Area Forecast Discussion
Issued by NWS Tucson, AZ
FXUS65 KTWC 260339
Area Forecast Discussion
National Weather Service Tucson AZ
845 PM MST Tue Apr 25 2017
.SYNOPSIS...Dry conditions will prevail through Thursday. Expect
markedly less wind Wednesday, then strong and gusty winds will occur
again Friday into Saturday along with a chance of showers east of
Tucson. Cooler Saturday followed by dry conditions with a warming
trend next week.
.DISCUSSION...Winds are gradually easing across the area this
evening, but slower than is typical due to the strength of the
system passing by. Locations east and north of Wilcox are still
experiencing fairly strong winds but even there they will weaken
overnight. Thankfully the worst is behind us for today. As a result
the wind advisory and Red Flag Warnings were allowed to expire at 8
pm. I made a few adjustments to a few elements of the the next 24
hours but no big changes.
Wednesday will bring much lighter but still gusty northwest winds in
the afternoon along with a crash in low level moisture begining in
the morning. Looking further ahead (which is described in more
detail further below) looking at an increase in winds Thursday and
more so Friday and potentially lingering into Saturday far eastern
areas before the pattern shifts and things settle down a bit.
.AVIATION...Valid through 27/06Z.
BKN clouds above 15k ft AGL until around 26/12Z then SKC to SCT
clouds above 20k ft AGL Wednesday into Wednesday evening. Surface
wind wly/nwly 10-20 kts with gusts near 30 kts diminishing to mostly
less than 15 kts by 26/12Z then variable in direction less than 12
kts 12Z-18Z Wednesday. Surface wind Wednesday afternoon and evening
10-22 kts with gusts near 30 kts. The strongest speeds will be east
of KTUS. Aviation discussion not updated for TAF amendments.
.FIRE WEATHER...Winds will continue to gradually ease through the
night becoming rather light toward morning except across ridges
where west-northwest winds will remain elevated. Dewpoints will
continue the slow downtrend but they will quickly drop Wednesday
morning when mixing starts. Ultimately RH levels will drop into the
single digits by afternoon with a NW breeze developing for areas of
elevated fire weather conditions.
Somewhat stronger winds are expected Thursday afternoon with min RHs
in the 10-15% range leading to areas of elevated and local critical
Fire weather conditions. Winds are expected to increase further
Friday as a system dives across the area however RH levels will be a
bit higher and marginal for critical fire weather conditions.
Otherwise, dry conditions will occur into Friday morning except for
a slight chance of showers and thunderstorms near the White
Mountains this evening. There is a chance of showers across the
White Mountains Friday, then a chance of showers east of Tucson
Friday night into Saturday. Dry conditions are expected Sunday into
early next week.
.PREV DISCUSSION /235 PM MST/...The winds will continue to be the
biggest forecast concern through the weekend as a series of systems
dig into the region from the northwest. Strong winds today with Wind
Advisory, Red Flag Warning and Blowing Dust Advisory all in effect
this afternoon. Wind gusts have pushed near 50 mph in portions of
the wind advisory area, especially east of Tucson. Extremely
dangerous fire behavior is causing issues at the Sawmill fire south
of Tucson (northeast of Madera Canyon), with rapid growth over the
past 18 hours. A Portion of I-10 in Cochise County has been closed
due to blowing dust. Winds will diminish this evening as the system
lifts northeastward into the Great Plains, but still breezy in some
eastern locations overnight.
With the strong ridge anchored off the Pacific coast, we`ll keep a
breezy northwesterly flow Wednesday, but the gradient won`t sharpen
to windy levels again until the next system pushes this way Friday.
A slightly more amplified flow should allow the Friday/Saturday
system to dig a little deeper into eastern Arizona before kicking
northeast Sunday. As such, a few showers possible Saturday, but the
main story will still be the wind. Another round of wind advisories
possible (especially east of Tucson) with fire concerns discussed in
the fire weather section below.
Temperatures will actually drop well below climo Saturday and
Saturday night, with overnight lows ranging from 30s in eastern and
southern areas to 40s from Tucson westward. A freeze is not out of
the question Sunday morning for colder valley locations of Cochise
High pressure takes over next week with dry conditions and
temperatures back well above average by Monday or Tuesday.
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