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Area forecast discussion
National Weather Service Omaha/valley NE
307 am CDT sun Apr 20 2014
Short term...(today through tuesday)
issued at 305 am CDT sun Apr 20 2014
Precipitation chances into Monday continue to be primary challenge
in short term.
At the surface a stalled boundary from near Columbus to Sioux City
at 08z is forecast to lift a bit north and/or wash out today as
shortwave energy tracks across the northern U.S. And a southern trough
moves a little north of east across Southern Plains. Forecast area
generally remains in between these systems today/tonight...although
a weak lobe apparently is/will continue to pivot up into forecast area from
southern system. However...moisture remains on low side especially
below 850 mb and any moisture there is was having a hard time
overcoming modest cap currently in place per 00z oax/lbf/top
soundings. Model quantitative precipitation forecast has been poor...generally overdoing
precipitation...and confidence in various solutions they give are low to
say the least. That said...there is some weak convergence near
boundary and middle level moisture does seem a bit more this morning
given middle deck ceilings at some locals and altocumulus castellanus appearance to morning
satellite imagery. And with heating would suspect some increase in
probability of precipitation are in order later this afternoon through this evening and then
overnight as northern wave sends cold front into ecntrl zones. Overall
though trimmed most probability of precipitation a bit.
It also looks less likely that temperatures today will be held
down substantially by widespread precipitation or continual thick
cloudiness with even last hold-out European model (ecmwf) coming around to warmer
readings. Generally boosted a few degrees.
Some moisture/instability lags across southeastern zones Monday
afternoon...possibly even behind weakening cold front per NAM. Because
of that lingered a slight chance far southeast into middle afternoon. Otherwise precipitation
chances will be decreasing behind front as winds and probably
fire danger increase again as dewpoints lower into the 30s/low
40s and highs reach 70 or better.
Return flow expected Tuesday with similar readings to Monday.
Long term...(tuesday night through saturday)
issued at 255 am CDT sun Apr 20 2014
Warm advection precipitation chances still look to be on the
increase Tuesday night/Wednesday period as strong low level jet overspreads
area in advance of deepening upper trough. GFS/European model (ecmwf) have trended
with less coverage for part of Wednesday and have responded with
warmer guidance values...most notably the European model (ecmwf). Boosted highs a
few degrees over previous forecast/earlier model blend on Wednesday.
Although some uncertainty on how far east front pushes during the
day Wednesday...still appears some severe weather threat will
exist...possibly a bit farther southeast than it looked earlier.
Although we'll have to overcome a strong wrly-downslope component
to low level winds behind front on Thursday...heating and some
moisture lags as main circ center...by then the probably
developed...upper low will likely remain northwest of the forecast area.
Thus the lingering probability of precipitation per previous forecast still look in order.
Somewhat cooler temperatures also in order Friday into Saturday as upper
trough axis shifts eastward...but amount of which will likely change as
exact latitude it does eventually shift becomes more certain.
Also late next weekend...new day 7...looks potentially interesting...
especially per 00z European model (ecmwf).
Aviation...(06z tafs for kofk...klnk and koma.)
Issued at 1145 PM CDT Sat Apr 19 2014
VFR conditions are expected through the period. A weak surface
front remains near kofk and the winds there are light and
variable. This trend is expected to continue for several more
hours before the front lifts northwest and the winds go south
similar to koma/klnk. Rain showers have been slow to develop and have
removed precipitation mention from kofk taf...but an isolated rain showers still
remains possible near the boundary overnight. We do expect a
better coverage of rain showers on sun but with timing and coverage
uncertainties we will leave the tafs dry at this time.