fxus65 ktwc 191610 

Area forecast discussion 
National Weather Service Tucson Arizona 
910 am MST sun Feb 19 2017 

Synopsis...a chance of valley rain and mountain snow will continue 
through this afternoon, with showers ending tonight. Dry conditions 
will occur Monday into next Saturday except for a few snow showers 
across the White Mountains Wednesday night and Thursday. Expect a 
sharp warming trend into Wednesday with cooler temperatures late in 
the upcoming week. 


Discussion...kemx was back in precip Mode this morning with 
scattered rain and snow showers moving slowly thru the County Warning Area from west 
to east. Visible satellite imagery indicated mostly cloudy 
conditions for Southeast Arizona, as WV imagery clearly depicted low 
pressure tracking across the state from southwest to northeast. The 
19/12z ktwc radiosonde observation had 0.56" of precipitable water with the majority of moisture 
below 500 mb. 

Mt. Lemmon had received between 6 and 8 inches of snowfall as of 8 
am this morning. With the thought that there is still enough 
moisture and instability around on the back side of this low to pop 
off some shallow convection into this afternoon, have decided to 
continue the west-southwest products thru 20/00z for the mountain zones above 
7500 ft. On the upside, south/southwest winds will not be nearly as 
gusty today, with speeds mainly less than 15 kts through this 
afternoon. Precip chances will begin to decrease late this afternoon 
and this evening with clearing from southwest to northeast overnight 
into Monday. 

No updates this morning. Please see the additional sections for 
further details. 


Aviation...valid through 20/18z. 
Scattered to numerous valley -shra and mountain shsn will occur into 
this afternoon, with precipitation coverage decreasing markedly 
early this evening. Dry conditions will occur Monday. Cloud decks 
will generally be 3.5-8k ft above ground level with occasional MVFR 
ceilings/visibilities mainly this morning. Cloud decks will increase 
late this evening into Monday morning. Light surface wind becoming 
sly/swly at 8-13 kts with gusts of 15-20 kts this afternoon, then 
decreasing to mainly less than 10 kts tonight into Monday morning. 
Aviation discussion not updated for taf amendments. 


Fire weather...a chance of valley rain and mountain snow will 
continue into this evening as a strong Pacific storm system begins 
to depart the region. Expect some breezy southwest 20-ft winds this 
afternoon. Dry conditions, a warming trend and normal diurnal wind 
patterns will then occur Monday through the middle of the week. 
There may be a few snow showers across the White Mountains Wednesday 
night and Thursday. Gusty winds are expected to return Thursday 
afternoon along with cooler temperatures into the upcoming weekend. 


Previous discussion...a storm system continued to track through Arizona 
early this morning with lingering showers. Models move this system 
east of the area by this evening. Expect instability showers and 
possibly a thunderstorm or two this afternoon before clearing this 
evening and tonight. Thereafter, a strong ridge of high pressure 
aloft will bring dry conditions and much warmer daytime 
temperatures, especially Tuesday and Wednesday. Models were still 
showing another system passing north of the area that could bring a 
few showers to the White Mountains Wednesday night and Thursday. 
Another system may impact the region late next weekend. 


Twc watches/warnings/advisories... 
Winter Storm Warning until 5 PM MST today for azz510-511- 
513-514 above 7500 feet. 

Winter Weather Advisory until 5 PM MST today for azz512 
above 7500 feet. 



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