Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 211133
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
733 AM EDT Mon Sep 21 2020

.SHORT TERM...(Today and tonight)
Issued at 427 AM EDT MON SEP 21 2020

Latest RAP analysis show a mid-level ridging extending from the
western Great Lakes to northern Ontario. Heights are beginning to
slowly fall as a mid-level low, seen at 500mb, over southern
Manitoba is shifting towards southern Ontario and may scoot along
the northern Lake Superior as the morning goes. In response to this
mid-level low, it has triggered some light rain showers over the far
western UP. However with drier air aloft, most of these rain showers
haven`t reached the ground. We`ll see if this trend continues but
for now, capping PoPs at only slight chance if anything does reach
the ground.

With the mid-level low approaching the area, latest sfc analysis
show a warm front, which could also aid in triggering some light
rain showers. 850mb theta-e ridge/theta-e advection is accompanying
with the eastward low-level jet along with some limited mid-level
instability available for parcels lifted from above the stable sfc
based layer and some fgen as well, may still be sufficient to
generate some isolated showers this afternoon and into the evening
so to show this, capped PoPs at this time to slight chance to slight
in some spots. Cannot rule out an isolated rumble of thunder, given
the limited instability in the 1-3km layer but not worthy of putting
it in the forecast since probability of thunder occurring is pretty
low. Any lingering precip will end by early Tuesday morning with
clearing behind it.

Breezy conditions will continue thanks to the ongoing pressure
gradient with high pressure near New England and a low pressure
tracking towards the Hudson Bay with Upper Michigan in between them.
Gusts will be between 25-35 mph with highest gusts near the Lake
Superior shoreline with the downsloping winds. Otherwise, expect
highs in the upper 60s to mid 70s with warmest spots over the west.
Lows tonight will be a bit warmer with 50s across Upper Michigan.

.LONG TERM...(Tuesday through Sunday)
Issued at 410 AM EDT MON SEP 21 2020

Near zonal flow pattern will start off the long term with slight
ridging and height rises on Tuesday. With high pressure over the
central Appalachians, WAA and southwesterly winds will allow for
daytime highs to climb into the mid-upper 70s. Overnight lows should
fall into the upper 40s in the interior and low 50s by the
lakeshores.

The warm conditions will continue on Wednesday ahead of an
approaching shortwave from the west with highs again climbing into
the mid-upper 70s. As this shortwave moves in and swings a cold
front through Wednesday night into Thursday, expecting showers to
move in from the west Wednesday evening. Instability varies by
model, but the progged 500-1000 j/kg within a 30-40kt deep shear`d
environment should be enough for a few thunderstorms. Following this
system`s cold frontal passage Thursday, 850mb temps should fall to
~10-12C, which should allow for surface temps to top out in the
60s.

On Friday, the ridge over the southwestern CONUS is progged to
broaden out and shift eastward over the Upper Great Lakes. Height
rises and advection of another warm airmass will allow for temps to
rebound back into the 70s. This weekend, as this ridge continues
east and amplifies over the eastern US, deep troughing should settle
in over the Plains. This will bring the region a good shot for more
rain showers with maybe some thunderstorms as the trough shifts into
the Upper Great Lakes and swings a cold front through the region.
Beyond this, guidance differs on this trough`s evolution and the
amount of colder air that will filter south. If you believe the EC,
some well below normal temps to look forward to by the middle of
next week. This contrasts well with the GFS` slightly below to near
normal progs.
&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 732 AM EDT MON SEP 21 2020

VFR conditions will prevail thru this TAF period at KIWD/KCMX/KSAW.
There could be an isolated shower that may get close enough to KIWD
later this afternoon but since given current airmass is pretty dry,
decided not to include VCSH in the TAF at this time. Winds will
remain gusty into the evening before gradually diminishing heading
into Tuesday. Newer guidance wasn`t too keen on LLWS occurring
tonight since winds won`t be as gusty. However, there could be a few
hours at KSAW where LLWS could occur but confidence to include in
TAF was low, so left it out for now.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 427 AM EDT MON SEP 21 2020

With Lake Superior being in between high pressure over New England
and low pressure over the Dakotas, this will continue to bring gusty
southerly winds today. As with southerly winds, the strongest winds
will occur mainly over the e half of Lake Superior. Some gale gusts
to 35kt will be possible at high obs platforms and the nearshore
zones east of Marquette. Winds will diminish tonight into Tuesday,
falling to under 15 kt. Winds could get up to 20kt on Thursday from
the east-northeast due to a passing front before turning southerly
and increasing up to 25kt for Friday and Saturday.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement through this evening for MIZ014.

Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...JH
LONG TERM...JP
AVIATION...JH
MARINE...JH


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