Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 200929
AFDDLH

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

.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 06Z TAFS through 06Z Friday night)
Issued at 1211 AM CST Fri Jan 20 2017

Conditions will be highly variable across the Northland overnight,
and we are expecting a fairly progressive deterioration. A band of
light rain, freezing rain, and drizzle will march northward across
the region overnight, bringing lowering CIG`s and VSBY`s. We could
see some icing as well overnight and into Friday. Areas of fog can
also be expected, with a highly varied mix of flight categories
settling more into the IFR to VLIFR range. This should then
continue into Friday and Friday evening.


&&

.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  34  41  34 /  70  50  60  50
ASX  41  34  40  34 /  80  60  50  60

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&

$$

SHORT TERM...JTS
LONG TERM...JJM
AVIATION...DAP


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