As stated yesterday, snow in December is extremely hard to come by as climatology argues against it. The upper level jet streams are in a position of flux as the Polar High strengthens in advance of the oncoming winter and the Subtropical High retreats. In this type of scenario, we don’t usually get that nice shot of arctic air from the north. Take a look at this picture…
Notice in the “winter” illustration, the colder air is more expansive and in the “summer” illustration, the warmer air is more expansive. Concerning this weekend’s system, there’s not enough cold air coming in behind the surface low pressure, despite a near-perfect storm track.
What’s the bottom line, you ask? We can expect some rain late Friday into Saturday. Some of the rain early Saturday *could* mix in with some wet snow and *could* end as some light snow Saturday evening, which shouldn’t amount to anything. Climatology wins again, and yes, I’m a sore loser.
Greetings, from the cloud capital of the world…Murfreesboro, TN. A stretch? Yeah it is, but here lately it seems as if the only weather worth mentioning is the cloud cover. Don’t worry though…
The weather community has been watching a storm system progged to exit the northern Gulf of Mexico for a few days now. You snowbirds in Tennessee know that any snow-making weather system worth its weight in road salt exits the Gulf and heads northeast towards the southern Applachians, as this storm system is progged to do. But we have a problem…
Most – if not all – of the medium and long range model data used for making a forecast are carrying different solutions. The GFS, affectionately called the GooFuS across weather circles, hints at a more northerly route for the storm system while the other major model, the ECWMF – European – model spit out a fantastically winterized solution yesterday. Average depths on the clown maps were nearly 8″.
Right on cue, today’s European model, more specifically the afternoon run, was much tamer in regards to a possible solution. It gave us a moderately snowy solution with 2-4″ accumulations throughout the area. Granted, that number sounds much more reasonable but several system factors are still considerably different across most model platforms, so the above referenced model solution, again, probably will not happen.
However, not all is lost. There are still similarities among some of the more important factors when it comes to Tennessee snowfall and we’re going to see which model suite picks the correct solution. Climatology argues against measurable December snowfall, but it has happened. The current stagnated pattern we’re in looks to make a wholesale change after Christmas and as the immortal Jim Ross mentioned above, business will DEFINITELY pick up after the first of the year.
Just concluded a conference call with the NWS concerning our impending storm event. Here’s the highlights:
– Squall line currently just E of Little Rock, AR. Progress has been more rapid than previous model data has indicated, but it’s expected to slow down the closer it gets. Current ETA for us is between 7p and 1a.
– All modes of severe weather are possible: hail, damaging winds, and tornadoes.
– This will also be a heavy rain event, with most folks seeing an additional 1-3″ of rain. Some could conceivably see 4″ of rain after its all said and done with.
– The discrete supercell chance, while not zero, is small. NWS more concerned with the flooding potential than a discrete supercell outbreak.
– Like to remind everyone that this will in all likelihood be a nocturnal event and would like to emphasize the importance to be aware of what’s going on around you. It will be dark, and given the amount of wind shear energy that will be present, some nocturnal tornadoes are expected.
– A Flash Flood Watch goes into effect at 7p tonight, lasting through 1p Tuesday afternoon. I do expect this watch to get upgraded to warnings for some counties across the midstate later on tonight.
– Keep up to date with your favorite local media outlets for changing weather conditions.
Here’s a brief outlook at this weekend’s forecast. Several of you have asked about the MTSU game on Saturday, and I’ve also fielded questions about the soccer tournament at Siegal Park. The answer to both questions can be given with one word…wet. But, HOW wet is it going to be. No way to know for sure and short-range data isn’t helping.
Here’s a shot of the NAM Hi-Res simulated radar reflectivity, valid for 7pm Saturday night…
Notice how there’s virtually no rain anywhere close to our area. Next up, is the 12z NAM composite reflectivity, valid for 7pm Saturday…
Notice anything different? Yeah, me too….a shed-ton of rain. Last, but not least, is the medium-range 12z GFS 700mb relative humidity, valid for 7pm Saturday…
While not wholly indicative of rain, it does indicate a lot of moisture in the air around 7pm. Unfortunately, this will have to be a wait-and-see kind of game as it pertains to this weekend’s rain chances. Model data isn’t conclusive at all and some folks might not even see a drop. However, most of us will at the very least see SOME rain falling during our respective sport-spectating activities Saturday night. I’ll be at the game Saturday, but my seat will be high and dry inside the Tower. Just be weather-aware and come prepared with appropriate raingear.
