Area Forecast Discussion
Issued by NWS Duluth, MN

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136
FXUS63 KDLH 212344
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
644 PM CDT Mon Aug 21 2017

.UPDATE...
Issued at 630 PM CDT Mon Aug 21 2017

Have updated for the showers blooming across the area this evening
in an area of instability ahead that has developed along and ahead
of an inverted trough and shortwave that is going to be moving
through the area this evening. In general have increased both pops
and cloud coverage, with some thunder across the southern forecast
area. Also...updated aviation section below for 00Z TAF TAF
issuance.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 321 PM CDT Mon Aug 21 2017

An approaching upper-level trough, and embedded shortwaves within
the westerly flow aloft, are and will be bringing areas of
forcing for ascent across the Northland through this evening.
Passing surface low pressure across the southern forecast area
will likely interact with this forcing to help produce some
showers and storms across northwest Wisconsin late this afternoon
through this evening. The storms should be relatively weak, but
there could be some stronger storms near Price County capable of
gusty winds and small hail. The storms could have brief downpours
of rain considering the deep moisture in the atmosphere, with
precipitable water values around 1.5 inches.

Also, the main upper-trough will swing through the Northland this
evening and overnight. It could bring a period of clouds and some
light rain over the western forecast area. Drier and cooler air
will filter into the Northland amidst the northwest flow
overnight. There should be a clearing trend later tonight. The
winds might be light enough in the early morning to result in some
patchy fog. Lows will range from the upper 40s to lower 50s.

The Northland will be in cool northwest flow Tuesday. Sunny skies
in the morning will quickly heat things up and deep mixing will
develop by the afternoon. Windy conditions will develop. The GFS,
NAM, and regional Canadian models are suggesting the mixing will
be strong enough to draw down 20 to 30 mph flow from aloft. Have
widespread 20 to 25 mph gusts in the afternoon, and some areas
will see occasional gusts to 30 mph, like in Duluth. A weak cool
front will dip into far northern Minnesota in the late afternoon,
and some light showers will likely develop up there. Highs should
be in the upper 60s and lower 70s.

.LONG TERM...(Tuesday night through Monday)
Issued at 321 PM CDT Mon Aug 21 2017

Cooler mid to late week with a chance for rain showers this
weekend.

On the synoptic scale northwest flow will prevail across the
Upper Midwest mid to late week as a longwave mid-level ridge
approaches the Great Plains. A broad area of high pressure will
build over the Upper Great Lakes, then track eastward this
weekend. A chance for a quick-moving mid-level shortwave to bring
a round of showers late Wednesday or early Thursday, though
confidence in exactly where rain would fall is below normal. A
warm front lifting northeast towards the region on Friday will
lead to increasing clouds and a chance for showers, then
additional chances for precipitation Saturday as a cold front
moves though. Model differences through the weekend lead to a long
period with chances for rain showers, but most solutions are not
a washout for all locations. A few thunderstorms are possible
Saturday and Sunday as the front moves through, but at this point
the threat for storms does not seem sufficient to include a
mention in the forecast.

Temperatures will be cooler than usual mid to late week with
highs in the 60s to near 70 through the long term period. As cool
as the mid 30s for parts of far northern Minnesota, though
depending on the track of the mid-level wave coming through
Wednesday night temperatures may not fall as cold as currently
anticipated. Otherwise lows in the 40s to 50s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 630 PM CDT Mon Aug 21 2017

Showers and a few thunderstorms are moving across the area this
evening, and will continue for at least a few hours as an
inverted trough and upper level shortwave moves across the area.
While sites are generally VFR, showers/thunderstorms may bring a
period of MVFR ceilings with IFR visibilities to each site as they
move across. There may also be a period of MVFR ceilings that
linger behind the showers/thunderstorms, but these should clear no
later than 04z most sites, but linger longer at KHYR where it may
linger as late as 10z. Otherwise, VFR conditions are expected to
return for the remainder of the TAF period. Northwest winds are
expected to increase after 14z, and should blow around 15 kts with
gusts in the 20-25kt range.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  52  71  50  66 /  40   0   0  10
INL  47  70  45  67 /  40  20   0  10
BRD  53  72  49  68 /  10   0   0  20
HYR  51  71  48  67 /  40   0   0  10
ASX  54  72  51  67 /  40   0   0  10

&&

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

$$

UPDATE...LE
SHORT TERM...Grochocinski
LONG TERM...JJM
AVIATION...LE



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