Area Forecast Discussion
Issued by NWS Tucson, AZ
FXUS65 KTWC 250424
Area Forecast Discussion
National Weather Service Tucson AZ
920 PM MST Mon Apr 24 2017
.SYNOPSIS...Expect strong and gusty winds Tuesday as a weather
system moves north of the area. This system may also bring a few
showers and thunderstorms to the White Mountains. Otherwise, dry
conditions will prevail through Thursday. Strong and gusty winds
will return Friday into Saturday along with a chance of showers east
of Tucson. Cooler Saturday followed by dry conditions with a warming
trend early next week.
.DISCUSSION...Winds a little slow to ease up this evening with
dewpoints very slowly creeping up thanks to a storm system that is
dropping southeast into the western US this evening. As this system
approaches the mid level gradient will continue to increase
overnight which will keep a breeze going through the night across
ridges and normally windier valley locations (like Sierra Vista
region). The gradient peaks Tuesday afternoon for the strongest
winds however it will be tight enough that the winds will increase
earlier in the morning than is typical with winds quickly increasing
after 8-9 am. A wind Advisory is in effect Tuesday to cover the
Thankfully humidity levels will be higher than they have been
lately. Most model guidance show dewpoints rising significantly
tonight and remaining elevated Tuesday. I have some concern with
that but current forecast is at the mid-point of the guidance and
will leave as is at this time. There is expected to be enough
moisture for a few showers across the White Mountains as the system
The wind will be slow to ease again Tuesday evening but after 10 pm
to midnight it should really drop off. Wednesday will be more of a
typical day wind with much drier air over the region. No
significant changes made at this time.
.AVIATION...Valid through 26/00Z.
Expect isolated to scattered -TSRA/-SHRA across the White Mountains
NE of KSAD Tuesday. Otherwise, SCT-BKN clouds above 20k ft AGL this
evening, then SCT-BKN clouds around 9k-14k ft AGL and BKN clouds
above 20k ft AGL late tonight into Tuesday afternoon. Clearing skies
should occur just after the valid period. Surface wind overnight
mainly 5-15 kts then increasing to westerly 15-25 kts with gusts
around 35 kts Tuesday. Aviation discussion not updated for TAF
.FIRE WEATHER...A Red Flag Warning is in effect from 11 AM to 7 PM
MST Tuesday for the southeastern half of fire weather zone 152. The
combination of strong and gusty winds, low relative humidity and a
high fire danger will create critical fire weather conditions.
For the remainder of southeast AZ outside of the Warning area, the
afternoon relative humidity is expected to be too high to meet Red
Flag Criteria, the reason for the limited area of the warning.
However, winds will be strong across the entire area during the
afternoon which could cause significant forward fire spread despite
the higher humidity levels.
Critical fire weather conditions should occur again Friday across 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, dry conditions through Thursday except for a slight
chance of showers and thunderstorms near the White Mountains
Tuesday. There is a chance of showers across the White Mountains
Friday, then a chance of showers east of Tucson Friday night into
Saturday. Cooler temperatures will occur Saturday followed by dry
conditions with a warming trend Sunday into next Monday.
.PREV DISCUSSION...for later periods...
The 24/12Z GFS/ECMWF have trended drier versus previous solutions
during the Friday into Saturday period. Thus, PoPs were trended down
for the Tucson metro area versus the official forecast from 24 hours
ago. Have opted for a chance of showers across the White Mountains
Friday followed by a slight chance of showers, or a chance of
showers (mainly White Mountains) Friday night and Saturday.
However, the main impact from this deepening low pressure system
north of the area still appears to be a high likelihood for strong
winds to occur across much of the area Friday, then mainly across
eastern sections Saturday. Expect cooler temperatures Saturday, then
dry conditions with a warming trend Sunday into next Monday.
Red Flag Warning from 11 AM to 7 PM MST Tuesday for AZZ152.
Wind Advisory from 11 AM to 7 PM MST Tuesday for AZZ507>509-
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