Sunrise 5:53 AM   Sunset 7:17 PM Moonrise 7:18 PM   Moonset 5:38 AM

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FXUS65 KPSR 232355 AFDPSR

Area Forecast Discussion National Weather Service Phoenix AZ 455 PM MST Tue Apr 23 2024

UPDATE
Updated 00Z Aviation Discussion.

SYNOPSIS
A couple of weather systems will move through the region in the Wednesday through Saturday time frame. This will lead to a significant cooling trend as well as breezy to windy conditions.
Desert highs drop to the lower 80s Friday and Saturday. Moisture with these systems will be quite limited and thus precipitation chances will be confined primarily to the northern half of Arizona. An exception will be slight chances of showers for east- central Arizona and far northern Maricopa County on Friday night and Saturday morning. A warming trend begins Sunday with desert highs returning to the 90s Monday and Tuesday.

DISCUSSION

Model trends remain on track with an upper low off the California coast moving through Wed-Thu and a follow-on shortwave from the Pacific Northwest moving through Fri-Sat. Despite dynamical forcing and cooling aloft with those systems, moisture looks to be limited and thus PoPs are quite meager. The NBM 90th percentile 12 hour QPF is zero over our forecast area until Friday night and Saturday. Even then, the amounts are less than one tenth of an inch and only cover portions of south-central AZ. Something to keep an eye on however is that some of the CAMS (e.g. NamNest and to a lesser extent FV3) are depicting a batch of showers moving through southwest AZ and western Maricopa County on Wednesday night/early Thursday. This is plausible given the aforementioned lifting mechanisms but not enough to go on yet to introduce mention of precip for those areas during that time.

The most noticeable sensible weather impacts from the passage of these systems will be the cooling trend and breezy to windy conditions. Highs on the lower elevations drop to the lower 80s by Friday and Saturday (upper 70s some spots). A warming trend follows with highs getting pretty close to the peaks we've just had by next Tuesday. As for winds, Wednesday through Friday look to be the windiest with less windy, though still breezy, conditions Saturday. Advisory strength conditions (gusts 40+ mph)
are expected to be limited to our portion of southeast California (mainly Imperial County). A Wind Advisory has been issued for the southwest corner of Imperial County from 5pm Wednesday to 11pm Friday. There is also a Wind Advisory for much of the rest of Imperial County for a shorter period of time (5pm Wednesday to 3am Thursday). Likewise for western portions of Joshua Tree N.P. It's possible that another Advisory for those areas may be needed for later Thursday.

AVIATION
Updated at 2355Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Winds are still slowly making their turn to westerly and directions will continue to be 140v210 with gusts of 15-20 kt until 01-02Z when winds become westerly. Westerly winds will gusts 15-20 kt will continue until mid-to-late this evening when wind speeds will calm down and then become easterly for the overnight hours. Winds tomorrow will follow a similar pattern as they did today. By mid-morning winds will start to slowly make their turn to westerly with directions of 140v210 expected again with gusts of 15-20 kt during the afternoon. FEW-SCT high clouds are expected throughout the day tomorrow.

Southeast California/Southwest Arizona including KIPL and KBLH: Winds at KIPL will mainly be out of the west whereas at KBLH winds will mainly be out of the S/SW through the TAF period. Wind gusts of 15-20 kt will continue through the mid-evening at KBLH and through the late-evening at KIPL. Winds speeds will decrease at both terminals for the overnight and morning hours before starting to pick up speed again for the mid-to-late afternoon hours. Skies will be mostly clear with FEW high clouds expected tomorrow morning.

FIRE WEATHER
A couple of weather systems will move through the region in the Wednesday through Saturday time frame. This will lead to a significant cooling trend as well as breezy to windy conditions.
Conditions will flirt with critical wind and humidity thresholds for a few hours late Wednesday afternoon in some spots near and west of the Lower Colorado River Valley. Otherwise, increasing humidities will preclude critical fire weather conditions. For instance MinRH values on Wednesday will be in the 10-15% range across much of the forecast area followed by an increase of 5-10% on Thursday with little change on Friday. However, these systems will struggle to produce precipitation over the forecast area with rain chances confined to the northern half of Arizona. An exception will be slight chances of showers for higher terrain and foothill locations of south-central AZ on Friday night and Saturday morning. A warming trend begins Sunday with desert highs returning to the mid and upper 90s by Tuesday. MinRH values drop to the 10-20% range by Sunday and 10-15% range by Monday. MaxRH bottoms out in the 25-50% range Tuesday morning.

PSR WATCHES/WARNINGS/ADVISORIES
AZ...None.
CA...Wind Advisory from 5 PM Wednesday to 3 AM PDT Thursday for CAZ560-563-565>567.

Wind Advisory from 5 PM Wednesday to midnight PDT Friday night for CAZ562.

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