Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
594 FXUS65 KTWC 202036 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 136 PM MST Thu Jun 20 2024 .SYNOPSIS...Hot temperatures this afternoon with an Excessive Heat Warning in effect for portions of southeast Arizona. Increased moisture will result in the potential for thunderstorms each day into next week week. Storms this afternoon into evening could produce strong winds and blowing dust mainly from Nogales to Tucson and into Pinal County. Windy conditions are also expected into Friday. The added moisture will also result in temperatures dropping back down close to seasonable levels through the weekend. && .DISCUSSION...Plenty of active weather to talk about today as a more monsoonal pattern/moisture regime is developing. East to southeast winds are ongoing, mainly from points Tucson eastward with a southerly to southwesterly flow elsewhere. Given the strong surface pressure gradient, we`ve seen wind gusts between 40 and 50 mph for portions of Graham and Cochise County where a Wind Advisory remains in effect until 5 AM Friday. Moisture levels have increased considerably with PWAT values of 1 to 1.25 inches from Tucson eastward, but still between 0.5 inch to 1 inch west of Tucson where the moisture hasn`t made it quiet yet. For this afternoon, we`re particularly focused on the potential for a north-south line of showers and thunderstorms developing across Eastern Pima/Eastern Santa Cruz/Eastern Pinal/Western Graham/Western Cochise Counties. This north-south line of showers and thunderstorms is forming along the western edge of the moisture push (pseudo dry line) with the mid to upper level flow generally pushing the storms that do develop towards the east to northeast. MLCAPE values this afternoon per the RAP are around 500-1000 J/KG in this favored zone with DCAPE values nearly 2000 J/KG. Given this profile, the main concern with any thunderstorms will be strong/gusty outflow winds producing areas of blowing dust. With that said, a Blowing Dust Advisory remains in place between 3 PM and 8 PM this evening. Not a lot of rain with these storms with dry lightning potential in spots as well. Convective activity will diminish after sunset this evening, and then the focus overnight into Friday morning will continue to be the larger scale east to southeast winds. The normally more susceptible spots for east to southeast winds (including the south and east portions of the Tucson Metro) will especially see the winds kick up tonight into Friday morning. A few locales will see sustained winds approaching advisory levels (30 mph). We didn`t expand any wind headlines on this forecast cycle but this is something we`ll continue to monitor this evening and overnight. HREF probabilities for wind gusts over 45 mph are over 50 percent in these localized most favored spots so the winds will certainly be noticeable overnight into Friday morning for many folks. For Friday, wind speeds will gradually diminish as the day progresses with the main focus turning to the deeper moisture and convective potential. With the increased moisture, temperatures will drop about 3 to 6 degrees for most locales compared to today. PWAT values Friday will increase to around 1 to 1.5 inches and these values range from 150% to 225% of normal so it`s certainly anomalous to have this much moisture early in the monsoon. HREF/CAMS are showing isolated to scattered showers and thunderstorms across most of southeast Arizona Friday afternoon into evening. Main concerns will continue to be gusty winds with brief localized downpours with the strongest storms. For this weekend, additional moisture makes its way into the region with PWAT values increasing to between 1.25 inches near the NM border to nearly 2 inches for the western deserts. These values are 2 to 3 standard deviations above normal for this time of year. With that said, the mid/upper high will be just to our north and east with warm temperatures aloft that will partially mitigate convection. However, given the deep moisture, we`ll certainly see scattered mainly afternoon and evening showers and thunderstorms this weekend. The ensembles are showing a slight meander early to mid next week of the mid/upper level high to the south and west as it strengthens slightly. This type of regime would result in thunderstorm chances shifting to locales generally from Tucson south and eastward. With the high increasing in strength, temperatures bump back up during this timeframe to about 3 to 5 degrees above normal. && .AVIATION...Valid through 22/00Z. SCT-BKN clouds 10-14k ft AGL KTUS/KOLS eastward. Convergence along a surface boundary will likely lead to isolated to scattered -SHRA/- TSRA starting around 21/21Z through about 22/03Z. Main terminals affected will be KTUS and KOLS. Storms will be capable of winds 35- 45 kts with a 10-30 percent chance for winds in excess of 50 kts. Outside of storms SFC winds become SELY at 15-25 kts with gusts to 30-40 kts across much of the forecast area. The strongest winds are expected at KDUG and KSAD terminals. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Temperatures are expected to peak today from Tucson westward, then more seasonable temperatures thereafter. Surface winds currently east to southeast from Tucson eastward and west to southwest areas west of Tucson. The strongest winds will be in the Upper Gila River Valley near Safford as well as near Douglas along the International and NM borders. The increased moisture with min RH values in these locales currently 20-30 percent. So while the winds are at critical levels, RH values will remain just above critical levels but certainly still elevated fire weather conditions due to the strong winds and dry fuels Thursday. Breezy to windy conditions continue Friday, though increased moisture will have overspread more of the forecast area. A mixture of dry/wet isolated to scattered storms are expected this afternoon from Tucson eastward and then to include the remainder of southeast Arizona Friday. As moisture remains this weekend, isolated to scattered thunderstorms will continue each day through the weekend into early next week with a low to mid grade monsoon pattern in place. && && .TWC WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning through 8 PM MST this evening for AZZ501>506. Blowing Dust Advisory from 3 PM this afternoon to 8 PM MST this evening for AZZ502-504>506. Wind Advisory through 5 AM MST Friday for AZZ508-509. && $$ Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson