…GULF COAST STATES TO SERN ATLANTIC COAST…

AS MENTIONED IN THE SYNOPSIS…SEVERAL MIDLEVEL IMPULSES ARE EVIDENT IN MORNING WATER VAPOR IMAGERY TRANSLATING GENERALLY EWD ALONG LOW-LEVEL BAROCLINIC ZONE. VISIBLE SATELLITE IMAGERY SHOWS MORE EXTENSIVE CLOUD COVER THIS MORNING ACROSS THE TN VALLEY INTO THE CNTRL/SRN APPALACHIANS. HOWEVER…AREAS TO THE S WILL LIKELY EXPERIENCE STRONG DAYTIME HEATING. WHEN COUPLED WITH LOWER/MID 70S DEWPOINTS…ENVIRONMENT WILL BECOME MODERATE TO STRONGLY UNSTABLE BY AFTERNOON. ALSO OF NOTE…12Z OBSERVED SOUNDINGS AND CURRENT VWP DATA SUGGEST A BELT OF 30-35 KT FLOW PRESENT IN THE 3-6 KM AGL LAYER…WHICH WHEN COMBINED WITH THE STRONG INSTABILITY WILL LIKELY FOSTER CORRIDORS OF MORE INTENSE STORMS…PRIMARY IN ADVANCE OF THE MORE PERSISTENT MIDLEVEL IMPULSES. THE PRIMARY HAZARD WITH THESE STORMS WILL BE DAMAGING WIND GUSTS.

The clouds preventing heating have, for the most part, dissipated. All that remains are lower level cumulous pockets and those wont affect how the atmosphere heats. Now that the atmosphere is heating, we will gain some fairly strong CAPE values, but mainly by evening. These storms look like they will show up mainly at or after 7 PM, with 2-3 j/kg CAPE and some pretty nice Helicity values. I haven’t seen helicity like this over Tennessee in a while, so it could be nice. This helicity will also allow for the possibility for tornadoes, with the EHI model showing values ranging from 1-3 over a large area, mainly over western portions of the mid state.

So, in summary…

Thunderstorms will be widespread across the state, mainly this evening but a scattered thunderstorm cannot be ruled out before then. There will be large amounts of instability and shear, allowing for thunderstorms with threats mainly being damaging winds/hail. Tornadoes cannot be ruled out as well.

I am hoping to catch one of the earlier storms, and maybe even tonight’s storms. Check back for updates!

Update: all of Middle Tennessee is under a Flash Flood Watch

This outflow boundary that is surging ahead of this line can do one of two things. On one side, it can act as a lifting mechanism, creating more thunderstorms. Or, on the other side, it can cut off and kill these current thunderstorm’s updrafts, causing it all to die. With the current speed and trajectory of the outflow boundary (also known as a gust front), I am guessing it will do the latter. I will keep monitoring things and radar and update as things happen.

The SPC has placed all of Middle Tennessee under a Slight Risk for severe storms today. We have FINALLY picked up some wind shear, so now it looks more favorable for longer living and more severe storms as opposed to the pulse storms we have been having all week. Here is what the SPC says about today…

…TN VLY/SRN APPALACHIANS INTO ERN KY…NC…SRN VA…

MODERATE TO STRONG INSTABILITY WILL DEVELOP WITH DAYTIME HEATING ALONG PORTION OF COLD FRONT CROSSING PARTS OF KY/TN…AND ALONG PREFRONTAL TROUGH OVER VA/NC. MID/UPR LVL FLOW AND ASCENT WILL INCREASE OVER THESE AREAS AS REGION IS GLANCED BY SRN FRINGE OF GRT LKS TROUGH. 35-40 KT WNWLY 700 MB WINDS COULD SUPPORT ORGANIZED STORMS WITH DMGG WIND/HAIL…ESPECIALLY OVER NRN PARTS OF THE REGION. THE SVR THREAT COULD PERSIST INTO MID EVE IN VA/NC.

The SPC even dared to include us in todays tornado risk. At the moment it is a very low risk, but I could honestly care less. Even a small risk gives me hope for something! The models do agree with the possibility of a weak tornado, thanks to the wind shear we have today. However, if a tornado were to develop I would imagine it would be brief. Still, a tornado is a tornado and there is a chance (albeit extremely small) for one today.

