Area Forecast Discussion
Issued by NWS Tucson, AZ
FXUS65 KTWC 240257
Area Forecast Discussion
National Weather Service Tucson AZ
757 PM MST Sun Apr 22 2017
.SYNOPSIS...Continued dry conditions with warmer than normal
daytime temperatures and gusty afternoon winds through Wednesday. A
few showers may occur across the White Mountains Thursday. However,
a stronger storm system may then bring strong gusty winds Friday
into Saturday, as well as a slight chance of showers as far west as
.DISCUSSION...Critical fire weather conditions will continue to
be the main concern the next few days. The gusty winds, above normal
daytime temperatures, and extremely low afternoon relative
humidities values have prompted the issuance of a Red Flag Warning
for Monday, and a Fire Weather Watch for Tuesday for portions of
southeast Arizona. Latest models continued to support the current
forecast. Please refer to the additional sections, especially the
previous discussion, for more details.
.AVIATION...Valid through 25/06Z.
Expect SKC to SCT clouds above 20k ft AGL into Monday evening.
Surface wind 8-18 kts with gusts to 25 kts diminishing to less than
10 kts tonight then continuing into early Monday morning. Surface
wind after 15Z-23Z Monday swly 12-25 kts with gusts to near 35 kts.
Aviation discussion not updated for TAF amendments.
.FIRE WEATHER...A Red Flag Warning is in effect from 11 AM to 7 PM
MST Monday for the southeastern half of fire weather zone 151, and
for most of fire weather zone 152. The combination of strong and
gusty southwest winds, relative humidity in the single digits to
lower teens, and a high fire danger will create critical fire
A Fire Weather Watch is in effect from late Tuesday morning through
Tuesday evening for the southeastern half of fire weather zone 152.
The combination of strong and gusty winds, low relative humidity and
a high fire danger may create critical fire weather conditions.
Critical fire weather conditions may also return Friday to a fairly
large portion of southeast Arizona. Field crews are strongly
encouraged to monitor subsequent forecasts for additional Fire
Weather Watch and/or Red Flag Warning issuances.
Otherwise, a few showers may occur across the White Mountains
Thursday. There is a chance of showers across the White Mountains
Friday, then a slight chance of showers as far west as Tucson Friday
night into Saturday. Dry conditions are expected to occur area-wide
Saturday night into next Sunday.
.PREV DISCUSSION...The upper level pattern Monday into Wednesday
will generally be characterized with a strong high pressure system
over the eastern Pacific, and a north-to-south trough axis across
the central CONUS Plains. This pattern will provide and fairly tight
northwest-to-southeast oriented mid-level pressure gradient across
the area. Thus, expect gusty winds to occur mainly during the late
morning into early evening hours. Some minor cooling will also occur
Monday into Wednesday, but daytime temperatures are forecast to
remain above seasonal normals.
An impulse embedded within the faster belt of westerly/northwesterly
winds aloft will move across the Four Corners region Thursday. There
appears to be enough moisture with this system to justify a slight
chance of showers across the White Mountains Thursday with dry
conditions continuing elsewhere.
Thereafter, the deterministic 23/12Z GFS/ECMWF were in much better
agreement versus previous solutions regarding the evolution of a
deepening upper trough/low pressure system north of the area Friday
into Saturday. The main concern at this time is the progged very
tight mid-level gradient. The GFSX/ECMX wind speeds would easily
support Wind Advisory criteria, or perhaps High Wind Warning
criteria, Friday afternoon into Friday night.
These solutions prompted considerable adjustments to be made to the
gridded data PoP/Weather fields. Thus, slight chance of showers now
exists Friday night into Saturday as far west as Tucson, and higher
precip chances exist closer to the New Mexico border. Dry conditions
should return area-wide Saturday night into Sunday in response to
northwesterly flow aloft as the upper low moves well eastward into
the central CONUS Plains. This system is expected to bring daytime
temperatures next weekend that are forecast at this time to be below
Red Flag Warning from 11 AM to 7 PM MST Monday for AZZ151-152.
Fire Weather Watch from Tuesday morning through Tuesday evening
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