Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 131411

Area Forecast Discussion
National Weather Service Duluth MN
911 AM CDT Sun Aug 13 2017

Issued at 857 AM CDT Sun Aug 13 2017

Adjusted pops based on current obs and trends. Meso models
indicate the forward edge of the precip will slowly work its way
east late this morning. There is dry air it still has to moisten
up before reaching the carlton county/twin ports region. If that
occurs, it won`t ne until the afternoon.  Rest of fcst unchanged.

UPDATE Issued at 645 AM CDT Sun Aug 13 2017

Please see the 12Z Aviation Discussion below.


.SHORT TERM...(Today through Monday)
Issued at 352 AM CDT Sun Aug 13 2017

As advertised, the upper level closed low has been making headway
into western Minnesota overnight. Early this morning the low aloft
was centered over North Dakota while at the surface the low was form
over the the lee of the Colorado Rockies with a trough extending
across south dakota into west central MN. Showers and storms were
occurring ahead of the forming low in the strong warm air advection
from north dakota, western MN, into Nebraska. With the evolving
surface pattern, in conjunction with the upper support, expect
the rain area to progress east into the DLH forecast area, first
in the southwest this morning, then spreading east and northeast
into the afternoon. The upper wave will be over MN tonight, then
traverse over Wisconsin on Monday, while the surface low cross
across southern MN and central WI. With this situation expect
plenty of moisture being advected into the region on 25 to 30 knot
low level jet. A strong baroclinic zone develops overnight across
the northland just south of the twin ports, so we will see a
prolonged period of rain across the southern forecast area,
mainly south of U. S. Highway 2 in MN and much of the northwest
corner of WI. Have not added chances of rain in far northern MN,
around the International Falls area as of now looks like the rain
will remain south of that area as models are keeping that area
under high pressure, but confidence is rather low and may need to
add some rain chances farther north.

.LONG TERM...(Monday night through Saturday)
Issued at 352 AM CDT Sun Aug 13 2017

A fairly active extended period with several periods where
there are chances of showers and thunderstorms. Temperatures will
remain near normal with highs in the 70s across the Northland. Low
temperatures will range from the upper 40s to low 60s.

Monday evening into Tuesday will be a transition period as a trough
digs from the western Great Lakes into the central Great Lakes.
Behind the trough, high pressure will build in. This will transition
cyclonic northwesterly flow, to westerly/southwesterly flow on the
western side of the ridge axis. In addition, low level flow will
become more southerly, which will advect warm, moist air into the
Northland. Will remain dry initially late Monday night into early
Tuesday as high pressure slides through. Precipitation chances will
increase from southwest to northeast Tuesday afternoon and evening
as a shortwave lifts across the northern Plains. At the surface a
broad area of low pressure will develop across the Dakotas. This
system will continue moving northeastward on Wednesday.
Thunderstorms still cannot be ruled out as there will be a few
hundred J/kg of MUCAPE to work with. PWAT values will range anywhere
from 1.5 to 2.0 inches on Tuesday and Wednesday, which is greater
than the 90th percentile based on SPC Sounding Climatology
information at INL and MPX for this time of year. GEFS current and
previous ensemble guidance show low probabilities of 1 inch of
precipitation in a 6 hour period on Tuesday and Wednesday. So, there
is potential for localized flooding due to heavy rainfall.

Current deterministic forecast guidance is in disagreement on how
quickly this system exits the region. The GFS is currently the
slowest piece of guidance, which lingers precipitation chances
across eastern Minnesota and northwest Wisconsin on Thursday. This
is due to the shortwave absorbing into a cutoff low located in
central Canada. The ECWMF/CMC are more progressive with the system,
lifting the shortwave into the central Great Lakes. Both the
ECWMF and CMC have the cutoff located across central Canada, but do
not have the shortwave being absorbed into the cutoff. Due to these
differences have low confidence in precipitation chances on
Thursday. The cutoff feature will be the main area of focus late in
the week and heading into the weekend. The ECMWF/GFS currently
depict a similar scenario where the cutoff rotates southeastward
from central Canada into western Ontario on Saturday. The CMC is a
bit faster, moving the cutoff into eastern Ontario, and western
Quebec. Behind the cutoff, a ridge will slide into the region from
the west on Sunday.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 645 AM CDT Sun Aug 13 2017

High pressure will build eastward into the central Great Lakes
today, while a broad area of low pressure moves into Minnesota.
Any radiation fog will dissipate this morning. Rain will
gradually spread eastward as Sunday progresses. This will
gradually lower ceilings to MVFR as the lower levels moisten. In
addition, visibility reduction is possible in areas of heavier
rainfall. Isolated thunderstorms are possible this morning and
afternoon. Due to the isolated nature of the activity, have held
off from including in the latest TAF set. IFR conditions may develop
at BRD/DLH and HIB between 20Z and 08Z per NAM/GFS guidance.


DLH  74  54  70  54 /  30  40  30  10
INL  77  51  77  52 /  10  10  10   0
BRD  66  55  72  56 /  70  60  20  10
HYR  75  55  70  53 /  30  60  60  10
ASX  79  56  72  53 /  20  50  50  10




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