Windspeed Posted February 19, 2015 Share Posted February 19, 2015 A thread to discuss the Winter Storm threat for Feb. 20th and 21st. A large area will start out with Winter Wx on Friday and transition to all rain on Saturday afternoon. The timing and location of the system is still in question, as are the p-types and durations of those types in certain areas. Some areas may experience significant icing. ANOTHER WEATHER SYSTEM DEVELOPS TO THE WEST FRIDAY...SPREADINGCLOUDS AND SNOW INTO THE SOUTHERN APPALACHIANS AND EASTERNTENNESSEE VALLEY FRIDAY AND EARLY SATURDAY. SNOW ACCUMULATIONS OF 2TO 4 INCHES ARE POSSIBLE BY SATURDAY MORNING. AMOUNTS MAY BECOMEHIGHER PRIOR TO PRECIPITATION CHANGING TO SLEET AND FREEZINGRAIN...BEFORE WIDESPREAD RAIN WORKS NORTHWARD THROUGH EASTTENNESSEE ON SATURDAY. SOME AREAS...ESPECIALLY NORTHEAST TENNESSEEAND SOUTHWEST VIRGINIA VALLEYS...MAY EXPERIENCE A FEW HOURS OFFREEZING RAIN PRIOR TO THE CHANGE OVER TO ALL RAIN. ABUNDANTRAINFALL AND WARM TEMPERATURES SHOULD RELIEVE ANY ICING PROBLEMS.LOCALIZED FLOODING MAY BECOME A PROBLEM DUE TO RAPIDLY MELTING SNOWPACK. Winter Storm WatchURGENT - WINTER WEATHER MESSAGENATIONAL WEATHER SERVICE NASHVILLE TN254 PM CST WED FEB 18 2015 ...WINTER WEATHER ADVISORY FOR THE EAST THROUGH 6PM...DANGEROUSWIND CHILLS TONIGHT INTO THURSDAY AND ANOTHER WINTER STORM FORFRIDAY AND FRIDAY NIGHT... .LIGHT SNOW SHOWERS WILL CONTINUE ACROSS THE REGION THROUGH6PM...BUT COULD LEAD TO MINOR ADDITIONAL ACCUMULATIONS OVER HIGHERELEVATIONS IN EASTERN MIDDLE TENNESSEE. FURTHER...THE COLDEST AIROF THE SEASON WILL USHER INTO THE REGION TONIGHT AND INTO THURSDAY.WINDS TONIGHT COMBINED WITH BITTER COLD TEMPERATURES AT OR BELOWZERO WILL PRODUCE WIND CHILLS DOWN TO -15 TONIGHT INTO MIDDAYTHURSDAY. YET ANOTHER WINTER STORM WILL IMPACT MIDDLE TENNESSEE ONFRIDAY...WITH SNOW...SLEET AND ICE ACCUMULATIONS POSSIBLE INTOFRIDAY NIGHT BEFORE CHANGING OVER TO ALL RAIN SATURDAY. TNZ005>008-023>028-056>063-075-077-093>095-190600-/O.NEW.KOHX.WS.A.0002.150220T1800Z-150221T1800Z//O.CON.KOHX.WC.Y.0003.150219T0000Z-150219T1800Z/STEWART-MONTGOMERY-ROBERTSON-SUMNER-HOUSTON-HUMPHREYS-DICKSON-CHEATHAM-DAVIDSON-WILSON-PERRY-HICKMAN-LEWIS-WILLIAMSON-MAURY-MARSHALL-RUTHERFORD-CANNON-BEDFORD-COFFEE-WAYNE-LAWRENCE-GILES-INCLUDING THE CITIES OF...DOVER...CLARKSVILLE...SPRINGFIELD...GALLATIN...ERIN...WAVERLY...DICKSON...ASHLAND CITY...NASHVILLE...LEBANON...MOUNT JULIET...LOBELVILLE...CENTERVILLE...HOHENWALD...FRANKLIN...BRENTWOOD...COLUMBIA...LEWISBURG...MURFREESBORO...WOODBURY...SHELBYVILLE...TULLAHOMA...MANCHESTER...WAYNESBORO...LAWRENCEBURG...PULASKI254 PM CST WED FEB 18 2015 ...WIND CHILL ADVISORY REMAINS IN EFFECT FROM 6 PM THIS EVENINGTO NOON CST THURSDAY......WINTER STORM WATCH IN EFFECT FROM FRIDAY AFTERNOON THROUGHSATURDAY MORNING... THE NATIONAL WEATHER SERVICE IN NASHVILLE HAS ISSUED A WINTERSTORM WATCH...WHICH IS IN EFFECT FROM