SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1254 AM CDT Mon Aug 16 2021 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE FLORIDA PANHANDLE...FAR SOUTHEASTERN ALABAMA...AND FAR SOUTHWESTERN GEORGIA... ...SUMMARY... The threat for a few tornadoes should increase across the Florida Panhandle into southeast Alabama and southwest Georgia today. Other storms may produce isolated severe wind gusts and some hail from parts of the central and southern High Plains into the Southwest. ...Southeast... Tropical Storm Fred is forecast by the NHC to move generally northward toward the northern FL Gulf Coast through the day, eventually making landfall somewhere along the western FL Panhandle. The low/mid-level wind field associated with Fred is expected to slowly continue strengthening today through landfall. Short-term guidance is in reasonably good agreement that east-southeasterly winds at 850 mb will strengthen to 35-45 kt in the eastern half of Fred's circulation. A related increase in low-level shear is expected across much of the FL Panhandle into southeastern AL and southwestern GA as Fred moves northward through the period. Even modest heating on the periphery of the tropical storm would be enough to support surface-based storms given the presence of low to mid 70s dewpoints. Weak boundary-layer instability coupled with the increasing low-level shear should prove favorable for low-topped supercells in outer rain bands, with an associated threat for a few tornadoes and isolated strong/gusty convective winds. ...Southwest... Mid-level winds will become more northerly today over the Southwest as an upper ridge becomes centered over CA by this evening. Multiple mid-level vorticity maxima, some convectively enhanced, will move southward across AZ/NM through the day. A seasonably moist low-level airmass is in place across much of the lower elevations across this region, and diurnal heating should boost MLCAPE generally into the 1500-2500 J/kg range. Scattered storms are forecast to initiate over the higher terrain by early afternoon, and subsequently develop south and southwest toward the lower elevations. Even though the mid-level flow should remain fairly modest (15-20 kt), some upscale growth into one or more clusters appears possible by the early evening. Severe/damaging winds should be the primary threat given a very well-mixed boundary layer, but some hail may also occur with initial development over the higher terrain. With the ongoing convection across parts of northern/central AZ, confidence remains too low that sufficient airmass recovery will occur later today at lower elevations to include greater severe wind probabilities. ...Central/Southern High Plains... Isolated storms may be ongoing later this morning across parts of the central and southern High Plains. A moist low-level airmass characterized by mid to upper 60s surface dewpoints will likely persist across these regions along/south of a lee trough. Diurnal heating of this moist airmass will support the development of moderate instability by this afternoon. Modest south-southeasterly low-level winds veering to northerly at mid/upper levels will foster weak deep-layer shear, with the potential for multiple clusters to move southward through the evening. Isolated severe wind gusts and perhaps some hail appear possible with the stronger storms. ..Gleason/Dean.. 08/16/2021 Read more LIVE: spc.noaa.gov
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