January 16-18th Rain-Sleet-Snow Chances

[snowdog]

The last big one to hit Nashville, 2003 I think, daytime temps were in the mid to upper 20's. 

Usually when you have mid 30's and a low riding south it sends up too much warm air and you do not get the snow till the backside when there is usually very little moisture left to work with. 

[Thundersnow]

We can get heavy, wet, slushy snows with temps in the 30s.  Of course, in that case, the roads usually stay wet and clear for the most part, even if it manages to accumulate on the trees and grassy areas. 

And, of course, if it's above freezing, the snow won't stay around for very long.

For good sledding snow, the ground needs to be frozen.


The January 16, 2003 snow fell with temperatures mainly in the upper 20s.  Here are recorded hourly observations that day during the height of the storm:

9:00 AM 28.4 °F / -2.0 °C  17.6 °F / -8.0 °C  64% 30.09 in / 1018.8 hPa  0.5 miles / 0.8 kilometers  Calm Calm -  0.00 in / 0.0 cm  Snow  Snow
9:06 AM 28.4 °F / -2.0 °C  26.6 °F / -3.0 °C  93% 30.09 in / 1018.8 hPa  0.2 miles / 0.4 kilometers  Variable 4.6 mph / 7.4 km/h / 2.1 m/s  -  0.00 in / 0.0 cm  Fog , Snow  Snow
9:10 AM 26.6 °F / -3.0 °C  26.6 °F / -3.0 °C  100% 30.08 in / 1018.5 hPa  0.2 miles / 0.4 kilometers  South 3.5 mph / 5.6 km/h / 1.5 m/s  -  0.00 in / 0.0 cm  Snow  Heavy Snow
9:26 AM 26.6 °F / -3.0 °C  26.6 °F / -3.0 °C  100% 30.07 in / 1018.2 hPa  0.2 miles / 0.4 kilometers  ESE 4.6 mph / 7.4 km/h / 2.1 m/s  -  0.03 in / 0.1 cm  Snow  Heavy Snow
9:39 AM 26.6 °F / -3.0 °C  26.6 °F / -3.0 °C  100% 30.05 in / 1017.5 hPa  0.2 miles / 0.4 kilometers  East 6.9 mph / 11.1 km/h / 3.1 m/s  -  0.05 in / 0.1 cm  Snow  Heavy Snow
9:53 AM 28.0 °F / -2.2 °C  28.0 °F / -2.2 °C  100% 30.06 in / 1017.8 hPa  0.2 miles / 0.4 kilometers  East 6.9 mph / 11.1 km/h / 3.1 m/s  -  0.08 in / 0.2 cm  Snow  Heavy Snow
10:05 AM 28.4 °F / -2.0 °C  28.4 °F / -2.0 °C  100% 30.03 in / 1016.8 hPa  0.2 miles / 0.4 kilometers  East 9.2 mph / 14.8 km/h / 4.1 m/s  -  0.03 in / 0.1 cm  Snow  Heavy Snow
10:40 AM 28.4 °F / -2.0 °C  28.4 °F / -2.0 °C  100% 30.00 in / 1015.8 hPa  0.2 miles / 0.4 kilometers  East 8.1 mph / 13.0 km/h / 3.6 m/s  -  0.09 in / 0.2 cm  Snow  Heavy Snow
10:53 AM 28.9 °F / -1.7 °C  28.9 °F / -1.7 °C  100% 30.01 in / 1016.3 hPa  0.5 miles / 0.8 kilometers  East 5.8 mph / 9.3 km/h / 2.6 m/s  -  0.11 in / 0.3 cm  Snow  Snow
11:02 AM 28.4 °F / -2.0 °C  28.4 °F / -2.0 °C  100% 29.99 in / 1015.5 hPa  0.2 miles / 0.4 kilometers  ESE 5.8 mph / 9.3 km/h / 2.6 m/s  -  0.01 in / 0.0 cm  Snow  Heavy Snow
11:24 AM 28.4 °F / -2.0 °C  28.4 °F / -2.0 °C  100% 29.96 in / 1014.4 hPa  0.2 miles / 0.4 kilometers  ESE 9.2 mph / 14.8 km/h / 4.1 m/s  -  0.04 in / 0.1 cm  Snow  Heavy Snow
11:41 AM 28.4 °F / -2.0 °C  28.4 °F / -2.0 °C  100% 29.95 in / 1014.1 hPa  0.2 miles / 0.4 kilometers  ESE 5.8 mph / 9.3 km/h / 2.6 m/s  -  0.07 in / 0.2 cm  Snow  Heavy Snow
11:53 AM 30.0 °F / -1.1 °C  30.0 °F / -1.1 °C  100% 29.96 in / 1014.3 hPa  0.2 miles / 0.4 kilometers  ESE 5.8 mph / 9.3 km/h / 2.6 m/s  -  0.08 in / 0.2 cm  Snow  Heavy Snow
12:53 PM 30.0 °F / -1.1 °C  30.0 °F / -1.1 °C  100% 29.92 in / 1013.0 hPa  0.2 miles / 0.4 kilometers  SSE 3.5 mph / 5.6 km/h / 1.5 m/s  -  0.04 in / 0.1 cm  Snow  Heavy Snow

