Ice Storm Warning 1, NWS Duluth, MN

Area Forecast Discussion
National Weather Service Duluth MN
1146 PM CST Fri Dec 23 2016

.UPDATE...
Issued at 919 PM CST Fri Dec 23 2016

The precipitation has diminished through the evening with only
very light echoes showing up on area radars. Observations reveal
only some light rain at KIWD as of 03Z. We have had a recent report
in DLH of freezing drizzle with little occurring at the office.
There still could be some light drizzle or freezing drizzle in
spots tonight a low level trough through central Minnesota moves
east. Some of the models have picked up on some light QPF
overnight and we will add to the forecast for far eastern
Minnesota into northwest Wisconsin.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 340 PM CST Fri Dec 23 2016

Light snow associated with a pair of shortwave troughs moving
through the Upper Midwest has spread across east-central Minnesota
and northwest Wisconsin this afternoon. Early reports from the
Webster, WI area indicated around one-quarter inch of snow
accumulation within the first hour and a half. We expect light
snow to continue over northwest Wisconsin and east-central
Minnesota through early evening, ending from west to east by
midnight at the latest. Total snowfall of up to 2 inches is still
expected with the highest amounts from Siren and Webster to
Hayward to Mercer and points south. Precipitation may end as
drizzle or freezing drizzle. The troughs quickly shuffle eastward
overnight allowing a return to a quasi-zonal flow for late
overnight and Saturday, yielding a brief break in active weather
ahead of the holiday storm.

.LONG TERM...(Saturday night through Friday)
Issued at 340 PM CST Fri Dec 23 2016

The primary focus for the long term periods continues to be on the
major winter storm/strong surface low that will affect the entire
region on Christmas and Monday. The condensed version is that
there are very few major changes to the forecast this afternoon
regarding this storm as overall large scale model guidance remains
in rather remarkable agreement on the placement/timing of the
synoptic scale features.

However, there is still major uncertainty regarding a couple of
important details that will have make or break impacts on the
sensible weather. Namely, the continued major model differences in
surface temps Christmas afternoon into Christmas night. While
there is little doubt that a warm layer aloft will rapidly return
northward and likely switch precip over to liquid, the GFS is by
far the most aggressive model at surging the surface warm sector
northward, while the NAM continues to be the most aggressive at
holding a shallow sub-freezing layer at the surface for a
majority of the event. The yields tremendous uncertainty and a
very large range of possibilities for high-impact weather in the
form of ice accumulations from freezing rain.

We are continuing to focus our messaging on at least *some*
potential (perhaps 30-35%) of a quarter inch of ice accumulation
or more in a band from Walker and the Brainerd lakes region east-
northeastward to Grand Rapids/Duluth and parts of the MN
Arrowhead. The grids and official forecast at this point have ice
accums generally between a tenth and two tenths of an inch in
these areas, as there is also, of course, the potential that the
warmer models verify and precip switches over to plain rain for
several hours Christmas Day evening. We are hopeful that the
various models come to a better consensus over the next 24-36
hours, but ascertaining specific areas for significant freezing
rain and ice accums is often extremely difficult even a few hours
in advance, let alone 2 days.

This storm should also bring progressively higher snowfall totals
the farther north/west one goes in the Duluth CWA, with the
potential for 6+ inches in the far northwest, as well as the
higher terrain of the Mn Arrowhead, as enhanced by deep/strong
easterly flow across Lake Superior. It should also be emphasized
that this will be a heavy, wet snow, that will cling to
trees/power lines/etc. So even areas that do not see ice accums
could still see power outages. The entire ice/snow accumulation
region will also be swept by 20-35 mph winds with some higher
gusts on Monday as the strong surface low departs, which could
exacerbate the potential power outage problems.

The storm will be followed by a short intrusion of arctic air,
with a transition back to a more progressive WNW flow regime aloft
by the middle of next week, which will bring a couple chances for
light snow or mixed precip with a couple of weak waves - each
followed by a 12-24 hour cool down.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1146 PM CST Fri Dec 23 2016

A trough of low pressure extended from near KCDD to just west of
KBRD then continued southwest. This trough will move east clearing
northwest Wisconsin early Saturday morning. Widespread IFR and
MVFR ceilings covered the Northland and other than some localized
brief clearing, they will continue overnight. Patchy drizzle or
freezing drizzle will be possible ahead of the trough but due to
the expected coverage we did not include in the TAFS at this time.
KCDD reported UP in the observation at 0530Z which may be
freezing drizzle or a mix of light snow/freezing drizzle given
cloud top temperatures of only -12C. There also could also be
some fog overnight but the visibility will most likely remain
MVFR.