So, at the moment a cold front is digging southeast towards us. This will be the mechanism to initiate storms today, and you can see on this radar image that it is already storming our way. My guess is that scattered thunderstorms will arrive in the northern part of the state between 11 AM and 12 PM. However there is a lot of room for error in that guess, so don’t hold me too hard to it. Main risk is large hail and damaging winds, so be looking out for that.

THE NWS STORM PREDICTION CENTER HAS ISSUED A SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

NORTHEASTERN             ARKANSAS

SOUTHERN KENTUCKY

MISSOURI BOOTHEEL

FAR NORTHWESTERN MISSISSIPPI

WESTERN AND MIDDLE TENNESSEE

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 215 PM UNTIL 800 PM CDT.

HAIL TO 1.5 INCHES IN DIAMETER…THUNDERSTORM WIND GUSTS TO 70 MPH…AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

DISCUSSION…THUNDERSTORMS HAVE DEVELOPED ALONG A ZONE OF WEAK CONVERGENCE IN NERN AR/WRN TN AND ARE EXPECTED TO DEVELOP NEWD INTO SRN KY. STRONG INSTABILITY COMBINED WITH STRONGER WINDS ALOFT WILL LIKELY RESULT IN STORMS WITH SEVERE HAIL…LOCALIZED DOWNBURSTS AND HEAVY RAINFALL.

The probabilities for the watch are:

Tornadoes: Very Low (<5%)

EF-2+ Tornadoes: Very Low (<2%)

Severe Wind: Low [10 or more wind events (20%)]

65 kt+ Wind: Low (20%)

Severe Hail: Moderate [10 or more hail events (30%)]

2″+ Hail: Low (20%)

Probability of 6 or more combined severe hail/wind events (60%)

The tornado risk for today is nearly non existent due to lack of helicity (wind shear), and therefore the SPC doesn’t even show a tornado risk over Tennessee. I don’t know what the SPC is looking at, but they are saying that there is enough deep layer shear to sustain these multicell lines, and warrant the risk of hail and damaging winds. I sure hope they are right, because I am itching for a good storm! There are great CAPE values for the day, and I have also noticed that there is very weak capping over Middle Tennessee today. This may be beneficial in preventing the weaker storms from developing. Then again, maybe not… I am still learning a lot about forecasting, so who knows. Enough of my blabbering, here is what the SPC has to say.

…DELMARVA WWD ACROSS THE SRN LOWER OH AND TN VALLEYS…

SEVERAL FEATURES SHOULD AID IN SCATTERED TO NUMEROUS THUNDERSTORMS DEVELOPING ACROSS THE REGION THROUGH THE AFTERNOON HOURS. FIRST FEATURE IS REMNANT MCV…CURRENTLY APPROACHING WRN PA. CURRENT MOTION/EXTRAPOLATION PLACES THIS FEATURE INTO S CENTRAL PA/MD PANHANDLE BY MID AFTERNOON. WEAK CONVECTION HAS ALREADY DEVELOPED AHEAD OF THIS SYSTEM OVER WV…AND SHOULD INTENSIFY AS MOVES INTO VA/MD PANHANDLE/SRN PA THIS AFTERNOON… REFERENCE MESOSCALE DISCUSSION 784.

FURTHER WEST…ANOTHER WEAK SURFACE LOW WAS LOCATED IN FAR NWRN OH…WITH A SURFACE TROUGH EXTENDING WSWWD INTO CENTRAL MO. THIS TROUGH WILL MOVE SLOWLY SWD AND CONVERGENCE WILL BE ENHANCED AHEAD OF IT AS AN UPPER THERMAL TROUGH SHIFTS EWD ACROSS THE TN/OH VALLEYS. DEEP LAYER SHEAR AT 20-30 KT WILL BE SUFFICIENT FOR SUSTAINED MULTICELL STORMS…AND IN CONJUNCTION WITH MODERATE INSTABILITY…SEVERE HAIL AND DAMAGING WINDS WILL BE POSSIBLE DURING THE AFTERNOON/EARLY EVENING HOURS.

Right now there is a mesoscale discussion in effect for western Tn, where a Severe Thunderstorm Watch appears possible. There may be one issued for northern Mid Tn later, but for now I will post the discussion.

