Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 281040
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
340 AM MST Mon Feb 27 2017

.SYNOPSIS...There is a good chance of valley rain and mountain snow
today, with the greatest coverage north of Tucson. Any precipitation
will end by this evening followed by dry conditions into early next
week. Gusty southwest to northwest winds will occur today before
markedly less wind occurs Wednesday. Expect much warmer daytime
temperatures by Thursday, then well above normal high temperatures
will continue Friday into early next week.

&&

.DISCUSSION...Dry conditions prevail across much of southeast
Arizona at this time. The exception was well west of Tucson, or
across far western Pima County, where scattered showers were
ongoing. A broad upper trough resides over the western CONUS early
this morning, and the mid/upper level trough axis extended from
western Montana southwestward into southern California. IR satellite
imagery generally depicted the location of this trough axis, with
colder-topped clouds east of the axis, or across much of Utah and
Arizona. Generally clear skies prevailed west of the trough axis.

The various 27/00Z models were in general agreement with depicting
the best chance of valley rain and mountain snow to occur later
today north of Tucson, and considerably less coverage of showers
should occur south of Tucson. The aforementioned mid/upper level
trough axis is progged to move eastward into western Arizona by late
morning, then advance rapidly eastward into New Mexico by this
evening. The deeper moisture will be shunted rapidly east of this
forecast area as well.

For this forecast issuance, have maintained a good chance of valley
rain/mountain snow showers north of Tucson this afternoon, and just
a slight chance of showers across southern sections. Have opted to
remove the Catalina/Rincon Mountains from the Winter Weather
Advisory. Thus, the Winter Storm Warning remains in effect until 5
PM MST this afternoon for the White Mountains above 6500 feet. The
Winter Weather Advisory remains in effect until 5 PM MST this
afternoon for the Galiuro and Pinaleno Mountains, including Mount
Graham southwest of Safford.

Gusty southwest to west winds will prevail across much of the area
this morning, then winds should turn to a more northwesterly
component this afternoon before diminishing this evening. Am
somewhat concerned about the potential for localized blowing dust
that may restrict visibilities along Interstate 10 in northern
Cochise County this afternoon.

Otherwise, decreasing clouds will occur this evening, then clear
skies or mostly clear skies will prevail late tonight. Generally
northwesterly flow aloft Wednesday into Thursday will likely produce
clear skies. The 27/00Z GFS/ECMWF/CMC were similar versus previous
solutions in developing a weak upper trough south of the area
Friday. A few cirriform clouds may encroach upon far southern
sections Friday, but generally clear skies should continue.

Thereafter, westerly flow aloft Saturday will transition into
southwesterly flow aloft Sunday into Monday. Expect precip-free
conditions to continue this weekend and early next week. Although
more widespread cirriform clouds should occur versus Friday, appears
at this time that these high-level clouds should be thin enough to
produce just mostly clear skies.

High temperatures today will be a few degrees below normal followed
by a few degrees of warming Wednesday. Expect markedly warmer
temperatures Thursday into Friday, then daytime temps Saturday into
next Monday should average about 10 degrees or so above seasonal
normals.

&&

.AVIATION...Valid through 01/12Z.
Scattered to numerous -SHRA and mountain SHSN this morning, with the
greatest coverage north of KTUS. Precipitation will end by this
evening. Otherwise, cloud decks generally 6k-12k ft AGL this morning
followed by decreasing clouds this afternoon. Clear skies to SCT
clouds 10k-15k ft AGL this evening into Wednesday morning. Surface
wind through this afternoon swly to nwly 10-22 kts with gusts to
near 35 kts. The strongest speeds will be east of KTUS and
especially near the New Mexico border. Surface wind variable in
direction less than 12 kts tonight into Wednesday morning. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Scattered to numerous valley rain and mountain snow
showers today, with the greatest coverage north of Tucson. Dry
conditions will then prevail this evening into early next week.
Expect gusty southwest to west winds today but given the available
moisture, critical fire weather thresholds will not occur. A
generally light east wind regime will then prevail Wednesday through
Friday, although 20-foot winds will experience occasional gusts to
near 20 mph. Normal diurnal wind trends are on tap this weekend into
early next week.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
    Winter Storm Warning until 5 PM MST this afternoon for AZZ510
      above 6500 feet.

    Winter Weather Advisory until 5 PM MST this afternoon for
      AZZ511 above 6500 feet.

&&

$$

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