Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 171140

Area Forecast Discussion
National Weather Service La Crosse WI
640 AM CDT Mon Oct 17 2016

.SHORT TERM...(Today and tonight)
Issued at 315 AM CDT Mon Oct 17 2016

At 3 AM, a warm front was located near the Interstate 94 corridor.
Temperatures north of this front are currently in the lower to mid
60s which are 25 to 30 degrees above our normal low temperature.
Meanwhile south of the warm front, temperatures are around 70
degrees. This is 30 to 35 degrees warmer than our normal low
temperature. If these temperatures stay above the lower and mid
60s through 1 AM Tuesday (the end of the calendar day in CST) than
some record warm minimum temperatures could be established for
this day.  More on this can be found in the climate section.

The temperatures are not the only thing exceptional about this
air mass early this morning. North of this warm front surface dew
points are in the mid to upper 50s. Meanwhile south of this warm
front, the surface dew points are in the mid and upper 60s. Dew
points this high are extremely rare for this time of year. La
Crosse has only seen 3 days this late in the year where the dew
points were higher than they were this morning. More on this can
be found below in the climate section.

The 17.00z models continue to show that low clouds will develop
and move northward into the area toward day break and then linger
through the day. This may limit our maximum temperature some.
However at this time, these clouds have not materialize across
northern Missouri as of yet. This is concerning because if these
cloud do not develop, the maximum temperature forecast will
likely be too low and this will make it more likely that surface
convection could develop along and north of Interstate 90 this
afternoon. For this to occur, the temperatures would have to be
near 80 degrees. With more than ample shear, right-moving
supercell thunderstorms could potentially develop along the warm
front. This opens the door for the potential of tornadoes along
with damaging winds and hail. If surface convection does not
develop, there will still be potential for elevated right-moving
or splitting supercells along and north of the warm front. The
main threat with these storms would be large hail and to a lesser
extent damaging winds. The severe weather potential is highly
dependent upon there being enough instability to balance out the
very strong shear located over the area. If severe weather happens
to develop, it would likely occur between 4 PM and 8 PM.

.LONG TERM...(Tuesday through Sunday)
Issued at 315 AM CDT Mon Oct 17 2016

This period looks mainly dry with more seasonable temperatures
returning to the area from Thursday into early next week. However
there are hints in the GFS and ECMWF that the temperatures for
this time period may be too cool.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 640 AM CDT Mon Oct 17 2016

A tricky forecast over the next 24 hours, revolving around how
stratus will behave, especially through the afternoon today. After
a break earlier, finally starting to see lower stratus fill back
in the past few hours, along with some fog which may impact RST
through mid morning, though very much unsure how low visibility
will go there with clouds now filling back in (much lower
visibility just to the west). In all likelihood, we should see a
period of MVFR to perhaps briefly IFR ceilings through mid
afternoon or so, before a northward-advancing warm front perhaps
tries to clear out the lower stuff, but also brings a small risk
for a few showers and storms around LSE/RST. A cold front will
then follow through late evening and early overnight, shifting
winds back northwest and perhaps bringing back a period of MVFR
ceilings with cooler air arriving behind the boundary.


Issued at 315 AM CDT Mon Oct 17 2016

As of 3 AM, La Crosse WI had a surface dew point of 66 degrees.
Only 3 days have had a dew point higher than this so late in the
year. They were October 17 1965, October 20 1979, and October 29
2004. On all three of these dates, the dew point maxed out at 67
degrees. Dew point records for La Crosse date back to 1934.

The temperatures early this morning are 20 to 35 degrees above
normal. In fact, there is a chance that both Rochester and La
Crosse will set new record warm low temperature readings for
October 17th. Below is a look at those records as they stand

           Record Warmest Low   Year Established   Forecast Low
           ------------------   ----------------   ------------

La Crosse           64                 1994             65
Rochester           62                 1953             64

In order for these to be records, the temperatures must stay
above these values through 1 AM Tuesday morning (the official end
of the calendar day).




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