Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 211947
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
247 PM CDT Wed Jun 21 2017

.SHORT TERM...(This evening through Thursday)
Issued at 247 PM CDT Wed Jun 21 2017

Overall a seasonal weather pattern through Thursday with a few
chances for precipitation on the way. Today there is a possibility
for two rounds of showers and thunderstorms for parts of the
Northland: first this afternoon with widely scattered showers and a
few embedded storms north of the Iron Range this afternoon, then a
second round of isolated, potentially strong to severe thunderstorms
across northern Minnesota this evening into tonight with additional
isolated to scattered showers/storms possible in northern Wisconsin.
Mainly sunny Thursday for areas north of the cold front Thursday
with a few post-frontal showers possible in northeast Minnesota.
Along the frontal zone in east-central MN into northwest Wisconsin
scattered showers and storms may develop in the afternoon.

On the synoptic scale a mainly zonal jet streak across the
CONUS/Canada border across much of North America will lead to a
fairly progressive pattern in the short term. A weak upper low
across central Manitoba will deepen as it drifts southeast today
into tomorrow with a surface low nearly co-located with the upper
low. An occluded front associated with this low stretches south
across central North Dakota, with a warm front from central ND
southeast across eastern SD towards western IA. As this front moves
east, a narrow ribbon of instability will advect northward into the
Red River Valley and east into northwest to north-central MN
tonight. With strong winds aloft and around 500-1000 j/kg MUCAPE
available, there is a narrow window for strong to severe storms to
develop along the frontal zone late tonight, mainly from the
Brainerd Lakes area north through Walker towards the international
border. As storms reach the US-53 corridor in northeast Minnesota
they are expected to weaken as they outrun the best elevated
instability, transitioning to showers. These showers may linger into
northwest Wisconsin late tonight. Patchy fog is possible behind the
front, mainly in the Brainerd Lakes to Lake Mille Lacs area. Lows in
the 50s.

On Thursday mainly sunny skies to start with highs rising into the
low to mid 70s, just about normal for mid to late June. A few post-
frontal showers are possible in northeast Minnesota but otherwise
just some clouds and breezy winds expected in NE MN. In northwest
Wisconsin closer to the frontal zone a late-day round of showers and
storms are possible, but severe storms are not expected.


.LONG TERM...(Thursday night through Wednesday)
Issued at 247 PM CDT Wed Jun 21 2017

The extended forecast period continues to highlight on-and-off
chances of showers and thunderstorms, along with a cooler than
normal weekend.

Some lingering small chances of showers and storms will be possible
Thursday night into Friday morning as a persistent cut-off upper-
level low continues to slowly advance eastward across extreme
northwestern Ontario Canada. A strong 110+ kt upper-level jet
situated over the southern periphery of the low will dive
southeastward during the day Friday. The best chances of these
showers/storms will be over the northern sections of the forecast
area as a stronger lobe of mid-level positive vorticity advection
will brush just across the Canadian border. The northwest flow
pattern continues through the day Friday, so more chances of
precipitation will continue, especially along the International
Border.

Friday night and Saturday morning look to be mainly dry until a more
compact and concentrated mid-level shortwave advances into the area
during the day Saturday. The 21.12z synoptic guidance is still
showing some disagreements in the spatial displacement of the trough,
with the GFS being the farthest south and quickest, compared to the
NAM and ECMWF solutions. This GFS solution is actually similar to
the 21.00z run from dProg/dt analysis, so there appears to be some
slight waffling in the model solutions. The overall consensus of
this wave is that the bulk of the vorticity will stay to the south
of the Northland. Still, the forcing for showers and storms will
remain, especially over the northern portions of the Northland where
isentropic upglide will be enhanced due to northerly flow on the
poleward side of the shortwave. Analysis of severe potential
Saturday afternoon and evening doesn`t show anything that really
stands out, except for increasing instability as low-level lapse
rates steepen. MLCAPE values should range from a few hundred up to
~700 J/kg, so not especially high. Deep layer shear and Pwat values
look pretty low as well, with values of 25-30 kts and 0.70 to 0.90",
respectively.

We will remain underneath the influence of an upper-level trough
that will continue to influence our weather pattern. A couple of mid-
level shortwaves will provide us with continued chances of showers,
and possibly some thunderstorms Sunday afternoon and evening. This
northwest flow around the cyclonic circulation of the upper-level
low will bring a few surges of cold air advection, so some cooler
temperatures will settle in for Friday through Monday, with high
temperatures in the lower to mid 60s, with some 70s creeping back
into the area for Monday. These temperatures are about 5 to 10
degrees below seasonal averages.


&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1252 PM CDT Wed Jun 21 2017

VFR conditions to continue across the Northland TAF sites through
the afternoon hours today. Some diurnal cumulus has developed over
mainly our eastern areas this afternoon, along with some high-
level clouds moving across north-central Minnesota. The potential
for showers and thunderstorms then increases later this
afternoon/evening and overnight as a warm front this afternoon,
followed by a cold front tonight, moves through the region. For
this afternoon, -SHRA will be possible, especially across our
northern TAF sites as the warm front moves through. Then, as the
cold front passes through later this evening and overnight,
chances of thunderstorms will increase. Some of these storms
could be strong, with gusty winds and small hail possible.
Confidence is higher for stronger thunderstorms the further west
and north you go, so KINL, KBRD, and KHYR will most likely see
these storms.

For our southern TAF sites, moisture pooling ahead of the cold
front will help to increase dew point temperatures, making the
development of areas of fog more likely, which could reduce into
MVFR categories, possibly into high-end IFR. The highest
confidence will be over KBRD and KHYR to see this. Ceilings may
also drop into MVFR as the cold front moves through.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  55  74  52  67 /  70  10  20  20
INL  52  71  51  62 /  80  10  30  40
BRD  56  73  53  66 /  50  20  10  10
HYR  59  75  52  69 /  50  40  20  20
ASX  55  76  53  69 /  60  20  20  20

&&

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

$$

SHORT TERM...JJM
LONG TERM...JTS
AVIATION...JTS



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