textproduct: NWS Phoenix

UPDATE...Updated 12z Aviation Discussion

KEY MESSAGES

- Weather conditions across the region this week will remain quiet as high pressure persists.

- Well above normal temperatures are forecast all week long with lower desert highs commonly topping out between 80 and 85 degrees.

SHORT TERM /TODAY THROUGH MONDAY/

An unseasonably strong ridge of high pressure currently centered over Arizona will gradually weaken and shift to the east by Monday. H5 heights well above the 90th percentile of climatology today will help to boost temperatures further with most lower desert locations topping out in the lower 80s this afternoon. NBM guidance indicates a 70% probability of Phoenix tying the daily record of 83 degrees today and just over a 50% probability of breaking the record. Breezy easterly winds today will provide some downslope warming and this may even lead to some locations reaching 85 degrees. For reference, the earliest first 85 degree day for Phoenix occurred on January 19, 1971, but the 30-year normal is not until March 6th. Higher level clouds are expected to begin to shift into the region from the west this afternoon, but they are likely to be too late to hinder heating today.

As the ridge pushes to the east tonight into Monday, H5 heights will temporarily dip down to around 576dm on Monday. The lower heights in addition to high clouds persisting across the region will help to push temperatures back into the upper 70s for the lower deserts.

LONG TERM /TUESDAY THROUGH SATURDAY/

The rest of the coming week should remain quiet as another Rex block develops across the Western U.S. midweek. Even though this blocking setup will not last all that long (2-3 days), the ridge is forecast to strengthen quickly and reach near climatological record strength across western Montana, Idaho, and eastern Oregon. H5 heights for our region are likely to reach 582dm again by Wednesday, adding to the unseasonably warm temperatures already in place. Highs are expected to reach into the lower 80s for many lower desert locations on Tuesday before peaking on Wednesday between 81-85 degrees. Easterly downsloping winds should also start to kick in by Wednesday potentially pushing temperatures well into the 80s.

An upstream Pacific trough is then seen moving toward the Pacific Northwest on Thursday and this will help to break down the Rex block. A weak cut-off low that forms on Tuesday west of Baja should also slowly move northeastward into at least western portions of our region Thursday into Friday, but guidance continues to show little if any weather impacts. Moisture advection is expected to be quite low and any forcing is likely to be limited, so PoPs remain well under 10% for Thursday and Friday. The only real impact is likely to be an increase in easterly winds with some areas across eastern and south-central Arizona potentially seeing gusts up to 30-35 mph Thursday morning. The decaying cut-off low may end up eventually getting mostly absorbed into the incoming Pacific trough, but there is still a good amount of uncertainty with the eventual evolution of the two systems. For now, due to the lack of expected moisture, rain chances remain quite low through next weekend. The breakdown of the ridge should at least allow for some cooling late in the week with the NBM showing lower desert highs mostly falling back into the upper 70s.

AVIATION

Updated at 1100Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation weather concerns expected throughout the TAF period. Easterly winds will prevail throughout the entire period, with some periodic gusts near 20 kts from late this morning through early this afternoon at KPHX and KIWA. Clear skies this morning will give way to increasing high cirrus cloud decks this afternoon and evening.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather concerns expected throughout the TAF period. Winds will fluctuate between the west to north at KIPL and northwest to north at KBLH with speeds aob 7 kts. Clear skies early this morning will give way to increasing high cirrus cloud decks later this morning through this afternoon.

FIRE WEATHER

Well above normal temperatures and dry conditions will persist over the next several days. Humidities will remain quite low with with afternoon minRHs commonly between 12-20% range areawide. Overnight recoveries will remain fair to poor with humidities mostly topping out in a 35-55% range. Breezy east winds will again be seen this morning into early afternoon, particularly affecting higher terrain and ridgetops of the eastern districts with gusts locally up to 20 to 25 mph. Light winds with typical diurnal tendencies return Monday. The weather pattern will again support breezy daytime conditions mid to late week.

CLIMATE

Phoenix, AZ Daily Record High Temperatures.

2/1 83 (2003) 2/2 82 (2025) 2/3 86 (2025) 2/4 86 (2025) 2/5 87 (1963)

PSR WATCHES/WARNINGS/ADVISORIES

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