Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 220804

Area Forecast Discussion
National Weather Service Marquette MI
404 AM EDT Mon May 22 2017

.SHORT TERM...(This evening through Monday)
Issued at 407 PM EDT SUN MAY 21 2017

WV imagery and RAP analysis indicated a mid/upper level trough over
the cntrl CONUS with a low center over nrn MN. At the surface, low
pressure was located over far nw WI with an occluded front draped
eastward through srn Upper Michigan. Although most of the pcpn had
ended early this afternoon in the wake of the stronger shortwave
lifting through Lake Superior another weaker shrtwv was bringing
another area of light rain or drizzle through the wrn cwa.

Tonight, models suggest that sct -shra will increase gradually from
west to east as a shortwave over wrn MN slides toward the area and
additional wrap-around moisture filters into the area. However, any
rainfall amounts will be light with QPF of only a few hundredths of
an inch.

Tuesday, expect the greatest pcpn coverage over the east half in the
morning as the shrtwv moves through the area. Even with some drying
in the afternoon, diurnal heating, max readings into the mid to
upper 50s, with the mid level trough over the area may still be
enough to support some inland sct/isold -shra development.

.LONG TERM...(Tuesday through Sunday)
Issued at 401 AM EDT MON MAY 22 2017

No high impact weather on the horizon this week. Rainfall chances
stay frequent through midweek and there are additional chances
next weekend, but total amounts should stay below 1 inch into
next weekend. RH values could be low to end the week (maybe as
early as Wed aftn far west but most likely on Thu) but with the
recent wetter weather pattern and light winds expected, a dry day
or two should not too much concern for fire weather. As a sfc high
pressure ridge crosses area late in the week, may have one or two
nights where temperatures inland would be low enough to support
mention of frost.

Upper low over the region slides to Quebec on Tue while secondary
trough lingers over middle Conus to the western Great Lakes. At the
sfc, main sfc low will head to Quebec while weaker sfc low pressure
wave drifts across western Great Lakes then drops to the northern
Ohio Valley by Wed where lower heights in the mean trough focus by
that time. Still appears that a shortwave or two affecting region
along with sufficient moisture blo h7 could lead to scattered light
showers over mainly west half of Upper Michigan on Tue. Some of that
rain may also try to affect southern and eastern forecast area on
Tue night on northern edge of sfc-h85 low and in area of weaker
upper level forcing. Overall though the forcing in lower and upper
levels remains weak so not expecting much in way of rainfall Tue
through Tue night. GFS most aggressive with showers lingering over
east on Wed in area of mainly mid level moisture/forcing. Other
models have that idea but keep focus either south or east of eastern
forecast area. Consensus keeps chance low for now which is reasonable
given the model differences and overall weak forcing.

That trough will only slowly give way to ridging aloft by Thu,
though GEM and to certain extent ECMWF indicate slower departure of
the trough. Since sfc low should be well south or east of forecast
area think risk of additional precip will be low, though the GEM
which has stronger secondary upper low over Upper Michigan would
point to some precip for a few runs now. Since the GEM is outlier
with strength of the upper low kept pops only at slight chance.
Farther west over west and central forecast area better chance of
sfc ridge building across so lowered min temps more in line with
bias corrected guidance sets which show interior west seeing lows
Wed night at least down into the mid 30s if not lower 30s. With the
lower temps have a mention for frost that night. Sfc ridge sliding
across on Thu night could lead to another night with temps down
into the 30s inland and some frost.

Once upper level ridging arrives Thu night into Fri it will not stay
around long as large upstream trough over scntrl Canada Thu night
will already be spinning a shortwave toward the Upper Great Lakes as
early as Fri aftn. Mid clouds should increase west to east but with
warming h85 temps, raised highs into the low 70s over interior west
which is more in line with last couple runs of GFS MOS extended
(MEX) guidance. Main sfc low stays closer to upper trough but sfc
trough tied to the low swings across Upper Great Lakes on Fri
night. Kept consensus low chances for showers over the west half.
Could be tsra as well over west in the evening with SI/s falling
blo 0C. Best chance for tsra will be upstream during the aftn in
MN with some sfc based CAPE indicated during peak heating. Rest of
weekend looks unsettled with chances for showers and possible
tsra as upper level troughing with embedded shortwaves affect
region. Could be rain on Sat, but better chance for rain probably
end up later Sat into Sun as better defined sfc trough moves in
from the northern Plains and there is potential for stronger
shortwave to move through. &&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 145 AM EDT MON MAY 22 2017

Downslope flow will keep visibilities up overnight at all sites. Low
cigs though will continue at IWD and CMX with IFR/LIFR conditions
there. Drier air moving in Monday morning will help bring conditions
back to MVFR at both sites and to VFR by evening. With sw downslope
winds at SAW, this will keep MVFR conditions there through Mon
afternoon before VFR conditions develop.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 407 PM EDT SUN MAY 21 2017

Low pres moving across Lake Superior this evening will result in
diminishing winds and shift in wind direction from e-ne to w-sw late
tonight. Winds under 20 kts should then be the rule Mon into Wed as
a relatively flat pres gradient dominates the Upper Lakes.

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


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