Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus65 ktwc 212232 
afdtwc

Area forecast discussion
National Weather Service Tucson Arizona
330 PM MST Mon Oct 21 2019

Synopsis...dry conditions into early next week. Expect warmer than
normal high temperatures Tuesday through Thursday, then cooler
temperatures Friday especially east of Tucson. Warmer temperatures
will return this weekend. Widespread freezing temperatures or a hard
freeze may occur in the eastern valleys Friday night.

&&

Discussion...clear skies prevail across Southeast Arizona this
afternoon except for a few thin cirriform clouds moving
southeastward mainly across the White Mountains. Surface winds at
mid-afternoon were generally from the northwest at 5-15 mph,
although some gusts near 20 mph were occurring near Safford. Expect
winds to diminish early this evening with the loss of daytime
heating, and clear skies should prevail tonight.

Various 21/12z numerical weather prediction models continue to
depict strong high pressure aloft will remain centered just west of
the central/northern California coast Tuesday into Thursday. The
position of the upper high will translate into a very dry northwest
flow aloft regime resulting in continued clear skies, or perhaps
some passing thin cirriform clouds at times.

The mid/upper flow by Friday remains progged to become increasingly
northerly in response to strong high pressure aloft becoming
centered generally over Southern California. This pattern should
promote a Bone-dry near-surface environment, particularly by Friday
night and continuing into early Saturday.

As such, the potential exists for widespread freezing temperatures,
and perhaps a hard freeze for some locales at least for a few hours
across the eastern valleys east of Tucson. Have noted a fairly wide
range of progged temperatures for Friday night/early Saturday
morning, with the GFS/nbm markedly warmer versus the European model (ecmwf)
temperatures. This official forecast issuance depicts only very
minor temperature adjustments versus the midnight shift forecast
issuance, and forecast lows for early Saturday morning remain
trended much closer to the European model (ecmwf) temps given the expectation of
clear skies, light winds, and a Bone-dry surface regime.

The upper high is then progged to be suppressed south of this
forecast area Saturday as an upper trough deepens over the Pacific
northwest/northern rockies region. The 21/12z GFS/gefs and European model (ecmwf)/
ecens have trended toward a less amplified upper trough and
definitely away from a digging closed upper low scenario over the
Great Basin Sunday into Monday versus previous solutions. The European model (ecmwf)
was somewhat deeper with upper trough by next Monday over the
intermountain west versus the GFS, and the European model (ecmwf) suggests a few
showers possible next Monday across the White Mountains. However,
per coordination with neighboring wfo's and a 50/50 GFS/European model (ecmwf) blend,
have opted to maintain precip-free conditions area-wide early next
week.

High temps Tuesday into Thursday will generally be a few to several
degrees above normal, with the warmest temperatures from Tucson
westward into the western deserts. Cooler temperatures will then
occur Friday from Tucson westward, but much cooler temperatures on
Friday east of Tucson. Warmer temps are on tap area-wide this
weekend.

&&

Aviation...valid through 22/00z.
Sky clear conditions through the period. Surface wind becoming variable in
direction under 10 kts areawide this evening and continuing into
Tuesday afternoon. Aviation discussion not updated for taf
amendments.

&&

Fire weather...dry weather is expected into early next week. Expect
above normal temperatures Tuesday through Thursday with temperatures
generally trending closer to normal Friday into next Monday. A dry
regime will result in daytime humidity minimums dropping into the
high single digits to the lower teens for many locations into this
weekend. Occasionally gusty east winds should occur Friday, and some
gusty southwest winds during the afternoon hours Sunday and Monday.
20-foot winds will be terrain driven and mainly less than 15 mph at
other times.

&&

Twc watches/warnings/advisories...none.

&&

$$

National Weather Service Glossary of Abbreviations