Source: http://www.wunderground.com/history/airport/KBNA/2003/1/16/DailyHistory.html?req_city=NA&req_state=NA&req_statename=NA

[Woodvegas]

1/13 12z GFS gives me about an 1 inch of snow Wednesday night then possibly a rain/snow mix (would be another inch if all snow) during the day Thursday. As usual temps appear to be marginal and the exact track of the low will be critical. There could be a lot of changes between now and then.

Then the GFS unleases the Artic hounds and the GFS text output does not have me getting above freezing for 11 straight days (19th through 29th) with a low of 9F Saturday night.

Note: I averaged MBT (Murfreesboro) and RNC (McMinnville) to get my output.

[jmundie]

The January 03 storm had high temps in the low 30s. The morning temps started just a few degrees above freezing.

Like I said, the best snow events we get here, temps are usually close to freezing. When we get heavy precip in the drier air, evaporational cooling occurs.

Need I remind anyone of last Feb, when it was bone chilling cold nearly the entire month, and we managed a two 1-1.5 inch snows?

Or how about the storm in 2004 which gave us no snow because the air was too dry, while areas that started above freezing to our south (columbia, namely) got almost 9 inches.

The most important factor in getting snow in nashville is a low pressure system that strengthens just as it passes to the south of Nashville, so it starts as heavy wet snow, possibly not accumulating at first, then the heavy precip cools the air and holds temps just below freezing.

[Thundersnow]

Afternoon AFD out of Memphis...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
245 PM CST SUN JAN 13 2008

.DISCUSSION...

COLD AND DRY HIGH PRESSURE CONTINUES TO BUILD INTO THE MIDSOUTH
THIS AFTERNOON. A LOW LEVEL STRATUS DECK CONTINUES TO HANG TOUGH
OVER WEST TENNESSEE AND WILL BE SLOW TO CLEAR FROM WEST TO EAST
TONIGHT. HIGH PRESSURE WILL REMAIN OVER THE AREA INTO MONDAY AND
BE REINFORCED BY CANADIAN HIGH PRESSURE AS A NORTHERN STREAM
SHORTWAVE DIGS ACROSS THE OHIO VALLEY. THIS WILL KEEP COOL AND DRY
CONDITIONS OVER THE AREA THROUGH WEDNESDAY MORNING.

ON WEDNESDAY...AN UPPER LEVEL LOW PRESSURE SYSTEM OVER NORTHERN
MEXICO WILL LIFT OUT TO THE NORTHEAST IN THE SOUTHERN STREAM ALOFT
AS SURFACE LOW PRESSURE DEVELOPS OVER THE WESTERN GULF OF MEXICO
AND MOVES NORTHEAST. AT THE SAME TIME...A NORTHERN STREAM
SHORTWAVE WILL DIVE SOUTHEAST ACROSS THE NORTHERN AND CENTRAL
PLAINS STATES. IT APPEARS AT THIS TIME THAT THE TWO UPPER FEATURES
WILL REMAIN UNPHASED AND BOTH THE 12Z GFS AND ECMWF NOW AGREE ON
THIS. REGARDLESS...LIGHT PRECIPITATION SHOULD OVERSPREAD THE
REGION WEDNESDAY AFTERNOON AND CONTINUE INTO THURSDAY. AT THIS
TIME...IT APPEARS THAT THE AIRMASS WILL BE COLD ENOUGH OVER AT
LEAST THE NORTHERN HALF OF THE AREA TO SUPPORT SOME WINTER WEATHER
POTENTIAL. THE GOOD NEWS IS THAT MODELS CONTINUE TO SUPPORT LIGHT
PRECIPITATION...THE BAD NEWS IS THAT IT USUALLY ONLY TAKES A SMALL
AMOUNT OF WINTER WEATHER ACROSS THE MIDSOUTH TO CREATE TRAVEL
PROBLEMS. THIS SCENARIO WILL CONTINUE TO BE UPDATED BY LATER
FORECAST SHIFTS.

