textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion.

KEY MESSAGES

- Persistent strong high pressure over the region will lead to well above normal temperatures through the next week, with lower desert highs pushing into the upper 80s to lower 90s by Wednesday.

- Dry conditions, with no rain in the forecast, and light winds most days will persist through the next week.

SHORT TERM /TODAY THROUGH TUESDAY/

The 24-hr temperature change at midnight/early this morning was around 5-10 degrees warmer across most of the region. High pressure ridging has built in over the region very quickly, which has led to the warming. Heights at 500mb are already up to 580-581dam, a 24-hr rise of 16-17dam. In addition to the atmospheric warming, an influx of high clouds may somewhat inhibit radiational cooling this morning. There is also a tightening pressure gradient this morning, as a result of a strong surface high in Colorado, which will lead to an increase in easterly winds across south-central AZ and may also keep temperatures a touch warmer this morning in some spots. Low temperatures this morning are expected to be roughly 10 degrees warmer than yesterday morning. With the tightened wind gradient, there will be some breezy conditions this morning, especially after sunrise, with lower desert gusts as high as 20-25 mph, and 30-35 mph in the higher terrain east of Phoenix. Winds will gradually subside through the early afternoon and the high clouds should clear out through mid to late morning, allowing for mostly sunny skies this afternoon. Highs today will, similar to the lows, be around 10 degrees warmer than yesterday, with lower deserts reaching the lower 70s to upper 80s.

To start the workweek, Monday and Tuesday, the atmosphere will continue to warm as a 582-585dam ridge persists over the region. High temperatures Monday are forecast to reach the low to mid 80s and then mid to upper 80s Tuesday. Morning low temperatures will also continue to warm, with mostly upper 40s to middle 50s across the lower deserts to start the week. As afternoon temperatures push into the 80s, HeatRisk levels will increase to the Minor category. There will likely be some lingering easterly breeziness Monday morning across south- central AZ, but with overall lighter wind speeds and gusts than this morning. Light winds are then expected Tuesday as the strong surface high to the northeast breaks down and the pressure gradient falls apart. Very dry conditions are expected the next 3 days, with humidity levels down to 10-15% in the afternoons.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Warming will continue through the middle of the week, despite a very brief dip in H5 heights Wednesday as a trough passes through the NW CONUS and into the Plains. Global ensembles unanimously show H5 heights staying around 582-585dam through the end of this week and end of the month. Temperatures at 850mb are forecast to reach up to 17-19C by mid to late week and 850mb temperatures of this magnitude are more common for late April and early May. High temperatures in the upper 80s to around 90 degrees is normal for late April and early May and that is precisely what is in the forecast. Latest NBM has forecast highs reaching the upper 80s to lower 90s Wednesday-Thursday and then widespread low 90s Friday through next weekend, with some communities, like Yuma, AZ and El Centro, CA pushing 95 degrees.

Both high and low temperatures will be pushing daily records late this week and next weekend. Daily record highs in Phoenix for the end of February are around 89-92F (see CLIMATE section below) and 92F is also the record highest February temperature. So, there is even a decent chance of setting a new monthly record in Phoenix. The midnight run of the NBM has a forecast high of 92F in Phoenix on the final two days of February with around a 75% chance of 92F or higher. Widespread Minor HeatRisk is expected through the next 7 days. This heat will pose a health risk if you spend extended time outdoors in the afternoon without breaks from the sun and/or proper hydration. Besides the coming heat, the atmosphere in the Desert Southwest will remain dry through the next week and winds will generally be light with occasional late morning and afternoon breezes. Guidance does show signs of the ridge flattening out some by the end of next weekend, and the overall model spread increases, but global ensemble clustering shows the majority of ensemble members still favor positive H5 height anomalies through at least the first few days of March. This would favor continued above normal temperatures and drier unfavorable rain chances.

AVIATION

Updated at 1720Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

No aviation weather concerns under morning high level clouds. Some easterly gusts in the upper teens are likely to continue through the early afternoon hours. Afterwards easterly winds will remain dominant through the TAF periods with speeds generally aob 10kts.

Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation weather concerns under morning high level clouds can be expected throughout the TAF period. Winds will generally be out of the west to northwest with periods of light variability this evening. Wind speed will generally be aob 7 kt.

FIRE WEATHER

Dry conditions will persist through the next week, with temperatures warming rapidly through the first half of the week. Besides a small uptick in moisture during the middle of the week, MinRH values will be around 10-20% and overnight recoveries will be around 35-50% each day. Afternoon high temperatures will go from low to mid 80s Sunday through Tuesday to upper 80s to low 90s Wednesday through next weekend, pushing 15-20 degrees above normal. Winds will be light with an occasional afternoon breeze and follow typical diurnal directional patterns most days over the next week. There will be an uptick in easterly winds this morning across south-central AZ, with general winds up to 10-15 mph and gusts up to 20-25 mph across lower elevations (below 3000') and a bit higher over higher elevations, up to 15-25 mph sustained with gusts up to 30-35 mph. There may be another uptick in easterly winds at the end of next week, but forecast confidence is currently low. There is no precipitation in the forecast through next week.

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)

PSR WATCHES/WARNINGS/ADVISORIES

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