Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 271850
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
250 PM EDT Wed Mar 27 2024

.KEY MESSAGES...

- Westerly lake effect snow continues tonight through Thursday
  evening, mainly across the Copper Country.
- Moderate to heavy lake effect snow and blowing snow is expected,
  mainly across the Copper Country through tonight.
- Heaviest snow amounts expected through tonight from Twin Lakes to
  Painesdale.
- Next chance of widespread precipitation occurs Friday night
  and Saturday, followed by a system worth monitoring for
  Monday/Tuesday next week.

&&

.UPDATE...
Issued at 1252 PM EDT Wed Mar 27 2024

More breaks in the clouds are apparent this afternoon with diurnal
instability leading to increased mixing. That, with some synoptic
support courtesy of the upper low over the area, is contributing to
widely scattered flurries and light snow showers across most of the
UP. WSW lake effect snow continues across portions of the western
UP, with a more prominent band off of the Bayfield peninsula
directed into the central Keweenaw peninsula. Snow totals there have
been bumped up slightly across northern Houghton county this
afternoon, but the band already is showing signs of washing out and
lifting more northward. Otherwise, the forecast remains on track.

&&

.SHORT TERM /THROUGH TODAY/...
Issued at 357 AM EDT Wed Mar 27 2024

Latest water vapor imagery and RAP analysis show a shortwave trough
lifting north of Lake Superior early this morning as another
shortwave and closed low circulation approaches from the eastern
Dakotas. The cold front tied to the sfc low lifting north of the
Upper Great Lakes moved through the area last evening and early
overnight as temps quickly dipped blo freezing. Some light scattered
snow shower activity has been observed behind the front as well.

Today, increasing CAA behind the front will continue to drop 850 mb
temps to -14C east to -16C west across Lake Superior. With Lake
Superior water temps 2-3C this cold air will be sufficient to
generate lake effect snow showers over the west wind snow belts.
Model soundings also show increasingly favorable snow growth as the
colder air will cause much of the mixed convective layer to
intersect the DGZ, allowing for fluffier dendrites to form which
will help boost snow totals. A mixed convective layer to only 7 kft
and an inversion sitting at around 5 kft will probably limit
accumulations to only an inch or two this morning, but conditions
look much more favorable for LES accumulation this afternoon as the
mid-level closed low over the Plains moves across the western fcst
area this afternoon and evening. Model soundings show inversions
lifting to 7-8kft and moisture deepening to near 15 kft in response
to the low moving over the area. Crosshair signature is also noted
in the model soundings with the best model omega/lift intersecting
the DGZ, maximizing snow growth. As a result, expect LES
accumulation to really take off this afternoon and evening. Have
snow accumutions increasing to 2-4 inches from 18Z-00Z across the
higher terrain of the west, especially from the Porcupine Mtns to
Houghton. Increased mixing from the colder air will also allow for
west winds to gust as high as 30-40 mph at times across portions of
the Keweenaw, exacerbating occasional whiteout conditions in blowing
snow.

With the greatest snow accumulation and wind/blowing snow concerns
through the event increasing across northern Houghton County
especially from Twin Lakes to Painesdale have decided to upgrade the
Winter Weather Advisory there to a Winter Storm Warning from this
afternoon through tonight. High-end advisories will remain in place
for Ontonagon and Keweenaw counties this afternoon into tonight.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Issued at 249 PM EDT Wed Mar 27 2024

Medium range guidance continues to handle the overall theme in the
extended forecast period well, presenting a consistent picture of
the main features in play going into the weekend. Starting off on
Thursday, the mid-upper level low that`s been responsible for the
snow and rain these past few days will continue its northeastward
exit toward James Bay while increasing anticyclonic flow and ridging
builds across the Plains. At the surface, high pressure will press
into western Wisconsin through the day, helping to pull in dry air
and subsidence that will result in diminishing lake effect snow
activity for the west wind snow belts. While the trend will be
decreasing activity, another inch or two of snow should be expected
in the Copper County, with the highest amounts being along the Spine
of the Keweenaw. Elsewhere, mostly dry conditions are expected.
Daytime highs should climb into the 30s, maybe near 40F for the
southern portions of Menominee County. The dry conditions will
persist overnight and Friday. Overnight lows should be mostly in the
teens interior west and low to mid 20s elsewhere. Daytime highs
Friday should top out in the 40s except mid to upper 30s near Lake
Superior and in the Keweenaw.