FRIDAY AFTERNOON THROUGHSATURDAY MORNING. * WIND CHILL ADVISORY IMPACTS...WIND CHILL VALUES WILL DROP DOWN TO AS LOW AS -15 AT TIMES FROM 6PM TONIGHT THROUGH NOON THURSDAY. * WINTER STORM WATCH TIMING...A WINTER STORM WATCH IS IN EFFECT FROM FRIDAY AT NOON UNTIL SATURDAY AT NOON. * MAIN WINTER STORM IMPACT...A MIX OF ACCUMULATING SNOW...SLEET AND ICE WILL BE POSSIBLE FRIDAY AND FRIDAY NIGHT BEFORE CHANGING OVER TO ALL RAIN MIDDAY SATURDAY. * OTHER IMPACTS...UNTREATED ROADS WILL REMAIN TREACHEROUS THROUGH THE REST OF THE WEEK. IF YOU MUST TRAVEL...USE EXTREME CAUTION. TNZ067>069-071-073-083>086-099>101-190900-/O.EXP.KMRX.WW.Y.0008.000000T0000Z-150219T0000Z//O.CON.KMRX.WS.A.0002.150220T2100Z-150221T2100Z/ROANE-LOUDON-KNOX-NW BLOUNT-NORTH SEVIER-RHEA-MEIGS-MCMINN-NORTHWEST MONROE-HAMILTON-BRADLEY-WEST POLK-INCLUDING THE CITIES OF...KINGSTON...LENOIR CITY...KNOXVILLE...MARYVILLE...SEVIERVILLE...DAYTON...DECATUR...ATHENS...MADISONVILLE...CHATTANOOGA...CLEVELAND...BENTON715 PM EST WED FEB 18 2015...WINTER STORM WATCH REMAINS IN EFFECT FROM FRIDAY AFTERNOONTHROUGH SATURDAY AFTERNOON......WINTER WEATHER ADVISORY HAS EXPIRED...* EVENT...A WINTER STORM SYSTEM MAY APPROACH BY LATE FRIDAY...BRINGING A THREAT OF WINTRY PRECIPITATION INTO SATURDAY.* TIMING...PRECISE TIMING OF THE POTENTIAL WINTER STORM REMAINS UNCERTAIN. PRECIPITATION WITH THIS STORM IS EXPECTED TO BEGIN LATE FRIDAY.* IMPACTS...SNOW ACCUMULATION MAY RESULT IN HAZARDOUS TRAVEL CONDITIONS ON UNTREATED ROADWAYS. GUSTY WINDS MAY RESULT IN ADDITIONAL POWER OUTAGES AND TREE DAMAGE IN AREAS THAT RECEIVED SIGNIFICANT ICE ACCUMULATION ON MONDAY.PRECAUTIONARY/PREPAREDNESS ACTIONS...A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANTSNOW...SLEET...AND/OR ICE ACCUMULATIONS. FUTURE DRIVINGCONDITIONS MAY BECOME HAZARDOUS...SO CONTINUE TO MONITOR THELATEST FORECASTS. Link to comment Share on other sites More sharing options...
jaxjagman Posted February 19, 2015 Share Posted February 19, 2015 Thanks windspeed.Hey guys,can we just use this one thread for forecast and OBS?Having two threads for the same dates can get confusing. Link to comment Share on other sites More sharing options...
Windspeed Posted February 19, 2015 Author Share Posted February 19, 2015 Works for me. I'll add it to the tags. Link to comment Share on other sites More sharing options...
John1122 Posted February 19, 2015 Share Posted February 19, 2015 The NAM appears to have 4-8 hours of snow, followed by 4-8 hours of sleet/zr working it's way across the Valley from SW to NE. .2-.4 snow, followed by .2-.4 sleet/zr. Link to comment Share on other sites More sharing options...
John1122 Posted February 19, 2015 Share Posted February 19, 2015 This is the last of the 3 hour panels where any of us are below freezing. North of 40 and the Plateau are around 30-31 degrees at this time. Link to comment Share on other sites More sharing options...
