textproduct: NWS Phoenix

UPDATE...Updated 12z Aviation Discussion

KEY MESSAGES

- Dry conditions with above normal temperatures and mostly clear skies will prevail through the middle of next week. - Periods of breezy winds will affect the Lower Colorado River Valley and higher terrain areas of south-central Arizona today into Saturday, and potentially again during the latter half of next week.

SHORT TERM /TODAY THROUGH SUNDAY/

Very dry air has settled into the region since Wednesday with PWATs near 50% of normal for late January. Any upper level moisture and clouds that we had for the first part of yesterday have been pushed southeast of the area with the help of a passing shortwave trough to our northeast. Slightly enhanced northerly flow will continue today before weakening into Saturday as upper level ridging slides eastward across the region. Clear skies will prevail today with some northerly breeziness again across the Lower CO River Valley and northeasterly breeziness over the high terrain north and east of Phoenix. Temperatures today will begin to warm with the increasing heights, pushing readings well into the mid 70s for the Phoenix area to the upper 70s across much of the western deserts. As the ridge moves fully over the region this weekend, H5 heights are forecast to rise to between 582-584dm, or above the 90th percentile of climatology. After widespread upper 70s highs on Saturday, many locations should top 80 degrees Sunday with the current forecast high of 82 degrees in Phoenix only one degree shy of the daily record. However, some increasing high clouds by Sunday afternoon have the potential to slightly affect daytime highs.

LONG TERM /MONDAY THROUGH NEXT FRIDAY/

Next week's weather looks to be much of the same with deep troughing remaining over the eastern half of the CONUS and ridging over the west. A slight dip in heights is expected Sunday night and Monday, while high clouds will continue to stream across the region. These factors should keep most areas from reaching 80 degrees on Monday, but as clouds decrease on Tuesday forecast highs show many locations likely reaching 80 degrees again across southeast California and the Lower CO River Valley.

A Rex block will also develop by the middle of next week with an anomalously strong upper level ridge developing over the bulk of the Western U.S., while a cut-off low forms just west of Baja. Ensemble guidance has been somewhat trending away from bringing the cut-off low into our region late next week or next weekend, but there is still too much uncertainty to discount it impacting our region at some point. Since guidance is now leaning more toward the ridge being fully in place later next week, forecast temperatures are trending upward. The NBM has nudged forecast highs up by around four degrees from Wednesday onward with the potential for upper 70s to lower 80s each day. Some spread is still seen in the NBM temperature guidance, but it's less then yesterday. Even if the cut-off low or its eventual remnants make its way near or into our region, the small amount of forecast moisture advection and the lack of forcing should strongly limit any rain chances next Friday into Saturday. Models also show some potential for a second cut-off low developing to our west by next Sunday or early in the following week. This second feature is showing more positive signs than the Friday/Saturday system for rain potential. The persistent blocking pattern should keep temperatures well above normal through all of next week.

AVIATION

Updated at 1105Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation weather concerns under clear skies can be expected throughout the TAF period. Winds will generally follow diurnal tendencies with speeds aob 7 kts along with extended periods of variable to even calm conditions. KPHX may temporarily switch to a light southwest wind around sunrise before shifting back to the east by the mid-morning hours.

Southeast California/Southwest Arizona including KIPL and KBLH: At KIPL, winds will fluctuate between the west to north with speeds under 10 kts. At KBLH, winds will fluctuate between the northwest to north with afternoon gustiness of around 20 kts before gusts subside by early this evening. Clear skies expected throughout the period.

FIRE WEATHER

Dry weather conditions will prevail through the next week, with MinRH values in the 10-20% range most afternoons. There will be a subtle moisture increase late this weekend into Monday, but MinRH values only increase to 20-25% at best. Overnight recoveries will remain poor to fair with humidities mostly between 30-55%. Expect another round of breeziness today across portions of the western districts and today and Saturday over the eastern Arizona high terrain. The weather pattern will again support breezy daytime conditions mid to late next week. Temperatures will warm further over the weekend with lower desert highs likely topping 80 degrees in many locations.

PSR WATCHES/WARNINGS/ADVISORIES

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