Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 230523
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1223 AM CDT Thu Mar 23 2017

.UPDATE...
Issued at 949 PM CDT Wed Mar 22 2017

Minor updates made to adjust hourly temperatures and some slight
adjustments to POPs and weather. Precipitation has been slow to
develop, as anticipated, with just the Walker MN AWOS reporting a
brief period of light snow with no visibility reduction earlier
this evening. Ceilings remain around 5-6kft, which combined with
the radar echos and mesoanalysis data indicates there is likely
some virga falling across this elevated frontal zone. Some light
snow showers should develop towards late tonight as this frontal
zone moves east, but little accumulation expected.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 348 PM CDT Wed Mar 22 2017

High pressure over the Great Lakes region will continue to shift
to the east, and an upper-level ridge will move into the Northland
from the west this evening. Southerly flow will bring an influx
of warmer and more humid air into the Northland through tonight,
bringing increasing cloud cover. A shortwave trough will lift
from the northern High Plains through the Northland by the wee
hours of the morning, and the lift from the wave will help deepen
up the atmospheric moisture, likely deep enough to produce some
light snow. The best chances for the snow will be across the
Arrowhead, where up to a half inch of snow is possible. Other
parts of the Northland could get a light dusting.

The southerly flow will continue Thursday, with the upper-level
ridge axis shifting east of the Northland and shortwaves lifting
into the Northland in its wake. The shortwaves, combined with the
deepening moisture, will likely result in widespread light rain by
later in the afternoon. Highs will primarily in the 30s, but low
40s are forecast for north central Minnesota.

.LONG TERM...(Thursday night through Wednesday)
Issued at 348 PM CDT Wed Mar 22 2017

Main challenge for the long term include precipitation types
Thursday night through Monday. Temperatures should be cold enough
for a wintry mix during the night with mainly rain during the day.

A quasi-stationary frontal boundary is forecast to extend from
the Central Plains northeastward into the Minnesota Arrowhead
Thursday evening. A combination of convergence and isentropic
upglide should provide enough forcing for ascent to yield
precipitation beginning late afternoon or during the evening
hours. Initially, temperatures should be warm enough for all rain,
but a mix of rain, freezing rain, and snow will develop by mid-
evening. Warm temperatures aloft over portions of the Minnesota
Arrowhead and northwest Wisconsin raise concerns regarding the
availability of ice crystals for snow. A deep elevated warm layer
will also contribute to melting any snow which is able to develop.
The potential for freezing rain is greatest over those areas,
with the highest ice accumulation over portions of Ashland, Iron,
and Price Counties. As with most freezing rain events, antecedent
surface temperatures will play a significant role in the
precipitation type. Temperatures on Thursday should be in the
middle to upper 30s and could result in all rain for much of the
event. Given the continued uncertainty, elected not to issue any
headline products on this shift. Ice accumulation of around one-
tenth of an inch is possible, especially over portions of Price
County, and later shifts will need to re-evaluate the need for
headlines.

The band of precipitation will gradually drift southeastward
through our forecast area by late Friday morning as the front sags
south. Precipitation should change back to rain as intensity
slows. The 12Z deterministic models all trended drier over the
Northland for Friday through early Saturday morning, but the
ensemble members warrant keeping POPs over northwest Wisconsin. An
area of low pressure, which is forecast to loiter over the
Central Plains Thursday night and Friday, will wobble
northeastward Saturday and Sunday bringing a wintry mix back into
the picture. By Monday, high pressure will begin to push into the
area and will bring the precipitation to an end. Dry and quiet
conditions are expected for Tuesday and Tuesday night before
another chance of showers pushes into the area.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1223 AM CDT Thu Mar 23 2017

VFR conditions are expected overnight as the previously forecast
lower ceilings have generally failed to materialize due to a
significant dry layer at low levels depicted on the INL and MPX
upper air soundings. A few flurries are possible overnight, but any
visibility-reducing snow will be very limited in duration. On
Thursday south-southeast winds will increase with a few gusts to 20-
25 knots possible. Ceilings will begin to rapidly lower in the
afternoon as light rain develops. Visibility and ceilings will be
reduced to MVFR levels in the afternoon with periods of IFR
conditions possible late in the afternoon and into the evening
hours.

At this point precipitation type will be right on the edge between
rain and freezing rain. The dry air at low levels right now would
lead to wet bulb temperatures below freezing, meaning dew points
will need to rise enough in the southerly flow this morning to
result in a wet bulb temperature above freezing. This is a very
difficult forecast since temperatures are right on the edge, but
given the southerly flow this morning we have leaned on more of a
rain scenario with fog/mist reducing visibility to a mile or less at
times Thursday late afternoon/evening. Winds diminish towards the
evening to around 5 knots out of the south-southeast.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  26  37  30  43 /  30  50  80  20
INL  27  43  29  40 /  20  40  50   0
BRD  32  39  32  47 /  10  50  70  20
HYR  28  38  33  45 /  20  40  90  50
ASX  23  39  31  44 /  40  40  90  30

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory from 10 AM this morning to 4 PM CDT this
     afternoon for LSZ140.

&&

$$

UPDATE...JJM
SHORT TERM...Grochocinski
LONG TERM...Huyck
AVIATION...JJM


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