Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 120416

Area Forecast Discussion
National Weather Service Tucson AZ
916 PM MST Thu Jan 11 2018

.SYNOPSIS...Expect dry conditions into the middle of next week. A
warming trend will occur into this weekend, with near record
temperatures from Tucson westward Saturday. Unseasonably warm
daytime temperatures will continue next week.


.DISCUSSION...The 00Z KTWC sounding is showing boundary layer
drying in the dry northwesterly flow behind the last storm as
expected. Some surface dew point trends are actually a couple of
degrees lower than originally forecast, with the latest HRRR
continuing that trend through the early morning hours. Compared to
24 hours ago, we`ve seen them drop 6 to 12 degrees east of
Tucson. Not a big deal, but with the clear skies and modest
diurnal wind trends we`ve blended some of the 00Z data suggesting
overnight lows a modest 1 to 3 degrees cooler than the previous

Our main forecast story is going to be the rapid return of
temperatures well above average, even approaching record highs
Saturday. Please see the climate and previous discussion below
for additional details.


.AVIATION...Valid thru 13/06Z.
Some wisps of cirrus level clouds passing through, otherwise
clear. Normal surface winds, variable in direction mainly less
than 12 kts. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Dry conditions through next Thursday. 20-foot
winds may experience occasional gusts to around 20 mph with an
easterly component Saturday into early Sunday. Otherwise, terrain
driven winds less than 15 mph will occur. Unseasonably warm
daytime temperatures will return Friday and continue into next


.CLIMATE...Tucson`s record high temperature Saturday (Jan 13) is 78
degrees, which is the only remaining day this month with a record
high temperature *not* in the 80s.


.PREV DISCUSSION...Clear to mostly clear conditions were observed
via satellite imagery across southeast Arizona early this
afternoon. Surface temperatures valid 11/21Z were running up to 13
degrees warmer (KOLS) than 24 hours ago, and highs should
generally top out 5 to 10 degrees warmer than yesterday.

Upper level ridging will continue to build in over the western CONUS
as broad troughing over the Great Plains advances eastward. A couple
of shortwaves are projected to rotate through the western periphery
of this trough into Saturday, with the second one grazing our CWA
along the AZ/NM border late Friday into Saturday morning. No precip
with this weak and dry disturbance, though some elevated easterly
winds may occur Saturday. High pressure will then continue to
amplify over the western CONUS into Sunday, with the ridge axis
finally moving onshore of the Pacific coast. As a result, a record
high temperature will be possible Saturday for Tucson, as the
current record is well within reach. Please see the climate section
below for additional information.

High pressure will progress eastward into early next week as precip-
free conditions continue into Tuesday. Then, both the 11/12Z
operational GFS/ECMWF develop a pronounced trough over the Pac NW
Tuesday afternoon. Slight differences were observed with each model
compared to their previous runs, with the general idea that the
trough axis may pass further south through the Great Basin and
therefore closer to our CWA Wednesday into Thursday. Also
interesting to note that 3 perturbations of the GFS ensemble produce
measurable rainfall over our area Wednesday night into Thursday
morning, even though the operational run remains precip-free. That
said, will chalk this information up to a one-run anomaly, and the
official forecast will remain dry through next Thursday.

After Saturday, record high temperatures for Tucson return to above
the 80 degree mark, and temperatures, though still running up to 10
degrees above normal next week, will remain at sub-record levels. Ho






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