Stovepipe Posted February 19, 2015 Share Posted February 19, 2015 0z NAM clown: Link to comment Share on other sites More sharing options...
Stovepipe Posted February 19, 2015 Share Posted February 19, 2015 The Hi-Res NAM seems to be more freezing rain and less snow than regular NAM based on meteograms and p-type maps. Link to comment Share on other sites More sharing options...
Chattownsnow Posted February 19, 2015 Share Posted February 19, 2015 0z NAM clown: it's a shame it would be washed away so quickly once the rain starts. I nice glaze of ice should slow it down some to start but not long. looks to have beefed up precip some from previous runs as well. Link to comment Share on other sites More sharing options...
John1122 Posted February 19, 2015 Share Posted February 19, 2015 The Hi-Res NAM seems to be more freezing rain and less snow than regular NAM based on meteograms and p-type maps. I'm thinking it's gonna be closer to 2 inches of snow, maybe 3, 1/2 inch or so of sleet then .10 or so of freezing rain based on model blends. MRX is just saying they've no idea how much of anything will fall. Link to comment Share on other sites More sharing options...
Windspeed Posted February 19, 2015 Author Share Posted February 19, 2015 Link to comment Share on other sites More sharing options...
John1122 Posted February 19, 2015 Share Posted February 19, 2015 Tropical seems to count all frozen as snow, which seems to be common for a lot of clown generation programs. This one is a little closer to reality but probably still not exactly in line with the model output. Link to comment Share on other sites More sharing options...
John1122 Posted February 19, 2015 Share Posted February 19, 2015 MRX kept the Winter Storm Watch as is, but I suspect they ultimately issue and advisory. They filled their grids with 1-3 inches plus some ice. Mentioned it would likely be a high end advisory event, Link to comment Share on other sites More sharing options...
Vol Man Posted February 19, 2015 Share Posted February 19, 2015 MRX is a little confusing on this...not even a WWA for NETN, with expectation of advisory snow and ice...but a WSW for central and southern valley with no more expectation of totals than for northern valley. And on their grid, they show wind chill values for Friday of -1 to -11, with a temp of 24 and only winds at 5 mph? Does that sound right? One more question: anyone else think it seems odd that the record low for tonight is 13? I would have though it would have been quite a bit lower for the record. All the local mets seem to be making a big deal that we will break our record tonight by close to 20 degrees...the 13 just doesn't seem right to me. Link to comment Share on other sites More sharing options...
John1122 Posted February 19, 2015 Share Posted February 19, 2015 MRX is a little confusing on this...not even a WWA for NETN, with expectation of advisory snow and ice...but a WSW for central and southern valley with no more expectation of totals than for northern valley. And on their grid, they show wind chill values for Friday of -1 to -11, with a temp of 24 and only winds at 5 mph? Does that sound right? One more question: anyone else think it seems odd that the record low for tonight is 13? I would have though it would have been quite a bit lower for the record. All the local mets seem to be making a big deal that we will break our record tonight by close to 20 degrees...the 13 just doesn't seem right to me. I am sure it's been colder, but Tri hasn't been keeping records as long as Knoxville, who has a record of 8 for 2/20. As for no advisories, they mentioned that the timeframe is just a bit too far out for them in NE Tennessee. Which is another reason I believe the Winter Storm Watch has a good chance of being turned into an Advisory when it comes time, likely with the afternoon shift you'll see area wide advisories, although they could probably even hold off until Friday morning for NETN, SWVA. Link to comment Share on other sites More sharing options...
weathertree4u Posted February 19, 2015 Share Posted February 19, 2015 I am sure it's been colder, but Tri hasn't been keeping records as long as Knoxville, who has a record of 8 for 2/20. As for no advisories, they mentioned that the timeframe is just a bit too far out for them in NE Tennessee. Which is another reason I believe the Winter Storm Watch has a good chance of being turned into an Advisory when it comes time, likely with the afternoon shift you'll see area wide advisories, although they could probably even hold off until Friday morning for NETN, SWVA. -2 here north of Nashville Link to comment Share on other sites More sharing options...
