Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/28/25
Area Forecast Discussion
National Weather Service Marquette MI
705 PM EST Mon Jan 27 2025
.KEY MESSAGES...
- Northwest gales to 45 knots with isolated 55 kts (north-
central) will continue through this evening, eventually
falling below gales tonight.
- Strong cold front passing across the area late this afternoon/evening
will lead to a quick burst of heavy snow, low visibilities
for a brief time.
- A Clipper system Tuesday into Tuesday night brings widespread moderate
to locally heavy snow to Upper Michigan. A band of heavy snow
is expected Tuesday evening, but it`s placement is still
uncertain at this time.
- Winter Weather Advisories have been issued across western and central
Upper Michigan for the incoming Clipper snow. Generally 3 to
6 inches expected Tuesday and Tuesday night across the area,
with locally higher amounts possible closer to Lake Superior
and lesser amounts closer to Wisconsin.
- High-end gales to Storm Force Winds possible over Lake
Superior Tuesday through Tuesday night. Heavy Freezing Spray
is also a distinct possibility given the higher winds.
- Normal to above normal temperatures expected the rest of this week
through this weekend.
- No significant lake effect or system snowfall is expected from
Wednesday to this weekend.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 358 PM EST Mon Jan 27 2025
Main focus late this afternoon/evening is a cold front, which is
currently stretching eastward along an Ironwood...Crystal
Falls...Manistique line. Winds ahead of it remain strong out of the
southwest with gusts generally in the 20 to 25 mph range. Behind the
front, winds have shifted to the northwest, but continue to gust up
to 25 to 30 mph at times. The exception continues to be the Keweenaw
and Grand Marais areas where wind gusts are still in excess of 35
and 45 mph, respectively. Meanwhile, current radar mosaic has
quickly lit up in just the last hour, which matches well with the
CAMs predictions of a quick snow squall in association with the
aforementioned cold front. Highest reflectivities are approaching
the eastern Lake Superior nearshores and are expected to expand
westward and sink across the U.P. through the evening hours.
Snow totals will generally be in the 1 to 2 inch range, but they
will be quick and in combination with the strong winds.
Therefore, visibility restrictions and slick roads will make it
difficult for any late evening commuters.
CAMs trend has the squall line through the U.P. by Tue 03Z at which
time the SPS highlighting the event will expire. But again, continue
to exercise caution through the night if driving as strong winds
contribute to blowing snow threat. In addition, temperatures will
rapidly drop after the brief warmup into the 30s today. Currently,
ground-based obs across the area are still reporting upper 30s
ahead of the cold front with upper 20s/low 30s behind it. But,
temperatures will plummet all the way into the single digits
above zero across all of the U.P. tonight as CAA strengthens.
&&
.LONG TERM /TUESDAY THROUGH MONDAY/...
Issued at 354 PM EST Mon Jan 27 2025
The extended period starts out very active as a Clipper low moves
through Lake Superior Tuesday and brings a burst of moderate to
locally heavy snowfall across the U.P. throughout the daylight
hours; the HREF currently shows a 30 to 60% chance of snowfall rates
up to 1 inch per hour in the Keweenaw and east Tuesday where the
greatest snowfall is currently expected with this system. These
robust snowfall rates will cause travel concerns, accumulating to
roadways quickly and bringing visibilities down to a half to quarter
mile or less at times. With SLRs being very fluffy initially, expect
vigorous warm air advection to raise the SLRs into the mid teens by
the afternoon hours. However, with most of the forcing still being
within the DGZ, I`m not expecting SLRs to go much lower than that
before snow showers return behind the Clipper low Tuesday evening.