Some partial clearing of the stratus deck is expected on Saturday
but more stratus is expected to move in later Saturday night.

The wind will become northwest behind the trough then continue to
veer to north then east through the rest of the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  24  28  21  31 /  40  10  30  80
INL  17  20   8  28 /  10   0   0  70
BRD  22  28  24  32 /  10  10  30  90
HYR  26  32  24  36 /  70   0  20  80
ASX  28  32  21  35 /  80   0  20  70

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Storm Watch from Sunday morning through Monday morning
     for MNZ025-026-033>037.

     Winter Storm Watch from Sunday afternoon through Monday morning
     for MNZ010>012-018>021.

LS...Small Craft Advisory until 4 AM CST Saturday for LSZ140-141.

&&

UPDATE...Melde
AVIATION...Melde

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE DULUTH MN
434 PM CST FRI DEC 23 2016

MNZ010>012-018>021-025-026-033>038-WIZ001>004-006>009-241130-
KOOCHICHING-NORTH ST. LOUIS-NORTHERN COOK/NORTHERN LAKE-
NORTH ITASCA-CENTRAL ST. LOUIS-SOUTHERN LAKE/NORTH SHORE-
SOUTHERN COOK/NORTH SHORE-NORTH CASS-SOUTH ITASCA-SOUTH CASS-
CROW WING-NORTHERN AITKIN-SOUTH AITKIN-CARLTON/SOUTH ST. LOUIS-
PINE-DOUGLAS-BAYFIELD-ASHLAND-IRON-BURNETT-WASHBURN-SAWYER-PRICE-
434 PM CST FRI DEC 23 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST
MINNESOTA AND NORTHWEST WISCONSIN.

.DAY ONE...TONIGHT

LIGHT SNOW WILL END FROM WEST TO EAST THIS EVENING ACROSS EASTERN
MINNESOTA AND NORTHWEST WISCONSIN. TOTAL ACCUMULATIONS OF AN INCH
OR TWO ARE EXPECTED ACROSS MUCH OF NORTHWEST WISCONSIN. LIGHT
FREEZING DRIZZLE OR SNOW FLURRIES MAY PERSIST IN MANY AREAS
OVERNIGHT...RESULTING IN SOME AREAS OF SLIPPERY ROADS ACROSS THE
ENTIRE AREA.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A MAJOR WINTER STORM WILL AFFECT THE NORTHLAND DURING ONE OF THE
BIGGEST TRAVEL PERIODS OF THE YEAR. THE STORM WILL ARRIVE IN FULL
FORCE ON CHRISTMAS DAY...AND PERSIST INTO MONDAY MORNING. THIS
STORM WILL BRING A VARIETY OF WEATHER CONDITIONS...WITH SNOW...
SLEET...FREEZING RAIN...AND EVEN RAIN. THERE ARE TWO MAJOR
CONCERNS. THE FIRST IS THE POTENTIAL FOR HEAVY SNOW OVER NORTHERN
MINNESOTA...GENERALLY NORTH AND WEST OF A LINE FROM CASS LAKE TO
ELY...AND OVER PORTIONS OF THE HIGHER TERRAIN ADJACENT TO LAKE
SUPERIOR IN THE MINNESOTA ARROWHEAD. THE HEAVIEST SNOW IS EXPECTED
IN THE BIGFORK AND INTERNATIONAL FALLS AREA. THE SECOND MAJOR
CONCERN IS THE POTENTIAL FOR ICE ACCUMULATIONS. THE GREATEST RISK
FOR SIGNIFICANT ICE ACCUMULATION WILL BE IN AN AREA FROM THE
WALKER AND BRAINERD LAKES REGION...TO GRAND RAPIDS AND
DULUTH...AND INTO THE MINNESOTA ARROWHEAD. A WINTER STORM WATCH IS
IN EFFECT FROM CHRISTMAS MORNING THROUGH MONDAY MORNING. THE
WEIGHT OF HEAVY WET SNOW AND ICE ACCUMULATIONS ON TREES AND POWER
LINES COULD LEAD TO POWER OUTAGES IN MANY AREAS.

