Holston_River_Rambler

Almost looks like there is a little leeside low forming in upstate SC

A live look out my window:

Ended up with about 1.5" total so far.

Much vaunted late February sun angle has done exactly 0 to melt anything except on the roads.

Here's how that looks on the HRRR, (using COD site since the blues are bluer there)

Yeah, I was just looking at the HRRR and RAP and it almost looks like this system us getting some higher (more elevated)-than-usual moisture trapped on our side of the Apps and some orographic lift is able to take advantage of that in areas that usually don't do well with the typical upslope.

Looks like MRX finally filled in the WWAs over the southern valley. Looks like they pulled the trigger at around 5:30 am.

Pretty cold cloud tops over east TN with some back building over Mississippi and western AL: That big upper low is just over the Dakotas is just pushing it all through a little too fast.

1/2" here.

oooo we have a mesoscale disco: Mesoscale Discussion 0116 NWS Storm Prediction Center Norman OK 0601 PM CST Tue Feb 18 2025 Areas affected...Northeastern Arkansas...Southeastern Missouri...Western Tennessee...Western Kentucky...Southern Illinois Concerning...Heavy snow Valid 190001Z - 190300Z SUMMARY...Snowfall rates will gradually increase across portions of western Kentucky and western Tennessee through the evening. Rates will decrease through time, though some moderate to heavy snowfall rates up to 1"/hr will be possible in heavier bands. DISCUSSION...Radar analysis shows the gradual shift of snowfall into portions of western Kentucky and Tennessee this evening. Moderate to heavy snowfall is ongoing across southeastern Missouri into southern Illinois, where a persistent heavy band extends, driven by 700-850 mb frontogenesis and isentropic ascent. This enhancement will gradually shift eastward through time, with potential for a few heavier bands with occasional 1"/hr rates. HREF ensemble guidance shows a down trend in rates overall through the evening, with a transition to mostly light snow for portions of western Tennessee. Confidence is highest in potential for better rates across northwestern Kentucky into southern Illinois. ..Thornton.. 02/19/2025

Saw a lightning strike and some convective clouds as the sun was setting upstream:

A few satellite and radar obs. for now: Looks to me like convection parallel to the Gulf coast thingy is happening. Note the feature over SE/ South central Texas. Looks like a front focusing the precip. there and south of the LA coast. Also evident on Long wave IR band: No clue what this feature is in west TN (maybe lower/ mid level moisture/ WAA impacting higher cloud temps somehow?) but it looks cool on IR imagery. Dry air trying to overcome near Memphis: Deep Gulf connection seems shut off for now, so we wait and see what the actual shortwave does as it moves east. Still looks near TX/ NM border to me

Pretty good radar echoes SW of Memphis right now but you can also see the virga halo around the radar site.

Rhea county has a Cold weather advisory now!

Sun angle is much lower with JKL’s latitude.

Weatherbell is down for me, so probably not much from me until either that comes back up or SREFs finish around 230 pm.

Nice fantasy storm on the 12 GFS around hr 300. It's even got the '24-'25 winter Baja lowTM trying to interact with the N. stream. surely nothing will change in 300 hours?

@PowellVolz yeah wrt speed, some of the models have it out of my area by 10 am or so. I would definitely take an earlier onset tonight.

Pretty good precip field, virga or otherwise, already:

Looks like MRX went with the NBM for that map:

Virga introduced, in case any of us had hope of earlier onset Some dry low level air will keep any precip light at onset, until forcing increases toward sunrise and precip rates increase. The timing of this will greatly affect snow accumulation amounts. A later arrival time will decrease the chance of accumulating snow, because rising temperatures during the day will become a stronger limiting factor. Once the sun comes up, snow accumulation during the daytime is difficult in the later parts of winter with the higher sun angle.

Sorry that only has East TN but it’s from a station based out of Columbia, SC

Here is the latest GRAF animation and yeah @PowellVolz I think this is the one

WBIR in house model showing snow starting at my location around 11pm tomorrow night. Wish I knew which model that was.

Key parts of their rationale for accums: If this precipitation moves in earlier in the morning we`ll likely see more accumulating snow before sunrise, but if it holds off even just a couple of hours and doesn`t start to precipitate in the southern Appalachians until after sunrise, then chances for accumulating snow really decreases. Once the sun comes up and starts to impact the cloud layer history indicates that snow occurring during the daytime, in the later parts of winter with the higher sun angle, and when temperatures are around or just above freezing... It can lead to much slower snow accumulations. In addition there could possibly be some downsloping flow which warms up the atmosphere and eats into the QPF totals. With temperatures expected to slowly climb through the day to above freezing for most of the Valley locations any precipitation that lasts into the afternoon hours will have a decent chance of flipping over to cold rain, which would also help wash away some of the snow that might have accumulated earlier in the day. At this time the most likely scenario is to see advisory level snowfall for much of the Valley locations, with the lowest amounts in the south and along the foothills of the Appalachians. We could see 4+ inches in the higher elevations of the northern Cumberland Plateau and over into far southwest Virginia on Wednesday as they`ll have the snow begin the earliest and the coldest temperatures throughout the day.