Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 161920
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
220 PM CDT Sun Jul 16 2017

.SHORT TERM...(Tonight through Tuesday Night)
Issued at 220 PM CDT Sun Jul 16 2017

High Impact Weather Potential: Thunderstorm chances return Tuesday
into Tuesday night. While uncertainty regarding timing/placement
remains on the higher side, there could be a low end risk for a few
severe storms later Tuesday and Tuesday night.

Fairly quiet weather has made a welcome return to the area the past
12-18 hours, courtesy of low level ridging building south from
Ontario. That feature will very slowly meander east through the
Great lakes into Monday, continuing to influence our weather locally
with a stretch of dry and less humid conditions as diurnal mixing
helps lower dew points back through the 50s and low 60s east of
the Mississippi while a tighter dew point gradient hangs somewhere
closer to the I-35 corridor. Will need to watch cloud trends
closely as plenty of hints are there that some low level moisture
will cycle around the periphery of the ridge and may result in
another near-sunrise blossoming of stratus/stratocumulus
especially west of the Mississippi on Monday. Regardless, the
start of the work week not looking too shabby by mid July
standards, with some good viewing for potential aurora activity
this evening.

Bigger focus remains Tuesday-Tuesday night as broad flat ridging/
zonal flow regime begins to set up over much of the central CONUS,
but with continued hints of a weak shortwave traversing the flow in
concert with a weak frontal boundary sliding southeast toward the
area. Returning moisture into that boundary should set the stage for
increasingly unstable conditions to our north and west initially,
with broad moisture transport into parts of Minnesota and northwest
Iowa likely helping to fuel some showers and storms Monday night.
Lots of questions then into Tuesday/Tuesday night regarding the
evolution of any additional convection, with uncertainty regarding
how much (if any) residual cloud cover could hamper destabilization
down this way. Nevertheless, it does appear per recent guidance
trends that a period of better moisture transport/low level jet
forcing may nose into the area toward Tuesday evening and night,
though with the usual concerns of exact placement and timing so
prevalent to longer range convective forecasts. Band of modest
westerly flow just touching the area from the north could support
sufficient shear for some storm organization and maybe severe
potential (linear convection?), but again we`ll have to see how
instability trends play out heading into Tuesday evening.

.LONG TERM...(Wednesday through Sunday)
Issued at 220 PM CDT Sun Jul 16 2017

Classic summertime pattern expected over much of the central CONUS
right on into next weekend, featuring broad but expansive mid level
ridging centered over the southern Plains/lower Mississippi River
Valley and our local area just on the northern fringe of that ridge.
That setup leaves us vulnerable to occasional ridge-running
shortwaves, giving a typical potential MCS setup somewhere across
the region. Still quite a few questions about where our frontal
boundary from Tuesday night will end up, as that feature will serve
as a focus for possible convection. Latest trends to push that
boundary southward into Wednesday/Thursday look to match what we
usually see in these setups, especially if convection Tuesday night
can become better organized, helping punt that front down well into
Iowa and thus shifting the better convective focus southward.

Unfortunately, this really will be one of those "wait and see"
patterns through much of next week as we will have to take a daily
look at where the "stalled" boundary resides post-convection.
Suffice it to say several periods of convection do remain possible,
with potentially a heavy rain threat somewhere if convective rounds
target the same areas, but confidence in placement and timing
remains very low. Along the same lines, temperatures each day will
be highly dependent on cloud and/or rain trends, with a consensus
blend by far the best way to go at this point.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1239 PM CDT Sun Jul 16 2017

Diurnal clouds between 3 and 4K will affect both TAF sites through
late afternoon. These clouds will then dissipate this evening with
the loss of diurnal heating. Winds will gradually shift from
northeast to southeast tonight as a ridge axis moves east through
the region. A few of the models hint that an IFR to MVFR deck of
clouds may affect parts of northeast Iowa and southeast Minnesota.
This will include KRST. Confidence was not high enough to include
them at this time.

&&

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

$$

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



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