Area Forecast Discussion
Issued by NWS La Crosse, WI

Home | Current Version | Previous Version | Graphics & Text | 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
000
FXUS63 KARX 201742
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1242 PM CDT Sun May 20 2018

.SHORT TERM...(Today through Tuesday)
Issued at 230 AM CDT Sun May 20 2018

Latest watervapor satellite imagery highlighting an upper level
shortwave across the central plains-ia, with various curls in the
flow spinning across southern parts of the region. The upper level
forcing was having a healthy hand in the ongoing convection that
stretched from ia into southern wi.

Meso models gradually weaken/diminish the area of showers as the
morning wears on and as the the upper level energy shears out.
Mostly the pcpn holds south of I-90 as strong drying persists in the
north (900-800  mb td depressions near 20 C later this afternoon).
Parent shortwave trough eventually gets a nudge east later
tonight/Mon which should result in a smattering of more light
showers. Weakly forced, no instability to speak of, and likely minor
qpf.

Temperatures are going to take a tumble for the next couple days,
thanks in part to widespread clouds and the scattered showers.
Warmest areas today will be north of I-94 where sunshine is more
likely.

.LONG TERM...(Wednesday through Saturday)
Issued at 230 AM CDT Sun May 20 2018

The suite of models continue to trend toward inching an upper level
shortwave trough (maybe more of an mcv) eastward from the plains tue
night, sliding it across what`s likely a west-east sfc boundary
hanging out somewhere near the IA/MN border. Should be an area of
showers/storms with the forcing, but as it moves east, it moves
away from the main branch of low level moisture transport and the
better CAPE pool. Plus, it will have to contend with a drier
atmosphere in residence across WI and a rather weak, ridging flow
a loft. How much the expected convection will hold together as it
advances east might be the biggest question. Feel there should be
a good shot for showers and a few storms west of the Mississippi
River, and likely diminishing in coverage as they move east. Will
sketch out the pcpn chances to reflect that.

The ridge will gradually edge to the east toward the end of the work
week as a shortwave trough in the northern branch of the upper level
flow drops southeast from Canada. The EC and GFS spin this across
the Upper Mississippi River Valley Friday night, driving it into the
eastern great lakes later on Sat. Some low level moisture transport
to help fuel showers/storms. SBCAPEs overdone in the GFS due to an
overly rambunctious sfc dew point, but should be at least
weak/marginal instability to help aid convection. Shear still looks
weak.

As for temperatures, look for a rebound as the weak ridging a loft
and return to a southerly flow pulls milder air back into the
region. Highs expected to be 5 to 10 degrees above the late May
normals.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1242 PM CDT Sun May 20 2018

MVFR stratus (possibly IFR at KRST) will continue at both TAF
sites through at least mid-afternoon before cloud bases rise
slightly. VFR ceilings look to be the rule later this evening and
into the early overnight before clouds drop back below 3000 ft agl
early Monday morning and continue through the rest of the period.

Scattered showers, especially at KLSE, have resulted in some
reductions in visibility due to mist. These restrictions will
gradually lift through the afternoon as lingering showers
dissipate and move out of the region. Some additional showers are
possible Monday morning, but lower confidence in coverage
precludes mention in 18Z TAF issuance.

Winds through the period will be light from the east-northeast,
generally 10 kts or less.

&&

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

$$

SHORT TERM...Rieck
LONG TERM....Rieck
AVIATION...Rogers



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