Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
100 FXUS65 KTWC 151555 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 855 AM MST Mon Jul 15 2024 .SYNOPSIS...Temperatures slightly above normal for most of this week with typical mid July moisture levels across the region. This will result in daily chances of showers and thunderstorms. Main threats will continue to be strong gusty winds and heavy rain including flash flooding potential. && .UPDATE...Visible satellite imagery shows scattered debris clouds over portions of southeast Arizona this morning, which continues to slowly dissipate. The latest observations across the forecast area indicate surface dewpoints from the upper 50s to the upper 60s. GOES- 16 ECONUS Total Precipitable Water (PW) imagery values range from near 0.75 inches in the White Mountains, to around 1 inch in Cochise County to over 1.50 inches in central/western Pima County. The KTWC 240715/12Z upper air sounding indicated 1.20 inches of PW, DCAPE of around 1500J/kg and generally an unstable profile once convective inhibition is reached. Overall, PW was down 0.34 inches versus 24 hours ago and the airmass is not quite as unstable as yesterday. However, still plenty of moisture and CAPE to work with today, with the University of Arizona Regional WRF Model Forecast showing max CAPE values between 1500-2000 J/kg over portions of southern Graham, Cochise, Santa Cruz and eastern Pima counties. The latest CAM solutions continue to point to an earlier start today between 18Z- 19Z over Cochise, Graham and Santa Cruz counties. Convection will then shift westward through the afternoon hours with the easterly flow at the mid levels. The U of A WRF and SPC HREF models both show areas south/southeast of Tucson will be rather active today, with both suggesting a complex developing over northern Sonora. In regards to the Tucson metro, both of these models show minimal convection occuring across the metro today, which makes sense given how hard the area was hit yesterday afternoon/evening. However, both models do bring convection into far eastern/southeastern Pima County, so if any organization to the storms takes place or propagation along outflow boundaries occur, then convection may still occur over Tucson. The main concerns today continue to be strong, gusty outflow winds and areas of heavy rainfall leading to localized flash flooding. && .PREV DISCUSSION... /issued 202 AM MST Mon July 15 2024/ Latest IR/WV satellite imagery shows some debris cloudiness early this morning following the active convection yesterday (most notably in the Tucson Metro). The mid/upper level pattern continues to feature high pressure near the Four Corners region which is keeping the favorable easterly mid level flow in place. Meanwhile, abundant lower level moisture remains from Tucson westward with PWAT values around 1.25" to 1.50" with lesser values closer to around 1" east of Tucson. It`s an interesting forecast today as we`ve got some competing factors to deal with in regards to convection. For those areas that got hit hard yesterday, the lower levels are worked over so it will take time to recover and that will tend to locally reduce convective activity. However, given the mid level steering flow of around 20 kts and clearing skies, many locales are setting up for another round of showers and thunderstorms. The CAMs today are reasonable in developing an area showers and thunderstorms south and east of Tucson this afternoon, especially across Cochise and Santa Cruz County. Lower confidence on how much activity will occur from Tucson westward. Regardless, main concerns today will be gusty winds and areas of heavy rain. A fairly typical mid July monsoon pattern is shaping up for the remainder of this week in our forecast area. The mid/upper level high which will initially be near the Four Corners will meander a bit to the south and west later in the week. However, our area will be far enough south much of the time to keep us in an active regime. Biggest uncertainties are the day to day variability in the moisture levels and potential for mid level warming when the high gets a bit closer. Overall though the theme for mainly afternoon and evening showers and thunderstorms through the rest of the week continues. In this regime both strong gusty winds and locally heavy rain are the main threats. Temperatures will be near to slightly above normal. && .AVIATION...Valid through 16/12Z. SCT clouds AOA 15k ft AGL, becoming SCT-BKN clouds at 8-12k ft AGL aft 15/18Z and continuing thru 16/04Z before diminishing. SCT TSRA/SHRA developing aft 15/19Z, first in Cochise and Santa Cruz Counties, potentially impacting KDUG and KOLS. SCT TSRA/SHRA will tend to push west but confidence in impacting KTUS is lower today. MVFR conditions in TSRA, with mountain obscurations, vsby reductions and wind gusts to 40+ knots. Outside of TSRA, SFC wind at most locations 12 knots or less favoring a SWLY thru NWLY direction during the afternoon/early evening hours and variable in direction at other times. The exception will be in the upper Gila River valley near KSAD where WLY/NWLY SFC wind will be 12-20 kts with gusts to 28 kts 15/18Z thru 16/03Z. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Deeper moisture has moved back into southeast Arizona and typical mid July moisture levels are expected through the week. This will result in the daily cycle of mainly afternoon and evening showers and thunderstorms, with the potential for more widespread rainfall. The main threats will be strong, gusty and erratic outflow winds and heavy rainfall leading to localized flash flooding. Minimum relative humidity values will be 20-30 percent in most lower elevation locations and 30-45 percent in mountain areas. Away from thunderstorms, 20-foot winds will generally be 15 mph or less, with afternoon/early evening gusts to 20-25 mph and light winds overnight. The exception will be in the upper Gila River valley around Safford, where afternoon/early evening winds will be west-northwest at 15-20 mph and gusts to 25-30 mph through Tuesday. Wind direction will primarily be southwest through northwest through most of the week. && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ Zell Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson