Air Resources Laboratory banner image
Air Resources Laboratory web site National Oceanic and Atmospheric Administration (NOAA)

az discuss


Office: PSR

FXUS65 KPSR 211213
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
513 AM MST Wed Nov 21 2018

.UPDATE...
Updated Aviation and Fire Weather sections.

&&

.SYNOPSIS...
Skies will be mostly clear today before high clouds start to
increase in the afternoon. A series of relatively dry low
pressure systems will move through the region over the next
several days. The main result will be breezy conditions at times,
occasional thick high cloudiness, and a gradual cooling trend
through the weekend. The best chance of precipitation will be
Thursday afternoon and evening.

&&

.DISCUSSION...
Today through Friday...
The upper low that brought high clouds to the forecast area
yesterday has now shifted to the southern Plains. That feature is
within undercutting flow on the southern side of a ridge over the
western CONUS. This will make for mostly clear skies today with
similar high temps as Tuesday. The ridge will be short lived
though due to an upper trough already moving into the West Coast.
In addition to moisture already within the trough, it is helping
to advect some subtropical moisture northeastward toward far
northwest Mexico and the Desert Southwest. Models continue to show
the trough tracking through the western CONUS on Thursday and
Thursday night. However, it weakens quite a bit in the process as
hits the ridge and an upstream system steals its thunder so to
speak. That will mean less robust moisture making it across the
southern California and northern Baja mountains and less moisture
from the subtropics making it north of the Mexico border. This
will hinder precip potential for our forecast area. Another
hindrance is that the dynamical forcing largely misses us just to
the north. That will mean only very slight chances of light rain
limited primarily to higher terrain areas. Too bad since the jet
core with the system peaks at about 140 kts over western AZ.
Otherwise, breezes pick up on Thursday and there will be some
minor cooling followed by some slight additional cooling on
Friday.

Saturday through Tuesday...
Yet another system affects the western CONUS late in the week and
over the weekend. This system will track from northwest to
southeast. The brunt of it goes through the NW CONUS and into the
central Rockies. Though there is some leftover moisture over the
Interior West for this system to work with, it won't be strong
enough over our area for precip. Instead, we will get some north
and northeasterly breezy to windy conditions later Saturday into
Sunday. There will be some minor cooling as well felt on Sunday.
That will mean highs in the Phoenix area struggling to reach 70
with the warmest deserts such as Yuma and El Centro in the lower
70s. For early next week, models are in fairly good agreement that
there will be narrow high amplitude ridging over western North
America. There is also agreement in the idea of a short wave
moving through the ridge and enhancing split in the Westerlies as
it develops into a weak upper low centered roughly over Baja
Mexico. There are differences in the model solutions on this
feature but for now, it looks to be a non-factor for our forecast
area. However, it will help keep temperatures from rebounding.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH:

Dry and stable conditions can be expected today and tonight.
Wind directions at the surface and within the lowest 5-10kft ASL
will favor east and southeast directions for much of the day.
Surface winds over metro Phoenix will become light and variable in
the afternoon favoring westerly directions. No significant clouds
except for increasing cirrus during the afternoon.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Friday through Tuesday:
Conditions are expected to be dry through the weekend and early
next week. Winds will be light Friday before a system passing
mainly through the Rockies leads to breezy northerly winds
Saturday afternoon into Sunday along with somewhat cooler
temperatures. Winds will continue to favor north and northeast
directions through early next week with high temperatures
remaining a few degrees below normal. Humidities begin trending
down Friday with a sharp decline on Sunday resulting in minimum
humidities in the upper teens to low 20s at most places.
Anticipate little change thereafter with overnight recovery
remaining at least fair to good.


&&

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

&&

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

$$

DISCUSSION...AJ
AVIATION...AJ
FIRE WEATHER...AJ

FXUS65 KPSR 211248 CCA
AFDPSR

Area Forecast Discussion...CORRECTED
National Weather Service Phoenix AZ
548 AM MST Wed Nov 21 2018

.UPDATE...
Updated Aviation and Fire Weather sections.

&&

.SYNOPSIS...
Skies will be mostly clear today before high clouds start to
increase in the afternoon. A series of relatively dry low
pressure systems will move through the region over the next
several days. The main result will be breezy conditions at times,
occasional thick high cloudiness, and a gradual cooling trend
through the weekend. The best chance of precipitation will be
Thursday afternoon and evening.

