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Area forecast discussion
National Weather Service La Crosse WI
620 am CDT Mon Mar 27 2017

Short term...(today through Tuesday night)
issued at 258 am CDT Mon Mar 27 2017

The slow moving nearly vertically stacked low that has impacted the
region for the past few days has finally moved eastward into the
eastern Great Lakes. Another upper level wave located across
Kansas at 08z this morning will move from the Central Plains into
the mid-Mississippi Valley by this evening. Most of the precip
with this system should stay to the south of our area as the
surface low passes well south across the Ohio Valley. Meanwhile,
another weaker northern stream wave will move from the northern
plains towards Lake Superior. In between these systems, little in
the way of precip is expected over much of the area today.
However, with low-levels remaining saturated and some weak
forcing, a few light showers/drizzle are possible underneath the
stratus deck, especially across north-central WI closer to the
northern stream wave. Temps should warm a few degrees higher than
Sunday to near seasonal averages, with light winds.

Tonight into Tuesday drier air will work into the region as high
pressure builds southward towards the Great Lakes. Gradual clearing
is expected tonight into Tuesday, although forecast soundings and
relative humidity fields do indicate some lingering moisture below 850 mb into
Tuesday morning, so it may take some time to clear out the clouds
completely. Assuming plenty of sunshine, Tuesday should be very
pleasant, with highs well into the 50s and light winds.

Long term...(wednesday through sunday)
issued at 258 am CDT Mon Mar 27 2017

The break from the unsettled weather pattern will be short-lived
with another upper low expected to move from the Desert Southwest
Wednesday northeast to the lower Great Lakes by Friday. The
overall forecast idea has not changed significantly with a
surface low lifting northeastward towards the lower Great Lakes by
Friday morning. The 27.00z European model (ecmwf) continues to indicate more
interaction with a northern stream wave and a farther north precip
shield. The less consistent GFS been trending northward as well
over the past few runs but the 00z run would keep north-central
WI dry. That said, precip is expected to gradually approach from
the south and west late Wednesday, possibly initially slowed by
dry easterly low-level flow. Precip would then increase later
Wednesday night and Thursday with increased low-level moisture
transport and stronger 850-700 mb warm advection/frontogenesis.
With remaining model differences, exactly where the northern edge
of the precip ends up is still in question, and gefs members
indicate plenty of spread with precip amounts. In addition to
amounts, there may also be precip type concerns. Temps on Thursday
may be cooler than currently forecast wherever the deformation
zone precip axis sets up on Thursday. The latest GFS/European model (ecmwf) would
keep parts of the area in the mid 30s for highs so, it's possible
there could be at least some mixed snow on the northern edge of
the precip shield Wednesday night and Thursday. There is not a lot
of cold air available, with 850 mb temps near 0c and surface
temps likely in the low 30s or higher, but it will be something to
watch as confidence in the evolution of the system increases.

Behind this system high pressure is expected to bring a break from
precip, with forecast confidence decreasing late next weekend with
greater spread in the deterministic/ensemble guidance. Temps should
climb behind the departing system back near or above average for the
weekend.

&&

Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 620 am CDT Mon Mar 26 2017

Cigs: low stratus expected to hang around for the better part of
today, with a little diurnal bump up to MVFR anticipated for the
afternoon. Main cloud mass expected to move east/south this evening,
but how far is in question. Plus, despite the exiting of the parent
low pressure system, moisture remains locked in underneath the low
level inversion tonight. Meso models inch the northern extend of the
low clouds just south of the taf sites this evening, and will follow
suit in the forecast. However, confidence is not high, and may need
to hang onto MVFR longer into tonight.

Weather/vsby: areas of fog this morning with a lot of Ebb and flow with
lower and improved vsbys...making it challenging to time the worst
conditions. Expect the variable vsbys to continue into mid late
morning, settling into VFR before 18z. Meso/sref models not pointing
to a return to lower vsby fog tonight - and will follow suit for
now. Can't rule it out completely though, and some MVFR br possible
overnight.

Winds: mostly light north, going more east toward 12z Tue.

&&

Arx watches/warnings/advisories...
WI...none.
Minnesota...none.
Iowa...none.
&&

$$

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