Weather Outlook
Date & Time: 4/23/2024 @ 8:40 AM MST
Forecaster: Malloy, J.
Synopsis:
A mostly sunny, hot, dry, and breezy high pressure ridging weather pattern continues. The County has been observing widespread 90s and a few 100°F readings each afternoon since this past Sunday. Such heat stays with us today before beginning a decline on Wednesday (low to mid-90s) when the high pressure axis starts shifting east of the area. Overnights are running quite mild, too. The unofficial low at Phoenix Sky Harbor this morning was 70°F, while most other rural/suburban sites landed in the 60s. On top of the warmth, look for breezier southwesterly afternoon/early evening winds (20-30mph) today and Wednesday given westerly flow aloft readily mixing down due to strong rising thermals creating a turbulent boundary layer across the desert landscape.
Thursday is a transition day. High pressure is replaced by low pressure troughing. We’ll be watching for a much cooler air mas traversing the region starting early Thursday morning. Increase humidity and some uptick in cloud cover with virga are expected; however, a rain threat over the lower deserts is questionable at this time. Brief light showers making it to the ground would be possible in the high country of central AZ, though. More confidence lies in ongoing widespread breezy daytime/early evening westerly winds (20-30mph) and a sharp (but welcomed) drop in afternoon temps down to the low 80s in the Valley. Overnight desert temperatures by Friday morning also get a chance to fall back into the upper 50s (low 60s still likely in the Phoenix urbanized corridor). Projections indicate a cool, unsettled weather pattern lingering through the upcoming weekend. More details to come throughout the week!
Weather Tutor:
What is virga? Virga is simply the appearance of rain streaks originating from a cloud base but evaporates before reaching the ground. Virga is common when the mid and/or upper levels of the atmosphere are sufficiently moist for saturation and precipitation generation yet a much drier air mass near the surface evaporates (or “consumes”) any falling liquid or frozen precipitation until the lower atmospheric water vapor demand is satisfied enough to allow precipitation to survive the journey to the landscape below. The “streakiness” appearance in the sky is related to both wind shear and changing terminal velocity of falling precipitation as vaporization occurs. Excessive virga and evaporative cooling may promote windier conditions similar to how thunderstorms create gusty outflow winds when relatively colder air above arrives at the surface and spreads out.
Today’s Climate Context:
Normal High 87˚F (Record Warmest 103˚F in 2012; Record Coolest 64°F in 1942)
Normal Low 63˚F (Record Warmest 74˚F in 2012; Record Coolest 40°F in 1923)
Daily Record Precipitation (0.57” in 1942)
Workday Almanac:
Today’s Sunset – 7:05 PM; Tomorrow’s Sunrise – 5:46 AM
Moon Phase – Full Moon (100%)