Area Forecast Discussion
Issued by NWS Marquette, MI

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890
FXUS63 KMQT 241942
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
342 PM EDT Fri Mar 24 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...(Saturday through Thursday)
Issued at 428 AM EDT FRI MAR 24 2017

Split flow will dominate the CONUS/southern Canada thru the upcoming
week with pcpn largely tied to southern stream energy that drops
into the sw CONUS and then tracks ene across the CONUS. One system
emerging over the western Plains today will weaken as it is kicked
ne to the Great Lakes early next week by the next shortwave trof
reaching the western CONUS. This will lead to rain and some fzra at
times Sat night thru Mon as the lead and trailing shortwave trof
affect the area. After a drier period midweek, a pair of southern
stream shortwaves may bring more 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 overall above normal temps
across the Upper Lakes for the next 1-2 weeks.

Beginning Sat, strong sfc high pres building across northern Ontario
today/tonight will become centered near James Bay by Sat evening.
Dry air emanating from this high will suppress pcpn associated with
warm front extending into the Lower Lakes from southern stream mid-
level low that will reach MO. However, there is a push of moisture
and weak isentropic ascent from the s during the aftn which may aid
a northward advancement of -ra into southern Upper MI during the
aftn. Prior to that, despite the strong sfc high pres passing by to
the n, which would normally suggest significant low-level drying,
fcst soundings show considerable low-level moisture blo about 4kft,
especially over roughly the w half of Upper MI, farther from the
departing sfc high. Not out of the question that there could be some
-dz/-fzdz during the morning where low-level easterly flow upslopes.

Sat ngt thru Mon ngt, mid-level low over MO Sat evening is fcst to
open up/weaken as it lifts across Lower MI to southern Ontario and
the Lower Lakes. This occurs in response to upstream shortwave trof
moving across the Plains Sun and reaching the Mississippi Valley
late Mon. As a result, deep moisture will expand across the area
with all model guidance indicating periodic pcpn. 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 h85 temps above
0C, allowing the potential of more -fzra, mainly at night.
Fortunately, forcing is weak, so pcpn amounts should be light
overall, and there should not be any significant icing.

With shortwave trof over the Mississippi Valley late Mon shifting e
of the area by Tue morning, expect dry weather to return for Tue/Wed
as Hudson Bay sfc high pres builds into the Upper Great Lakes.

Wed night/Thu, there is uncertainty on the the strength/track of a
northern stream shortwave running roughly along the U.S./Canadian
border. 00Z ECMWF has significantly backed off on the strength of
this wave, and now does not generate any pcpn. 00Z CMC still
maintains a stronger wave with pcpn while the 00Z GFS is similar to
the ECMWF. With some weighting from previous model runs, fcst will
reflect a chc of pcpn Wed night into Thu.

Late week, at least one batch of southern stream energy may make a
run toward the Great Lakes, but there is little model agreement or
consistency at this point.
&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 138 PM EDT FRI MAR 24 2017

Conditions this afternoon vary from MVFR to LIFR, with KIWD
continuing to see the lowest ceilings and visibilities as onshore
flow continues out of the northwest. Further north, winds have veer
around more northerly and has allowed the better upslope flow to
weaken. Across KSAW, the combination of moist onshore and upslope
flow out of the north has allowed the IFR ceilings and visibilities
to remain in place. Tonight, expect the lower ceilings to linger at
KSAW and KCMX with winds veering around to the east-northeast
providing good onshore/upslope flow. Soundings suggest enough low-
level lift and saturation will take place at KCMX for some light
snow, and possibly some light freezing drizzle, to develop later
tonight. Soundings show that cloud top temperatures may be just cold
enough to support snow rather than freezing drizzle, so opted to
just mention light snow for now. We may see a brief increase in
visibilities at KSAW later this afternoon, but expect the lower
visibilities to return with upslope flow developing overnight. As
winds veer to the east-northeast, KIWD will see improving conditions
as downsloping flow should allow ceilings to rise gradually to the
MVFR category.
&&

.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.
&&

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

$$

SHORT TERM...Ritzman
LONG TERM...Rolfson
AVIATION...Ritzman
MARINE...Ritzman



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