Wind Advisory 14, NWS Phoenix, AZ

Area Forecast Discussion
National Weather Service Phoenix AZ
1112 AM MST Fri Apr 17 2020

.UPDATE...Updated Aviation Discussion.

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.SYNOPSIS...
A couple of weak weather systems will move through the region over
the next several days bringing breezy to locally windy conditions
at times. However, rain chances are expected to remain north of
the forecast area. Temperatures will fluctuate as well but without
any sharp cooling trends. During the latter half of next week,
high pressure builds over the region. This will lead to highs in
the 90s on the lower deserts.

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.DISCUSSION...
At 2 am this morning, a weak closed low could be seen spinning just
off the southern California coast; southwest flow aloft ahead of the
low was spreading a bit of mainly high cloudiness into the deserts.
As the low starts to move inland later today, weak warm air
advection ahead of it will allow high temperatures in the central
deserts to rise into the mid or even upper 80s, with slightly cooler
conditions expected in far southeast California.

Model guidance, including operational runs of the GFS/ECMWF and
various ensemble suites, continue to suggest that this low will
quickly weaken and lift northeast across Arizona tonight into
Saturday; as is typical for mid April the low will bring little if
any precipitation to the deserts and will primarily usher in
slightly cooler temperatures and breezy to locally windy conditions.
By Saturday we can expect highs to fall to around 80 over the warmer
lower deserts. The strongest winds will primarily effect Imperial
County this afternoon and early evening with peak southwest to west
gusts in excess of 30 mph. GEFS plumes output showed no members
bringing any measurable rain to the Phoenix area with this system
and the latest 5 day WPC QPF output showed virtually no
accumulations in our area. IVT plumes forecasts also did not depict
any moisture intrusions into the desert southwest with this upcoming
low...or with any system moving into the area early next week.

As the weakened low quickly moves east of the area later Saturday, a
dry generally westerly flow aloft will set into the area bringing a
warming trend allowing high temperatures to climb into the mid to
upper 80s by Monday. There will also be increasing high cloud
spreading through the flow Sunday into Monday.

Early next week, another fast moving open wave trof will push inland
and move across the desert southwest mainly in the Monday night
through Tuesday night time frame. This will be a weak, rather
moisture starved system, and any precipitation will likely be
confined to higher terrain areas of northern Arizona. As we move
through early April and into the latter part of the month, it is
common that Pacific trofs bring little measurable precipitation to
the southern deserts; these systems mainly provide some amount of
cooling and increased breeziness which can lead to enhanced fire
weather danger if the winds become strong enough. At this time we
don't expect that winds will be overly strong with the Tuesday
system so fire weather concerns should be modest at best. Also,
cooling will not be significant with Tuesday trof as the lower
deserts should stay in the mid 80s for the most part.

For the latter portion of the extended period - the Wednesday into
Thursday time frame - we can expect high pressure aloft to build
into the desert southwest with the southern Arizona deserts to see
500mb heights rise into the 582-584dm range. Dry northwest flow
aloft, sunny skies and high heights should allow the warmer deserts
to see the warmest readings so far this year. The Phoenix area will
likely climb into the low 90s Wednesday and the mid 90s by Thursday.
These warm readings will be well above seasonal normals; the normal
high for next Thursday is just 87 degrees as compared to the
forecast high of 95 for Phoenix.

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.AVIATION...Updated at 1811Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

Increasingly breezy winds heading into the afternoon will be the
primary aviation impact today. Gusts should approach 20-25 kts
this afternoon through early evening. Breezy southerly cross
winds are likely for a few hours between 18-22Z, for KPHX and
DVT, as winds veer toward the southwest. Surface winds should
gradually subside after sunset this evening. However, a glancing
system will lead to a brief increase in southwesterly low level
winds, between 1-3 kft, between ~4-8Z. This may lead to minor LLWS
concerns. Isolated convection will likely pass well off to the
northwest with the system as well, but should not be any concern
to the Phoenix area. A mix of mid and high clouds are expected
through the TAF period, with VFR prevailing.

Southeast California/Southwest Arizona including KIPL and KBLH:

Breezy to windy conditions are expected at both terminals today.
Winds at KIPL will favor the west through the next 24 hours with
gusts upwards of 25-30 kts expected this afternoon. At KBLH, winds
will favor a south to southwesterly component through the TAF period
with gusts upwards of 25 kts this afternoon. Gusts at both
terminals should subside by midnight, but sustained winds may
remain elevated around 7-12 kts through the night. Otherwise,
high clouds aoa 20 kft will increase throughout today before
scattering out by this evening.

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.FIRE WEATHER...
Sunday through Thursday:
Winds will be light on Sunday before another relatively weak
weather system moves through the region in the Monday-Tuesday
timeframe. The system is expected to be dry with only a modest
increase in Min RH values (increasing from mid teens to near 20%
by Tuesday on the lower deserts). Winds will strengthen as well.
At this time, critical fire weather thresholds are not expected to
be met. On Wednesday and Thursday, a warming trend can be expected
along with lighter winds and a lowering of minimum RH below 15
percent across the deserts. In fact, highs on the lower deserts are
anticipated to be well into the 90s by Thursday.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

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.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

DISCUSSION...CB
AVIATION...Benedict/Smith
FIRE WEATHER...AJ/CB