Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 131150
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
650 AM CDT Fri Oct 13 2017

.UPDATE...
Issued at 642 AM CDT Fri Oct 13 2017

Updated aviation section below for 12Z TAF TAF issuance.

&&

.SHORT TERM...(Today through Saturday)
Issued at 318 AM CDT Fri Oct 13 2017

Mostly dry conditions expected for today, despite a cold front
boundary moving through the Northland this morning, and 700-500 mb
layer frontogenesis moving over northwest Wisconsin this afternoon.
For early this morning, continued small chances of drizzle, mainly
over the Minnesota Arrowhead for the next few hours, and over
northwest Wisconsin through the morning hours. The NAM and RAP model
soundings both prog a saturated layer in the low levels advancing
through the region, along with the cold front. These soundings do
indicate that the saturated layer will shrink from the top down by
dawn, so chances of drizzle will decrease after sunrise. Current
regional radar mosaics show a band of light precipitation stretching
from south-central South Dakota, extending into central Minnesota.
This is associated with the aforementioned FGEN, which is progged to
translate eastward. The lift associated with this band should remain
to the south, but should still clip Price county in northwest
Wisconsin this afternoon. Chances of rain aren`t too high with this,
and not expecting much in the way of accumulations either. Clouds
will decrease from northwest to southeast today as sfc high pressure
builds into the region, so overall, mostly sunny skies are expected.
High temperatures will remain around seasonal averages, with highs
ranging from the lower 50s north to the upper 50s over northwest
Wisconsin.

A cool night is in store as the area of high pressure moves right
over us. Skies will remain clear, along with light winds, will bring
cool temperatures, with lows tonight ranging from the middle to
upper 20s north to the lower to middle 30s south.

Conditions will become more active Saturday afternoon as a mid-level
shortwave trough develops over the Intermountain West and advances
eastward over the region. Good lift will accompany this system with
strong isentropic upglide on the 305 K pressure surface Saturday
afternoon, mainly per the 13.00z GFS model, but the NAM model also
indicates this isentropic lift, mainly Saturday evening. The
associated sfc low pressure will develop from lee cyclogenesis, and
lift northeastward over Iowa and southern Wisconsin, placing us
underneath the inverted sfc trough. The baroclinic zone associated
with this system appears to stay to the south over central Wisconsin
Saturday afternoon, but low-level thermal profiles will remain too
warm for snowfall. However, this is a different story for Saturday
evening. More on that in the long term section. A rumble of thunder
may be possible over north-central Wisconsin Saturday afternoon as
some small elevated instability is progged to move into this area.
However, this is a very small risk at this time. Convective-allowing
models are progging a wing of stratiform precipitation to translate
northward, so some wetting rainfall is expected for Saturday
afternoon, with amounts between a few hundredths over the Iron
Range up to around one-quarter of an inch to the south.

.LONG TERM...(Saturday night through Thursday)
Issued at 330 AM CDT Fri Oct 13 2017

Saturday night and Sunday have been the main focus of the forecast
for a few days now, with a very strong low pressure system that
moves from eastern Iowa northeast across Wisconsin to eastern Lake
Superior overnight Saturday night, intensifying as it moves and
deepens before moving off to the northeast on Sunday.  There are
still some model differences, with the NAM farther west and deeper
than the GFS/ECMWF by Sunday morning.  Of greater concern though, is
the position of the baroclinic zone and that is in better agreement
among the models, draped from southern Minnesota across northern
Wisconsin and then across Lake Superior around 06z Sunday.  The cold
air aloft over northern Minnesota combined with surface temperatures
near freezing there as well, is going to produce some snow across
the region.  In fact, considering the dynamics of the system as it
moves across, we could have a short period of fairly heavy
precipitation rates, which may very well be snow.  For a short
period of time there could be a surprising amount of snow, mainly on
grassy surfaces, before it all melts once again.  SREF plume data
shows that some places up in the arrowhead may get a couple inches
of snow, with some of the ensemble members producing much more.
These higher values are rather unlikely, but I do feel that an inch
or two are possible by Sunday morning in the Arrowhead along and
north of the Iron Range.  Precipitation ends quickly on Sunday, even
as it switches back to all rain.

Once the Saturday night/Sunday storm system moves out of the area,
conditions get quiet across the area with northwest flow on the back
side of the exiting upper level trough.  This pattern continues
through at least mid week, with the upper level ridge shifting east
of the area, and the flow aloft turning more southwesterly as a
large trough axis moves onto the west coast.  For now, it appears
that any shortwaves embedded in this flow will track either north or
south of the area, leaving us with some needed dry weather for a few
days.  Towards the end of the week, enough uncertainties creep into
the forecast that we may see some precipitation chances.
Temperatures will have been cool on Sunday and Monday, then
gradually warm through the week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 642 AM CDT Fri Oct 13 2017

Stratus continues to affect KHYR, and also KINL, but these
locations to return to VFR by 15z this morning as a cold front
continues to slide east through the area. West to southwest winds
to increase for several terminals and may gust to 15-20kts for a
few hours for locations that mix deeply enough. Winds to diminish
again to less than 10kts after 23z.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  56  34  53  36 /  10   0  70  90
INL  53  26  51  32 /   0   0  50  70
BRD  55  36  54  35 /   0   0  90  90
HYR  59  35  56  38 /  10   0  90  90
ASX  60  33  56  40 /  10   0  70  90

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory until 11 AM CDT this morning for LSZ140-141.

&&

$$

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


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