Area Forecast Discussion
Issued by NWS La Crosse, WI

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980
FXUS63 KARX 200411
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1110 PM CDT Fri May 19 2017

.SHORT TERM...(This evening through Saturday)
Issued at 314 PM CDT Fri May 19 2017

For late this afternoon and early evening, the 700 to 500 mb
frontogenesis will gradually weaken across the area. In addition,
there will be some drying below 750 mb. As this occurs, the
showers will gradually dissipate.

From late tonight into Saturday morning, the 925 and 850 mb
moisture transport will increase as a low pressure system moves
east across Iowa. The greatest surface-based CAPES will remain to
our southeast across southeast Iowa and Illinois. However with
elevated CAPES climbing up to 500 mb and the dry slot moving in
kept the threat for isolated storms in the forecast.

With precipitable water values of around 1 inch, the showers and
storms will be efficient rainfall makers on Saturday. Additional
rainfall amounts will be around an inch for northeast Iowa and
southwest Wisconsin and from a half to 1 inch for the remainder of
the area. These rains will result in further rises on area rivers
and streams.

.LONG TERM...(Saturday night through Friday)
Issued at 314 PM CDT Fri May 19 2017

On Saturday night, the upper level low will transition northeast
from the central Plains into northern Wisconsin. As this occurs,
the threat for showers will gradually shift north of Interstate 90
and remain there through Sunday night. Additional rainfall amounts
look light.

From Monday afternoon through Tuesday, a shortwave trough will
round the upper level low and move through the Mid and Upper
Mississippi River Valley. This system will result in another round
of showers. With surface-based CAPES climbing to 1000 to
1500 J/kg on Monday and up to 500 J/kg Tuesday afternoon, this
will result in the development of isolated thunderstorms. With
850 mb temperatures of around 3C and extensive cloud cover, the
high temperatures on Tuesday will remain in 50s.

Some weak ridging will then develop across the region for the
mid-week. This will provide a couple of dry with high temperatures
in the 60s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1110 PM CDT Fri May 19 2017

Cigs: clouds will continue to thicken/lower overnight as an upper
level trough/sfc low approaches from the southwest. Expecting a drop
into mvfr/ifr between 12-15z...likely holding there through Sat
night and the better part of Sunday.

WX/Vsby: showers move back into the area around 12z Sat, with the
bulk lifting north of the taf sites by 21z. Could see some
convection develop along the system`s cold front/dry slot by late
afternoon/early evening. Maybe some thunder chances with this,
otherwise the thunder threat looks minimal. There will be vsby
restrictions with the rain, generally mvfr but a period of ifr
possible (more likely krst).

Winds: easterly in direction with some increase toward 12z Sat as
the sfc low approaches - and then a decrease in speeds as the low
moves through. Some hints of LLWS potential overnight/early Sat
morning - moreso for KLSE. Not confident enough to include at this
time.

&&

.HYDROLOGY...
Issued at 314 PM CDT Fri May 19 2017

River Flood Warnings continue along the Trempealeau River at
Arcadia and Dodge, the Black River at Black River Falls and
Galesville, and the Yellow River at Necedah as runoff from the
very heavy rain continues to move through the river system.

Another round of rain and isolated storms will move through the
area late tonight and Saturday. Additional rainfall amounts will
be around an inch for northeast Iowa and southwest Wisconsin and
from a half to 1 inch for the remainder of the area. These rains
will result in further rises on area rivers and streams.

&&

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

$$

SHORT TERM...Boyne
LONG TERM...Boyne
AVIATION...Rieck
HYDROLOGY...Boyne



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