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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
612 am CDT Tuesday Sep 23 2014

Update...
issued at 602 am CDT Tuesday Sep 23 2014

Updated to include 12z aviation discussion below.

&&

Short term...(today and tonight)
issued at 322 am CDT Tuesday Sep 23 2014

Today-tonight...surface analysis shows an area of high pressure centered
over the central Ohio Valley region with its western extent still
covering the upper miss River Valley this morning. Aloft...an upper level
ridge is centered just about over Minnesota...extending southward over IA/MO. With
this ridge slowly moving eastward over Minnesota into WI and the surface high pressure
allowing for decent radiational cooling conds over eastern portions of
the weather forecast office mpx County warning forecast area with clear skies and nearly calm winds...the
coolest readings will be felt over western WI this morning. In
addition...patchy fog is also being seen this morning whereas the Minnesota
portion of the County warning forecast area with warmer temperatures and a more S-southeast component of
winds around 5 miles per hour will remain free from fog development. Any fog
will gradually burn off shortly after daybreak...then attention
turns to a compact rotating upper level low making its way eastward over
the northern plains. With a deep southerly fetch ahead of this upper low
bringing in higher levels of moisture to be wrapped into this
system...enhanced Omega lift ahead of the low will be responsible
for creating isolated to scattered showers over western and southern portions of the
County warning forecast area by midday today. Though clouds will certainly be on the increases
from the SW...the lack of a surface low or front along with drier
lower levels will make low level lift and moisture convergence a
mitigating factor to better precipitation coverage and quantitative precipitation forecast amounts...but
with better model agreement on at least -shra over southwestern portions
of the County warning forecast area today and even through tonight...have maintained slight-low chance
probability of precipitation for those portions of the County warning forecast area. Since the upper level low is
expeceted to run into the drier upper ridge...open up to a trough and lift
north...precipitation is not expeceted to make much more progress eastward than
central Minnesota through tonight so have been able to leave much of eastern Minnesota
into western WI dry through this part of the forecast period. Even the Twin
Cities /and the I-35 corridor as a whole/ may have a tough time
receiving precipitation through this short-term period but cannot be ruled
out completely so some slight chance probability of precipitation are included along and west of
Interstate 35. As for temperatures...after quite the spread in low
temperatures this morning...ranging from the lower 40s in western WI to the lower
50s in western Minnesota...temperatures will even out for highs this afternoon into the
lower 70s underneath an expected decent coverage of clouds...albeit
middle-to-high level. Modest warm air advection tonight with deep S-SW
flow at the surface and aloft along with the blanket of cloud cover
will spell much warmer temperatures for overnight Tuesday into Wednesday. Lows Wednesday
morning will range around 50 in western WI to near 60 in western Minnesota.

Long term...(wednesday through monday)
issued at 322 am CDT Tuesday Sep 23 2014

Main forecast issues of note were the continued probability of precipitation through
Wednesday night...which resulted in cooler temperatures on
Wednesday. Also...increased temperatures later in the weak above guidance
based on the mass fields.

At the start of the period light rain showers should be ongoing
across the western half of the forecast area. Hires models depict
this...and forecast soundings off the NAM/GFS show deeper
moisture...stronger vertical motion...and therefore generate more
precipitation. Middle level clouds will limit the afternoon heating...so
decreased temperatures on Wednesday...especially in western WI.

An upper level ridge will build across the High Plains as this
system gets sheared apart in the northern stream. A thermal ridge
will build to the west...and by Friday afternoon h850 temperatures will
be on the order of 17-19c along the Minnesota/Dakota border.
Forecast soundings show clear skies...and although the surface
winds initially start out southeast...afternoon mixing gradually
transfers southwesterly winds throughout the boundary layer which
will be a favorable setup for warm temperatures...especially along
the Minnesota River Valley. This setup has the potential to bring
middle and even upper 80s across western Minnesota by the end of the
week...so raised temperatures above the model consensus.

&&

Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 602 am CDT Tuesday Sep 23 2014

Aside from patchy IFR fog in/near Keau this morning...all sites to
start out as VFR. High clouds slowly stream in from the SW in
advance of an upper level low rotating over the Dakotas. -Shra will
gradually spread into southwestern Minnesota later today then over more of western and
southern Minnesota tonight. However...krwf looks to have the best shot at some
precipitation then possibly kaxn tonight. Otherwise...the slowing
progression of the upper low will confine precipitation returns to southern/western
Minnesota...leaving the remainder of the taf sites dry. In addition...no
flight conditions reductions are expeceted for the sites that receive precipitation
due to drier lower levels and southerly winds in the 8-15 knots range for
much of the day into tonight.

Kmsp...VFR conds throughout with gradually increasing high cloud
coverage that will slowly lower through tmrw morning. Precipitation chances are
quite low so have opted to run with a dry taf...but if anything...
isolated showers may be possible after 10z-12z tmrw. And if so...no
flight condition reduction is expeceted.

/Outlook for kmsp/
Wednesday...VFR. MVFR ceilings possible overnight. Winds south-southeast 12-15g25 kts.
Thursday...VFR. Winds S 7-10 kts.
Friday...VFR. Winds south-southeast 5-10 kts.

&&

Mpx watches/warnings/advisories...
Minnesota...none.
WI...none.
&&

$$

Update...jpc
short term...jpc
long term...jrb
aviation...jpc

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