Area Forecast Discussion
Issued by NWS Flagstaff, AZ
Issued by NWS Flagstaff, AZ
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290 FXUS65 KFGZ 131720 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 1020 AM MST Thu Jun 13 2024 .SYNOPSIS...Expect another round of abnormally warm temperatures today, even in the face of increasing cloud cover and some isolated, light rain showers. From this evening through Friday, a passing low pressure system will bring more scattered shower activity, and a slight chance for thunderstorms. Dry, warm, and breezy conditions return by the weekend, with a slight cooling trend early next week. && .UPDATE...Current forecasts through Friday are on track with no morning updates planned. Increasing southerly flow aloft ahead of the low off the northern Baja continues to pull moisture northward, mainly in the mid levels. Radar is showing some shower development (likely virga or sprinkles) in southwest Arizona and this will move northward into our region this afternoon. Still thinking this afternoon`s activity will be this virga/sprinkle activity for the most part as CAPE is very low. As the low shifts closer to our area later tonight/Friday, instability associated with cooling mid-level temperatures will bring a bit better chance for a few thunderstorms. && .PREV DISCUSSION /351 AM MST/...Current satellite and upper-air analysis shows a 500 mb low centered off the west coast of northern Baja and a 500 mb ridge over northern Mexico. A southerly flow between these features has transported moisture into southern Arizona. For example, the dew point in Yuma, AZ is currently sitting around 50 degrees, which is about 5-10 degrees higher than this time yesterday morning. Moist air will continue to spread northward across the state today, bringing with it increasing cloud cover and chances (10-30%) for light rain showers. While this moisture will keep high temperatures a couple of degrees cooler than yesterday, abnormally warm conditions will persist and an Excessive Heat Warning remains in effect below 4000 feet within the Grand Canyon and lower deserts of Yavapai County through 8 pm MST. Otherwise, most locations will see a round of south-southwest winds, with gusts in the 20-30 mph range during the afternoon hours. From this evening through Friday, the aforementioned low will move across the state resulting in higher chances (20-50%) for showers, and a slight chance (10-15%) of thunderstorms and dry lightning. While rainfall amounts are expected to be meager, a few pockets of rainfall in the 0.2-0.4 inch range may occur, especially across northeast Arizona. As you would expect with the cloudy and unsettled weather forecast for Friday, daytime temperatures will dip a few degrees resulting in an end to the excessive heat. On Saturday, dry weather returns to Arizona as the low pressure system slides across the central United States. At the same time, the general model consensus predicts a long wave trough over the western United States will deepen keeping Arizona under the influence of a dry southwest flow aloft through at least mid- week. High temperatures may quickly rebound again on Saturday, with temperatures approaching excessive heat levels once again. This increase in temperature may be short-lived though, with a slow but steady cooling trend likely after that. Forecast uncertainty is high beyond Sunday. Model disagreements hinge on the strength of the developing longwave trough, as well as the timing of shortwaves traversing the general flow. Overall, the main hazard in the extended forecast is for critical fire weather. The majority of longer range models highlight Sunday and Monday as the period with the best combination of low relative humidity and strong surface winds. && .AVIATION...Thursday 13/18Z through Friday 14/18Z...Mostly VFR conditions will prevail under mid to high level cloud cover. Brief MVFR conditions are possible throughout the TAF period in isolated -SHRA, but mostly showers are excepted to be light. Look for SW winds 15-25 kts, gusting near 30 kts after 18Z. Light and variable winds should return after 06Z. Gusty/erratic winds will be possible near storm development, with greater chances for -TSRA after midnight. OUTLOOK...Friday 14/18Z through Sunday 16/18Z...-SHRA/-TSRA will continue along and NE of a KSJN-KPGA line between 18Z-00Z, with drier conditions elsewhere. VFR conditions will prevail outside of areas experience showers/thunderstorms. Winds look to be generally out of the SW each afternoon, becoming gusty on Sunday. && .FIRE WEATHER...Today and Friday...Hot temperatures will continue today before slightly cooling off tomorrow. Chances for rain/thunderstorms this afternoon across Yavapai & Coconino Counties, becoming more focused across E Arizona on Friday. Dry lightning and gusty/erratic winds possible near storms. Southwest winds 15-25 mph today becoming more westerly 10-20 mph Friday. Saturday through Monday...Above normal temperature will continue through Sunday, with cooler conditions returning Monday. Mainly dry conditions with gusty, southwest winds and afternoon RH values 5-15% daily. Near critical fire weather conditions likely over the weekend and continuing into next week. && .FGZ WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 8 PM MST /9 PM MDT/ this evening for AZZ005-006-037. && $$ PUBLIC...JJ/RR AVIATION...Konieczny FIRE WEATHER...RR For Northern Arizona weather information visit weather.gov/flagstaff