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FXUS63 KARX 191210
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
710 AM CDT Sun Aug 19 2018

.SHORT TERM...(Today and tonight)
Issued at 254 AM CDT Sun Aug 19 2018

Early this morning, valley fog has already developed along the
Mississippi River and many of its tributaries. Expect this fog to
continue through mid-morning before dissipating. Visibility could
be reduced to 1/4 mile or less at times, so motorists should slow
down and allow extra time to reach their destination.

For the rest of today, surface high pressure will drift east of
the forecast area allowing southerly return flow to develop. Dry
conditions will continue, but expect increasing high clouds
through the day ahead of a 500 hPa closed low across the Central
Plains. Afternoon highs will top out in the lower to mid 80s.

The 500 hPa low moves over Kansas City by 12Z Monday with its
surface low near the MO/IA border. Rain chances increase from west
to east, although some guidance hints that much of tonight will
remain dry. Mostly cloudy skies will keep temperatures elevated
with lows mainly in the 60s.

.LONG TERM...(Monday through Saturday)
Issued at 254 AM CDT Sun Aug 19 2018

Still some differences in surface low track for Monday's system,
although a model consensus brings it across southern IA into
northern IL with the 19.00Z GFS being the outlier a bit farther
north. That said, latest GFS/NAM develop strong low-mid level
frontogenesis across the forecast area north of the low track.
When combined with strong Q-vector convergence aloft, mid-level
moisture advection, and PWATs approaching 2.0 inches, expect
periods of moderate to locally heavy rain through much of the day.
MUCAPE tops out around 1500 J/kg by 00Z Tuesday across the
southern half of the forecast area, falling off to the north.
Expect embedded thunderstorms for much of the area, but most
widespread south of I-90. Overall lower instability/shear precludes
a severe threat, although rainfall of 1-2 inches appears likely
along and south of I-90 with locally higher amounts possible,
especially along the deformation axis.

Much of the area has received 0.5 to 2.0 inches of rain over the
past week with scattered higher pockets mainly across southern WI.
River levels are also generally low, so not expecting flooding
issues unless prolonged training of heavier showers/storms occurs.
As the placement of the deformation axis becomes more certain,
will be able to better pinpoint potential problem areas.

Monday and Tuesday likely to breezy as well with frequent gusts up
to at least 25 mph. Cloud cover/rain should limit deep mixing, but
higher gusts are still possible within stronger showers/storms.
Temperatures will be on the chilly side for late August with
highs only in the low 70s.

Rain will exit from west to east on Tuesday with dry conditions
returning for Wednesday/Thursday as high pressure builds across
the region. Temperatures in the 70s will be the rule. The next
best chance for showers and storms will be Friday as another
stronger short-wave moves across the Upper Midwest.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 708 AM CDT Sun Aug 19 2018

LIFR valley fog expected to impact KLSE this morning. All
ingredients are present for this to remain at 1/4SM through 14Z,
with rapid dissipation after.

Otherwise, VFR expected.

&&

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

$$

SHORT TERM...Rogers
LONG TERM...Rogers
AVIATION...Baumgardt
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