Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 172235
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
335 PM MST Sun Jun 17 2018

.SYNOPSIS...Dry conditions with a warming trend this week. The
hottest temperatures will likely occur Friday followed by slightly
moderating temperatures next weekend.

&&

.DISCUSSION...Visible satellite imagery and surface observations
depict a few to scattered cumuloform clouds generally from Tucson
eastward to the New Mexico state line this afternoon. Clear skies
were noted across western Pima County and south central Pinal
County. The vertically-challenged cumulus clouds will dissipate
during the next few hours with the loss of daytime heating. Thus,
clear skies later tonight followed by clear skies or perhaps mainly
a few cumulus clouds again Monday.

Various 17/12Z numerical weather prediction models were in excellent
agreement Tuesday with the depiction of at least a 594 dm high to be
centered just west of northern Baja California or near 30N/120W. The
upper high is then progged to amplify over the southwest CONUS
Wednesday into Thursday. The model moisture fields suggest that
southeast Arizona will be hard-pressed for clouds, or certainly any
clouds of consequence, starting Tuesday and continuing at least into
Thursday and perhaps Friday as well. Thus, the main impact will be a
pronounced warming trend that began this afternoon and will prevail
at least through Thursday.

By Friday, there were some differences between the 17/12Z
deterministic GFS/ECMWF regarding the upper pattern over the
southwest CONUS. In essence, the ECMWF depicted a somewhat deeper
shortwave trough moving eastward across the Great Basin versus the
GFS. Aside from a few cumulus clouds mainly across the White
Mountains, clear skies are expected to occur again Friday. Due to
the more amplified shortwave trough, the ECMWF was not quite as
robust with the hottest temps for Friday versus the GFS. At any
rate, still appears Friday will have the hottest temps this forecast
period, and Excessive Heat Criteria may ultimately be achieved for
some portions of southeast Arizona.

Thereafter, the upper high is depicted via the 17/12Z GFS/ECMWF to
retrograde to west of the California coast, perhaps eventually
centered near 35N/130W or so. These solutions also depict some
increase in moisture to occur by next Sunday, especially east to
southeast of Tucson. The ECMWF maintained precip-free conditions
next weekend, but the GFS depicted measurable precip to eventually
encroach upon far southeast sections next Sunday afternoon. Given
low forecast confidence regarding the GFS solution, have maintained
precip-free conditions next weekend. However, forecast confidence is
higher regarding a scenario that includes some moderation in daytime
temps by next Sunday.

&&

.AVIATION...Valid through 19/00Z.
FEW-SCT clouds 6-12k ft AGL into this evening becoming SKC overnight
into Monday. Sfc wind into early this evening sly/swly at 10-15 kts
with gusts near 20 kts, diminishing to less than 10 kts into Monday
morning. Wly/swly wind Monday afternoon generally 8-12 kts. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Dry conditions will persist into next weekend.
Though daytime minimum humidity will fall to less than 10 percent
this week, 20-foot winds will mostly be terrain driven at less than
15 mph. However, some periodic gustiness is likely during the
afternoon hours due to strong daytime heating.

&&

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

&&

$$

DISCUSSION...Francis
AVIATION...Carpenter
FIRE WEATHER...Carpenter

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