Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 200724

Area Forecast Discussion
National Weather Service Marquette MI
324 AM EDT Sat May 20 2017

.SHORT TERM...(This evening through Saturday)
Issued at 319 PM EDT FRI MAY 19 2017

High clouds have overspread much of the area today and have limited
our mixing and diurnal heating this afternoon. This has resulted in
slower warming through the afternoon and dew points running a bit
higher. High pressure continues to push east across northern
portions of Lake Superior this afternoon, and rain showers across
southern Wisconsin have continued to wane as they run into a drier
air mass and better large scale subsidence.

Tonight the big question will be how low temperatures get. Given the
high clouds expected, do not expect temperature to drop as low as
they did last night. Generally speaking, low to upper 30s are
expected. It is possible that a few locations may see temperatures
around or just below freezing, especially across the higher terrain
in the interior west and central. During the day Saturday, cloud
cover will be on the increase as mid-level clouds thicken ahead of
an approaching area of low pressure. The surface pressure gradient
will also increase, bringing gusty easterly winds across the area.
As warm air advection overspreads the region, ahead of low pressure
lifting out of the Middle Mississippi River Valley, rain showers
will lift north into Upper Michigan through the afternoon and
evening hours. Initially, given how dry the air mass is overhead, it
may take a while for the low levels to moisten up enough for
precipitation to reach the ground; therefore have delayed the
arrival of precipitation a bit. The instability looks like it will
remain south of the area and lapse rates are quite unimpressive, so
opted to leave out mentions of thunder through the afternoon and
evening hours. Given the more stable airmass in place, expect
precipitation to remain more stratiform; therefore, do not think
rainfall rates will be terribly impressive.

.LONG TERM...(Sunday through Friday)
Issued at 320 AM EDT SAT MAY 20 2017

An upr trof centered over the Great Lks wl dominate the upper air
pattern for at least the first half of the coming week. Although no
heavy pcpn appears likely during this time, a general cyc llvl flow
over the area should result in a good deal of cld cover and a chc of
some showers at times. Blo normal temps wl also prevail, especially
the daytime hi temps with the cld cover. After the deep upr trof
exits to the e at mid week, a passing sfc hi pres wl bring at least
a brief period of dry wx. There remains much uncertainly on the
track/timing of a rather strong disturbance that wl follow and bring
a return of shower chcs sometime later in the week.

Sun...Lingering rain on Sun mrng ahead of lo pres lifting nwd toward
the wrn cwa and its attendant occluded fnt to triple pt lo pres
moving thru Lower MI wl diminish to perhaps some drizzle with
vigorous dry slotting under jet surge region on the ern flank of
supporting shrtwv moving n thru MN. As the lo pres continues into
wrn Lk Sup/Ontario during the aftn and the occluded fnt shifts to
the n, a dvlpg wsw flow on the srn flank of the lo wl end any pcpn
over the scntrl with downsloping wind component. But upslope wind
component wl keep pcpn chcs going over at least the hier terrain of
the nw cwa. Although there could be some breaks in the cld cover
over the scentrl later in the day with the downsloping wind, more
lingering clds overthe rest of the cwa within the llvl cyc flow wl
hold max temps blo normal, especially over the wrn cwa.

Sun ngt into Mon ngt...Slow moving, closed lo is fcst to exit only
slowly to the ne, resulting in just a gradual weakening of the llvl
cyc wly flow over Upr MI. Although the absence of any large scale
forcing wl restrict pcpn chcs, the lingering moist cyc flow wl bring
a continued chc of mainly light showers to most of the cwa,
especially away fm the scentral, where the downsloping wind
component wl be a greater negative for pops. H85 temps falling into
the 2-4C range and the clds wl result in blo normal temps,
especially Mon daytime maxes with the cld cover.

Tue/Tue ngt...A shrtwv digging sewd thru the nrn Plains on Mon is
progged to move near Iowa by 12Z Tue and then Chicago by 12Z Wed,
resulting in a deepening upr trof centered over the Great Lks. Many
of the medium range models show a slowly deepening sfc lo pres
associated with this shrtwv moving toward Lower MI. Although the
sharper forcing/heavier pcpn accompanying the shrtwv are progged to
remain to the s of Upr MI, rather deep cyc flow and lingering mstr
over the cwa wl still result in plenty of clds and probably at least
some sct showers, with the hier pops over the se closer to the
sharper dpva/deep lyr qvector cnvgc. Since h85 temps wl remain arnd
2C, cool wx wl persist, especially the daytime hi temps on Tue under
the clds.

Wed thru Fri...As the deep upr trof axis/sfc lo pres drift slowly to
the e on Wed, trailing hi pres/acyc flow and axis of much drier air
wl bring clrg during the day. With h85 temps rising to within a
couple degrees of 6C, expect max temps to rebound aoa 60 over the
scentral farther fm Lk Sup moderation. Depending on how quickly
the sfc hi pres shifts to the e on Wed ngt, Thu mrng could be
chilly with lgt winds before a strenghtening sly flow ahead of the
next shrtwv sliding e thru the Plains near the Cndn border brings
a return of moister, more seasonably warm air and shower chcs
late in the week. The longer range models show a great deal of
uncertainty on the timing/track of this disturbance, so the fcst
wl show only lo chc pops for Thu/Fri.

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 126 AM EDT SAT MAY 20 2017

VFR conditions will prevail through Sat afternoon. Rain showers will
begin to lift north across the area as low pressure lifts north
towards the area Sat afternoon. Winds will also increase and become
gusty during the day as the pressure gradient increases. Conditions
will fall to MVFR at all sites by Sat evening as the rain becomes
more widespread.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 320 AM EDT SAT MAY 20 2017

Ene winds 10 to 20 kts this morning will increase up to 25 to 30 kts
over the w half of Lake Superior this afternoon as the pres gradient
ahead of lo pres approaching from the sw tightens sharply over that
area and where terrain influences will accentuate the ne flow. The
sharper pres gradient and strong winds up to 30 kts will overspread
the rest of the lake tonight. Not out of the question there could be
some gales over the far w where the funneling of the ene flow will
continue. As the lo pres passes into Ontario on Sun and drags a
trough across Lake Superior, expect the winds to diminish and shift
to the w-sw by Sun night. Winds under 20 kts should then be the rule
on Mon into Wed as a relatively flat pres gradient dominates the
Upper Lakes.

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


SHORT TERM...Ritzman
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