Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 300924
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
524 AM EDT Sun Apr 30 2017

.SHORT TERM...(Today and tonight)
Issued at 523 AM EDT SUN APR 30 2017

Water vapor imagery and RAP analysis show a vigorous mid-level low
spinning over the TX panhandle. Ahead of this feature, strong low-
level southerly flow off the Gulf of Mexico per 00z raobs is
transporting abundant moisture n up the Mississippi River Valley and
is leading to considerable shra/tsra activity which has spread as
far n as Lower MI. Closer to home, it`s been a dry/cool night across
the fcst area under considerable high cloudiness.

Model guidance for the progression of the vigorous Southern Plains
system into the Upper Great Lakes has changed little over the last
24hrs. Mid-level low at 500mb is still fcst to deepen around 150m by
the time it reaches Upper MI Mon evening with the associated sfc low
tracking into central Upper MI. Main axis of strong 850-700mb
moisture transport remains focused from the Lower Mississippi River
Valley to Lower MI today with secondary axis peeling back ahead of
the ne tracking mid-level low thru the Plains and into the Upper
Mississippi Valley by late aftn. With main moisture transport not
yet directed into Upper MI today and with only weak isentropic
ascent and lingering dry low-mid level air at least initially, opted
to push back pcpn timing into the fcst area today. Model guidance
supports this idea with all trending slower with the northward
advancement of pcpn. It`s quite possible pcpn may not reach the
southern fcst area until late aftn. While not delaying pops that
much, fcst will generally hold off pcpn mention until the aftn hrs
with a slow spread from s to n, but not reaching the Keweenaw before
00z. Considerable high/mid cloudiness and a steady e to ne wind will
limit warming today, but with delay of pcpn, temps were raised
slightly from previous fcst. Still, expect readings mostly in the
low/mid 40s, coolest along the Great Lakes shores.

Tonight, vigorous deep layer forcing per q-vectors combined with
strong isentropic ascent, arrival of axis of stronger moisture
transport and precipitable water increasing to above 1 inch/at least
250pct of normal will support a band of mdt pcpn swinging n across
the area. Pcpn may be briefly heavy at times. By 12z Mon, expect
widespread pcpn amounts roughly in the 0.5 to 1 inch range. In
addition, with mid-level dry slot surging nne, arrival of some weak
elevated instabilty and showalter index falling toward 0C, there
could be some rumbles of thunder. Included schc mention into roughly
the se half of the fcst area where parameters are more favorable.
Finally, not out of the question that there could be a little snow
mixed in with the rain initially over the high terrain of the nw
fcst area this evening as evaporative cooling of the lower level dry
air cools the column. If it occurs, it would be short-lived.

.LONG TERM...(Monday through Saturday)
Issued at 342 AM EDT SUN APR 30 2017

Expect an active beginning to the work week as low pressure lifts
northeast across the Upper Great Lakes. The best chance for
precipitation will coincide with this system, on Monday and Tuesday.
There will be another chance for precipitation later in the week as
a cold front pushes south across the area. Otherwise, for the most
part the weather looks like it will quiet down a bit later this week
and through the weekend. Temperatures will start off below normal,
before climbing back up into the 50s, which near normal for this
time of year.

On Monday as the above mentioned low pressure system lifts across
the Wisconsin and up into central/eastern portion of the area,
expect the rain to continue. With strong upper-level diffluence
overspreading the region ahead of the main cutoff energy lifting
northeast, the combination of strong synoptic-scale lift and PWATs
running upwards of 150-200% of normal, the heaviest rain is expected
to linger through the mid/late morning hours, especially across the
norther on Monday. The medium range models are consistent with
elevated instability lifting northeast with the main branch of mid-
level moisture transport. Therefore, would not be surprised if we
hear a few rumbles of thunder through the morning hours. By the
afternoon hours on Monday, the strong warm, moisture advection will
lift northeast of the area as the surface trough lifts into central
portions of the area, allowing for the left exit region of the upper-
level jet and main upper-level vort-maxes to move across the area.
This additional synoptic-scale lift will allow rain to linger
through the day on Monday.

Monday night through Tuesday, as the main surface and and upper-
level low lift across eastern portions of the area, expect
precipitation to linger and change over to snow in some locations as
cold air advection wraps around the exiting system. Based on current
forecast soundings, looks like precipitation across the west and
north central should remain mostly snow, especially across the
higher terrain. Depending on how deep the moisture is behind the
system, a few locations could pick up a couple of inches of wet,
heavy snow, especially across the west and the higher terrain in the
north central portions of the area. Further east and across south
central portions of the area, any lingering precipitation should
remain mostly liquid.

Wednesday things will begin to dry out as heights rise across the
area and high pressure briefly traverses the region. Precipitation
chances will return Thursday as an upper-level wave and weak cold
front push across the area. As the upper-level wave digs across the
region, we will remain under northwest flow into the weekend. With
embedded shortwave activity Thursday night and Friday, we may see
lingering rain showers; however, any precipitation should remain
fairly light.

This weekend, there are discrepancies among the GFS/ECMWF/Canadian,
all being a bit different in the placement and progressiveness of
upper-level energy. Depending on where the upper-level trough sets
up and how cutoff energy that is progged to lift out of the
southeast interacts with the upper-level flow, we could could have a
cooler weekend in store with a chances for precipitation late in the
weekend.
&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 137 AM EDT SUN APR 30 2017

VFR conditions will prevail into late afternoon; however, there may
be lower clouds into the MVFR range that try to build into the KSAW
TAF site late afternoon as rain moves northward into the area. With
more persistent rain during the evening, expect cigs to lower to
MVFR at IWD and to IFR at SAW by the end of the period. The dry air
should perist longer to the north with cigs remaining above MVFR at
CMX. However, confidence is lower this evening.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 523 AM EDT SUN APR 30 2017

As low pres tracks ne from the Southern Plains, expect increasing e
to ne winds today and tonight, especially tonight. Winds today will
increase more notably over western Lake Superior, reaching 20-30kt
during the aftn while winds over the e stay mostly in the 10-20kt
range. Tonight winds will continue to increase across Lake Superior,
reaching 35-40kt over much of the lake. Not out of the question that
locally higher gusts to around 45kt could occur late tonight over
western Lake Superior.

Northeast gales of 35 to 40 knots will persist through much of
Monday as the surface low tracks across central portions of Upper
Michigan enhancing the surface pressure gradient. Winds will subside
first across the eastern half of the lake late on Monday as the
surface low tracks across the eastern half. By Tuesday morning as
the low lifts into southern Ontario, winds will back northerly at 20
to 30 knots. Expect these winds to persist through the day on
Tuesday has cold air advects southward. By Wednesday morning, winds
will further subside to 10 to 15 knots. Winds will remain around or
under 20 knots through the end of the week and first part of the
weekend.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning from 2 AM to 2 PM EDT Monday for LSZ265-266.

  Gale Warning from 8 PM EDT /7 PM CDT/ this evening to 5 PM EDT
     /4 PM CDT/ Monday for LSZ162.

  Gale Warning from 2 AM to 8 PM EDT Monday for LSZ263-264.

  Gale Warning from 5 AM to 2 PM EDT Monday for LSZ243>246.

Lake Michigan...
  Gale Warning from 2 PM this afternoon to 8 AM EDT Monday for
     LMZ221-248-250.

&&

$$

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


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