Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 171809
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
109 PM CDT Sat Jun 17 2017

.UPDATE...
Issued at 1258 PM CDT Sat Jun 17 2017

Updated aviation section below.

UPDATE Issued at 917 AM CDT Sat Jun 17 2017

Plenty of clouds over the northern half of the forecast area this
morning. This is north of a stationary front which is draped over
the Iron Range. More sun than clouds over the South. The rain
showers are persisting from CDD southeast to BFW and through the
Arrowhead. Some light rain has occurred at Walker recently. Have
updated to account for these trends and more sun in northwest
Wisconsin.

&&

.SHORT TERM...(Today through Sunday)
Issued at 251 AM CDT Sat Jun 17 2017

The Northland`s weekend will begin relatively warm and humid, with
high odds of showers and thunderstorms this afternoon and evening.
A passing cold front this afternoon and this evening will bring
cooler weather for Sunday. Some showers are possible Sunday, too.

At 330 AM, there was a vertically-stacked area of low pressure
over far northern Ontario. Its surface cold front extended down to
northwest Minnesota and eastern North Dakota. A weak upper-level
trough was over the eastern forecast area and moving east, and the
Northland was in zonal flow. An upper-level trough and 120 knot
jet streak were digging across the northwest US. There were
showers over the Minnesota Arrowhead, as well as some isolated to
scattered showers over parts of far northern Wisconsin into north-
central Minnesota. Much of the Northland had broken to overcast
cloud cover, calm winds, and relatively humid conditions in the
50s. There were some spots with fog.

The showers across the Northland will generally decrease in
coverage heading into dawn with the exiting weak upper-trough.
There may be only light showers here and there across northern
Minnesota by around and in the few hours after dawn.

A warm day will set up with the light westerly flow. Temperatures
will climb into the 70s. There will be increasing chances of
showers and thunderstorms this afternoon into this evening. A cold
front will move south through the Northland, which will be the
main trigger, at least at first, for showers and storms. However,
the upper-trough over the northwest Wisconsin will begin
approaching the Northland later today. It will bring substantial
large-scale lift into the Northland by late today, especially
near the southern forecast area ahead of the deepening upper-level
low within the trough. So while most of the showers and storms
will mainly be along and near the cold front across northern
Minnesota earlier in the afternoon, there may be some showers and
storms that develop farther south because of daytime heating and
the increasing large-scale lift. Scattered showers and
thunderstorms are likely across much of the Northland by this
evening, with the heaviest activity along and near the cold front.

Severe weather is not expected today due to the lack of instability
and deep-layer wind shear. However, there may be a period of about
500 to 1000 J/kg of mixed-layer CAPE, 25 to 30 knots of 0-6 km
wind shear, and freezing levels around 10 to 11 kft. This might be
the kind of environment to support some brief strong storms late
this afternoon and this evening, capable of pea size hail.

The cold front will continue moving through the southern forecast
area late this evening through the rest of the night. There will
be a quite a bit of large-scale lift, maximized near the southern
forecast area because of the deepening upper-level low within the
passing upper-trough. This will bring high chances of showers and
some storms to the southern forecast area overnight. Overnight
lows will be in the low to middle 50s.

The upper-trough will exit east of the Northland Sunday. Cool and
breezy northwest flow will develop across the Northland. Expect
extensive cumulus and isolated to scattered light showers. There
could be some thunder across the eastern forecast area in the
afternoon when a weak upper-trough passes through the region
during peak heating. Highs will be in the low to middle 60s.

.LONG TERM...(Sunday night through Friday)
Issued at 351 AM CDT Sat Jun 17 2017

A subtle, but somewhat significant pattern change is expected mid
week, as somewhat amplified mid level flow flattens, with a more
progressive westerly flow pattern expected for later this week
which should allow for periodic chances for thunderstorms through
much of the week.

Initially, the DLH CWA is expected to lie underneath northwest
flow aloft on the back side of the departing trof Sunday night and
Monday. There could be a few lingering showers or thunderstorms
Monday-Tuesday time frame, first lingering from the departing
front, and then again in the afternoons/evenings with daytime
instability and a disturbance rotating southeastward on the back
side of the trof.

As the trof over the Great Lakes deamplifies and moves eastward
Tuesday, stronger mid level westerly flow will overspread most of
the U.S.-Canada border region from the west coast to the western
Great Lakes by mid week according to most mid-range model
guidance. This will allow for a warming trend, along with the
northward expansion of the Plains instability axis with time.
Thus, any disturbance will have some potential for initiating a
few thunderstorms. Both the ECMWF and GFS continue to advertise a
more significant wave traversing the northern tier of states Wed
night/Thursday, which would result in a more substantial threat
for thunderstorms.

However, as is the case more often than not this time of year,
the timing of individual bouts of convection is exceptionally
difficult beyond about 24 hours, due to the cumulative integrated
effects of daily bouts of convection and subsequent
boundaries/effects on the following day(s) instability. We have
not deviated much from consensus guidance for the Mon-Fri time
frame, with at least some small risk of t-storms somewhere just
about every day this coming week. The best chances for organized
storms and at least some potential for severe weather and/or heavy
rainfall at this time, appears to be with the advancing wave and
moisture/instability push into the region Wed night through Thur
night.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1258 PM CDT Sat Jun 17 2017

Initial VFR conditions with scattered showers and a few
thunderstorms across the area. Under the showers and storms a
period of MVFR ceilings/visibilities can be expected. These
showers and storms are forming in advance of a disturbance and
associated weak cold front that is moving rapidly towards the
area this afternoon and will continue through the evening. The
highest confidence in coverage is across the southern terminals
from 20z through 02z, and have put in tempo groups for thunder for
KDLH, KBRD, KHYR and KHIB, but for a shorter time frame. Behind
the cold front winds will turn to light northwest, MVFR ceilings
are expected to spread into the area from the northwest after 06z.
The MVFR ceilings...along with scattered showers expected to
continue through approximately 17z.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  75  54  66  49 /  60  60  50  20
INL  69  52  62  47 /  60  30  30  10
BRD  76  55  66  50 /  70  70  20  10
HYR  79  56  67  50 /  50  70  60  30
ASX  79  53  66  50 /  50  70  60  30

&&

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

$$

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



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