We’ll start off the discussion with the latest mesoscale update from NWS Nashville:
“.MESOSCALE UPDATE… RAIN COOLED AIR HAS MOVED ACROSS A GOOD PART OF WESTERN MIDDLE TENNESSEE THIS MORNING DELAYING SEVERE STORM THREAT FOR SEVERAL HOURS IN THIS AREA. SOUTHERN AND SOUTHEASTERN MIDDLE TENNESSEE…CLOSER TO THE ALABAMA BORDER HAS WARMED NICELY THROUGH THE MORNING BEING SOUTH OF THE COLD POOL WITH TEMPERATURES IN THE MIDDLE 70S. 850 MBAR JET ON THE ORDER OF 50-60 KNOTS HAS REMAINED INSITU LAST SEVERAL HOURS FROM CENTRAL MISSISSIPPI NORTHEASTWARD THROUGH MIDDLE TENNESSEE. AIR MASS ACROSS SOUTHERN MIDDLE TENNESSEE WILL CONTINUE TO DESTABILIZE OVER THE NEXT FEW HOURS SO WILL NEED TO KEEP REALLY CLOSE TABS ON THIS AREA FOR THE POTENTIAL FOR MORE DISCRETE AND RAPID DEVELOPMENT IN THE FORM OF SUPERCELLS. THIS MAY TAKE A COUPLE OF HOURS SINCE CAP WILL HAVE TO BE BROKEN. AS WE GET INTO THE AFTERNOON HOURS EXPECT TO SEE ACTIVITY PICK UP BACK TO OUR WEST CLOSER TO THE TENNESSEE RIVER AND TAKE ON MORE OF A LINEAR OR SQUALL LINE APPEARANCE WESTERN MIDDLE TENNESSEE DOWN INTO NORTHEAST MISSISSIPPI. IN ADDITION A FLOOD THREAT EXIST FOR ALL OF MIDDLE TENNESSEE THROUGH 11 PM TONIGHT. THREE TO FOUR INCH RAINFALL AMOUNTS HAVE ALREADY FALLEN ALONG AND 40 MILES SOUTH OF INTERSTATE 40 FROM FAIRVIEW TO THE TENNESSEE RIVER.”
Highlights from the conference call…
– This event has the opportunity to be locally significant.
– There has been flash flooding to our west across Williamson, Maury, and Lewis counties. That is expected to continue throughout the day as we expect up to 2-4 additional inches of rain.
– All modes of severe weather are possible
– The greatest chance of severe weather will be situated across areas south of I-40, as this is where the greatest tornado chance will be. Significant and long-track tornadoes are possible this afternoon/evening.
– Perhaps the greatest question most of the weather geeks have is what will the rain this morning do to our atmsophere? Quite typically, this situation serves as a scrubber or a cleanser and “cleanses” our atmosphere. However, this is not the case this time. The rain has produced what meteorologists call a “thermal moisture boundary”. Essentially it is a cold pool that serves as a highway of sorts for supercell thunderstorms. Often they latch on this boundary and strengthen explosively. Right now, this boundary exists along the Bedford/Rutherford Co line, and back west through Maury Co. NWS Nashville will be watching this area CLOSELY once storms begin firing back to the southwest. For example, the Mayflower, AR tornado was a result of a storm interacting with this type of boundary. The atmosphere was a lot more conducive for strong tornadoes across S Arkansas, but this tornado formed across N sections of the state.
– Best chance for severe weather across the area will be late afternoon into the early evening.
– Continue to spread the word about the storm chances for today. Emphasis on “Don’t be scared…be prepared.”.
More info as it becomes available.
Several have asked about what does a good, short-term disaster kit contain. Thinking this could go well over 140 characters, I’ll list them here on the blog. This isn’t an all-inclusive list and your kit will obviously have things that are more important to you than they would be to others, but this is a good start. This “kit” can be kept in a plastic tub near your safe place, or even in your safe place if you’re so inclined.
#1 – Several bottles of water
#2 – Several cans of non-perishable food (w/manual can opener)
#3 – Multiple flashlights w/several changes of batteries
#4 – Well-stocked first aid kit
#5 – A whistle or noisemaker used to call for help
#6 – Battery-operated radio/TV you can use to keep up-to-date with whats going on around you
#7 – Those with children should include powdered formula and extra clothes
#8 – Extra cash and travelers checks
#9 – Several days worth of prescription medication, extra pair of glasses, or other health aids
Again, this list is not inclusive and should be considered for short-term only. A long-term disaster kit will obviously contain much more than this, such as a mess kit (paper plates, cups, spoons, etc), plastic bags, and personal sanitation items. Chances are you won’t need to utilize this short-term kit, but it’s always a good practice to be prepared.
Just concluded a conference call with the NWS. Here’s the highlights:
– This system is slow-moving and will send numerous lobes of upper-lvel energy our way.
– There will be multiple rounds of severe weather between Sunday afternoon and early Wednesday morning, which means severe storms during the day AND at night a possibility.
– At this juncture, it’s difficult to nail down specifics, but it appears as though all modes of severe weather (straightline winds, hail, tornadoes) will be possible.
– Along with the storm threat, there is a flash flooding threat, as well. We can expect 1.5-3″ (maybe even 4-5″, if the Weather Prediction Center were to be believed) before the system departs.
– We don’t want to overhype the details (or potential) of this system because they’re highly fluid and dependent upon how the storms develop and evolve. Sundays storm evolution will affect Mondays storms…Mondays storms will affect Tuesdays, etc.
More info as it becomes available.