Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 262100

Area Forecast Discussion
National Weather Service Duluth MN
400 PM CDT Wed Oct 26 2016

.SHORT TERM...(This evening through Thursday)
Issued at 400 PM CDT Wed Oct 26 2016

The forecast area was between systems at 19Z. Low pressure over
Saskatchewan, high pressure over Ontario, and low pressure over
Iowa. This resulted in the easterly flow persisting along with
plenty of cloud cover. The rain that had been affecting the western
and southern edges of the region this morning and early afternoon,
has diminished. Additional rain is falling farther north and covers
the Twin Ports, along the south shore of Lake Superior, and is now
beginning to affect the north shore. This rain was being helped
along by differential vorticity advection in the 700-400mb layer,
the passing of an upper level trof and a coupled jet structure.

The upper trof slowly moves eastward tonight and the coupled jet
structure diminishes. The aforementioned surface systems move
gradually eastward as well. Another upper level short wave trof/
vorticity maxima, moves into Ontario late tonight. Just enough
upward vertical motion clips the Arrowhead to generate a chance of
showers. Forecast soundings from short term hires models and
deterministic models, no longer indicate the potential for snow and
have removed.

The upper level short wave/vorticity max are shoved eastward on
Thursday, replaced by upper level ridging. Weak high pressure drifts
over the area in the late morning and is east of the area by late
afternoon. A warm air advection pattern arrives in the late morning
and pushes eastward through the day. Unfortunately, there will be
plenty of clouds around preventing a good warmup.

.LONG TERM...(Thursday night through Wednesday)
Issued at 400 PM CDT Wed Oct 26 2016

Main concerns for the long term are precipitation chances Friday
through Saturday morning and again Sunday night through early
Tuesday morning.

A longwave ridge in place over the Northern Plains and Upper Midwest
at the start of the period will flatten into a quasi-zonal pattern
by sunrise Friday morning. A shortwave trough will eject east across
the Rockies Thursday night and across the region Friday. A surface
low will push eastward out of North Dakota and the southern Canadian
Prairies ahead of the upper trough. With a brief period of return
flow ahead of the system, moisture will be limited. Cloud cover will
increase ahead and north of the low track bringing a chance of rain
across my north. All deterministic guidance has taken a more
northern track with this system than this time yesterday, so
confidence is increasing with the placement of POPs along my
northern zones. With relatively warm temperatures, think rain will
be the main p-type.

The trough and surface low will shift east of the area Saturday
morning. With cyclonic flow behind the departing shortwave and
modest cold air advection, think showers will linger over my eastern
zones until early Saturday. Winds will back northwesterly over
western Lake Superior as well, which should support a slight chance
of lake effect showers over favored areas of Bayfield, Ashland, and
Iron Counties. Quasi-zonal flow returns in response to the departing
trough, while another subtle ripple in the flow pushes east across
the Central Plains and into southern Minnesota during the day.
Like the consensus keeping POPs with that feature south of my CWA
and lowered POPs Saturday night and Sunday.

Longwave trough over the western CONUS is expected to kick eastward
Sunday night and Monday. While deterministic solutions differ in
strength and trajectory of surface reflection, the fact that the
medium-range guidance continues to move this trough into the area
early next week increases confidence. GFS is much stronger with the
evolution of the trough and produces a strong surface low over
northern Ontario Monday night. ECMWF and GEM are weaker with the
upper trough and surface low, partially due to phasing issues with a
second trough farther upstream over the Canadian Rockies. At this
point, prefer the non-GFS consensus which does bring a prolonged
precip event into the Northland Sunday night continuing through late
Monday night. Confidence in temperature at that time range is merely
average, especially given diverse model solutions. Have a rain/snow
mix for a few locales at the beginning of the precipitation and
again Monday night. There is certainly a potential for accumulating
snow with this system, but low confidence in p-type warrants leaning
toward all rain with occasional rain/snow.

Northwest flow returns Tuesday into early Wednesday with temperatures
likely cooling heading into the midweek.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1249 PM CDT Wed Oct 26 2016

Surface low pressure over eastern Iowa was supporting light rain
across much of Wisconsin and portions of northeast Minnesota this
afternoon. Expect the rain to gradually shift eastward and
diminish as the low moves toward southern Lake Michigan by early
evening. Mainly MVFR ceilings can be expected for the afternoon,
except over far northern Minnesota where VFR ceilings should
continue for several more hours. Ceilings will gradually lower
tonight with all sites seeing a period of IFR ceilings overnight.
Model output statistics and vertical profiles from the NAM and RAP
hint at the possibility of LIFR ceilings developing overnight, but
elected to keep SCT group for the lower ceiling potential for now.
A second area of low pressure will drop southeast out of
Saskatchewan overnight, which could result in another round of
showers overnight. Added VCSH mentions overnight with this
package, as confidence and timing with additional precipitation is
lower than average. Ceilings will gradually raise back into low-
end MVFR Thursday morning. Confidence in this forecast is above
average through 26.02Z and average thereafter.


DLH  37  47  41  58 /  10   0  10  10
INL  38  49  42  54 /  10  10  10  30
BRD  37  51  44  62 /  10  10   0   0
HYR  34  48  41  62 /  20   0   0  10
ASX  37  48  41  60 /  30   0  10  10


LS...Small Craft Advisory until 10 PM CDT this evening for LSZ142>147.

     Small Craft Advisory until 4 AM CDT Thursday for LSZ140-141.

     Small Craft Advisory until 4 PM CDT this afternoon for LSZ121-



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