FXUS65 KTWC 271630

Area Forecast Discussion
National Weather Service Tucson AZ
930 AM MST Tue Oct 27 2020

.SYNOPSIS...A deep winter storm will maintain much colder than
normal conditions through Wednesday with areas of overnight
freezing temperatures. Scattered showers, snow down to around 4000
ft, will continue east of Willcox today then diminish quickly
this evening with skies clearing. Dry and warmer weather will
return by the end of the week and continue through the weekend.


.DISCUSSION...Many places this morning getting down to the freezing
mark or below within the Freeze/Hard Freeze warning areas, including
KTUS with 32 degrees. With things starting to warm up, we expired
the Freeze and Hard Freeze warnings this morning at 8 AM. A few
light rain and snow showers continue across areas east of Tucson,
but mainly east of the AZ/NM line. The upper low remains centered to
our south and east with plenty of cloud cover wrapping around on the
eastern periphery, and clear skies west of Tucson where drier air is
in place. As the low moves out through the day today, any lingering
showers and cloud cover will clear and set the stage for another
chilly night. The forecast remains on track for now with tweaks
possible with the afternoon package. No updates. Please see the
remaining sections for additional details.


.AVIATION...Valid through 28/18Z.
ISOLD-SCT SHRA/SHSN east of KTUS this morning lasting into the
afternoon. SCT-BKN clouds 5k-10k ft MSL, gradually dissipating
during the afternoon and evening hours. SFC winds remain less than
12 kts through the period, favoring a N-E direction during the
afternoon. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Chances for rain and snow showers will continue
across Cochise, Graham and Greenlee Counties, diminishing later this
afternoon. Elsewhere, much drier air has spread across the region
behind the passing cold front. Temperatures have plummeted roughly
20 degrees below normal for late October. However, the cold air
doesn`t linger very long as high temperatures quickly ramp back up
near or above normal by Friday and into the weekend. 20-foot winds
will be less than 15 mph Tuesday and Wednesday becoming easterly
Thursday into the weekend.


.PREV DISCUSSION...The upper low settled over southern AZ overnight
just a bit further west that anticipated 24hrs ago resulting in more
cloud cover east of Benson than forecast. This has resulted in
temperatures in the Sulphur Springs valley and points east to not
drop as much as anticipated. I therefore made some temperature
adjustments that resulted in freeze headline changes for that area,
basically more areas out of the Hard Freeze warning. Further west
the temperatures are dropping as expected with several areas south
and east of Tucson already below freezing and a few locations in the
metro area within a degree or two of freezing at 2 am.

This further westward shift of the storm also means that shower
activity will continue east of a Dudleyville, Texas Canyon to
Douglas line for a good part of the day with the snow level as low
as 4,000 ft although amounts will be very light. Could even see a
flurry as far west as Mt Lemmon for a brief period early this
morning. This afternoon will be rather cold for late October and 20-
25 degrees colder than normal. The forecast high of 59 in Tucson
would be the first sub 60 degree high since March 27th.
Even if we manage 60 or better, the last high in the 60s was April
11th. Chilly indeed.

The storm then shifts east tonight taking the precipitation and
clouds with it leaving behind a cold and dry air mass. Winds will be
light as well which should allow temperatures to drop during the
overnight hours with fairly widespread sub-freezing temps east and
south of Tucson. Even though we missed the low temps this morning
east of Benson, we should drop into the hard freeze category in
those coldest areas tomorrow morning. Still looking at the potential
for the record coldest October low temperature for Willcox tomorrow

Beyond Wednesday, heights rapidly rise for a quick rise in high
temperatures. Thursday will be right about normal for high temps (81
at Tucson) then we rise into mid and upper 80s Friday through the
weekend. The ridge doesn`t look quite as intense over our area as it
has the last couple of days so we may be able to avoid 90 degree
highs late in the weekend into next week although it will be close.



Hard Freeze Warning from 9 PM this evening to 8 AM MST Wednesday
for AZZ503-507>509.

Freeze Warning from 9 PM this evening to 8 AM MST Wednesday for



Fire Weather....Howlett

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NWS TWC Office Area Forecast Discussion