griteater

WPC Model Discussion... PREFERENCE: 12Z ECMWF/UKMET/CMC BLEND CONFIDENCE: AVERAGE THE FIRST SHORTWAVE WEAKENING SOUTHEASTWARD FROM CA/AZ SHOWS GOOD AGREEMENT IN THE MODEL GUIDANCE BUT THERE ARE DIFFERENCES TO TALK ABOUT REGARDING A SHORTWAVE AMPLIFYING SOUTHWARD ACROSS THE CNTRL ROCKIES WED/WED NIGHT. MODEL AND DETERMINISTIC TRENDS HAVE BEEN TOWARD THE WEST/MORE AMPLIFIED WITH THE SHORTWAVE VALID THU EVENING. THE 12Z GFS IS THE WEAKEST AND MOST PROGRESSIVE WITH THE POSITIVELY TILTED TROUGH AXIS STRETCHING FROM THE MS VALLEY INTO NRN MEXICO FRI MORNING. GIVEN THE ENSEMBLE TRENDS TOWARD A SLOWER/DEEPER TROUGH AXIS...AWAY FROM THE 12Z GFS AND 00/06/12Z GEFS...DO NOT WANT TO BE ON THE FASTER EDGE OF THE MODELS. THE 12Z UKMET REPRESENTS THE MOST AMPLIFIED SIDE OF THE LATEST DETERMINISTIC MODEL SPREAD BUT IT HAS WEAKENED SOME FROM ITS 00Z CYCLE. FOR FRIDAY...THE 12Z ECMWF TRENDED SLIGHTLY WEST WITH THE NRN PORTION OF THE TROUGH AXIS AND FASTER/EAST WITH THE SRN PORTION OVER SOUTH TEXAS. THE PREVIOUSLY PREFERRED 00Z ECMWF MEAN IS CURRENTLY NEAR A BLEND OF THE 12Z ECMWF/UKMET/CMC. WHICH IS BETWEEN THE PREVIOUSLY MORE AGGRESSIVE DIGGING SEEN IN THE 00Z UKMET/ECMWF AND FLATTER/MORE PROGRESSIVE 12Z NAM/GFS.

In cases like this where the only warm layer is right at the surface, this is what I've used/observed in the past... If surface wet-bulb temperature is... 32: Snow 33-34: Snow or Rain/Snow Mix 35: Rain/Snow mix 36-37: Rain or Rain/Snow mix

IMO, this is going to continue to tick more amped with more precip inland. I'm just basing it on how it's trending with the wave/trough and sfc low positioning, and how these tend to work with the modeling. I think we would have seen it back off with the 12z runs if we were moving to a weaker solution. Looks good to me in the mtns. East of there it will take some heavy temperature analysis to determine locales with snow.

It's banging on the heavy rates scouring out the low level warmth. Tough forecast.

Euro looks like a light snow event for the mtns and foothills..into far NE GA...storm is slow to depart...some snow mixed in east of there probably

Euro is a little farther inland with precip....and a little warmer

Early 12z UKMet looks similar to GFS & CMC...detailed maps later

After the sounding comes up, there is a dropdown at the top center of the page for Hr - so you can change the forecast hour there. At top right, there's a dropdown for map where you can view the map and choose another location for the next sounding

GFS out to 81...overall it's slightly more precip / slightly warmer

GFS out to 69, it looks like it's going to take a baby step toward more precip

GFS out to 57 - it's bending the heights back to the SW more this run so it should be a little slower with the storm....but it may have trouble sharpening the base of the trough

No way the GFS will come in way amped, but maybe it takes a baby step

You can just click on the map on pivotal weather and get the soundings as the maps come out. Same with the College of Dupage models, but for some reason I was having trouble with the NAM soundings. Tropical Tidbits has it too, but not for the NAM (no idea why) http://www.pivotalweather.com/model.php?m=nam&p=refcmp_ptype&rh=2017120506&fh=78&r=conus&dpdt=

As others have mentioned, the upper jet structure is good here (right entrance region of jet over the northeast)...that should allow for precip to expand back to the west. Models are notorious for being too skimpy on the NW side of Miller A's....should see the precip expand back to the NW with that kind of jet structure

The NAM looks too amped at the base of the trough, but I like a toned down version of this...but with precip getting back into E Tennessee

It's kind of how I've been envisioning this system, but we'll see what the other models say when they come in

NAM = que the Fred Sanford holding the heart pic

Outside of the mountains, quicker is not the trend we want to see from a temperature standpoint

UKMet looks a little faster and slightly less amped to me compared to last run...hard to tell on the precip...detailed maps come out later.

CMC looks a little quicker with the storm this run...has some light snow in north GA to upstate to parts of central, then western NC....not a lot of precip thrown back west into the cold air

Some light snows before precip ends from Raleigh north to Chesapeake

Need to see what the UKMet says for trend clues

Looking like GFS is going to be an eastern scraper again

GFS out to 69 - just minor differences, but it looks a whole like the prior run to this point