Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 210920

Area Forecast Discussion
National Weather Service Duluth MN
420 AM CDT Fri Jul 21 2017

.SHORT TERM...(Today through Saturday)
Issued at 420 AM CDT Fri Jul 21 2017

At 4 AM, regional radar depicted a small area of showers and
thunderstorms along the border with Canada, generally in the
vicinity of Lake of the Woods. This area of showers and storms was
moving east along the border region, and should roll into
International Falls. Elsewhere, we were seeing an increase in
high clouds across the CWA. There was some patchy fog across the
area as well. Temperatures ranged from the middle 40s in the
interior portions of the MN Arrowhead, to the mid to upper 60s in
the Brainerd Lakes region, and in a few places near Lake Superior.

Severe weather is the main focus for today through Saturday. The
latest Day One Outlook from the Storm Prediction Center has a
portion of our area in an Enhanced Risk of severe thunderstorms
this afternoon and evening. This area basically includes our
southwest corner of the CWA, including the Brainerd Lakes region
and east central Minnesota. Buffering the Enhanced Risk was a
Slight Risk stretching from Park Falls, to Duluth, to Bigfork and
Birchdale. The main question at this point is timing and expected
threats from the severe weather. A thorough analysis of the CAMs
showed several possible solutions, although overall there was
consensus that a large complex will slide along our southern
counties this afternoon. As a result, we will have the highest
POP`s in that area this afternoon. Meanwhile, the CAMs indicate
that an area of thunderstorms will develop west and north of the
CWA late this afternoon, and will slide southeast across the
Enhanced to Slight Risk areas during that time. Consensus on any
particular solution is much lower, but in terms of mass fields,
the above mentioned are the better opportunities for strong to
severe thunderstorms. Strong heating in the Red River Valley,
along with cooling temperatures aloft, will combine with a pre
frontal trough to cause steep lapse rates, with the potential for
explosive thunderstorm development, as noted by SPC. The storms
should initially be cellular, with large hail, but then transition
to a wind event as it dives southeast across Minnesota and
portions of Wisconsin. Will strongly highlight the risk of severe
thunderstorms in the southwest today and this evening.

More thunderstorms are expected on Saturday, with a Slight Risk of
severe storms across the CWA, mainly during the period of peak
heating. Surface heating and cooler temps aloft should lead to the
potential for organized storms during the afternoon and evening.

Highs will be in the upper 70s to middle 80s today through

.LONG TERM...(Saturday night through Thursday)
Issued at 420 AM CDT Fri Jul 21 2017

The main concerns in the long term include a chance of strong
thunderstorms lingering into Saturday evening and thunderstorm
chances Tuesday through Thursday night.

A compact shortwave trough is forecast over northwest Ontario and
northern Minnesota Saturday evening with mid-level height falls
across much of the Northland. Showers and storms may be ongoing
during the evening hours and are expected to weaken overnight.
Instability on the order of 500 to 1500 J/kg of MUCAPE and 0-6 km
shear of 30 to 45 knots would continue to support storm-scale
organization with large hail and damaging wind gusts possible.
The shortwave trough and associated vort max is expected to slide
southeastward into the central Great Lakes on Sunday keeping only
a slight chance of showers or an isolated thunderstorm in the
picture. Temperatures will trend cooler for the second half of
the weekend with highs in the middle 60s northeast to the middle
70s in the west.

A low amplitude mid-level ridge will build across the Northern
Plains and the Canadian Prairies Sunday night through Monday night
with surface high pressure moving gradually eastward through the
region. Look for mainly sunny to partly cloudy skies with slowly
moderating temperatures for the start of the work week. Another
shortwave trough will move across the northern Canadian Prairies
Tuesday through Wednesday. Surface low pressure will move
eastward across central Saskatchewan and Manitoba, and into far
northwest Ontario Tuesday evening. A cool front will accompany the
surface low, and will extend southward into the Northern Plains
moving through the Northland on Tuesday. Showers and thunderstorms
are possible along and ahead of the front, especially Tuesday
afternoon and evening.

The cool front will stall out over the Dakotas through the
Midwest. Another ripple in the mid-level flow and convergence in
the baroclinic zone should give rise to thunderstorms Wednesday
afternoon. The storms are expected to move eastward along the
quasi-stationary front and may graze the Northland Wednesday
night and Thursday. Temperatures for the latter portion of the
week will trend near normal with highs in the low 70s to near 80


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1253 AM CDT Fri Jul 21 2017

Another round of MVFR to IFR fog will develop overnight at some
TAF sites, with BRD and HYR most likely to fall to IFR visibility
at times overnight. A chance for a shower at INL overnight,
otherwise increasing VFR clouds at all sites through the TAF
period. Calm winds overnight becoming generally southeast at 5-10
knots Friday, with a few gusts to near 20 knots at BRD. Exception
will be at DLH where wind direction is expected to shift to more
east-northeasterly in the afternoon.

Confidence in convection on Friday is generally low, with a low
chance for showers or storms throughout the day at BRD, then a
better chance for storms at BRD, DLH, and HYR in the evening hours.
However, it is possible the storms set up south of these sites, so
due to low confidence have only included a VCSH mention until timing
of thunderstorms can be predicted with some level of certainty.


DLH  80  59  73  57 /  30  30  30  30
INL  82  60  77  56 /  20  50  50  50
BRD  83  64  82  60 /  50  70  20  10
HYR  85  64  79  58 /  50  70  20  30
ASX  82  59  73  56 /  30  30  30  30




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