Marine Weather and Tide Forecast for San Luis, AZ

SYNOPSIS
Gusty winds and elevated to locally critical fire weather conditions will be the main weather concerns through Tuesday, as a low pressure system passes over the Great Basin. Temperatures will also cool from the upper nineties this afternoon to the eighties across much of the lower deserts by Tuesday. Tranquil conditions return Wednesday, with typical afternoon breezes and a gradual warming trend to near seasonal normals during the latter half of the workweek.

DISCUSSION
Early afternoon mid-level wv imagery shows a trough moving onshore over the Pacific Northwest, with notable height packing evident in 500 mb RAP analysis to its southeastern periphery. Mountain wave activity in the lee of the Sierras is quite apparent, indicative of the strong southwesterly flow that is expected to shift over the forecast area over the next 12-24 hours as the trough digs into the Great Basin. While the stronger flow aloft is expected to bring breezy to windy conditions across portions of the area as early as this afternoon, the region still remains under the influence of high pressure and positive H5 height anomalies today. Abundant high clouds may limit afternoon highs from reaching the century mark across much of the lower deserts, but temperatures will still range from 4 to 8 degrees above normal this afternoon, mostly in the upper 90s.

As mentioned above, strong winds will be one of the primary impacts from the incoming dry weather system through Tuesday. Wind gusts of 25-40 mph are expected across the area, mainly during the afternoons and evenings. The strongest winds will be focused across southeastern CA and over the AZ high terrain. A Wind Advisory remains in effect for much of Western Imperial County through Tuesday night, to capture the areas most prone to mountain rotor activity and downsloping winds. Though there will likely be a lull in stronger gusts early Tuesday morning, most guidance including GFS/NAM MOS for Imperial show sustained wind speeds remaining around 25 kts, just under the Advisory threshold, so have opted to maintain previously issued product without splitting it up. Strong winds combined with low relative humidities between 8-15% and dry fine fuels will lead to elevated to locally critical fire weather conditions as well. Therefore, a Red Flag Warning remains in effect for southern Gila County and the higher elevations of northeastern Pinal and eastern Maricopa Counties through 7 PM MST this evening and again Tuesday from the late morning through early evening.

The other impact of this system will be cooler temperatures. Expect lower desert highs to fall solidly in the 80s over SE CA and SW AZ Tuesday and close to 90F for portions of the Phoenix Metro Area, then 80s areawide Wednesday (70s for populated higher terrain areas like Globe/Miami, and western JTNP.) These cooler temps are around 3 to 6 degrees below normals for the time of year.

Late week, global guidance still depicts some measure of longwave troughing/quasi-zonal flow being maintained over the Western US, with H5 heights gradually rebounding to around 576-579 dm. Latest NBM probabilistic guidance shows a very narrow IQR in forecast temperatures, so confidence is quite high that temps will return to near seasonal levels. This upcoming weekend, ensembles still show a shortwave carving out the western side of the longwave trough/quasi-zonal pattern over the Western CONUS. Though there are notable discrepancies in how far south this trough will dive, it will likely result in another cooldown to below normal and breezy to locally windy conditions this upcoming weekend.

AVIATION
Updated at 2350Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT: Westerly winds with gusts reaching 20-25 kts will prevail through this evening at all Phoenix Metro terminals. Gusts will diminish by 05Z-06Z tonight with speeds remaining elevated around 8-11 kts overnight. It is likely that winds will not switch back to the east overnight and instead remain S-SW. Tuesday will be very similar to today with gusts returning to all TAF sites after sunrise and persisting through the early afternoon. SCT to BKN high clouds will continue to overspread the region.

Southeast California/Southwest Arizona including KIPL and KBLH: Gusty winds and the potential for localized blowing dust will continue to be the primary aviation concerns at the SE California terminals through this evening. Gusts will continue to reach 25-30 kts at both terminals through late tonight, but there could be a period of stronger gusts around 35 kts at KIPL after sunset. These strong gusts may result in local surface and slantwise visibility restrictions due to blowing dust. SCT-BKN high clouds will continue overnight before clearing out early tomorrow mornings.

FIRE WEATHER
Elevated fire danger will exist today and Tuesday as warm temperatures, low humidity levels, and gusty winds become juxtaposed with receptive, dry fine fuels. MinRHs of 8-15% will be common throughout the week following poor to fair overnight recovery of 20- 50%. Winds will gust to between 25-40 mph during the afternoon and early evening today and Tuesday, some higher gusts are possible in western Imperial County. Gusts will likely be most pronounced across ridge tops and in the typical downsloping areas. Speeds should weaken during the latter half of the week, though still will retain the usual afternoon upslope gustiness. Temperatures will also cool during the first half of the week as the weather system moves into the region, however should rebound closer to seasonal normals by the end of the week.

PSR WATCHES/WARNINGS/ADVISORIES
AZ...Red Flag Warning until 7 PM MST this evening for AZZ133.

Red Flag Warning from 10 AM to 8 PM MST Tuesday for AZZ133.

CA...Wind Advisory until 5 AM PDT Wednesday for CAZ562.

Wind Advisory until 2 AM PDT Wednesday for CAZ563-566-567.