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Freeze to Thaw, Winter Wx, Feb. 20th-21st, 2015


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My forecast is for less than an inch of snow and sleet and .1 ice tonight.  That's a relative non-event, the trees would appreciate it.

The zone forecast for Knox is pretty robust.

 

 

 

  • A chance of snow...light freezing rain and light sleet likely in the evening...then light freezing rain and light sleet after midnight. Snow and sleet accumulation 1 to 2 inches. Ice accumulation of up to one quarter of an inch. Lows in the mid to upper 20s. Temperature steady or slowly rising after midnight. South winds 5 to 15 mph. Chance of precipitation 90 percent.
  •  
    Saturday Breezy. Not as cool. Light freezing rain in the morning. Rain in the afternoon. Ice accumulation of up to one quarter of an inch. Highs in the mid to upper 40s. South winds 10 to 20 mph with gusts to 35 mph in the afternoon. Chance of precipitation 80 percent.
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DAY 1 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   0636 AM CST FRI FEB 20 2015

   VALID 201300Z - 211200Z

   ...NO SVR TSTM AREAS FORECAST...

   ...SUMMARY...
   ISOLATED THUNDERSTORMS MAY OCCUR DURING THE AFTERNOON AND EVENING
   ACROSS PARTS OF COLORADO.  THUNDERSTORMS WILL ALSO DEVELOP FROM
   EASTERN OKLAHOMA INTO WESTERN KENTUCKY AND TENNESSEE TONIGHT.

   ...SYNOPSIS...
   A SHORTWAVE TROUGH OVER THE NRN GREAT BASIN WILL TRANSLATE ESEWD TO
   THE CO FRONT RANGE BY THIS EVENING...AND THEN CONTINUE EWD OVER
   KS/MO TONIGHT...WHILE LARGE DOWNSTREAM HEIGHT RISES OCCUR OVER THE
   MID ATLANTIC AND NEW ENGLAND.  FORCING FOR ASCENT IN THE LEFT EXIT
   REGION OF THE MID-UPPER JET...IN COMBINATION WITH CONDITIONALLY
   UNSTABLE LAPSE RATES...WILL SUPPORT A RISK FOR ISOLATED
   THUNDERSTORMS THIS AFTERNOON/EVENING ACROSS PARTS OF CO.
   MEANWHILE...LEE CYCLOGENESIS WILL OCCUR TODAY INVOF THE TX/NM/OK
   BORDER IN ADVANCE OF THE MIDLEVEL TROUGH...AND HELP STRENGTHEN SLY
   FLOW ACROSS TX.  A MODIFYING AIR MASS IS RETURNING NWD FROM THE WRN
   GULF BASIN...WHERE BOUNDARY LAYER DEWPOINTS WILL GRADUALLY INCREASE
   INTO THE MID 60S AS TRAJECTORIES BECOME MORE SLY WITH TIME.  THE N
   EDGE OF THE RETURNING MOISTURE /56-60 F DEWPOINTS/ WILL SPREAD AS
   FAR NE AS THE ARKLATEX BY TONIGHT.

   BUOYANCY WILL REMAIN MINIMAL WITHIN THE DEVELOPING WARM SECTOR
   ACROSS TX TODAY AS A RESULT OF THE MODEST MOISTURE RETURN COMPARED
   TO MIDLEVEL TEMPERATURES/LAPSE RATES.  FARTHER NE AND MAINLY
   TONIGHT...A STRENGTHENING SWLY LLJ WILL PROMOTE STRONG WAA AND
   SATURATION...SUCH THAT WEAK CAPE ROOTED IN THE 850-700 MB LAYER WILL
   BE POSSIBLE.  ELEVATED CONVECTION WILL SLOWLY INCREASE IN COVERAGE
   TONIGHT AS LOW-LEVEL MOISTURE SPREADS NEWD ALONG THE 70-80 KT
   LLJ...WITH THUNDER FREEZING RAIN/SLEET LIKELY WITH THE INITIAL
   CONVECTION DEVELOPING ABOVE A SUB-FREEZING BOUNDARY LAYER FROM AR TO
   THE LOWER OH AND TN VALLEY REGION.

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Is it just me, or is this looking further south than models have been suggesting?

Yes, at least at this point. The HI-Res maps that 1234 posted up above are way off of what is happening now. Ice reports well down into Mississippi and Alabama. There are now FZRN Advisories way down there into those states. Parts of the Memphis area are having an awful time on the roads. Just a little FZRN goes a long way on the roads. Now, how that translates to the east, who knows.

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OHX update:

 

 

 

000
FXUS64 KOHX 201651
AFDOHX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
1051 AM CST FRI FEB 20 2015

.UPDATE...TAKING A LOOK AT NEW 12Z DATA...NO BIG CHANGES. HAVE
MADE SOME ADJUSTMENTS TO ICE ACCUM AND SNOW TOTAL GRIDS...BUT
THESE ARE RELATIVELY MINOR...AND HEADLINES REMAIN THE SAME.

