Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 292105

Area Forecast Discussion
National Weather Service Tucson AZ
205 PM MST Sat Apr 29 2017

.SYNOPSIS...Winds will diminish this evening as our wind maker low
pressure system pushes into the Central and Southern Plains. Cooler
temperatures tonight with a freeze expected in some colder eastern
valleys. High pressure will bring dry conditions and a strong
warming trend for the new week.


.DISCUSSION...Much drier with the cooler airmass today. Surface
dew points in the single digits to lower teens, down 30 to 40
degrees compared to yesterday. The 12z KTWC sounding showed
precipitable water plummeting to 1/5 of an inch and latest
satellite estimates confirm that trend into afternoon hours. The
winds have behaved a little better today as the low weakens a bit
pushing through New Mexico and lifting into the central and
southern Plains.

Coolest night in 3 or 4 weeks tonight with a patchy late season
freeze in colder eastern and southern valleys. Freeze warning in
effect Sunday morning for areas east and south of Tucson.

High pressure takes control next week as the strong ridge near the
west coast builds inland and pushes our temperatures quickly back
to around 7-12 degrees above average later in the new week. We
could see the first 100 of the year at TIA by Friday, but right
now the best bet is upper 90s.


.AVIATION...Valid through 01/00Z.
VFR with SKC conditions or FEW-SCT clouds AOA 15k ft AGL mainly NE
of KTUS. Isolated -SHRA/-SHSN in the White Mountains NE of KSAD
through this evening, then dry conditions through Sunday. Gusty
WLY/NWLY SFC winds at 14-18 kts with gusts to near 30 kts this
afternoon becoming terrain driven at less than 10 kts overnight. NE
SFC wind on Sunday at mainly less than 12 kts. Aviation discussion
not updated for TAF amendments.


.FIRE WEATHER...Much drier today with relative humidity dropping to
7-12 percent in valley areas despite the cool temps. An isolated
rain or snow shower may occur across the White Mountains through
this evening. Otherwise, no precipitation over the next 7 days.
Northwesterly breeziness will continue this afternoon across eastern
areas, with 20-ft winds of between 15 and 25 mph and gusts to 35
mph. Thus, a Red Flag Warning remains in effect for parts of fire
weather zones 151 & 152 through 8 pm this evening.

From Sunday onward, wind will not be a big issue though some
afternoon breeziness is expected with the peak heating of the day.
However, the air mass will be very dry all week with single digit
afternoon humidity levels and daytime temperatures gradually
climbing from near average Sunday, to 10-15 degrees above average by
the end of the week.


Red Flag Warning until 8 PM MST this evening for AZZ151-152.

Freeze Warning from 1 AM to 7 AM MST Sunday for AZZ503-507>509.




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