Area Forecast Discussion
Issued by NWS Duluth, MN

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181
FXUS63 KDLH 261755 AAC
AFDDLH

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
1255 PM CDT Fri May 26 2017

.UPDATE...
Issued at 1255 PM CDT Fri May 26 2017

Update for new 18Z Aviation Discussion below.

UPDATE Issued at 1142 AM CDT Fri May 26 2017

A mix of clouds across the western half of the forecast area has
allowed temps to reach 70F. Farther east, plenty of clouds are
keeping temps down. Some showers continue to percolate over the
Arrowhead, western Lake Superior, to the Apostle Islands. Moisture
is on the increase ahead of a surface trof in western Minnesota
with dewpoints into the 50s. Made some adjustments to account for
the showers, raise the max temps where more sun is found, and
cloud cover.

&&

.SHORT TERM...(Today through Saturday)
Issued at 341 AM CDT Fri May 26 2017

An upper level low and surface low were located along the
Manitoba/Saskatchewan border, just west of Lake Manitoba. A
frontal boundary stretched from this low through the Red River
Valley and south. A shortwave and area of warm air advection were
causing showers over the Northland early this morning and these
should continue to move east exiting most of the area early. A
shortwave will move through the Northland today into this evening
along with the front. There will likely be a lull in shower
coverage this morning across most of the area but then as the
airmass heats and moistens through the day, showers and a few
thunderstorms will develop with coverage greatest along and just
ahead of the frontal boundary. The front will just be entering our
western CWA early this afternoon progressing east this afternoon
and overnight. The precipitation coverage will diminish this
evening and overnight with loss of heating. Weak shortwave ridging
will develop tonight which will bring a dry period later tonight
into at least Saturday morning. Expect highs today from the upper
sixties to lower seventies. It will be cooler around Lake
Superior.

The upper low will be moving slowly east to northeast tonight into
Saturday with an upper trough extending well south through the
region. Another shortwave and surface trough will start to affect
portions of the Northland Saturday afternoon and we have low
chances for showers or thunderstorms across mainly our northwest
CWA. Some of the guidance shows the showers developing elsewhere
across the CWA but we went with overall consensus which keeps them
mainly over the northwest quarter of Minnesota and south of
northern Wisconsin. Highs will be in the upper sixties to lower
seventies and winds are expected to west to southwest.

.LONG TERM...(Saturday night through Thursday)
Issued at 341 AM CDT Fri May 26 2017

The long-term forecast period begins with a closed upper-level low
progged to be situated over eastern Manitoba/western Ontario Canada
will very slowly translate eastward, remaining just north of the
Northland Sunday and Monday. The associated mid-level shortwave
component of this system will continue bringing a series of
shortwave impulses that will affect the region, keeping the
Northland under chances of precipitation. Some embedded positive
vorticity advection and isentropic lift will provide the forcing for
these rain showers and possibly some thunderstorms, especially
Sunday afternoon as 0-3 km low-level lapse rates steepen to between
6 to 9 degrees C/km. MUCAPE instability values vary between the
primary medium range guidance, but could range between a few hundred
J/kg up to around 1300 J/kg. So, there should be some decent
instability in place for thunderstorms on Sunday. Storms are not
expected to be severe.

There does appear to be a subtle cold frontal boundary that looks to
sweep through the Northland for early Monday as evident in the 925
mb temperatures, where we go from a range of 9 to 13 degrees C at
00z Monday across the Northland to 6 to 9 degrees C 00z Tuesday.
This will translate to cooler temperatures Monday and Tuesday, with
high temperatures in the mid 50s to lower 60s.

Temperatures return to more seasonal values beginning Tuesday as a
push of 850-700 mb layer warm air advection moves through. The
models differ on chances of precipitation for Tuesday and early
Wednesday as the ECMWF continues precipitation chances over the
Northland, while the GFS/CMC models keep conditions dry Tuesday
night into Wednesday. The consensus blends bring in a chance of
precipitation Wednesday morning and into the afternoon, but only a
small chance, mainly from the Iron Range southeast over the head of
Lake Superior and into northwest Wisconsin. Due to the model
uncertainty, will maintain the consensus blends for now.

Dry period from Wednesday evening through Thursday afternoon as high
pressure situated over Saskatchewan and Manitoba Canada takes
control over the region, and continues through the rest of the
forecast period.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1255 PM CDT Fri May 26 2017

A trough of surface low pressure was located over central
Minnesota this afternoon with several subtle elevated troughs from
near the surface feature westward into eastern North Dakota. A
robust cumulus field has developed along and behind the surface
trough with the strongest updrafts ahead of each upper-level
trough. Showers and thunderstorms have begun to develop over
northern Minnesota, and additional development southward is
expected through this afternoon. Think the best thunder potential
at the terminals will be limited to a 2-3 hour window as the
surface trough pushes eastward. Winds will veer westerly late this
afternoon or tonight. HYR may experience a brief period of IFR
visibility late tonight and model guidance points to lower
visibility. Models also point to the potential for fog at DLH.
With the scattered nature of the rain this afternoon, and limited
amounts expected, don`t have much faith in visibility
restrictions. Kept the 3SM mist at HYR from earlier shift, but
moved the timing earlier in the night. High clouds drift into the
Northland Saturday morning with primarily VFR conditions expected
during the morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  66  45  70  47 /  60  30  10  30
INL  72  45  70  46 /  30  20  30  20
BRD  75  47  72  49 /  10  10  10  30
HYR  74  47  73  48 /  40  50  10  30
ASX  71  47  71  47 /  40  50  10  30

&&

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

$$

UPDATE...Huyck
SHORT TERM...Melde
LONG TERM...JTS
AVIATION...Huyck



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