Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 192142
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
342 PM CST Sun Feb 19 2017

.SHORT TERM...(This evening through Monday night)
Issued at 342 PM CST Sun Feb 19 2017

The focus remains on the rain likely for Monday. There was little
change to the forecast. It still looks like the Northland will see
a period of wet weather, and there could be isolated thunder.

Tonight...The Northland will continue to see very unusually warm
southerly flow, with 850 hpa temperatures about 8 to 10 degrees
Celsius. There will be increasing upper-level cloud cover
overnight as low pressure works its way east from the High Plains
into the Northern Plains. There will be increasing dew point
temperatures later tonight in advance of the approaching cool
front in the Dakotas. The cloud cover and increasing dew point
temperatures will help to bolster the overnight temperatures to
very unusually warm levels more reminiscent of high temperatures
for this time of the year. Lows will only be in the 30s to lower
40s, so there will continue to be a bit of melting of the snowpack
overnight.

Monday...The Northland will see a surge of moisture amidst the
very unusually warm southerly flow ahead of an approaching cool
front and potent upper-level trough from the west. The
precipitable water values will increase to around 1 inches, quite
high for overall atmospheric moisture for this time of the year. A
period of deep saturation and rain will develop as falling
heights and a 100 to 120 knot jet streak develop substantial
atmospheric lift across the Northland. Strong south-southwesterly
flow aloft, combined with embedded shortwaves in the southerly
flow, could develop isolated, elevated thunder across parts of the
forecast area, primarily the southern half of the forecast area.
Several models have up to a couple hundred J/kg of MUCAPE,
including the GFS, SREF, NAM, and regional Canadian. The storms
would likely be relatively weak, mainly just providing some
rumbles of the thunder. There will likely be widespread rainfall
of 0.25" to 0.5" and isolated areas could get quite a bit more,
all depending on the track of and/or training of any heavier
showers or storms. The melting snow, combined with the rain and
difficulty any rain will have penetrating the relatively frozen
ground, will likely contribute to ponding on low-lying roadways.

Monday Night...There could be lingering showers across the
Arrowhead and northwest Wisconsin in the early evening, but cooler
and drier air will filter into the Northland amidst the westerly
flow in the wake of the cool front. Lows will likely be in the low
to middle 30s.

.LONG TERM...(Tuesday through Sunday)
Issued at 342 PM CST Sun Feb 19 2017

A rain/snow mix is possible for much of the Northland Tuesday
evening and Wednesday and then a significant storm system takes
aim on the region Thursday night through early Saturday morning.

Quasi-zonal flow expected to return behind the departing occluded
system Tuesday morning. A weak shortwave trough is forecast to
scoot across far northern Minnesota during the day increasing
cloud cover across the Northland. The lack of moisture behind
Monday night`s cold front will keep the risk of precipitation low.

Cloud cover will increase Tuesday night as a clipper system moves
out of the northern Rockies into the Dakotas and southern
Canadian Prairies. A compact shortwave trough and a slug of
Pacific moisture will raise the potential for a rain/snow mix
across much of the Northland. The best chance of precipitation
continues to be focused over the northern half of our CWA. Raised
QPF amounts with this forecast. Precipitation will begin as light
snow and change to rain Wednesday morning. Even with the higher
QPF, we are only carrying one-half up to an inch of snow
accumulation in our northern tier of zones. Temperatures will
trend cooler on Wednesday, and especially Thursday, behind the
clipper. Even with the surge of cooler air however, temperatures
will be closer to, but still above, normal.

Focus then shifts to the Thursday night through early Saturday
morning time period. A significant trough will dig into the
western CONUS Wednesday night and emerge over the Central Plains
Thursday morning. The quasi-zonal pattern over the Upper Midwest
will quickly shift to a southwest flow regime ahead of the
approaching trough. Baja Pacific and Gulf moisture will stream
northward into the Mississippi River Valley ahead of the
approaching low, setting the stage for a potent storm system to
affect the region late this week. The surface low is forecast to
track from southwest Colorado Thursday morning to somewhere in the
Great Lakes and eastern Canada by Saturday morning. Deterministic
solutions diverge considerably in handling this system with the
ECMWF moving the surface low to near James Bay by Saturday
morning, while the GFS low is centered over southern Ontario, and
the GEM farther west over Upper Michigan. Ensemble members feature
a wide envelope of solutions, too. Continued to lean on the
consensus for now, which brings accumulating snow to an area from
Lake Mille Lacs to the Twin Ports and all of northwest Wisconsin.
Snow will move northeastward into central Minnesota and east-
central Wisconsin late Thursday night or early Friday morning and
spread across all but far northwestern portions of our CWA by noon
Friday. The highest confidence continues to focus east of the
I-35 corridor and across all of northwest Wisconsin. Snow will
slowly diminish late Friday night and early Saturday. There is a
potential for a period of lake effect snow over snowbelt areas of
northwest Wisconsin through Saturday night.

With considerable uncertainty regarding the track and intensity
of this system, confidence in snow amounts is low, other than the
expectation that measurable to plowable snow seems likely for
portions of Minnesota and Wisconsin. Anyone with travel plans late
this week is encouraged to keep up with the latest forecast as
details become clearer.

High pressure will build into the Northland Saturday afternoon
and winds will veer northwesterly behind the departing storm. The
fresh snow pack and northerly breezes will bring near to below
normal temperatures back to the area Saturday and Saturday night.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1217 PM CST Sun Feb 19 2017

An area of VFR cirrus/stratus will move northeastward across the
terminals this afternoon and early this evening. This band of
clouds marks the location of the upper-level warm front. Radar
echoes over central and northwest Minnesota indicate an impressive
area of virga associated with this band. There could be a few
sprinkles at BRD, HIB, and INL as the band moves through, but feel
dry air in the mid- and low-levels will continue to evaporate the
precipitation before reaching the ground.

A low-level jet will develop tonight ahead of an approaching
storm system and LLWS is expected at all sites. Forecast models
continue the "wet bias" with ample low-level moisture for low
stratus or fog once again tonight. Since very little fog has
formed during the previous several nights, will ignore the overly
moist guidance and hold onto a scattered layer at MVFR altitudes.
Rain showers will move into the terminals from the southwest on
Monday morning. Think winds will become gusty thanks to
entrainment and mixing processes, so introduced wind gusts with
the showers and ended the LLWS potential.

Overall confidence in this forecast is above average.

&&

.CLIMATE...
Issued at 937 AM CST Sun Feb 19 2017

For record highs and record warmest low temperatures for Duluth
and International Falls, please see the Public Information
Statement (PNSDLH) issued by our office this morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  37  49  33  50 /  10  90  60   0
INL  37  48  32  46 /  10  90  50   0
BRD  44  54  33  54 /  10  80   0  10
HYR  41  53  35  54 /   0  90  70   0
ASX  37  53  37  54 /   0  80  60   0

&&

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

$$

SHORT TERM...Grochocinski
LONG TERM...Huyck
AVIATION...Huyck


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