textproduct: NWS Phoenix

KEY MESSAGES

- Elevated flows will continue on the Salt and Gila rivers through at least early next week due to dam releases.

- Dry weather with occasional breeziness and temperatures within a few degrees of the daily normals will be common through much of next week.

SHORT TERM /Today through Monday/

Early morning objective analysis depicts the central circulation of low pressure system cutting off from the northern stream and descending into SW Arizona. A jet streak on the western periphery of this circulation will ensure additional equatorward propagation over the next 48 hours taking the cold core and synoptic ascent well into northern Mexico. In its wake, sharp high pressure ridging folded towards the Great Basin/central Rockies will promote surface pressure rises and subsident, dry air filtering into the forecast area. Periods of nocturnal/morning breezy E/NE winds will be common over portions of the area in this typical cold season pattern, however wind speeds should not be very strong or seasonally anomalous. Under the building ridge through the weekend, H5 heights will rise into a 580-584dm range allowing modest warming versus the past several days. Numerical guidance spreads are rather narrow yielding excellent forecast confidence of high temperatures within a few degrees of the daily normals while overnight lows warm several degrees above normal.

LONG TERM /Tuesday through Friday/

Hemispheric pattern amplification driven by an unusually early season sudden stratospheric warming (SSW) event will be the main story for the latter half of next week with large ensemble forecast spread persisting. For much of the week, northern stream jet energy will settle over southern Canada while weak low amplitude waves in the southern stream remain sequestered over northern Mexico. As a result, subsident ridging with nearly steady midtropospheric heights will define the pattern over the SW Conus yielding high confidence of a very tranquil, near persistence forecast carrying on from early in the week. By the end of the week, effects from disruption of the polar vortex will be manifested in poleward retrogressive ridging while deep negative height anomalies descending equatorward over the NE Conus and East Pacific. However, the specifics regarding depth, positioning, and evolution of features within the greater synoptic pattern remain highly uncertain. Recent operational models peel a notable shortwave from the east Pacific trough towards the SW Conus/northern Mexico late in the week, however this type of solution is not consistent among NAEFS and EPS members. Given the amplification phase, wide ensemble spread and large run-to-run variations are likely the next several days resulting in low forecast confidence for next weekend.

AVIATION

Updated at 0515Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Winds will exhibit a E/NE direction through the entire TAF period with speeds generally aob 10 kt through the period. Some occasional gusts in the upper teens are possible tomorrow afternoon. FEW-SCT clouds aoa 7-8 kft will continue through tomorrow afternoon before skies become clear tomorrow evening.

Southeast California/Southwest Arizona including KIPL and KBLH: Winds will exhibit a N/NW component at both TAF sites through the period. Wind speeds at KIPL will be aob 10 kt and wind speeds at KBLH will be aob 13 kt through the period. Skies will remain clear.

FIRE WEATHER

Dry conditions will prevail across the region through the majority of next week with some enhanced morning ridge top and terrain gap breeziness during the beginning of the week. Minimum afternoon humidity levels will primarily fall into a 20-30% range in western districts and 30-50% in eastern districts with a tendency for drying towards the middle/end of the week. This will follow fair to good overnight recovery in western districts and good to excellent levels in eastern districts. Outside of the early week breeziness, wind speeds will be light with directional tendencies towards a northerly or easterly component.

PSR WATCHES/WARNINGS/ADVISORIES

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