Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 201014

Area Forecast Discussion
National Weather Service Tucson AZ
314 AM MST Tue Feb 20 2018

.SYNOPSIS...As the cool air mass behind the cold front that moved
through last night continues to settle over the area, showers will
diminish this morning and skies will clear from the west through
the day. High temperatures will top out 13 to 20 degrees cooler
than average today. Cooler than average temperatures will
continue into the weekend with a chance for a few showers on


.DISCUSSION...Despite the best efforts of the high-res models to
get rid of the showers late last evening, they continue this
morning and looking at the low level water vapor imagery suggests
that it will continue for several more hours as it slowly eases to
the east. Just this last hour the drier low level air finally made
it to the Tucson area so would expect showers in the immediate
vicinity to come to an end very soon. I adjusted pops through the
morning hours to slow up the tapering of the showers a bit as well
as increasing the could cover. I may have to extend them a bit
more across eastern areas, especially the Whites and will keep an
eye on that. Speaking of the White mountains, opted to let the
Winter Weather Advisory continue until 5 am as upslope flow
continues with accumulating precipitation noted on area gauges.

Otherwise, gradual clearing from the west later today as the cool
and dry air mass advects across the area. High temperatures will
be quite a bit cooler than yesterday and topping out well below
normal for a change. Actually, today`s average temperature should
end up below normal for the first time since January 27th. With
the clearing skies along with the cool and dry air mass in place,
temperatures late tonight into Wednesday morning will be quite
cool with near or below freezing temperatures east and south of
Tucson. In the immediate Tucson area lows are expected to be near
or just above freezing for the metro area with a few outlying
areas dipping below freezing.

For Wednesday through Thursday a few upper level waves passing
through the base of the trough will enhance clouds at times and
bring a small chance of a shower or two near the New Mexico border
and the White mountains. The more noticeable aspect for most will
be the continued cooler than average temperatures.

Friday a more significant shortwave will round the base of the
trough and the models are gradually converging on a similar
solution however the GFS remains the most aggressive. Based on
the continued trend toward this feature being real and fairly
significant I lowered temperatures a bit and raised pops a bit for
a somewhat larger area of showers and highs mostly in the 50s in
the valleys.

Saturday looks to be dry and continued cool then Sunday into
Monday temperatures jump up 5-10 degrees under mostly clear


.AVIATION...Valid thru 21/12Z.
SCT-BKN cloud layers with ceilings generally 4-8k ft AGL. Isolated
to scattered valley -SHRA and MTN -SHSN mainly to the south and east
of KTUS this morning. Brief MVFR conditions possible in/near -SHRA/-
SHSN. SFC wind WLY/SWLY at 8-15 kts with a few gusts near 20 kts
into this evening. The strongest speeds will occur at
KDUG/KALK/KFHU. Dry conditions at all terminals by late this
afternoon with skies clearing from west to east tonight into
Wednesday morning. Aviation discussion not updated for TAF


.FIRE WEATHER...Isolated to scattered valley rain and mountain snow
showers will continue this morning east of Tucson. Dry conditions
and well below normal temperatures will occur this afternoon into
Sunday morning, except for a slight chance of showers Friday and
Friday night. 20-ft west to southwest winds will occur through
Thursday and generally remain less than 15 mph. Slightly elevated
west or southwest winds may then occur Friday with less wind
occurring this weekend.


Winter Weather Advisory until 5 AM MST early this morning for



FIRE WEATHER...Carpenter

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