Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 242053
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
353 PM EST Wed Feb 24 2021

.SHORT TERM...(This evening through Thursday)
Issued at 351 PM EST WED FEB 24 2021

WV imagery and RAP analysis indicated mid/upper troughing from
Hudson Bay into the north Central CONUS. The shortwave and sfc low
that brought snow through Upper Michigan early today has departed
toward Quebec leaving clearing skies as drier air moves in on nnw
winds. An upstream shrtwv into southern Manitoba and its weak sfc
reflection supported sct -shsn into eastern ND and northwest MN.

Tonight and Thursday, expect a period of mostly clear skies this
evening that will give way to increasing clouds overnight as the
Manitoba shrtwv approaches the area. Favorable radiational cooling
before the clouds arrive will allow temps to drop into the single
digits inland with teens near the Great Lakes. Sct -shsn will move
into the west late tonight. Ice cover on Lake Superior will be
patchy enough so that 850 mb temps to around -13C along with
convergent westerly winds will aid the snow showers. Given the
marginal instability and forcing from the shrtwv, Any snowfall
amounts should remain light, generally less than an inch. Diurnal
heating may also boost the -shsn as the shrtwv moves through the
central and east into the afternoon. Highs should climb to around 30
north and the low to mid 30s south.

.LONG TERM...(Thursday night through Wednesday)
Issued at 339 PM EST WED FEB 24 2021

The long-term period looks active with a lot of back-and-forth in
temperatures and multiple snow chances, but at the moment, no
significant storms.

Thursday night will be seasonably cool with ridging overhead
initially. However, as the night goes on, SW winds will increase as
a trough approaches from the NW. Despite skies partly cloudy or even
mostly clear, these increasing winds should help keep the PBL mixed
to keep temps in the teens for lows rather than in the single digits.

This stronger wind will continue into Friday as a 40-50 kt LLJ
overspreads the U.P. from west to east. There should initially be
enough sunshine Friday morning to help mix down some higher gusts
around 25-35 mph from the SW. Cloud cover will increase in the
afternoon leading to decreased mixing, but this lack of mixing will
be compensated by winds aloft increasing and reaching their peak in
the evening thus maintaining SW 25-35 mph gusts through the day and
into the evening. The early-day sunshine and downslope wind should
allow temps to climb above most raw guidance into the upper 30s and
low 40s for highs.

Two weak disturbances will move through the area this weekend, one
late Friday night into Saturday morning and the other Sunday
morning. They are expected to take similar tracks. Both will be
quick movers, and neither will have significant moisture to work
with. The Friday night snowfall will mainly affect areas east of a
line from Iron Mountain to Marquette. The snow from the Sunday wave
looks to be displaced a little bit to the east of that. Neither wave
should cause accumulations of more than an inch, and most of what
falls Friday night will melt on Saturday with highs getting into the
upper 30s and low 40s. Things begin to turn colder on Sunday with
the first in a series of two cold fronts.

The second cold front will likely move through late Sunday night or
early Monday morning. However, there remains some uncertainty in
just how cold the air will be behind it. The 06z GFS 850 mb temp of
around -27 C was near the bottom of the distribution of the GEFS
around 12z-18z Monday, and the 12z run is similarly cold.
Deterministic EC and UKMET from 00z are warmer (around -15 C and -23
C, respectively). WPC cluster analysis shows a signal for
underdispersion of the ensemble systems, especially in regard to the
speed/placement of the mid-level short wave that is responsible for
ushering in the brief cold shot. While 80% of 00z GEFS members fall
into two clusters with a deeper trough, 76% of the EC Ens members
fall into the other two clusters with a much flatter upper-level
pattern. Even the warmer members should still support some lake-
effect snow in the NW wind snow belts Monday afternoon, albeit
briefly.

Regardless of how cold and/or snowy Monday ends up being, models
show an amplifying ridge and WAA Monday night followed by strong SW
flow on the western edge of the ridge Tuesday. Raw models get temps
into the mid 30s for highs on Tuesday but if not much snow
accumulates the day before, the gusty SW flow and some sunshine with
the March sun angle could easily drive temps even higher. With a
pretty good ensemble consensus for 850 mb temps around -2 to -3 C,
some sunshine, and a stiff SW wind, it seems very unlikely that
highs will stay below freezing as suggested by the NBM
deterministic. For now, went with the NBM 75th percentile for high
temps, which is about 6-8 F warmer than the NBM deterministic. This
puts temps mostly in the upper 30s, with some low 40s west half.
Wouldn`t be shocked if some places get into the mid 40s though.

The warmth looks to continue into the end of next week. The CIPS
Analogs for the GEFS for the period next Thursday to next Sunday
show ~75% of matching analogs with above-normal temps and median
highs in the low 40s (and even 30-40% chances are highs in the 50s
near the Wisconsin line).
&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1238 PM EST WED FEB 24 2021

Any lingering IFR conditions at KSAW will improve to MVFR early in
the forecast period as drier air moves into the region with
increasing northerly winds. Otherwise, clearing will move into the
west this afternoon with conditions lifting to VFR. Upslope
northerly flow will delay the clearing at KSAW until early this
evening. Another weak trough moving into the reigon will drop cigs
back to MVFR by early Thursday.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 351 PM EST WED FEB 24 2021

Northwest winds of 25 to 30 knots over the east will diminish
quickly this evening and back westerly tonight. Southerly winds
increase with 35 knot gales over the east possible Friday. Winds
then dies down to 25 knots out of the northwest on Saturday.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Watch from Friday afternoon through Friday evening for
     LSZ249>251-266-267.

Lake Michigan...
None.
&&

$$

SHORT TERM...JLB
LONG TERM...RJC
AVIATION...JLB
MARINE...JLB


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