[Thundersnow]

The January 03 storm had high temps in the low 30s. The morning temps started just a few degrees above freezing.

The 24-hour high on that date in Nashville was 32.  So, it doesn't appear it was ever above freezing in the morning or any other time of the day... at least at the airport.  Looking at the hourly updates, it appears the high of 32 occurred at 2:00 in the afternoon, which was after most of the snow had ended.  During the heaviest snow, the temperatures ranged from 26 to 30.

Like I said, the best snow events we get here, temps are usually close to freezing. When we get heavy precip in the drier air, evaporational cooling occurs.

Need I remind anyone of last Feb, when it was bone chilling cold nearly the entire month, and we managed a two 1-1.5 inch snows?

Or how about the storm in 2004 which gave us no snow because the air was too dry, while areas that started above freezing to our south (columbia, namely) got almost 9 inches.

The most important factor in getting snow in nashville is a low pressure system that strengthens just as it passes to the south of Nashville, so it starts as heavy wet snow, possibly not accumulating at first, then the heavy precip cools the air and holds temps just below freezing.

What you're really referring to is a suppressed storm track... which is often the case with an Arctic airmass.  So, you're right in the sense that usually when a cold air mass is in place, the air is too dry, and it's hard to get a healthy storm system close enough to give us the business. 

But, that's not to say that temperatures below 30 prevent us from getting snow.  Again, remember that the high temperature in Nashville on the date of the blizzard of '88 (if we can call that a blizzard... hey, 8-10 inches area wide is a blizzard by TN standards) was 23 degrees... that was the high temperature.  So, in that case, we were getting a major snowstorm with temperatures in the low 20s.

So, the air temperature whether it be 23, 28, 32, or 34... it doesn't tell the full story.  There are many factors to consider.  But, I would much rather see a snowstorm at 23 degrees than I would at 33 degrees. 

But, it takes a very unique set of circumstances for us to get a major snowstorm in Middle TN anyway you cut it... especially over the last two decades, it seems.

[Thundersnow]

Nashville AFD:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
341 PM CST SUN JAN 13 2008

.SHORT TERM (MON-WED)...
COLD FRONT WL MOVE EAST OF THE PLATEAU THIS AFTERNOON. ECHOES EAST
OF INTERSTATE 65 PRODUCING ISOLATED SHOWERS OR BRIEF SLEET IN A
FEW CASES. COLDER AIR AND MOISTURE MAY PRODUCE SOME BRIEF LIGHT
SLEET OR FLURRIES NEAR THE KENTUCKY BORDER THIS EVENING.

SFC HIGH PRES IN THE SOUTHERN PLAINS WL NUDGE EAST INTO THE LWR
MS VLY TONIGHT. PRES GRAD WL KEEP ATM MIXED TONIGHT WITH MOS BLEND
OF TEMPS. COLD MON BUT WITH MORE SUN. DRY AIR AND LESS WINDS MON
AND TUE NIGHT SO COLDER. SFC HIGH PRES MOVES INTO THE APPS WED
AND DRY CONDITIONS WL CONTINUE.

.LONG TERM (THU-SUN)...
BUILDING MOISTURE CONTINUES TO BE A CONCERN WITH LOW PRES IN THE
WESTERN GULF. ALL MODELS TRACK SFC LOW WELL SOUTH OF MID TN WED
NIGHT-THU. ALTHOUGH TEMPS LOOK TO MODERATE WED EXPECTATIONS ARE
FOR RAIN/SNOW EVENT WED NIGHT FM OVERRUNNING MOISTURE AT THIS
POINT.

