357
FXUS63 KMQT 011719
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
119 PM EDT Wed May 1 2024

.KEY MESSAGES...

- Breezy west winds gusting up to 40 mph, mainly this afternoon.
- 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 347 AM EDT Wed May 1 2024

The well-advertised band of rain showers is lifting northeast across
the UP along a warm front extending east from a 1002 mb surface low
west of Duluth. Lightning is mostly absent from ongoing activity,
but there is a cluster of lightning/thunderstorms near Green Bay, WI
where SPC Mesoanalysis analyzed around 250 J/kg MUCAPE. Surface
observations across the UP show temperatures mainly around 40F
though there are mid-40s near the WI state line. Light east-
southeast winds advected moisture off Lake MI allowing low stratus
and fog to develop across east-central portions of the area where
clear skies occurred last evening. Increasing upper level clouds
make it difficult to see fog/stratus on RGB satellite imagery, but
several eastern UP surface observations indicate vsby at or below 1
mile.

Looking ahead through today, any lingering fog should diminish as
rain moves through this morning. Rain ends early this morning across
most of the west-central UP, but the Keweenaw and eastern UP will be
slower to dry out. The track of the low pressure remains low
confidence and has important implications for today`s wind
forecast. The most likely scenario is a surface low over
eastern Lake Superior by early afternoon with the associated
cold front passage already across most of the area. Despite very
dry mid-levels, model soundings indicate sufficient boundary
layer moisture for nearly continuous stratus or broken cumulus
that limits surface heating and mixing depth. This lowers
confidence in afternoon wind forecast, but EFI values of 0.7-0.9
and SoT >0 indicates unseasonably strong winds. EPS output and
sounding analysis suggests potential for westerly gusts to
around 40 mph especially across the south-central UP where mid-
level winds are stronger and downsloping west winds allow for
deeper mixing. Downsloping also boosts high temps into the low
60s across the south-central with 50s elsewhere except for 40s
on the Keweenaw. Across the eastern UP, west winds back Nwerly
this afternoon as the low pressure tracks over Ontario resulting
in a pseudo lake breeze/cool front that may force a shower or
two across the far east.

&&

.LONG TERM /TONIGHT THROUGH TUESDAY/...
Issued at 505 AM 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.

Beginning tonight, sfc high pressure ridge builds over the area in
the wake of the passing shortwave today. Result will be a dry, quiet
night, but lower level moisture/clouds from today will likely linger
tonight for many areas. Expect min temps ranging through the 30s F.
W half has best chc of seeing a decrease in cloud cover, so lowest
readings are expected in the traditional interior cold spots of the
w. Also, if it does clear out over the w, some radiation fog
could develop.

Attention then shifts to the next shortwave swinging across the
Rockies tonight and out over the Northern Plains on Thu. 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. Overall model trend has been to lower
cape avbl 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
w to e 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 w and later aftn across the e. 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 w, especially Keweenaw where
gusts to around 30mph should occur.

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 trends are toward a drier
scenario, and ensemble guidance only indicates a 20-30pct 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 w.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 119 PM EDT Wed May 1 2024

Expect the messy TAF conditions to continue the rest of today into
Thursday as conditions slowly improve to MVFR/VFR across the area
the rest of this afternoon. However, model guidance is hinting at
some FG developing over KSAW and KCMX tonight, which would bring
these terminals back down to LIFR again late tonight into Thursday
morning. As yet another low pressure moves towards Upper MI
Thursday, we could see rain showers move back over the area; this`ll
improve conditions across KCMX and KSAW back to MVFR by late
Thursday morning/near the end of the TAF period.

While LLWS isn`t expected, I`d say there`s around a 30% chance that
we could see some marginal low-level turbulence at KSAW and maybe
(lower chance) at KCMX as mixing may cease and cause a 20 to 30 knot
difference between the winds at the sfc and 2 kft aloft. However, as
the night goes on, the threat for it diminishes, becoming 0% after
midnight tonight.

&&

.MARINE...
Issued at 505 AM EDT Wed May 1 2024

Low pres will track e across Lake Superior today from near Duluth to
near Michipicoten Island. E to NE winds gusting up to 25-30kt are
expected in advance of the low. Attention then turns to eastern Lake
Superior to the e of the Keweenaw this aftn. As the low tracks to
near Michipicoten Island, westerly winds will increase to its s in a
corridor from the lee of the Keweenaw toward Whitefish Pt. Guidance
has trended weaker with the low pres, and thus the probability of
low end gale gusts is only 20-40pct, mainly running from near the
Huron Island to Grand Marais for about a 3-5hr period mid aftn to
early evening. High pres ridge arrives tonight, resulting in a quick
drop of winds to under 20kt across the lake. 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 pres 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.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Small Craft Advisory until 8 PM EDT this evening for LSZ245-
     246.

  Small Craft Advisory until 5 PM EDT /4 PM CDT/ this afternoon
     for LSZ241-242.

  Small Craft Advisory until 11 PM EDT this evening for LSZ243-
     244.

  Small Craft Advisory until 10 PM EDT this evening for LSZ247-
     248.

  Small Craft Advisory until 2 AM EDT Thursday for LSZ249.

  Small Craft Advisory until 8 AM EDT Thursday for LSZ250-251.

Lake Michigan...
  Small Craft Advisory until 8 PM EDT this evening for LMZ221-
     248-250.

&&

$$

SHORT TERM...EK
LONG TERM...Rolfson
AVIATION...TAP
MARINE...Rolfson