063
FXUS63 KMQT 020902
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
502 AM EDT Thu May 2 2024

.KEY MESSAGES...

- Active pattern continues through next week as a series of low
  pressure systems track across the U.S. and affect Upper MI.
  Above normal precipitation expected, including chance of
  thunderstorms at times.
- Mostly above normal temperatures expected, generally 5 to 10
  degrees above normal on the majority of days through the
  middle of next week.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 346 AM EDT Thu May 2 2024

Upper Michigan is between two systems tonight with 500 mb ridging
resulting in mostly clear skies and efficient radiational cooling.
RGB composite satellite imagery shows low clouds across the far east
and mid/upper level clouds to our southwest with clear skies across
most of the CWA. Light anticyclonic winds and clear skies have
allowed temps to tumble well below afternoon dew point values with a
handful of sites at or below 35F even all the way to the lakeshores
in a few spots. Iron Mtn and the Sault have reported fog and RGB
imagery suggests implies some in the Michigamme Highlands too, but
observed visibilities have been greater than a mile so far.
Continued nocturnal cooling may allow for increased coverage or
intensity of patchy fog, but mid-level clouds are beginning to move
over our coolest locations so decided to leave fog out of the
forecast for now.

Looking ahead through today, the primary forecast challenges are
related to cloud/precip trends with latest model guidance indicating
a slightly earlier arrival of both. This feeds back onto high temps
that are coming in a few degrees cooler than the previous forecast
and now appear warmest ~60F across the east where cloud cover should
arrive latest. HREF guidance brings the first measurable precip into
locations adjacent to Wisconsin between 17-19Z (1-3 PM CDT)
this afternoon then to a line between Houghton, Marquette, and
Escanaba between 19-21z (3-5 PM CDT). Generally tried to mimic
that timing in going forecast, but rain may struggle to move
over the eastern UP until tonight.

&&

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
Issued at 458 AM EDT Thu May 2 2024

Last 24-48hrs of medium range model guidance maintains an active
pattern across the Lwr 48 thru next week as a series of vigorous
waves track off of the N Pacific and then across the U.S. Late next
week into the mid month period, it appears this pattern will
breakdown. The active pattern will be beneficial in easing ongoing
drought over western and eastern Upper MI as frequent rainfall
events are expected. An updated drought monitor will be issued this
morning, but the last one from 4/25 indicated drought conditions in
western Upper MI were into the severe category in portions of
Gogebic/Ontonagon counties. To the e, moderate drought was indicated
from eastern Delta to western Mackinac counties. The frequent pcpn
events will also ease spring fire weather concerns. So, expectation
is for pcpn from now thru the end of next week to be above normal
for most areas of Upper MI. As for temps, with the progressive
nature of the flow and frequent shortwave passages, no prolonged
periods of well above normal or well blo normal temps will occur.
Instead, expect some fluctuation in temps, but mostly around normal
to above normal. Majority of days will be above normal, generally 5-
10 degrees above normal. Farther down the road, there are still
indications for a cooler period mid month, probably beginning late
next week, per recent EPS runs which show troffing/weak negative
height anomalies over the Great Lakes region and ne U.S. There is
also consistency in recent CFSv2 ensemble means showing a cooler
period mid month. Don`t know much about the strengths/weaknesses of
the ECMWF AI machine learning model yet, but it has had a run-to-run
signal for a chilly period generally around May 15 with 850mb temps
down toward -4C over Upper MI.

Beginning tonight/Fri, vigorous shortwave over eastern SD this
evening will reach western Lake Superior Fri morning and will be
approaching Hudson Bay Fri evening. Main surge of waa/isentropic
ascent and strong 850-700mb moisture transport advances across Upper
MI this aftn/evening, providing the period of more widespread shra.
There isn`t much cape for parcels lifted from top of sfc based
inversion. Most guidance is less than 200j/kg, but a few models show
spotty up to 300j/kg. Might be a few rumbles of thunder. Occluded
front associated with shortwave will reach western Upper MI around
06z, will extend roughly thru Munising to Manistique by 12z Fri and
will exit Luce County around 15z. Shra will abruptly end with its
passage as sharp mid-level drying surges into the area. Lower levels
will dry out quickly as well on Fri as daytime heating builds mixed
layer and taps very dry air aloft. Expect skies to trend sunny Fri
morning over the w half and early to mid aftn across the e. However,
weaker wind fields over the e and resulting lake breeze development
may end up allowing lower clouds to persist there thru the aftn, at
least closer to the Great Lakes, especially if widespread fog
develops over the Lakes with the rainfall this aftn/tonight. Expect
high temps on Fri ranging thru the 60s F, even lwr 70s F portions of
interior w to central. Will be locally cooler along the Great Lakes.
Over the w interior, deepening mixing will support dwpts tumbling to
around 30 or even upper 20s F, resulting in RH falling to 20-30pct.
Fcst soundings also support gusty westerly winds to 25-30mph. Even
though there will be gusty winds, warm conditions and low RH, recent
rainfall, including this aftn/tonight, will work to limit fire wx
concerns on Fri.

