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Area forecast discussion 
National Weather Service La Crosse WI
1216 PM 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 18z tafs through 18z Wednesday afternoon)
issued at 1216 PM CDT Tuesday Jul 22 2014

Drier air and northwest winds were spreading southeast across the
area at middle day...with winds becoming northwest in the 10kg g15-20kt
range. Dew points were dropping from the low-middle 70s to the middle 60s.
However a band of 2k-3k feet strato-cumulus was located across northwest WI
to southwest Minnesota...behind the cold front bringing in the drier air.
This band of clouds thinning the past couple hours but still appears
there will be some bkn025 ceilings at krst through 20z. With continued
thinning appears lower clouds at klse will remain scattered as the band
moves across in the 19-21z period.

Good VFR conditions and decreasing northwest to north winds then
expected for later this afternoon through tonight and for Wednesday as drier
Canadian high pressure builds into the upper Midwest. Light north
winds tonight should keep any radiational valley br/fog in the 09-13z
time-frame to a minimum and left this out of the klse taf.


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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