AREAS AFFECTED…

NERN AR…BOOT HEEL OF MO…WRN TN…KY CONCERNING…

SEVERE POTENTIAL…WATCH POSSIBLE

VALID 031758Z – 031900Z

A PRE-FRONTAL ZONE OF LOW LEVEL CONFLUENCE CURRENTLY EXTENDS FROM NERN AR…NEWD ALONG THE OH RIVER INTO NRN KY. THIS AXIS WILL LIKELY BECOME THE FOCUS FOR STRONG THUNDERSTORM DEVELOPMENT OVER THE NEXT FEW HOURS AS BOUNDARY LAYER CONTINUES TO WARM/DESTABILIZE. GIVEN THE MARGINAL DEEP LAYER SHEAR IT APPEARS MULTI-CELL UPDRAFTS WILL BE COMMON WITHIN MODERATELY UNSTABLE AIRMASS. LOCALLY STRONG DOWNBURSTS AND HAIL COULD ACCOMPANY THE MORE ORGANIZED STORMS.

So, updates will come later as things progress. I would say it is safe to assume that if you are within the slight risk area, you will see some t-storms today. I just took a look at the SPC Hourly Mesoscale Analysis, and i see more favor in those models. As you can see, thunderstorms are already developing in western Tn. I will be sure to update if we get a severe thunderstorm watch.

…LWR MS/TN VLYS ENE TO THE MID-ATLANTIC…

BANDS OF MAINLY ELEVATED TSTMS WILL CONTINUE ALONG AND N AFOREMENTIONED FRONT AND ASSOCIATED OUTFLOW BOUNDARIES FROM THE SRN OZARKS ENE TO THE MID ATLANTIC STATES THROUGH THIS MORNING AS MOIST /WITH PW AOA 1.50 INCHES/ LOW-LVL FLOW CONTINUES. COMBINED WITH MODERATE TO STRONG HEATING…SUFFICIENT CAPE /2000-3000 J PER KG/ SHOULD DEVELOP FOR NUMEROUS NEW STORMS ALONG THE SRN FRINGES OF MORNING ACTIVITY. GLANCING INFLUENCE OF GRT LKS TROUGH MAY SUPPORT ORGANIZED ACTIVITY FROM KY NEWD TO THE MID ATLANTIC CST.

40-45 KT WSW MID-LVL FLOW ON NRN FRINGE OF UPR RIDGE SHOULD SUPPORT ORGANIZED STORMS/STORM CLUSTERS AND PERHAPS MARGINAL SUPERCELLS…ESPECIALLY FROM KY/TN TO THE CNTRL APPALACHIANS…AND OVER CNTRL/SRN PA TO THE MID ATLANTIC CST. EMBEDDED BOWS MAY YIELD BOTH DMGG WIND GUSTS AND SVR HAIL. THE SVR THREAT SHOULD DIMINISH THIS EVE.

Also, this risk will continue throughout the weekend, with severe thunderstorms expected tomorrow (saturday) and possibly even sunday night. When all is said and done, a possible 2-3 inches, if not locally higher, will have been dropped on the state. This may cause a few flood problems with the already bloated rivers, so keep an eye out. Click on this image to the right to show an animation of how the next few days will pan out. Also, I thought I would post what the Hazardous Weather Outlook says about the next few days.

.DAYS TWO THROUGH SEVEN…SATURDAY THROUGH THURSDAY

THE COLD FRONT THAT PASSES THROUGH TODAY…WILL BECOME STATIONARY NEAR THE ALABAMA BORDER ON SATURDAY…THEN BEGIN MOVING NORTH AS A WARM FRONT BY SUNDAY. ISOLATED SEVERE THUNDERSTORMS WILL REMAIN POSSIBLE ON SATURDAY…WITH DAMAGING WIND GUSTS…LARGE HAIL…AND HEAVY DOWNPOURS.

IN ADDITION TO THE SEVERE WEATHER POSSIBLE ON SATURDAY…MIDDLE TENNESSEE IS EXPECTED TO RECEIVE BETWEEN TWO AND THREE INCHES OF RAINFALL THIS WEEKEND AND INTO MONDAY…WITH LOCALLY HIGHER AMOUNTS POSSIBLE. FLOOD PROBLEMS MAY DEVELOP AS THE WEEKEND PROGRESSES… ESPECIALLY IN AREAS WHERE HEAVY THUNDERSTORM RAINS REPEATEDLY OCCUR.

Currently there are storm firing up around Middle Tennessee, on with a severe thunderstorm warning on it for large hail and winds in excess of 60 MPH. Thunderstorms are expected to progress as the day goes on, and then convection will weaken by evening hours. Here is todays HWO.

