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Area forecast discussion...updated
National Weather Service Duluth Minnesota
1243 PM CDT Wed Jun 28 2017

Update...
issued at 1009 am CDT Wed Jun 28 2017

Updated precipitation trends based on radar data and high
resolution model guidance. Still think the highest rainfall totals
in our area will be found in Sawyer and Price County through
tonight. Hrrr and hires windows all point to thunderstorms with
between 1 and 2 inches of rainfall this afternoon over much of
northwest Wisconsin. The exact placement of the heaviest rainfall
varies between models, but the fact that each have swaths of
nearly 2 inches of rain is an important signal. Raised quantitative precipitation forecast values
over Sawyer, Ashland, Iron, and price counties, with the highest
amounts in southern Sawyer and southern price. Maintained a
consensus approach to quantitative precipitation forecast for this afternoon which smooths out and
lowers maxima, but think there is a good likelihood of a few
spots exceeding 2 inches of rain today/tonight. Updated pops based
on recent radar trends. Remainder of the forecast largely
unchanged.

&&

Short term...(today through thursday)
issued at 345 am CDT Wed Jun 28 2017

A more active day of showers and thunderstorms will develop later
this morning and continue into this evening. A potent system,
associated with deep lift as evidenced by upper-level divergence
and a mid-level shortwave trough, will enter the region today. In
the low-levels, a 35 to 40 kt low-level jet will intensify later
this morning, with the nose of the jet situated right over the
Northland. Enhanced moisture transport will result from this low-
level jet, with pwat values in the 1.3 to 1.6" range, and surface
dewpoint temperatures forecast in the lower to mid 60s this
afternoon. Naefs analysis of these precipitable water values continue to
indicate well above climatological averages for this time of the
year, with these values >90% of climatology. Heavy rainfall, with
some localized flooding, will be possible later this afternoon and
evening, with the heaviest amounts expected to be over portions
of northwest Wisconsin, where over one inch of rainfall will be
possible. The focusing mechanism for convection will be a low-
level baroclinic zone that will develop along a warm front
boundary over our southern portions of the forecast area. Corfidi
forward propagation vectors indicate a nearly due-east component
of motion with this convection, which would be right along the
baroclinic zone, so training convection will be possible. Wpc's
latest day 1 excessive rainfall forecast has removed the slight
risk of excessive rainfall from the forecast area, leaving only
the marginal risk area over northwest Wisconsin and points north
and west into northeast Minnesota. Total precipitation through
Thursday morning across the area could range from one-half of an
inch in portions of northeast Minnesota to over one inch in
northwest Wisconsin.

There is an increased chance of strong to severe convection with
this system, albeit still a low risk. The 28.00z synoptic guidance
is now indicating the stronger axis of instability will be
further east over portions of the Northland, a bit further east
than yesterday's corresponding model runs. There's still some
uncertainty regarding the exact spatial displacement of the
instability, but the general consensus is for MLCAPE values to
range from 300 j/kg up to 1500 j/kg by 21z today, much more
favorable for strong to severe storms compared to yesterday. Deep
layer shear remains fairly low, with values ranging from 20 to 30
kts over the area. Given this more favorable set up for severe
convection, the Storm Prediction Center has expanded their day 1
convective outlook to include areas south of a Nisswa to Duluth to
Bayfield line in a marginal risk of severe weather. Due to the
lack of deep shear, the most likely threats will be large hail and
damaging winds to go along with the larger threat of heavy
rainfall and localized flooding. The slight risk of severe weather
stops just barely into southeastern Price County.

Temperatures today will likely be cooler than they were
yesterday, due to the abundance of cloud cover and precipitation
expected, along with a northeasterly wind component off Lake
Superior. Highs today will range from the lower to mid 60s along
Lake Superior, and into the upper 60s and lower 70s further
inland.

The system will depart the Northland late tonight. Some lingering
mid- to upper-level energy will continue to support some chances
of showers over portions of our northeastern forecast area. The
departure of the system will bring a cooler airmass over the
region, which will also help to scour out the better moisture, as
evidenced by decreased Theta-E values. The better instability will
also decrease as the system departs to the east.

Long term...(thursday night through tuesday)
issued at 345 am CDT Wed Jun 28 2017

The atmosphere will be unstable into the weekend with showers and
a few thunderstorms possible through Sunday morning as a series
of shortwaves affect the region. There will be some lingering
showers across areas mainly north of the Iron Range and The
Arrowhead Thursday morning before moving off to the east by
midday. The next round of precipitation will develop late Thursday
night and continue into early Saturday evening as a series of
shortwaves move through central Minnesota and WI. The threat for
precipitation will finally end by Sunday afternoon as an area of
high pressure builds into the upper Midwest. It will stay dry
through Wednesday night when another shortwave brings a chance for
showers to the region.

Temperatures will stay at or a little below normal through the
weekend but will increase to the 75-85 range with higher humidity
at the beginning of next week. July 4th looks to be rain-free at
the moment.

&&

Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1236 PM CDT Wed Jun 28 2017

Widespread rain will be over the region with MVFR to IFR
ceilings. This scenario will last through much of the forecast
period. However, some thunderstorms could occur in southern
areas, from kbrd to khyr through 02z. Overnight expect mainly IFR
conditions, but by 14z tomorrow ceilings will gradually rise.
East to southeast winds this afternoon will switch to northwest as
a cold front moves through this evening.

&&

Preliminary point temps/pops...
dlh 62 54 71 53 / 90 60 20 30
inl 68 54 71 54 / 90 80 30 30
brd 72 57 77 57 / 100 20 20 40
hyr 71 57 74 55 / 90 70 10 40
asx 70 53 72 53 / 80 70 20 30

&&

Dlh watches/warnings/advisories...
WI...beach hazards statement until 8 PM CDT this evening for wiz001.

Minnesota...beach hazards statement until 8 PM CDT this evening for mnz037.

Ls...Small Craft Advisory until 10 PM CDT this evening for lsz140>145.

&&

$$

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