Sunrise 5:42 AM   Sunset 7:09 PM Moonrise 10:16 PM   Moonset 7:10 AM

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FXUS65 KPSR 260512 AFDPSR

Area Forecast Discussion National Weather Service Phoenix AZ 1010 PM MST Thu Apr 25 2024

UPDATE
Updated Aviation

SYNOPSIS
Breezy to windy and relatively cool conditions will continue through Saturday. The windier day will be Friday. There will be a chance of showers over portions of south-central Arizona Friday night and Saturday morning, mainly over higher terrain areas. Rainfall amounts, if any, will be light. A significant warming trend ensues Sunday through Tuesday with little change Wednesday and Thursday.
That will mean desert highs well into the 90s for the workweek with readings close to 100 at some spots by midweek.

DISCUSSION
There is a sizable short wave centered over AZ with a potent vort max within it over northeast AZ. That feature generated shower and storm activity over western AZ early this morning with convective showers developing over the northern half of AZ. Follow-on convective showers associated with a cold pool aloft continue to be limited to FGZ's forecast area. The short wave will continue to weaken with time as it tracks northeastward and largely be out of AZ by 00Z this afternoon. For our forecast area, the most noticeable impact is breeziness coupled with cooler temperatures. 24 hour temperature trends early this afternoon are running roughly 5-10 degrees cooler. Some areas, most notably Imperial County, have been experiencing strong winds where the surface pressure gradient is best. As the wave weakens and moves further away, the flow aloft will also weaken leading to a temporary weakening of winds.

The approach of another wave from the Pacific northwest along with terrain effects, will lead to restrengthening of winds there and a Wind Advisory remains in effect for later this afternoon and evening. After something of an overnight and morning lull, strong winds develop again Friday afternoon and evening. In fact, much of Imperial County as well as western Joshua Tree N.P. and some higher terrain portions of southern Gila County have anywhere from 60-100% probability of wind gusts exceeding 40 mph. Thus, a Wind Advisory is in effect. Elsewhere will still be windy but not as strong. Winds won't be as strong Saturday but still breezy to locally windy.

This second system will have a bit better potential to produce rain for our area (more widespread chances over northern AZ). But, precip chances will be limited mainly to higher terrain and foothill locations of south-central AZ Friday night and Saturday morning.
Precipitation, if any, will be light. In fact, the 90th percentile of the NBM 12 QPF ending 12Z Saturday is less than one tenth of an inch for the lower elevations up to a quarter inch for above 4000ft). Very localized spots could see more if a thunderstorm passes over but thunderstorm potential is less than 20% (less than 10% lower elevations). Snow flurries could be seen as low as 6000ft with accumulations above 6500 ft.

With the exit of the second system later Saturday, a significant warming trend ensues Sunday through Tuesday with little change Wednesday and Thursday. That will mean desert highs well into the 90s for the workweek with readings close to 100 at some spots (incl.
Greater Phoenix) by midweek.

AVIATION
Updated at 0510Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Periods of gusty afternoon/early evening winds will be the primary weather concern through Friday night under FEW-SCT midlevel decks.
Confidence is good wind directions will revert to light easterly after midnight, however directions should veer back to S/SW quickly by late Friday morning with gusts progressively strengthening during the afternoon. By late afternoon, gusts reaching a 25-30kt range should be common. Isold SHRA/TSRA across northern AZ should decay before reaching terminals Friday evening, however there is a remote chance (less than 20%) that a residual SHRA and outflow descends into the Phoenix metro.

Southeast California/Southwest Arizona including KIPL and KBLH: Strong, gusty W/SW winds will be the main weather concern through Friday evening under clear skies. Gusts should generally relax during the overnight hours, however stronger gusts should resume fairly quickly Friday afternoon. Widespread 20-30kt gusts should become common with KIPL likely experiencing gusts above 35kt at times late Friday afternoon/evening. As a result, lofted dust and regionally reduced slantwise visibilities are possible, though not specifically mentioned at the surface at any particular TAF site.

FIRE WEATHER
A period of enhanced winds continues through Saturday with portions of southeast CA and southern Gila County seeing very strong winds at times (mainly Friday). Fortunately, RH values are expected to remain high enough (MinRH 20-30%) to avoid critical thresholds during the time of strongest winds. RH trends down Saturday over the lower elevations (MinRH 10-20%) but winds are not expected to reach critical thresholds. Higher RH values (MinRH 25-35%) linger over south-central AZ Saturday. A significant warming trend takes place Sunday through Tuesday with little change Wed-Thu. RH trends down as well with MinRH bottoming out around 10-15% by Tuesday (little change through Thursday). MaxRH bottoms out around 25-45% by Wednesday. Winds next week will be lighter.

PSR WATCHES/WARNINGS/ADVISORIES
AZ...Wind Advisory from noon Friday to midnight MST Friday night for AZZ557-558.

CA...Wind Advisory from noon Friday to midnight PDT Friday night for CAZ560-563-565>567.

Wind Advisory until midnight PDT Friday night for CAZ562.

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