Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
796 FXUS65 KTWC 082145 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 245 PM MST Mon Jul 8 2024 .SYNOPSIS...Excessive heat continues through mid-week with high temperatures expected to approach record levels in some locations. The combination of substantially drier air and a stable atmosphere will reduce thunderstorm chances today. Returning moisture and a more favorable weather pattern will result in thunderstorm chances returning Tuesday and increasing through the week. && .DISCUSSION...Excessive heat. Its almost a broken record at this point, but it remains significantly impactful for Southeast Arizona not only today but well into this week. The 08/13Z NBM probabilities for Tucson exceeding 110 degrees this week are 80% today/55% Tuesday/55% Wednesday/55% Thursday and 25% Friday. We are running approximately 1 to 5 degrees warmer than this time 24 hours ago across the CWA, with KTUS already reaching 111 degrees at 231 pm MST. The record high temperatures for KTUS today is 111 degrees last set in at 1994. With regards to thunderstorm activity, today will be a quiet day across the entire forecast area. The SE extent of the upper ridge centered over central California will be just too much warm air for us to overcome this afternoon. Surface dewpoints are awful today, with KSAD mixing down so far to 22 degrees, and KDUG and KTUS down to 43 degrees. Not the most favorable conditions for afternoon convection. No storms today with some cumulus developing near/over the higher terrain. This will begin to change as we move through the week though. A N/S oriented jet streak seen on the eastern periphery of the upper ridge this morning will assist in the re-orientation of this feature from a negative tilt this morning to a more neutral tilt Tuesday. As this occurs, areas east of Tucson will start to see an area of weak diffluence and stretching deformation aloft, which will in turn assist in the overall lift. In addition, CAMS are suggesting an outflow from storms in NM today will import lower level moisture into the eastern locales/upper Gila River Valley overnight. The combination of these two things will bring back thunderstorm activity east of Tucson tomorrow. With the excessive heat in place and pockets of dry air in the middle levels, the threat tomorrow will be from strong thunderstorm outflows. At this stage, I dont believe the extent of any outflows impacting locations as far west as Tucson will occur tomorrow. However, as the upper high shift more to the north and east with time, this allows for the more favorable NE flow from storms to march from the Rim down toward our neck of the woods. Expect thunderstorm coverage to expand west across the rest of the CWA beginning Wednesday and continuing into the weekend. Late this weekend into early next week, the upper High is expected to move over Colorado. This position would open Southeast Arizona up to an easterly flow. There are indications that point to an inverted trough making its way into southern New Mexico Sun day and Monday. If this were to happen, not only would we see an increase in moisture from the east and south, but dynamics will be present for more widespread precipitation Sunday and Monday. There is still some uncertainty in where that upper high eventually moves to, but things are starting to look wet as we move into early next week. Stay tuned. && .AVIATION...SKC across the majority of southeast Arizona with the exception of SCT cumulus above the higher terrain. Areas near KDUG and the New Mexico border SCT-BKN 7-10k ft AGL are possible feet are possible with a slight chance of a thunderstorm through the evening. Skies will become SKC this evening and overnight. SFC Winds west to northwesterly 10 to 15 kts with occasional gusts to 20-25 kts, decreasing after sunset. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Excessive heat will persist this week across the majority of Southeast Arizona. This afternoon should see the lowest minimum relative humidities of the week as moisture is expected to gradually push back into southeastern Arizona in the coming days. Relative humidity values should fall into the single digits in lower elevations today, while west to northwest winds of 12 to 16 mph with gusts up to 25 mph are expected. Tuesday through Thursday minimum relative humidities should remain in the 10 to 16 percent range in lower elevations and 15 to 30 percent in mountain areas. 20-foot winds will generally be 15 mph or less each afternoon with occasional gusts to 20 mph. Daily chances for thunderstorms begin to arrive Tuesday, with the possibility of strong outflow winds under any thunderstorm. && .CLIMATE... Near record to record high temperatures today, Tuesday, and Wednesday. DATE Jul 08 Jul 09 Jul 10 FCST RCD/YR FCST RCD/YR FCST RCD/YR TUCSON INTL AIRPORT 111 111/1994 110 110/1979 109 109/2021 PICACHO PEAK 114 114/2017 114 113/1994 113 111/1995 SAFFORD AG STATION 110 107/2002 106 108/1956 106 110/2003 SIERRA VISTA FD 102 102/2023 100 103/2003 100 102/2003 && .TWC WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 8 PM MST Wednesday for AZZ501>506-509. && $$ Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson