Scientific Forecaster Discussion
fxus65 ktwc 222152
Area forecast discussion
National Weather Service Tucson Arizona
252 PM MST Tue Oct 22 2019
Synopsis...dry conditions into early next week. Expect above
average high temperatures through Thursday, then cooler
temperatures Friday, especially east of Tucson. Warmer
temperatures will return this weekend. Our first widespread
freezing temperatures may occur in colder eastern valleys Friday
night into Saturday morning.
Discussion...the position of a strong and high amplitude eastern
Pacific Ridge will dominate our weather the rest of the month.
With it's proximity to the coast, we are currently on the eastern
flank of the ridge with heights and thicknesses supporting
afternoon highs several degrees above average through Thursday.
Add in a strong Bermuda high, and you have a lot of room for broad
and deep troughiness over much of the rest of the country. A
strong system digging into New Mexico Thursday and Thursday night
will bring good cold air advection from British Columbia southward
into especially eastern portions of the state Friday and Friday
night. Gusty winds should keep temperatures up Thursday night into
Friday morning, with strong easterly winds Friday. The gradient
will relax quite a bit Friday night into Saturday, with a strong
chance of normal diurnal trends by sunrise Saturday morning.
Combined with clear skies and low dew points, we should have some
locations in Cochise County drop to near or a little below
The ridge will retreat a little further off coast over the weekend
with a broad trough over the region, but the key will be how far.
Gefs and European model (ecmwf) deterministics disagree on the progression of the
pattern early next week with a slower and deeper European model (ecmwf). Ensemble
means of each help a little with the operational GFS near the warm
end of the runs. The current nbm blend looks fine as it comes in
between these resolutions, however we might end up needing a touch
more depth offered by the European model (ecmwf) ensemble mean judging by the
persistent depth of weekly height anomalies the first half of next
week. The bottom line is limited moister this far south, but
another round of gusty winds and cooler air to start the new work
week. As the new mean trough position slowly shifts eastward,
we'll pick up the front foot of the ridge again the second half of
Aviation...valid through 24/00z.
Clear skies and surface wind variable in direction mainly under 12
kts into Wednesday afternoon. Aviation discussion not updated for
Fire weather...dry conditions into early next week. Afternoon
minimum relative humidity in valley locations generally 8-15 percent
through Thursday, then mainly in the teens to lower 20 percent range
Friday into next Tuesday. Expect gusty east winds developing as
early as Thursday evening, but more likely early Friday morning into
Saturday morning. 20-foot winds will be terrain driven and mainly
less than 15 mph at other times.
Climate...there are early indications that a few locations across
Cochise County may approach record lows Saturday morning, October
26. Below is a select location listing of the daily record lows
for October 26th.
Bisbee-Douglas Airport 33 /1997
Sierra Vista 32 /1905
Tombstone 32 /1929
Willcox 21 /1921