John1122 Posted February 19, 2015 Share Posted February 19, 2015 My point forecast is now 70 percent snow tomorrow afternoon, 1/2 inch snow. 100 percent tomorrow night of snow, sleet, then zr. 2-4 inches of snow and sleet and .10 of ice. That actually may result in a winter storm warning. Especially with the zr/sleet forecast until 1 Saturday. Link to comment Share on other sites More sharing options...
Stovepipe Posted February 19, 2015 Share Posted February 19, 2015 The NAM is showing 0.43 inches of freezing rain for here, hi-res NAM showing 0.23. Both have less than a half inch of snow. Link to comment Share on other sites More sharing options...
jaxjagman Posted February 19, 2015 Share Posted February 19, 2015 AREA FORECAST DISCUSSIONNATIONAL WEATHER SERVICE NASHVILLE TN349 AM CST THU FEB 19 2015 .DISCUSSION...MOSTLY CLEAR AND VERY COLD CONDITIONS ABOUND THIS MORNING. THEEARLIER SNOWFALL HAS ENDED ACROSS THE PLATEAU AREA. CURRENT TEMPSARE GENERALLY IN THE SINGLE DIGITS. STILL EXPECTING SEVERALLOCATIONS ACROSS THE NORTH TO FLIRT WITH THE ZERO DEGREE MARK FORLOWS. WINDS HAVE DECREASED AND ARE GENERALLY UNDER 10 MPH BUT WILLKEEP THE WIND CHILL ADVISORY GOING UNTIL NOON AS NW WINDS OF 5 TO10 MPH ARE EXPECTED TO CONTINUE. TODAY...BROAD AND IMPRESSIVE THERMAL TROUGH WILL REMAINED ANCHOREDJUST EAST OF THE AREA. THE THERMAL AXIS THIS AFTERNOON WILL BE SETUP ALONG THE ATLANTIC COAST. 850 MB TEMPS ACROSS THE PLATEAU AREAWILL ONLY BE -20C AT 00Z. SO...FOR HIGHS TODAY...WE WILL ONLY SEETHE MERCURY REACH 11F AT CSV...16 FOR CKV AND 19 FOR BNA. TONIGHT...ALL EYES WILL BE ON THE DEVELOPING SYSTEM OVER TX. STILLEXPECTING A SFC LOW TO BEGIN DEVELOPING WITH EASTWARD TROUGHINGDEVELOPMENT. PRECIP SHOULD BEGIN TO SPREAD OUR WAY AND IT LOOKS ASTHOUGH SOME SNOWFALL COULD REACH OUR WESTERN COUNTIES LATE TONIGHT.HOWEVER...POPS WILL BE LOW. AS WE MOVE INTO FRIDAY...SNOW IS EXPECTED TO OVERSPREAD THE MIDSTATE. BY AFTERNOON...THE PRECIP WILL BEGIN TO CHANGE TO SLEET ANDFREEZING RAIN FOR WESTERN AREAS. ON FRIDAY NIGHT...THE TRANSITIONWILL CONTINUE FROM WEST TO EAST. IT LOOKS AS THOUGH THE PRECIP WILLCHANGE TO ALL RAIN ACROSS SOUTHWESTERN AREAS AROUND 03Z...CENTRALAND NW AREAS 06Z-09Z...PLATEAU AREA 12Z TO 15Z SATURDAY MORNING.AFT 15Z...RAIN WILL PERSIST INTO SATURDAY NIGHT. IN FACT...1 TO 2INCH RAINFALL AMOUNTS CANNOT BE RULED OUT. AS FOR THE SNOW AND WINTRY ACCUMULATION...LOOKS AS THOUGH 1 TO 2INCH SNOWFALL AMOUNTS COULD OCCUR ON FRIDAY...PRIOR TO THE SNOWTRANSITIONING TO SLEET AND FREEZING RAIN. SLEET ACCUM COULD BEAROUND 1/4 INCH...AND ICE ACCUM BETWEEN 1/10 INCH AND 1/4 INCH.THE FACT THAT THE OVERALL LIQ EQUIV OF FROZEN/FREEZING PRECIP LOOKSTO BE IN THE .25 TO .35 RANGE...THE WINTER STORM WATCH WILLCONTINUE. FOR THE EXT FCST...THINGS KIND OF QUIET DOWN A BIT. WE COULD SEESOME LIGHT SNOW SUNDAY NIGHT AND MONDAY ON THE BACK SIDE OF THE BIGWEEKEND SYSTEM. THEN...FOR NOW...THE GULF MOISTURE REMAINS WELLSOUTH OF OUR AREA AND TN LOOKS DRY. TEMPS WILL STILL RUN ON THE COLDSIDE FOR THE MIDDLE OF NEXT WEEK BUT IT WILL BE NOTHING LIKE IT ISTODAY. Link to comment Share on other sites More sharing options...
