Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 181052
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
350 AM MST Tue Feb 18 2020

.SYNOPSIS...Dry conditions with above normal daytime temperatures
through Thursday. A few showers may develop Friday, then scattered
to numerous to prevail Friday night and Saturday as a weather system
moves across the area. A chance of showers exists Saturday evening
mainly east of Tucson, then dry conditions return Sunday into Monday.

&&

.DISCUSSION...Clear skies prevail across southeast Arizona early
this morning along with light surface winds. Generally zonal flow
aloft will continue across the area into Wednesday. This pattern
will translate into sunny skies or a few cirriform clouds today,
then increasing cirriform clouds from the south tonight into early
Wednesday. Clouds are expected to decrease Wednesday afternoon
followed by clear skies later Wednesday night.

Various 18/00Z models continue to depict upper ridge amplification
over this forecast area Thursday ahead of a deepening low pressure
system near the California coast. Flow aloft will become
increasingly southwesterly Thursday night as the upper ridge axis
moves east of the area, and low pressure aloft becomes centered west
of southern California. The upshot is for dry conditions to continue
Thursday into Thursday night, and most likely Friday morning as
well.

Thereafter, a few showers should develop Friday afternoon especially
east of a Safford-Sierra Vista line as the upper low approaches the
southern California coast. The 18/00Z GFS/GEFS and ECMWF/ECENS were
in fairly decent agreement regarding the expected precip potential
starting Friday evening and continuing into Saturday as the upper
low moves eastward into southern California by midday Saturday. As
such, forecast confidence has increased regarding start/end timing
of rainfall and high elevation mountain snow, as well as projected
liquid amounts and snow accumulations associated with this system.

At any rate, the official forecast continues with isolated to
scattered showers favoring locales east of Tucson Friday evening,
then scattered to numerous showers across much of the area late
Friday night into Saturday afternoon. The upper low is progged to
fill while moving rapidly eastward into eastern New Mexico by
daybreak Sunday. As such, isolated to scattered showers mostly east
of Tucson Saturday evening followed by a return of dry conditions
late Saturday night. Dry conditions will then prevail Sunday into
Monday under northwesterly flow aloft.

The event total rainfall amounts are presently forecast to generally
range up to around 0.30 inch in the valleys, and mainly from 0.10"
to 0.50" across the mountains. However, liquid amounts approaching
0.80" may ultimately occur across the White Mountains. Event total
snowfall amounts of 2-6 inches should be limited to above 8000 feet.

High temperatures this afternoon and Wednesday will range about 5-9
degrees above normal. Even warmer temperatures are on tap Thursday,
and portions of the Tucson metro area may reach or exceed 80
degrees. A cooling trend will prevail Friday into Saturday followed
by warmer temperatures returning especially next Monday.

&&

.AVIATION...Valid through 19/12Z.
SKC-FEW clouds above 20k ft MSL into this afternoon becoming SCT-BKN
clouds above 20k ft MSL later tonight and into Wednesday morning.
Surface wind variable in direction under 12 kts. Aviation discussion
not updated for TAF amendments.

&&

.FIRE WEATHER...Dry conditions with above normal daytime
temperatures through Thursday. A few showers should develop Friday,
especially during the afternoon hours, then scattered to numerous
showers Friday night into Saturday. Expect isolated to scattered
showers mainly east of Tucson Saturday evening, then dry conditions
return Sunday into Monday. 20-foot winds will be terrain driven
under 15 mph through Wednesday. Some gusty east to southeast winds
should occur at times Thursday afternoon into Friday, then gusty
southwest winds Saturday afternoon. Somewhat less wind to prevail
Sunday into Monday, although occasional west to northwest afternoon
gusts are forecast to occur.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

DISCUSSION...Francis
AVIATION...Michael
FIRE WEATHER...Michael

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