Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 200442

Area Forecast Discussion
National Weather Service Tucson AZ
941 PM MST WED OCT 19 2016

.SYNOPSIS...Dry conditions with above normal daytime temperatures
will continue through Saturday. Gusty east to southeast winds will
also prevail Thursday into Friday morning. Increasing moisture will
then bring a slight chance to much of the area early next week.


.DISCUSSION...current forecast looked on track, so no updates
necessary this evening. Refer to the previous discussion for


.AVIATION...Valid through 21/06Z.
Clear skies will prevail across much of southeast Arizona through
Thursday afternoon, although a FEW clouds around 8k-12k ft AGL may
occur east of KTUS Thursday. Surface wind generally less than 10 kts
tonight, then surface wind ely/sely 10-20 kts with gusts to near 30
kts Wednesday. The strongest speeds will likely be in the vicinity
of KTUS. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Dry conditions will continue through Saturday.
Increasing moisture will then provide a slight chance of showers
south of Tucson Sunday, then a slight chance of showers across much
of southeast Arizona Monday into Tuesday. Dry conditions will return
next Wednesday.

Meanwhile, expect gusty east to southeast winds Thursday into Friday
morning. The combination of these strong winds and low relative
humidity may briefly create critical fire weather conditions near
the Tucson metro area, or central Fire Weather Zone 151, late
Thursday morning into Thursday afternoon. However, widespread
critical fire weather conditions are not forecast to occur at this
time. Normal diurnal wind trends will return this weekend.


.PREV DISCUSSION...Strong high pressure aloft was centered west of
northern Baja California near 28N/125W and a ridge axis extended
northward into the Pacific Northwest this afternoon. The very dry
generally wly flow aloft pattern will maintain clear skies tonight.
The upper high will expand eastward across the southwestern CONUS

Meanwhile, a tight surface pressure gradient will produce gusty east-
to-southeast winds Thursday. Various high resolution models suggest
that the onset of these gusty winds will occur across far eastern
sections around daybreak Thursday, then spread westward Thursday
morning. The best guess for the onset of these gusty east-to-
southeast winds for the Tucson metro area will be after sunrise
Thursday, or around 15Z-17Z Thursday or such. Perhaps a slight
moderation in speeds late Thursday afternoon, then winds should
increase again Thursday night and remain gusty Friday morning. Winds
should then diminish rapidly Friday afternoon as the surface
gradient weakens.

Thereafter, the 19/12Z GFS/ECMWF/CMC remained similar with their
respective previous solutions with depicting the upper high to
become positioned over Texas Saturday. The flow aloft is progged to
become more swly Saturday, then somewhat deeper moisture is depicted
to move northeastward across the area Sunday.

For now, have discounted some solutions that attempted to produce
light rain amounts south-to-southeast of Tucson as early as Saturday
afternoon/evening. However, PoPs were raised Sunday to introduce a
slight chance of showers south-to-southeast of Tucson. The upper
trough is progged to deepen west of the area Monday. These solutions
were markedly more aggressive with precip chances versus solutions
from 24 hours ago. At any rate, additional PoP increases were made,
and a slight chance of showers now exists area-wide Monday.

The flow aloft is depicted to become increasingly westerly Tuesday.
This pattern should translate into a drier regime, especially by
next Wednesday. There appears to be enough residual moisture to
justify a slight chance of showers mainly from Tucson eastward next
Tuesday. Have then opted for precip-free conditions to return area-
wide next Tuesday night into Wednesday.

Expect above normal daytime temperatures to continue thru this
weekend, then high temps are forecast to moderate closer to seasonal
normals Tue-Wed.





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