Dry weather will continue Fri night. Then, next shortwave will
already be approaching by Sat aftn, resulting in a chc of shra
spreading w to e Sat aftn/night. Model spread is high with some
models show nothing more than spotty pcpn while others are more
widespread. Ensemble guidance doesn`t show much more than a 10-30pct
chc of rainfall exceeding a tenth of an inch. Better chc of pcpn
will be over the western fcst area as upper diffluence from right
entrance of sw-ne oriented upper jet will pass across that area
before weakening as it shifts e. Fcst will only reflect a 20-40pct
chc of shra spreading w to e Sat into Sat evening.

In the wake of the shortwave, dry weather returns for Sun with sfc
high pres ridge arriving. A model trend that showed up 24hrs ago for
Mon has been locked onto as models solidly agree on a more amplified
mid-level ridge over the Upper Great Lakes on Mon. So dry weather
will continue on Mon as well. For the time range, agreement is good
for the next shortwave swinging out of the Rockies on Mon to result
in a mid-level low over the Dakotas for Tue. In response,
strengthening waa/isentropic ascent will spread toward Upper MI late
Mon night/Tue, supporting shra spreading into the area late Mon
night/Tue morning. Anchored by the mid-level low, mid-level troffing
will then expand across the Rockies and Plains to Great Lakes during
the midweek period, resulting in additional shortwaves tracking thru
the trof to the Upper Great Lakes. Thus, expect more opportunities
for shra Tue thru Thu.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 148 AM EDT Thu May 2 2024

VFR conditions continue at all terminals into Thu afternoon before
an approaching system brings lowering cigs and vsby restrictions in
rain showers. Cigs lower to IFR this afternoon then to LIFR at CMX
and IWD this evening and potential exists at SAW too, but confidence
was too low at this time. SAW may also have fog and low cigs around
sunrise before improving this morning. Rain then moves into SAW by
the evening and conditions go to IFR.

&&

.MARINE...
Issued at 458 AM EDT Thu May 2 2024

Winds have fallen to under 15kt across Lake Superior during the
night. These lighter winds under 15kt will linger across eastern
Lake Superior today. Meanwhile, over western Lake Superior, NE winds
will be on the increase again as the next low pressure lifts toward
the Upper Mississippi Valley. Expect NE winds up to around 25kt by
late aftn over far western Lake Superior. E to SE winds will
increase up to 25kt over eastern Lake Superior tonight. Probability
guidance only indicates about a 10pct chc of low end gale gusts for
this event. As low pres lifts into northern Ontario on Fri, winds
will shift sw. While gusts up to 25kt will continue over western
Lake Superior, winds will fall off to mostly under 15kt over the
eastern lake in the afternoon as winds back around to the se. Over
the weekend, expect winds mostly below under 20kt across Lake
Superior under a relatively weak pres gradient. High pres that
arrives over the Upper Great Lakes late weekend will shift e on Mon
while a deep low pres emerges over the western Dakotas. This will
result in increasing easterly winds Mon into Tue. Expect winds up to
30kt by Tue.

With showers moving across Lake Superior this aftn and tonight, some
fog will likely develop, and it could become locally dense. Fog will
push mostly to Canadian waters for Fri due to the sw winds. If the
fog does not clear off of the lake on Fri, it may expand back across
eastern Lake Superior during Fri aftn as winds back to the e to se.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...EK
LONG TERM...Rolfson
AVIATION...07/EK
MARINE...Rolfson