A COLD AIR MASS WAS IN PLACE OVER MID TN AT MID MORNING...WITH
TEMPERATURES IN THE TEENS AND DEW POINTS IN THE SINGLES. RADAR
SHOWED A BAND OF LIGHT REFLECTIVITIES ACROSS THE MID STATE...BUT
THIS ACTIVITY IS NOT REACHING THE GROUND AT THIS TIME. SNOW AND
SLEET IS REACHING THE GROUND BACK IN WEST TN...INCLUDING JACKSON
WHERE VSBYS HAVE BEEN DOWN TO 3/4 MILE.

WE EXPECT POCKETS OF FLURRIES TO DEVELOP OVER THE NEXT 2-3
HOURS...THEN SNOW WILL BECOME WIDESPREAD AFTER 2 PM. WE HAVE
RECEIVED A LOT OF QUESTIONS ABOUT RUSH HOUR...ESPECIALLY IN
NASHVILLE. THERE MAY BE LITTLE OR NO ACCUMULATION FOR BNA THROUGH
3 PM OR MAYBE 4 PM...BUT THINGS COULD GO DOWNHILL QUICKLY. FOR
DECIDING WHEN TO HEAD HOME...IT IS NOT ADVISED TO JUST LOOK OUT
THE WINDOW FOR SNOW TO START. IF EVERYBODY DOES...THERE WILL BE LOTS
OF PEOPLE ON THE ROADS WHEN THINGS ARE GETTING BAD. PLEASE PLAN
AHEAD.

BY 6 PM...SNOW AND SLEET IS EXPECTED TO BE FALLING OVER MUCH OF
THE MID STATE WITH ACCUMS ANYWHERE FROM ONE QUARTER TO 1 INCH.
FREEZING RAIN WILL BE DEVELOPING OVER THE SOUTHWEST COUNTIES.
THROUGH MIDNIGHT...WARMER AIR ALOFT WILL CHASE THE SNOW TO THE
EAST...AND SPREAD FREEZING RAIN ACROSS THE AREA. LATE IN THE
NIGHT...THE WARMER AIR WILL CHANGE THE WINTRY PRECIP OVER TO RAIN
FROM WEST TO EAST. THE LINE OF ALL LIQUID IS EXPECTED TO BE ALONG
THE TN RIVER ABOUT MIDNIGHT...I 65 AROUND 3 AM...AND THE PLATEAU
BY 9 AM. ONE ADJUSTMENT FROM THE PREVIOUS FORECAST IS TO LOWER ICE
TOTALS A LITTLE FOR OUR NORTHWEST COUNTIES. THIS RESULTS IN
EXPECTED ICE TOTALS OF A TENTH TO QUARTER GENERALLY SOUTHWEST OF I
24...WITH ONE QUARTER TO ONE HALF ON THE NORTHEAST SIDE OF I 24.
SNOW TOTALS ARE STILL EXPECTED TO BE ANYWHERE FROM ONE HALF TO
1.5 INCH.

TODAY...WE WILL BE LOOKING AT THE POTENTIAL FOR HEAVY RAINFALL
AFTER THIS WINTER EVENT AND WE WILL CONSIDER AND COORDINATE A
POSSIBLE FLOOD WATCH.

 

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I'm right at 19º right now. Temp has been rising fast all morning from a low of -12º. Granted, it's been beautiful blue skies all day. Not sure if we'll make it above freezing, but it's going to be close. Funny that after three days of model runs, we may very well be too warm to see any frozen types by the time precip gets here.

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MRX change over times:

 

 

 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
1259 PM EST FRI FEB 20 2015

.AVIATION...YET ANOTHER UPPER LEVEL TROUGH WILL BE BUILDING
SOUTHEAST THROUGH THE MISSISSIPPI VALLEY TONIGHT INTO SATURDAY WITH
MUCH WARMER AND UNFORTUNATELY MOIST AIR OVERSPREADING A VERY COLD
SURFACE AIRMASS. THIS MEANS THAT THERE WILL BE SNOW TRANSITIONING
TO SLEET AND FREEZING RAIN ACROSS THE GREAT VALLEY. EVENTUALLY THE
MIXED PRECIPITATION WILL CHANGE INTO RAIN AROUND 11Z AT
CHA...POSSIBLY 13Z AT TYS AND AROUND MID DAY AT TRI.
MODEL
FORECASTS CREATE MVFR CONDITIONS OR BETTER THROUGH THE EVENT.
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I'm right at 19º right now. Temp has been rising fast all morning from a low of -12º. Granted, it's been beautiful blue skies all day. Not sure if we'll make it above freezing, but it's going to be close. Funny that after three days of model runs, we may very well be too warm to see any frozen types by the time precip gets here.

I went from -11 to 18 quickly, but I've been stuck at 18 for a few hours now.

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