Joe’s Weather Blog: What a week of weather ahead (SUN-2/18)

This week is going to be fascinating on many fronts…numerous precipitation chances (for a change)…temperatures that will be varied from point A to point B…even has close to us as the KC Metro area…the potential of some thunder and lightning…the chance of ice. not once but twice, and hopefully some needed rains…and that last aspect is what I hope turns out to be the given in this…although depending on where you live as usual your results will vary. There are many questions about the exact play-out of Monday (temperatures) and Tuesday (temperatures>ice) and Wednesday night (more ice?).



Forecast:

Tonight: Windy and mild with temperatures initially dropping a few degrees then going up. We may be near 60° at daybreak Monday. Also some mist/drizzle is possible later tonight into Monday morning. Winds may continue to gust to 30-40 MPH overnight as well. The low cloud deck/surge should arrive around 8-11PM from south to north

Monday: Cloudy and windy. There will be some light and fast moving showers that may occur at any time. We should warm up a few degrees to about 65°. Then a cold front will start moving through the Metro but it will be crawling through. Temperatures on the north side from I-70 north may drop from the 60s to near 40° sometime in the afternoon, while the south side remains in the mild air mass for several more hours. With this set-up some showers are possible at any time.

Monday night: This actually may be the key time frame to what happens on Tuesday regarding the ice set-up. How far south will the cold air push then stall? Will there be a retreat of the cold air? Temperatures may vary widely by daybreak Tuesday from near 32° on the north side to near 55° on the southside IF the cold air retreats. IF not, most of the metro is closer to 35°. There should be some mist/light rain in the region as well.

Tuesday: Conundrum day. It won’t snow…that’s the only thing I’ll promise right now. Too warm above us for flakes to form. Temperatures may be varied through the area from the 30s to the 60s at daybreak. North of the front there will be rain and freezing rain developing. South of the front there may be enough instability to create some thunderstorms. Near the front is the question and where that front sets up will determine who has icing (north) and who remains liquid (south). That front may end up VERY close or in the KC Metro area.



Discussion: (again scroll to the bottom of this IF you don’t want to see all the model talk)

Changes from yesterday’s thoughts…

Frontal location…some model data has it wavering in the KC Metro area itself on Monday night and Tuesday morning. This would be extremely unusual to have a front come through…stall…retreat north and then come through again all in the course of 18 hours or so. The reason: A weak area of low pressure forms along the almost stalled front Monday night. This turns the surface winds back towards the south as the low comes up the front…then returns the winds towards the north after the low pressure area passes sometime near daybreak Tuesday. IF that low is farther south…indicating that the front Monday night pushed farther south…then we stay in the COLD air…near 32° (or colder air) and that means what falls is mostly freezing rain on Tuesday.

IF the model depictions though are right…then we see temperatures flipping and flopping. The cold air comes in Monday afternoon/night…stalls on the southside (let’s say Paola) and stalls on the east side (lets say Odessa, MO). Then as a weak area of low pressure (remember…counter-clockwise flow) comes up along the nearly stalled or slightly retreating north front. Then sends I-70 areas back into the 50s early Tuesday morning…while north of I-70…towards KCI…the cold air hangs tough…so whatever falls would be liquid from KC south and potentially icy near and north of KCI.

Let me try to illustrate this to you…

Things are reasonable at Noon Monday…with the sharp cold front cutting into areas on the north side…heads up for areas north of that front at noon…MUCH COLDER than KC!

Here is the EURO forecast for temperatures…

Now the hi-res NAM model….

Now let’s move ahead 6 hours…to 6PM.

Euro…

Hi res NAM…

subtle differences in frontal location for JACO, Miami Co and Cass Co…it’s a big deal because the temperatures will be 25° different either side of the front.

Then at 6AM Tuesday…look what happens…and perhaps the key to icing…

Euro forecast…note the changes IN the KC Metro area…

Now my concern…the hi res NAM model…see the differences? We’re talking a 15 mile southward displacement

Why is that important…because winds above this boundary will be cranking out of the SSW at close to 45-55 MPH before shifting away as the morning goes along…that should get a decent amount of rain to form…and that rain would be falling into the cold air at the surface for a good part of the KC metro…look what happens by 9AM Tuesday…on the hi-res NAM.

