Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 250356

Area Forecast Discussion
National Weather Service Tucson AZ
855 PM MST Fri Feb 24 2017

.SYNOPSIS...Dry conditions will prevail through Saturday along with
cooler temperatures. A brief warmup on Saturday before a fast moving
system pushes across the area on Sunday. A stronger Pacific storm
will bring a chance of valley rain and mountain snow to the area on
Monday and Tuesday along with below normal temperatures. Dry and
warmer weather returns starting Wednesday.


.DISCUSSION...The upper pattern is defined by zonal flow across
Southeast Arizona, with a trough of low pressure moving off the
coast of the Pacific Northwest. Latest satellite imagery indicated a
few thinning high clouds tracking from west to east through Sonora
Mexico this evening, with clear skies across our neck of the woods.

Dry airmass in place across Southeast Arizona with surface dewpoints
in the single digits to teens. This is also evidenced by a dry
25/00Z KTWC sounding profile, with a precipitable water value of
0.18 inches. This dry airmass, combined with the clear skies will
result in another chilly night tonight, with lows in the valleys in
the upper 20s to low 30s(East of Tucson) to mid 30s(Tucson west).
This is all reflected well in the inherited forecast, so no updates
will be necessary.


.PREV DISCUSSION...A series of Pacific weather systems will keep a
small roller coaster ride in temperatures over the next 5 days
before much warmer temperatures return to the area late next week.

Zonal flow tonight will bring some thin high clouds otherwise it
will be clear with overnight low temperatures continuing on the cool
side, similar to this morning.

Warmer Saturday, but still below normal, under a mix of high clouds
and sunshine. Our next precip weather maker will be moving down the
California coast. This feature will quickly move across the area on
Sunday bringing increased cloud cover and a chance of rain/snow
showers mainly to the White mountains. Elsewhere mainly virga with a
few sprinkles around due to drier low levels. Highs Sunday will
be 4-6 degrees cooler than Saturday.

A little warmer with clouds increasing once again on Monday as the
next Pacific weather system, this one a little stronger, approaches
the area. There is a slight chance of showers late Monday afternoon
into Monday evening. However the best precipitation chances window
will be late Monday night into Tuesday. Not big precip maker.

After that strong warming trend Wednesday thru Friday.


.AVIATION...Valid through 26/06Z.
Clear skies to scattered clouds above 20k ft AGL into Saturday
evening, with increasing high clouds Saturday afternoon. Surface
wind generally less than 10 kts. Saturday afternoon, surface wind
will be wly/nwly 10-15 kts with gusts to 25 kts. The strongest
wind will be east of KTUS in the vicinity of KDUG and KSAD. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...Dry conditions will prevail areawide through
Saturday night. There will then be a slight chance of showers across
the eastern half of the forecast area Sunday, with even higher
precipitation chances in the White Mountains. A Pacific system will
bring a chance of valley rain and mountain snow showers, late Monday
into Tuesday. Dry conditions will return next Wednesday through
Friday. Expect gusty west to northwest 20-foot winds during the
afternoon and early evening hours primarily east of Tucson through
Tuesday, with breezy to windy 20-foot winds across Cochise county on
Sunday. Critical fire weather thresholds may be met for a few hours
Sunday afternoon across the southern half of Cochise county, with
winds speeds easily exceeding criteria, but minimum relative
humidity values and fire danger both marginal at this time.





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