Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 290820
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
320 AM CDT SUN MAY 29 2016

.SHORT TERM...(Today through Wednesday)
Issued at 320 AM CDT Sun May 29 2016

Showers speckle the radar scope out there early this morning, with
an upper trough overhead but lifting northeast while an associated
surface cold front is just about to slip out of the eastern CWA at
07Z. In addition to the smattering of showers, some fog and lower
stratus has developed in spots with a moist airmass in place and
lightening winds along/behind the front. Heading through day, the
primary forecast issue remains chances for any additional showers
this afternoon, and honestly have to say I`m not terribly impressed
by the potential. From a forcing perspective, there just isn`t a
whole lot once we lose our upper trough (and remaining showers) by
mid morning, though to be fair a weak shortwave crossing central
North and South Dakota currently is progged to slide over our way,
in addition to perhaps a weakish secondary surface trough axis
dropping into the area. The biggest issue looks to be boundary layer
moisture, with the NAM/GFS too high with dew point values well into
the mid 60s, while their respective mixed layer values and forecast
raobs suggest values down into the mid 50s look more reasonable. As
such, have a hard time seeing much if any instability development,
save for perhaps east of the Mississippi River where things may mix
out a little less to support maybe 250 J/KG MLCAPE beneath some
cooling aloft, maybe leading to a couple of showers.

Looking quiet tonight with low/mid level ridging firmly building in
aloft, with lower dew points and clear skies likely supporting
comfortable lows back into the 50s for most spots. With wet ground
from recent rains, could see some fog development, especially along
and east of the Mississippi in valley locations. Thereafter, some
trickiness into Memorial Day itself with regard to additional precip
chances. Guidance has really been struggling with northward extent
of returning moisture through Iowa the past few days, and gut
feeling is the more southerly displaced solutions with regard to
moisture/instability are the way to go as low level ridging hangs
firm across the area and low level flow maintains a northerly
component. That may change heading into Monday night with the
development of stronger return flow and approach of an elevated warm
front and lead wave in advance of a robust northern stream closed
low working toward the northern Plains. Broad layer warm advection
ascent should bring at least a risk for precip lifting north through
the area, though elevated instability remains meager with maybe 250-
500 J/KG CAPE and limited shear for no severe weather threat.

That northern Plains upper low is expected to shift into northern
Minnesota by Wednesday with broad ascent continuing to deliver some
additional rainfall across the area. Given expected widespread cloud
cover across the area through midweek, get the feeling that overall
instability will remain limited with the potential for curtailed
heating Tuesday afternoon, with probably only an isolated/scattered
thunder risk in a broader rain shield. Similar to Monday night, just
not seeing a whole lot of shear for any severe threat. Per current
trends, it appears rain will shut down quickly from west to east on
Wednesday as a cold front arrives and modest subsidence/drying sets
in through the day.

.LONG TERM...(Wednesday Night through Saturday)
Issued at 320 AM CDT Sun May 29 2016

In contrast to an active weather stretch for the start of the work
week, things are looking rather quiet into late week and next
weekend, with continued hints of notably cooler and less humid
conditions as upper troughing sits across the region while low level
ridging also dominates. With pronounced thermal troughing in place
and 850mb temps hovering in the 2-7C range, envision highs in the
mid 60s to mid 70s with some quite comfortable humidity levels.
Can`t completely rule out a diurnally driven shower on Thursday with
hints of a stronger shortwave dipping through the mean trough and
coolness aloft supporting some weak instability, with otherwise dry
conditions likely through Friday night, and maybe a few showers
returning by Saturday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1150 PM CDT Sat May 28 2016

Periods of MVFR to IFR conditions are expected at the TAF sites
tonight in low stratus and BR. Low pressure moves across the TAF
sites tonight, and combined with a moist airmass, will produce
some stratus and BR at times. KLSE will mainly see the MVFR
conditions while KRST is expected to see IFR. Mixing increases
Sunday morning and conditions will improve to VFR. Look for west
winds to increase into the 12 to 14 kt range during the day on
Sunday with gusts to 22 kts possible. Also, a broken stratocumulus
deck is expected on Sunday with cloud bases in the 3500 to 4000 ft
range. Clouds will scattered out Sunday evening and west winds
subside as weak high pressure edges in.

&&

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

$$

SHORT TERM...Lawrence
LONG TERM...Lawrence
AVIATION...WETENKAMP



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