Area Forecast Discussion
Issued by NWS Marquette, MI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KMQT 260021
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
821 PM EDT Mon Mar 25 2024

.KEY MESSAGES...

- Temperatures will climb above freezing this afternoon and stay
  that way overnight with periods of rain.
- A cold front passing Tuesday will bring rain turning to snow
  with a period of mixed precipitation possible. Rapid cooling
  behind the cold front may result in a flash freeze with
  untreated surfaces possibly becoming icy late on Tuesday.
- Westerly lake effect snow develops early Wednesday morning and
  continues through Thursday evening, mainly across the Copper
  Country.
- Next chance for widespread precipitation comes into the
  weekend, but confidence is low.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 258 PM EDT Mon Mar 25 2024

Early afternoon water vapor imagery shows a deep trough centered to
the lee of the southern Rockies with ridging over the Northeast.
Deep moisture plume is advecting into the upper Great Lakes on
strong southwesterly winds in between these two features, downstream
of a strong shortwave trough pushing into eastern MN. Good
isentropic lift is continuing over the local area, and the arrival
of the deeper moisture is coincident with the regional radar filling
back in. Cold air has been slow to dislodge thus far over the north-
central and northwestern UP where p-type remains snow; however, p-
type just changed back to rain here at NWS MQT and the rain/snow
line should continue progressing northward through the afternoon due
to a combination of warming aloft and at the surface. This should
result in travel conditions continuing to become less hazardous, so
the winter weather headlines were allowed to expire at 18Z.

Periods of rain will continue through the night tonight as
isentropic lift continues due to a strengthening low-level jet in
the northeast quadrant of a surface low approaching from the
southwest. Temperatures should continue to rise and should remain in
the mid-30s to low 40s through the night, so travel impacts and
frozen precip are not anticipated. Rainfall totals are likely to be
in the 0.5-1.00 inch range through 12Z Tuesday, with some spots in
the Keweenaw possibly exceeding an inch due to the orographic
component of the southeasterly low-level winds interacting with the
terrain. Some ponding of water on roadways is possible. Dewpoints
rising into the mid and upper 30s over the snowpack could result in
some areas of fog especially over the interior west where winds will
be lighter, but overall, decent gradient winds should keep fog from
being too dense or widespread.

&&

.LONG TERM /TUESDAY THROUGH MONDAY/...
Issued at 334 PM EDT Mon Mar 25 2024

The feature of note beginning Tuesday morning is a mature 988mb low
(per 12Z GEFS mean) transiting from northern Wisconsin across the
western UP to north-central Lake Superior and eventually northern
Ontario by Tuesday night. This low will bring a myriad of precip-
types as it passes and gusty winds in its immediate wake. Cool air
behind the low will support Werly to WSWerly LES into Thursday.
While the remainder of the UP will be dry in the end of the week,
the heavy precipitation to begin the week will keep most fire
weather concerns at bay. While precip rates at times may exceed
0.75"/day, persisting drought conditions should limit hydro concerns
significantly. The next chance for widespread precipitation
will come late Friday into the weekend, but model spread is
still high and confidence is low.

Two prominent 500mb troughing features are over central North
America at 12Z Tuesday. The first is a potent shortwave primarily
responsible for the sub-990mb low that will pass over the UP Tuesday
following roughly the same track. The other is a longer wave which
will phase with the shortwave Wednesday and the trough will pivot
around northern Ontario through Thursday. For Tuesday, potent warm
southerly flow will bring morning temperatures into at least the mid-
40s. The NBM 25th-75th percentile range is disappointingly large for
such a short time period, with 25th percentile highs in the upper
40s to low 50s and the 75th percentile is pushing 60, displaying the
large spread in the ensembles regarding the timing of the passage of
the cold front. Regardless of exact values, cooling behind the front
is going to be strong, with 12Z GFS 850mb cold advection rates of up
to -50C/12 hr. This translates into surface temperatures broadly
falling 2-3C/hr, which the WSSI is highlighting as a minor to
locally moderate flash freeze threat. This cooling will also
complicate the precip types in the evening and overnight hours, with
a messy transition from rain to a wintry mix to snow expected. The
12Z HREF does highlight the Ironwood to Ontonagon area as having up
to 50% chance of a glaze of freezing rain accumulation, but the
potential for flash freeze conditions is still expected to be the
primary driver of slick road conditions. Once the transition to snow
occurs, a slushy inch of snow widespread is most likely, but this
also depends on the timing of the arrival of the cold air behind the
front. Whether it falls as solid or liquid, QPF totals will be
highest along the Keweenaw and in the east half, with the central UP
most likely to be under the influence of a dry slot which will limit
precipitation. 12Z HREF probability of exceeding 0.5 inches is 20-
50% along the Keweenaw and 50-90% in the east, with about a 50%
chance of seeing 0.75 inches of QPF around Newberry. No hydro
impacts are expected due to the current drought conditions.

