SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1238 AM CDT Tue Sep 12 2023 Valid 121200Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF ARIZONA AND THE FLORIDA PENINSULA... ...SUMMARY... Isolated severe thunderstorm wind gusts and a couple instances of hail are possible across parts of southern Arizona Tuesday afternoon into early evening. Gusty winds may also be noted with convection over the Florida Peninsula. ...AZ... Upper anticyclone has settled south of the international border over northwest Mexico. As a result, stronger westerlies are now observed at low latitudes and several embedded short-wave troughs are currently noted within this flow from off the coast of southern CA into the southern Rockies/southern Plains. The air mass over the southern Plains will stabilize significantly over the next 24hr as surface pressures build over the middle of the country and a cold front advances into southwest TX. However, seasonally steep lapse rates are forecast to continue across portions of the southwestern US where PW values are expected to remain at/above 1.5" across the lower desert regions of AZ. Latest model guidance suggests isolated severe thunderstorms may evolve later this afternoon ahead of a weak disturbance. Forecast soundings exhibit modest surface-6km shear (20-25kt), which could support a few organized multicell updrafts. Convective temperatures should easily be breached by late afternoon and gusty winds, and perhaps some hail, may be noted with the more robust updrafts. This activity should propagate east toward higher terrain during the evening. ...FL Peninsula... Large-scale pattern will not change appreciably across the FL Peninsula during the day1 period. Weak mid-level trough that is currently located over the central Gulf Basin will only slowly progress east Tuesday, remaining well offshore through the period. Even so, 500mb temperatures may actually cool slightly today compared to Monday, and this should result in considerable buoyancy as temperatures warm through the 80s to near 90F across the interior Peninsula. Steep low-level lapse rates would seemingly support gusty downdrafts with the strongest diurnally driven convection. Some sub-severe hail may also be noted with this activity. ..Darrow/Squitieri.. 09/12/2023
