Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 182250

Area Forecast Discussion
National Weather Service Tucson AZ
350 PM MST TUE OCT 18 2016

.SYNOPSIS...Expect dry conditions with above normal daytime
temperatures through this weekend. Gusty east winds will also occur
Thursday into Friday. Thereafter, increasing moisture will lead to a
slight chance of showers mainly across the White Mountains next
Monday night into Tuesday.


.DISCUSSION...High pressure aloft extended from near the Baja
California spur eastward into the southeast CONUS this afternoon.
Meanwhile, a low amplitude and broad upper trough was across much of
the northern U.S. High pressure aloft will build over Arizona into
Thursday, and this pattern will result in clear skies or just a few
mainly cirriform clouds at times. Gusty east-to-southeast winds will
develop Thursday morning and continue into Friday due to a tight
surface pressure gradient. Less wind will occur this weekend as the
surface pressure gradient weakens.

18/12Z GFS/ECMWF/CMC were similar with depicting increasingly
southwesterly flow aloft this weekend as the upper high moves
eastward into the Gulf of Mexico, and an upper trough deepens near
the West Coast. Have noted that the GFS depicted light liquid precip
accumulations to occur southeast of Tucson Sunday followed by dry
conditions Sunday night-Mon.

However, the 18/12Z ECMWF was markedly more robust with potential
rainfall across the area Sun-Mon. After reviewing the available
gridded PoP/Weather data sets from neighboring forecast offices, have
maintained dry conditions area-wide Sunday into Monday. Based on the
available gridded PoP/Weather fields and the deterministic GFS/
ECMWF, opted to introduce a slight chance of showers mainly across
the White Mountains next Monday night-Tue. The upshot at this time
is that forecast confidence is quite low regarding precip potential
Sun-Tue, and this scenario is subject to revision with subsequent

At any rate, forecast confidence is quite high that this pattern will
translate into above normal daytime temps across southeast Arizona
into early next week.


.AVIATION...Valid through 20/00Z.
Clear skies and surface wind mostly less than 10 kts will prevail
into Wednesday afternoon. A few locales may experience gusts of 15-
20 kts early this evening and Wednesday afternoon. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...There is a slight chance of showers across the White
Mountains next Monday night and Tuesday. Otherwise, dry conditions
will prevail into early next week. Expect light and terrain driven
winds to continue Wednesday, then gusty east winds should occur
Thursday into Friday. The combination of gusty east winds and
low relative humidity may briefly create critical fire weather
conditions near the Tucson metro area 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.





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