STRONG AND GUSTY WEST WINDS UP TO 40 MPH WILL LEAD TO AREAS OF
BLOWING AND DRIFTING SNOW SUNDAY NIGHT AND MONDAY. ANYONE WITH
TRAVEL PLANS CHRISTMAS DAY AND MONDAY SHOULD CONTINUE TO STAY
CURRENT WITH THE LATEST FORECAST THROUGH THE WEEKEND. NOW IS THE
TIME TO MAKE A PLAN IN CASE CONDITIONS BECOME TOO DANGEROUS TO
TRAVEL. PLEASE REFER TO THE LATEST WINTER WEATHER MESSAGE FOR
ADDITIONAL DETAILS ON THE WINTER STORM WATCH THAT IS IN EFFECT FOR
MANY AREAS.

.SPOTTER INFORMATION STATEMENT...

SNOW SPOTTERS ARE REQUESTED TO REPORT PRECIPITATION TYPE...AND
MEASUREMENTS OF SNOW OR ICE ACCUMULATIONS TONIGHT. SNOW SPOTTERS
WILL ALSO BE NEEDED CHRISTMAS DAY AND MONDAY. A REMINDER THAT
SPOTTERS AND THE PUBLIC CAN ALSO REPORT PRECIPITATION TYPE WITH
THE FREE M-PING SMARTPHONE APP.

LSZ121-140>148-241130-
BAYFIELD TO OAK POINT WI-GRAND PORTAGE TO GRAND MARAIS MN-
GRAND MARAIS TO TACONITE HARBOR MN-
TACONITE HARBOR TO SILVER BAY HARBOR MN-
SILVER BAY HARBOR TO TWO HARBORS MN-TWO HARBORS TO DULUTH MN-
DULUTH MN TO PORT WING WI-PORT WING TO SAND ISLAND WI-
SAND ISLAND TO BAYFIELD WI-OAK POINT TO SAXON HARBOR WI-
434 PM CST FRI DEC 23 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF THE NEARSHORE
WATERS OF WESTERN LAKE SUPERIOR.

.DAY ONE...TONIGHT

PERSISTENT SOUTHWEST WINDS WILL CONTINUE ACROSS PARTS OF THE
NORTH SHORE OF WESTERN LAKE SUPERIOR TONIGHT...RESULTING IN
CONDITIONS HAZARDOUS TO SMALLER VESSELS. PLEASE REFER TO THE
LATEST NEARSHORE MARINE FORECAST AND MARINE WEATHER MESSAGE FOR
MORE DETAILS ON A SMALL CRAFT ADVISORY THAT REMAINS IN EFFECT FOR
SOME AREAS TONIGHT.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A STRONG WINTER STORM IS FORECAST TO MOVE INTO THE REGION
SATURDAY NIGHT AND CONTINUE THROUGH MONDAY. WINDS WILL BECOME
EASTERLY ON SATURDAY AND WIND SPEEDS WILL INCREASE MARKEDLY
SATURDAY NIGHT AND SUNDAY. WINDS WILL THEN SHIFT TO THE SOUTHWEST
AND REMAIN STRONG ON MONDAY AS LOW PRESSURE MOVES FROM NORTHWEST
MINNESOTA INTO NORTHWEST ONTARIO. CONDITIONS WILL BE HAZARDOUS TO
SMALL CRAFT SATURDAY AND FREQUENT GALE-FORCE GUSTS ARE LIKELY
SATURDAY NIGHT THROUGH MONDAY AFTERNOON. A GALE WARNING MAY
EVENTUALLY BE NEEDED FOR CHRISTMAS DAY INTO MONDAY EVENING.

MORE INFORMATION MAY BE OBTAINED AT THE FOLLOWING WEB ADDRESS:
HTTP://WWW.WEATHER.GOV/DULUTH (ALL LOWER CASE)