&&

.DISCUSSION...
Today through Friday...
The upper low that brought high clouds to the forecast area
yesterday has now shifted to the southern Plains. That feature is
within undercutting flow on the southern side of a ridge over the
western CONUS. This will make for mostly clear skies today with
similar high temps as Tuesday. The ridge will be short lived
though due to an upper trough already moving into the West Coast.
In addition to moisture already within the trough, it is helping
to advect some subtropical moisture northeastward toward far
northwest Mexico and the Desert Southwest. Models continue to show
the trough tracking through the western CONUS on Thursday and
Thursday night. However, it weakens quite a bit in the process as
hits the ridge and an upstream system steals its thunder so to
speak. That will mean less robust moisture making it across the
southern California and northern Baja mountains and less moisture
from the subtropics making it north of the Mexico border. This
will hinder precip potential for our forecast area. Another
hindrance is that the dynamical forcing largely misses us just to
the north. That will mean only very slight chances of light rain
limited primarily to higher terrain areas. Too bad since the jet
core with the system peaks at about 140 kts over western AZ.
Otherwise, breezes pick up on Thursday and there will be some
minor cooling followed by some slight additional cooling on
Friday.

Saturday through Tuesday...
Yet another system affects the western CONUS late in the week and
over the weekend. This system will track from northwest to
southeast. The brunt of it goes through the NW CONUS and into the
central Rockies. Though there is some leftover moisture over the
Interior West for this system to work with, it won't be strong
enough over our area for precip. Instead, we will get some north
and northeasterly breezy to windy conditions later Saturday into
Sunday. There will be some minor cooling as well felt on Sunday.
That will mean highs in the Phoenix area struggling to reach 70
with the warmest deserts such as Yuma and El Centro in the lower
70s. For early next week, models are in fairly good agreement that
there will be narrow high amplitude ridging over western North
America. There is also agreement in the idea of a short wave
moving through the ridge and enhancing split in the Westerlies as
it develops into a weak upper low centered roughly over Baja
Mexico. There are differences in the model solutions on this
feature but for now, it looks to be a non-factor for our forecast
area. However, it will help keep temperatures from rebounding.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH:

Dry and stable conditions can be expected today and tonight.
Wind directions at the surface and within the lowest 5-10kft ASL
will favor east and southeast directions for much of the day.
Surface winds over metro Phoenix will become light and variable in
the afternoon favoring westerly directions. No significant clouds
except for increasing cirrus during the afternoon.

For the Imperial Valley, there will be locally reduced visibilities
in smoke this morning. The KIPL ASOS has occasionally observed
readings as low as 4SM since midnight. Anticipate improvement by late
morning/midday as the inversion breaks and mixing increases.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Friday through Tuesday:
Conditions are expected to be dry through the weekend and early
next week. Winds will be light Friday before a system passing
mainly through the Rockies leads to breezy northerly winds
Saturday afternoon into Sunday along with somewhat cooler
temperatures. Winds will continue to favor north and northeast
directions through early next week with high temperatures
remaining a few degrees below normal. Humidities begin trending
down Friday with a sharp decline on Sunday resulting in minimum
humidities in the upper teens to low 20s at most places.
Anticipate little change thereafter with overnight recovery
remaining at least fair to good.


