Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 201806
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1206 PM CST Mon Feb 20 2017

.UPDATE...
Issued at 1206 PM CST Mon Feb 20 2017

Rain with embedded thunder is spreading across the forecast area
this morning.  Thunder, even if isolated in nature is affecting
areas as far north as Koochiching county as of 1130AM this morning,
so have expanded the coverage of slight chance thunder to a much
larger portion of the area than we had before.  CAPE is weak, but
just strong enough to produce these isolated-scattered rumbles of
thunder.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 314 AM CST Mon Feb 20 2017

At 3 AM CST this morning, a cluster of showers and thunderstorms was
moving through the Brainerd Lakes region, with some moderate rain
associated with the storms, as indicated by nearby ASOS/AWOS
observations. This cluster appears to be associated with an 850 mb
low level jet and warm air advection. Increased POPs from previous
shift to account for this cluster. Convective-allowing models are
indicating this cluster will advance northward into Itasca and
Koochiching counties, and possibly northwestern St. Louis county,
later this morning.

The chances of precipitation will increase further this morning,
with precipitation taking hold across the rest of the Northland this
afternoon. A mid- to upper-level system will support these
precipitation chances as a mid-level shortwave trough with a deep
lifting profile advances through the region. Thermal profiles will
support all rain p-types throughout the event, with enhanced
moisture transport. GFS model Pwat values are progged over 1 inch,
with good theta-E advection into the Northland. Corresponding to the
enhanced moisture transport, QPF amounts look to be high for this
time of the year, with total QPF amounts between 0.2" along our
western fringes to nearly 0.9" towards the eastern counties through
Monday night. The heaviest rainfall is most likely to fall in the
afternoon hours today, so the afternoon commute looks to be a soggy
one. The melting snow from warmer temperatures, coupled with the
rainfall, will likely lead to ponding on low-lying roadways.
Moreover, thunderstorm chances will continue through the morning and
afternoon today as the latest RAP/NAM model soundings are progging a
few hundred J/kg of elevated CAPE values. So, continued the mention
of slight chance to chance thunder in the forecast.

Precipitation will eventually end early Tuesday morning as the mid-
level support moves to the east and dry low- to mid-level air moves
in. Subtle sfc high pressure ridging and more zonal flow at the mid-
levels look to follow the shortwave, keeping conditions quiet and
dry for Tuesday. The 20.00z GFS/NAM soundings show a mostly dry
atmospheric profile, so partly to mostly sunny skies are possible
Tuesday, although the soundings are hinting at some mid to high
clouds developing over the north. Otherwise, a nice dry day to
follow up the wet day from Monday. Temperatures will stay well above
seasonal normals today and Tuesday, with high temperatures in the
mid 40s to mid 50s for most of the Northland.

.LONG TERM...(Tuesday night through Sunday)
Issued at 314 AM CST Mon Feb 20 2017

A shortwave trof will move into the Dakotas late Tuesday night. Its
attendant surface low will organize in the central Dakotas. Even
though there will be an area of omega that reaches the forecast
area, the amount of moisture to work with is limited. The models
have backed off with the onset of precipitation from the previous
forecast and have followed suit by lowering pops. The surface low
will move across southern Minnesota and into eastern Wisconsin on
Wednesday, then into Quebec Wednesday night. Meanwhile, the upper
trof strengthens as it moves across the forecast area Wednesday
before departing Wednesday night. Will see a mix of rain and snow or
just rain or snow as these features pass by. Due to differences in
thermal profiles from the models, this leads to various QPF/snow
amounts. A break in the action comes on Thursday as the region will
be between systems. The next system is still being handled
differently by the ECMWF/GFS/GEM Thursday night through Saturday.
The ECMWF and GEM have decided to handle this system differently
from the previous 2 days of runs. The GFS has been the most
consistent. Will use a blend, but lean on the GFS which has the
support from NAEFS ensembles. Snow will be the main ptype as this
system will have plenty of cold air to deal with. This means that
the bulk of the accumulating snow will fall over northwest Wisconsin
with lighter amounts elsewhere. Much of the Borderland will miss out
on seeing snow with this system. As has been the case with this
system, the timing differences and overall coverage/amounts of snow
preclude a mention. Will fine tune as we get closer. Surface high
pressure follows this system and covers the region through Sunday.
There will be an opportunity for some light lake effect snow from
the Bayfield peninsula east along the Gogebic Range Saturday
afternoon through Monday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1206 PM CST Mon Feb 20 2017

An area of low pressure will lift northeastward into central
Manitoba this afternoon. The warm front and cold front associated
with the low will move through the forecast area today and
tonight. This will bring MVFR/IFR conditions with showers and
embedded thunderstorms. Embedded thunderstorms are expected
through the afternoon as there is a few hundred J/kg of MUCAPE per
the latest RAP. Expect visibilities to fall to 1-3 miles at times
in the heaviest showers.

Precipitation will come to an end at all terminals between 02Z and
07Z. Ceilings will gradually scatter out to VFR late tonight and
the concern will shift to fog formation. Uncertain at this point
how widespread fog will be as winds become westerly and guidance
has over done fog development over the past several days. Due to
uncertainty just hinted at fog developing at all terminals, but
if it appears to be much more likely then visibilities will need
to be lowered in future updates.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  45  32  49  34 /  80  60   0  10
INL  47  31  45  30 /  80  50  10  20
BRD  55  32  55  34 /  70  20   0  10
HYR  53  34  54  35 /  80  70  10   0
ASX  50  36  55  36 /  80  70  10   0

&&

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

$$

UPDATE...LE
SHORT TERM...JTS
LONG TERM...GSF
AVIATION...WL


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