Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 280336

Area Forecast Discussion
National Weather Service Tucson AZ
833 PM MST Thu Oct 27 2016

.SYNOPSIS...Strong high pressure will result in dry conditions with
well above normal daytime temperatures through the weekend. A
trough through western states should bring a moderate cooling
trend next week, with temperatures falling closer to seasonal
averages by the middle of the week.


.DISCUSSION...The latest (28/03Z) satellite imagery shows broken to
overcast high clouds across much of the region attm. Expect these
high clouds to persist through the rest of tonight and Friday. Made
adjustments to the sky grids/text products earlier this evening to
reflect increased cloud cover for tonight. Otherwise, a very warm
day across the forecast area with several record highs tied or
broken. These include the TIA (high of 97), Douglas-Bisbee Airport
(high of 89) and Picacho Peak (high of 97). For more information on
the record highs, please refer to the PHXRERTWC product. Easterly
flow continues across the forecast area this evening at most
reporting sites. However, should see the flow slacken and become
terrain driven in most locations by midnight or shortly thereafter.
TIA will be the exception, with typical southeast overnight/early
morning winds. For more information on the latter periods of the
forecast, please refer to the prev discussion section below.


.AVIATION...Valid through 29/00Z.
VFR with BKN-OVC cirrus level clouds through the period and FEW-SCT
clouds at 8-12k ft agl after 28/17Z. Surface wind generally ely/sely
at 7-14 knots with occasional gusts to near 18 knots, diminishing
below 10 knots after 28/06Z. Aviation discussion not updated for TAF


.FIRE WEATHER...Dry conditions will prevail into early next week.
Expect occasionally gusty east to southeast winds through this
evening. 20-foot winds will then be terrain driven generally 15 mph
or less into the middle to latter part of next week. A low pressure
system will begin to move into the Desert Southwest, bringing a
chance of showers mainly to the White Mountains late Tuesday into


.PREV DISCUSSION...Water vapor imagery shows an expansive ridge that
is centered over southern Sonora Mexico, with the ridge axis
extending north into the entire western half of the nation.
Meanwhile, a Pacific system is currently making its way toward the
Pacific Northwest. Also, Tropical Storm Seymour, which is generally
about 850 miles west of the southern tip of the Baja Peninsula is
expected to weaken to a Remnant low by Friday. Southwest flow on the
western flank of the ridge with continue to pull mostly high level
moisture from the eastern Pacific northward today.

Current IR satellite imagery shows plenty of mid and high level
cloudiness across the eastern Pacific waters, much of California and
Arizona. For Arizona, most of this cloudiness is thin high cirrus
clouds, so this cloud cover should not hinder our chances of seeing
afternoon high temperatures in the upper 90s today, which will
easily break record temps, especially at Tucson where the record for
today is 94 degrees, set back in 1937.

Models indicate that as the ridge moves east Friday, a shortwave
trough and associated vort max will move inland across central
California, with weaker disturbances even farther south. This system
will eject northeast into the central and northern Rockies late
Friday into Saturday. As a result, expect some moisture to be
transported north and east into parts of California, Nevada and
mainly northern parts of Arizona and even lingering through late
Saturday/early Sunday. Since most of this moisture will be to our
north and northwest as this system passes by, only included single
digit POPs in the forecast through that time.

Another couple of shortwaves expected behind this first one, with
the next one moving across the Great Basin Sunday and then another
developing farther south over southern California on Tuesday before
moving across Arizona Wednesday into Thursday. Some significant
differences with timing as the GFS is much quicker in kicking the
system northeast than the ECMWF, which has it lingering over
southeast Arizona and southwest New Mexico through much of the day
on Thursday. That said, associated moisture is just to our east
based on the ECMWF solution, whereas the GFS is significantly drier.
For now I just show isolated to scattered showers beginning late
Tuesday into Wednesday with the threat tapering off thereafter. May
have to revisit this forecast if the model trends end up
pointing to a solution more in line with the slower ECMWF.

For Tucson, high temperatures will range from 10 to 12 degs above
normal through Sunday, then 4 to 5 degs above normal Monday and
Tuesday. Thereafter, highs will hover within a degree or two either
side of normal. Low temps will range from 10 to 15 degs above normal
Friday through Sunday mornings, then around 8 to 10 degs above
normal for Monday and Tuesday and 3 to 5 degs above normal
Wednesday. Near normal lows expected for Thursday.





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