Given the burst of snowfall associated with the warm air advection
via the Clipper and the high SLRs, we could see a quick-hitting 2 to
5 inches across the area Tuesday. In addition to the snow
accumulations, expect to see patchy blowing snow across much of the
area, especially in the Keweenaw and along the Lake Superior
shoreline as winds gust up to 40 mph. The patchy blowing snow will
further deteriorate driving conditions across the area by severely
limiting visibilities in windy spots. Therefore Winter Weather
Advisories have been issued this afternoon across western and
central Upper Michigan. Now, if the track of the low moves further
north, we may see lower snow totals in the areas near the Wisconsin
border; however, if the track for some reason goes further south,
then totals in the interior U.P. will be higher. Given the warm air
advection associated with the Clipper, we could see some spots in
the west along the lakeshore get right to or just above freezing
Tuesday; they may see less snowfall due to locally lower SLRs and
melting.
Moving into Tuesday night, expect a strong fgen band to bring a band
of heavy lake enhanced snowfall back across portions of the U.P.;
the latest HREF currently shows scattered chances of 10 to 30% of
snowfall rates up to 1 inch per hour across the U.P. to account for
this fgen band. While even the CAMs are still struggling on the
placement of this band, with a majority of guidance showing this
occurring, strong cold air advection behind the cold front, and
strong vorticity ahead of the cold front, this band of heavy snow
will bring an additional 1 to 4 inches to wherever it sets up fast;
currently, it seems to be either the Keweenaw and eastern U.P. from
Munising to Newberry, or the west, although some other areas such as
Marquette County cannot be completely ruled out either. Thus,
wherever this band sets up, we could see some of the Winter Weather
Advisories upgraded to a short Winter Storm Warning to account for
this heavy snowfall as roadways will quickly become snow covered and
visibilities will be one quarter mile or less at times within the
band. As the Clipper low continues eastwards across the Lower Great
Lakes into New England late Tuesday night into Wednesday, expect the
lake enhanced snow to become pure lake effect over the north-
northwest to eventually northwest wind snow belts. As surface high
pressure ridging builds in from our northwest Wednesday, expect the
lake effect snowfall to significantly decrease across the area,
although a remnant low over eastern Lake Superior may keep the lake
effect going until the evening hours. While we could see some light
snow showers over mainly the east half Thursday morning as a second
Clipper low digs through northern Ontario, expect mostly dry
conditions across our area late Wednesday night into this weekend as
another high pressure drops into the Upper Great Lakes from the
Canadian Prairies.
For temperatures late this week into this weekend, expect highs to
oscillate between normal and above normal. The warmest day is
expected to be on Thursday as robust warm air advection in
association with the mid-week Clipper north of us moves through the
Upper Peninsula. This tongue of warm air will allow highs to get
into the mid 30s to lower 40s after possibly some light snow showers
move through the area early in the day. Once the cold front of the
Clipper moves over us, more normal temperatures return as highs dip
back down into the mid 20s. After the surge of colder/more normal
air moves over us this weekend, medium range guidance is suggesting
that a Clipper and possibly a shortwave low lifting from the central
Rockies could bring more precipitation into the area to end the
extended period this weekend into early next week.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 705 PM EST Mon Jan 27 2025
Cold front dropping across Upper MI was accompanied by +shsn. In the
wake of the front, lake effect shsn will occur mainly into the
eastern U.P. tonight. On Tue, attn turns to clipper low pres that
will track ese to Lake Superior, spreading -sn across the area. At
IWD, sct -shsn associated with passing cold front may lead to ocnl
MVFR conditions for the next couple of hrs. Otherwise, expect VFR to
prevail tonight. A 2-3hr period of IFR in -sn is expected Tue
morning at IWD. MVFR cigs will follow. At CMX, expect VFR this
evening with cloud bases aoa 4000ft. BLSN will result in MVFR vis
with ocnl brief IFR. High end MVFR cigs should develop overnight at
CMX, then -sn develops mid to late morning with vis falling thru IFR
to LIFR. Diminishing -sn in the aftn will allow vis at CMX to
improve to MVFR. At SAW, burst of mdt/hvy snow associated with cold
front is exiting to the s currently. Expect MVFR thru 02z with ocnl
IFR thru 01z. Conditions will trend VFR by 03z with VFR continuing
until about mid morning when -sn develops. Vis will quickly fall
thru IFR to LIFR. Expect improvement back to MVFR by mid aftn at
SAW. Gusty wind this evening will diminish to under 10kt late
tonight/early Tue morning at all terminals. Winds then become gusty
again by late Tue morning with some risk of LLWS.
