Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 191610

Area Forecast Discussion
National Weather Service Tucson AZ
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 CWA 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 RAOB had 0.56" of PWAT 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 WSW 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 AGL with occasional MVFR
ceilings/visibilities mainly this morning. Cloud decks will increase
late this evening into Monday morning. Light SFC 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.


.PREV 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.


    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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