Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 241917

Area Forecast Discussion
National Weather Service Marquette MI
317 PM EDT Mon Apr 24 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 317 PM EDT MON APR 24 2017

12Z raobs/latest wv imagery and RAP analysis show a wsw flow alf
over the wrn Great Lks to the e of upr troffing dominating the wrn
CONUS/sw Canada. The ese flow arnd a retreating sfc hi pres rdg
extending fm nw Ontario into the se Great Lks is advecting dry llvl
air shown on the 12Z APX, GRB and MPX raobs into Upr MI. But there
are plenty of hi clds streaming into the cwa ahead of a shrtwv/sfc
lo pres in the nrn Plains lifting toward MN within the wsw upr flow.
Despite this hi cld, temps have risen well aoa normal, especially
over the w with downslope flow away fm lk moderation.

Tngt...Shrtwv in the ncentral Plains will move ne, reaching wrn Lk
Sup late tngt. Since this disturbance is fcst to shear out a bit as
it enters a more confluent upr flow and the ssw lo-mid flow wl still
be tapping the dry air to the s, the bulk of the models indicate no
more than isold-sct showers wl impact only the nw portion of the
cwa. Plenty of hi clds and steady winds wl limit the diurnal temp

Tue...A shrtwv rdg axis is fcst to aprch following the exiting
shrtwv to the ne. So any pops over the nw cwa wl tend to diminish
until later in the day, when another shrtwv and some large scale
forcing/hier pwat aprch fm the sw as the lo-mid flow grdly taps a
moister airmass. The best chc of some showers mainly in the 21-24Z
time frame wl be over the w closer to the aprchg forcing/deeper
moistening and along a slow moving frontal bndry that wl push slowly
into the far w during the day in the wake of the first passing
shrtwv to the ne. Many of the short term guidance also indicate the
llvl moistening wl be sufficient to bring a return of some lo clds
over at least the e half. Despite the incrsg clds, expect temps to
top out as hi as the 60s, warmest over the central away fm Lk MI
moderation and some thicker clds/late arriving cold fnt over the w.
If there is more sunshine, a few places in the downslope regions
near Baraga could see 70 degree max temps.

.LONG TERM...(Tuesday through Sunday)
Issued at 437 AM EDT MON APR 24 2017

...Active pattern with frequent chances for precipitation...

Broad upper level trough with vigorous jet stream punching in off
the Pacific sets up over much of the Conus into next weekend.
Couple of stronger shortwaves/associated waves of low pressure
will work across Upper Great Lakes bringing potential for
widespread precip. Enough cold air may be drawn into these systems
to result in wintry precipitation. Precip totals this week will
be well above average. Based on qpf projections from WPC, very
feasible that total monthly precip at NWS Marquette would end up
over 5 inches which would place this month into the top 5 for
wettest Aprils on record.

Now appears generally warm and mainly dry on Tue ahead of more
unsettled weather pattern for the rest of the week. Exception could
be some light rain over west half to start the day as southern edge
of shortwave moving by over northern Ontario clips the area. Best
chances over far west and Keweenaw as sfc trough pushing toward
western Lk Superior propels a warm front across the area. In recent
days it appeared this low would be stronger but trend is weaker now
as majority of shortwave energy stays back over Rockies and central
Plains until later Tue night and Wed. Clouds will be around to start
the day over the west closer to the sfc low and could also see
strato cu expand through the day over east forecast area with surge
of moisture advection blo h7. Where clouds are not too thick during
peak heating on Tue max temps should push well into the 60s away
from onshore flow close to Lk Michigan.

Eventually will see more rain spread over western Upper Michigan
late Tue aftn into Tue evening as shortwave lifts over the northern
Plains and stronger sfc low moves to the Upper Mississippi river
valley overnight Tue night. Greatest chances for rain will be
overnight into Wed morning as the larger scale lift is enhanced by
developing coupled jet structure and increasing h85-h7 frontogenesis
on northwest/cold side of approaching sfc trough. Should be swath of
moderate to possibly heavy rain where forcing maximizes but will
likely be in relatively narrow swath. Quite a spread in forecasted
12hr qpf 00z-12z Wed with minimum of less than 0.25 inch to maximum
of well over 1 inch. Trend is for sfc temps to stay just warm enough
even over far west to limit fzra potential and keep ptype rain for
the forecast area through the night. Precip should begin to diminish
later Wed as this shortwave lifts north of Lk Superior and next
stronger shortwave digs over the central Plains.

For rest of Wed into Thu preferred the way ECMWF handled that next
shortwave and associated track of sfc low as it matched up best with
majority of recent NAEFS ensembles. Result was NE low level flow
keeping steady or even falling temps toward 32F over far west Wed
aftn into Wed evening. Since max wet bulb temps aloft are still 2-3c
at that point the setup points to freezing rain or sleet Wed night
into Thu before cooler air moves in on Thu. Current forecast shows
total freezing rain/ice accumulations could exceed 0.25 inch Wed
night into Thu morning over west third, especially over the cooler
higher terrain locations. Overall idea matches up pretty well with
WPC probabilistic winter precipitation guidance. Gradual cooling
aloft on Thu which could lead to some snow. Right now though latest
guidance including more wrapped up and colder aloft ECMWF would
suggest near sfc temps warming into the low to mid 30s may keep
precip mainly in the form of rain. Warmer idea is also supported by
majority of NAEFS ensembles which keep the 32F sfc temp line mainly
to the northwest of here Thu.

Dry weather expected on Fri then another low pressure system lifting
in from the central Plains could bring more wet weather later in the
weekend. Sat looks mainly dry as it stands now which is a trend
toward ECMWF from 24 hour ago. System may have enough cold air to
lead to wintry precip Sun night into Mon morning. Seems that even as
the calender flips from April to May we just cannot shake the wet
and active pattern.

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 144 PM EDT MON APR 24 2017

A dry low-level air mass will dominate the area thru Tue mrng under
a good deal of hi clds, allowing VFR conditions to prevail at all
the TAF sites. Gusty ese winds this aftn up to 20-25kt, especially
at the more exposed CMX location, will give way to some LLWS tngt as
the near sfc lyr cools and increases llvl stability under continued
stronger winds above the sfc-based invrn.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 315 AM EDT MON APR 24 2017

N winds up to 20 kts over the e half of the lake will diminish this
evening as a hi pres ridge builds over the Upper Lakes. As this
ridge shifts to the e and a deepening lo pres in the Plains moves
toward MN, expect winds to veer toward the e-se and increase up to
30 kts on Mon. Where the winds will be strongest over the ncentral,
there could be a gale. Winds will veer southeasterly overnight at 20
to 30 knots before gradually diminish to 10 to 15 knots across the
western half of the lake by Tuesday morning. Further central and
east, expect the southeast winds of 20 to 30 knots to persist. A few
gale force gusts to 35 knots are possible early Tuesday night.
Northeast gales of 35 knots look likely across much of the lake as
the pressure gradient increases behind an exiting surface trough
late Tuesday night through Wednesday. It is possible these winds may
hold on through Wednesday night into Thursday, especially across the
central and eastern portions of the lake. By Friday morning, winds
will back west-northwest and diminish to around 10 to 20 knots.
These winds will continue through the weekend, but veer to the east-

Upper Michigan...
Lake Superior...
  Gale Watch from late Tuesday night through Wednesday evening for

  Gale Watch from late Tuesday night through late Wednesday night
     for LSZ264.

Lake Michigan...


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