We also end up with close to 1/2″ rain from 6AM-6PM…those temperatures as you can see would probably support freezing rain.

Now there is a big difference around these parts when it comes to ice accumulations affecting roads. During the DAY…IF the temperatures are 29-32° we typically don’t have a lot of problems…and it appears the vast majority of whatever happens (if we get ice) will be mostly during the day. Ice will accumulate on exposed surfaces, trees and decks etc. When the temperature though is below 28°…all bets are off

Typically the general rule is that the NAM model does better in the handling of colder and shallow air masses. I say shallow because this air mass coming in will only be about 1000-3000 feet thick as it moves through the KC area…if that thick…it’s shallow! Above that level the temperature will be closer to 55° several thousand feet off the ground. This is more complicating because it’s not as IF we get hourly reports on the thickness of the cold air…so it will be even tougher to track…

Then there is the complication of what raindrops are up there…are “warm”…does this “warm” rain chew away at the near 32° air at the surface…and allow the surface air to increase a degree or so (that’s all that’s needed really).

The bottom line is IF the temperature falls into the 20s Monday night…it’s a sign that the cold air mass may have a better push south…that would mean a colder set-up for Tuesday and hence more ice.

The potential continues for 1/10>1/3rd” of ice accumulation if the colder air mass is the winner here and northwards.

Also I looked harder into the Wednesday night and Thursday morning event…that would be ice and or sleet not snow I think. The air at about 5,000 feet to near to above 32°

So let’s wrap this up…

  1. Varied temperatures within KC Metro area Monday afternoon. 20-30° variation from southside to northside by 3PM or so.
  2. Critical push of cold air…and it’s stopping point Monday night will determine the significant ice potential on Tuesday
  3. I’m still concerned about 1/10-1/3rd inch ice accums in the KC Metro area…perhaps with a leaning location for areas N/W of the I-35 corridor region?
  4. The ice would end after 3PM Tuesday…assuming we’re cold enough.
  5. IF we’re in the 29-32° range during the day Tuesday…roads may not be terrible. Exposed surfaces will have more accumulation. IF 28° or colder…more impacts.
  6. Anecdotally to me at least…it seems all these cold air masses this winter have been colder than what the models have dictated during the initial push. It seems to me that in most cases, even the short range models have struggled to keep up with the degree of coldness during the 1st 6 hours of the cold air surge.
  7. It’s been 120 days since out last 1/2″+ precipitation event in one calendar day…going back to 10/21…that’s an amazing run. We may get close to that this time…
  8. Some may hear thunder with all this happening
  9. This forecast will change…I’m telling you now. The end play of ice…may be very varied from the south to the north within the KC metro area. areas south may have little impact…areas north may have more impact. KC will fluctuate in between. (3PM Update) As a matter of fact the PM NAM models (hi-res/regular) are now both colder and farther south with the front…meaning that there is no retreat of warm air northwards…and a better chance of being colder and icier on Tuesday.
  10. I need 10 minutes of air time to talk about the next 2-3 days of weather…and even then I’d probably go over my allotted time

More Monday

Our feature photo comes from Tracey Schell-Sunderhuse from Linn Valley, KS. There were some stunning sunrise shots this morning…

Joe

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4 comments

  • nwallen56

    Hi Joe. With what you know about the ice potential (and I fully realize this may change drastically), how do you think KCI will be affected? I have a flight departing at 6:30 Tuesday morning and I’m wondering the likelihood that it will take off on time (if at all). I promise I won’t hold you to anything you say in reply.

    • Joe Lauria

      It may be delayed a bit by deicing I guess but with the flight so early…odds are it will be here Monday night and waiting for you to get there. That drive though could be a bit slick depending on the temps. JL

  • Patrick Trudel (@sedsinkc)

    Thank you so much for the in-depth model discussion. Very educational and fully illustrates what a tough forecast you have. It’s beyond my rudimentary amateur forecasting skills. However, just as analog, it seems to me the scenario where the front comes thru then retreats a few hours later only to return soon again seems most unlikely. That almost never happens, in my experience. So I would favor the colder scenario just from experience.