of
slowing the arrival of this front, wouldn`t be surprised if the
timing continues to get pushed back even further. Therefore, the
primary area of focus for precipitation is expected to be across the

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 727 AM EDT MON SEP 18 2017

A relatively dry low-level air mass should allow VFR conditions to
prevail thru the fcst period at KIWD/KCMX/KSAW. A disturbance
approaching the area will spread some -shra into w and central Upper
MI this aftn/evening. If -shra occur at any of the terminals,
conditions won`t fall out of VFR given that the pcpn will be light.
KIWD probably has the best chc of seeing -shra.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 519 AM EDT MON SEP 18 2017

High pres over the Upper Lakes will lead to winds mostly under 15kt
across Lake Superior today and tonight. As the high shifts e on Tue
and a low pres trof moves out over the Plains, winds will begin to
increase a bit on Tue, but much more so Tue night and Wed as the
trof moves closer. SE to S winds will increase to 20-25kt across
much of the lake Tue night and will increase up to 30kt over eastern
Lake Superior on Wed. With passage of the trof, winds will drop off
quickly to under 15kt from w to e Wednesday night with these lighter
winds lingering thru Thu.

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


SHORT TERM...Rolfson
LONG TERM...Ritzman
MARINE...Rolfson is the U.S. government's official web portal to all federal, state and local government web resources and services.