Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 122341

Area Forecast Discussion
National Weather Service Marquette MI
741 PM EDT Wed Aug 12 2020

.SHORT TERM...(This evening through Thursday)
Issued at 328 PM EDT WED AUG 12 2020

Outside of a few passing mid-level clouds, Upper Michigan remains
mostly clear this afternoon with temperatures climbing into the 80s
for most. A developing Lake Superior lake breeze continues to
develop and push inland, as temperatures behind this breeze have
fallen back into the 70s. Remnant convection across MN is throwing
some convective-induced cirrostratus clouds across the far western
half of the cwa over the last few hours, and will continue to move
eastward into this evening.

Tonight, a little bit of a change from the going forecast as latest
run of CAMs and models suggest a convectively-induced passing shrtwv
will bring a round of shra and iso tsra across western Lake Superior
and far western Upper Michigan. Was a little skeptical on coverage
and eastern extent given drier air and high pressure ahead of
shrtwv, but through in some slight to chance PoPs, mainly west of a
line from Big Bay to Watersmeet. Additionally, models suggest this
wave to outrun supporting instability and forcing that lingers
behind it across MN. With these increasing clouds, increased lows
tonight a few degrees from going fcst, falling to either side of
60...60s along Lake Superior and upper 50s inland.

Tomorrow, weak WAA and increasing theta-e across the far west will
help increase moisture and dewpoints across the western half of the
UP. High pressure ridging extending westward from Canada will allow
the east half of the UP to remain a little drier, while model
soundings support this idea as well. Convection over MN is expected
to diminish as it advected eastward over Lake Superior. Highs will
climb into the 80s again, similar to this afternoon.

.LONG TERM...(Thursday night through Wednesday)
Issued at 343 PM EDT WED AUG 12 2020

A shrtwv ridge will move out to our east Thursday night and Friday
as a longwv trough moves through the area from Friday to Sunday,
bringing showers and thunderstorms to Upper Michigan as it slowly
passes. Behind the longwv, temperatures will drop from above
normal to near or below normal as CAA brings in cooler, drier
Canadian air. More details for the forecast follow below.

Thursday night and Friday, the Hudson Bay high begins to move out
east as a longwv trough slowly follows behind it, dragging a shrtwv
trough through NE Minnesota. PWaTS have 2 std anomalies over NE
Minnesota/N Ontario, and IVTs show moisture from the PacNW and
strained moisture from Gulf (due to the Gulf moisture being
partially blocked by a low over the Ohio River Valley) enhancing
convection near NE Minnesota. CAPE and wind shear values seem to
support the idea of some strong storms being possible over NE
Minnesota Thursday night into Friday, with CAPE values getting to
2500 J/kg and wind shear reaching 30+ knots. However, these values
drop off quickly near Lake Superior. Therefore, although some
storms, with a few possibly becoming strong, will probably form
over far western Lake Superior, there shouldn`t be a concern for
severe weather Thursday night and Friday for Upper Michigan as
convection should be suppressed by the anomalous high pressure
shrtwv over our area. There may be a stray shower or thunderstorm
over the west, but that should be about it if convection was to
occur over Upper Michigan. So, save for the possibly strong
thunderstorms over the far western lake Thursday night and
Friday, there shouldn`t be any hazardous weather that needs to be
considered. This high pressure ridge will also keep temperatures
above normal as it will keep warm air (15-20 C at 850mb) near the
Upper Peninsula.

Friday night into Sunday, the longwv trough will bring a cold front
through the area. This front should drop the temperatures each day
as the front slowly moves through the area from west to east. A
decrease in the PWaT anomalies show that the amount of moisture from
the PacNW and Gulf for this system is decreasing with time. Also,
CAPE values are also not as nearly as impressive when compared to NE
Minnesota Thursday night and Friday; model guidance has CAPE only
getting to 2000 J/kg at most in a few spots, mostly during the
afternoon Saturday. Wind shear shouldn`t be hindered though, as
values look to remain near 30 knots. Therefore, it seems that as the
front travels through the Upper Peninsula over the weekend, showers
and thunderstorms will diminish and weaken as the front makes its
way east, making severe weather unlikely. Temperatures should
drop closer to normal with each passing day, as the small
positive temperature anomaly vanishes as the front moves through.

The early part of the workweek next week should see drier and cooler
conditions as a Canadian airmass makes its way over the Upper
Peninsula. A stray shower or two is not out of the realm of
possibility, especially if the front moves slower than expected over
the weekend. However, the beginning of the workweek should be
relatively dry as a high pressure ridge moves over the western
Plains; CAA will also help to keep things dry, as it will suppress
convection through subsidence. Temperatures may get anomalously
cool, especially Monday and Tuesday, as that is when the CAA looks
to be strongest (hinted at by the ENS and NAEFS). Temperatures
appear to be near normal for Wednesday.

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 740 PM EDT WED AUG 12 2020

With relatively dry low-level air mass to remain over the area,
expect VFR conditions to prevail at KIWD/KCMX/KSAW thru this fcst
period. A disturbance moving across the area tonight, may generate a
some shra that will affect KIWD and perhaps KCMX. Not expecting
conditions to fall out of VFR if a shra occurs.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 328 PM EDT WED AUG 12 2020

Convection ongoing across MN this afternoon will pass over western
Lake Superior tonight, as winds gust up to around 20 knots from the
SE. Winds fall blo 20 knots again for Friday before increasing up to
20 knots again on Saturday from the south ahead of an approaching
trough and cold front. Another cold front is progged to move over
the lake during the start of next week, which may bring winds to
around 25 knots from the NW.

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


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