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Area forecast discussion 
National Weather Service La Crosse WI
600 am CDT Tuesday Jul 22 2014

Short term...(today through thursday)
issued at 253 am CDT Tuesday Jul 22 2014

Organized line of convection working east across Minnesota and
northern Wisconsin this morning. Local and regional radars
showing some echoes developing south of the line on the edge of
the moisture transport axis. Looking at the mesoscale scale models this
morning...the hrrr and rap are pretty much useless as they turn
the system more northeast and dissipate it way too quickly. The
22.00z hi-res arw and nmm look much more reasonable with the
convective complex and continue moving it east taking it just
north of the forecast area. Looking at the 22.00z NAM BUFKIT
sounding for Ladysmith...this makes sense as the cap holds in
place through the remainder of the night. As for the developing
echoes over the forecast area...these are just starting to get
some sprinkles to the ground. The hi-res nmm shows the echoes
continuing through the night until the moisture transport starts
to Bend more off to the east but does not really show them
expanding and keeps them scattered. With the main convective
complex expected to move by to the north...have lowered the rain
chances across the north down to about 40 percent for this
morning. To handle the light echoes...will show about a 20 percent
as far south as i90 unless observations start indicating that this
activity is reaching the ground.

For the remainder of today...the main short wave trough will pass
across Lake Superior into Ontario. A secondary short wave trough
will drop across the region during the afternoon as the flow
becomes northwest aloft. It appears that this secondary short wave
trough will only produce some weak pv advection in the 500-300 mb
layer as it moves across. However...the forcing from this wave
does not look like it will be able to interact with the front
until it has moved past the area. The NAM BUFKIT sounding for
Blue River indicates the cap will hold in place until late this
afternoon while the 22.00z GFS holds it into the evening. With the
cap remaining in place...all the models suggest further
development along the front does not take place until this evening
and south of the forecast area. Just in case the NAM is correct
and the cap dissipates a little sooner...have opted to hold onto a
20 to 30 percent rain chance across the southeast sections for the
late afternoon into the early evening.

Looks like temperatures will have a good opportunity to warm this
afternoon ahead of the front. High temperatures in the upper 80s
to lower 90s over the southeast half of the area are a pretty good
bet. Dew points are expected to again get into the middle 70s
ahead of the front...which will push the heat index in the
advisory range across the southern sections and will be issuing a
heat advisory to handle this.

The rest of the period looks to be quiet with cooler and drier
conditions as a large area of high pressure moves across the
region from Canada toward the Ohio River valley.

Long term...(thursday night through monday)
issued at 253 am CDT Tuesday Jul 22 2014

Some differences between the models on how fast the next system
moves into the region. The upper level ridge that builds over the
western part of the country over the first half of the week...gets
flattened as an upper level low moves onshore from the Pacific and
across southern Canada. The differences in the models comes from
how fast short wave troughs will Cut Through the flow between the
upper level low and the ridge. It looks like the 22.00z European model (ecmwf)
continues to be faster than the GFS and 22.00z Gem on bringing the
first short wave through. However...all of them show the same
general pattern with the wave and a surface low tracking from the
Dakotas southeast toward the Ohio River valley. With the GFS and
Gem being a little slower...will indicate the highest rain chances
Friday into Friday night. The next short wave trough and surface
low still look to come through over the weekend and track farther
northeast than the Friday system. This system will bring some rain
chances to the entire area for Sunday with the better chances over
central Wisconsin.


Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 600 am CDT Tuesday Jul 22 2014

Immediate concerns for early this morning is the potential for a few
hour period of MVFR cigs/vsbys. Satellite imagery and surface observation
indicating a drop in visibilities in a clear slot ahead of an approaching
cold front. Some stratus also starting to develop-extend into this
region. Both could impact krst/klse...with a higher likelihood at
krst. BUFKIT soundings would suggest that any ceiling that did move in
would quickly mix out between 14-16z. Will add ceiling mention into a
tempo group for krst for now...and leave out at klse were confidence
is a bit less. Some fuzz will linger at krst until middle morning. VFR
conditions should then be the rule into tonight.

For Wednesday morning...some suggestions in the NAM klse sounding of
valley fog potential. Decoupling will result in a light wind this
evening...but direction could be northwest. If so...locale research
suggests dense fog is not likely. Also...winds just off the ground
are expected to be 10+ kts. Also not favorable. So...will leave any
mention out of the forecast for now...but potential should be


Arx watches/warnings/advisories...
WI...heat advisory from noon today to 7 PM CDT this evening for

Iowa...heat advisory from noon today to 7 PM CDT this evening for


Short term...04
long term....04

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