Area Forecast Discussion
Issued by NWS Flagstaff, AZ
Issued by NWS Flagstaff, AZ
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584 FXUS65 KFGZ 132345 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 445 PM MST Thu Jun 13 2024 .SYNOPSIS...From this afternoon through Friday, a passing low pressure system will bring 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. && .DISCUSSION...A well defined upper low was located just off the coast of San Diego this afternoon, moving slowly toward the northeast. Southerly flow ahead of this low has induced a surge of mid level moisture into Arizona, and scattered shower development is ongoing in southwest Arizona stretching up into portions of Yavapai and Coconino counties. Most of this activity through the afternoon should be in the form of virga and light showers, though a couple lightning strikes have been observed north of Yuma already. With the hot/dry boundary layer still in place, a few of these showers could produce strong outflow winds of 40+ mph. As the upper low moves closer to our area later tonight, cooling temperatures aloft will steepen lapse rates and allow for a few thunderstorms to develop and spread northward. Precipitation amounts are forecast to be fairly minimal overnight, less than 0.10" for most areas that see precipitation at all. By Friday - the upper low shifts into northeast AZ and then NM/CO by late afternoon. The chance for showers and thunderstorms continues in the morning as far south/west as Flagstaff and then will be focused in northeast Arizona by afternoon. With daytime heating, scattered thunderstorms are forecast northeast of a Kayenta to St Johns line. Temperatures Friday afternoon will be several degrees cooler and well below Excessive Heat Warning criteria. Shower and storm chances end by sunset Friday. Saturday - Heat builds back in briefly as the low departs, and the next larger western US trough begins to take shape. Ridging builds between these two features and allows temperatures to rise to well above normal levels once again. As of now, highs look to remain a bit below warning criteria but this will need to be monitored. Sunday through Tuesday - the major feature this period will be a deep upper low (for mid June) centered over the NW US. Northern Arizona will be on the dry and windy southern end of this feature, with heights falling below normal and allowing for a cooling trend. Southwest winds will increase, with sustained speeds of 15-25 mph and gusts greater than 30-35 mph likely each day. The combination of gusty winds and low humidity brings the threat of critical fire weather with the best chances Sun/Mon but Tuesday will need to be watched too. && .AVIATION...Friday 14/00Z through Saturday 15/00Z...Mainly VFR expected. Brief MVFR conditions are possible in ISO SHRA. SW winds 15-25 kts, gusting near 30-35 kts, becoming light and variable after 06Z. Gusty/erratic winds will be possible near storm development, with greater chances for TSRA after 06Z. OUTLOOK...Saturday 15/00Z through Monday 17/00Z...Mainly VFR conditions with SW winds. Winds become gusty on Sunday. && .FIRE WEATHER...Isolated to scattered showers and thunderstorms will continue tonight, becoming more focused over E. AZ. on Friday. Gusty and erratic winds possible near storm development along with dry lightning. Look for 5-15 mph west-southwest winds on Friday and breezy southwest winds on Saturday. Minimum RH values will drop from 10-25% Friday afternoon to 5-15% on Saturday afternoon. Dry and warm conditions forecast for Saturday. Sunday through Tuesday...A slight cooling trend will occur Sunday through the beginning of the week. Look for gusty southwest winds Sunday, increasing and peaking on Monday. Minimum RH values will linger in the single digits to mid-teens each afternoon. As a result, near-critical fire weather concerns likely for the end of the weekend through the beginning of next week. && .FGZ WATCHES/WARNINGS/ADVISORIES...None. && $$ PUBLIC...JJ AVIATION...Meola FIRE WEATHER...Konieczny For Northern Arizona weather information visit weather.gov/flagstaff