Well, there has been another shift in the forecast. This posting will be brief, but now the cold front will not pass us until 6:00 A.M. through Noon tomorrow. Primary risks are hail and maybe damaging winds. I have taken a look at the models, and it really doesn’t look like we will get more than a good lightning show. However, there will be plenty more days of severe weather to come! Here is a bit of the SPC forecast for tomorrow, a graphic or two, and a closing statement Mind you, this statement was made this morning and the forecast is most likely not as valid as it was, but it is still a general guideline for tomorrow…

...MIDWEST/LWR OH RVR VLY TO THE TN RVR VLY...
   BANDS/CLUSTERS OF TSTMS THAT DEVELOP OVER THE ERN PLAINS TODAY WILL
   CONTINUE ENE EARLY IN THE DAY 2 PERIOD ACROSS MOST OF THE REGION
   WITHIN A STRENGTHENING WARM/MOIST ADVECTION REGIME.  ISOLD STORMS
   MAY YIELD HAIL GIVEN THE EXPECTED STEEP MID-LVL LAPSE RATES.  

   PRIMARY SVR CONCERN WILL EVOLVE MID-LATE AFTN IN WAKE OF THIS
   ACTIVITY AND ALONG THE SFC OCCLUSION.  HERE...A TONGUE OF LWR 50S
   SFC DEW POINT WILL EXIST BENEATH A NEWD ADVANCING DRY SLOT/PLUME OF
   VERY STEEP MID-LVL LAPSE RATES.  SFC HEATING WILL BOOST INSTABILITY
   AND RESULT IN ADDITIONAL LOW-TOPPED VARIETY STG/SVR TSTMS OVER
   PORTIONS OF THE MIDWEST/LWR OH RVR VLY TO THE TN RVR VLY.  ISOLD SVR
   HAIL AND BRIEF TORNADOES WILL BE THE PRIMARY THREATS WITH THE SVR
   RISKS DIMINISHING AFTER SUNSET.

   ANOTHER ROUND OF CONVECTION MAY EVOLVE OVERNIGHT OVER THE LWR OH/TN
   RVR VLYS AS THE SECONDARY DISTURBANCE ROTATES TOWARD THE REGION.
   MOST OF THIS ACTIVITY WILL BE SUB-SVR AS THE PRIMARY INSTABILITY
   AXIS WILL BE RELEGATED TO THE GULF COASTAL REGION.

   ..RACY.. 03/10/2010

So, still be prepared for anything, but don't worry too much. Unless something 

drastic happens overnight (which is why you should prepare!), the threat wont be 

as great as it is to our west at the moment. I will attempt an update tomorrow 

morning, but still be prepared for anything... you just never know!   

I really need to start saving my enthusiasm for, oh, I don't know... a REAL threat?

THIS HAZARDOUS WEATHER OUTLOOK IS FOR MIDDLE TENNESSEE.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A DISTURBANCE ALOFT WILL BRING SHOWERS AND THUNDERSTORMS TO MIDDLE
TENNESSEE LATE TONIGHT. ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE
NEAR THE TENNESSEE RIVER. HEAVY RAIN AND PONDING OF WATER ON ROADS
MAY ALSO OCCUR WITH THESE STORMS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

ISOLATED STRONG THUNDERSTORMS WILL BE POSSIBLE ACROSS MIDDLE
TENNESSEE THURSDAY MORNING. LOOK FOR ANOTHER ROUND OF STORMS ON
FRIDAY. SOME STORMS MAY PRODUCE HAIL.

.SPOTTER INFORMATION STATEMENT...

EVEN THOUGH ANY SEVERE THUNDERSTORMS ARE EXPECTED TO BE BRIEF AND
ISOLATED, SPOTTERS ARE ENCOURAGED TO CLOSELY MONITOR WEATHER
CONDITIONS AND BE PREPARED TO CALL IN ANYTHING REACHING REPORTING
CRITERIA.

$$

So, keep an eye out on the weather tonight, but I don't expect anything much tonight. 

I know that this is a drastic change from the previous forecast, but that is what happens!

What the Storm Prediction Center says:

This is the Enhanced Thunderstorm Outlook, which is valid until 2 P.M. today. However, below is the SPC’s tornado outlook for today.

This is the text from the SPC regarding our area specifically. Head over to the SPC page for the rest.

...NE TX/ERN OK/SE KS INTO MO/AR AND THE MS VLY TODAY/TONIGHT...
   LOW-LVL MOISTENING WILL CONTINUE NWD AHEAD OF MERGING COLD FRONT/DRY
   LINE TODAY/TONIGHT...WITH SFC DEWPOINTS IN THE UPR 50S F EXPECTED BY
   LATE AFTN OVER ERN OK/AR.  A SEPARATE AREA OF RELATIVELY MOIST AIR
   WILL SPREAD N FROM THE AR/MS DELTA INTO SE MO AND WRN KY/TN.
   COUPLED WITH SFC HEATING AND COOL MID LVL TEMPERATURES...SETUP
   SHOULD YIELD SBCAPE OF 1000-1500 J/KG IN AR...AND VALUES AOA 1000
   J/KG FROM ERN OK INTO SRN MO/W TN.

   COMBINATION OF DESTABILIZATION AND STRONG ASCENT AHEAD OF NM UPR
   VORT SHOULD SUPPORT VIGOROUS STORM DEVELOPMENT ALONG AND AHEAD OF
   THE FRONT FROM SE KS THROUGH ERN OK INTO NE TX BY MID/LATE AFTN.
   THE STORMS SHOULD CONSOLIDATE INTO BROKEN BANDS AND MOVE/DEVELOP
   E/NE INTO MO/AR BY EARLY EVE.

   BAND OF 80+ KT SSWLY 500 MB FLOW SHIFTING ENE ATOP LOW-LVL SLY FLOW
   WILL BE FAVORABLE FOR SUPERCELLS.  HOWEVER...SUBSTANTIAL
   SPATIAL/TEMPORAL VARIATION OF WIND FIELD AHEAD OF COMPACT UPR
   VORT...AND NW-TO-SE VARIATION OF MOISTURE AVAILABILITY ACROSS REGION
   COMPLICATE FORECAST OF DOMINANT STORM MODE.  NEVERTHELESS...OVERALL
   COMBINATION OF STRENGTHENING INSTABILITY...SHEAR...AND LIFT SUGGEST
   STRONG LIKELIHOOD FOR SVR WEATHER...ESPECIALLY LARGE HAIL.
   TORNADOES ALSO WILL BE POSSIBLE...NOT ONLY WITH THE MORE DISCRETE
   STORMS THIS AFTN...BUT ALSO WITH BROKEN BANDS/LEWPS OVER AR/MO AND
   PERHAPS WRN TN TONIGHT/EARLY THU AS THE ACTIVITY ENCOUNTERS
   INCREASING MOISTURE MOVING N UP THE MS RVR VLY.

I have taken a look at the models, and it looks like we have a possible area of CAPE ranging in the 1000 J/Kg, but in mostly western Mid Tn areas. Lift index values are in the -5 area, and we have some 35-40 kt wind shear over Middle Tennessee. Storm motion will be east-northeast, and it looks like we have some ok levels of vorticity. Now I barely only have a clue to what vorticity is, so don’t ask me! All I know is it is a good ingredient to have for tornadoes. Today will also be an ok day because we have some decent moisture in the area, with temperatures reaching near 70. All of these things are why the SPC has included us in the 2% tornado risk, because there are enough ingredients there to have a a chance of a tornado. Mind you, it was only a few days ago in Oklahoma with a 2% risk that a large, stove-pipe tornado touched down! This is why you need to keep an eye on things today, because we are NOT exempt.

This is the hail probability graphic today, which we are also included in.

This is what our WFO in Nashville has to say about things…

THIS HAZARDOUS WEATHER OUTLOOK IS FOR MIDDLE TENNESSEE.

.DAY ONE…TODAY AND TONIGHT A STRONG COLD FRONT WILL PASS THROUGH MIDDLE TENNESSEE LATE TONIGHT. AS A RESULT, WIDESPREAD THUNDERSTORMS ARE EXPECTED ACROSS THE MID STATE. A FEW OF THESE STORMS MAY EVEN BECOME SEVERE, ESPECIALLY IN AREAS ALONG AND NEAR THE TENNESSEE RIVER. HEAVY RAIN AND PONDING OF WATER ON ROADS MAY ALSO OCCUR WITH THESE STORMS.

.DAYS TWO THROUGH SEVEN…THURSDAY THROUGH TUESDAY LOOK FOR ANOTHER ROUND OF STORMS ON FRIDAY. IT IS POSSIBLE THAT SOME OF THESE STORMS MAY PRODUCE HAIL.

.SPOTTER INFORMATION STATEMENT… EVEN THOUGH ANY SEVERE THUNDERSTORMS ARE EXPECTED TO BE BRIEF AND ISOLATED, SPOTTERS ARE ENCOURAGED TO CLOSELY MONITOR WEATHER CONDITIONS AND BE PREPARED TO CALL IN ANYTHING REACHING REPORTING CRITERIA.

$ SPOTTER THUNDERSTORM REPORTING CRITERIA…

TORNADO

FUNNEL CLOUD

FLOODING

HAIL >= 1/2 INCH

WINDS > 50 MPH (MEASURED)

STRUCTURAL DAMAGE

TREES OR POWER LINES DOWN

So, in summery, we do not have a “large” risk as it were, but there is still enough of a risk to warrant caution. Just get yourself prepared, keep an eye on the news and weather, change the batteries in your weather radio, etc, etc. Be expecting this storm system to move in LATE TONIGHT, and not this afternoon. I feel like that is what gives this storm system its danger, because the main force of it will occur after midnight through Friday morning. Nighttime thunderstorms are usually the killers. Now I am not saying we have some large risk and we need to run for the hills, but I do feel the need to warrant caution tonight.

I took a brief look at the twisterdata.com NAM models, and it looks like maximum CAPE values range in the 1000-1750 J/Kg, moisture will be decent, and just a little bit of wind shear. Lift Index levels will also bee in a good range, so we will keep an eye on that and hope for the best!

This is the Hazardous Weather Outlook for Middle Tennessee from the National Weather Service.

.DAYS TWO THROUGH SEVEN…TUESDAY THROUGH SUNDAY

AN UNSETTLED WEATHER PATTERN WILL DEVELOP OVER THE REGION WITH ON AND OFF CHANCES FOR THUNDERSTORMS TUESDAY NIGHT THROUGH FRIDAY. A FEW OF THE STORMS COULD BE STRONG TO SEVERE THROUGH THIS PERIOD. THE GREATEST PROBABILITY FOR SEVERE WEATHER WILL OCCUR WEDNESDAY EVENING THROUGH EARLY THURSDAY MORNING WITH A STRONG LOW PRESSURE AND COLD FRONT CROSSING THE REGION.

.SPOTTER INFORMATION STATEMENT… EVEN THOUGH ANY SEVERE THUNDERSTORMS ARE EXPECTED TO BE BRIEF AND ISOLATED, SPOTTERS ARE ENCOURAGED TO CLOSELY MONITOR WEATHER CONDITIONS AND BE PREPARED TO CALL IN ANYTHING REACHING REPORTING CRITERIA.

The Storm Prediction Center has not issued any convective outlooks for us, but the Arklatex area does have a pretty good risk on Wednesday.

Keep an eye on the weather the next week, it will be on/off thunderstorms and the National Weather Service isn’t ruling out severe weather. Be alert!

Currently only Base Reflectivity and Base Velocity in the lowest tilt have been upgraded. The NWS will be doing these upgrades in phases, until by the end of the year every tilt is included and the legacy products will stop being sent. Base Reflectivity has increased from 4-bit data to 8-bit data, but the pixel sizes have remained the same. That means that there is higher res data just within the same area of measurement. Base Velocity, however, has greatly reduced from 1km pixels to 250m or 275m (cant remember) pixel sizes, allowing for smaller, more accurate velocity measurements.  Here are a few examples below…

Base Reflectivity: (click for larger image)

(Legacy BR: Unsmoothed)

(High-Res BR: Unsmoothed)

Unfortunately I do not have an example of the Base Velocity, but you can take my word for it that it is a much better resolution!

If you have GRlevel3, you need to go to the GRlevelx owner forums and download the v1.71 update to view Southern region data.

One small thing to report on as I am sitting on the plane is that it looks as if snow will not show itself this week. If it does, it will be VERY little. Also, the National Weather Service has already started releasing higher res radar products for parts of the country! Our area is expected to get online the first week of March.

Updates will resume in March, so until then, au revoir!

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE NASHVILLE TN
310 PM CST FRI FEB 5 2010

...WINTER WEATHER ADVISORY PARTS OF MIDDLE TENNESSEE LATE TONIGHT
THROUGH EARLY SATURDAY MORNING...

.A LOW PRESSURE SYSTEM WILL MOVE ACROSS THE REGION WITH LIGHT
PRECIPITATION TONIGHT. THE PRECIPITATION WILL BE RAIN
EARLY...CHANGING TO LIGHT SNOW OVERNIGHT. SNOWFALL AMOUNTS AROUND
ONE INCH ARE POSSIBLE FOR NORTHERN MIDDLE TENNESSEE WITH 2 INCHES
POSSIBLE ON THE CUMBERLAND PLATEAU.

...WINTER WEATHER ADVISORY IN EFFECT FROM 10 PM THIS EVENING TO
10 AM CST SATURDAY...

THE NATIONAL WEATHER SERVICE IN NASHVILLE HAS ISSUED A WINTER
WEATHER ADVISORY FOR SNOW...WHICH IS IN EFFECT FROM 10 PM THIS
EVENING TO 10 AM CST SATURDAY.

* MAIN IMPACT: UP TO ONE INCH OF SNOW WILL FALL OVER NORTHERN
  MIDDLE TENNESSEE LATE TONIGHT. 1 TO 2 INCHES WILL FALL OVER THE
  CUMBERLAND PLATEAU AND SURROUNDING AREAS.

* OTHER IMPACTS: MOST OF THE ACCUMULATION WILL OCCUR ON GRASSY
  AREAS. SOME ROADS MAY BECOME SLICK.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER WEATHER ADVISORY MEANS THAT PERIODS OF SNOW...SLEET...OR
FREEZING RAIN WILL CAUSE TRAVEL DIFFICULTIES. BE PREPARED FOR
SLIPPERY ROADS AND LIMITED VISIBILITIES...AND USE CAUTION WHILE
DRIVING.

So, nothing major. Just don't be surprised when you start to see some snow falling! 

And do not even begin to think schools will be closed for this. Just a light dusting  

The National Weather Service is now expecting 6-12 inches of snow for Northern Middle Tennessee and the Nashville Area!

Also, there worst is yet to come…

The National Weather Service is saying the heaviest snow will come later this afternoon, causing for the most hazardous road conditions of the day.

.NOW…
AT 3 PM…WINTRY PRECIPITATION CONTINUES ACROSS MIDDLE TENNESSEE.
SNOW WAS BEING REPORTED OVER ALL OF THE MID STATE…WITH THE
HEAVIER SNOW…AND A FREEZING RAIN MIX…OVER THE SOUTHERN
COUNTIES. HIGHER ACCUMULATIONS WILL BECOME MORE PREVALENT THIS
AFTERNOON AND TONIGHT AS PRECIPITATION BECOMES HEAVIER AND MORE
WIDESPREAD. ROADS WILL BECOME INCREASINGLY SLIPPERY AS MORE SNOW
AND ICE ACCUMULATES…ESPECIALLY ALONG BRIDGES AND OVERPASSES.
MOTORISTS ARE URGED TO USE EXTREME CAUTION IF TRAVEL IS NECESSARY.

$$

MTP

Both the National Weather Service and the NAM forecast model agree that by the end of saturday Northern Middle Tennessee with have up to and over 6 inches of snow! Look over the graphics below. This first graphic is the expected snowfall today. It looks like todays total snow/ice accumulations will be up to 3 inches, with weekend totals at 6.

And this is the expected snowfall through the weekend.

Here is a radar image I took this morning. It is a Level II radar image, so it it much higher res than what is publicly used on the internet, by news media, etc. Note the areas of red on the radar; that is not snow. That area is currently experiencing freezing rain/sleet, which could be hazardous. (click to enlarge)

Middle Tennessee is still under a Winter Storm Watch, which means hazardous winter conditions are imminent and appropriate actions should be taken to protect life and property.

(from the National Weather Service)

...THE WINTER STORM IS MOVING IN...

AT 930 AM...RADAR INDICATES THAT LIGHT TO MODERATE SNOWFALL IS NOW
COVERING A LARGE PORTION OF MIDDLE TN. MUCH OF THE PRECIPITATION
OVER THE PLATEAU AREA WAS NOT YET REACHING THE GROUND. SOME SLEET
WAS MIXING IN WITH THE SNOW ACROSS SOUTHERN AREAS.

PRIOR TO NOON TODAY...LOOK FOR UP TO 1 INCH OF SNOWFALL TO
OCCUR...PRIMARILY ACROSS THE NORTHWESTERN QUARTER OF THE MID STATE...
INCLUDING THE NASHVILLE METRO AREA.

THE WINTER STORM WARNING PERIOD IS STILL SCHEDULED TO BEGIN AT
NOON TODAY. THIS AFTERNOON...LOOK FOR THE PRECIPITATION TO BECOME
HEAVIER WITH ACCUMULATING SNOWFALL...SLEET AND SOME ICE
ACCUMULATION EXPECTED FOR THE ENTIRE MID STATE.

MOTORISTS ARE URGED TO DRIVE WITH EXTREME CAUTION. A TRANSITION
TO VERY TREACHEROUS DRIVING CONDITIONS IS EXPECTED AS WE GO
THROUGH THE DAY. IN FACT...SOME ROADS WILL LIKELY BECOME IMPASSABLE
AS WE MOVE TOWARD THIS EVENING AND INTO TONIGHT.