During the day on Friday, the mid-level ridge axis will shift
through the region as a surface low organizes in the Central Plains
and a northern stream shortwave presses through the Northern Tier
along the international border. As these features move into the
Upper Great Lakes, precip will move into the forecast area. Timing
among the various guidance packages suggest increasing precip
chances Friday evening that should persist through Saturday as the
surface low lifts through southern Lake Michigan and southern Lower
Michigan and the attendant inverted trough moves through Upper
Michigan. Precip type appears to be a mix of rain, snow, and maybe,
freezing rain, at least early on. As the event progresses through,
warm nose feature around 2-3k feet should break down as weak cold
air advection sets up. This should help any precip transition over
to rain or snow. Precip should come to an end Saturday evening,
followed by a dry Sunday thanks to another surface high moving
through the region.

Attention then shifts to a the potential interaction of a trough
exiting the Rockies and shortwaves dropping out of Canada. Model
trends with this system appear to be moving south and there is a
general trend toward potential phasing with a shortwave late Monday
and Tuesday. GEFS and EC ensemble systems continue to suggest weak
clustering of their membership and both their ensemble means move
the surface low near southern Lake Michigan and into southern Lower
Michigan. The same ensemble systems suggests the greater probability
of moderate QPF being near the ensemble means. This suggests a
significant precipitation event/snow event is becoming less likely,
but certainly continues to warrant monitoring in the coming days.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 131 PM EDT Wed Mar 27 2024

Lake effect snow showers continue at IWD and CMX this afternoon,
with MVFR ceilings and IFR visibility expected the rest of today. A
heavier band directed into the Keweenaw this afternoon is even
leading to visibility below a mile at times, which may bring
occasional LIFR restrictions at CMX. IWD should slowly improve
overnight as lingering LES mainly north of the area, with a return
to VFR into early Thursday. CMX, meanwhile, should stay at IFR
overnight before an improvement to MVFR into early Thursday. SAW has
seen some hit and miss snow showers this afternoon, which should
continue into tonight, but restrictions are not expected with just
some lower level stratocumulus. Otherwise, expect blustery WSW winds
the rest of today through tonight, with gusts up to 20 to 30 knots.

&&

.MARINE...
Issued at 249 PM EDT Wed Mar 27 2024

Strong, mostly westerly and southwesterly winds will persist this
afternoon and evening as a surface low slowly pulls away into Hudson
Bay, leaving behind continued lake-induced instability and modest
pressure gradient forces thanks to high pressure building in across
the Plains. Expecting today`s low end gales to lighten through the
night as these forces begin balancing, but given the persistent
colder airmass aloft, near 30kt gusts should be expected at least
through Thursday. The colder airmass and wind will also make
freezing spray accumulation possible, although the trend to weaker
winds should reduce the risk through late tonight into Thursday. No
changes were made to the current gale warnings. Winds lighten to
around 20kts or less Thursday night, then remain light going into
the weekend.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until 8 AM EDT Thursday for MIZ001-002.

  Winter Storm Warning until 8 AM EDT Thursday for MIZ003.

Lake Superior...
  Gale Warning until 11 PM EDT /10 PM CDT/ this evening for
     LSZ162-241>244-263-264-266.

  Small Craft Advisory until 8 AM EDT /7 AM CDT/ Thursday for
     LSZ240-249.

  Small Craft Advisory from 11 PM EDT /10 PM CDT/ this evening
     to 8 PM EDT /7 PM CDT/ Thursday for LSZ241>244.

  Gale Warning until 5 PM EDT this afternoon for LSZ245>248-265.

  Small Craft Advisory until 2 AM EDT Friday for LSZ250-251.

Lake Michigan...
  Small Craft Advisory until 2 AM EDT Thursday for LMZ221-248-
     250.

&&

$$

UPDATE...
SHORT TERM...Voss
LONG TERM...JTP
AVIATION...LC
MARINE...JTP


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