Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 160430
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
930 PM MST Wed Nov 15 2017

.SYNOPSIS...Dry conditions will continue into next week. Expect near
record temperatures for some locations again Thursday and Friday,
then relatively cooler temperatures this weekend and early next
week. However, daytime temperatures will still be several degrees
above normal.

&&

.DISCUSSION...IR satellite imagery depicted scattered to broken
cirriform clouds moving eastward across southeast Arizona during the
past 1-2 hours. Somewhat thicker clouds were moving eastward across
southern California/northern Baja California. Expect mostly clear
skies to partly cloudy skies the rest of tonight as a few mid-level
and mainly high-level clouds continue to move across the area.

Low temperatures early Thursday morning are forecast to be a few
degrees warmer east-to-south of Tucson versus this morning, but will
be quite identical to minimum temperatures achieved this morning
from Tucson westward into western Pima County. Expect record or near-
record high temperatures for at some locales Thursday and Friday.

As of this writing, the 16/00Z is in AWIPS thru 18Z Wed., Nov. 22. A
shortwave trough is still progged to move eastward across the Great
Basin and into the central Rockies Friday and Friday night.
Thereafter, the GFS depicted yet another strengthening upper high
over the southwestern CONUS (and centered just west of northern Baja
California) Monday into Wednesday.

However, this is much different than the 15/12Z ECMWF that depicted
a shortwave trough over the Pacific Northwest early Monday. This
system is then depicted to deepen while moving southeastward into
Arizona late Monday, then continuing into central New Mexico as a
561 dm closed upper low by 12Z Tue., Nov. 21.

The day shift opted for the drier/warmer GFS scenario which was
similar to the CMC at that time. Based on the 16/00Z GFS, that seems
to be the prudent course of action. Will be curious to see the
16/00Z ECMWF and what if any changes versus the previous solution.

After the passage of the Friday/Friday night system, there appears
to be an increasing potential for fairly widespread freezing
temperatures in the eastern valleys east of Tucson especially Sunday
night/early Monday morning.

Please refer to the additional sections for further detail.

&&

.AVIATION...Valid thru 17/06Z.
A few clouds around 15k ft AGL with scattered to broken clouds above
20k ft AGL into Thursday afternoon, then decreasing clouds Thursday
evening. Surface wind variable in direction less than 12 kts into
Thursday evening. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Dry conditions into the middle of next week. Some
gusty west to northwest winds will prevail Friday afternoon east of
Tucson as a system passes north of the area. Occasionally gusty east
winds may also occur this weekend, especially east of Tucson.
Otherwise, 20-foot winds will generally be terrain driven less than
10 mph.

&&

.PREV DISCUSSION /200 PM MST/...Quite a bit of thin cloud cover
across the region this afternoon as strong onshore flow continues
across southern California into Arizona. Weak ridging remains firmly
in control though, and much like the last few days we have seen
temps shoot well above normal with most desert locales in the mid
80s as of 21Z. Upper 80s still looks like a solid bet by the time
all is said and done. Much of the same is expected on Thursday,
perhaps a degree cooler but overall no significant day to day change
expected.

A trough currently moving onshore in the Pacific Northwest will
sweep through Arizona on Friday. NAEFS and other ensemble forecast
systems suggest fairly impressive Integrated Vapor Transport values
as the system moves inland but these values diminish rapidly as one
moves into Arizona, especially southeast Arizona. At this point it
appears the trough will bring an increase in clouds, maybe some
breeziness, and possibly some precip to the highest elevation
locations of northern Arizona, but little to nothing in the way of
precip this far south. Pretty much the same old story of Fall so far
in 2017 although if nothing else it should knock temperatures back a
bit with weekend highs forecast to hit the upper 70s in the deserts.
These values are still about 6-8 degrees above climatological
normals for mid November but certainly a downward trend we haven`t
seen much of so far this month.

Weak ridging returns early next week and temperatures will creep
back into the 80s. There remains some discrepancy in the
deterministic models with respect to another trough moving into
Arizona Monday/Tuesday with some models keeping the bulk of the
ascent well north of Tucson, while others suggest better ascent and
a stronger trough. Ensembles are maintaining the idea of ridging
across the area through much of next week and at this point it`s
hard to argue against that solution. Doesn`t appear temps will
rebound all the way to the upper 80s like they did earlier this week
but above normal temps appear to be the rule through at least late
next week.

&&

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

&&

$$

Francis
PREVIOUS DISCUSSION...Leins

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