Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 232350
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
650 PM CDT Thu Mar 23 2017

.UPDATE...
Issued at 650 PM CDT Thu Mar 23 2017

Second severe weather event, and it`s not even April yet. As
alluded to yesterday, was a bit wary of the potential for some
sneaky stronger convection across the area late this afternoon,
and the atmosphere delivered, with reports of quarter to even golf
ball hail over parts of northeast IA into Grant County, WI. The
higher instability axis responsible for the "fun" continues to
rapidly transit northward on the leading edge of notable deep
layer moisture advection, with more of a showery band working back
into the region from northwestern IA within an axis of weak but
developing frontogenetic ascent.

Per trends the past 6 hours, starting to wonder if the more steady
rain band later tonight might end up a bit farther south than
currently advertised, with near-term guidance trends shifting in
this direction. Even the farther north NAM/GEM solutions (at least
from a QPF perspective) indicate the strongest deep layer
frontogenetic response down toward the I-90 corridor or just
slightly north, suggestive that areas north of I-94 may tend to
end up more on the drier side of the FGEN downward branch
circulation. Have trended our forecast more in the southern camp
of solutions for later tonight, with just a small risk for
isolated thunder given remnant 100-200 J/kg elevated CAPE in the
axis of strongest lift along the surface/elevated warm front.
Don`t envision any severe potential from any overnight storms -
thankfully.

&&

.SHORT TERM...(This evening through Friday)
Issued at 321 PM CDT Thu Mar 23 2017

At 3 PM, a small area of showers and scattered thunderstorms were
moving east across northeast Iowa and along the Minnesota/Iowa
border. This was developing along an elevated warm front. There
has been a few reports of hail to around 1 inch in diameter. In
addition with very dry air below the cloud bases, some of the
showers have been producing wind gusts up to 40 mph.

From tonight into Friday, a cold front will slowly sink southward
through the forecast area. Moderate 850 mb moisture transport will
raise the precipitable water values to around 1.25 range. This is
around 3 standard deviations above normal. With most unstable
CAPES up to 250 J/kg, there will be a possibility for isolated to
scattered thunderstorms. The highest CAPES and the best 0-6 km
shear will be this evening and this could result in the potential
for some hail up to 1 inch in diameter. Rainfall amounts along
and north of Interstate 90 will range from 1 to 2 inches.

.LONG TERM...(Friday night through Thursday)
Issued at 321 PM CDT Thu Mar 23 2017

From Friday night into Saturday morning, a cold front will move
slowly south across the area. Southerly winds ahead of an
approaching upper level low will bring a narrow band of Gulf of
Mexico moisture northward into the region and this moisture will
pool along this front. Precipitable water values will range from
an inch to 1.25 inches. This 2.5 to 3 standard deviations above
normal. Fortunately, the moisture transport will be weak to
moderate, the most unstable CAPES are generally less than
150 J/kg, and there is generally weak convergence along this
front. This will keep the hourly rainfall rates under control.
Rainfall totals during this time frame will range from a half to
1 inch. The heaviest rain will be found along and south of the
Interstate 90 corridor. Meanwhile further north, there are some
questions on where the northern extent of this precipitation will
be located. This could present some issues for the potential of
light freezing rain in north central Wisconsin. However with this
said, confidence remains low that this will even occur.

From Saturday afternoon into Monday, a slow moving upper level low
pressure area will move south and southeast of the forecast area.
Wrap around moisture will keep a chance of showers into the
forecast area. Additional rainfall amounts will be less than a
tenth of an inch.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 650 PM CDT Thu Mar 23 2017

Batch of showers and thunderstorms continues to exit the area, but
with another round of lighter showers likely just skirting
LSE/RST the next few hours. Current IFR to MVFR ceilings should
lift back to VFR levels through the evening hours, before lowering
back to MVFR and eventually IFR late tonight into Friday as
periods of rain develop along a warm front draped over the region.
A period of low level wind shear also appears likely for all
areas roughly 04Z-08Z with a strong low level jet just off the
deck, but with overall surface winds shifting from southeast to
north/northeast tonight/Friday as the warm front stalls across the
area.

&&

.HYDROLOGY...Tonight through Saturday
Issued at 321 PM CDT Thu Mar 23 2017

Like the past couple of days, it continues to look like anywhere
from a half to 1.50 inches of rain will fall across the area from
tonight through Saturday. There may be even a few locations that
could potentially see rainfall totals up to 2 inches. With this
rain falling over over a long duration, only in bank rises are
currently expected for area streams and rivers.

&&

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

$$

SHORT TERM...Boyne
LONG TERM...Boyne
AVIATION...Lawrence
HYDROLOGY...Boyne



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