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Mostly Rain with tail end winter precip (fewer to no travel issues): 50%

ScreenHunter_01 Dec. 17 12.29

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+++++10PM Update+++++

No real changes needed to the forecast…I’ve tweaked the storm type probabilities a bit…

Crippling Ice Storm: 5%

Crippling Snow Storm (Over 6″): 5%

Crippling Ice/Snow combo: 10%

Mostly rain with wintry precip (hazardous conditions): 30%

Mostly Rain with tail end winter precip (fewer to no travel issues): 50%

++++++++++++++++++++++++++++++

Let’s start with the positive, what a great weekend that’s in progress across the region. Aside from a few clouds out there today, and more high clouds heading this way tomorrow, temperatures  for mid December are ideal. Highs today should surge to near 50° and highs tomorrow should be in the 52-57° range. The record high tomorrow is 64° set back in 1939  and tied in 1976. We won’t get there due to a pretty good deck of high clouds that will be streaming into the region around lunchtime but still it will be nice. The winds will be out of the South in the 15-25 MPH in the afternoon so it will be breezy and that will take the edge of the warmth just a little bit. The map on the right side at the top of the blog represents the Winter Storm Watches that are running as I type this.

Our focus will continue to be the storm which is sitting and spinning near southern CA. The new models have carried the same torch that they were last night. The NAM model continues to be the coldest throughout the atmosphere supporting more snowfall, the GFS isn’t as cold, and have more of a wintry mix event for Tuesday with anything from a cold rain to some sleet/frz rain…to eventually some snowflakes. The EURO model from last night was warmer as well supporting less snow. At this point, I think the NAM model is just too cold…it’s also not very comforting to look up into western Canada and see surface temperatures mostly in the 30s and 40s, Granted the colder air is still north of the boundaries of this map…but still.

Here is the storm in question off the coast of CA…

There is a nice looking loop of it here…if you look closely enough, the storm is actually drifting to the west right now…maybe even a bit SWwards…

At this point it really is pointless to get into the specifics…confidence though is increasing that this will be a headache for folks from, at the very least, Amarillo, TX through Dodge City, KS towards the Concordia and Manhattan, KS. area where snowfall amounts in spots may be close to a foot if things work out. That would impact travel along the I-70 corridor towards CO and also the US 50/54 corridors in Central and SW KS…so if nothing else please plan accordingly.

I’ve very confident that the precip will start as plain rain with temperatures well into the 40s on MON PM…there may be a few preliminary lighter showers moving through the region in the AM Monday, but the heavier precip should hold off till later Monday. I’m confident that through midnight early TUE AM, we’re looking at rain for the KC Metro area. The NW MO and NE KS region however will probably be fighting some freezing rain/sleet later Monday night.

From there the issue becomes surface temperatures. The models drive a shallow layer of cold near surface air into the region in the wee hours of TUE. This should start changing the precip over to some sort of frz rain or depending on the thickness of that shallow layer some ice pellet mix. It’s also possible that we alternate through a variety of frozen modes of precipitation into Tuesday based on the GFS ideas.

As far as the frz rain potential goes…a lot of folks get worried at just the mention of ice. Again if temperatures are 30° or above, typically we have few, if any, issues. Once the surface temperatures get down into the 20s then we start to have issues on the roads etc. I’m still struggling to see how things could get that cold here on Tuesday during the daytime hours especially. If W Canada was bone-chilling cold now, that would be a different story, but at this point they aren’t.

The storm will also be entraining dry air into the circulation. This will create a “dry slot” that will also factor into what happens around here. The models can suggest something like this, and they are, but they won’t have accuracy in the placement or timing of something like that happenning, especially from several days away. Another factor to consider is that the storm gets so wrapped up it actually takes warm air to the SE of here and wraps it counter-clockwise around the circulation of the storm. The GFS model is certainly showing strong signals for this happening. This would prevent snowflakes from forming and/or maintaining themselves aloft.

I just glanced at the newest EURO model and it keeps the vast majority of whatever falls as just plain rain…and even keeps the potential for frz rain to at a minimum in the metro. even N MO wouldn’t get that much frozen stuff. The new EURO is about 200-300 miles slower with the storm as well and shows the potential for some wet snowflakes to fall WED AM…probably no accums though. It keeps our temperatures in the 35-40° for the most of the day on Tuesday.

OK so that’s the trends of the modelling. What do I think? my feelings haven’t changed since yesterday’s blog…I continue to feel that the potential for 2-4″ is a worst case scenario concerning snowfall amounts (again NOT a forecast), and in reality the amounts could be much less than that, if we get any accumulation at all. for the KC metro. There is the possibility of some sort of wintry mix, but with temperatures in the 30s, the impact should be pretty minimal. The wild card there will be IF the air nearest the ground gets colder than what I’m thinking right now. Should that change then we could have issues…at this point I think that is a lower chance potential. Here are my probabilities…

Crippling Ice Storm: 5%

Crippling Snow Storm (Over 6″): 10%

Crippling Ice/Snow combo: 10%

Mostly rain with wintry precip (hazardous conditions): 30%

Mostly Rain with tail end winter precip (fewer to no travel issues): 45%

I won’t be overly specific on the news tonight because obviously this is a “fluid” situation. Essentially I’ll be playing the “Be Aware Of This” card and since we’re giving you several days to be aware whatever happens won’t be a surprise. I’ll update those probabilities later tonight should they need updating then again in tomorrow’s late AM blog.

Joe

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