Scientific Forecaster Discussion
fxus65 ktwc 192210
Area forecast discussion
National Weather Service Tucson Arizona
310 PM MST sun Nov 19 2017
Synopsis...dry conditions will continue into early next week.
Widespread freezing temperatures for eastern valleys tonight, then
daytime temperatures rebound quickly to near record or record
levels by Thanksgiving.
Discussion...strong high pressure aloft centered west of the Baja
California spur near 25n/120w and ridge axis extended northward into
northern California this afternoon. Meanwhile, clear skies were
across Southeast Arizona with some cirriform clouds moving eastward
and over the ridge axis into Southern California. Surface winds had
generally diminished to under 10 mph most sections at this time.
Clear skies or perhaps a few thin cirriform clouds will prevail
tonight. Any clouds that move into the area are not expected to
hinder nearly ideal cooling conditions, however. Light winds will
also prevail across much of Southeast Arizona tonight, although
occasionally gusty east to southeast winds are expected near the
Tucson Metro area.
For locales east of Tucson tonight, the combination of clear skies,
light winds, and a very dry regime will allow for fairly widespread
freezing temperatures to occur. Thus, a freeze warning remains in
effect from 1 am to 8 am MST Monday for the upper San Pedro River
Valley, eastern Cochise County below 5000 feet, and the upper Gila
River valley. Please refer to AWIPS product phxnpwtwc /WMO header
wwus75 ktwc/ for detail.
The ridge axis will amplify over Southern California into the
Great Basin area Monday. However, the 19/12z GFS/ECMWF/CMC suggest
that mainly cirriform clouds will thicken across this forecast
area, especially Monday afternoon into Monday evening. Mostly clear
skies to partly cloudy skies will prevail late Monday night into
Thereafter, Southeast Arizona will likely be hard-pressed for a
cloud of significance Wednesday into next weekend as the center of
strong high pressure aloft is progged to remain generally just south
of this forecast area. The main impact from this high pressure
system will translate into a strong warming trend Wednesday into
Thanksgiving day, with forecast highs Thursday to range about 12 to
nearly 20 degrees above normal.
The most recently issued official forecast then depicts a few
degrees of daily cooling to occur Friday into next Sunday. However,
would not be surprised to see high temps Friday and Saturday to
actually be quite similar to temps that occur on Thursday, or
Thanksgiving day. Perhaps the same may also apply to next Sunday as
well. The upshot is that no cooling of significance appears to be on
tap until after next Sunday, at least at this time.
Aviation...valid thru 21/00z.
Sky clear into this evening with scattered clouds above 20k ft above ground level overnight
into Monday morning. Scattered-broken clouds above 20k ft above ground level Monday
afternoon. Surface wind generally Ely/southeasterly at 8-12 kts into this
evening, then variable in direction less than 10 kts late tonight
into Monday. Surface wind Monday afternoon westerly/northwesterly but less than 10
kts. Aviation discussion not updated for taf amendments.
Fire weather...dry conditions into next weekend. Well above normal
temperatures return to the region Thanksgiving into next weekend. 20-
foot winds may be gusty from the east this evening and again
Wednesday into Thursday. Wind will be terrain driven at mainly less
than 15 mph at other times.
freeze warning from 1 am to 8 am MST Monday for azz507>509.