Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 202002
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
402 PM EDT Mon Mar 20 2017

.SHORT TERM...(Today and tonight)
Issued at 301 AM EDT MON MAR 20 2017

Upper air pattern consists of a 500 mb ridge across the central and
southern plains with a broad trough across central Canada skirting
the northern plains this morning. This broad trough slowly digs into
the upper Great Lakes today with a shortwave near Lake Winnipeg by
00z Tue. This shortwave moves through the area tonight. Nam shows
some deeper moisture and some 850-500 mb q-vector convergence moving
through tonight. Overall, did not make too many changes to the going
forecast. Have some chance pops in for northwest lake effect snow
belts late tonight as cold air comes in aided by some deeper
moisture and dynamics behind the shortwave.

.LONG TERM...(Tuesday night through Monday)
Issued at 401 PM EDT MON MAR 20 2017

A cold nly flow ahead of Cndn hi pres bldg toward the Upr Lks wl
cause some les over mainly the e half on Tue ngt, but the dryness of
the incoming airmass/lowering subsidence invrn base wl limit the
intensity of this pcpn, which wl end on Wed with the arrival of the
sfc hi. After some dry and milder wx on Wed and Thu, another chc for
some mixed pcpn wl arrive on Thu ngt ahead of a warm fnt associated
with a srn branch closed lo lifting enewd out of the srn Rockies.
How long this pcpn lingers wl then depend on how quickly/far to the
s a sfc hi pres under a nrn branch flow in scentral Canada expands
into the Upr Lks on Sat.

Tue night...Upr MI wl be under the influence a confluent nw flow alf
btwn shrtwv sliding to the se and progressive upr rdg axis moving e
thru the nrn Plains. The cold n flow ahead of a Cndn hi pres center
that is progged to move fm near Lk Winnipeg to the MN arrowhead by
12Z Wed is fcst to drop h85 temps as lo as about -19C over the ern
cwa during the ngt, allowing for a transition to pure les in the
absence of daytime heating. But the dry nature of the incoming
airmass that leads to an inverted-v T/Td profile on the fcst
sdngs/fcst lo invrn base near 4-5k ft agl and trend toward a more
acyc llvl flow especially over the w under the large scale
dnva/subsidence wl hold down the les intensity/coverage. The best
chc for a few inches of fluffy sn wl be over the ncentral and e, an
area closer to the h85 thermal trof and impacted by a longer
fetch/more modification acrs Lk Sup that is fcst to allow some lk
induced troffing and more near sfc cnvgc possibly enhanced by a land
breeze wind component. With diminishing winds, pwat falling toward
0.10 inch, and at least partial clrg closer to the incoming hi pres,
temps over the interior w half wl fall into the single numbers and
perhaps near zero. Tended toward the lower end of guidance for temps
in this area.

Wed/Wed ngt...Lingering les over the e half wl end Wed mrng as the
sprawling sfc hi pres builds over Upr MI during the day ahead of the
incoming upr rdg axis. Under mosunny skies/incrsg early spring sun
angle, expect temps to rebound sharply well into the 30s over at
least the interior w half. The combination of incrsg hi clds
sprilling over the aprchg upr rdg axis and an incrsg sly flow on the
wrn flank of the sfc hi pres retreating to the e wl limit the
diurnal temp fall, which wl be sharpest over the interior e closer
to the departing hi/core of drier air.

Thu...The gusty sly flow on the western flank of the departing sfc
hi pres is fcst to lift h85 temps as hi as about 4C by late in the
day. Despite some incrsg waa mid/hi clds, max temps wl recover into
the 40s away fm the cooling influence of mainly Lk MI. Although some
of the medium range guidance indicates there could be some light
pcpn under the waa/incrsg mid lvl mstr, the dryness shown in the
llvls of the fcst sdngs suggest the day wl be dry.

Thu ngt into Sat...The fcst for Upr MI during this time wl depend on
the evolution of an incrsgly split upr flow that wl feature a closed
srn branch lo moving fm the srn Rockies on Thu ngt toward the OH
River Valley/Lower Great Lks on Sat and sfc hi pres under upr rdging
in the nrn branch flow that wl prevail over scentral Canada.
Although the guidance differs on the details, the medium range
models show some mixed pcpn, with ptype impacted by near sfc
evaporate cooling of the very dry llvl antecedent airmass that would
favor at least a period of freezing ra during fvrbl period of
nocturnal cooling, wl dvlp on Thu ngt but change to mainly ra into
Fri ahead of the warm fnt extending enewd fm the srn branch lo
emerging into the srn Plains toward the Lower Lks and under some upr
dvgc in the rrq of an h3 jet core within the confluence zn btwn the
branches located to the s of James Bay. Following the passage of a
cold fnt attendant to a nrn branch disturbance tracking thru
Ontario, the Cndn hi pres is fcst to follow into nw Ontario on Sat.
Exactly how quickly and far to the s this hi blds into Ontario and
how much cold/dry air flows into the Upr Lks wl determine the
evolution/placement of the waa pcpn band. The trend exhibited by the
12Z GFS/Cndn models shows a sfc hi pres bldg faster/farther to the
s, suppressing the waa pcpn band to the s by 12Z Sat, with only some
lgt pcpn persistening over the ncentral on Sat under an upslope ene
flow on the srn flank of the Ontario hi pres. Considering the
uncertainty with the expected split flow pattern, maintained the
model consensus fcst.

Sun/Mon...Uncertainly lingers in the longer term as to whether some
pcpn on the nrn flank of the slow moving srn branch closed lo wl
expand back toward the Upr Lks later in the weekend/early next week
following the passage of the sfc hi pres center into Quebec. Any
associated mixed pcpn would impact mainly the se cwa closer to the
closed lo. If the hi pres is more expansive, this period could be
dry.
&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 240 PM EDT MON MAR 20 2017

Quiet with VFR conditions until later tonight when cold front pushes
across Upper Michigan. Expect a brief periof of scattered rain/snow
showers as the front moves through, mainly at CMX. Colder air moving
in on Tue combined with moisture off Lk Superior and daytime heating
should result in scattered snow showers on Tue, but only mostly
during the morning at IWD and CMX. Ceilings should drop to around
030 late tonight into Tue morning but otherwise will end up in the
lower VFR range up to 050. Vsby within in heavier snow showers on
Tue could drop to IFR at 1-2sm but for the most part should be
MVFR to VFR. NW-N winds may gust over 20 kts late tonight into
Tue so there also could be blsn, especially at SAW.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 301 AM EDT MON MAR 20 2017

With the cold air moving across the lake, north gales to 35 knots
are expected Tue morning across the central and eastern lake. There
could be a little freezing spray tonight into Tue morning. These
would be the strongest winds forecasted for this forecast period.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning from 5 AM Tuesday to 2 AM EDT Wednesday for
     LSZ249>251-266-267.

  Gale Warning from 2 AM to 8 PM EDT Tuesday for LSZ243>248-264-
     265.

Lake Michigan...
None.
&&

$$

SHORT TERM...07
LONG TERM...KC
AVIATION...JLA
MARINE...07


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