Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Las Vegas Nevada
156 PM PST Wednesday Feb 10 2016
Synopsis...Spring like weather will continue across the region
through the rest of the week with dry and unseasonably warm weather
expected. Scattered high clouds will pass through the area at times
and locally breezy conditions will remain along the Colorado River
near Laughlin and Bullhead City.
Short term...through Friday.
Very quiet and pleasant weather is expected through the remainder of
the work week with high temperatures running a good 10-15 degrees
above normal in snow-free areas. Little change was made to the
inherited forecast as high pressure remains entrenched across the
region. Persistent northerly winds down the Colorado River valley
the last few days will also gradually weaken through the end of the
Long term...Saturday through Tuesday.
Long-duration amplified ridge in the west weakens this weekend with
an onslaught of vorticity maxima progressing into the Pacific
northwest. Models are trending faster and weaker with the shortwave
trough reaching the coast 00z-12z Saturday with the GFS a bit slower
than the European model (ecmwf). The faster progression of the trough corresponds to
a somewhat weaker depiction of the high-amplitude ridge, undoubtedly
owing to a rather potent predecessor negatively tilted trough
progressing through the ridge late this week well north of our area.
Main effect this has on the weekend forecast is the degree of
cooling expected as the southern stream portion of the vorticity maximum
moves through the area. General impression is that the shortwave
trough looks a tad weaker today than yesterday, and with the
slightly weaker looking ridge on Saturday compared to how it was
depicted 24 hours ago...thinking that there will be somewhat less
cooling from Saturday to Sunday than what was forecast 24 hours ago.
Nevertheless, these changes are quite minor (a matter of a degree or
two cooler on Saturday and a degree or two warmer on sunday). Trough
passage is expected to be dry regionwide with breezy north winds
after trough passage on Sunday and Monday, particularly for the
Colorado River valley. Longwave ridging recommences early next week.
Models continue to depict a low cutting off in the subtropical
eastern Pacific as the weekend system progresses through the west.
What exactly happens to this low is anyone's guess, as models are
struggling mightily with how this low interacts with an upstream
large-scale trough progressing through the east Pacific into the
West Coast next week. 00z European model (ecmwf) shows reasonable
phasing/amplification with the trough as it moves through the west
middle-to-late next week, but also shows a rather dry depiction of the
southern portion of the trough. Meanwhile...00z GFS looks wetter but
actually closes off a secondary low off the California coast that
progresses through our region late next week, creating a second
period of widespread precipitation for the southwest. 00z CMC looks at
least reasonably similar to the 00z ECMWF, and the 06z dgex looks
reminiscent of the 00z GFS. 18z dgex had the east Pacific low moving
northeast into the southwest bringing widespread precipitation
throughout the region on Wednesday (something hinted at by the model
24 hours before) but has essentially zero support from any other
deterministic model solution. Very brief look at 06z GFS shows a
much different depiction of the Pacific trough's passage through the
west the middle of next week (much slower and farther north) with a
subsequent cutoff low developing much farther northwest than its 00z
counterpart suggests. However, it does progress this cutoff into the
southwest the following weekend.
Such large spread from model to model and such large changes in
continuity from model run to model run, quite common with cutoff
lows progressing into longwave ridges, lead to high uncertainty in
the forecast next week. Through Tuesday, it appears warm and dry
weather will hold (fairly high confidence), but after that is not at
all clear. Plenty of time to figure things out, though.
Aviation...for McCarran...generally light winds under 6 kts
favoring typical diurnal trends this week. No other operationally
significant weather expected.
For the rest of southern Nevada...northwest Arizona...and southeast
California...generally light winds under 6 kts favoring typical
diurnal trends this week. The exception will be some enhanced
northerly winds down the Colorado River valley with gusts to around
20 kts at times. No other operationally significant weather
Spotter information statement...spotter activation is not expected.
Please report any significant weather according to Standard operating
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