SNOW SHOWER CHANCE WITH SYS THU-FRI WITH WRAP AROUND MOISTURE IN
COLDER AIR. DOES NOT APPEAR TO BE A MAJOR SYS. BUT COULD REQUIRE
WINTER WX ADVISORIES LATER IN THE WEEK. ARCTIC FRONT WL BRING
COLDER AIR INTO THE MID STATE NEXT WEEKEND.

[Nashville_wx]

Another PISS POOR AFD from KBNA. I need to write a letter to them.

[jmundie]

The 24-hour high on that date in Nashville was 32.  So, it doesn't appear it was ever above freezing in the morning or any other time of the day... at least at the airport.  Looking at the hourly updates, it appears the high of 32 occurred at 2:00 in the afternoon, which was after most of the snow had ended.  During the heaviest snow, the temperatures ranged from 26 to 30.

What you're really referring to is a suppressed storm track... which is often the case with an Arctic airmass.  So, you're right in the sense that usually when a cold air mass is in place, the air is too dry, and it's hard to get a healthy storm system close enough to give us the business. 

But, that's not to say that temperatures below 30 prevent us from getting snow.  Again, remember that the high temperature in Nashville on the date of the blizzard of '88 (if we can call that a blizzard... hey, 8-10 inches area wide is a blizzard by TN standards) was 23 degrees... that was the high temperature.  So, in that case, we were getting a major snowstorm with temperatures in the low 20s.

So, the air temperature whether it be 23, 28, 32, or 34... it doesn't tell the full story.  There are many factors to consider.  But, I would much rather see a snowstorm at 23 degrees than I would at 33 degrees. 

But, it takes a very unique set of circumstances for us to get a major snowstorm in Middle TN anyway you cut it... especially over the last two decades, it seems.

You're right, all I'm saying is, the colder it is, its harder to get significant precip in here that isn't mostly virga. The only convective snowstorm I ever got growing up in Memphis was 1985, and I was a couple months old, so obviously I don't remember what the surface map looked like. And I wasn't here in Nashville in 88, so don't have that storm to reference.

But I remember several times in Memphis waking up to what was supposed to be a huge overrunning event, which massively underperformed due to the air being so dry. It seems like maybe most of our large overrunning events occur when the low has a positive tilt, and precip has trouble overcoming dry air. The lows that go negative before they reach us tend to pump large amounts of heavy precip in, but with them comes warmer air (at least aloft, if not at all levels).

I still say our best track for big snows is gonna be marginal tempwise until the low passes to our east, pulling in more cold air. We just don't get many of those.

I'm not feeling quite as bad though, since its looking more and more like the Northeast is gonna get screwed with this system. If they can't get snow, then there's really no reason why we should get any.

[Snowman]

I agree, sometimes the BNA (OHX) discussions are very short and not very detailed. Of course its far out and things will change so I understand them not wanting to put alot of effort into it.

[jmundie]

18z is screwing us again. The entire precip shield is headed towards NC. Is that positive tilt? We need it go go negative and pull down some cold air, cause we have no high pressure to keep temps down. Our only chance of seeing accumulating snow is having the heaviest moisture come in at night.

[Nashville_wx]

Good things come to those who wait. We all know the Gfs has a SE bias, let the nw tend come into effect. Another 3-4 models run we should have a good idea of where the L is gona track. I will bet it comes NW.

[jmundie]

Yeah, but we just got burned with this last storm. The gulf storm never materialized. We get a clipper out of no where that is supposed to transfer energy to the coast any minute now.

Every day I become more and more convinced that no one knows what's going to happen more than a day an advance.

[Thundersnow]

Yeah, but we just got burned with this last storm. The gulf storm never materialized.

What storm are you referring to?

While the system this week doesn't look particularly huge at this point, I think it's the best chance we've seen so far this winter.  There have been storms in model fantasy land for one to two weeks away... but, those situations have very low confidence and should be taken with a grain of salt anyway.

We're now actually 3-4 days from a potential... which is really the best we've done so far, other than the "flizzard" on New Year's Day.   

[Snowman]

I agree with Nashvillewx. Let the northwest trend work.