Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 181151
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
551 AM CST Mon Feb 18 2019

.SHORT TERM...(Today through Tuesday)
Issued at 329 AM CST Mon Feb 18 2019

Some light lake effect snow/flurries are expected along the South
Shore of Lake Superior this morning. Otherwise, quiet conditions
continue through Tuesday afternoon.

The Northland remains under the influence of an upper-level trough,
situated over the Intermountain West states. A trough of low
pressure associated with the upper-level jet stream was situated
over the northeastern United States, with surface high pressure
building into the eastern MT and western ND region. This has
resulted in generally a north to northeast flow over the region,
which has supported some lake induced snowfall and low stratus
clouds over the western arm of Lake Superior. Over the last several
hours, radar reflectivity has diminished a bit, but light snow
continues to be reported in Duluth and Ironwood under the lake
induced stratus. The models haven`t handled this lake effect snow
very well, but current GOES-16 nighttime microphysics imagery shows
an expanding stratus deck coming off Lake Superior between Saxon
Harbor and the Keweenaw Peninsula, so we have chances of lake effect
snow continuing through at least mid-morning today before the
boundary layer begins to dry out and the wind profile backs more
northwesterly. Total accumulations should remain light, ranging from
a coating up to one inch possible. Elsewhere, skies will be partly
to mostly sunny, with highs in the teens to lower 20s.

Increasing cloud cover tonight as a mid-level shortwave trough
advances into the region. Overnight lows will be quite cold yet
again - falling into the single digits to lower teens below zero.
However, the temperatures aren`t expected to bottom out too much due
to the cloud cover, which will inhibit radiational cooling, despite
the high pressure building into the region from the west. The high
pressure will remain in control over the region through Tuesday
afternoon, with mostly sunny skies expected. Highs should range from
the middle teens to lower 20s.

.LONG TERM...(Tuesday night through Sunday)
Issued at 220 AM CST Mon Feb 18 2019

A period of light snow Wednesday into Wednesday evening producing
around 1 to 3 inches of snow for parts of the Northland, then a
break late week before snow chances return through the weekend.
Temperatures just below to near normal through the week and into
next weekend.

Mid-week, a longwave mid/upper level trough over the southwest
ejects into the Great Plains and towards the Great Lakes. While
there will be a short period of southeast flow and warm air
advection at low levels ahead of the mid-level trough axis, the
primary forcing mechanism for precipitation will be the broad air
of mid-level PVA. The GFS/GEFS ensemble is the most muted in terms
of the synoptic features and resultant precipitation, while the
NAM has consistently been an aggressive outlier over the past few
runs. The ECMWF and Canadian have been more in the middle of these
two extremes, but still trending towards a more aggressive
deepening of the mid/upper level features as the trough lifts
northeast towards the Upper Great Lakes. There will be amble
low/mid level moisture associated with this trough due to
south/southeasterly flow across the Gulf Coast advecting low level
moisture into the southern Great Plains ahead of the trough axis
on Tuesday, but with stronger large-scale forcing possible and
somewhat slower than usual large-scale flow, there is a
possibility for higher snowfall amounts, especially across
northwest Wisconsin. Overall forecast amounts have been nudged
higher with this forecast, with around 1 to 3 inches expected for
parts of northeast Minnesota, including the Twin Ports, and as 2
to 5 inches of snowfall across northwest Wisconsin. Around an inch
or less for areas north and west of the Iron Range. The greatest
impact from this snowfall will likely be during the Wednesday
afternoon/evening commute.

In the wake of the mid/upper level trough departing the southwest
early in the week, another one will deepen late-week which will then
eject into the Great Plains and Midwest, taking a slower evolution
which will lead to a more mature low with the potential for much
greater snowfall amounts. This late-week/weekend system will dig a
bit deeper and farther south before lifting northeast towards the
Great Lakes, and ahead of it a few mid-level shortwave troughs will
result in additional chances for snow before the main mid/upper
level trough axis causes a surface low to deepen over the Mid
Mississippi River Valley into the Great Lakes late Saturday into
Sunday. Ahead of the main surface low, the slower evolution of the
longwave trough axis will lead to a longer period for low level
moisture and warm air advection across the Great Lakes region, with
high temperatures into the low to mid 20s on Saturday. With a warm
frontal zone in the vicinity there will be a chance for light snow
across the Northland late Friday into Saturday, but the best chance
for snow arrives Saturday night into the day Sunday as the main low
deepens and moves across the Great Lakes. There remains a large
spread across guidance in what kind of track the low will take, from
the Canadian and FV3-GFS which have a faster and much, much more
farther south track resulting in little to no precipitation across
the Upper Midwest, to the aggressive ECMWF which produces a broad
area of conditions capable of supporting 1-2" per hour snowfall
rates for a period Saturday night into Sunday morning. Confidence in
some accumulating snow this weekend is high, but confidence in the
higher snowfall amount scenarios is low - even some GFS ensemble
members have solutions which bring little to no snow across the
Northland.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 552 AM CST Mon Feb 18 2019

After a brief period of MVFR ceilings this morning at DLH and HYR
due to lake-effect clouds, conditions will improve to VFR through
the rest of the forecast period at most sites. Mainly clear skies
to start outside of the lake effect clouds over northwest
Wisconsin and the Twin Ports, with gradually increasing high level
clouds today into tonight. Overnight, a layer of MVFR stratus will
develop in parts of northwest Wisconsin, impacting HYR. Winds
remain very light through the TAF period at around 5 knots or less
out of the northwest.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  17  -3  18   5 /  20   0   0  10
INL  11 -11  15   2 /   0   0   0   0
BRD  15  -8  14   3 /   0   0   0  30
HYR  20  -2  21   7 /   0   0   0  20
ASX  17   0  22   8 /  40   0   0  10

&&

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

$$

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


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