textproduct: NWS Phoenix

KEY MESSAGES

- Strong high pressure has settled over the region with near record temperatures expected today and Saturday.

- An unprecedented heat wave for March is expected for next week with highs topping 100 degrees by Wednesday and 105 degrees by next Friday, shattering daily records by as much as 10 degrees.

- Widespread Minor Heat Risk is expected through the weekend before increasing to Moderate HeatRisk by the middle of next week.

SHORT TERM /TODAY THROUGH SUNDAY/

An unseasonably strong high pressure ridge continues to impact our region with the center of the ridge situated just west of northern Baja. H5 heights over our region peaked yesterday between 586-588dm and have started to fall as the ridge slides farther to the south. However, this will not curtail our temperatures today as the unseasonably warm air mass remains in place allowing for lower desert highs to top out in the lower 90s in the Phoenix area to as warm as the mid 90s across southeast California and southwest Arizona.

By tonight, a very weak and subtle shortwave trough will be reaching the central California coast with a more significant trough entering the Pacific Northwest from the northwest. The weak shortwave will enter our region by later Saturday afternoon, further suppressing heights across our region into Saturday night. Higher level clouds will accompany this weak disturbance making Friday night through much of Saturday partly cloudy. Despite the presence of the higher clouds and the slightly lower heights, high temperatures Saturday may only drop a degree from Friday's. The lower heights (578-582dm) will be quite brief and mainly focused late Saturday into early Sunday before the next ridge quickly begins to raise heights from west to east by Sunday afternoon. NBM forecast highs for Sunday are nearly identical to Saturday with highs mainly between 90-93 degrees in the Phoenix area to 91-95 degrees across southeast California and southwest Arizona.

The passing disturbance this weekend will also lead to an increase in winds with areawide gusts up to around 20 mph on Saturday before becoming focused across the Lower CO River for Sunday and Monday with gusts as high as 25-30 mph.

LONG TERM /MONDAY THROUGH NEXT SATURDAY/

The forecast and forecast thinking for next week has barely changed with Moderate HeatRisk becoming widespread by the middle of the week and localized Major HeatRisk possible for next Friday and Saturday. The majority of the area will experience summer- like temperatures for a few days with highs potentially as hot as 110 degrees for next Thursday-Saturday. Please see our previous discussion for more detailed information.

PREVIOUS DISCUSSION

Issued at 324 AM MST Thu Mar 12 2026

An unprecedented heat wave for mid March is expected next week across the Western U.S. with widespread temperature anomalies of 20-30F. Model guidance continues to show remarkable agreement through all of next week with model trends over the past couple of days suggesting an even stronger record breaking ridge settling over the Western U.S. by Monday and lasting into next weekend. This event is likely to break daily records by as much as 10 degrees for many areas and all time March temperature records, especially across the Southwestern U.S. where the largest positive height anomalies are anticipated.

By late Saturday, the next high pressure ridge will be developing well off the coast of California, quickly reaching record strength for this time of year on Sunday. Large negative height anomalies developing across the Eastern U.S. will also help drive an increasing amplitudinal pattern, quickly expanding the ridge over the Western U.S. by Monday.

Climatological record H2 heights are projected over the entire West Coast and into the Western U.S. by early next week before slowly shifting eastward throughout the rest of next week. A large area of record H5 heights focused across the Southwestern U.S. is also expected to develop by mid week and last through at least next Thursday or Friday. Ensemble mean H5 heights of 588-592dm are shown across the Desert Southwest by early Wednesday before peaking as high as 594-596dm on or around next Thursday. For reference, sounding climatology data for Las Vegas, Flagstaff, and Tucson all show record H5 heights for March are around 590dm and April 591dm, 593dm, and 592dm respectively. So, to put this in better prospective the ridge for next week is forecast to be as strong if not a little bit stronger than any ridge this region has ever seen in March or April. Guidance does start to show some weakening of the ridge by next weekend, but that is where model uncertainty increases with some members hanging onto the ridge a bit longer.

Record temperatures are forecast for the majority of next week, particularly from Tuesday-Saturday. As the ridge begins to move into the region on Monday, highs should warm more into the mid 90s at least across the western deserts. The first 100 degree temperatures are likely to be seen by Tuesday with NBM forecast highs of 99-102 degrees across much of southeast California and southwest Arizona. Phoenix will most likely have to wait until Wednesday to hit 100 degrees which would easily break the earliest 100 degree day on record (currently March 26, 1988).

Forecast H8, H7, and H5 temperatures are all at record levels for Wednesday through next Saturday. It is not a question of whether we will get record temperatures next week, the question should be by how much will they be broken. Highs are nearly certain to top 100 degrees each day during the latter half of next week with the hottest readings even topping 105 degrees at some point next Thursday-Saturday. NBM 75th percentile temperatures continue to show potential for some spots to even hit 110 degrees late next week. The earliest ever 105 degree day in Phoenix is April 20th and the earliest 106 degree day is May 2.

Widespread Moderate HeatRisk will affect the area during the latter half of next week with at least some potential for localized areas of Major HeatRisk developing across the lower deserts. However, the large diurnal swings may keep this from occurring. Forecast lows are still shown to dip into the 60s for the majority of the area during the entire event which only puts the lows in the Minor category, affecting the calculation of the overall HeatRisk. Either way, this event should easily bring high- end Moderate HeatRisk for several days.

AVIATION

Updated at 0505Z.

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

No aviation concerns are expected during the TAF period. Winds will once again follow diurnal trends with window of VRB to calm conditions during the overnight and in between directional shifts. Clear skies will give way to increasing high clouds Friday afternoon and evening.

FIRE WEATHER

High pressure will dominate across the region through next week with temperatures around 15 degrees above normal through the weekend before heating up even further (20-30 above normal) later next week. Dry conditions will also prevail with MinRHs at or just below 10% and persisting through next week. Overnight recoveries will be poor to fair, mostly between 25-40% each night. Winds will remain light today before becoming increasingly breezy this weekend. Elevated fire danger is likely to become a problem this weekend into early next week, focused more across the Lower CO River Valley.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...None.