Carvers Gap Posted February 19, 2015 Share Posted February 19, 2015 So, what do you all have for the (none HIRES) 12z NAM? Looks like it takes its time getting the Valley to the freezing mark Fri-Sat. Looks like significant precip before it switches. Link to comment Share on other sites More sharing options...
Stovepipe Posted February 19, 2015 Share Posted February 19, 2015 So, what do you all have for the (none HIRES) 12z NAM? Looks like it takes its time getting the Valley to the freezing mark Fri-Sat. Looks like significant precip before it switches. Yeah looks juicier and colder. I'll post the clown and meteograms once it finishes rolling out. Link to comment Share on other sites More sharing options...
Stovepipe Posted February 19, 2015 Share Posted February 19, 2015 12z NAM clown for Friday/Saturday: Link to comment Share on other sites More sharing options...
valkhorn Posted February 19, 2015 Share Posted February 19, 2015 12z NAM clown for Friday/Saturday: Juicy. I wonder how much of that is freezing rain and sleet in TYS. Also, it would be pretty nice to have a nice thump and have it melt so that the ice can at least go away a bit. Link to comment Share on other sites More sharing options...
jaxjagman Posted February 19, 2015 Share Posted February 19, 2015 gimme a few min ill do some text,looks like the NAM is further E ? Link to comment Share on other sites More sharing options...
Silas Lang Posted February 19, 2015 Share Posted February 19, 2015 Juicy. I wonder how much of that is freezing rain and sleet in TYS. Also, it would be pretty nice to have a nice thump and have it melt so that the ice can at least go away a bit. Yeah, surely some of that is ice pellets and zr, right? I wouldn't complain if that happens but that seems like an awful lot of snow. I am also going to assume ratios would be lower due to the impending warm air. Link to comment Share on other sites More sharing options...
jaxjagman Posted February 19, 2015 Share Posted February 19, 2015 Link to comment Share on other sites More sharing options...
Stovepipe Posted February 19, 2015 Share Posted February 19, 2015 Meteograms for 12z NAM show: TYS: Snow: 0.70 ZR: 0.31 Sleet: 0.39 TRI: Snow: 6.5 ZR: 0.23 Sleet: 0.06 BNA: Snow: 0.70 ZR: 0.18 Sleet: 0.36 Link to comment Share on other sites More sharing options...
Carvers Gap Posted February 19, 2015 Share Posted February 19, 2015 The 12 NAM is significantly south with its precip shield. It is feeling the effects of the cold behind it. 10 m temps are slow to warm. Link to comment Share on other sites More sharing options...
1234snow Posted February 19, 2015 Share Posted February 19, 2015 Wow that is a big increase on amounts from yesterday's runs. I'm cautiously optimistic about this one. Can't wait to see what the RGEM shows. Link to comment Share on other sites More sharing options...
Wulfer Posted February 19, 2015 Share Posted February 19, 2015 Meteograms for 12z NAM show: TYS: Snow: 0.70 ZR: 0.31 Sleet: 0.39 TRI: Snow: 6.5 ZR: 0.23 Sleet: 0.06 BNA: Snow: 0.70 ZR: 0.18 Sleet: 0.36 Stovepipe can you provide KCHA numbers? Link to comment Share on other sites More sharing options...
Carvers Gap Posted February 19, 2015 Share Posted February 19, 2015 I am not sure that I buy the 12 NAM yet. That was a big shift in our favor this time. The totals are dependent on two things: 1. Precip moves in before the cold moves out(that I think is correct...but how much?) 2. Precip shield is south(after the last storm, I am a little iffy on this one, but synoptics may favor this) Temps tomorrow will be around zero tomorrow morning. Will be tough for any system to erode the cold quickly. Going to be very dependent on how quick the precip moves in. If it is slow, this could be next to a non-event. If it is quick, like the NAM...game on. So, let's see what model support the NAM has and what would counter it. Anyone have any maps that would support it from short range models? Link to comment Share on other sites More sharing options...
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