Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 230939

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

.SHORT TERM...(Today through Friday)
Issued at 438 AM CDT Thu Mar 23 2017

A very complicated forecast for the next 24 hours, with some
sensitive fluctuations that will have a very large impact on the
forecast area, but that`s for tonight. As of early this morning,
yesterday`s ridge of high pressure has slid to the eastern Great
Lakes region, with a developing surface low over eastern Colorado
this morning, and an inverted trough extending north up into
Manitoba and Saskatchewan where a weak low was centered. A lobe of
mid level moisture over eastern Nebraska and Kansas this morning
is going to surge north today on a wave of isentropic lift, moving
into the forecast area this afternoon, and remaining over
northern Minnesota and Wisconsin through tonight before narrowing
and shifting back south again on Friday. Rain and even a little
embedded thunder is expected to spread into the forecast area from
the south this afternoon. The initial wave of snow/sleet from a
leading wave is moving across the area early this morning and
should move out of the area to the east fairly early this morning,
and expect a period of drier conditions for at least a few hours
before the next wave moving in from the south gets here. A fairly
major complicating factor are the temperature profiles associated
with this system. The warm air advection should bring our mid
level temperatures above freezing, and while we should warm above
freezing during the day today, tonight they are going to dip to
near or just below freezing for a large portion of the area. This
is going to produce a mixture of freezing rain, sleet and rain to
a fairly large portion of the area overnight tonight, and could
make for some significant travel problems for the Friday morning
commute. However, these temperature profiles are very dependent on
getting the temperatures at the surface and aloft right, and with
tonight`s Min temperature guidance ranging from the low to mid
30s  the Canadian- on the warm end, to the 20s  bias
corrected NAM12 - on the cold end, this puzzle is not making
itself easy this morning. For now, I have decided to go with a
winter weather advisory for portions of northwest Wisconsin,
knowing that it may need to be expanded to include portions of the
north shore as well, or dropped entirely depending on temperature
trends in the next 18 hours. It seemed to better to get the
notification of the potential out now rather than wait.

.LONG TERM...(Friday night through Wednesday)
Issued at 438 AM CDT Thu Mar 23 2017

While a vertically stacked upper/surface low meanders through the
Southern Plains Friday night, high pressure will be drifting through
northwest Ontario. An upper short wave trof with weakening area of
vorticity moves over western Lake Superior. This will be just enough
lift to continue to mention some mixed precipitation over much of
Pine county and northwest Wisconsin. Dry elsewhere due to the
surface ridge axis from the aforementioned high extending through
the area. On Saturday, upper level and surface ridging covers the
region. However, only the GFS is trying to back build some
precipitation into northwest Wisconsin as it has an embedded impulse
lifting into this area. Cannot rule it out completely and have small
pops for mixed ptypes in the early morning, then rain by mid morning
into the afternoon. The GFS continues to be the only model with
precipitation over the forecast area Saturday night, but is then
joined by the GEM. The NAM/ECMWF are dry. Used a blend for
ptypes/pops. The vertically stacked system departs Sunday, which
allows for the next pair of upper waves to affect the region through
Monday. Embedded impulses will cross the area between and with these
features, and will use a blended approach to pops/ptypes to resolve
differences in models and their thermal profiles. A Hudson Bay high
sets up for Monday night through Wednesday which will keep the
region dry. The only model bringing in any precipitation is once
again the GFS on Wednesday afternoon. Will have a small pop to
account for this option. Temps will be above normal.


.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

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.


DLH  37  31  43  26 /  70  80  20  10
INL  43  29  40  23 /  50  50   0   0
BRD  40  32  47  28 /  70  70  20  10
HYR  39  33  45  29 /  60  80  60  20
ASX  40  32  43  28 /  60  80  30  20


WI...Winter Weather Advisory from 8 PM this evening to 9 AM CDT
     Friday for WIZ002>004-008-009.



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