Dec 29
This evening we take a look at fresh arctic air pouring southeast and click through the various midrange model solutions for the weekend storm system.
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Dec 28
After a cold November, December has been a mild month across the country:
Our headache of a Christmas Eve storm delivered wet weather and this was followed by another wet weather maker (that ended as a wintry mix across central Indiana) yesterday:
Lower 48 Snowpack isn’t impressive considering the time of year:
As we move forward, colder times are ahead to wrap up 2014. Note the latest GFS ensembles showing a one-two punch of cold in the coming couple of weeks. Also note the initially warmer Southeast region- courtesy of that negative PNA. 1st image is Day 1-6, 2nd image is Day 6-11, and the 3rd image is Day 11-16.
The GFS ensembles suggests the cold eventually overwhelms the pattern in the face of a mostly negative PNA that slowly begins to trend positive:
Remember a negative PNA typically would provide a milder southeast this time of year:
The AO, or Arctic Oscillation, has shown a tendency to want to go negative- a cold signal (note the control run off the charts negative):
The European model is suggesting we have a true direct discharge of arctic air in the mid range pattern (left) while the GFS isn’t as bullish on the cold. We’ll likely have to put down a snowpack to achieve the cold the European is suggesting Days 8-10 (below zero). Needless to say, we’ll keep a close eye on things.
The last few days of 2014 will be relatively quiet, and colder than normal. The next storm system of significance awaits for Friday and Saturday. Modeling ranges anywhere from mostly a rain event to more of a significant winter storm. Case in point, let’s just compare the GFS (TOP- milder and less snow) and GFS Upgrade (BOTTOM- colder and more snow). While we can’t show it here, the European model is more of a blend and also delivers accumulating snow. Again, another big fight coming (and you thought you wanted to have this job ;-))?!
In the longer term, the MJO suggests we’re heading back into a milder pattern for mid January as it takes us into Phase 5. Caution though as the MJO forecasts have been erratic as of late, as well. (Click on the images to enlarge if needed).
Bottom line: Our short term confidence is very high on a dry and colder than normal stretch of weather through Day 5. By Day 6 confidence begins to decrease as a wide range of solutions can be argued for and against concerning the storm system next week. We appear set to go into a highly volatile weather pattern through the mid and longer range. Many of our long range teleconnections contradict one another leading to a lower than normal confidence in the longer range.
All of that said, one key ingredient that’s been missing over the past few weeks is arctic air getting involved with the pattern. As stated above, that’s not the case any longer (thanks to this blocking ridge over AK):
Modeling can struggle in handling true arctic air and, as such, wild swings can take place with mid and long range guidance. We caution against this in advance. With so many different signals out there, anticipate a very stormy (not necessarily saying this has to mean snowy) pattern over the next 2-3 weeks.
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Dec 27
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Highlights:
Showers Around…The first round of light rain moved through central Indiana during the early morning hours and has now pushed into extreme eastern portions of the state and into Ohio. While low clouds and areas of fog will remain, we should be dry through a large portion of the late morning into the early afternoon. Showers will then redevelop later this afternoon and tonight as a cold front draws closer. We’re not looking at any sort of heavy rain and temperatures will be mild for this time of year.
Colder Air Pushes In To Close 2014…A cold front will move through the area early Sunday. Cold air may help change light rain to a light wintry mix/ snow flurries before coming to an end Sunday morning. The bigger story will be a much colder air mass that will push south and lead to a cold close to 2014 (fitting, considering the year as a whole has been colder than normal). Unfortunately for snow lovers out there we won’t have any moisture around to lead to snowy times.
Storm System Brews Late Next Week…A significant storm system is on the charts by Friday, but we want to be very clear when we say that the range of model solutions varies from a warmer and mostly wet event to one that’s much colder and primarily a winter storm. Which solution is correct? That’s virtually impossible to say at this point. One could actually argue for and against the wide range of possibilities with some of the pattern developments and teleconnections as of late. Stay tuned.
Upcoming 7-Day Precipitation Forecast:
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Dec 26
I hope this finds you coming off a blessed Christmas spent with family and friends! As you venture out this morning know that several reports of slick spots have come…
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Dec 24
In what’s been an agonizing 6-7 days it’s only fitting that this will come down to the very end. Model performance has been poor, at best, concerning our Christmas Eve storm and given many forecasters a gray hair or two (yours truly included).
We’re going to lay out our best thinking below, but I want to be very clear when I say that we’re in a “now cast” mode for the rest of the day. It’ll be particularly important to have a means of gathering the latest weather information if you have travel plans later today.
Overnight model data shifted the track of a developing surface low east. After looking over all of the available data, we now have converged on a surface low track that moves northeast from west Tennessee into northwest Ohio. The surface low will strengthen as it moves northeast, helping wrap cold air into the system and change rain to a wet snow across central Indiana this afternoon and evening.
The tricky part comes into play when we get into the details. Banding features and associated precipitation rates will be key in determining when local communities see a transition to wet snow and ultimately how much accumulates. This won’t be a “uniform” type accumulation event. Dynamics with this system are impressive, despite only marginally cold air. If we get into a situation where heavier banding develops it won’t take long to cool the entire column of air and result in localized moderate to heavy snow.
On the flip side, surface temperatures are mild after a day yesterday into the middle 50s. Add in the fact stated above of only marginally cold air available and precipitation intensity will be key. If precipitation isn’t heavy enough, it’ll be tough for much snow to fall, yet alone accumulate.
Bottom Line:
As stated above, this is a now cast scenario through the rest of your Christmas Eve. Given all of the data we’ve looked at, this is how we see things playing out this evening:
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