Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 220410

Area Forecast Discussion
National Weather Service Tucson AZ
910 PM MST Sat Oct 21 2017

.SYNOPSIS...Dry conditions to prevail during the upcoming week.
Warmer daytime temperatures returning Sunday into Monday, with
record or near record high temperatures Monday into Wednesday.
Expect a cooling trend next Friday and Saturday, although above
normal temperatures will likely continue.


.DISCUSSION...Clear skies prevail across southeast Arizona at this
time. Surface winds valid 9 pm MST were generally from the west to
northwest at less than 10 mph. Expect clear skies the rest of
tonight as surface winds shift to a light easterly component. Some
locales in the coldest valleys east of Tucson may briefly experience
freezing temperatures around daybreak Sunday. However, widespread
freezing temperatures are not expected to occur.

The light easterly (generally downslope) near-surface wind
component, sunny skies, and rising heights/thicknesses due to
building high pressure, will translate into warmer temperatures on
Sunday. High temperatures Sunday are forecast to be about 3-8
degrees warmer area-wide versus this afternoon, with the stronger
warming to occur from Tucson westward into the western deserts.

There are no updates warranted at this time. Please refer to the
additional sections for further detail.


.AVIATION...Valid thru 23/06Z.
Clear skies into Sunday evening. Surface wind becoming sely to nely
5-15 kts most sections of southeast Arizona later tonight and
continuing into Sunday evening. Aviation discussion not updated for
TAF amendments.


.FIRE WEATHER...Dry conditions to continue into next Saturday. A
generally light east wind component will prevail Sunday into
Wednesday, although some 20-foot wind gusts in excess of 20 mph will
occur at times. Expect normal diurnal wind trends Thursday into next
Saturday. However, some weather models suggest that gusty northwest
winds may occur Friday, especially east of Tucson and across the
Upper Gila River Valley including Safford.


.PREV DISCUSSION /156 PM MST/...For the first time in a few weeks,
it actually feels "normal" outside as cooler air has settled into
the region. Daytime highs so far (as of 20Z) have only been in the
upper 70s across the deserts and with a few more hours of heating
still to be realized, highs should end up right around normal (low
80s) for late October. For the rest of the evening and overnight
hours, expecting mostly clear skies to prevail. Dewpoints have
started to retreat as expected and should continue to fall through
the rest of the night, allowing temperatures to fall several degrees
lower than what was seen this morning. Low 50s/upper 40s will be
common Sunday morning with some of the more protected areas in
Cochise/Graham Co`s likely seeing upper 30s Sunday morning.

The reprieve from the heat will be short lived as ridging will
return Sunday and will last through most of the upcoming week. Near
record temps are all but certain by mid week as mid 90s will be
common across the Tucson area and points west. Could even see some
spots across western Pima County flirt with the century mark by mid
week. A late week pattern change looks to be in the cards by Friday
with a trough forecast to dip through the Four Corners into New
Mexico on Friday. This should result in somewhat cooler temperatures
to close out the week into the weekend along with a period of gusty
winds coincident with the arrival of much lower dewpoints. Naturally
there are some slight differences between the operational GFS and
ECMWF but their respective ensembles (along with the NAEFS) are all
indicative of troughing across the area late in the week.






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