textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion.

KEY MESSAGES

- Breezy conditions will continue along the Lower Colorado River Valley including portions of Southeast California and Southwest Arizona through early this afternoon.

- Dry weather returns to the area today with localized morning lows near freezing and highs slightly below normal, followed by a gradual warming trend through the upcoming workweek.

SHORT TERM /TODAY THROUGH MONDAY/

Latest mid-lvl wv imagery and 500 mb streamline analysis reveals a shortwave trough progressing through the Four Corners region this morning. This shortwave is embedded in a larger scale trough which encompasses much of the Lower 48. Very dry air is already working into the forecast area under subsident NW flow on the backside of this passing shortwave. This will result in clearing skies and the end of any rain chances for the next several days. High temperatures this afternoon will top out a few degrees below normal across southcentral AZ due to the presence of negative 500 mb hght anomalies over the eastern 2/3 of the forecast area. Readings this afternoon will range from the mid 50s to mid 60s across southcentral AZ and mid 60s to around 70 degrees across the western deserts of SW AZ and SE CA. There will still be some lingering breeziness along the Lower Colorado River Valley through this afternoon where gusts in the 20-30 mph range can be expected.

Clear skies and light winds will result in a chilly start to Monday morning as lows bottom out in the mid 30s to low 40s across the lower deserts and a few isolated spots around freezing. No freeze products are planned at this time as most of the locations that will experience a freeze Monday morning have already seen a freeze this winter. As low amplitude ridging builds over the western CONUS on Monday, temperatures will return to a near normal range with highs reaching the mid to upper 60s across much of the area.

LONG TERM /TUESDAY THROUGH SUNDAY/

Through the middle of the upcoming workweek, a ridge of high pressure will continue to amplify over the Western CONUS with 500 mb hghts maxing out around 579-581 dam on Tuesday and Wednesday. This will result in a warming trend with lower desert highs rising back into the lower 70s or around 3 to 5 degrees above normal. A series of shortwave troughs progressing through the Southern Rockies will maintain a modest sfc pressure gradient which will foster breezy conditions over the foothills and high terrain of southcentral AZ Tuesday and Wednesday mornings.

By the latter half of the week and into next weekend, a majority of EPS and GEFS members maintain ridging over the Western CONUS, however a southern stream shortwave trough may temporarily undercut the ridge during the Thursday-Friday timeframe. This weak shortwave may briefly stall the warming trend for a day or two, otherwise no sensible change to the weather is anticipated as NBM PoPS remain largely <5%. Ridging will then expand over the Desert Southwest next weekend which will allow the warming trend to recommence as lower desert highs reach the mid 70s Saturday and Sunday.

AVIATION

Updated at 1120Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Uncertainty in wind directions through this morning will be the primary weather issue under mostly clear skies. Winds have begun to shift from NW to N/NE, though decoupling has led to periods of light speed (AOB 5 kts) and some drift in directions. A period of variability may be favored instead with prevailing N/NE directions at times. Then, confidence is good that a westerly fetch will develop this afternoon, followed by an easterly switch this evening. FEW-SCT high clouds will begin to move in this afternoon and increase in coverage tonight into Monday morning. Easterly winds will increase late Monday morning, more so at KPHX than other terminals.

Southeast California/Southwest Arizona including KIPL and KBLH: Lower than usual confidence on winds at KBLH early this morning, then gusty north winds late this morning into the afternoon, will be the main aviation weather concerns. A few periods of strong (10-15 kt) sustained north winds have been observed at KBLH overnight, though periods of very light or calm winds have prevailed for the last couple hours. The surface will likely remain decoupled through 17-18Z, then north winds will increase late morning with gusts temporarily to 15-20 kts, before subsiding over the afternoon. Winds at KIPL will vary between W/NW and N but generally remain light, AOB 6 kts. Clear skies will give way to FEW-SCT and eventually BKN mid to high clouds later today into tonight.

FIRE WEATHER

As a weather system departs to the east and high pressure returns to the region, a warming trend will commence through the upcoming week. Dry air is already filtering into the region in the wake of the departing weather system this morning. Relative humidity will bottom out around 10-15% across the western districts and 15-30% across the eastern districts today and these ranges will likely continue through the first half of this week. Overnight recovery will be poor to fair over the next several nights. Northerly winds across the Lower Colorado River Valley will relax by this afternoon, however there will be some enhanced breeziness across the high terrain of southcentral AZ Monday and Tuesday morning. Elsewhere, winds will return to a more typical diurnal pattern.

PSR WATCHES/WARNINGS/ADVISORIES

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