Area Forecast Discussion
Issued by NWS Phoenix, AZ

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057 FXUS65 KPSR 232121 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 222 PM MST Thu Feb 23 2017 .SYNOPSIS... Dry weather with below normal temperatures will continue through Saturday. However, two fast moving weather disturbances are forecast to move into the region Sunday and again Monday night. The weather system Monday night will have better potential for spreading rain showers across the region. Drier and eventually warmer weather will return to the area by the middle of next week. && .DISCUSSION... Tonight through Saturday... In the wake of a dry cold front last night, a cooler airmass will continue to settle over the region through Saturday. Under mostly clear skies and much lower dewpoints, temperatures will be much cooler than normal, but a little warmer on Saturday. Light winds. Sunday through Tuesday... A couple of Pacific storms are still forecast to move into the region this period, generally one Sunday and another Monday night. However, a very complex Rex Block pattern continues over the eastern Pacific, so daily model run solutions for Sunday and Monday night continue to waver slightly, with adjustments to timing, intensity and precipitation amounts. For example, the European model is now much wetter than the GFS for Monday night in south central AZ, including Phoenix. And, what complicates precip forecasts in south central AZ is the increasingly moist southern branch jet stream, from just north of Hawaii, that is forecast to merge with the northern branch jetstream over the area. For now the Sunday system will be relatively dry, but a good chance of showers will continue generally from the Colorado River Valley eastward on Monday night. Wednesday and Thursday... Dry weather with near normal temperatures are forecast this period. && .AVIATION... South-Central Arizona including KPHX, KIWA,and KSDL: High-Res model output continues to show isolated-scattered showers/thunderstorms developing over the eastern portions of the Greater Phoenix area through about mid-morning today as the upper low that has brought the moisture to the region moves off to the south and east. However, confidence on any shower activity actually affecting a particular terminal is not high enough at this time to include anything more than VCSH in the TAFs. Cigs could briefly dip as low as 8k feet in any showers that do develop, but should remain, for the most part, aoa 10k feet. Cigs/shower chances to lift/end this afternoon and evening as the upper low moves off well to the east. Winds to remain easterly until late afternoon, then briefly shift to light westerly to northwesterly during the late afternoon/early evening hours before reverting back to easterly direction during the mid-late evening hours. Southeast California/Southwest Arizona including KIPL and KBLH: High pressure building into the region to bring mainly clear skies to both KIPL and KBLH through most of the taf period, with perhaps a bit of high cirrus moving into the region late tonight. Winds to remain mainly out of a westerly to northwesterly direction at KIPL and out of a northerly direction at KBLH through the taf period, with speeds mainly aob 12 kts. Aviation Discussion not updated for amended TAFs. && .FIRE WEATHER... Saturday through Wednesday... Dry conditions, but increasing clouds are expected for most areas through early Sunday as a mostly dry weather system passes by to the north. A second weather system is likely for Monday into Tuesday with better chances of wetting rains, especially across the high terrain of Arizona. Below normal temperatures are expected through the entire period. Breezy conditions early Sunday and again on Monday are expected in most areas with breezy conditions persisting down the Lower Colorado River each afternoon through Wednesday. Humidities will start out dry on Saturday, but improve through early next week with minimum readings as high 35 to 40% on Monday. Gradual drying thereafter will lead to afternoon readings closer to 20% on Wednesday. && .SPOTTER INFORMATION STATEMENT... Spotter reports will not be needed through the weekend. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook, Twitter, and at weather.gov/phoenix DISCUSSION...Vasquez AVIATION...Wilson FIRE WEATHER...Kuhlman

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