.DAY ONE…TODAY AND TONIGHT

A COLD FRONT WILL PUSH ACROSS THE MID STATE TODAY AND PRODUCE THE LIKELIHOOD FOR THUNDERSTORMS…A FEW OF WHICH COULD BECOME SEVERE… WITH DAMAGING WIND GUSTS…LARGE HAIL…AND HEAVY DOWNPOURS.

Pretty self explanatory, isn’t it? I took a brief look at the RUC forecast models, and was quite shocked at how much instability there is. Right now we have roughly 3000 j/kg CAPE values across a large portion of the state! It made me wonder why we were under such a minimal risk… well, I took a look at the helicity forecast and saw why. We have VERY little wind shear, only enough to support hail risk. Tornadoes seem unlikely at this point, due to the severe lack of wind shear. So don’t expect anything too crazy. You may see some decent sized hail, but other than that the severity is small.

A BROKEN BAND OF SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS THE AREA TONIGHT WITH PASSAGE OF A COLD FRONT. BRIEF DOWNPOURS ARE EXPECTED…WITH QPF AMOUNTS UNDER ONE QUARTER INCH. SOME OF THE STORMS COULD BE BRIEFLY SEVERE WITH STRONG WINDS BETWEEN 6 PM AND MIDNIGHT.

Some of the models have changed since then, but it is the same general idea. Before I get any further, some of you are probably wondering if this will affect any of the flooding. The answer is no. As said in the above statement, rainfall will be under 1/4 of an inch, and also very localized if more. This should not be a continuance of the flooding, so do not worry there. This cold front will pass fairly quickly and won’t linger like last weekend, which caused the flooding.

Now, it has been a VERY long time since I have done this, so I am rather excited. I will be pulling out the good ‘ol Skew-T chart! For those who don’t know, a Skew-T chart is a product that shows different characteristics of the atmosphere for that hour. Weather balloons are sent up, and they collect data that is compiled onto the chart.  Now, a strong reminder is that a Skew-T chart is only valid FOR THE HOUR IT WAS CREATED. However, we can use it to look at the characteristics of the atmosphere that may apply to the whole day.

Moving on, the Skew-T chart has picked up a nice little bit of instability, and a really strong cap. Instability is expected to increase throughout the day as daytime heating weakens ad eventually breaks the cap. That will happen around the same time the cold front pushes through, allowing thunderstorm development. Also, the nice little indent in the dewpoint part of the graph shows an ok potential for hail, one of the main threats.

(click on images to enlarge them) Now, here is the part that gets a little tricky… earlier models were showing not so great levels of wind shear, but as the day has progressed the models have increased the amount of helicity. Same goes for EHI . The EHI models were low, but now are pretty high. What does this mean? I have no idea… I am not too terribly experienced, but it is possible we will have a slightly larger tornado risk issued later. That is just speculation, I am still learning a lot but we will see how things pan out. Plus, with Lift Index at -6 I have no doubt there will be some form of severe weather, I just doubt how severe it will be. It will be interesting to see how it all pans out, so check back for updates!

Middle Tennessee is under 3 different zones of risk. Far eastern is under a HIGH risk, central Middle Tennessee is under a MODERATE risk, and the rest is under a slight risk. There will be a continuance of a slight risk through tomorrow, of which will be discussed later. Here is the Hazardous Weather Outlook:

…FLASH FLOOD WATCH IN EFFECT THROUGH MONDAY MORNING…

THIS HAZARDOUS WEATHER OUTLOOK IS FOR MIDDLE TENNESSEE.

.DAY ONE…TODAY AND TONIGHT

SEVERE THUNDERSTORMS ARE POSSIBLE TODAY AND TONIGHT AHEAD OF A SLOW MOVING COLD FRONT. THUNDERSTORMS WILL PRODUCE HEAVY RAINFALL WITH FLASH FLOODING WEST OF INTERSTATE 24. MORE INFORMATION IS AVAILABLE ON THE INTERNET AT WEATHER.GOV OR BY LISTENING TO NOAA WEATHER RADIO.

.DAYS TWO THROUGH SEVEN…SUNDAY THROUGH FRIDAY

THE THREAT OF MORE SEVERE THUNDERSTORMS AND FLOODING WILL CONTINUE SUNDAY AND INTO EARLY MONDAY. MORE INFORMATION IS AVAILABLE ON THE INTERNET AT WEATHER.GOV OR BY LISTENING TO NOAA WEATHER RADIO. .SPOTTER INFORMATION STATEMENT… REPORTS FROM TRAINED WEATHER SPOTTERS WILL LIKELY BE NEEDED.

Severely heavy rain has fallen today, with flash flood reports all across the states. The creek in my front yard, which you can see in the previous post’s video, became so flooded that it could no longer pass under the road and started flowing over it. 3-6 inches of water began rushing over the road, causing for hazardous driving conditions. The creek itself became well over 6 feet deep!

Western and central portions of Middle Tennessee are still under a Significant/15% tornado risk, and a new Tornado Watch will be issued by the SPC. However, I will post the current watch message here.

DISCUSSION…NUMEROUS THUNDERSTORMS CONTINUE TO AFFECT PORTIONS OF TN/MS/LA THIS MORNING…WITHIN A VERY MOIST AND UNSTABLE AIRMASS. WIDESPREAD WEAK LOW LEVEL WARM ADVECTION WILL LIKELY MAINTAIN THE RISK OF DISCRETE STORM DEVELOPMENT. LOW LEVEL VERTICAL SHEAR THROUGHOUT THE REGION IS FAVORABLE FOR SUPERCELLS AND TORNADOES. POCKETS OF DAYTIME HEATING THIS AFTERNOON WILL FURTHER INCREASE THE RISK OF SEVERE STORMS.

As I said above, I would discuss tomorrow’s risk too. But, I again find myself lacking in time so I will just post the SPC discussion.

…THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER MS VALLEY…TN VALLEY…OH VALLEY…CNTRL APPALACHIAN AND NRN APPALACHIANS…

…TN VALLEY/LOWER MS VALLEY…

A LARGE AND POTENTIALLY SEVERE MCS SHOULD BE ONGOING AT THE BEGINNING OF THE PERIOD FROM THE OH VALLEY SSWWD ACROSS WRN TN AND MS LOCATED ALONG THE WRN EDGE OF A PRONOUNCED 50 TO 60 KT LOW-LEVEL JET. MODEL FORECASTS GRADUALLY MOVE THE MCS EWD DURING THE DAY INTO THE UPPER OH VALLEY AND ACROSS THE TN VALLEY. MODEL FORECASTS ACROSS THE OH AND TN VALLEYS SUNDAY SHOW STRONG DEEP LAYER SHEAR PROFILES ASSOCIATED WITH A BROAD 90 TO 100 KT MID-LEVEL JET. THE AMOUNT OF SHEAR WHICH COMBINED WITH WARMING SFC TEMPS JUST AHEAD OF THE CONVECTION SHOULD KEEP PORTIONS OF THE LINE SEVERE INTO THE EARLY AFTERNOON. MODEL FORECASTS BY SUNDAY AFTERNOON DEVELOP A ZONE OF MODERATE INSTABILITY FROM MS NNEWD ACROSS NRN AL INTO MIDDLE TN WHERE 0-6 KM SHEAR SHOULD BE 50 TO 60 KT. THIS ENVIRONMENT SHOULD BE FAVORABLE FOR SUPERCELLS AND BOWING-LINE SEGMENTS. THE MORE DOMINANT SUPERCELLS THAT MOVE EWD INTO A WELL-FOCUSED LOW-LEVEL JET ACROSS THE TN VALLEY LATE SUNDAY AFTERNOON SHOULD PRODUCE TORNADOES WITH A STRONG TORNADO POSSIBLE. BOWING LINE-SEGMENTS SHOULD BE CAPABLE OF PRODUCING ISOLATED VERY STRONG DAMAGING WIND GUSTS. THE LOW-LEVEL JET IS FORECAST TO REMAIN WELL-DEVELOPED ACROSS THE TN VALLEY SUNDAY EVENING WHICH COMBINED WITH MODERATE INSTABILITY MAY SUPPORT THE DEVELOPMENT OF A SEVERE LINEAR MCS LATE SUNDAY EVENING WITH A SEVERE THREAT CONTINUING THROUGH MUCH OF THE NIGHT. AN UPGRADE TO MODERATE RISK MAY BE NECESSARY ACROSS PARTS OF THE TN VALLEY AS CONFIDENCE INCREASES CONCERNING THE MODEL SOLUTIONS.

Be safe, and remember: TURN AROUND, DON’T DROWN!

