Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 192145

Area Forecast Discussion
National Weather Service Tucson AZ
245 PM MST Mon Feb 19 2018

.SYNOPSIS...Winter returns to southeast Arizona this week as a
couple of weather systems will bring gusty winds, valley rain and
mountain snow into Tuesday. Freezing temperatures return to the
lower elevations Tuesday night into Wednesday morning from mainly
Tucson east and south. Temperatures will remain below normal
through the end the week with another chance of showers Friday.


.DISCUSSION...Southerly winds have been gusting in the 25 to 40
mph range in the valleys and 35 to 55 mph range in the mountains.
Isolated light showers/high elevation snow showers were occurring
mainly east of Tucson this afternoon while up the road in NW Pinal
county there was a line of showers with embedded isolated
thunderstorms out ahead of the approaching cold front. Blowing
dust has also developed in advance of this cold front and we
posted a short term blowing dust advisory thru 5 pm for south-
central Pinal county. This cold front will continue to push east
tonight bringing a quick shot of valley rain and mountain snow
showers. The best chances for accumulating snows will be above
7500 feet with snow possible down to as low as 4000 feet post
frontal. Little accumulation expected as bulk of precipitation
will be ahead of the falling snow levels. Will continue the winter
weather advisory for Mt. Graham and the White Mountains. Cold
front east of the area later tonight with upper level trof by
Tuesday morning.

Much colder airmass across the area on Tuesday with highs running
14 to 18 degrees below normal. Then much colder overnight lows
Tuesday night into Wednesday morning with freezing temperatures
likely from Tucson east and south. A weak upper level trof moving
across the area may bring enough clouds to keep temperatures from
realizing full cold potential. As the above mentioned trof moves
east across the area on Wednesday it may have enough dynamics to
work on residual moisture that will be near the Arizona/New Mexico
border to generate isolated light valley showers and mountain snow
showers. Increased PoPs a bit for the Whites Wednesday afternoon
and evening. Little snow accumulation expected up there.

Another weak upper level trof moves across the area on Thursday in
advance of a deep upper level trof that will move across the state
on Friday. This deeper/colder upper level trof is being handled
differently by the models with the GFS deeper/colder than the more
progressive and not a deep ECMWF. For now went with a blend
between the models with gusty southwest winds a given. Could see a
scenario and showers will be associated with the cold front moving
across the area. Confidence low at this time.

Dry next weekend with a warming trend to near normal. Temperatures
for the remainder of the week into next weekend will be pleasantly
below normal. Love it.


.AVIATION...Valid thru 20/23Z.
SCT-BKN cloud layers with ceilings generally between 4-8k ft.
Isolated to scattered valley -SHRA and MTN -SHSN mainly to the
south and east of KTUS as a cold front passes through this
evening. Brief MVFR conditions possible in/near -SHRA/-SHSN. SFC
wind southwesterly/westerly at 18-28 kts with gusts between 30-40
kts until around midnight. The strongest speeds are expected at
the KFHU/KDUG terminals. After midnight winds will start to
gradually decrease with speeds between 8-12 kts at KTUS and KOLS.
KDUG will remain slightly elevated with southwest winds at 12-17
kts and gusts between 25-30 kts after midnight into Tuesday
afternoon. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Isolated to scattered valley rain and mountain snow
showers will continue into Tuesday morning as a couple of weather
systems track through the southwest. Dry conditions and well below
normal temperatures will then occur Tuesday into Sunday morning,
with a few showers possible Friday afternoon. 20-ft southwest winds
will be gusty this afternoon, generally 20-30 mph with gusts up to
40 mph. Wind speeds will generally remain less than 15 mph Tuesday
and Wednesday. Slightly elevated west or southwest winds may then
occur late in the work week.


 Winter Weather Advisory until 5 AM MST Tuesday for AZZ510.

 Wind Advisory until 11 PM MST this evening for AZZ503>514.

 Winter Weather Advisory until 11 PM MST this evening for AZZ511.

 Blowing Dust Advisory until 5 PM MST this afternoon for AZZ505-



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