Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 150542
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1242 AM CDT Tue Aug 15 2017

.UPDATE...
Issued at 1242 AM CDT Tue Aug 15 2017

Update for new 06Z Aviation Discussion below.

UPDATE Issued at 920 PM CDT Mon Aug 14 2017

Only some minor updates to the evening grids and products. Skies
had generally cleared across most of the CWA. The exception was
the redevelopment of some MVFR CIG`s in northwest Wisconsin. In
addition, fog was starting to develop across the region. We should
see a continued expansion of fog overnight. A few showers will
still be possible late this evening in the Minnesota Arrowhead.
Other than that, only minor changes and a quiet night.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 342 PM CDT Mon Aug 14 2017

A trough of low pressure continued to move through the Northland
this afternoon and will continue east and south overnight. Showers
and a few thunderstorms have developed as far west as the Brainerd
Lakes region with coverage highest over the Arrowhead and parts of
northwest Wisconsin. The showers and storms will diminish in
coverage into the early evening hours then end overnight. Ridging
will build in overnight leading to light winds and clearing skies.
Fog will develop overnight and it may be dense in spots.

The fog will lift Tuesday morning with dry conditions expected
through the day. Surface high pressure will move off to the east and
winds will be east to southeast at 10 mph or less for most areas
except close to Lake Superior where they will be a bit stronger.
Highs will be in the seventies for most areas. Clouds will be on the
increase through the day with mostly cloudy conditions developing by
late afternoon from the Brainerd Lakes region toward northwest
Minnesota.

.LONG TERM...(Tuesday night through Monday)
Issued at 342 PM CDT Mon Aug 14 2017

The primary concern during the long term continues to focus on
rain chances and amounts late Tuesday night through Thursday
morning.

Omega blocking pattern will remain in place over the North
American continent Tuesday evening. A progressive shortwave
trough will rotate through the base of the western cutoff low and
moving into the Northern Plains. An inverted trough at the
surface will be accompanied by developing low pressure in the low-
levels ahead of the mid-level wave. Robust poleward moisture
return with precipitable water forecasts between 1.5 and 2 inches
by Wednesday will increase the potential for heavy rainfall. Rain
and isolated thunderstorms are forecast to arrive in our
southwest Tuesday night and spread across the remainder of the
forecast area on Wednesday morning. Guidance today has trended a
little slower with the precipitation, which makes sense
considering the overall blocking pattern. Wouldn`t be surprised
if the heaviest rainfall shifts later in time, yet again, with
subsequent updates. Rainfall amounts between 1 and 2.5 inches are
possible with the heaviest totals stretching from southern Aitkin
and western Pine County northeast through the Twin Ports and
along the North Shore. The rainfall is expected over a prolonged
period, and with a low amount of instability forecast with the
surface trough, rain rates should be modest. The slower
progression and low instability will keep the flash flood risk
low. Area streams, and especially mainstem rivers, should have
enough reserve capacity to handle the rainfall, which also
decreases the flash flooding risk.

Drier conditions return to the Northland Thursday night and
Friday morning before the next progressive shortwave trough moves
through the region between Friday afternoon and Saturday morning.
Scattered showers and isolated thunderstorms are possible, but
rain amounts should be light. Another system moves into the Upper
Midwest Sunday night, which could bring a round of showers and
storms.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1242 AM CDT Tue Aug 15 2017

High pressure will lead to clearing skies overnight along with widespread
fog, which is expected to develop across most of the terminals
and is already being seen at KHYR, KBRD and KHIB. KINL should
remain VFR or MVFR overnight, but the remainder of the terminals
will reach down to IFR and LIFR CIGS/VSBYS, with times of VLIFR
at KHYR, KBRD and KHIB. VSBYS/CIGS will quickly improve after
sunrise with VFR conditions returning and remaining through the
day. Clouds will be on the increase heading into Tuesday night and
will see ceilings drop, but any drop below VFR CIGS should occur
after the forecast period.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  53  73  57  66 /  20   0  40  90
INL  48  78  57  69 /  20  10  20  80
BRD  53  75  60  70 /  10  10  70  90
HYR  49  77  58  74 /  20   0  10  80
ASX  51  74  55  73 /  20   0  20  60

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&

$$

UPDATE...BJH/DAP
SHORT TERM...Melde
LONG TERM...Huyck
AVIATION...BJH



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