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Area forecast discussion 
National Weather Service Kansas City/Pleasant Hill MO
316 PM CST Thu Nov 27 2014

Discussion...
issued at 316 PM CST Thursday Nov 27 2014

Quiet weather is expected through much of the forecast, punctuated by
a distinct warm up Friday into Saturday and strong frontal passage
Sunday with very cold air filling behind it.

For Friday through Saturday, southerly low-level flow is expected
with strong warm advection. 850mb temperatures climb into the 14c to
16c range, which would support temperatures in the 70s if mixing to
that level could occur. Rather, mixing will remain shallower and
closer to around 925mb, but this will still result in temperatures
that are about 10 degrees above normal for this time of year. Even
warmer conditions are expected Saturday as warm advection persist
resulting in surface temperatures in the 60s.

A strong cold front is expected to move through the area Sunday.
Models continue to be in good agreement showing this passage
sometime during the day. But the finer details of the timing remain
very uncertain. The GFS remains the fastest and as a result is the
coldest for Sunday high temperatures. The timing of the European model (ecmwf) and
the Gem are much more similar to each other and a bit slower.
Looking back to previous anomalously warm days, the Gem has been in
the top 3 regarding verification while the GFS usually ranks poorly
due to a cold bias. With the latest European model (ecmwf) supporting the Gem output,
confidence is higher in a slower frontal passage. This thinking
basically splits the forecast area in two from Schuyler County in northwest
Missouri to Johnson County in Kansas. Very warm conditions are
expected ahead of the front with highs in the 60s likely from
Boonville to Clinton. Temperatures will very likely not budge from
overnight lows in far northwestern Missouri. So locations from
Maryville to Rockport should see highs in the mid 30s. It is also
entirely possible that the temperature gradient could be even more
extreme, perhaps close to 40 degrees around noon on Sunday. With such
a tight gradient, a difference of an hour or two in timing of the
front could result in a 20 degree temperature bust. Needless to say,
confidence through the center of the forecast area, in a southwest
to northeast orientation, is low as it's just impossible to know
precisely where the front will be at a particular time during the
day.

Confidence in the forecast for the remainder of the extended remains
low as the GFS and European model (ecmwf) remain out of phase. Both models show a
strong upper low off the West Coast. The GFS is quick to break down
the western Continental U.S. Ridge and progress the trough east into the center
of the country by Wednesday night. The European model (ecmwf) maintains the upper
ridge over The Rockies through Wednesday night and as a result the
flow over the Continental U.S. Is out of phase. The impacts of this at the
surface are such that the GFS develops a Lee trough with southerly
flow over eastern Kansas and western Missouri. With the ridge
depicted by the ECMWF, colder high pressure prevails over the area.
This results in a 30+ degree temperature spread between the two
models. Based on National guidance, preference seems to be in favor
of the European model (ecmwf) and its ensembles. So have modestly trended towards a
cooler solution for now.



&&

Aviation...(for the 18z tafs through 18z Friday afternoon)
issued at 1053 am CST Thursday Nov 27 2014

VFR conditions will continue through the forecast period. Mid-level
clouds will remain in place through much of Thursday prior to
scattering out overnight. Winds will vary initially while
becoming southeasterly and increasing slightly with time.



&&

Eax watches/warnings/advisories...
Kansas...none.
MO...none.
&&

$$

Discussion...cdb
aviation...Welsh

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