Area Forecast Discussion
Issued by NWS Duluth, MN

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878
FXUS63 KDLH 240004 AAA
AFDDLH

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
704 PM CDT FRI SEP 23 2016

.UPDATE...
Issued at 705 PM CDT Fri Sep 23 2016

Band of light/moderate rain with a few embedded weak/brief TStorms
extending from eastern North Dakota to the Twin Cities metro area
continues to translate steadily eastward this evening, with the
leading edge now moving across areas from Walker to the Brainerd
Lakes area. This band of precip is tied to the strong
moisture gradient and low-mid level baroclinic zone laid out
northwest to southeast in this area, with large scale forcing in
the form of deep layer warm/moist advection. This is also being
enhanced by mesoscale frontogenesis forcing for ascent. We have
made a few adjustments to the forecast for overnight and Sat
morning, raising PoPs a bit and bringing this band of rain
steadily northeastward across the Duluth CWA.

An updated aviation discussion for the 00z TAF issuance is also
included below.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 247 PM CDT Fri Sep 23 2016

High pressure was located over northwest Ontario with an east
northeast flow around the high which was creating a gusty northeast
wind over western Lake Superior. Farther inland, surface winds were
in an east southeast direction. This was ahead of a developing
surface low in the lee of the Rockies in northeast Colorado. Between
these features, the first wave of showers and thunderstorms were
lifting northeastward out of southeast North Dakota and southwest
Minnesota. As this activity progresses towards the forecast area,
there is a decrease in the number of lightning strikes and some
erosion of the reflectivity field as it encounters the drier air
over the region. The showers and storms were occurring in the area of
a coupled jet structure that runs from northwest North Dakota
southeastward into south central Minnesota, with an assist from a
weak shortwave trof lifting northward through the eastern Dakotas on
the backside of upper ridging.

All models indicate that some short wave energy will undercut the
upper ridging over the region tonight. This will help push some
showers and isolated storms into the southwest corner of the
forecast area early this evening. MUCAPE is less than 250 J/kg and
the 850mb lifted index is barely below 0C. This instability will
diminish after sunset and just have a mention of showers the rest of
the night.

The upper ridge moves east of the region on Saturday. Meanwhile, an
upper level cut off low begins to deepen over western North Dakota.
Strong warm air advection will cover the by afternoon with a low
level jet to 30 knots reaching the western third of the forecast
area. There will be some lingering showers in the morning that will
occur on the nose of this jet, diminishing by noon. There ill be a
break in the rain early in the afternoon before the next wave of
showers and storms begins to impinge on the western third of the
region in the late afternoon. This activity will be occurring along
and ahead of a cold front moving through western Minnesota.

.LONG TERM...(Saturday night through Friday)
Issued at 247 PM CDT Fri Sep 23 2016

Low pressure in the Northern Plains will move east and north
Saturday night. A LLJ will usher in PWAT values around 1.6 inches
overnight and showers will increase in coverage. A few hundred J/KG
of MUCAPE will be in place and with strong lift, thunderstorms will
also be possible. The thunderstorms will be capable of producing
localized heavy rain Saturday night. The low will become nearly
vertically stacked on Sunday over southern Manitoba. The models are
in decent agreement that shower/storm coverage will be lower on
Sunday than what occurs Saturday night and much of the area could be
in a dry slot with little precipitation coverage. If some clearing is
able to develop, a narrow area of higher instability will form
Sunday afternoon ahead of a cold front that will extend south of the
low and some strong storms would be possible into the evening.

The ECMWF is the fastest pushing the low east and north of the
Northland with the Canadian/NAM/GFS all keeping the upper low over
or near the Northland through 12Z Monday before it slowly continues
east. Showers and a few thunderstorms will be possible Sunday night
and we linger a chance for showers into Tuesday. We keep a chance
for showers longer than what even the slower GFS suggests for Monday
night into Tuesday as we think with the colder air in place behind
the front they will continue to be possible. Gusty west to northwest
winds will develop late Sunday night and be strongest Monday into
Monday evening behind the departing low.

Mainly dry conditions are expected Tuesday night through Friday.

High temperatures will be in the sixties on Sunday with only the mid
to upper fifties Monday. Highs will then warm back into the mid to
upper sixties Wednesday into Thursday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 625 PM CDT Fri Sep 23 2016

Conditions should slowly deteriorate from southwest to northeast
overnight as warm frontal boundary slowly moves north, and pushes
a band of rain, and potentially a few brief/weak TStorms across
the TAF sites. Ceilings should lower into MVFR category at all TAF
sites with the precip for at least a few hour period, and ceilings
are expected to be slow to rise after precip stops with low
ceilings and the development of some fog. A few sites, especially
KDLH and KHIB could see IFR conditions for several hours late
tonight and Sat morning. Due to strong east winds at the surface,
KDLH could also approach LLWS conditions between 03-14z, but it is
marginal enough and shear appears to be distributed over a
sufficiently deep layer to preclude inclusion in the official TAF
at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  52  63  56  66 /  40  20  80  40
INL  52  71  58  66 /  70  30  70  40
BRD  58  71  58  65 /  60  50  80  20
HYR  54  68  60  69 /  30  20  70  50
ASX  51  70  57  70 /  30  20  60  70

&&

.DLH Watches/Warnings/Advisories...
WI...Beach Hazards Statement until 8 PM CDT this evening for WIZ001.

MN...Beach Hazards Statement until 8 PM CDT this evening for MNZ037.

LS...Small Craft Advisory until 10 PM CDT this evening for LSZ121-
     146>148.

     Small Craft Advisory until 4 AM CDT Saturday for LSZ141>145.

&&

$$



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