Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 191154
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
654 AM CDT TUE JUL 19 2016

.SHORT TERM...(Today through Wednesday)
Issued at 403 AM CDT Tue Jul 19 2016

At 400 AM, it was quiet across the Northland. Temperatures ranged
from the mid 40`s at Crane Lake, Cook and at the Grand Marais
Airport, to the lower 60s across much of the southern portion of
the CWA. Skies were generally clear area-wide.

It`s hard to imagine we are talking about some of the hottest air
of the season being here this week, with temperatures dropping
through the 40`s across much of northern Minnesota. Light winds
under high pressure were causing optimal radiational cooling
across the Arrowhead region. Things will change considerably after
this morning, as we will see hot and humid air advect in on
southerly winds.

For today, a day of transition, as upper level ridging moves
across Minnesota during the day. Temperatures should easily climb
into the lower to middle 80s this afternoon, as higher dewpoint
air pushes into the southwest portion of the CWA during the day.
As higher dewpoint air spreads into the area on southerly winds,
it will bring unsettled air into the far west and southwest. Will
continue a small mention of showers and thunderstorms across that
area, especially from mid to late afternoon.

A better chance of showers and thunderstorms will come tonight, as
a shortwave embedded in upper level westerly flow will move just
south of the CWA. At this point, it looks like the heaviest
rainfall will be south of the CWA. The models really are having a
tough time resolving various precipitation threats, but think the
best chance of showers/storms tonight will be in the far south.
Will continue mention of showers and storms on Wednesday as well,
as another upper level shortwave slides across the area. The
remnants of this system should all but exit the region on
Wednesday Afternoon. Some of these storms could be strong, or
potentially severe on Wednesday.

The big story will be the high heat and humidity. Temperatures on
Wednesday will reach the upper 80s to lower 90s, with Heat Index
values reaching 95 to 105 across at least the southern portion of
the CWA. Have added another tier of counties to the current
Excessive Heat Watch, now including the zones that include Duluth,
Superior, Bayfield, Ashland and Hurley.

.LONG TERM...(Wednesday night through Monday)
Issued at 403 AM CDT Tue Jul 19 2016

Hot and humid mid-week then returning to near-normal temperatures
this weekend. A chance for showers and storms late Wednesday night
into Thursday, then low chances for storms through the weekend. At
this point widespread severe storms are not anticipated but a few
strong storms will be possible Thursday and then again Saturday
afternoon into Saturday night.

On the synoptic scale the upper high/ridge across the Great Plains
will peak in strength Wednesday night. The placement and strength of
the ridge has been fairly well predicted, with a slight trend
southward and just a tad bit weaker than originally modeled a few
days ago. Still...near-record heat is expected Thursday with the
strong southwest flow at low levels Wednesday and Thursday bringing
in very warm and moist air. Dew point values on Thursday could
approach the upper 70s in northwest Wisconsin...downright oppressive
humidity. Added the rest of northwest Wisconsin and the
Carlton/South St Louis (including Duluth) zone to the Excessive Heat
Watch as confidence has increased in the extreme heat index values
approaching 100 nearing the shoreline of Lake Superior due to the
south/southwest winds at the surface.

On Thursday a mid-level trough comes across southern Canada with a
resulting surface trough/weak low ahead of it across the upper
Midwest. This will result in at least scattered convection across
northeast Minnesota into northwest Wisconsin around the ridge
Wednesday night into Thursday. While the mid and upper level winds
would favor an MCS evolution, the low level winds do not appear
particularly favorable for such a convective mode...thus think
cycling clusters of storms, some strong, will move across the region
but an organized widespread threat for severe weather is not likely.

As this trough moves across it will wipe out some of the warmest air
resulting in not as hot conditions on Friday, but as a stronger mid-
level trough approaches across the intermountain west on Friday the
mid-level ridge axis again builds across the upper Midwest resulting
in warm southwest flow at low levels with highs in the mid to upper
80s away from Lake Superior...but with less low level moisture heat
indicies will not be as high. A slight chance for storms on Friday
given the instability aloft and weaker inhibition due to not-as-hot
low/mid level temps, but the better chance for storms will be late
Friday night into Saturday night as a warm front lifts northeast
through the upper Midwest then a cold front approaches from the
northwest all associated with the mid-level trough moving east
across southern Canada.

Late Sunday into Monday the then-mature low traverses across Lake
Superior, with the Northland in relatively cooler northwest flow in
the wake of the low. This will result in a chance for showers and
possibly a few storms Monday. Beyond this guidance begins to really
diverge, but generally warming to seasonable temperatures with a
low chance for showers and storms through mid-next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 654 AM CDT Tue Jul 19 2016

VFR conditions are expected to prevail through the TAF period with
a chance for MVFR visibilities late tonight as the chance for
showers and thunderstorms increase. Today will be mostly sunny
with a light south wind, breezy at times at BRD. Increasing clouds
this evening with a chance for showers and thunderstorms at all
sites. At this point confidence is still low in the coverage of
showers and storms so kept the TAFs VFR for now, but some brief
MVFR visibilities are possible.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  80  64  86  69 /  10  40  30  30
INL  83  68  91  68 /  10  50  20  50
BRD  85  71  90  72 /  40  50  10  10
HYR  86  69  88  70 /  10  50  40  20
ASX  78  65  88  68 /  10  30  40  30

&&

.DLH Watches/Warnings/Advisories...
WI...Excessive Heat Watch from Thursday morning through Thursday
     evening for WIZ001>004-006>009.

MN...Excessive Heat Watch from Wednesday afternoon through Thursday
     evening for MNZ025-033>038.

LS...None.
&&

$$

SHORT TERM...DAP
LONG TERM...JJM
AVIATION...JJM


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