The Storm Prediction Center issued another tornado watch for most of middle Tennessee, regarding the new HIGH risk scenario. The probabilities are astounding. >95% for tornadoes, and 90% for EF-2 through EF-5 tornadoes! Please take appropriate caution this evening, as I have no idea when this will strike. Here is the text from the watch and the SPC outlook.

Tornado Watch:

DISCUSSION…SEVERE THUNDERSTORMS CONTINUE TO INCREASE IN BOTH NUMBER AND INTENSITY AHEAD OF THE RAPIDLY DEEPENING LOW AND UPPER TROUGH MOVING TOWARD THE MID MISSISSIPPI VALLEY. VERY STRONG DEEP LAYER SHEAR COUPLED WITH VERY MOIST/UNSTABLE AIR MASS CONTINUES TO SUPPORT BOTH TORNADIC SUPERCELLS AND VERY DAMAGING WINDS. THREAT WILL RAPIDLY SPREAD NORTH AND EAST ACROSS THE WATCH THRU THE AFTERNOON. THE RISK FOR LARGE LONG TRACK TORNADOES WILL BE A THREAT AS WELL.

And from the High Risk outlook:

…MS/AL/TN/KY/FAR NORTHEAST AR/MO BOOTHEEL… HAVE EXPANDED CATEGORICAL HIGH RISK NORTHWARD ACROSS PORTIONS OF WESTERN TN/WESTERN KY. UPPER 60S F/LOWER 70S F SURFACE DEWPOINTS ARE IN PLACE WITHIN A PRISTINE WARM/MOIST SECTOR ALONG/SOUTH OF A WARM FRONT…WHICH IS EXPECTED TO CONTINUE TO RETREAT NORTHWARD ACROSS THE CENTRAL GULF COAST STATES/TN VALLEY INTO THIS EVENING. RAPIDLY STRENGTHENING LOW LEVEL WINDS AND WARM ADVECTION WILL CONTINUE TO LEAD TO SEMI-DISCRETE CONVECTIVE SUPERCELLULAR INITIATION…WITH MORE OF A MIXED SUPERCELLULAR/QUASI-LINEAR MODE PROBABLE NORTHWARD TOWARD THE OH/MS RIVER CONFLUENCE. STRONG/ELONGATED LOW LEVEL HODOGRAPHS WILL SUPPORT THE POSSIBILITY OF STRONG AND DAMAGING TORNADOES…ALONG WITH DAMAGING WINDS AND LARGE HAIL.

I have also just heard that Jasoo, Ms. is completely obliterated by a massive wedge. This same system is heading our way, so please be safe!

Tornadoes: High

EF-2+ Tornadoes: Moderate

Severe wind: High

65 kt+ Wind: Moderate

Severe Hail: Moderate

2″+ Hail: Low

The watch spans an area from Arkansas to Kentucky, and all in between. The image of the watch is above. Also, here is the text from the tornado watch, giving a bit more info on the situation.

DISCUSSION…STRENGTHENING/MOISTENING WAA/SSWLY LLJ EXPECTED TO SUPPORT CONTINUED DEVELOPMENT OF SUSTAINED STORMS/COMPLEX SUPERCELL STRUCTURES AND MESOSYSTEMS WITH AN ATTENDANT THREAT FOR TORNADOES ACROSS A SIZABLE PART OF THE LWR MS AND LWR TN VLY THROUGH EARLY SAT.

However, the worst is yet to come. As the warm front pushes in tonight, the cold front will do so tomorrow which will bring out greatest chance for severe weather. These are the only counties in risk for severe weather TONIGHT ONLY, but tomorrow everyone is under equal risk. The hourly weather graph doesn’t give any hope in figuring out when the next (and worse) round will come, but our local National Weather Service has updated their Hazardous Weather Outlook, which gives out a lot more information on timing. From the NWS’s HWO:

1000 PM CDT FRI APR 23 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR MIDDLE TENNESSEE. .DAY ONE…TONIGHT

WITH A DEVELOPING COLD FRONT APPROACHING FROM THE WEST…THUNDERSTORMS MAY DEVELOP LATE TONIGHT. A FEW OF THESE STORMS MAY EVEN BECOME SEVERE IN AREAS WEST OF NASHVILLE BEFORE DAYBREAK.

