Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 311950

Area Forecast Discussion
National Weather Service Marquette MI
350 PM EDT TUE MAY 31 2016

.SHORT TERM...(Today and tonight)
Issued at 427 AM EDT TUE MAY 31 2016

00Z raobs/latest wv imagery and RAP analysis show a shrtwv rdg axis
over the wrn Great Lks to the E of a fairly vigorous shrtwv moving E
thru the nrn Plains. Despite the presence of this rdg axis and dry
air shown on the 00z INL/GRB raobs, there have been some isold
showers over the far wrn CWA in Gogebic and Ontonagon Counties
associated with axis of some h85 fgen/h85-7 theta-e advctn in that
area well ahead of the shrtwv to the W. Except for some patchy hi
clds over nrn Lk Sup, skies farther to the E are generally moclr
deeper into the dry airmass associated with sfc rdg axis extending
fm hi pres center over Hudson Bay into the Upr MI. Looking farther
to the W, there is a much more wdsprd area of showers/TS over the W
half of MN under warm conveyor belt mstr ribbon ahead of the nrn
Plains shrtwv.

Today...Some of the hier res models show the isold showers over the
far W early this mrng moving as far NE as the Keweenaw and even near
Marquette by 12z as axis of h85-7 fgen shifts slowly in that
direction. But since the h85-7 mstr advctn is progged to fade slowly
as the band moves toward the core of the drier air, expect any isold
showers early this mrng to be confined to just the far W. The
showers over the far W are likely to begin to increase in coverage
later this mrng as axis of deeper mstr associated with warm conveyor
belt to the W pushes into that area. But the guidance is fairly
consistent on showing a fairly sharp ern edge to the pcpn shield fm
about the Keweenaw to Iron County that wl be maintained by more
persistent llvl dry air related to sfc-h925 ESE winds on wrn flank
of only slowly retreating sfc rdg axis held in place by rising upr
hgts to the E of slowly moving shrtwv in the nrn plains. Expect
incrsg mid/hi clds in this area with the arrival of some hier lvl
mstr. These clds wl hold down max temps. The far E wl be warmest
with max temps at least close to 70 as that area wl see more

Tonight...As the shrtwv moves slowly to the E and hgts fall slowly
over the CWA, the warm conveyor belt mstr ribbon is fcst to edge
slowly to the E as well. Incrsg upr dvgc/h85-7 mstr transport/deep
lyr qvector cnvgc with pwats incrsg up to about 1.5 inches /about
200 pct of normal/ wl support arrival of likely/categorical pops
over the W half. But there wl be a sharp ern edge to these hier pops
with lingering llvl dry air and weaker forcing over the ern CWA
closer to slowly departing rdg axis. Despite the deep moistening/
sharp dynamics, model fcst SSIs/unimpressive lapse rates support no
more than a shc of TS even under the deeper mstr/axis of hier pops.
With the clds/increasing mstr and steady S winds, tngt wl be much
warmer than early this mrng with lo temps probably not falling much
blo 60 in the downslope areas near Lk Sup over the W half of the

.LONG TERM...(Wednesday night through Tuesday)
Issued at 346 PM EDT TUE MAY 31 2016

Upper trough will be over northwest Ontario on Wednesday evening.
Sfc low associated with the upper trough will be just north of Lk
Superior with cold front working across central and eastern Upper
Michigan through the evening, perhaps triggering some showers and
thunderstorms as it moves through. Upper trough and Sfc low move to
James Bay Thursday afternoon. H85 thermal trough with plenty of low-
level moisture behind the system results in mostly cloudy and cool
conditions on Thursday. Temps will only struggle through the 50s near
Lk Superior and into the 60s inland. Low inversions and shallow cloud
depth and dry air blo cloud base should limit any potential for
showers. Some sprinkles could occur over east close to a weak sfc
trough moving through.

Sfc ridge crosses Thursday night into Friday as shortwave ridging
spreads across. Expect dry conditions but there may be stratocu or
cu as H85 thermal trough is slow to depart. Ridge overhead on Thu
night with light winds and possible partial clearing over west may
allow temps to fall into the upper 30s. Bias corrected GFS and GEM
showed that and went ahead and lowered mins over interiort west as
pattern certainly fits a cooler than guidance night. Trend is for
stronger shortwave trough and deepening sfc low to slide over Upper
Great Lakes on Friday into Friday night. Expect showers ro spread
over western Upper Michigan late Friday afternoon into Friday night
and across rest of cwa by late Friday night. Elevated instability
with this deepening system may promote some thunderstorms. Based on
sfc based cape and deep layer shear upstream and mid-upper level
steering winds and thicknesses may see situation where shra/tsra
roll in from MN or northern WI and in the evening and expand into an
MCS across much of Upper Michigan through the night. Far west cwa
may see risk for strong/gusty winds as 0-1km shear is over 20 kts
suggesting that at least initially the storms could be dominated by
cold pool interactions and thus have a chance of sustaining into that
part of the cwa. Overall though with limited instability across most
of cwa, biggest hazard likely will be heavy rain with PWATS to around
200 pct of normal and increasing low-level jet ahead of deepening
system. This is probably why models are showing widespread moderate
qpf over western cwa Fri night.

Extended...Upper trough crosses Upper Great Lakes on Saturday. Sfc
low will be over or just south of Upper Michigan. Unsettled for sure
with high chance of showers and possible thunderstorms. Clouds and
showers along with east to northeast winds will likely keep
temperatures from reaching 60 degrees over northwest cwa while rest
of area will be mainly in the 60s. Upper trough still close enough to
keep showers going through Sunday as well. NW winds restrict any
instability for thunderstorms to the south central. Upper trough
moves far enough away by Monday to keep the chance for showers only
over east half of cwa. Tue looks dry as brief ridging crosses Upper
Great Lakes region. Expect daytime high temps to remain below normal
through the period.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 149 PM EDT TUE MAY 31 2016

Lingering low-level dry air will ensure vfr conditions continue this
aftn at KCMX/KSAW. Vfr conditions should continue at KIWD as well,
but if passing shra affect the terminal, there may be some brief
mvfr conditions. As a more consolidated ribbon of shra slowly
spreads e across the area tonight/Wed morning ahead of a cold front,
expect conditions to deteriorate to at least mvfr at all terminals,
with some ifr as well. With an upslope southerly wind Wed morning,
KSAW is most likely to see ifr conditions. Behind the ribbon of
shra, KIWD/KCMX should break out to vfr Wed morning/early aftn. LLWS
will be possible tonight at KCMX/KSAW.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 427 AM EDT TUE MAY 31 2016

Expect NE winds today between hi pres over Hudson Bay and
approaching lo pres in the northern plains to peak as hi as 30 kts
over the western lake, where the gradient will be sharpest and
terrain funneling will accentuate the NE winds. Not out of the
question there could be a few gale force gusts to 35 kts in that
area. Expect the winds to veer toward the S later tonight into Wed,
when the lo pres will move into Ontario. Stronger SE to S winds up
to 30 kts tonight into Wed morning over mainly the E half will
diminish thru the day as a weaker gradient develops overhead.
Although the air over Lake Superior is dry now, expect fog to
develop W to E late today thru Wed as rain showers overspread the
area and the increasing SE to S flow advects more moisture into the
Upper Lakes. After the cold front associated with the low moving
thru Ontario passes Wed night into Thu, W winds up to 20-25 kts will
drag drier air over the Lake and dissipate the fog. Hi pres building
over the western Lakes late Thu into Fri will then bring a period of
light winds/quiet weather. More showers may arrive with the next lo
pres on Sat, but right now winds look to be no hier than about 20

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


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