textproduct: NWS Phoenix

KEY MESSAGES

- Strong high pressure over the Southwest will result in very warm temperatures and minor HeatRisk this week with afternoon highs more than 15 degrees above normal.

- Daily record highs and warm lows may be tied or broken in Phoenix, Yuma, and El Centro over the weekend.

- Dry, tranquil weather will persist through early next week.

SHORT TERM /Today through Thursday/

The Conus pattern will be dominated by moderate amplitude longwave features over the next 72 hours; and more specifically, broad troughing over the eastern Conus and a poleward shift of subtropical ridging in the Southwest. Little to no discrepancies exist among modeling depicting H5 heights steady in a 582-585dm range, or nearing the 99th percentile of late February climatology. While occasional patchy cirrus will stream inland cresting the ridge axis, this should have almost no impact on daily highs as thermal warming of the lower levels and seasonally deepening mechanical mixing dominates. Ensemble guidance spread remains extremely narrow yielding excellent forecast confidence of temperatures warming better than 15F above normal, and beginning to flirt with daily records by Thursday.

LONG TERM /Friday through Monday/

Essentially nothing will change in the synoptic pattern through the weekend as the stable Conus longwave pattern holds steady. If anything, H5 heights may locally edge higher (closer to 588dm at times) while sfc-H8 thermal profiles continue to warm. Model guidance continues to forecast H8 temperatures peaking around +20C over the weekend easily resulting in afternoon highs above 90F across lower desert communities. Guidance spread also remains unusually narrow with probabilities of exceeding daily records well above 50% over the weekend. Widespread minor HeatRisk will expand even into higher elevations with afternoon readings exceeding 20F above normal. The trend among the vast majority of ensemble membership during the first half of next week shows some form of troughing with lowering heights entering the SW Conus, however specific timing and orientation of any incoming negative height anomalies is very uncertain. Regardless, forecast confidence is moderately good regarding temperatures retreating from record levels as at least minor height falls enter the region.

AVIATION

Updated at 1146Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation weather concerns are expected through Wednesday morning under FEW to SCT high cirrus. Winds will follow familiar diurnal trends, with speeds generally aob 7 kts and periods of light variability.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather concerns are expected through Wednesday morning under FEW to SCT high cirrus. Winds will favor the W/NW at both terminals through most to the TAF period, with speeds aob 7 kts and periods of light variability. A SE'rly wind is expected for a period at KBLH early this evening.

FIRE WEATHER

Warm and dry conditions will continue the remainder of the week with temperatures well above the seasonal normal. Minimum afternoon humidity levels will generally fall into the teens across lower deserts, and into a 20-25% range at higher elevations. This will follow fair to good overnight recovery of 30-60%. Wind speeds will remain fairly light with just modest afternoon upslope gusts. Overall conditions will be favorable for early spring prescribed burning operations.

CLIMATE

Daily High Temperature Records:

Phoenix Yuma El Centro --------- --------- --------- 2/25 92 (1921) 95 (1986) 94 (1986) 2/26 91 (1986) 96 (1986) 95 (1986) 2/27 92 (1986) 95 (1986) 96 (1986) 2/28 89 (1986) 97 (1986) 92 (1986) 3/1 89 (2016) 93 (1986) 91 (2016) 3/2 90 (2016) 94 (1910) 92 (2016)

PSR WATCHES/WARNINGS/ADVISORIES

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