textproduct: NWS Phoenix

UPDATE

06Z Aviation Discussion

KEY MESSAGES

- Temperatures will cool through the weekend reaching below normal levels for several days early next week.

- Unusually strong winds will impact the region through Sunday resulting in areas of blowing dust and critical fire weather conditions.

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

SHORT TERM /Today through Monday/

Pronounced negative height anomalies have become established over the Great Basin early this afternoon as additional shortwave energy plunging into the Pacific NW will further add to the depth and magnitude of troughing across the western Conus over the next 48 hours. Into Arizona, seasonally rare midlevel height falls combined with the tightened pressure gradient and unusually intense zonal jet component will yield a continuation of strong, gusty winds through Sunday. However through the beginning of next week, heights aloft will stabilize while the pressure gradient slowly weakens allowing winds to gradually relax. While speeds fall below advisory thresholds by this evening (with the exception of far SW Imperial County), afternoon gusts will be still be sufficient when combined with low humidity levels and extremely dry, receptive fuels to support highly elevated to critical fire weather conditions. Hence, the Red Flag Warning continues across eastern districts Sunday, while elevated fire danger persists elsewhere and through the daylight hours Monday. Otherwise, with H5 heights falling below 582dm early next week and markedly drier air surging into the region, confidence is excellent that temperatures will hover 5F-10F below normal by Monday including morning lows in the 60s and 70s, and lower elevation afternoon highs barely eclipsing 100F.

LONG TERM /Tuesday through Saturday/

Once the Pacific trough settles over the Western CONUS negative height anomalies will remain in place over the Desert SW through early to mid week at the latest. The negative height anomalies will keep temperatures between 98F-103F or around 4F-7F below normal for this time of year. In fact, the June 30th forecast for Yuma and El Centro suggests highs not even reaching 100F, which has occurred on only a handful of days in the period of record for these cities on the last day of June. Guidance shows temperature beginning to climb back towards normal by Thursday as the trough begins to be displaced by the subtropical high building to the region's SE, returning H5 heights to near seasonal normal. By the next weekend afternoon highs will yet again be in the 105F-110F range.

AVIATION

Updated at 0607Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: The main aviation concern will be another round of gusty conditions. Gusts between 20-25 kts will develop by 18Z this morning, lasting through the evening. mostly diurnal trends, however a slightly earlier transition out of the west, as early as 15Z at KPHX and periods of southerly cross winds during the transition period. With elevated winds regionwide, lofted dust may have some minor slantwise visibility impacts, but no surface reduction are anticipated. Skies will be mostly clear through the TAF period.

Southeast California/Southwest Arizona including KIPL and KBLH: Strong winds will continue to be the main aviation concern during the next 24 hours. Winds will be relaxed for the overnight period, enough to the point where KBLH may see a period of VRB conditions, but gusts around 25 kt are expected to push toward and potentially even past sunrise at KIPL, though they should become more intermittent. These enhanced gusts will have the potential to generate areas of dust that would impact slantwise and even surface VIS at times. Other than the dust, skies will be clear through the TAF period.

FIRE WEATHER

Elevated to critical fire danger will continue due to low humidity, very warm temperatures, afternoon upslope/upvalley breezy conditions, and very receptive dry fuels. Red Flag Warnings remain in effect through Sunday for much of the area. Expect MinRHs to stay close to 5-15% for the next several days. Winds will increase this evening with gusts in the 20-35 mph range and locally higher over higher terrain areas. Winds are likely to peak on this evening with gusts commonly reaching 25-40 mph. These windy and dry conditions will combine with the very dry fuels to create a risk of extreme fire behavior. Temperatures will cool this weekend reaching slightly below normal levels starting Sunday and lasting into early next week. Winds are expected to gradually diminish Monday and Tuesday.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Wind Advisory until 11 PM MST this evening for AZZ530-533.

Red Flag Warning until 8 PM MST Sunday for AZZ133.

CA...Wind Advisory until 11 PM PDT this evening for CAZ564>567-569- 570.

Wind Advisory until 11 PM PDT Sunday for CAZ562.