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

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000 FXUS64 KMRX 180531 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 131 AM EDT Mon Mar 18 2024 ...New AVIATION... .UPDATE... Issued at 1102 PM EDT Sun Mar 17 2024 Temperatures have been slower to fall than forecast. Adjusted hourly temperatures over the next few hours based on local observations. Otherwise, the forecast seems to be in good shape. Northwesterly winds will continue overnight advecting a cooler airmass. && .SHORT TERM... (This evening through Monday) Issued at 241 PM EDT Sun Mar 17 2024 Key Messages: 1. Cold weather arrives tonight, Monday to be 10 to 15 degrees below normal. Discussion: With the stronger cold air advection lagging behind, the front has been slow to cross the area today, which hasn`t had too much impact on the forecast since there`s no moisture to greet the front. Once the cold airmass moves in tonight, temperatures will begin their trek downwards. Some locations will hit freezing tonight, but frost formation might be a little limited, with dewpoint depressions of around ten degrees valley wide indicating available surface moisture is low. Tomorrow temperatures will struggle to rebound under the cold airmass, 850 mb temperatures during the day will be -5C to -7C over East Tennessee, and Nashville sounding climatology suggests 10th percentile cold for this time of year. Northwest flow looks to strengthen Monday afternoon, bringing breezier winds to Tennessee and southwest Virginia, as the upper trough responsible swings fully into the region. Also notable is the precipitable water tomorrow will be below the 10th percentile for this time of year, close to the daily record minimum, with GFS and Euro showing values of 0.20" across all of East Tennessee and southwest Virginia. In response, afternoon relative humidities will dip to the low 30s area wide. Some of the high resolution CAM guidance has suggested flurries/brief drizzle out of the clouds tomorrow afternoon. Not confident enough moisture will be present to see anything in even our Virginia counties or the east TN mountains, so left PoPs as is. && .LONG TERM... (Monday night through next Sunday) Issued at 241 PM EDT Sun Mar 17 2024 Key Messages: 1. Cold night is in store for Monday night with area-wide hard freeze Tuesday morning. Very cold wind chills in the higher elevations with values in the single digits to near zero. 2. Very dry conditions Tuesday through Thursday with low afternoon relative humidity in the 20s and lower 30s. 3. Rain chances return Friday with only light precipitation totals expected. Discussion: For Monday night/Tuesday morning, cold air builds into the Tennessee valley and southern Appalachians with a hard freeze across much of the area. Frost development will be limited due to continued breeze and relatively low relative humidity. For Tuesday through Thursday, a gradual moderation of temperatures and dry conditions are expected with upper flow remaining northwesterly and surface ridging. Main concern will be the low afternoon relative humidity with values dropping into the 20s to lower 30s. For Friday and Friday night, deterministic and ensembles shows a short-wave moving across the Gulf Coast states. Moisture and deformation zone on the northern/northwest side of the associated cyclo-genesis will produce an area of light rain. NBM probabilities of measurable rainfall is only around 50 percent with probabilities of one-quarter inch only around 20 percent. For Saturday, drier conditions return as the system moves off the southeast coast. && .AVIATION...
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(06Z TAFS) Issued at 130 AM EDT Mon Mar 18 2024 VFR flight conditions expected next 24 hours. Winds are becoming gusty behind the cold front early this morning. Some occasional gusts up to 20 knots at are possible at TYS and TRI through the next few hours. Winds should decrease before sunrise and then increase again late this morning and be from the northwest today at 10 to 15 knots with gusts to 25 knots at all three sites, possibly higher at times during the afternoon hours. A decrease in winds will occur at about 00Z Monday evening with sunset as the pressure gradient behind cold front weakens.
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&& .PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN 51 28 58 38 / 0 0 0 0 Knoxville McGhee Tyson Airport, TN 48 27 54 37 / 0 0 0 0 Oak Ridge, TN 49 26 56 35 / 0 0 0 0 Tri Cities Airport, TN 46 25 50 33 / 10 0 0 0
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...Wellington LONG TERM....DH AVIATION...TD

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