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Area forecast discussion 
National Weather Service La Crosse WI
1120 am CDT Wednesday may 6 2015

Short term...(today and tonight)
issued at 300 am CDT Wednesday may 6 2015

Complex weather pattern will lead to plenty of clouds and some
chance for showers and embedded thunderstorms today into tonight
for some areas. Closed circulation ejecting out of the mean trough
along the West Coast of the Continental U.S....spinning over Colorado
overnight. Frontogenetic forcing on the leading edge of the
warm/moist advection leading to showers from central Minnesota across
primarily the northern half of WI. Meanwhile...stronger dynamic
forcing nearer the main low center leading to convective
development from Kansas/MO up into Iowa. Main circulation and forcing
will move north into the Dakotas tonight. Continued moisture
transport into our area suggests that some showers and isolated
thunderstorms could develop and affect portions of southeast Minnesota
and northeast Iowa later today and tonight. However it does appear
the better support will remain further west. Have been maintaining
rain chance gradient diminishing further east for a few days now
and will keep the general trend through Thursday morning.

Despite plenty of clouds and some rain...warm advection and any
random peek at the sun will help temperatures make it up into the
70s. And a few localized 80 degree readings are not out of the
question.

Long term...(thursday through tuesday)
issued at 300 am CDT Wednesday may 6 2015

Very unsettled pattern will make the timing details of the
forecast challenging for the next week to 10 days. Dakotas wave
continues north into Canada...with secondary short wave trough
helping to kick the trailing surface cold front through the area
Thursday night into Friday. Gulf will be wide open at this point
so moisture return and instability should drive some convection
through the region with rain likely during this timeframe...
supported by all models. Still some uncertainty on just how far
and how fast the front moves south of the area on Friday. GFS most
robust with the surge of cooler/drier air. European model (ecmwf) trending that way
too leading to a bit higher confidence than yesterday at this
time. Opted to favor the GFS for this period due to the trend.

Main long wave trough finally looking to fully eject out of the
Desert Southwest over the weekend...taking its time tracking into
the upper Midwest by late Mon/Tue. Models in surprisingly good
agreement with placement and timing of features as this takes
place. Main surface low deepens along the Lee of The Rockies by
Sunday morning. If this timing holds...Sunday afternoon/evening
could be interesting with several parameters falling into place
for a severe weather outbreak from the plains up toward Iowa. Late
Sunday into Monday looks pretty wet under this scenario as the
system slowly traverses the tri-state region.

&&

Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1120 am CDT Wednesday may 6 2015

Ceilings...
low clouds should continue to lift this afternoon as mixing kicks
in. Anticipating some lowering for a few hours as a warm front
shifts across the area tonight...and again as another area of precipitation
moves in from the west Thursday morning. At this time though...ceilings are
trending toward the VFR category.

Vsby/wx...
warm front and weak instability should be enough to fire
a line of -shra late this afternoon into the evening. See some ts
threat...mostly krst where instability and timing favor the
potential. Will add thunderstorms in the vicinity for now. Confidence a bit lower at klse and
will leave out of the forecast. Trends will be monitored and
adjustments made to forecast as necessary.

Expect short-term reductions with any stronger shower/storm...but
timing on any dip into MVFR/IFR is uncertain...and likely less than
1 hour. Perhaps some overnight br MVFR visibilities due to saturated near
surface layer.

Winds...
mixing will promote afternoon gustiness...with pressure
gradient then tightening for Thursday morning. Sustained around 20 kts is
likely Thursday morning...with gusts around 30 for krst.

Low level wind shear could become a concern overnight tonight with rap/hrrr/nam12
BUFKIT soundings suggesting 45 kts from the south by 2 kft.
Straddling criteria and will opt to leave out of the forecast for
the moment.

&&

Arx watches/warnings/advisories...
WI...none.
Minnesota...none.
Iowa...none.

&&

$$

Short term...mw
long term...mw
aviation...rieck

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