textproduct: NWS Phoenix

KEY MESSAGES

- Lingering breezy conditions coupled with low humidity and very dry fuels through Tuesday will result in elevated fire danger, primarily for the Arizona higher terrain.

- Below normal temperatures will prevail through much of the week.

- More tranquil conditions and a slow warming trend will arrive during the latter half of the work week.

SHORT TERM /TODAY THROUGH WEDNESDAY/

An unusually high amplitude, broad upper level trough for late June has settled over the Western US, with several shortwave impulses apparent in midlevel water vapor satellite imagery embedded within the broader trough. One of which is gradually shifting northeastward into the Northern Plains, packing heights aloft along its eastern flank to induce a fairly prominent SSW- NNE oriented jet streak. As this first shortwave departs, midlevel flow will decrease somewhat today but remain elevated, resulting in lingering breezy to locally windy conditions. A second impulse can been seen moving south along the California coast and is forecast to round the base of the longwave trough, passing just northwest of the area and then ejecting northeastward late Tuesday. This will reinvigorate midlevel flow, maintaining the widespread gusty afternoon winds on Tuesday, primarily over Northern/Eastern AZ high terrain, but not to the same extent as was observed over the weekend. The continued unusually strong synoptic winds will promote elevated fire danger over the AZ high terrain east/northeast of Phoenix through at least Tuesday, then winds taper off more notably by the latter half of the week.

Confidence remains high that broad troughing will be maintained over the Western US through much of the rest of the week, but with negative midlevel height anomalies gradually eroding and retreating northward. Ensemble mean H5 heights through early Wednesday should fluctuate within a 579-585 dam range over the forecast area, mostly between the 3rd and 10th percentiles of climatology, supporting temperatures well below normal for late June/early July. As we enter our climatologically hottest time of the year, expect afternoon highs to struggle to reach the triple digits across much of the lower deserts through Wednesday (except in urban, low-lying valley areas), between 5 and 10 degrees below daily normals. Perhaps more impressively, the column is forecast to dry out even further heading into the middle of the week with the second shortwave impulse passing north of the area, resulting in PWATS as low as 0.2-0.3" and surface dewpoint temperatures in the 20s and 30s across portions of the forecast area. Forecast lows Tuesday and Wednesday morning are in excess of 10F below daily normals for some rural lower desert communities, cooling well into the 60s.

LONG TERM /THURSDAY THROUGH SUNDAY/

Ensemble model guidance remains in good agreement on the overall synoptic pattern starting to shift by the latter half of this week. They show high pressure slowly starting to push back into the Desert Southwest from the east and the Pacific trough lifting north/northeastward. As a result, H5 heights aloft will start to increase leading to a gradual warming trend. The latest NBM has temperatures returning to near to slightly below normal by the end of the workweek. The high pressure will continue to push into our region next weekend with H5 heights aloft continuing to rise. The NBM has afternoon high temperatures going back above normal by the end of the weekend, with highs in the 105-110 degree range.

With high pressure slowly building back into our region more tranquil weather conditions are expected with only some minor afternoon breezy conditions expected with the highest winds across the Lower CO River Valley and the higher terrain north and east of Phoenix. Very dry conditions will also remain in place and thus there will be no rainfall chances through this weekend.

AVIATION

Updated at 1700Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No significant weather concerns will exist through Tuesday afternoon under clear skies. Confidence is good that a brief period of southerly cross runway winds early afternoon will veer to W/SW with occasional gusts 15-20kt through mid evening. Behavior of wind shift timing and speeds will be nearly identical to the past 24 hours tonight and Tuesday.

Southeast California/Southwest Arizona including KIPL and KBLH: No major weather issues will exist through Tuesday afternoon under clear skies. Southerly winds will be preferred at KBLH while a west component more common at KIPL. Confidence is good that late afternoon/evening gusts 20-25kt will affect the region, and much weaker than the past few days. An extended period of light and variable winds will be possible around sunrise Tuesday morning.

FIRE WEATHER

Elevated fire danger, and locally near critical for the high terrain of the eastern district, will continue through Tuesday due to low humidity, very warm temperatures, breezy southwest winds during the afternoons/early evenings, and very receptive dry fuels. Afternoon minimum humidities between 7-15% through Tuesday will drop to a 5-10% range for the eastern districts beginning Wednesday and areawide by Friday. Poor to fair overnight recoveries between 20-45% through Wednesday night will decrease into a 15-30% range Thursday night onwards. Winds will diminish more noticeably during the latter half of the work week, but afternoon/early evening upslope and upvalley gusts to 15-25 mph will continue. Temperatures will remain below normal through the majority of the week, with lower desert highs around 100F through midweek, then gradually warming into a near normal range this weekend.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...Wind Advisory from 5 PM this afternoon to 8 AM PDT Tuesday for CAZ562.