Area Forecast Discussion
Issued by NWS Duluth, MN

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332
FXUS63 KDLH 201537
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
937 AM CST Fri Jan 20 2017

.UPDATE...
Issued at 937 AM CST Fri Jan 20 2017

Our office began getting many reports of spin outs, crashes, and
icy roads from sheriff offices across northwest Wisconsin and
much of central into northeast Minnesota this morning due to the
rain and drizzle spreading through the region this morning. Even
though air temperatures are generally about freezing in the middle
30s, it appears road temperatures are near or below freezing, so
the rain is causing icing on some roads. We can confirm this from
sensors available from the MN DOT, with many areas of our
southwest and west-central forecast area in Minnesota reporting
those cold road temperatures. Instead of getting cute with trying
to decide which counties really need a freezing rain advisory or
not, and for the sake of time, decided to issue and then expand a
freezing rain advisory for much of the forecast area where the
rain and drizzle will be spreading through the region this
morning. Almost all of the forecast area, except far northern
Minnesota and the North Shore, have a freezing rain advisory in
effect through noon. Secondary roads and untreated roads will
likely be more affected then main roads. Hopefully the road
surfaces will warm up sufficiently enough by this afternoon to the
let the freezing rain advisory expire, but we will be keeping tabs
on reports we get to see how this situation evolves.

&&

.SHORT TERM...(Today through Saturday)
Issued at 325 AM CST Fri Jan 20 2017

Chances of precipitation should ramp up during the morning hours
today as a mid- to upper-level system moves through the region. This
system should have good support as a few pockets of vorticity maxima
along with some enhanced isentropic lift associated with the system
moves through. The associated northwest to southeast bands of
positive vorticity advection will lead to similar orientation of
precipitation, with mainly the eastern portions of the forecast area
under the best chances of seeing precipitation. A wintry mix is
possible with this precipitation as the thermal profile indicated
from the 20.00z GFS/NAM soundings are very much close to isothermal
along the 0 degrees C isotherm. A small change in the thermal
profile will change the precipitation types. Freezing rain, sleet,
and rain are all possible later this morning and afternoon.
Fortunately, any precipitation amounts should remain light, but some
roads may still become slick, especially if they have been
untreated. Highs today look to be in the upper 30s and lower 40s.
There should be more fog developing this evening and overnight as
additional snow melt occurs.

There could be some decent ice accretion Friday night and Saturday
morning along the North Shore as 1000-850 mb mean layer winds remain
from the southeast, enhancing orographic lift. Some ice
accumulations could reach up to one-tenth of an inch from the whole
duration of the system. Then, a more compact mid-level shortwave
trough will arrive Saturday morning and afternoon, which should
bring another chance of precipitation. There could be some freezing
rain/rain early Saturday morning, transitioning to drizzle/rain
Saturday afternoon, which should transition to snow Saturday night
into Sunday morning. By Saturday night, the sfc low pressure should
be situated just to the south of our forecast area, eventually
making its way northward into the Northland. More above freezing
temperatures are expected for the high temperatures on Saturday,
with highs again in the upper 30s and lower 40s.

.LONG TERM...(Saturday night through Thursday)
Issued at 325 AM CST Fri Jan 20 2017

Prolonged period of light precipitation and very mild temperatures
will continue through early next week, then colder (but still above
normal) temperatures and a chance for mainly snow mid-week. At this
point, the track for the mid-week storm continues to aim south of
the Northland, but still a few inches of snowfall are possible
across parts of east-central MN into northwest Wisconsin Tuesday
night into Wednesday. Highs in the upper 30s to low 40s this
weekend through Tuesday, mid 30s Wednesday, then to the upper 20s
to low 30s on Thursday - well above our normal highs around 20 in
late January.

On the synoptic scale, an upper low gradually lifts from the upper
Midwest into northwest Ontario Saturday night into early Monday.
With plenty of moisture through the column and cyclonic flow, there
is a chance for light precipitation all weekend, but the best
chance for moderate rain/snow will occur Saturday night as the
mature lifts up the I-35 corridor between the Twin Cities and
Duluth resulting in warmer air advection across the Minnesota
Arrowhead with southeast winds perpendicular to the shoreline.
While a broad area of better large-scale lift is expected due to
the mid-level PVA associated with the vort max approaching and the
warm air advection, some orographic enhancement will be possible
along the higher terrain of the north shore. Precipitation type
should be snow at higher elevations, but at the shoreline precip
may be a mix of rain and snow or all rain due to the influence of
the relatively warmer lake water. With the warmer environment
snowfall will be more of the wet variety with snow ratios around
4-6:1. Maybe 1-2 inches possible Saturday night along the higher
terrain, but otherwise little snowfall accumulation expected.
Decided to keep a mainly rain/snow drizzle/freezing drizzle mix in
the forecast as soundings indicate a very limited potential for
freezing rain due to warm surface temperatures, as we lose ice
aloft periods of freezing drizzle are certainly possible.

As the low dissipates to the early Monday a mid-level longwave ridge
builds across the Great Plains east into the Mississippi River
Valley, which should result in precipitation coming to an end by
Monday morning. As a deep longwave trough digs in across the west
coast, a mid-level shortwave trough will eject out of the Colorado
Rockies towards the Great Lakes Tuesday into Wednesday, with a
resultant surface low quickly deepening in response as it approaches
the mid-Mississippi River Valley. Cold air will wrap down across the
northern Plains in response to the low, with a broad precip shield
extending north into east-central Minnesota and northwest Wisconsin.
Surface low track remains well to the south across all guidance,
with a model consensus having the low towards far southern Wisconsin
by Wednesday morning. While a far northerly track remains within the
envelope of possibilities, looking at model trends and ensemble
guidance there are not many solutions with a much more northerly
track. Confidence is slightly above average for a low-end snowfall
event across northwest Wisconsin Tuesday night into Wednesday, with
light snowfall totals elsewhere Tuesday night through Thursday in
the colder wrap-around flow.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 535 AM CST Fri Jan 20 2017

MVFR conditions will quickly deteriorate to IFR conditions this
morning, remaining generally IFR through the TAF period. Light
rain with IFR ceilings will develop today from south to north,
changing to a rain/snow mix this evening. Visibility will be
reduced to MVFR or IFR with the combination of rain/drizzle and
fog/mist in place due to the melting snow pack given the warm
surface temperatures. Light southeast to east winds at less than
10 knots through the forecast period.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  38  33  37  33 /  80  60  60  70
INL  39  30  37  30 /  70  70  40  60
BRD  38  33  38  31 /  60  50  60  50
HYR  41  35  41  34 /  80  50  60  50
ASX  41  35  40  34 /  80  60  50  60

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Freezing Rain Advisory until noon CST today for WIZ001>004-
     006>009.

MN...Freezing Rain Advisory until noon CST today for MNZ018-019-025-
     026-033>038.

LS...None.
&&

$$

UPDATE...Grochocinski
SHORT TERM...JTS
LONG TERM...JJM
AVIATION...JJM



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