textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion.

KEY MESSAGES

- A pronounced warming and drying trend will occur over the next several days as strong high pressure builds over the region, pushing temperatures to above normal starting Thursday.

- Hot temperatures will develop over the region by the weekend with lower desert highs topping 100 degrees as early as Friday before peaking at just over 105 degrees by early next week.

SHORT TERM /TODAY THROUGH THURSDAY/

The weather system that brought much cooler air into the region along with some isolated rainfall is slowing exiting to the southeast. Drier air has already started to work its way into the area from the north and this will keep skies clear to mostly clear at least in the short-term. A high amplitude upper level ridge is also edging into the Pacific Northwest and much of California. This feature is forecast to slowly move into our region from the northwest starting Thursday. The cool air mass currently in place will begin to modify already today with highs reaching into the mid to upper 80s, but more so starting Thursday as the high pressure ridge starts to influence the region. The rapidly rising heights starting Thursday is expected to push readings to as warm as the upper 90s across the Lower CO River Valley and southeast California to 92-95 degrees in the Phoenix area.

LONG TERM /FRIDAY THROUGH TUESDAY/

A noticeable shift in the weather pattern late this week and lasting through at least the first part of next week will lead to any weather systems tracking across southern Canada into the North-central and Northeastern U.S. Upper level ridging will also slowly take over across much of the Western U.S. and eventually into the Southern Plains by early next week. The first ridge that will move into our region late this week is expected to weaken somewhat, but another even stronger ridge is favored to build in from the west over the weekend and last through at least the first part of next week. H5 heights are seen rising to between 582-585dm this weekend before likely peaking between 588-591dm next Monday. Forecast uncertainty increases a bit going into the middle of next week as there are some discrepancies with a weak cut-off low that may develop west of Baja. However, for now this feature may end up being too weak to have much influence over our region later next week.

Forecast temperatures continue to rise over the weekend into early next week with highs easily topping 100 degrees by Saturday and potentially even reaching or topping 105 degrees as early as Sunday. Widespread Moderate HeatRisk is expected over the weekend as afternoon temperatures climb to above 100 degrees. The hottest temperatures should fall on Monday and/or Tuesday with the latest NBM indicating some western lower deserts reaching 110 degrees to 105-107 degrees in the Phoenix area. This very well could result in Major HeatRisk across portions of the area for Monday and Tuesday, so Extreme Heat Watches/Warnings may eventually be needed. Skies are likely to stay fairly clear through at least Monday, but some higher clouds may finally make their way into the region by next Tuesday or Wednesday depending on what happens with the potential cut-off upper level low. Models do mostly favor the ridge breaking down during the latter half of next week likely leading to a cooling trend. Despite this, above normal temperatures should persist as highs look to stay close to 100 degrees late next week.

AVIATION

Updated at 1057Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation weather impacts expected through the next 24 hours, with light diurnal winds and mostly clear skies. W'rly winds may develop as early as 16-17Z today, but there will also likely be light variability through the morning that may continue through early afternoon. Wind speeds will mostly stay at or below 7 kts.

Dependent on smoke generation by the wildfire in Buckeye, W-SW winds this afternoon may pull more smoke into central portions of Phoenix and could impact slantwise visibility, especially during the late afternoon and evening timeframe.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather impacts expected through the next 24 hours, with light winds favoring seasonal diurnal trends and with mostly clear skies. Extended periods of variability are expected at both terminals, including most of the day at KIPL. Wind speeds otherwise will mostly stay at or below 7 kts.

FIRE WEATHER

A rapid warming trend over the next several days will push readings to above normal by Thursday and to well above normal starting this weekend. Humidities will also quickly lower over the next couple of days with MinRHs reaching 15-25% today to around 10% starting Thursday. However, despite the drier and warmer conditions, winds will be fairly light with only periodic upslope gusts in the mid teens through Thursday. Breeziness should pick up more Friday into the weekend with gusts to around 20 mph expected. Although conditions for critical fire weather will not be met, single digit MinRHs and well above normal temperatures by this weekend may produce some areas of elevated fire danger.

PSR WATCHES/WARNINGS/ADVISORIES

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