Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 161605

Area Forecast Discussion
National Weather Service Tucson AZ
905 AM MST Mon Oct 16 2017

.SYNOPSIS...Strong high pressure will maintain dry conditions with
unseasonably warm temperatures through Wednesday. A disturbance may
bring a few showers Thursday, then dry conditions will prevail
Friday into early next week. Another system will bring some minor
cooling Saturday, then very warm temperatures return by early next
week as high pressure builds over the area.


.DISCUSSION...Clear skies and locally gusty east to southeast winds
prevail across southeast Arizona this morning. Tucson International
Airport recorded a wind gust to 31 mph shortly before 9 am MST.
Meanwhile, a dry surface regime exists with lower elevation dew
points valid 9 am MST ranging from the upper 20s-mid 30s. 16/12Z
KTWC sounding total precip water value of 0.50 inch was virtually
unchanged versus 24 hours ago.

The profile exhibited a fairly modest easterly wind component in the
surface-700 mb layer, with the highest observed speed earlier this
morning only around 20 kts. 16/12Z upper air plots depicted a 592 dm
high centered just south of this forecast area over northern Sonora
Mexico, and a ridge axis extended northwestward into northern
California. Light to moderate wly/nwly flow prevailed above 700 mb.

Occasionally gusty east to southeast winds will occur today and then
begin to diminish tonight and especially Tuesday morning as a tight
surface pressure gradient loosens across the area. Otherwise, strong
high pressure aloft will maintain clear skies today before a few
cirriform clouds move across the area tonight into Tuesday. High
temperatures this afternoon will generally average just a few
degrees lower versus Sunday, but will remain 3-10 degrees above
normal depending upon location.

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


.AVIATION...Valid thru 17/18Z.
Clear skies into this afternoon followed by a few to scattered
clouds above 20k ft AGL tonight into Tuesday morning. Surface wind
today generally ely/sely 5-15 kts with gusts near 30 kts. The
strongest speeds will be in vicinity of KTUS. Surface wind nly to
ely less than 12 kts tonight into early Tuesday morning. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...A few mainly mountain showers will occur Thursday.
Otherwise, dry conditions will prevail into early next week. Gusty
east to southeast winds will diminish early Tuesday followed by
normal diurnal wind trends during the latter part of the week.


.PREV DISCUSSION /200 AM MST/...Dry weather remains in place across
the region this morning as the atmosphere remains quite dry for mid
October. The cold front that dipped through the area on Sunday
accomplished just about what was expected...little to no cooling
west of Tucson along breezy easterly winds area-wide. Wind speeds
remain elevated this morning with several locations still seeing
winds above 10kts as of 09Z. Not surprisingly these locations
(including KTUS) have been slow to cool down with temps still in the
mid 70s. Those area that are a bit more protected and where winds
have calmed have already fallen well into the mid 60s.

Winds will remain elevated today and to a lesser extent tomorrow as
the relatively tight pressure gradient remains in place across
eastern Arizona. A return to more typical diurnal wind speeds and
directions is more than likely going to have to wait til late
Tuesday or early Wednesday at the earliest. Temps during this period
will be very similar to those seen the past few days with highs in
the mid 90s in the lower elevations and in the 80s in the valleys
east of Tucson.

Not a dramatic departure from the inherited forecast, but the latest
runs of the deterministic GFS and ECMWF are still depicting a weak
shortwave trough moving into the area Wednesday with increased
clouds and even a chance of precip in some spots on Thursday. Latest
available NBM guidance suggests slight chances of precip in the
White Mountains on Thursday, trailing off to lower single digit PoP
values around Tucson and the surrounding deserts. Made slight upward
adjustments to the PoP forecast for this time period but there will
be quite a bit of lower level dry air in place that may preclude
much in the way of measurable precip across the area, especially in
the lower elevations.

Still looks like a slight cool-down will come via another weak
trough in the Friday night/Saturday timeframe. Given how warm it has
been lately, the cool-down may seem noteworthy but in reality the
trough will only knock us back to where we should be for mid/late
October with highs in the mid/upper 80s. High pressure will return
this weekend and the cool-down will be short-lived as highs should
approach the 90 degree mark by this time next week.






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