Area Forecast Discussion
Issued by NWS Duluth, MN

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249
FXUS63 KDLH 221739
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1239 PM CDT Sat Jul 22 2017

.UPDATE...
Issued at 659 AM CDT Sat Jul 22 2017

Update for new 12Z Aviation Discussion below.

&&

.SHORT TERM...(Today through Sunday)
Issued at 435 AM CDT Sat Jul 22 2017

At 430 AM, it was fairly quiet across the Northland. No showers
or thunderstorms were within our CWA borders at 430, although a
line of strong thunderstorms was moving toward our far southwest
CWA. There was quite a bit of fog across the Northland, with
localized visibilities down to a quarter mile. Temperatures ranged
from the lower 50s in the north to the mid 60s further south and
in several locations near Lake Superior.

The main focus for today will be the threat of severe weather.
SPC has our area in a Slight Risk, given a pre-frontal trough
expected to deepen over Minnesota during the day. A major upper
level shortwave will provide ample cooling aloft and substantial
height falls to produce a risk of severe thunderstorms across the
entire CWA this afternoon and tonight. The main risk will be very
large hail due to cold air aloft and strong westerly winds aloft,
but also a risk of damaging winds. CAM`s are all over the place,
so will tie the best chance of thunderstorms in with time of peak
heating and location of surface and upper level features. Will
generally keep POP`s in the scattered range, rather than likely,
as a good deal of the guidance indicates more scattered coverage.
Highs today are generally expected to reach the lower 80s.

Showers and thunderstorms should diminish tonight, as the upper
level trough/low move east, and the best forcing moves with it. A
few storms could even linger into Sunday morning, with the upper
low/shortwave lingering in the Lake Superior region for a time.
High pressure and building heights will then result in a drying
trend for the afternoon. Highs will be a bit cooler on Sunday,
with mainly 70s across the region.

.LONG TERM...(Sunday night through Friday)
Issued at 435 AM CDT Sat Jul 22 2017

Seasonal temperatures ahead for the long-term with a few
thunderstorm chances Monday night through Wednesday morning, then
again Thursday night.

Not much change in the forecast Sunday night through Wednesday
morning. Mid-level ridging will build into the Upper Midwest
Sunday night and continue on Monday with surface high pressure
drifting southeastward across the Northland. Mainly clear to
partly cloudy skies are expected with temperatures rebounding into
the low to upper 70s for Monday afternoon.

A shortwave trough is forecast to move across the northern
Canadian Prairies Monday night and Tuesday, with a surface low
moving from central Alberta to far northwest Ontario by Tuesday
night. A cool front will stretch to the southwest of the surface
low and should provide a focus for showers and thunderstorms late
Monday night through Tuesday evening. Winds aloft will turn south
to southwesterly Monday as the ridge passes east of the Northland.
A robust surge of higher theta-e air will advect northward ahead
of the approaching front, nosing into western Minnesota Monday
night and into the Northland on Tuesday. Precipitable water will
increase in the southerly warm air advection as well with forecast
values in the 1.5 to 2.0 inch range, well into the 90th
percentile for late July. Strong to severe thunderstorms are
possible Tuesday afternoon and evening.

A mid-level ridge will amplify over the western United States
Tuesday night and Wednesday with northwest flow developing over
the Northern Plains and Upper Midwest. A few showers are possible
Wednesday afternoon, but generally drier conditions are expected.
Weak surface high pressure is forecast to move through the Dakotas
and into Minnesota leading to partly cloudy skies. Temperatures
won`t cool much for Wednesday, only a few degrees from Tuesday`s
highs. Thursday should be relatively quiet as well before a weak
shortwave trough rides the northwesterly flow into the Northland
Thursday night and Friday morning. A few showers or thunderstorms
are possible as the disturbance moves through. High temperatures
Thursday and Friday will be in the low 70s to low 80s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1232 PM CDT Sat Jul 22 2017

The first area of concern is an area of stratus is affecting the
HIB and DLH airports with IFR-LIFR conditions. These clouds are
moving east and conditions should improve to VFR by 20z. The
second concern is development of thunderstorms this afternoon and
evening. The strongest storms should develop further east than
Friday and will be mainly east of a line from INL to AIT. MVFR-IFR
conditions will affect the INL/HIB/DLH/HYR airports after 22z
through 02z this evening. The BRD airport may stay precip free.
Overnight...conditions will be VFR-MVFR in morning fog with VFR
conditions at all airports on Sunday.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  73  57  70  52 /  40  40  20   0
INL  80  56  76  53 /  50  50  10   0
BRD  85  60  75  55 / 100  10  10   0
HYR  81  58  71  51 /  40  30  20   0
ASX  73  56  67  51 /  40  30  20   0

&&

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

$$

UPDATE...Huyck
SHORT TERM...DAP
LONG TERM...Huyck
AVIATION...Stewart



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