Area Forecast Discussion
Issued by NWS La Crosse, WI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KARX 290831
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
331 AM CDT Thu Jun 29 2017

.SHORT TERM...Today and Tonight
Issued at 330 AM CDT Thu Jun 29 2017

At 3 AM, a cold front was located from western tip of Upper
Michigan through La Crosse WI and then southeast to Omaha
Nebraska. The 29.00z models are in general agreement that this
front will shift south into northeast Iowa and southwest
Wisconsin this morning. Meanwhile, the western portion of this
front over western Iowa will surge northward as a short wave
trough over western Nebraska moves east. This short wave trough
will then move east northeast across Iowa this afternoon. As this
occurs, the instability will increase south of Interstate 90.
This is most dramatic in the RAP which has the 0-1 km mean layer
CAPES climbing into the 1 to 3K J/kg range. Meanwhile the NAM
keeps it boundary further south. As a result it only has CAPES of
1 to 2K J/kg across Fayette and Clayton counties in northeast Iowa
and Grant County in southwest Wisconsin. The GFS is between these
2 solutions.

With the ARW, NMM, and HRRR close with their solutions, trended
the forecast toward them for this afternoon and evening. Showers
and storms will move into northeast Iowa between 29.20z and
29.22z. This precipitation will then move out of southwest
Wisconsin between 30.01z and 30.03z. While there is good agreement
across southwest Wisconsin and northeast Iowa, there is still
some uncertainty on how far north these showers and storms will
get. SPC has south of I-90 in a marginal risk for wind and hail.
This seems reasonable since the 0-3 km and 0-6 km shear are weak.

In addition to the hail and wind threat this afternoon and evening,
the precipitable water values climb into the 1.5 to 2 inch range
and warm cloud layer climb depths rise into the 3.5 to 4.5 km
range across northeast Iowa and southwest Wisconsin. This would
make the showers and storms very efficient rain producers.
Fortunately, the CAMs are in good agreement that this convective
system will be progressive, so it should not aggravate the
flooding situation taking place along the Turkey River.

For tonight, the models are agreement that a short wave trough
will move east through the Upper Mississippi River Valley. This
will keep a chance of showers and storms in the forecast.

.LONG TERM...Friday through Wednesday
Issued at 330 AM CDT Thu Jun 29 2017

From Friday into Saturday night, a series of short wave troughs
will move east through the region. While the 0-1 km CAPES climb
into the 750 to 1500 J/kg range, both the 0-3 km and 0-6 km shear
remain weak. As a result, not anticipating any severe weather.

From Sunday afternoon into Monday, a cold front will move slowly
south across the region. With a 40 to 45 knot mid-level jet
moving through the region on Sunday afternoon and evening, there
will be an increase in the 0-3 km and 0-6 km shear along and
north of Interstate 90. In addition, the 0-1 km CAPES will be in
the 1 to 2K J/km range. This may result in some strong to severe
storms.

From Monday night into Wednesday, the models differ on the
location of the cold front. The GFS is further north, so it has
showers and storms south of Interstate 90 as a low pressure system
moves along this front from the afternoon of Independence Day
into Tuesday night. Meanwhile the GEM and ECMWF are much further
south with this front and we remain dry.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 633 PM CDT Wed Jun 28 2017

Two areas of ongoing convection early this evening. The first was
ahead of the cold front over northeast Iowa into southwest
Wisconsin that will stay south of both airports. The second was
ahead of the area of low pressure that was over east central
Minnesota. This activity has the potential to impact both airports
as it slides east/southeast this evening and will include this
possibility in both forecasts. Once this activity moves through,
it should be quiet for the remainder of the period. The winds will
swing around to the west once the cold front goes through with
speeds generally around 10 knots or less.


&&

.HYDROLOGY...Through Friday Night
Issued at 330 AM CDT Thu Jun 29 2017

Heavy rain fell across parts of southwest Wisconsin and northeast
Iowa on Wednesday and Wednesday evening. The legacy storm total
precipitation (STP) estimated anywhere from 2 to 5 inches across
much of Fayette, southern Clayton, and southern Grant counties.
This is in agreement with the storm total amounts from the dual
pol. This has resulted in flooding along the Turkey River in
northeast Iowa. Both Elkader and Garber have already rose above
flood stage. With the rapid rise taking place at Garber, this site
will have the potential of making moderate flood stage. Meanwhile
Elkader is beginning to slow its increase, so it looks like it
will stay with minor flooding.

We issued a flood warning for Whitewater Park too. However, this
river has already crested and it is on its way down. We might be
able to cancel this warning sometime this morning.

For this afternoon and early evening, the precipitable water
values climb into the 1.5 to 2 inch range and warm cloud layer
rise into the 3.5 to 4.5 km range south of Interstate 90. This
would make the showers and storms very efficient rain producers.
Fortunately, the CAMs are in good agreement that this convective
system will be progressive, so it should not aggravate the
flooding situation taking place along the Turkey River.

&&

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

$$

SHORT TERM...Boyne
LONG TERM...Boyne
AVIATION...04
HYDROLOGY...Boyne


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.