Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 201652

Area Forecast Discussion
National Weather Service Tucson AZ
Issued by National Weather Service PHOENIX AZ
952 AM MST Tue Mar 20 2018

.SYNOPSIS...Strong high pressure aloft will provide much warmer
temperatures into Thursday. Expect record or near record high
temperatures on Thursday. A weather system will then bring a slight
chance of showers mainly north of Tucson Friday. Cooler temperatures
and gusty winds will also occur. Dry conditions with temperatures
closer to seasonal normals this weekend and early next week.



Clear skies are being reported across our CWA this afternoon as a
strong ridge of high pressure is positioned over the desert SW.
Temperatures bottomed out in the low 40s and upper 30s around
Tucson this morning but will quickly warm into the upper 70s
today. Very dry conditions will also persist on Tuesday as the
boundary layer remains void of any substantial moisture. The
forecast looks on track for today, see previous discussion below
for additional details.


.PREV DISCUSSION... /issued 405 AM MST Tue Mar 20 2018/

IR satellite imagery and surface observations depicted clear
skies across much of southeast Arizona early this morning.
However, a few thin cirriform clouds were moving eastward mainly
across the White Mountains. Upper ridge axis extended from
southern Baja California northwestward to near the northern
California coast. Meanwhile, deep low pressure aloft was centered
well west of the central California coast vicinity 32N/140W.

The upper ridge axis will amplify and move eastward into the
Intermountain West and including the southwest CONUS Wednesday as an
upper trough deepens near the West Coast. Mostly clear skies will
likely occur into Wednesday as the bulk of thicker clouds and deeper
moisture remains west to northwest of this area. Mainly high level
clouds will thicken Wednesday night into Thursday as the upper ridge
moves east of the area, and the upper trough approaches the
California coast.

The main impact from the upper ridge translates into a strong
warming trend into Thursday. For instance, high temperatures this
afternoon will generally be about 6-10 degrees warmer versus Monday.
Forecast high temps Thursday are expected to be about 8-15 degrees
or so warmer versus this afternoon. Thus, record or near record
temps Thursday appears increasingly likely for at least portions of
this forecast area, or particularly from Tucson eastward to the New
Mexico state line.

The 20/00Z GFS/ECMWF/CMC depict an impulse/upper speed max to eject
eastward into the Great Basin Thursday night, then further eastward
across the southwest CONUS Friday. These solutions suggest the bulk
of measurable precip will occur north of this forecast area. The
ECMWF seems to be a reasonable compromise solution versus the drier
GFS, and the wetter CMC solution. The ECMWF depicts the best chance
of albeit light rainfall amounts to generally occur west to north of
Tucson, and this scenario is similar to the official forecast.

There is a slight chance of showers mainly across western Pima
County late Thursday night, then a slight chance of showers mostly
north of Tucson Friday. Snow levels will remain mainly above
mountain tops. Dry conditions to return Friday evening and continue
at least through Sunday under swly/wly flow aloft. Thereafter, the
GFS/ECMWF depict a deepening upper trough over the southwest CONUS
by next Monday. The ECMWF depicted measurable precip to occur across
portions of central/northern Arizona, while the GFS maintained
precip-free conditions. Based on these solutions, have kept dry
conditions into next Monday.

After the unseasonably warm temperatures Thursday, cooler
temperatures will occur Friday with very minor daily cooling
prevailing this weekend.


.AVIATION...Valid through 21/12Z.
Clear skies to scattered clouds above 20k ft AGL into Wednesday
morning. Surface wind mainly less than 10 kts thru the period,
although a general wly/nwly component will occur this afternoon and
early this evening. Aviation discussion not updated for TAF


.FIRE WEATHER...Dry conditions with a strong warming trend through
Thursday. There is a slight chance of showers Friday especially
north of Tucson as a weather system moves north of the area. Dry
conditions will return Saturday into next Monday. 20-foot winds
terrain driven mainly less than 10 mph into Wednesday. Expect some
gusty southwest to west afternoon winds at times Thursday into this





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