Area Forecast Discussion
Issued by NWS Duluth, MN

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197
FXUS63 KDLH 161138
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
638 AM CDT Thu Aug 16 2018

.SHORT TERM...(Today through Friday)
Issued at 401 AM CDT Thu Aug 16 2018

A gradual warming trend through the end of the work week with just a
low chance for precipitation today in parts of northwest Wisconsin
then again Friday across the MN Arrowhead.

On the synoptic scale a mid-level closed low is clearly visible on
infrared and water vapor channel satellite imagery over central
South Dakota early this morning. This low will take an east-
southeast track towards the Mid-Mississippi River Valley today
towards the Ohio River Valley tonight. Over the Upper Midwest a weak
front will track from north to south across the region late today
into night in the wake of the mid-level low to the south, but
impacts from this front will be minimal - a few clouds, a shift in
wind direction, and not much else. Behind the front a broad area of
high pressure over Ontario will stretch down into the Upper Midwest
on Friday leading to broad-scale subsidence. Despite this, a few
diurnally driven showers are possible across the MN Arrowhead
focusing on a lake breeze boundary moving inland. Instability will
be minimal and deep layer winds weak, so threat for thunderstorms
appears very low, but a few brief showers are possible.

The past few weeks have been abnormally dry northern Minnesota,
especially along and west of the Iron Range. In parts of northern
Minnesota, the amount of rain in the past 30 days has been half or
less of normal, and in the past 14 days some locations have not even
received a half inch of rain, which is less than 25 percent of
normal. The lack of recent rain combined with sunny skies and a
relatively dry airmass in the area will lead to relative humidity
values falling to 30 to 40 percent each afternoon today and
tomorrow. While winds will be very light, the Minnesota DNR rates
the fire danger in northern Minnesota as high in Koochiching,
Itasca, and parts of central St Louis County.

Today will be begin with areas of fog gradually lifting in the
morning with a general trend towards sunny skies. Like yesterday,
there is a chance for an isolated shower/storm in parts of northwest
Wisconsin, mainly in Price county in our CWA. A weak front moving in
from the north will result in a wind shift, with winds out of the
west in far northern MN, out of the north in east-central MN and NW
Wisconsin - but in both cases, light around 5 mph. Highs in the
upper 70s to mid 80s, a few degrees above normal for mid-August.

Tonight another round of fog possible, with the best chance for fog
in northwest Wisconsin. Lows milder compared to this morning in the
50s.

On Friday the front that moves from north to south across the area
on Thursday finally moves along the stalled out boundary that brought
chances for storms in northwest Wisconsin over the previous three
days. High pressure overhead will result in north winds with 5 to 10
mph winds off Lake Superior along the shoreline. The lake breeze may
kick off a few showers across the MN Arrowhead, but precip will not
be widespread in coverage or very long in duration. Highs again in
the upper 70s to mid 80s, cooler near the lake.

.LONG TERM...(Friday night through Wednesday)
Issued at 401 AM CDT Thu Aug 16 2018

Friday night through Saturday the area will remain quiet with a
ridge of high pressure nearby.  A shortwave and surface low pressure
system and cold will move across northern Ontario, bringing chances
for showers and storms there, but these should stay north of the
Canadian border.  Temperatures during this period to remain above
normal with plenty of sunshine.

The cold front from that system to our north will slowly sag into
the forecast area Saturday night and Sunday, and interact with a
strong shortwave that moves across the northern High Plains.  This
should bring some chances for showers and storms into the area as
early as Saturday night and Sunday.  The models appear to agree that
this upper level shortwave will strengthen and even cut off to
varying degrees through Monday before slowly shifting out of the
region by Tuesday. The models have some significant disagreements on
the strength and timing of this feature, and do not have much
confidence in the forecast beyond Monday.  However, for now it
appears that the greatest chance for showers and storms with this
will be Sunday afternoon and night through early Monday, and the
main question will be how long into Monday and Tuesday we will need
to continue precipitation chances.  We need the rain, so hopefully
this system lingers around for a little longer, and bring rainfall
to most of the area.  Temperatures will also be pushed back down 70s
through the early part of the week, with highs only in the 70s.
Behind this system we get another large ridge of high pressure, and
we should have another period of warm dry weather through the end of
the work week with highs near to above normal.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 631 AM CDT Thu Aug 16 2018

An area of high pressure over northern Minnesota this morning will
continue to slide east with a weak trough of low pressure moving
from Canada into the northern MN terminals after 00z this
evening. Fog is affecting several of the terminals with LIFR
conditions, which are expected to begin clearing with visibilities
and ceilings improving to VFR by 15z this morning. Once the fog
has cleared expect VFR conditions through approximately 09z
tonight, when several sites should once again develop fog. For
now have put in IFR visibilities with no ceilings, but we may need
to put in lower conditions as we see what the low level moisture
parameters do during the daytime today. However, there is little
to no airmass change expected and will not be surprised to have
another period of LIFR conditions after 09z.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  79  57  82  57 /   0   0  10   0
INL  85  56  83  56 /   0   0   0   0
BRD  81  58  84  59 /   0   0   0   0
HYR  82  55  84  55 /  20   0  10   0
ASX  77  55  81  57 /   0   0   0   0

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Dense Fog Advisory until 8 AM CDT this morning for WIZ001-006.

MN...Dense Fog Advisory until 8 AM CDT this morning for MNZ019-026-
     035>038.

LS...None.
&&

$$

SHORT TERM...JJM
LONG TERM...LE
AVIATION...LE



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