.DAYS TWO THROUGH SEVEN…SATURDAY THROUGH THURSDAY

LOOK FOR WIDESPREAD STORMS TO DEVELOP SATURDAY AND SATURDAY EVENING AS A STRONG COLD FRONT PASSES THROUGH MIDDLE TENNESSEE. THE ENTIRE MID STATE IS UNDER A MODERATE RISK OF SEVERE WEATHER. SEVERE STORMS MAY OCCUR AT ANY TIME DURING THIS PERIOD…BUT WILL BE MOST LIKELY DURING THE AFTERNOON THROUGH EARLY EVENING. DAMAGING STRAIGHT-LINE WINDS…LARGE HAIL…AND ISOLATED TORNADOES ARE ALL POSSIBLE WITH THIS SYSTEM.

.SPOTTER INFORMATION STATEMENT…

A SIGNIFICANT SEVERE WEATHER EVENT IS EXPECTED. SPOTTER REPORTS WILL BE NEEDED.

But wait, there’s more!

A MODERATE RISK MEANS THAT THERE IS A 45 PERCENT CHANCE OF A SEVERE WEATHER EVENT (DAMAGING WINDS…LARGE HAIL OR TORNADOES) OCCURRING WITHIN 25 MILES OF ANY GIVEN LOCATION IN MIDDLE TENNESSEE.

THIS EVENING…A WARM FRONT HAS MOVED NORTH INTO CENTRAL KENTUCKY WITH OF A LARGE AREA OF SHOWERS MOVING INTO SOUTHERN PORTIONS OF THE MID STATE. SCATTERED SHOWERS HAVE ALSO DEVELOPED AND ARE MOVING ACROSS AREAS ALONG AND NORTH OF INTERSTATE 40 AND GENERALLY ALONG AND WEST OF INTERSTATE 24. THIS WARM FRONT WILL CONTINUE TO LIFT NORTH OVERNIGHT…PROVIDING FOR INCREASING MOISTURE AND INSTABILITY ACROSS THE ENTIRE MID STATE. THIS..ALONG WITH STRENGTHENING LOWER LEVEL AND UPPER LEVEL WINDS…COULD BRING A ROUND OF SEVERE THUNDERSTORMS INTO WESTERN PORTIONS OF MIDDLE TENNESSEE OVERNIGHT… ESPECIALLY JUST ALONG AND EAST OF THE TENNESSEE RIVER VALLEY. A TORNADO WATCH IS IN EFFECT UNTIL 3 AM CDT FOR BENTON…HOUSTON… HUMPREYS…MONTGOMERY…PERRY…AND STEWART COUNTIES. THUNDERSTORMS THAT DEVELOP IN THESE COUNTIES COULD PRODUCE LARGE HAIL…THUNDERSTORM WIND GUSTS TO 70 MPH OR GREATER…NUMEROUS CLOUD TO GROUND LIGHTNING STRIKES…AND ISOLATED TORNADOES.

ANOTHER ROUND OF STORMS…THAT WILL LIKELY CONTAIN DAMAGING WINDS… LARGE HAIL AND ISOLATED TORNADOES WILL MOVE INTO SOUTHWEST MIDDLE TENNESSEE AROUND 8 AM AND MOVE NORTHEAST INTO THE NASHVILLE AREA BY 10 AM. FROM 10 AM ON THROUGH THE AFTERNOON HOURS…SUPERCELL THUNDERSTORMS ARE LIKELY THROUGHOUT MIDDLE TENNESSEE…WITH TORNADOES POSSIBLE.

THIS IS THE STRONGEST STORM SYSTEM TO AFFECT MIDDLE TENNESSEE SO FAR THIS SPRING…AND THE POTENTIAL FOR SEVERE WEATHER LOOKS TO BE INCREASINGLY LIKELY…INCLUDING TORNADIC SUPERCELLS.

So, as stated above, severe weather will be possible ANY TIME during the day, but more likely in the afternoon/early evening. The Storm Prediction Center has not updated their discussion on the event, but I will certainly be checking it in the morning. However, I do not know if I will have the time to make another post. It all depends on the weather, and how soon I leave to go spot this for the NWS.

So all we can do now is wait. Thankfully we shouldn’t be caught by surprise by anything severe tonight while we sleep, but keep your weather radios handy just in case. I honestly have no idea how this is going to pan out, which is why I have tried my best not to hype this post up as much as the others! And so it begins… what the National Weather Service calls, “the strongest storm system to affect Middle Tennessee so far this spring”. Be safe.