textproduct: NWS Phoenix

KEY MESSAGES

- Elevated fire danger across the Arizona high terrain will persist for another day or two with daytime breezy and very dry conditions.

- Temperatures will gradually warm through the rest of the week, but will at least stay below normal through Thursday.

- As the heat builds into the weekend and early next week it will lead to increasing coverage of Moderate Heat Risk and highs eventually reaching 110 degrees by next Monday or Tuesday.

SHORT TERM /TODAY THROUGH FRIDAY/

The anomalously strong trough over the Western U.S. will remain in charge of our weather for another couple of days keeping below normal temperatures in place. Despite the trough continuing to gradually fill today into Thursday, H5 heights will remain within the 10% percentile of climatology into tonight. Highs today will be similar to yesterday's readings, but with the western deserts warming another 2-3 degrees. H5 heights will eventually rise back into a normal range for this time of year on Thursday with temperatures rising back into the normal range by Friday. As highs warm back to around 105 degrees by Friday, overnight lows will also warm back into the 70s areawide. The warming overnight temperatures will also become more apparent once some higher level clouds start to move into the region from the southwest starting Friday. The atmosphere will continue to be very dry through the rest of the workweek with PWATs running 25-50% of normals and surface dew points mostly staying in the 20s and 30s.

LONG TERM /SATURDAY THROUGH TUESDAY/

By the weekend, the weather pattern will begin to shift with the trough energy ejecting through the Northern Plains and the broad troughing shifting northward over the Pacific Northwest and Southwest Canada. The subtropical ridge currently over the Eastern U.S. into Mexico will then begin to shift west northwestward, quickly raising H5 heights over our region by the weekend.

Another change will come from a developing tropical system which is currently around 1000 miles west southwest of southern Baja. This system will not have any direct impact on our weather, but guidance favors some of its higher level moisture and clouds working into our region from late Friday through late Saturday/early Sunday. The timing and the positioning of the clouds could still change somewhat, but as of now we are likely to see a good deal of higher clouds centered on Saturday. These clouds may help to stem the building heat over the region, keeping temperatures close to normal through at least Saturday and potentially even Sunday. The current NBM forecast highs show readings between 103-108 degrees on Saturday and 106-110 degrees Sunday, both of which are down a degree or so from previous forecast runs.

By Sunday, guidance shows the subtropical ridge consolidating and forming a new center somewhere to our east northeast. This developing ridge is expected to take a little while to really strengthen as H5 heights are not likely to reach into the 90th percentile until next Tuesday or Wednesday. Temperatures are expected to climb a bit further early next week as the ridge strengthens with 110-113 degree highs becoming very likely by Tuesday.

Moisture should also begin to improve starting around Sunday, potentially becoming meaningful for some isolated convection to begin showing up over the eastern Arizona high terrain as early as Monday. If the high becomes more established close to the Four Corners area by the middle of next week, deeper moisture may move into our area from the southeast providing more widespread convection chances. Models still differ on the timing and the extent of this deeper moisture potential, so it may take another few days to gain more forecast confidence on shower and thunderstorm potential later next week.

AVIATION

Updated at 0850Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation weather concerns under clear skies can be expected throughout the TAF period. The overall winds will follow the typical diurnal tendencies with a period of southerly winds during the late morning/early afternoon hours before the westerly shift. Some occasional afternoon/early evening gusts in the mid to upper teens can be expected.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation weather concerns under clear skies can be expected throughout the TAF period. At KIPL, winds will generally be out of the west while at KBLH, winds will fluctuate between the south-southeast to southwest. A period of light variability will be common this morning at KBLH and through early afternoon at KIPL. Some gusty sundowner winds upwards of 25 kts can be expected at KIPL early in the evening.

FIRE WEATHER

A diminishing threat of breezy to windy conditions will help to gradually lower the fire danger over the next couple of days, but very low humidities will persist through at least the weekend. Despite the diminishing wind threat, there will still be the typical afternoon upslope/upvalley breeziness with gusts reaching 20-25 mph today and 15-20 mph each day Thursday through the weekend. Afternoon minimum humidities will mostly range between 5-10% through Saturday with mostly poor overnight recoveries of 15-30%. Despite the decrease in winds later this week, seasonably elevated fire danger will persist through the weekend due to very dry conditions, seasonably warm temperatures, very dry and receptive fuels, and the typical upslope/upvalley breeziness each afternoon into the early evening.

PSR WATCHES/WARNINGS/ADVISORIES

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