Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 250821

Area Forecast Discussion
National Weather Service Marquette MI
421 AM EDT Sat Mar 25 2017

.SHORT TERM...(This evening through Saturday)
Issued at 342 PM EDT FRI MAR 24 2017

Water vapor imagery shows a stout moisture plume continuing to
stream northward out of the Gulf of Mexico all the way up into
Wisconsin and has been feeding into the mid-level baroclinic zone
that has slowly begun push south across south central and eastern
Upper Michigan this afternoon. Surface temperatures were slow to
respond, but where precipitation continues to call this evening
temperatures have warmed above freezing. A few locations north of
the precipitation have seen persistent fog, especially where
northerly winds have resulted in onshore and upslope flow.

Through the rest of the evening and overnight hours, winds will
increase a bit compared to the calm winds experienced through the
day today. While the winds will not be impressive, trees that are
still coated in ice may become problematic and/or be susceptible to
broken limbs. Rain across the south central will continue to push
south of the area as high pressure near the Hudson Bay continues to
slowly drop across southeast Ontario. This will result in surface
winds becoming east-northeasterly over night. These upslope winds
across north central portions of the area extending west into the
Keweenaw may result in the development of freezing drizzle and light
snow. Forecast soundings show cloud top temperatures leaning more
towards ice crystals, so it may be more light snow than freezing
drizzle, but precipitation is expected to remain quite light. These
areas may also see fog due to the upslope/onshore flow. As the
surface high pressure drops closer to the area, low-level dry air
will begin to filter south across the area and should allow for any
precipitation and fog to diminish by daybreak. During the day on
Saturday, expect a mostly dry day across the U.P. as the bulk of the
precipitation remains south of the area through much of the day.
Through the afternoon, cloud cover will gradually try to scatter out
especially across the north, but do not expect this trend to
continue as more precipitation is on the way for Saturday evening.

.LONG TERM...(Sunday through Friday)
Issued at 420 AM EDT SAT MAR 25 2017

Medium range model guidance continues to indicate that split flow
will dominate the CONUS/southern Canada thru the upcoming week with
pcpn over the Upper Lakes mostly tied to southern stream energy that
drops into the sw CONUS and then tracks ene across the CONUS. One
system currently getting kicked e over the Plains by the next
shortwave trof arriving over the western CONUS will weaken as it
lifts into the Great Lakes region over the next couple of days. This
will lead to an unsettled couple of days with periodic -ra and even
some -fzra at times Sun/Mon as the lead energy and trailing
shortwave trof affect the area. After a dry period midweek, a pair
of southern stream shortwaves will probably bring one or more
opportunities for pcpn late next week/weekend. Overall, it appears
pcpn amounts will generally be on the lighter side. As for temps,
split flow across N America will keep arctic air bottled up way to
the n, resulting in above normal temps across the Upper Lakes on
most days for the next 1-2 weeks. Latest CPC week 3-4 experimental
outlook (Apr 8-21) suggests a continuation of a pattern that should
favor above normal temps overall.

beginning Sun thru Mon night, mid-level low currently centered over
OK will be near St Louis Sun morning and will weaken/open up as it
moves to the Lower Lakes by Mon morning. Meanwhile, upstream trof
currently moving onshore over the western CONUS will weaken as it
reaches the western Great Lakes by Mon evening. Deep moisture
associated with the first system will return to the area tonight and
will persist until the second shortwave trof passes Mon night.
Result will be damp conditions Sun/Mon with periodic -ra. The main
fcst challenge is that the low-level flow will remain easterly thru
Sun before backing northerly into Mon. This will act to maintain
some colder near sfc air blo an elevated warm layer with 850mb temps
well above 0C, allowing for the potential of more -fzra, mainly
during the night/early morning. Fortunately, forcing is weak thru
the period, so pcpn amounts should be light overall, preventing any
significant icing. Best potential of icing will be tonight into the
morning hrs on Sun as temps should fall a few degrees blo freezing
tonight over much of the area before pcpn arrives, and then only
slowly rise thru Sun morning.

Shortwave trof that reaches the western Great Lakes late Mon will
shift e of the area by Tue morning, shunting deep moisture out of
Upper MI. Hudson Bay sfc high pres will then ridge s into the Great
Lakes in association with northern stream mid level ridge shifting e
across s central Canada, supporting a return of dry weather for

Thu thru Sat, there is a plenty of model uncertainty with the GFS
moving significantly different from the ECMWF. The GFS is putting
more emphasis on northern stream energy and makes the northern
stream the more dominant influence on Upper Lakes weather, keeping
southern stream energy well s of here. The ECMWF maintains a more
influential southern stream with energy over the southern Rockies on
Tue lifting into the Great Lakes late in the week. The CMC and UKMET
lend support to the ECMWF, which has been a bit more consistent over
the last couple of runs than the GFS, and it probably represents a
somewhat better solution for late in the week. That said,
confidence, which is never particularly high in the latter part of a
7 day fcst, is quite a bit lower than typically the case. Chc pops
will cover much of the Thu-Sat time frame. While ptype will likely
be mostly rain, not out of the question that there could again be
issues with fzra. Some snow may be possible as well.

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1246 AM EDT SAT MAR 25 2017

Tonight, expect the lower ceilings to linger at SAW with winds
veering around to the east-northeast providing good onshore/upslope
flow. IFR cigs at IWD will also persist tonight. MVFR conditions
will prevail at CMX where ne winds are less favorable for low cigs.
Drier air moving in Saturday will bring improving conditions to MVFR
at SAW and IWD and to VFR during the afternoon at all TAF sites.
MVFR cigs will move back in later Saturday evening as low level
moisture edges back into the region from the south.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 342 PM EDT FRI MAR 24 2017

Tonight in Saturday, winds will become northeasterly and eventually
veer around to the east at speeds up to 20 to 30 knots. Saturday,
easterly winds will decrease to around 15 to 25 knots. The highest
winds are expected to be across the far western portion of the lake
as winds will funnel parallel to the shoreline into northern
Wisconsin and Minnesota. Saturday night winds will decrease across
the west to around 15 to 20 knots and increase to around 20 to 25
knots across the east. Winds will become light and back to the north
Sunday into Monday. Monday through the middle of the week, northerly
winds will persist over the lake, with speeds at times up to 15 to
20 knots.

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


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