Scientific Forecaster Discussion
fxus65 ktwc 102155
Area forecast discussion
National Weather Service Tucson Arizona
255 PM MST Sat Dec 10 2016
Synopsis...dry conditions with well above normal daytime
temperatures will prevail into Thursday. Cooler temperatures with a
slight chance of valley rain and mountain snow showers will then
occur next Friday into Saturday.
Discussion...clear skies prevail across much of Southeast Arizona
at this time, although some mid and high-level clouds were
encroaching upon western Pima County from south central Arizona. The
quasi-zonal flow aloft pattern is progged continue during the next
several days. This pattern will bring periods of mid and high-level
clouds with daytime temps remaining well above normal. 10/12z GFS/
European model (ecmwf)/CMC were similar with depicting some upper ridge amplification
Wednesday followed by continued well above normal 500 mb heights
next Thursday. Thus, some record high temps or near-record high
temps may occur Wed-thur.
Thereafter, the deterministic GFS/European model (ecmwf) were somewhat similar with
the depiction of a deepening upper trough over the western Continental U.S.
Friday into next Saturday. However, the GFS was deeper, further west
and markedly more robust with moisture/pops versus the European model (ecmwf).
Meanwhile, the CMC depicted ridge amplification over the eastern
Pacific next Friday, and the mid/upper level trough axis was much
further east versus the GFS/ECMWF, or a north-south oriented trough
axis over the central/southern rockies.
Given the differing solutions, forecast confidence regarding precip
potential next Fri-Sat is somewhat low at this time. For this
forecast issuance, only fairly minor adjustments were made to the
gridded data pop values. Thus, have continued with a slight chance
of showers across much of the area Fri-Sat, and a chance of snow
showers across the mountains from northeast of Tucson to the White
Aviation...valid through 12/00z.
Few-scattered clouds at or above 20k ft above ground level becoming scattered-broken late tonight into
Sunday. Surface winds generally less than 12 kts thru the forecast
period. A few gusts to 15 or 20 kts may occur during the peak
heating hours of the afternoon. Aviation discussion not updated for
Fire weather...above normal temperatures will persist through the
end of the upcoming work week. 20-ft winds will generally remain
less than 15 mph with a few higher afternoon gusts. Dry conditions
are expected through Thursday, with a potential disturbance bringing
cooler temperatures, a chance of precipitation and gusty winds to
the region Thursday night into next weekend. However, confidence in
timing and track of this system remains low.