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FXUS65 KPSR 291719
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1019 AM MST Mon Apr 29 2024

.UPDATE...Updated 18z Aviation Discussion.

&&

.SYNOPSIS...
Warmer temperatures are anticipated over the next several days with
highs rising into the low to mid 90s across the lower deserts. An
upper level trough will pass through the Intermountain West mid-week
resulting in breezy conditions across southcentral AZ and southeast
CA. Otherwise, dry conditions will prevail across the forecast area
through at least this weekend.

&&

.DISCUSSION...
Latest mid-lvl wv imagery and 500 mb streamline analysis reveals
broad longwave troughing over the central U.S. with dry NW flow
present over AZ and southeast CA. As we head through today, upper
level flow will transition to quasi-zonal as another trough enters
the Pacific NW. As this occurs, we will see 500 mb hghts rise to
around 575-577 dam over the forecast area by this afternoon.
Consequently, mid-level temperatures will increase by a few
degrees compared to yesterday which will result in highs rising to
above normal levels. Expect temperatures to top out into the
upper 80s to lower 90s across the desert communities under clear
skies and light winds. Dry, tranquil conditions will carry into
tonight with lows falling to the upper 50s to lower 60s. On
Tuesday, mid-lvl hghts/thicknesses will increase further with 850
mb temperatures rising to 18-21 deg C. This will promote sfc highs
in the low to mid 90s or around 3-6 degrees above average.

On Wednesday, a shortwave trough will swing through the Intermountain
West, resulting in the tightening of the 700-500 mb hght gradient
over our forecast region. This will lead to increased breeziness
with gusts up around 20-25 mph across much of the area. A decrease
in overall 500 hghts will result in a slight cool down with highs
closer to normal Wednesday afternoon. The afomentioned shortwave
trough will continue to progress through the 4-Corners region on
Thursday, sending a backdoor front into the Colorado River Valley
where gusty northerly winds will be possible during the morning
hrs. This front will be quite weak however and will result in no
sensible change to the temperatures with highs still expected to
reach the lower 90s by Thursday afternoon.

As we head into this weekend there is still a fair amount of spread
between global ensembles regarding the upper level pattern. The GEFS
is showing a fairly robust trough moving onto the CA coast by Sunday
into Monday whereas the EPS is indicating that troughing will be
much more subdued and confined to the Pacific NW. The deterministic
NBM indicates highs continuing in the low to mid 90s through this
weekend, though a larger temperature spread is seen in the
interquartile range due to the aforementioned model uncertainties.
Despite the uncertainty in temperatures, ensembles and deterministic
models do agree that dry conditions are favored to persist through
this weekend and into early next week and thus PoPs remain nil.

&&

.AVIATION...Updated at 1120Z.

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

Expect VFR conditions for all terminals. No major weather issues
anticipated through tonight under clear skies. Timing of the
usual diurnal wind shifts will be typical for this time of year
while any enhanced gusts remains minimal or absent. Look for
extended periods of nearly calm conditions during transition
periods.


&&

.FIRE WEATHER...
Warm and dry conditions will persist this week and into this weekend
with high temperatures around 3-5 degrees above normal each day.
Winds will be light and follow typical upslope/downvalley patterns
today and Tuesday before increased breeziness arrives Wednesday with
gusts reaching the 20-25 mph range across much of the area. Windy
conditions will also be possible across the western districts on
Thursday as a dry cold front passes through the Colorado River
Valley. Minimum relative humidity values will range from 10-15%
today. However, it will become noticeably drier across the lower
deserts by mid-week with sub 10% RH values possible in some
locations. Moisture recovery will range from poor to fair each
night, or around 25-50%.

&&

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

$$

DISCUSSION...Salerno
AVIATION...Young/Trampp
FIRE WEATHER...Salerno