Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 210400

Area Forecast Discussion
National Weather Service Tucson AZ
900 PM MST THU OCT 20 2016

.SYNOPSIS...Expect gusty east to southeast winds into Friday
morning, then winds will diminish Friday afternoon. Increasing
moisture will then bring a slight chance of showers Saturday
afternoon followed by a better chance of showers and thunderstorms
on Monday. Dry conditions will return Tuesday into next Thursday.


.DISCUSSION...Evening satellite imagery showed a clear sky across SE
AZ. At the surface, gusty easterly winds were occurring and these
should continue through the overnight hours into late Friday
morning. Strong upper high over the area will continue well above
normal high temperatures across the area on Friday. A few spots,
like Tucson, will be near record highs for October 21st. Details on
increased moisture this weekend leading to a chance of showers can
be found below in the previous discussion.


.AVIATION...Valid through 22/00Z.
Expect SKC into Friday afternoon. Surface wind into Friday morning
will be ely/sely 10-20 kts with gusts to near 25 kts. Surface wind
diminishing Friday afternoon to mainly less than 10 kts. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...Gusty east to southeast winds will continue into
Friday morning. Wind speeds will diminish Friday afternoon, then
terrain driven winds will be generally less than 15 mph this weekend
and into next week.

Otherwise, expect dry conditions through Saturday morning, then
increasing moisture for at least a slight chance of showers starting
Saturday afternoon and continuing into Monday. The best chance for
any wetting rainfall of significance will be Monday when some
thunderstorms may also occur. Dry conditions will then prevail
Tuesday into next Thursday.


.CLIMATE...Today marked the 14th consecutive day of at least 90
degrees recorded at Tucson International Airport for October 2016.
This currently ties the tenth longest period of 90 degrees or warmer
on record. The current official forecast suggests that 90 degrees or
warmer should continue through Sunday. If this occurs, there will be
17 consecutive days this month of at least 90 degrees recorded at
Tucson International Airport. This 17 consecutive day period would
be the sixth longest on record.


.PREV DISCUSSION...20/12Z GFS/ECMWF/CMC were similar with depicting
increasing moisture to move southwest-to-northeast across southeast
AZ Saturday in response to high pressure aloft moving east of the
area, and a deepening upper trough near the Pacific Northwest. Have
opted to introduce a slight chance of showers Saturday afternoon
generally from Tucson southward to the International border. The
various NWP solutions as well as WPC QPF guidance suggests an
earlier onset of measurable (albeit quite light) rainfall amounts
versus NWP solutions from 24 hours and longer ago.

Moisture should continue to increase Sunday as southwesterly flow
aloft continues ahead of a very deep upper low near the Pacific
Northwest coast. A slight chance of showers exists Sunday and Sunday
night, then PoPs were boosted into the chance-category for much of
southeast AZ Monday. There were fairly distinct differences between
the 20/12Z GFS/ECMWF deterministic solutions for precip potential
Monday, with the GFS markedly wetter versus the ECMWF. Appears the
ECMWF keeps the bulk of deeper moisture well northwest of this
forecast area versus the GFS.

At any rate, per coord with neighboring WFO`s, there is now a chance
of showers and thunderstorms for most locales Monday. A chance of
showers continues Monday night mainly from Tucson east to the New
Mexico border. A slight chance of showers continues Tuesday mainly
across the White Mountains with dry conditions elsewhere. Dry
conditions should then prevail Tuesday night into next Thursday as
high pressure aloft amplifies over the southwestern CONUS/southern

Expect above normal daytime temperatures to continue this forecast
period, despite a modest cooling trend to occur early next week.





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