Holston_River_Rambler

12z EPS MSLPs: 12z EPS 850s: 12z EPS qpf: 12z EPS snow mean: 12z EPS ice: H5 trend with the Baja low:

Hurricane hunters dropsondes planned:

Could be wrong, but I suspect the GFS is going to bring it out in two waves on this run

Did anyone see the NAM give east TN an appetizer Friday am? Had to zoom out to get the 1055 high in, lol

hot dawg, a non zero probability

Overnight WPC probabilities: Pertinent parts of the overnight WPC disco: Model guidance generally remains in good agreement with the large scale pattern. All model guidance shows arctic air making it down to the Gulf and East Coasts, which will clash with southern stream energy to produce a high impact winter storm across the southern tier. However, some model differences still exist with the details of both the southern and northern stream energy. These details will impact things such as the timing, snow/ice line, and the northern gradient of the snowfall. While these details will need to be worked out over the coming days, it seems almost certain that a significant winter storm will occur. The 12z/18z GFS runs from yesterday were extreme outliers with a much slower and even cutoff southern stream energy near CA. The 00z GFS has since come into better agreement with the other models, but given it appears to just be catching on to things, we still prefer to only give it a little weight in this forecast. Otherwise taking a blend of the ECMWF/CMC/UKMET, the ECENS/GEFS and the AI model suite, seemingly results in a pretty good middle ground forecast at this point and is reflected in the WPC QPF forecast. On the southern side of this system significant freezing rain is expected, likely resulting in dangerous travel conditions and power outages. Given the arctic airmass in place, temperatures will likely only be in the teens and 20s where freezing rain is occurring, which will only act to increase travel impacts. The exact swath of ice will a bit uncertain until we get closer to the event...but currently the highest probabilities stretch from portions of central TX into the lower MS Valley and into portions of SC/NC. To the north of this icing threat will be a swath of significant snowfall stretching from OK into the TN Valley and Mid-Atlantic. Again, we will need to fine tune the northern and southern gradients of this snow, and also the exact magnitudes...but a rather wide swath of significant snowfall is likely. Temperatures in the teens and 20s will increase travel impacts from this snow and also result in snow ratios likely higher than climatology. This should result in higher snowfall totals than applying a simple 10-1 ratio to QPF would give you...especially on the northern half of the snowfall axis.

Kuchera:

6z Euro is a tick south from 0z, still some mixing issues for southern valley though

6z Euro surface pressure trend: If we just end up with that little lp blob over the Snokies turning into a leeside low......

6z normal Euro still dropping a 1054 hp south and it is a tick further south than 0z

6z continues its tick south:

6z AIFS ha a pretty good look:

Euro AIFS is running, let's see what it does.

GFS automatically gets a processing upgrade when it shows 30" + of snow in any given Tennessee location. In all seriousness though.........

WPC extended Disco: Model guidance is in pretty good agreement on the upper level pattern through the period, especially over the central and eastern U.S. under the broad upper trough. All model guidance shows Arctic air making it down to the Gulf and East Coasts, which will clash with southern stream energy to produce a potentially high impact winter storm across the southern tier. There are some southern stream differences among the models that may affect sensible weather. The 06Z and 12Z GFS solutions were the only deterministic solutions still hanging on to a slower upper low lingering near Baja California into next week, while other guidance (including AI) has trended much more progressive with this feature. For this reason, the WPC forecast favored a faster solution with very limited influence from the GFS. A faster solution allows for increased moisture across the south-central U.S. ahead of the upper low with a broader precipitation footprint. There is still a significant amount of uncertainty in the QPF forecast this weekend. Models have been trending northwards with the heavy precipitation axis, which is in line with what the AI guidance has been showing, so adjustments were made to the NBM to reflect these trends in the WPC forecast. The WPC forecast used a blend of the ECMWF/GFS/CMC/UKMET early in the period, then increased contributions from ensemble means through the second half of the period while decreasing the influence of the GFS.

New WPC graphic: from this site: https://www.wpc.ncep.noaa.gov/threats/threats.php

Maybe this overpowering northern stream will finally do us a favor and keep heights suppressed in front just enough to ward off as much ice as possible

Euro:

Some pivotal satellite for data collection over the pole will probably get knocked out, lol.

Anything even remotely like a Miller A/B hybrid triggers me lol.

It looks like it ticked south a smidge, but it reeaaaalllly wants to get the big hp out in front of the system and then have the LP attack it.

Neither one have started yet on pivotal:

I guess the AIFS doesn't always start at 15 minutes after the hours 6 and 12.