Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 270620

Area Forecast Discussion
National Weather Service Duluth MN
120 AM CDT Sun May 27 2018

Issued at 120 AM CDT Sun May 27 2018

Updated for the new 06Z Aviation Discussion below.


.SHORT TERM...(This evening through Sunday)
Issued at 329 PM CDT Sat May 26 2018

A hot and humid weekend continues for the Northland, with
temperatures as of this afternoon in the mid 80s to low 90s across
the southern half of the forecast area. However, along the
Canadian border, clouds and scattered showers and thunderstorms
have kept temperatures down in the 70s, with a pretty steep
gradient in between. The thunderstorms are being generated along a
weak east-west boundary with a pool of instability with CAPE
approaching 1000j/kg and 25-30knot shear, with a weak shortwave
rotating through the northwest flow aloft. The storms are
vigorous, but have not appeared severe so far. Tonight these
storms should weaken as the shortwave moves off to the east and we
lose the instability, and the surface boundary weakens even as it
becomes stalled across the area. Overnight temperatures to get a
little cooler than they did this morning, dipping into the 50s
most locations. Sunday to be another hot and humid one, with south
flow ahead of an approaching low pressure system brings additional
low level moisture into the area, and temperatures rise into the
mid 80s to low 90s everywhere. The low pressure system over South
Dakota should generate storms that slide into the forecast area
during the afternoon. However, this depends on the convection that
is expected to develop over MT today forming an MCS over North
Dakota overnight that diminishes before it reaches us in the
morning. Any cloud cover left over that reaches us could affect
high temperatures as well. For now am anticipating it falling
apart before that, and that we should get new development during
the late afternoon or early evening over northwest Minnesota that
slides in our direction.

.LONG TERM...(Sunday night through Saturday)
Issued at 329 PM CDT Sat May 26 2018

Sunday evening will find quasi-zonal flow over the Upper Midwest
and the Canadian Shield. Upper-level ridging will be focused over
the Mississippi River Valley with a closed upper low over the
Intermountain West. A shortwave trough and associated area of
vorticity will kick east of the low and ride north of the ridge,
moving across the Dakotas and into northern Minnesota and
northwest Ontario overnight. A strengthening low-level jet will
nose into the Northland and will increase convergence and
isentropic ascent over northern Minnesota just ahead of the
approaching shortwave. Thunderstorms are expected overnight and
the SPC has included our northern zones in a Marginal Risk of
severe weather as of this afternoon. Large hail, gusty winds, and
torrential rainfall are the greatest hazards from those storms.
With mean storm motion oriented along the front, training storms
are expected, which will increase the flooding potential.
Abundant moisture for heavy rain will be present with PWAT
forecasts of 1.5 to 1.8 inches.

Convection will taper off Memorial Day morning as the low-level
jet weakens and the front slowly sags southward. The
precipitation during the morning will enhance the cool side of
the boundary and set the stage for another round of strong to
severe storms during the afternoon through Monday night. PWATs
will be a little lower than Sunday night, around 1.4 inches, and
spread out across the Northland rather than pooling near the
front. Heavy rainfall will be possible once again. Large hail and
damaging winds will be possible with the strongest storms.
Temperatures will be very warm for Memorial Day with highs in the
80s to low 90s, except near Lake Superior where 70s to low 80s
are expected.

A pattern shift begins on Tuesday as the upper-level ridge begins
to move eastward ahead of an approaching trough. Southerly flow
will continue over the Upper Midwest with temperatures climbing
into the 80s for most areas. Showers and thunderstorms will
percolate during the late afternoon and evening hours once again,
and a few strong storms are possible. The trough will gradually
move eastward Wednesday and Thursday keeping showers and storms
in the picture and ushering in cooler, but still above normal,
temperatures. Friday appears dry as of this forecast as high
pressure passes north of the region.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 120 AM CDT Sun May 27 2018

An active weather pattern will persist across the Northland
throughout the next few days, as warm and humid air continues to
settle into the region. Some showers and thunderstorms will be
possible from Sunday afternoon into Sunday night, especially
across the north. While we expect largely VFR conditions during
this TAF cycle, there could be some MVFR CIG`s and VSBY`s in
association with thunderstorms. In addition, there could be some
localized fog overnight, especially at KHIB.


DLH  57  90  59  80 /   0  10  40  20
INL  55  86  57  83 /   0  30  60  20
BRD  60  92  64  92 /  10  10  20  10
HYR  59  92  65  92 /   0   0  30  20
ASX  50  89  57  81 /  10  10  50  20




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