&&

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

&&

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

$$

DISCUSSION...AJ
AVIATION...AJ
FIRE WEATHER...AJ



Office: TWC FXUS65 KTWC 211627 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 927 AM MST Wed Nov 21 2018 .SYNOPSIS...A passing system may bring a few sprinkles or snow flurries to higher mountain peaks on Thanksgiving Day. Otherwise, dry conditions into early next week. High temperatures today will be a few degrees above normal. Seasonably mild daytime temperatures will then prevail Thanksgiving Day into early next week. && .DISCUSSION...A weather system impacting the West Coast today will pass through the area tomorrow. Latest models continued to indicate limit moisture associated with the system this far south. That said, the current forecast for light shower/sprinkles and/or snow flurries above 8500 feet still looked good. Otherwise, expect considerable cloudiness and a little cooler daytime temperatures for Thanksgiving Day. No updates necessary this morning. Please refer to the additional sections for more details. && .AVIATION...Valid through 22/18Z. Expect SKC conditions this morning. Cloud cover will increase this afternoon leading to SCT-BKN clouds at or above 15k ft AGL toward the end of the TAF period. SFC winds variable in direction mainly under 12 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Expect dry conditions area wide into early next week. 20-foot winds will be slightly elevated out of the west Thursday and Saturday with some afternoon gusts possible. Sunday into Tuesday morning expect easterly winds; otherwise, 20-foot winds will be light and terrain driven. && .PREV DISCUSSION...Upper ridge axis extended from southwest Arizona northward into central Montana early this morning. Meanwhile, an upper trough axis extended from near the Pacific Northwest coast southwestward to well west of the southern California coast, or near 30N/135W. A band of southern stream westerlies also extended from well west of Baja California eastward across Sonora Mexico and further east into the southeastern CONUS. The upper ridge axis will move eastward across this forecast area today and continue eastward into the central/southern Rockies tonight as the upper trough approaches the West Coast. As a result, clear skies this morning followed by increasing high clouds from the west this afternoon. Cloud bases should lower closer to higher mountain top levels toward daybreak Thanksgiving Day, then mostly cloudy skies continuing Thanksgiving Day as the upper trough continues eastward into the Intermountain West. Various 21/00Z numerical weather prediction models and especially the deterministic GFS/ECMWF and GEFS/EPS have generally trended downward on measurable precip chances for southeast Arizona Thursday. Thus, the inherited PoPs were lowered to remove earlier mention/depiction of slight chance of showers across portions of the area. Although PoPs are now less than 10 percent, would not be surprised if virga occurs Thursday. As such, sprinkles for some elevations below 5000 feet and snow flurries across higher peaks are certainly in the offing. Clouds should gradually decrease on Friday but enough mid/high level moisture lingers for partly cloudy skies. The next forecast concern has been regarding a shortwave trough that has been depicted by various solutions to have differing amplitudes while moving eastward across the Four Corners region on Saturday. The 21/00Z deterministic GFS/ECMWF were very similar with depicting a flatter/less amplified/further northeast moving system versus previous solutions. Given these solutions, PoPs were lowered to less than 10 percent across the White Mountains Saturday night which also removed previous mention/depiction of a slight chance of snow showers. Thereafter, the GFS/ECMWF remained quite similar with depicting an upper trough to develop over the southwest CONUS late Sunday into Sunday night. The models depict a weak closed upper low to form south or southwest of the area on Monday. Some clouds should accompany this system but no precipitation is expected to occur. Dry conditions are forecast to continue next Tuesday under light nly/nwly flow aloft as upper low remains well south or southeast of this forecast area. High temps today will generally range about 2-5 degrees above normal. A modest cooling trend remains on tap for much of the area Thanksgiving Day into Friday before a few degrees of warming occurs Saturday. Daytime temps Sunday into Tuesday should have very minor daily changes and should also be quite close to seasonal normals. && .TWC WATCHES/WARNINGS/ADVISORIES...None. && PREV DISCUSSION...Francis AVIATION...Hardin FIRE WEATHER...Hardin $$ Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
Office: FGZ FXUS65 KFGZ 211626 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 926 AM MST Wed Nov 21 2018 .SYNOPSIS...Expect dry weather with near normal temperatures across northern Arizona again today. On Thanksgiving Day, a cold frontal passage will bring a chance of light showers and cooler temperatures. Another cold front will move through on Saturday. && .UPDATE...It's a beautiful start to the day, with mostly clear skies and temperatures warming quickly over N. Arizona. Expect only a few high clouds today with light winds and high temperatures near to, or slightly above normal. Current models are consistent with bringing in light rain or snow showers for Thanksgiving Day, generally around and north of the Flagstaff area. Current forecast is on track, with no updates expected at this time. && .AVIATION...For the 18Z Package...Expect mainly VFR conditions for the 24 hour forecast period. SW winds increasing aft 15Z Thursday to 10-15G20-30 kts. Cloud bases 10-15 kft by 15Z will slowly lower, with showers developing from the west. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...For today, expect light winds and slightly above normal temperatures under mostly clear skies. On Thursday, a passing cold front will deliver cooler conditions, breezy southwest winds and a chance of rain and snow showers. Friday through Sunday...Expect dry weather and near normal temperatures on Friday, before another cold front impacts the region Saturday and Sunday. This mainly dry front will bring a sharp drop in temperatures and a return of northwest through northeast winds. .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && $$ PUBLIC...BAK/KD AVIATION...NL FIRE WEATHER...NL For Northern Arizona weather information visit weather.gov/flagstaff