FXUS65 KTWC 122235
Area Forecast Discussion
National Weather Service Tucson AZ
335 PM MST Thu Dec 12 2019
.SYNOPSIS...Dry conditions and a warming trend will prevail through
Saturday. A weather system moving north of the area may bring
isolated showers to the White Mountains Sunday into Sunday evening.
Then, expect dry conditions but cooler temperatures early next week.
Slightly warmer temperatures will return next Tuesday and Wednesday.
.DISCUSSION...Satellite imagery early this afternoon
depicted scattered to broken cirrus streaming into Arizona on
northwest flow aloft. This moisture was on the eastern periphery of
a broad area of high pressure located well west of northern Baja
California. Do expect this cirrus to thin this evening and overnight
with clear or mostly clear skies by daybreak Friday. The upper high
is then progged to continue building eastward into Saturday. Any
clouds which do develop during this period will mainly be thin
The aforementioned ridge will flatten out Saturday with robust zonal
flow setting up over the state. This will occur in advance of a
shortwave trough which will move from the Pac NW through the Great
Basin on Sunday. The 12/12Z GFS/ECMWF and their ensembles are
consistent with the trough axis passing through the Four Corners
region Sunday into Sunday evening. Though the majority of moisture
will remain north of this forecast area, there could be enough
bagginess in the trough for some precip to develop across the White
Mountains. Therefore, the forecast calls for isolated to scattered
rain and snow showers across the White Mountains Sunday through
Sunday evening. With the lack of moisture, liquid QPFs will be
limited to a trace to perhaps a few hundredths of an inch likely
confined to the highest peaks. Additionally, some westerly to
northwesterly breezes may also occur Sunday afternoon particularly
east of Tucson.
Dry conditions will return area-wide late Sunday night into Monday
under northwest flow aloft. A ridge will then build over the region
Tuesday with the ridge axis passing overhead Wednesday. It should be
noted that the ECMWF solution depicts a more amplified ridge than
the GFS. Model solutions then develop an upper trough off the coast
of California, though there remain considerable differences between
the GFS and ECMWF regarding its depth and progression late next
week. Early indications are that this trough will eventually pass
through the state in some capacity. For now, have introduced slight
chance category PoPs at day 7 which by and large match up well with
our neighboring WFOs.
Warmer than normal temperatures occur Friday and Saturday, with a
cooling trend to near normal on Sunday. Below normal
temperatures then prevail Monday through Thursday next week.
.AVIATION...Valid through 14/00Z.
BKN-OVC clouds AOA 20k ft MSL thru 13/14z, then FEW-SCT clouds AOA
25k ft MSL thru the end of forecast period. Surface wind variable in
direction and less than 12 kts. Aviation discussion not updated for
.FIRE WEATHER...Dry and warmer conditions are expected through
Saturday. A weather system moving across the Four Corners region
will bring some breezy winds Sunday, especially east of Tucson. This
system may also result in isolated rain and snow showers in the
White Mountains. Dry conditions areawide early next week, but with
cooler temperatures. Locally gusty east winds may occur Tuesday and
Wednesday of next week.
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