Marine Weather and Tide Forecast for Glendale, AZ

Key Messages

1) Gusty winds over the weekend resulting in a locally elevated fire danger

2) Increased odds for above normal temperatures and widespread Moderate HeatRisk returning late next week...

DISCUSSION
Weather Pattern Overview:

Broad, weakly cyclonic flow lingers over the SW Conus as a closed, occluded low pressure system lifts into the Upper Midwest. The weakness left in the midtropospheric flow over the forecast area from this exiting system will quickly be filled over the weekend by a series of Pacific negative height anomalies intensifying into an amplified longwave western trough. The magnitude of the attendant Pacific jet during this meridional transition will ensure robust shortwave energy and notable height falls migrate into much of Arizona. The timing and juxtaposition of height falls and jet core carving out the trough base will support very gusty winds throughout the weekend, but particularly Saturday afternoon/evening across SE California where parameters align nearly optimally. As such, advisories will almost certainly be necessary in the typical wind prone locations of Imperial County. These gusty winds combined with seasonally low humidity values will also result in an elevated fire danger, though more limited wind speeds in south-central Arizona Saturday and higher moisture sweeping through the region Sunday may preclude more critical conditions.

Ensemble membership remains in good agreement depicting several vorticity centers pivoting through the longwave trough with one notable and final trailing wave digging into northern Arizona Monday. Given the inland trajectory of this entire series of shortwaves, moisture will be extremely limited with boundary layer mixing ratios never exceeding 5 g/kg. However, given the unusual depth of the trough and magnitude of the cold core, a few showers may be squeezed out over higher terrain areas. On the other hand, recent operational models have shifted the jet streak and cold core slightly further north resulting in a forecast of a large midlevel capping inversion locked over the southern half of Arizona. If this model trend comes to fruition, it would be all but impossible for anything other than outflow winds to propagate into lower elevations.

While some subtle midlevel weakness in the height field may hold over the Southwest during the latter half of the week, ensembles are far more resolute in building stronger ridging over northern Mexico and SW Conus. Some of the more extreme members have been highlighting H5 heights around 594dm, however the preponderance of output suggests heights closer to 588dm. As a result, widespread moderate HeatRisk should evolve towards the end of next week with temperatures nearly 10F above normal. Should any of the more anomalous solutions be realized (and it could be argued that would be a likely outcome given the pattern progression), this could be the first vestiges of major HeatRisk with temperatures 15F above normal yielding extreme HeatRisk over the holiday weekend.

Forecast Confidence & Deviations:

Good confidence in temperature forecasts exists the next couple days, but then deteriorates significantly early next week depending on how far south the cold core migrates. Mandated NBM forecasts have bumped warmer based mainly on changes in the operational members, but could flip flop back based on future model iterations. Feel the automated NBM winds over the weekend are somewhat underforecast and have made some minor increases during peak mixing hours. Spurious POP and QPF grids were substantially reduced this cycle, however did have to make some minor adjustments based on unrealistic model artifacts. Average confidence exists with respect to temperatures towards the end of this forecast period, but would not be surprised if actual readings were even warmer than the current automated NBM output.

AVIATION
Updated at 2341Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT; Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation impacts are expected through the next 24 hours. Winds at all terminals will follow typical diurnal trends, with speeds remaining at or below 10 kts through most of the TAF period.
Afternoon gustiness can be expected in the Phoenix area, with gusts up to 15-20 kts at times. Clear skies will prevail.

FIRE WEATHER
With dry conditions prevailing through next week, winds will increase in speed over the weekend yielding an elevated fire danger with locally near critical conditions. MinRHs will mostly fall in a 10-15% range through Saturday before a cooler and somewhat more moist airmass keep minimum readings in a 15-25% range Sunday and Monday. Poor to fair overnight recovery of 20-50% will improve closer to a 35-60% range early next week. Winds will be most pronounced in western districts Saturday with gusts 30-40 mph, then translating into eastern districts Sunday albeit with somewhat weaker speeds. Very warm and dry weather will return during the middle of next week, however wind speeds will be much weaker as high pressure starts building into the region.

PSR WATCHES/WARNINGS/ADVISORIES
AZ...None.
CA...None.