Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 110417

Area Forecast Discussion
National Weather Service Tucson AZ
917 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...Water vapor imagery shows west to northwest flow aloft
continuing with a batch of mid and high level cloudiness seen in IR
imagery currently moving east southeast across central and southern
Arizona. That said, will make adjustments to sky cover for the
remainder of tonight to account for recent satellite trends. In
addition, will adjust short term hourly temp and dewpoints to also
account for latest trends. Otherwise, forecast is on track.

See previous discussion below for details beyond tonight.


.AVIATION...Valid through 12/06Z.
FEW-SCT clouds AOA 20k ft AGL becoming BKN late tonight into Sunday.
SFC 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 TAF amendments.


.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.


.PREV DISCUSSION...The quasi-zonal flow aloft pattern is progged to
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/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/ECMWF were somewhat similar with
the depiction of a deepening upper trough over the western CONUS
Friday into next Saturday. However, the GFS was deeper, further west
and markedly more robust with moisture/PoPs versus the 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






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