Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 272236

Area Forecast Discussion
National Weather Service Tucson AZ
335 PM MST Sat May 27 2017

.SYNOPSIS...Dry conditions will continue through Sunday night.
Increased moisture will then bring a chance of afternoon and evening
thunderstorms mainly near the New Mexico border Monday into
Thursday. Dry conditions will return area wide next weekend. Expect
warmer than normal daytime temperatures through Tuesday followed
temperatures closer to normal during the latter part of the week.


.DISCUSSION...A highly amplified upper ridge axis this afternoon
extended from central California northward into British Columbia.
Meanwhile, a subtropical jet prevailed across southern Arizona. A
very dry regime will continue across this forecast area into Sunday.
Thus, clear skies will prevail for most sections into Sunday
afternoon. The exception may be east of Tucson where some high-based
cumuloform clouds may develop Sunday afternoon.

The various 27/12Z weather prediction models were similar with
depicting a pronounced near-surface moisture increase especially
east of Tucson Sunday night into Monday morning. This moisture
increase is attributed to a backing of the lower level winds.
Meanwhile, the models depict the development of a negatively tilted
upper trough off the southern California/northern Baja California
coasts by Monday evening.

The 27/12Z Univ. of AZ WRF-NAM and WRF-GFS were very similar with
depicting precip echoes to occur by early afternoon Monday across
the White Mountains. These echoes are then depicted to quickly move
east of this forecast area Monday afternoon. Dry conditions are
depicted to prevail Tuesday into Wednesday, at least according to
these solutions. However, have noted that the 27/12Z GFS/ECMWF/CMC
were similar with depicting measurable precip Monday afternoon/
evening (as well as Tue-Thur during the afternoon/evening hours)
to mainly occur near the New Mexico border and locales further east.

Based on these solutions, have opted to depict a slight chance of
afternoon/evening showers and thunderstorms Tuesday through Thursday
to generally occur east of a Safford to Bisbee line with dry
conditions elsewhere. Have depicted the highest precip chances
across the White Mountains each day. The GFS/ECMWF/CMC depicted the
deeper moisture to be north-to-east of this forecast Friday into
next Saturday in response to ridging aloft. Per coordination with
neighboring office`s, have maintained a slight chance of showers/
tstms to just the White Mountains Friday with dry conditions
elsewhere. Dry conditions should prevail area wide next Saturday.

A warming trend is forecast to occur Sunday into Monday followed by
no significant change in daytime temperatures Tuesday. These high
temperatures will generally average about 2-5 degrees above normal.
A few degrees of cooling is on tap Wednesday and Thursday before
warmer temperatures return next weekend.


.AVIATION...Valid thru 29/00Z.
KTUS vicinity westward SKC thru Sunday afternoon. East of KTUS clear
skies into Sunday morning, then a FEW-SCT clouds at 10k-15k ft AGL
may develop Sunday afternoon. Surface wind swly to nwly 10-20 kts
with gusts to near 25 kts diminishing this evening. The strongest
speeds will be east to south of KTUS. Surface wind variable in
direction mainly less than 12 kts later tonight and into Sunday
afternoon. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Dry conditions will prevail Sunday with afternoon
minimum relative humidity generally ranging from 5-12 percent.
Thereafter, moisture will increase especially east of Tucson Sunday
night into Monday. A series of disturbances aloft will then provide
a chance of afternoon and evening thunderstorms mainly near the New
Mexico border Monday through Thursday. A slight chance of
thunderstorms continues across the White Mountains Friday followed
by dry conditions returning area wide next weekend.






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