Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 241740
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1240 PM CDT TUE MAY 24 2016

.SHORT TERM...(Today through Thursday)
Issued at 257 AM CDT Tue May 24 2016

Water vapor satellite early this morning indicates a couple of
short wave troughs are over the Dakotas and eastern Nebraska.
These waves will move to the northeast and past the area early
this morning with rising upper level heights expected for much of
the day. The hi-res models indicate the showers and storms over
western Iowa ahead of the Nebraska wave will continue to move
northeast and then start to rapidly weaken once they move past
Interstate 35 and begin to move into some drier air. Dew points
are currently in the lower 60s where this activity is occurring
and then drop into the lower to middle 50s across eastern Iowa so
the weakening trend in the hi-res models makes sense. With the
rising heights for the remainder of the day, there doesn`t really
look to be much of trigger to cause additional activity to form
and the hi-res models only show the possibility of some widely
scattered activity during the afternoon.

Heights will start to lower again tonight as the next short wave
trough comes out of the Rockies and moves across the Dakotas.
Decent agreement between the models that a convective complex
should form over the Dakotas ahead of this wave tonight and move
northeast into Minnesota. Not as good agreement between the models
as to whether a second complex will form farther south over
Kansas on the nose of the low level jet. The 24.00Z NAM and GFS
both seem to support this idea and generate a MCV that then moves
northeast toward the area late tonight and across the area
Wednesday. As this wave is coming across, the low level jet should
start to strengthen again during the afternoon with the nose of
this possibly right over the forecast area. However, at this
point, there is little support from the hi-res models of the
activity making into the area late tonight into Wednesday or
redeveloping over the area. Confidence that the broad scale models
have the right idea with these convective complexes is not very
high but will try to maintain some continuity with the previous
forecasts. Will continue to have up to a 60 percent chance of rain
late tonight that spreads across the entire area Wednesday.

If this activity can generate over the area Wednesday, it should
progress off the east/northeast Wednesday night with a general
drying trend across the western sections. Thursday morning looks
like there should be a lull in the activity before the forcing may
start to increase again during the afternoon. All the models show
an upper level low over North Dakota that becomes an open wave
during the afternoon. The NAM suggest a rather strong short wave
trough could be rotating around this upper level low while the GFS
and 24.00Z ECMWF really don`t show this wave at all. Even without
this short wave trough, the GFS does indicate some moisture
transport back into the area with some lift spreading over the
area from the upper level low. For now, will bump the rain chances
up into the 30 to 40 percent range for the afternoon.

The potential for severe storms looks rather limited through
Thursday. The limiting factor for today and Wednesday looks to be
an overall lack of decent shear. The potential on Thursday then
depends on which model has the correct solution. Looking at
forecast soundings for KRST Thursday afternoon, the NAM indicates
around 3500 J/Kg of CAPE will be in place with around 50 knots of
shear while the GFS shows a mid level cap with 1300 J/Kg of CAPE
above the cap but only 15 to 20 knots of shear.

.LONG TERM...(Thursday night through Monday)
Issued at 257 AM CDT Tue May 24 2016

The southwest flow aloft looks to continue into the Memorial Day
holiday weekend. Right now, there is good model agreement of an
upper level low lifting out of the desert southwest and across the
upper Missouri River valley for the beginning of the weekend. With
the southwest flow and the potential for embedded short wave
troughs, will have persistent rain chances in the forecast with
the highest threat looking to be Friday as the upper level low
approaches the region. These rain chances will then decrease with
the passage of the upper level low with only a small 20 to 30
percent chance on Memorial Day.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1240 PM CDT Tue May 24 2016

Pretty quiet at the moment with VFR cumulus/mid-cloud cover
behind a weak departing mid-level trough. Looks to remain
quiet/VFR through much of tonight. Will be watching a stronger
trough eject northeast toward the area toward morning which is
likely to draw scattered shra/ts into the vicinity of KRST by 11z
and KLSE around 14z. Scattered shra/ts to remain in the vicinity
through 18z...but expected to remain VFR.

&&

.ARX Watches/Warnings/Advisories...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...04
LONG TERM...04
AVIATION...DAS


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