Once synoptic precip departs early Wednesday, the strong surge of
cool air will allow for lake effect snow to develop as 850mb
temperatures fall into the -10 to -15 C range. As the 500mb trough
will be pivoting near the northern shores of Lake Superior Wednesday
into Thursday, the boundary layer winds will be primarily Werly to
WSWerly. EPS mean wind gusts over the Keweenaw are in excess of 40
mph Wednesday, which has a 10-20% chance of a blowing snow threat to
reduce visibility and cause drifting. LES falls off significantly
Thursday as surface ridging builds in with a more dry airmass. The
NAEFS shows PWAT values falling to below 0.25 across the UP and NBM
RHs fall to the 30s Thursday in the interior west, though with the
heavier precipitation from earlier in the week, fire weather
concerns are minimal.

The next chance for precipitation comes late in the week. The
Canadian and GFS bring a shortwave across the Upper Great Lakes over
the weekend, though the Euro has ridging prevailing. GEFS MSLP
clusters show surface low pressures mainly staying south of the UP
but a small cluster does transit near the region. The EPS keeps all
potential low pressures south of the UP, so confidence in this
potential precipitation is low. The GEFS has good confidence that
high pressure will be over northern Ontario to begin next week with
a cluster of members showing a Colorado Low developing and ejecting
northeast sometime for the middle of next week, but confidence in
any solution rapidly drops off in that time period.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 820 PM EDT Mon Mar 25 2024

Ptypes are ranging across the TAF sites from snow at CMX to rain at
SAW and some fluctuation between rain and snow at IWD.  By Tue 06Z
though, precipitation should be transitioned to mainly rain at all
TAF sites.  So, poor flying conditions will continue with LIFR being
the predominant flight category at CMX and SAW.  IWD, however,
should trend more toward IFR.  Little improvement is expected
through this TAF period with IFR and MVFR at best at CMX/SAW and
IWD, respectively, by early Tuesday afternoon. Meanwhile, will
carry a LLWS threat at SAW from now through tomorrow morning and
at CMX starting around Tue 11Z as a strong low level jet enters
the area.


&&

.MARINE...
Issued at 334 PM EDT Mon Mar 25 2024

A large and deep area of low pressure tracks northeast toward Lake
Superior tonight then across the lake on Tuesday. This results in a
complex marine forecast with multiple periods of gales from a
variety of directions within both stable and unstable flow regimes.
Easterly gales will overspread the lake by tonight to 35-40 kt.
Winds become more cyclonic and low level stability increases as the
low approaches the lake tonight. Increasing stability lowers
forecast confidence in gale potential, especially across the eastern
lake where the warmest temperatures are forecast. However, low-end
35 kt southeast gales over the eastern lake and northeast gales to
around 40 kts over the western lake appear most likely. As the low
tracks northeast across the lake on Tuesday it drives a cold front
eastward with strong cold air advection resulting in deep mixing. A
period of westerly gales is likely (60-80%) for Tuesday night and
Wednesday. Westerly gales should diminish Wednesday night with winds
subsiding below 20 kts Thursday night. In addition to the wind, wave
heights through Tuesday will mainly be 8-12 ft with some 12-14 ft
waves east of Isle Royale and north of the Keweenaw Peninsula. Waves
fall below 8 feet by Thursday afternoon. A period of moderate heavy
freezing spray is also expected across the lake after the cold front
passes late Tuesday through Wednesday.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning until 5 PM EDT /4 PM CDT/ Tuesday for LSZ162.

  Small Craft Advisory until 8 AM EDT /7 AM CDT/ Wednesday for
     LSZ240-245>248.

  Small Craft Advisory until 2 PM EDT /1 PM CDT/ Tuesday for
     LSZ241>243.

  Gale Warning from 2 PM EDT /1 PM CDT/ Tuesday to 8 PM EDT /7
    PM CDT/ Wednesday for LSZ241>243.

  Gale Warning until 8 PM EDT Wednesday for LSZ244-263-264.

  Small Craft Advisory from 2 AM Tuesday to 8 AM EDT Wednesday
     for LSZ249-250.

  Gale Warning until 2 PM EDT Tuesday for LSZ251-266-267.

  Small Craft Advisory from 2 PM Tuesday to 8 AM EDT Wednesday
     for LSZ251.

Lake Michigan...
  Small Craft Advisory until 8 AM EDT Tuesday for LMZ221-248-250.

  Gale Warning from 8 AM to 2 PM EDT Tuesday for LMZ221-248-250.

&&

$$

SHORT TERM...Thompson
LONG TERM...GS
AVIATION...TDUD
MARINE...EK/GS


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.