POWER OUTAGES MAY ALSO BE A POTENTIAL PROBLEM TONIGHT...AS THE
WEIGHT FROM THE HEAVY SNOW CAN SNAP TREE LIMBS AND BRING DOWN
TREES  ACROSS THE AREA.

STAY TUNED TO NOAA WEATHER RADIO OR YOUR LOCAL TELEVISION STATION
FOR FUTURE UPDATES.

Enjoy your snow day everyone, and be safe! Be looking out for future posts with measured snowfall amounts, cool pictures, and more! If you have any snow pictures you would like to send in to be shown off, go to the “about us” and then the “contact us” page!

This image was taken as of 4:00 PM CST.

Northern portions of the mid state are expected to have up to 4 inches of snow, with lower portions having snow/sleet/ice all by the end of Friday. Saturday accumulations could add an inch or two more to snowfall totals. The NAM forecast shows a possibility for up to 6 inches of snow, but I do not know what factors contribute to the model. So I cannot say that this will be the outcome. Models are supposed to be used with other information and the forecaster’s knowledge, and I don’t have that much… that is why there are the people at the NWS who do this for a living.

Lastly, here is the winter storm warning text from the National Weather Service.

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE NASHVILLE TN
336 PM CST THU JAN 28 2010

...WINTER STORM WARNING FOR NORTH MIDDLE TENNESSEE FRIDAY AND
FRIDAY NIGHT...

.A LOW PRESSURE SYSTEM PASSING TO OUR SOUTH WILL BEGIN SPREADING
PRECIPITATION ACROSS NORTH MIDDLE TENNESSEE EARLY FRIDAY MORNING.
SNOW...SLEET..AND FREEZING RAIN WILL DEVELOP ACROSS THE AREA...
WITH 3 TO 8 INCHES POSSIBLE FRIDAY THROUGH FRIDAY NIGHT NORTH...
1 TO 3 SOUTH. ADDITIONALLY ONE-QUARTER TO ONE-HALF INCH OF ICE IS
LIKELY.

TNZ005>011-022>034-057-059-062>066-291000-
/O.UPG.KOHX.WS.A.0002.100129T1200Z-100130T1200Z/
/O.NEW.KOHX.WS.W.0001.100129T1200Z-100130T1200Z/
STEWART-MONTGOMERY-ROBERTSON-SUMNER-MACON-CLAY-PICKETT-BENTON-
HOUSTON-HUMPHREYS-DICKSON-CHEATHAM-DAVIDSON-WILSON-TROUSDALE-
SMITH-JACKSON-PUTNAM-OVERTON-FENTRESS-HICKMAN-WILLIAMSON-
RUTHERFORD-CANNON-DEKALB-WHITE-CUMBERLAND-
INCLUDING THE CITIES OF...DOVER...CLARKSVILLE...SPRINGFIELD...
GALLATIN...LAFAYETTE...CELINA...BYRDSTOWN...CAMDEN...ERIN...
WAVERLY...DICKSON...ASHLAND CITY...KINGSTON SPRINGS...NASHVILLE...
LEBANON...MOUNT JULIET...HARTSVILLE...CARTHAGE...GAINESBORO...
COOKEVILLE...LIVINGSTON...JAMESTOWN...ALLARDT...CENTERVILLE...
FRANKLIN...BRENTWOOD...MURFREESBORO...WOODBURY...SMITHVILLE...
SPARTA...CROSSVILLE...FAIRFIELD GLADE
336 PM CST THU JAN 28 2010

...WINTER STORM WARNING IN EFFECT FROM 6 AM FRIDAY TO 6 AM CST
SATURDAY...

* MAIN IMPACT: ON FRIDAY...1-4 INCHES OF SNOW. ONE-QUARTER TO ONE-
  HALF INCH OF ICE.

* FRIDAY NIGHT...2-4 ADDITIONAL INCHES OF SNOW. ONE-QUARTER INCH
  OF ICE.

* OTHER IMPACTS: ROADS AND BRIDGES WILL BECOME SLIPPERY AND
  DANGEROUS FOR DRIVING. GUSTY WINDS MAY CAUSE DRIFTING SNOW...
  AND WIND CHILLS FRIDAY NIGHT WILL DROP INTO THE TEENS AND SINGLE
  DIGITS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WARNING MEANS SIGNIFICANT AMOUNTS OF SNOW...
SLEET...AND ICE ARE EXPECTED OR OCCURRING. STRONG WINDS ARE ALSO
POSSIBLE.  THIS WILL MAKE TRAVEL VERY HAZARDOUS OR IMPOSSIBLE.

&&

$$