Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 160748
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
248 AM CDT Sat Mar 16 2024

.KEY MESSAGES...

- With northwest winds gusting into the 25 to 35 mph and minimum
  relative humidities dropping into the 25 to 35 percent range,
  there will be the potential for near-critical fire weather
  conditions along and south of Interstate 94 this afternoon.

- Cooler than normal temperatures are expected for Sunday and
  Monday. High temperatures on both days will be mainly in the
  30s on both days. Wind chills on Sunday morning will be in the
  single digits and teens on Sunday morning and in the single
  digits above zero on Monday morning.

- Near-normal temperatures are expected from Tuesday into
  Friday.

&&

.DISCUSSION...
Issued at 247 AM CDT Sat Mar 16 2024

Today through Monday...

A cold front will be exiting the area close to sunrise this
morning. Cold air advection continues through much of the
weekend. 850 mb temperatures start out this morning around 0 to
6C and they drop into -12 to -14C by Sunday morning. There
continues to be much uncertainty in the cloud cover for this
afternoon. With 850 mb relative humidities of greater than
80 percent and cyclonic flow aloft in the NAM, it would keep us
mainly cloudy during daytime each day. Meanwhile, the GFS and
RAP lowers the 850 mb moisture during the afternoon. This would
result in deeper mixing (possibly up to 750 mb) and lower
relative humidities. Based on the clouds upstream, leaning more
toward mainly clouds for today. This would result in our high
temperatures in the lower to mid-40s north of Interstate 90 and
range from the mid-40s to lower 50s elsewhere. The 16.00z HREF
is not that impressive with its 2-meter relative humidities
falling below 30 percent. They are only showing up to 20 percent
chance that this will occur across southeast Minnesota and
northeast Iowa. For dew points today and Sunday, did a 50-50
blend of the NBM and NBM 10th percentile, so that I could lean
toward the potential for a drier scenario, but not go completely
that way. The 16.00z HREF probabilities of winds gusts greater
than 35 mph are generally less than 20 percent. This will likely
result in the potential that we could approach critical fire
weather conditions this afternoon, so planning on issuing a
Special Weather Statement highlighting that dry fuels and winds
could result in favorable conditions for fires to spread this
afternoon.

Below normal temperatures continue to look likley for Sunday and
Monday. High temperatures will range from the upper 20s to
mid-30s on Sunday and in the 30s on Monday. Even though it will
be cool on St. Patrick`s Day, we were even colder last year.
La Crosse, WI had a high temperature of 28F and a low
temperature of 9F. It was the coldest high on St. Patrick`s Day
since 1993 (17F). Rochester, MN had a high temperature of 21F
and a low temperature of 4F. It was the coldest high on St.
Patrick`s Day since 1993 (11F). Wind chills will be in the
single digits and teens on Sunday morning and in the single
digits above zero on Monday morning.

Tuesday and Wednesday...

Another cold front will move southeast through the region during
the morning. Unlike this one, the coldest air will be located
more over Ontario, so high temperatures will be more seasonable
for Tuesday (lower 40s to lower 50s) and slightly cooler than
normal for Wednesday (mid-30s to upper 40s). Like the front
today, it looks like it will move through the region dry.

Late Next Week...

Still plenty of uncertainty on how the northern stream 500 mb
pattern sets up. Much of this difference is due to how fast the
ridge over Ontario and Quebec breaks down. This impacts both the
temperatures and precipitation. Due to this uncertainty, stayed
with the NBM`s temperatures and precipitation chances.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 950 PM CDT Fri Mar 15 2024

VFR conditions are forecast through the TAF period with a
period of gusty WSW winds overnight tonight becoming NW on
Saturday, gusting 25 to 30 kts. Mid-level clouds will increase
overnight tonight with lower 3.5-5kft VFR clouds moving in
during the morning on Saturday. A period of low level wind shear
is possible for a several hour window overnight tonight as
winds aloft increase, but with some mixing/gust likely there is
not specific mention of LLWS in the TAFs.

&&

.FIRE WEATHER...This Afternoon
Issued at 247 AM CDT Sat Mar 16 2024

With northwest winds gusting into the 25 to 35 mph and minimum
relative humidities dropping into the 25 to 35 percent range
south of Interstate 90, there will be the potential for near-
critical fire weather conditions along and south of Interstate
94 this afternoon. One limiting factor will be cloud cover. If
it stays cloudy longer this afternoon, this would limit mixing
which would lower wind gusts and temperatures. In addition, the
cooler temperatures would limit the drop in relative humidity
values this afternoon. The 16.00z HREF is not that impressive
with its 2-meter relative humidities falling below 30 percent.
They are only showing up to 20 percent chance that this will
occur across southeast Minnesota and northeast Iowa. This
will likely result in the potential that we could approach
critical fire weather conditions this afternoon, so planning on
issuing a Special Weather Statement highlighting that dry fuels
and winds could result in favorable conditions for fires to
spread this afternoon.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.

&&

$$

DISCUSSION...Boyne
AVIATION...KAA
FIRE WEATHER...Boyne


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