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Area forecast discussion 
National Weather Service La Crosse WI
634 am CDT sun may 24 2015

Short term...(today and tonight)
issued at 247 am CDT sun may 24 2015

Pleasant weather last few days will be ending today as impact from
broad upper trough over western U.S. Begins to be felt across
cornbelt and western Great Lakes. Main focus continues to be timing
of rain over next couple days...along with lower risk of any severe

Upper low continues to slowly move through central rockies with
several short wave troughs rotating around base and into the Central
Plains early this morning. This has been generating wide spread
convection from Interstate 80 southward although instability and
lightning risk remains well south.

As lead wave ejects northeast this morning...expect rain shield to
continue northeast as well...which is handled well in short term
mesoscale models. Have adjusted rain threat to match trends...which
will increase from southwest to northeast after daybreak. May take
quite awhile to reach Interstate 94 battling drier air initially.

Behind this wave...could see a break in rain threat during part of
the afternoon before next wave...which appears stronger in
guidance...forces more convection into area tonight. May be a bit
optimistic but trended rain chances down for part of the
afternoon...with back to categorical tonight. Cape is basically none
for much of day but some elevated MUCAPE develops tonight as deeper
moisture begins to approach. This combined with broad diffluent flow
will certainly aid development of more widespread rain and perhaps a
few thunderstorms...especially in southern forecast areas where
influence of low level jet ahead of wave could be strongest.

Long term...(monday through saturday)
issued at 247 am CDT sun may 24 2015

Still looking like upper low will develop into open wave and move
northeast more rapidly on Memorial Day. Best low level moisture
transport occurs early Monday though as previously mentioned
stronger wave advects northeast. Models track surface low across the
area and draw warm sector briefly into area with much higher mixed
layer cape values setting up just south of the area. If we break
into sunshine...temperatures will likely climb quick so did raise a
few degrees.

Instability will be the limiting factor it appears with ample 0-3km
shear available for limited threat of damaging wind or hail if any
stronger storms develop Monday afternoon or evening. Details on any
threat may have to be worked out near real-time depending on how
earlier convection inhibits setup. Marginal risk via Storm Prediction Center seems on
track but again...would not be surprised if slight level
probabilities are added at some point.

Boundary from earlier system will likely be just south of the area
Tuesday but yet another short wave could trigger more convection
along this...bringing highest rain risk across mainly south and
southeast areas.

While we could see a break from rain threat middle week...mean upper
trough across northern rockies and northern Midwest will continue to
eject weak short wave troughs and produce rain threats into next
weekend before North Branch of split flow becomes more dominant and
pushes front through.


Aviation...(for the 12z tafs through 12z Monday morning)
issued at 634 am CDT sun may 24 2015

Main taf concerns are MVFR/IFR/LIFR conditions and
showers/thunderstorms chances at both rst/lse taf sites today into
tonight. Low pressure moving into southern Iowa tonight will
continue to advect moisture northward into the area today. Latest
mosaic radar shows showers over much of Iowa and Missouri. Latest
11z metars indicate VFR conditions across southern Minnesota...
northeast Iowa and southwest Wisconsin. The combination of low
level moisture advecting northward into the area today...and
vertical motion associated with the surface low...expect ceiling
heights to lower and showers to become more widespread this
morning. Thunderstorm potential looks minimal at this
the latest 24.06z GFS/NAM indicate very little or if any
instability today into tonight across the region. Will continue to
leave mention of thunder out of both rst/lse taf sites. The 24.06z
GFS/NAM BUFKIT soundings show ceilings lowering to MVFR/IFR...potentially
to LIFR at rst taf or around 00z Monday. Have introduced
earlier time of IFR/MVFR conditions at both lse/rst taf sites
around 00z Monday...with potential of LIFR condition at rst after
02z Monday.


Arx watches/warnings/advisories...


Short term...Shea
long term...Shea

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