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

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000 FXUS64 KMRX 092316 AFDMRX AREA FORECAST DISCUSSION National Weather Service Morristown TN 716 PM EDT Thu Apr 9 2020 .UPDATE... FOR 00Z AVIATION. && .SHORT TERM...(Tonight and Tomorrow)... Temperatures have risen a few degrees higher this afternoon than what max temperatures were forecast to be earlier in the day. This is due to the cold front moving off to the east slower than anticipated. This has allowed temperatures to climb into the mid and upper 60s across most areas and around 70 across the southern TN Valley. It`s been a very nice day because of the warmer temps, even with the gusty winds. Tonight, temperatures will quickly fall with the drier air in place as dewpoints are in the low to mid 30s. Lows temps also bottom out in the lower to mid 30s across our northern areas while upper 30s to near 40 will be more common down across the southern TN Valley. Winds will stay up through the night with the tight pressure gradient in place so no danger of frost. Clouds increase overnight as another impulse rotates down through the upper trough. We will be on the extreme southern end of this impulse so moisture will be very limited. It does look like enough moisture sweeps down into southwest VA and extreme northeast TN to allow for a few light snow showers to develop after midnight. These light snow showers only last a few hours and dissipate toward sunrise. The highest terrain of SWVA and NETN may pick up a few tenths of an inch of snow, if that much, so no impacts are expected. Clouds clear quickly tomorrow morning as the trough pulls out and high pressure begins to build back in. Highs will be in the lower to upper 50s tomorrow which is around 10 to 15 degrees below normal. RH values will dip down into the mid 20s by tomorrow afternoon across valley locations due to the drier air in place. SR .LONG TERM...(Saturday through Thursday)... The long-term period starts off with freezing temperatures Saturday morning across the Cumberland Plateau, northeast Tennessee, southwest Virginia and southwest North Carolina. A 1020 mb surface high will be overhead with ideal radiational cooling conditions Friday night into Saturday morning. Confidence is fairly high for near to below freezing temperatures for these locations and went ahead and issued a Freeze Watch for early Saturday morning. PW values will be around 0.2-0.4 inches on Saturday. These values are around the 10th percentile for early to mid April. Therefore, the atmosphere will be very dry with sunny skies forecast on Saturday. With this dry airmass and plenty of insolation and no cold air advection, temperatures will warm quickly throughout the day into the low to mid 60s for most locations. Moisture will quickly increase throughout the region Saturday night into Sunday. The surface high will slide to the east out over the Atlantic with Lee cyclogenesis taking place to the west. Southerly flow will develop across the Southeastern U.S. A deep upper level trough will move across the Southern Plains into the Lower Mississippi River Valley on Sunday. A warm front will lift northwards from the Gulf of Mexico into the LA/MS/AL/GA. Rain chances will increase across the forecast area Saturday night into early Sunday from southwest to northeast as the warm front lifts to the north. Most of the instability will be elevated with thunderstorms forecast on Sunday. There is the chance that the warm front could nudge into southern portions of the forecast area before the end of the day Sunday. There could be the chance for a few strong to severe storms late Sunday afternoon/evening for the southern tier of counties or so but confidence still remains low at this time and will not mention the chance for strong to severe storms in the HWO just yet. The entire forecast area will enter the warm sector late Sunday into Sunday night as the system races off to the northeast. Instability will be limited overnight and the upper level system will be lifting out quickly and do not anticipate any severe weather overnight Sunday. Heavy rainfall with the system will lead to the possibility of some localized flash flooding. PW values will increase to near 2 inches with storm total rainfall amounts of 2-3 inches possible. Rain chances will begin to decrease late Sunday night into Monday morning from southwest to northeast. Drier air will advect in behind the departing system on Monday. Broad troughing is forecast across most of the CONUS next week with temperatures continuing below normal for mid-April. Highs will be in the 50s to low 60s with lows in the 30s/40s throughout much of the upcoming work week. Both the GFS/ECMWF have come into better agreement for next week with maybe some small chances of precipitation mid-week as a fast moving system moves in from the northwest but otherwise, expect mainly dry conditions for the upcoming work week. MA && .AVIATION... 00Z TAF DISCUSSION. VFR conditions forecast to prevail through the period. May have a few light showers or snow flurries in the vicinity of TRI late tonight and early Friday morning, but chances are too low to include in the TAF. Main impact through the period will be strong winds at each TAF site from the NW/NNW with gusts in the 20 to 30 kt range on Friday morning. JB && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 42 60 38 68 52 / 0 0 0 0 80 Knoxville McGhee Tyson Airport, TN 38 57 36 67 49 / 0 0 0 0 70 Oak Ridge, TN 38 57 36 66 50 / 0 0 0 0 70 Tri Cities Airport, TN 34 53 31 62 44 / 10 10 0 0 50 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...Freeze Watch from late Friday night through Saturday morning for Cherokee-Clay. TN...Freeze Watch from late Friday night through Saturday morning for Anderson-Bledsoe-Campbell-Claiborne-Grainger-Hamblen- Hancock-Hawkins-Morgan-Northwest Carter-Northwest Greene- Scott-Sequatchie-Sullivan-Union-Washington. VA...Freeze Watch from late Friday night through Saturday morning for Lee-Russell-Scott-Washington-Wise. && $$

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