Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 281745

Area Forecast Discussion
National Weather Service Marquette MI
145 PM EDT Sun May 28 2017

.SHORT TERM...(Today and tonight)
Issued at 321 AM EDT SUN MAY 28 2017

Upper air pattern consists of a 500 mb closed low near Lake Winnipeg
with a 500 mb trough over the northern and central plains this
morning. An impressive looking shortwave on water vapor is in the
ern Dakotas and this heads east into the upper Great Lakes this
afternoon and early evening with the 500 mb low moving to Lake
Superior late tonight. Nam shows some 850-500 mb q-vector
convergence and moisture remaining over the area through tonight.
Will continue with a diurnal trend for pops with them highest in the
late afternoon and diminishing in the evening once sfc heating goes
away. Will also continue with some thunder in the forecast as well
as there is some low level cape up to 700 j/kg in the boundary layer
through 180 meters. Will also continue with likely pops in the
afternoon and have the lowest pops across the north and go with
chance pops tonight. Overall, did not make too many changes to the
going forecast.

.LONG TERM...(Monday through Saturday)
Issued at 256 AM EDT SUN MAY 28 2017

The main forecast highlights are a cloudy and cooler Memorial Day,
with chances for lingering showers across much of the area, and some
thunder possible across the south central and eastern portions of
Upper Michigan. The cooler temperatures will linger through Tuesday,
with lingering rain showers across the area. Towards the middle/end
of the week, temperature will rebound back to near normal, but
additional precipitation chances may be on the horizon. Next
weekend is a challenging forecast considering the models are
struggling to break up the dominant cutoff blocking flow across the
Great Lakes region.

As a pesky upper-level low is expected to linger across the region,
confidence is high that cooler temperatures will prevail with
lingering chances for rain showers, as multiple rounds of vort
maximums rotate in and out of the area, through Wednesday. It
doesn`t look like we will see a persistent rain through the whole
time period, rather periods of rain showers across the area. Monday
will be the best chance at seeing any additional thunderstorm
activity, as mid-level lapse rates will be steepest, with the cutoff
low pushing overhead during the day, and one last bout of
instability develops across central and eastern portions of Upper
Michigan. The shear on the other hand doesn`t look impressive, so
updrafts may struggle a bit to maintain their intensities. Scattered
area-wide showers will continue Tuesday and early Wednesday, then
the main upper-level low slowly try to lift out of the region.

Towards the middle/end of the week, the medium range models start to
diverge on the track and return of cutoff energy aloft. The GFS is
stronger, and thus slower; while the ECMWF is much faster with the
cutoff energy. Depending on how the upper-air pattern evolves the
better precipitation chances could come on either Thursday or
Friday. Therefore, confidence is a low in how precipitation chances
will pan out. All that being said, how far west the main trough axis
gets and where additional shortwaves track will be the key to where
any additional precipitation develops later this week.

Confidence continues to decrease as we get to next weekend with the
medium range models struggling to come to a consensus, which makes
sense as they struggle to break up the blocking pattern we will be
in for much of this week. Given the potential for lingering upper-
level energy with vort maximums still rotating and digging across
the area; cannot rule out additional chances for rain next weekend.

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 144 PM EDT SUN MAY 28 2017

VFR conditions should mostly prevail at KIWD/KCMX/KSAW until late in
this fcst period. A couple of disturbances will slide through Upper
Michigan this afternoon, late tonight and again on Monday. This will
bring scattered to numerous showers to each of the TAF sites, most
numerous during peak heating. There is enough instability this
afternoon for some isolated TS first at the IWD and CMX TAF sites
then shifting eastward to KSAW by late this afternoon. The chances
of thunder diminish this evening through the remainder of the TAF
period. It is not out of the question that there could be some
lowered visibility under some of the heavier showers along with some
lowered ceilings; however, the better chance will come later tonight
into Monday morning as a close upper level low slides overhead. This
will likely give MVFR to IFR conditions at times for mainly IWD and
CMX toward the end of this TAF period.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 321 AM EDT SUN MAY 28 2017

Through the weekend, winds of 10 to 20 knots are expected across
Lake Superior. Early next week, winds will increase to around 20 to
25 knots as an area of low pressure is progged to dig across
portions of the Upper Great Lakes. Towards the end of the week as
the surface pressure gradient relaxes behind the exiting low
pressure system, winds will decrease to around 10 to 15 knots.

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


LONG TERM...Ritzman
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