textproduct: NWS Phoenix

UPDATE...Updated 06z Aviation Discussion

KEY MESSAGES

- Temperatures will continue to cool closer to normal the remainder of the week allowing moderate HeatRisk to be reduced towards a minor category.

- An approaching east Pacific weather disturbance will dry out the region, while bringing increasingly breezy conditions through the weekend.

- Strong high pressure should build back into the region by the middle of next week with increased odds of major HeatRisk impacting the area.

SHORT TERM /Today through Friday/

Early morning objective analysis suggests a consolidating mid/upper level low situated over central Arizona with a retrograding, pinched ridge over western Nevada. The westerly flow behind this low pressure system has eroded moisture through SE California, however a pool of 8-11 g/kg boundary layer mixing ratios still hovers over southern Arizona. DCape values in excess of 1500 J/kg promoted numerous outflow boundaries last evening, and just enough to locally breach notable inhibition. Further scouring of moisture over Arizona will take place today with mixing ratios falling closer to 7-9 g/kg while the mid/upper level pattern becomes more anti-cyclonic and subsident. Deep, moist convection should become relegated to higher terrain areas of eastern Arizona, potentially clipping far eastern Gila County. Otherwise, H5 heights will actually change very little over the next 48 hours, however modest cooling in the H8-H7 layer and wider diurnal spreads due to markedly drier air surging into the region will result in temperatures retreating very near the daily normals. With mixing ratios tumbling closer to 3-4 g/kg Friday, even mountain cumulus development will be completely eliminated.

LONG TERM /Saturday through Wednesday/

Ensemble member agreement remains very good through early next week advertising East Pacific troughing migrating inland and deamplifying over the Rockies. This evolution will create a dry zonal flow pattern with mixing ratios falling very close to 2-3 g/kg and total column PWATs as low as 0.25" though Monday. Forecast confidence is very good that temperatures will hover near normal through the weekend before beginning a warming trend next week as subtropical ridging builds back north. Modest height falls combined with seasonably deep mixing depths will promote repeated chances of gusty afternoon winds, and combined with the incoming dry airmass and receptive, dessicated fuels, fire danger will become quite elevated.

There is growing confidence among operational and NAEFS members that subtropical ridging will continue strengthening towards the SW Conus during the middle of next week as mean longwave troughing is established over the eastern US. H5 heights should easily rebound over 594dm with the anti-cyclone center becoming positioned either directly over Arizona or towards the international border. GEFS membership generally keeps H5 heights under 595dm while some of the more extreme CMC and EPS members are highlighting H5 heights 597- 600dm during the midweek period. Regardless, numerical guidance means strongly suggest lower elevation high temperatures by the middle of next week flirting with 115F, and it would not be unexpected for reading to breach this level. As a result, widespread major HeatRisk and extreme heat appears increasingly likely during at least the Wed-Fri time frame next week.

AVIATION

Updated at 1748Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation concerns are expected through the TAF period. Current southerly winds will shift westerly for the afternoon where another round of gusty conditions are expected between 22-03Z with speeds between 15-20 kts. Mostly clear skies today with the FEW higher clouds expected to clear up by the afternoon.

Southeast California/Southwest Arizona including KIPL and KBLH: Main aviation concern today will be gusty conditions, especially at KIPL, with speeds expected between 20-25kts. At KIPL, generally westerly winds will prevail while at KBLH, winds will generally fluctuate between the south to southwest. Winds at KIPL may be enough to reduced visibilities near 6SM but confidence is too low at this time to include in this TAF package. Otherwise clear skies are expected through the period.

FIRE WEATHER

A pronounced drying trend will continue across the region the remainder of the week with terrain induced showers/storms exiting into far eastern Arizona and New Mexico. Temperatures will cool closer to normal the rest of the week, however the much drier airmass will allow minimum humidity levels primarily in a 10-20% range to deteriorate into widespread single digits over the weekend and early next week. Correspondingly, overnight recovery will fall into a poor to fair 15-40% range. Winds will frequently become gusty the remainder of the week yielding a widespread elevated fire danger, however at this time, speeds appear to remain below critical thresholds. By the middle of next week, temperatures will warm markedly with minimum humidity levels hovering around 10-15% and continued gusty winds yielding dangerous conditions for any ongoing wildfires.

PSR WATCHES/WARNINGS/ADVISORIES

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