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Area forecast discussion 
National Weather Service Duluth Minnesota
338 PM CDT Tuesday Sep 2 2014

Short term...(this evening through Wednesday afternoon)
issued at 338 PM CDT Tuesday Sep 2 2014

Main concerns in the short term remain focused around the potential
for thunderstorms this afternoon and evening...mainly across the northern
counties where a few could pulse up and become strong with small
hail...gusty winds and heavy downpours...and the next threat of
strong to possibly severe weather tomorrow afternoon and
evening...dealing with large hail...damaging winds...heavy rainfall
and even a few tornadoes.

Broad cyclonic flow aloft is present across much of the northern third of
the Continental U.S. And over S-central Canada. Numerous embedded short waves are
tracking eastward through the long wave pattern today and one currently
over southern Manitoba will combine with a nearly Colorado-located surface trough/cold
front as it moves into northern Minnesota to produce scattered showers and
thunderstorms across the region through tonight. Already seeing scattered
convection develop over NE Minnesota with roughly 500-1000 j/kg of mu
cape...a weakly sheared deep layer env and a modest amount of
moisture above the mixed layer. Will likely see convection develop
over the same area...NE Minnesota as additional convection is forming
upstream to the northwest and will track to the southeast through the evening
and possibly tap into leftover boundaries from storms downstream.
A few of these storms could develop further to the south...but the
bulk of the convection should remain to the north and mainly carry
a threat of brief heavy rain...small hail...gusty winds and
lightning.

Storms could hold together late this evening and into the overnight
hours...becoming elevated above the bl but an overall decrease in
coverage and intensity is expected after sunset. Could see some
clearing late tonight...with a few lingering showers into The
Arrowhead. Any clearing could lead to temperatures falling into the upper
40s and 50s.

During the day Wednesday a surface low will develop quickly over the eastern
rockies and Central Plains...and lift to the NE through the morning.
A warm front will extend to the east and lift northward on the nose of a
strong push of warm moist unstable air. As this warm front
develops...the low level and deep layer wind profile will become
favorable for supercells across central Minnesota as surface winds back along
and ahead of the front. Ml cape values will climb above 2000 j/kg
and convection should initiate in the middle to late
afternoon...north of a capping inversion expected to be in place
over southern Minnesota. Steep lapse rates...a strong push of moisture from
the south and favorable amount of instability and deep layer shear
will all contribute to the convection becoming strong to severe.
The greatest risk of severe weather appears to be south of Highway 2 in NE
Minnesota in the afternoon and into northwest WI during the early evening. Even
though wet bulb zero heights are fairly high...around 10k feet...the
potential for strong updrafts will allow for the threat of large
hail with these storms. The sheared wind profile will allow the
storms to mature very well...and also allow for the potential of a
few tornadoes...mainly early along the warm front in Minnesota. The other
threat of heavy rainfall is also heightened with a strong push of
deep layer moisture from the south making the potential for
localized flooding a concern. Could see a quick 1-2 inches in some
locations with isolated higher amts possible.

Stay alert for any watches or warnings that may be issued in the
afternoon and evening on Wednesday.

Long term...(wednesday night through tuesday)
issued at 338 PM CDT Tuesday Sep 2 2014

An active weather pattern will begin this period as an amplifying
middle level trough advects east and interacts with sf low and strong
moisture transport. MDT/strong model consensus that a surface low will make
its way from sodak towards southeast Manitoba Wednesday night. The associated
cold front will make its way into western Minnesota by early Thursday morning.
Ahead of this front a surface warm front will move into southern/ctrl Minnesota. The
GFS/ecm/Gem all have their moisture transport maxima aimed into the southeastern
County Warning Area Wednesday evening...then translating east of the County Warning Area by 12z Thursday.
Although the forecast thermal/moisture fields may certainly change..at
this time it appears as if there will be two main forcing areas and
concentration of quantitative precipitation forecast. The southern one will be thermodynamically
driven by the nocturnal low level jet while the northern one will be tied into
deeper synoptic scale ascent occurring with middle level trough and
convergence from surface low moving across northestern nodak after midnight
Wednesday. Surface cold front will push across the County Warning Area Thursday with
additional convection developing in unstable atmosphere. Some storms
may be severe based on latest forecast of 50/60kt deep layer shear and
sbcapes approx 1500/255 j/kg. 110/120kt upper jet axis will cross
the region late Thursday. As a result strong kinematics with this
system so we should see a period of gusty winds with frontal passage and for
at least 6 hours or longer behind the surface front. A period of quiet
weather should follow from Friday into Sunday as surface high builds
into the Northland. There is a low probability of a few showers skirting
the northern tier of Minnesota but will leave out for now. Temperatures drop below climatology
after frontal passage and through most of the weekend. Northwest middle level flow relaxes
by early next week with a return to warm advection and increasing
chance of precipitation.

&&

Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1242 PM CDT Tuesday Sep 2 2014

A weak disturbance may bring an area of rain shower/thunderstorm to the County Warning Area this
afternoon/early evening. Confidence low on timing and areal extent
of precipitation with this feature so am expecting a few amendments in
next few hours. Otherwise mainly a VFR forecast.



&&

Preliminary point temps/pops...
dlh 56 75 62 76 / 20 60 60 40
inl 49 75 56 72 / 30 30 40 50
brd 55 77 64 77 / 20 60 60 40
hyr 54 77 65 83 / 10 50 70 60
asx 56 78 63 81 / 20 50 60 50

&&

Dlh watches/warnings/advisories...
Minnesota...none.
WI...none.
Ls...none.
&&

$$

Short term...bjt
long term...Cannon
aviation...Cannon

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