Area Forecast Discussion
Issued by NWS Duluth, MN

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808
FXUS63 KDLH 182147
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
347 PM CST Wed Jan 18 2017

.SHORT TERM...(This evening through Thursday)
Issued at 343 PM CST Wed Jan 18 2017

Relatively quiet day today with plenty of sunshine to boost
temperatures into the mid 30s to low 40s. Pressure pattern is
relatively weak over the area with a surface ridge over the lower
Ohio river valley and a weak lee trough developing in the lee of
the Rockies, and we have weak southwest flow over the forecast
area. There is sunshine occurring over most of Minnesota, Iowa,
the Dakotas and most of Nebraska this afternoon. Tonight this is
expected to change as the southerly flow increases advects some
warmer and more moist air up over the snowpack that has been
experiencing snowmelt today. This, from past experience is likely
to cause stratus development this evening. The question is where,
with very poor indicators of location in the models. The models
appear to develop it somewhere over Iowa/eastern Nebraska this
evening, then spreading it rapidly northeast overnight tonight and
Thursday. This is certainly possible, but would not be surprised
to see it develop farther north over southern Minnesota and
eastern North Dakota, near the edge of the snowpack and where the
most melting has happened today. Either way, it should spread into
the southern portions of the forecast area before dawn and then
slowly march north during the day. Expect a sharp northern edge to
the stratus, leaving sunnier conditions for the northern CWA for
at least the morning hours before it spreads in during the
afternoon. We may end up being a little too cool on highs across
the northern CWA, depending on the progress of the stratus to the
north. With the stratus spreading in, have included drizzle once
the deeper moisture moves in during the late afternoon.

.LONG TERM...(Thursday night through Wednesday)
Issued at 343 PM CST Wed Jan 18 2017

Summary: The Northland can expect the warmer than normal weather to
continue through the middle of the week, but with a cooling trend
beginning towards the end of the forecast period. Daily high
temperatures will likely be in the middle to upper 30s, except begin
to drop back to near the freezing mark by Wednesday. There will be
periods of wintry mixtures of rain/drizzle, freezing rain/drizzle,
and snow through at least early this weekend, followed by additional
periods of rain and snow over the latter half of the weekend into
early next week. Overall...expect cloudy weather through the
forecast period.

Thursday night and Friday morning...An upper low will be over
the Central Plains by Thursday evening. It will lift northward
overnight into Friday, becoming a negatively tilted upper-trough.
It will bring a surge northward into the Northland, and its synoptic
lift will develop some light precipitation across the Northland. The
GFS and NAM soundings primarily support periods of rain/drizzle and
snow, but there could be some freezing drizzle and light freezing
rain if the surface temperatures are cold enough to cause freezing
on surfaces. Overnight temperatures could dip to near or just below
the freezing mark, so the freezing on surfaces is certainly
possible. Any snow accumulation should be very light due to the lack
of deep moisture and melting from the relatively warm temperatures
in the low-levels.

Friday afternoon through early Saturday...Even deeper moisture will
work its way into the Northland during the latter half of Friday
into Friday night. The precipitation should primarily transition to
light rain and drizzle by early Friday afternoon, but the soundings
suggest a transition to a period of snow late Friday into Friday
night, especially over northern Minnesota. Forecasting snowfall
amounts is tricky this far out, especially considering the
considerable uncertainty regarding precipitation amounts. The GFS
continues to have much less precipitation than the ECMWF and
Canadian with this next main wave of precipitation. If the snow is
only light, as the GFS suggests, then melting will probably result
in little if any accumulation. However, the ECMWF and Canadian
suggest a period of moderate snowfall rates, which could drop
temperatures and result in a quick accumulation of snow. The ECMWF
and Canadian scenario even might need a winter weather advisory due
to the snow causing low visibility and difficult travel conditions.
Also, in the wake of the main wave of moisture, there will be a
possibility of freezing drizzle/rain into early Saturday.

Saturday and Saturday night...A weak upper-low may move through the
Northern Plains and Upper Midwest, potentially helping to maintain
cloud cover over the Northland and some light rain and/or snow.

Sunday into Monday...A Southern Plains low will lift into the
Eastern US, and its inverted trough over the western Great Lakes
could bring additional light rain and snow to the Northland.
Considering its inverted trough, there could be some banding of the
rain and snow, but those details will be forthcoming once we get a
better idea of even where the inverted trough would set up.

Tuesday into Wednesday...There are still some signs of a potential
winter storm system affecting parts of the Plains and Upper Midwest,
namely from some run-to-run continuity from the GFS. The latest GFS
continues to indicate a strong low developing near eastern Colorado
early next week, then lifting through the Central Plains to Great
Lakes during the middle of the week. The latest 12Z low track is
similar to the ensemble mean, taking the low to near southern Lake
Michigan. This track could bring snow to parts of the Northland.
However, the latest run of the ECMWF no longer has this storm
system, even though previous runs were fairly similar to the GFS.
Therefore, there is more uncertainty now the likelihood of this
storm system forming. Storm or no storm, there will likely be a
cooling trend of the middle of the week as cooler air filters out of
Canada.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1155 AM CST Wed Jan 18 2017

The widespread clear skies and light winds across northeast
Minnesota and northwest Wisconsin will likely continue through at
least most of tonight. There is a low chance of fog late tonight.
The biggest concern is the threat of IFR/MVFR stratus moving into
the Northland from the south late tonight and Thursday morning
when a surge of moisture begins to move into the region. Not
confident yet that this stratus will reach Northland terminals by
late morning, but the best chances of this occurring by the
afternoon will be at KHYR and KBRD, followed by KDLH and KHIB. The
NAM and GFS show high humidity around 950 and 925 hpa spreading
into the region late tonight and in the morning, but have concerns
that the stratus might not develop until even deeper moisture
arrives Thursday afternoon and evening.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  25  38  32  37 /   0  10  20  50
INL  23  36  29  39 /   0   0  20  30
BRD  24  38  31  38 /  10  20  20  50
HYR  27  40  32  40 /  10  10  30  50
ASX  27  40  32  40 /   0  10  20  50

&&

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

$$

SHORT TERM...LE
LONG TERM...Grochocinski
AVIATION...Grochocinski



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