Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 191755 AAB
AFDDLH

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
1155 AM CST Thu Jan 19 2017

.UPDATE...
Issued at 1155 AM CST Thu Jan 19 2017

Please read the new 18Z Aviation Discussion below.

&&

.SHORT TERM...(Today through Friday)
Issued at 345 AM CST Thu Jan 19 2017

Fog has developed across portions of the Northland this morning
as a warmer and more moist airmass has made its way into the
region. The warmer air has lead to some snow melt, lending further
moisture for fog. Some fog this morning is expected to become
dense in some locations, so decided to issue a Dense Fog Advisory
for the southern half of our forecast area through 15Z this
morning. Some fog may linger later in the morning, but shouldn`t
be as dense.

Most of today will remain dry, except for some developing areas
of drizzle/freezing drizzle/fog this evening and overnight as a
push of mid-level positive vorticity advection and weak 700-500 mb
layer frontogenetical forcing translates from the south. Another
day of above freezing temperatures is expected again today across
the area, with highs in the upper 30s and lower 40s.

A better push of FGEN and 500 mb isentropic lift moves into the
forecast area Thursday night and Friday morning, which will bring
increasing chances of a wintry mix to the area through the day
Friday. Freezing rain, sleet, and snow are all possible, depending
on the thermal profile. Any snow and ice accumulations that occur
will be very light in nature. However, there may be some slick
spots on untreated roadways during this time. Precipitation type
should be mostly light rain by Friday afternoon, transitioning
back to brief wintry mix, and then all snow by Friday night.

.LONG TERM...(Friday night through Wednesday)
Issued at 345 AM CST Thu Jan 19 2017

A mild and wet period through the weekend into early next week,
with a chance for a more substantial storm and a return to
slightly colder temperatures by mid-week.

On the synoptic scale a somewhat active pattern across North
America with a broad upper low lifting into the upper Midwest over
the weekend, getting stuck and slowly dissipating as a stronger
upper low ejects out of the southern High Plains into the
southeast US. To the north, a broad ridge builds over Hudson Bay
with little in the way of arctic air even as far north as the
northwest Territories. With the upper low getting essentially
stuck in the flow over the upper Midwest, a period of mild
temperatures and light precipitation is expected through early
next week. Temperatures at the surface and aloft will be very
warm, with surface temperatures likely driving the precipitation
type much of the time. Ice loss aloft may be an issue, and with a
thin warm layer between 800mb and 925mb depicted on the NAM, a
period of freezing rain is possible. However, most guidance is a
bit cooler and thus, when precipitation is ongoing and
temperatures at the surface are below freezing, precip type should
be snow. Occasional freezing drizzle is still possible at times,
which could result in minor ice accumulations, but through the
weekend generally little snow/ice is expected. Highs in the upper
30s to low 40s Saturday through Monday, lows upper 20s to low 30s.

Late Monday into Tuesday a mid-level longwave ridge builds across
the central and southern Plains east into the lower Mississippi
River Valley. Then another upper low lifts from the central Great
Plains towards the Great Lakes region. The latest guidance keeps
the bulk of the large-scale lift and precip focused south of the
Northland, but there is still enough uncertainty across ensemble
guidance to suggest a more northerly track is at least possible.
However, because of the deepening low to the south, colder air
will advect south across the region leading to at least some light
precipitation and colder temperatures, especially as the low lifts
east towards the lower Great Lakes on Wednesday. Temperatures will
be colder aloft but at the surface temperatures will remain mild
with highs in the 30s Tuesday and Wednesday, lows in the 20s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1155 AM CST Thu Jan 19 2017

Fog and low stratus from the melting snowpack was found across
much of northern Minnesota and northwest Wisconsin late this
morning. A wedge of clearing was located over central Minnesota
and portions of northwest Wisconsin and is expected to move
northward this afternoon. Visibility and ceilings at HYR may be
variable this afternoon between VFR and IFR. Visible satellite
imagery indicates an area of low stratus just east of the airfield
which was showing signs of expanding slowly westward. Included a
TEMPO group with lower visibility and ceilings at HYR to account
for that potential. Elsewhere, conditions are expected to improve
to MVFR or VFR at INL and HIB. Low stratus and fog will lift
northward from central and southern Minnesota and central
Wisconsin into the area again late this afternoon or this evening.
Expect a return to widespread LIFR ceilings and visibility at most
sites. There is a potential for freezing drizzle overnight, but
surface temperatures may be close to freezing during that time.
The precipitation intensity may increase Friday morning as a warm
front advances north into the area. Rain, freezing rain, and snow
will be possible and precipitation type will depend significantly
on surface temperatures. Confidence in this forecast package is
average.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  38  33  37  31 /  10  40  60  50
INL  39  28  39  28 /   0  10  40  70
BRD  38  31  38  31 /  10  30  50  40
HYR  42  32  40  34 /   0  60  60  30
ASX  43  32  40  32 /   0  50  70  40

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Dense Fog Advisory until noon CST today for MNZ010>012-018>021-
     025-026-033-035-037.

LS...None.
&&

$$

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


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