870
FXUS63 KMQT 020746
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
346 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
- Temperatures won`t stray too far from normal most days, but
  they will be above normal more often than below normal.

&&

.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 /THURSDAY THROUGH WEDNESDAY/...
Issued at 357 PM EDT Wed May 1 2024

Last 24hrs of medium range model guidance has maintained continuity
in showing that the recent active pattern across the Lwr 48 will
continue thru next week as a series of vigorous waves track off of
the N Pacific and then across the U.S. This pattern will be
beneficial in easing ongoing drought over western and eastern Upper
MI as frequent rainfall events are expected, some potentially mdt to
hvy. The latest drought monitor 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 overall above normal pcpn thru next week. As
for temps, with the progressive nature of the flow and frequent
shortwave passages, expect temps fluctuating around normal, likely
not straying too far from normal on most days, rather than any
prolonged periods of well above or well blo normal temps. Daily
temps will end up on the warm side of normal more often than the
cool side. Farther down the road, there are indications for a cooler
period mid month per recent EPS runs which show troffing/weak
negative height anomalies setting up over the Great Lakes region and
ne U.S. CFSv2 ensemble mean also supports a cooler period mid month.

After a dry and quiet night with ridging briefly overhead, an upper
low centered over the Rockies will begin to move into the Northern
Plains Thursday. In response, strong waa/isentropic ascent will
advance across the Upper Mississippi Valley to Upper MI Thu
aftn/night. Strong 850-700mb moisture transport is also noted with
precipitable water increasing to 200-250pct of normal. As a result,
expect shra to spread ne into Upper MI during Thu aftn, especially
across the w half. Shra will then continue across the area Thu
night. Rainfall amounts should be on the order of 0.25-0.50 inches.
Ensemble probability guidance indicates a 30-60pct chc of exceeding
0.50 inches, and only a 10-20pct chc of exceeding 1 inch. The
highest totals are now indicated mainly east of M-95, perhaps owing
to the proximity of the left-exit region of the LLJ being directed
over the area and lending some divergence aloft. Overall model trend
has been to lower cape available for parcels lifted from top of sfc based
inversion. So, potential of thunder has diminished.

On Fri, low pres will lift across western Lake Superior or ne MN
early in the day and then into northern Ontario. Shra will end from
west to east as associated cold or occluded front crosses the fcst
area late Thu night thru early Fri aftn. With sharp drying occurring
in the wake of the front, skies will trend mostly sunny early Fri
over the west and later aftn across the east. High temps will range
thru the 60s to lwr 70s F. Will be cooler near Lake Superior where
westerly winds are an onshore wind and also near Lake MI as a
southerly wind component will linger. Deepening mixed layer under
increasing insolation will lead to a breezy day mainly in the
western UP, especially across the Keweenaw where gusts to around
30mph should occur.  There is also a potential for dewpoints to mix
out fairly nicely, with RH currently forecast to drop into the lower
30s (and perhaps even the upper 20s) closer to the WI border in the
western UP. Given breezy conditions, this is worth monitoring for
any elevated fire weather risk. That said, as this will be
immediately following a round of decent rainfall, so fuels should be
moist.

Dry weather will continue Fri night. Then, next shortwave will
already be approaching by Sat aftn, resulting in a chc of shra
spreading west to east Sat aftn/night. Model trends are toward a
drier scenario, and ensemble guidance only indicates a 20-40pct
chance of rainfall exceeding a tenth of an inch. Fcst will only
reflect 30-40pct chc of shra Sat aftn/night.

In the wake of the shortwave, dry weather returns for Sun with sfc
high pres ridge arriving. Model agreement has notably improved for
dry weather to continue on Mon as a more amplified mid-level ridge
shifts over the area. While there is more uncertainty in timing
shortwaves beyond Mon as is typical at this time range, models have
trended toward better agreement. Next wave is likely to arrive Tue,
bringing the next round of shra in the ongoing active pattern. Shra
chc will continue on Wed as a potential mid-level low approaches
from the west.

&&

.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 357 PM EDT Wed May 1 2024

Low pressure is beginning to move east of Lake Superior this
afternoon, and though winds are turning calmer across western Lake
Superior, they should remain elevated across the eastern half of the
lake through this evening while shifting more to the west. Expect
wind gusts generally in the 20-25kt range before winds fall back to
around 5-10kts across the whole lake later tonight. Lighter winds
under 15kt will linger across eastern Lake Superior on Thu. Over
western Lake Superior, NE winds will be on the increase again on Thu
as the next low pressure moves out over the central Plains. Expect
NE winds up to 30kt by late Thu aftn over far western Lake Superior.
E to SE winds will increase up to 30kt over eastern Lake Superior
Thu night. Probability guidance indicates a 10-30pct chc of low end
gale gusts. As low pres lifts into northern Ontario on Fri, winds
will shift s to sw. While gusts up to 30kt will continue over
western Lake Superior, winds will fall off to under 20kt over the
eastern lake. Over the weekend, expect winds mostly under 20kt
across Lake Superior, then winds begin to pick up out of the E/SE
early next week.

&&

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

&&

$$

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