Area forecast discussion 
National Weather Service Tucson Arizona 
300 PM MST Friday Nov 21 2014 

Synopsis...expect isolated to scattered showers mainly southwest to 
southeast of Tucson tonight as a weak low moves south of the area. 
Light precipitation amounts will prevail. Dry conditions will then 
occur this weekend and next week. There will be another round of 
cold overnight lows the first half of the week with a warming trend 
later in the week. 


Discussion...kemx WSR-88D detected isolated 30-45 dbz echoes over 
the tohono o'odham nation west of Tucson at this time. The rest of 
Southeast Arizona was void of precipitation echoes. A few lightning strikes have been 
detected during the past hour southeast of Organ pipe National Monument. 
Isolated to scattered showers and a few thunderstorms will continue 
to move/develop eastward into this evening. The favored areas for 
measurable precipitation will be across the southern portion of the tohono 
o'odham nation...Santa Cruz County...and southwestern Cochise County. Have 
maintained isolated showers for the Tucson metropolitan area this 
evening...and dry conditions should prevail north of Tucson. 

As the upper low moves southeastward across northern Sonora late tonight... 
isolated showers will still be possible south-to-southeast of 
Tucson. Expect dry conditions area-wide Sat morning as the upper low 
moves well southeast of the area. Liquid amounts from this precipitation event 
should be mostly less than one tenth of an inch. Snow levels this 
evening will fall to around 7500 feet...with only flurries to occur 
across the highest elevations. 

Drier northwesterly flow aloft will prevail this weekend and early next week. 
Two shortwave troughs will move southeastward across the central rockies 
sun-Mon. A tight middle-level gradient should produce gusty westerly/northwesterly 
winds Sun afternoon especially east of Tucson. The orientation of 
the middle-level gradient favors the upper Gila Valley with the 
stronger winds. Some gustiness may also occur Monday afternoon... 
although wind speeds in general should be less versus sun. 
Thereafter...high amplitude ridge axis adjacent the West Coast Tuesday 
will move eastward and flatten across the area Thanksgiving day. Clear 
skies or mostly clear skies will be the rule...with locally gusty 
east winds Wednesday-Thursday in response to a somewhat tight surface pressure 
gradient. Dry conditions will continue Friday under westerly flow aloft. 

Expect a few degrees of daily cooling Sat-Monday followed by much warmer 
daytime temperatures during the middle and latter part of the upcoming 
week. Another period of freezing temperatures and hard freezes for mainly 
eastern locales appears to be increasingly likely Sun night through Tuesday 
night. At this time appears that the Tucson metropolitan area will not 
experience freezing temperatures...or at least widespread freezing temperatures. 


Aviation...valid through 23/00z. 
An upper low over SW Arizona will move southeast into Chihuahua Mexico by 
Saturday morning. This will generate isolated to scattered -shra and a few 
-tsra...mainly near the international border into this evening with 
a few remaining -shra near kdug through late tonight. The cirrus deck 
over the eastern two thirds of the region will continue moving east and 
will be east of the area by 22/04z. Scattered-broken cumulus over the western third 
of the area will develop to the east and southeast through 22/04z then primarily 
remain over the southeast corner through 22/12z. Mostly clear skies 
expected areawide after 22/12z. Surface winds generally 10 kts or less 
through 23/00z except for local 10-15 knots southerly winds this evening. 
Aviation discussion not updated for taf amendments. 


Fire weather...a passing upper low will generate isolated to 
scattered rain showers with a few mountain snow showers into this 
evening...especially near the international border. Isolated 
thunderstorms have developed this afternoon and that possibility 
remains into the evening hours...again mainly near the international 
border. Then a couple of upper level disturbances moving northeast 
of the area will bring gusty west to northwest winds Sunday and 
Monday during the afternoon hours. The upper Gila Valley should see 
the strongest winds with speeds of 20-25 miles per hour and gusts into the 30s 
on Sunday with min relative humidity values in the upper teens to middle 20s. Relative humidity 
levels will be lower Monday however winds will not be as strong. 
Otherwise dry with cold overnight lows the first half of next week 
followed by a warming trend late in the week. 


Twc watches/warnings/advisories...none. 



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aviation/fire weather...cerniglia 

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