Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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000 FXUS64 KMRX 251853 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 253 PM EDT Fri May 25 2018 .SHORT TERM (Tonight and Saturday)... Troughing over the western U.S. with sloppy ridging east of the Rockies...sloppy thanks to weak troughing over the MS Valley that is stuck within the ridge, and which may tend to help draw Alberto toward the northern Gulf Coast. Thus, moisture return is well-underway, seen by scattered diurnal convection presently over the higher terrain. As moisture increase from the Gulf continues, thanks to encroaching influences of Alberto, probabilities of rainfall will increase to likely category Saturday and into the new week. .Long Term (Saturday Night through Thursday Night)... The extended fcst period kicks off on Saturday night amidst an increasingly complex upper pattern which features a broad ridge over the western Atl, northern stream troughing across the OH valley and central Appalachians, and sharp ridging over the plains. Meanwhile at the surface, weak ridging will be in place across much of the southeast CONUS, all while TC Alberto moves northward through the Gulf of Mexico. At fcst initialization, the airmass over east TN and southwest VA/NC will be increasingly moist as persistent llv sly flow funnels moisture northward. Ample daytime heating earlier on Saturday (and again on Sunday) will favor scattered/numerous showers and thunderstorms each day/evening. By Sunday evening, the airmass becomes increasingly influenced by Alberto which should be nearing the gulf coast, and thus advecting more of a tropical like airmass across the southeast. Moving into Monday, current model progs suggest Alberto sliding inland to the west thanks to the western Atl ridge, before shifting east toward midweek as said ridge weakens and another northern stream trough picks up the cyclone. All said, as usual with these tropical systems, uncertainty is high at this range. Therefore given the fact that profiles will be increasingly moist amidst ample heating each day, think relatively high pops are reasonable. The fcst will highlight mostly chance pops on Monday, ramping up to widespread likely levels by Wednesday. At that point uncertainty becomes so high with the ECMWF pushing Alberto through the OH valley, while the GFS slides the storm just east of the spine of the Appalachians. Thus, the remainder of the periods will feature only mid level chances pops, although this is likely to change. Temperatures through the period will remain above normal levels. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 69 85 68 83 / 40 60 60 60 Knoxville McGhee Tyson Airport, TN 67 84 67 84 / 40 60 60 60 Oak Ridge, TN 68 85 68 85 / 40 60 60 60 Tri Cities Airport, TN 64 82 64 81 / 30 60 60 60 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ GC/CDG

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