&&
.MARINE...
Issued at 354 PM EST Mon Jan 27 2025
Northwest high-end gales to 45 knots over the eastern half of Lake
Superior this afternoon weaken to around 20 knots by Tuesday morning
as surface high pressure ridging moves through the area ahead of an
incoming Clipper low from the Canadian Prairies. As this happens,
expect the heavy freezing spray conditions to progressively improve
tonight into Tuesday morning. However, as the Clipper low makes its
way into the lake Tuesday, expect winds to pick up from the
southwest to 20 to 30 knots with a few gale force gusts up to 35
knots possible ahead of it; this eventually becomes northwest gales
of 40 to 45 knots behind said low Tuesday evening and night, with
westerly gales of 40+ knots or much higher Tuesday as the low enters
the lake and immediately behind it towards the Keweenaw Peninsula.
Indeed, some CAMs such as the HRRR bring storm force winds up to 60
mph (wow!) over the lake Tuesday evening as a strong fgen band
associated with the incoming cold front develops over the area.
These higher winds could bring heavy freezing spray conditions back
across Lake Superior Tuesday and Tuesday night; therefore, we could
see additional Heavy Freezing Spray Warnings issued for Lake
Superior in the future. While mixing will remain strong in the
boundary layer Tuesday night into Wednesday, the winds will
progressively weaken Tuesday night through Wednesday as the cold air
advection behind the Clipper low dissipates. Thus, we should see
winds die back down to 20 to 30 knots by Wednesday afternoon, with
winds backing to the west and eventually southwest Wednesday night
as weak surface high pressure ridging moves through the Upper Great
Lakes; this will cause winds to weaken further to around 20 knots or
less by around midnight Wednesday night. However, with yet another
Clipper low diving down through northern Ontario Thursday, expect
winds to increase from the southwest to around 25 knots. Once the
cold front of the Clipper moves through Thursday evening, expect
northwest to north winds of 20 to 30 knots to return to the lake
Thursday night, with the highest winds expected in the east half. As
more high pressure ridging moves through the Upper Great Lakes
Friday and Saturday, expect the winds to weaken back down to 20
knots or less. However, with yet another Clipper low expected to
move through the Canadian Prairies this weekend, expect winds to
begin picking up from the south and southwest again late Saturday
in response.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory from 7 AM Tuesday to 7 AM EST
Wednesday for MIZ001>004-006-007-084-085.
Winter Weather Advisory from 7 AM Tuesday to 1 AM EST
Wednesday for MIZ005.
Lakeshore Flood Advisory until 1 AM EST Tuesday for MIZ006-007.
Winter Weather Advisory from 6 AM to 11 AM CST Tuesday for
MIZ009.
Winter Weather Advisory from 7 AM to noon CST Tuesday for
MIZ010-011.
Winter Weather Advisory from 8 AM to 1 PM CST Tuesday for
MIZ012.
Winter Weather Advisory from 9 AM to 7 PM EST Tuesday for
MIZ013-014.
Lake Superior...
Gale Warning until 10 PM EST this evening for LSZ242>244-263-
264.
Heavy Freezing Spray Warning until 7 AM EST Tuesday for
LSZ243>251-264>267.
Gale Warning until 1 AM EST Tuesday for LSZ245>251-265>267.
Lake Michigan...
Gale Watch from Tuesday afternoon through Wednesday morning
for LMZ248-250.
&&
$$
SHORT TERM...TDUD
LONG TERM...TAP
AVIATION...Rolfson
MARINE...TAP