Area Forecast Discussion
Issued by NWS Tucson, AZ
FXUS65 KTWC 121559
Area Forecast Discussion
National Weather Service Tucson AZ
859 AM MST Thu Jan 12 2017
.SYNOPSIS...Mild temperatures today under a mix of sun and
clouds. A few sprinkles possible Friday, then a low pressure system
will bring a chance of valley rain and mountain snow over the
weekend into early Monday along with cooler temperatures. Dry
conditions with warmer temperatures Tuesday and Wednesday. Another
storm system may impact the area later next week.
.DISCUSSION...More of the same today with patches of mainly high
cloud and temperatures several degrees above average. We`ve
actually seen some drying at 700hPa over the past 12 hours and are
left with mainly cirrus level moisture for the time being. That
will change over the next 36 hours as layered elevated moisture
returns. Winds will continue to slowly back around to the
southwest as the consolidating low currently near northern
California digs further south in response to amplified features
upstream and downstream. Our current forecast has solid trends,
but we might end up being a touch underdone with our precip
Saturday afternoon and Saturday night.
Please see the previous discussion below for additional details.
.AVIATION...Valid through 13/18Z.
SCT-BKN clouds AOA 18k ft AGL. Surface wind generally less than
12 kts. Aviation discussion not updated for TAF amendments.
.FIRE WEATHER...Dry conditions with mild daytime temperatures
will continue through today. A low pressure system will then move
into the region over the weekend, resulting in a chance of valley
rain and mountain snow. Dry conditions are expected to return Monday
through Wednesday of next week. Outside of some elevated south to
southeast 20-foot winds at 10-20 mph on Friday and Saturday, 20-foot
winds Sunday through Wednesday of next week are expected to be
terrain driven and generally less than 15 mph.
.PREV DISCUSSION...Our next precipitation system is currently off
the Oregon coast this morning. By later this afternoon the upper
low will be near Frisco and then drop S to off the southern
CA/northern Baja coast late Friday afternoon. By Saturday morning
the closed low will be north of the Baja Spur and then lift E-NE
across northern Sonora/far SE AZ later Saturday night into Sunday
morning. A little slower than previous solutions and we`ve been
backing off on the timing of precipitation.
Moisture values will start to increase on Friday under S/SW flow
aloft where a few sprinkles is possible as the atmosphere moistens
up from top down. Isolated to scattered light showers west and north
of Tucson Friday night will gradually increase in areal coverage on
Saturday with best chances for scattered to numerous showers
occurring Saturday afternoon into early Sunday morning. Snow levels
lowering into the 5500 to 6500 foot area Saturday night into Sunday
morning with the lower end being near the center of the low, which
would mean across the southern sections. Forecast snow amounts above
6500 feet range from 4-11 inches depending on mountain ranges.
Valley QPF values are forecast to range from 0.10" to 0.70".
As the upper low lifts NE into the central plains late Sunday into
Monday, several upper level trofs will move across the area keeping
unsettled conditions Sunday night into Monday with a few lingering
showers far eastern areas on Tuesday.
Highs will be below normal Saturday through Wednesday. Freezing
temperatures return to the eastern areas Tuesday and Wednesday
Another storm system is possible late next week.
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