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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
115 PM CDT Wednesday Apr 1 2015

Update for 18z aviation discussion below...

&&

Short term...(today and tonight)
issued at 422 am CDT Wednesday Apr 1 2015

Warmest temperatures of the year...followed by afternoon
thunderstorms and the potential for the first severe weather this
season continues to be on track for today.

Increased afternoon highs for today...and would not be surprised to
80f across southern Minnesota given the warm air advection...deep
mixing...and diurnal heating. Forecast soundings show 40kt gust
potential with the south southwesterly winds ahead of the cold
front...so continued with a Wind Advisory across the southern half
of the forecast area.

As alluded to in previous discussions...the source of the boundary
layer moisture is moisture advection in the h900-800mb layer. This
will take place along the NE/Iowa border...up through Redwood Falls.
Boundary layer mixing will bring this moisture down to the surface
causing dewpoints to rise. However...farther east in central/eastern
Minnesota...boundary layer mixing will fail to increase surface moisture
until late afternoon...so a red flag warning has been issued for
this area given the dry fuels...low relative humidity...and strong winds.

Convection certainly looks likely this afternoon...after 4pm...as
the hires models depict a line of storms from eastern NE up through
northwest WI. Given the instability and shear...severe weather is a
real possibility...and the slight risk has been shifted slightly
northward for this afternoon. The main threat is hail/wind
initially...followed by mainly wind 1-2hrs after initiation. The GFS
continues to be the fastest model in comparison to the other
deterministic models with the timing of the cold front. For probability of precipitation
trended toward a slightly slower/westward solution...but advanced
the precipitation faster in anticipation that cold pool development should
propagate the line faster then the cold front...so have precipitation
exiting the region by 09z tonight.

Long term...(thursday through tuesday)
issued at 422 am CDT Wednesday Apr 1 2015

Strong cold air advection and very deep mixing will make for another windy day
Thursday. Soundings show mixing up to 700 mb with unidirectional
flow. GFS is most bullish with the wind reaching solidly advisory
criteria...the others are a tad more reserved. Nonetheless...could
see gusts exceed 40 knots and may need a Wind Advisory for parts of
the area...particularly central Minnesota and northwest WI. Relative humidity will
plummet into the teens by afternoon and will set up another
critical fire weather day. Consult the fire weather section below for
more information on that threat.

Wind will ease quickly Thursday evening and high pressure will
build in Friday/. A fast moving weak clipper will slide southeast
across the northern plains and upper MS valley Friday night and
could bring a bit of light snow to northern MN/WI. Most of it will
remain north of the County Warning Area...but did introduce a slight chance
bordering weather forecast office dlh.

Models diverge from Sunday Onward with the European model (ecmwf) on the slower
side and the GFS on the faster side of the guidance consensus. GFS
has also shifted north with the system for next week whereas the
European model (ecmwf) has shifted south. There is too much uncertainty to get into
any specifics yet...but chances for precipitation increase during this
period and it looks like mainly rain.

&&

Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1248 PM CDT Wednesday Apr 1 2015

Currently in the warm sector of a strong surface low in the
Dakotas. Main concern in the imediate future is the very stong
winds...gusts over 40mph will continue this afternoon for much of
the area. Later this afternoon and especially this
evening...trailing cold front will push through and set off a line
of showers with embedded thunder. Current expectations are that
this line will develop near a line from rwf to stc and progress
east through the evening. Expcting mostly VFR but visible could drop
temporarily under thunderstorm activity. Some visible restirction has
been seen at rwf due to the dirt/dust being kicked up by the
excessive winds. That could persist through the afternoon.

Kmsp...best chance of precipitation looks to be 2-4z at this time.
Thunder is still a possibility but do not expect severe storms
this far north.

/Outlook for kmsp/
Friday...VFR. Winds northwest 10-15 kts.
Sat...VFR. Winds west 10-15 kts.
Sun...VFR. Winds east around 10 kts.

&&

Fire weather...
issued at 422 am CDT Wednesday Apr 1 2015

Strong southerly winds from 25 to 35 miles per hour will develop this
morning across the red flag warning area and persist through the
afternoon while humidity levels drop to around 25 percent. If
winds are stronger than currently forecast further north...a few
counties may need to be added to the warning.

A Fire Weather Watch has been issued for Thursday from southwest
to northeast Minnesota. Strong west winds from 25 to 35 miles per hour will
develop during the morning and persist through late afternoon. In
addition...humidities will drop into the 15 to 20 percent range
setting up another day with critical fire weather conditions. The
watch is in effect west of the area expected to get hit most by
thunderstorms this evening...as there is potential for wetter
fuels there.

&&

Mpx watches/warnings/advisories...
Minnesota...red flag warning until 7 PM CDT this evening for mnz064-073>078-
082>085-091>093.

Wind Advisory until 5 PM CDT this afternoon for mnz054>059-
064>069-073>077-082>085-091>093.

Fire Weather Watch from Thursday morning through Thursday
evening for mnz042>045-048>062-064>068-073>075-082.

WI...none.
&&

$$

Short term...jrb
long term...borghoff
aviation...speed
fire weather...borghoff

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