Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
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858 FXUS65 KPSR 061710 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 1010 AM MST Wed Nov 6 2024 .UPDATE... Updated Aviation && .SYNOPSIS... An active weather pattern will help keep temperatures in a below to near normal range through the next 7 days, with generally dry conditions prevailing. As a low pressure system dives south into the Desert Southwest, breezy to locally windy conditions are expected today, particularly along the Lower Colorado River Valley and over portions of Southeast California. This system will be capable of producing overall light precipitation amounts for the Eastern Arizona high terrain through Thursday. && .DISCUSSION... Satellite imagery and objective analysis depict a potent upper level low diving south southwest at this hour, currently centered over eastern Utah. This is the system that will be responsible for ushering a colder air mass into the region over the day today, as well as bringing widespread breezy to locally windy conditions. The strongest winds today will be focused over the Lower Colorado River Valley and portions of SE CA, with northerly gusts to between 35-45 mph. This is supported by ensemble and Hi-Res guidance, which advertises 850 mb flow upwards of 30-35 kt, peaking sometime this morning over the western CWA. As such, A Wind Advisory will be in effect through this evening for locations along the Lower Colorado River Valley and zones just to the west. Another Wind Advisory segment has been added to capture the Yuma Area and Southeastern Imperial County including Glamis, though Advisory-level (40+ mph) gusts are only expected to pick up there after sunrise and last into early this afternoon as the pressure gradient slackens over the course of the day. Moisture availability with this system will be lacking (South-Central AZ PWATs peaking around 0.4-0.5") resulting in near zero rain chances across lower elevation areas. However, the dynamics of this system, along with orographic assistance, may be enough to squeeze out some showers over the eastern Arizona high terrain through Thursday, resulting in overall light accumulations. Another aspect of this system will be the much colder air parked over the region, as the upper low settles over eastern AZ later today and lingers through Thursday. At the center of the low, NAEFs and ENS mean 850-700 mb temperatures are below the 1st percentile of climatology. As the position of the low has trended slightly further south in the latest model runs, the most recent NBM now advertises that some of the higher elevation desert communities east of Phoenix will have a decent chance at seeing freezing temperatures (overnight lows in the lower 30s). A Freeze Warning has been issued for the high terrain east of Phoenix including the communities of Globe/Miami and San Carlos, valid midnight tonight through 9 AM MST Thursday morning. Lower desert highs through the end of the work week will range mostly in the 60s to lower 70s, with Thursday shaping up to be the coolest day. By Friday, the upper low will have shifted east of Arizona, and heights aloft will begin to rebound to near average for this time of year. Weak ridging is still depicted by ensembles over this weekend, with potentially a weak disturbance passing over the area that will act to keep heights aloft from increasing much above average. As a result of this evolution, a gradual warming trend should carry us through the weekend, with near normal highs in the upper 70s to lower 80s by Sunday and into early next week. Beyond Monday, guidance begins to diverge, with another trough expected to enter the western US. Cluster analysis reveals considerable uncertainty with respect to how progressive this next trough will be and how much it will deepen once it moves inland. This is reflected in the NBM temperature spread, with IQRs of around 10F Tuesday onward. Either way, the somewhat active pattern continues into next week, and PoPs for the system next week are currently quite low (no more than 20%, and only over the high terrain of the eastern CWA). && .AVIATION...Updated at 1710Z. South Central Arizona including KPHX, KIWA, KSDL, and KDVT: An extended period of northerly cross runway winds along with occasional gustiness will be the primary weather issues through Thursday morning as mid/high level cigs clear the region. Confidence is good that NE winds will prevail across the metro through the afternoon with occasional gusts up to 20 kt. There will be a tendency for wind directions to attempt to become more NW after sunset, however a period of 030v330 may be common until the early morning hours. Directional variability and multiple subtle wind shifts may impact operations later Thursday morning. Southeast California/Southwest Arizona including KIPL and KBLH: Very gusty north winds with areas of lofted dust will be the greatest weather concerns through Thursday morning under mostly clear skies. North gusts will increase through the afternoon with good confidence of peaking in a 25-40kt range. While there may be some sfc visibility restrictions, lofted dust and late afternoon slantwise vsby issues seem more likely. Otherwise, gusts should relax somewhat after sunset with more modest gustiness returning Thursday afternoon. && .FIRE WEATHER... Well below normal temperatures will prevail through the end of the work week. A mostly dry weather system will dive south into the Desert Southwest today and linger through Thursday. This system will bring breezy to locally windy conditions across the western districts for much of today, with wind gusts along the Lower Colorado River Valley and portions of Southeast California to between 35-45 mph. Light shower activity will be possible across the eastern Arizona higher terrain through Thursday afternoon, but CWR for the high terrain of the eastern districts is 5% or less. MinRHs today will fall in the upper single digits up to around 15% and will mainly fall into the teens on Thursday across the lower deserts, with readings closer to 20-30% over higher terrain areas each day. For late this week into the weekend, dry conditions will persist with weak high pressure eventually pushing temperatures from below normal into the normal range over the weekend. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Wind Advisory until 8 PM MST this evening for AZZ530. Wind Advisory until 2 PM MST this afternoon for AZZ532. Freeze Warning from midnight tonight to 9 AM MST Thursday for AZZ557-558-560-562. CA...Wind Advisory until 7 PM PST this evening for CAZ564-569-570. Wind Advisory until 1 PM PST this afternoon for CAZ565. Freeze Warning from 11 PM this evening to 8 AM PST Thursday for CAZ560. && $$ DISCUSSION...Whittock AVIATION...18 FIRE WEATHER...Whittock