Sunday, March 16, 2014

'Snow'ver Achiever

Well, at least in my estimate, this snow is becoming an overachiever. Right now, heavy snow falling here at Valley Station. In fact, secondary roads are becoming overwhelmed by the huge flakes falling at this time. Closing in on 1" here. More later.

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8:30pm
1.5" and it looks like it's finally coming to an end shortly. Not expecting much more but will check in if more accumulates.


MS

Saturday, March 15, 2014

Could This Be Winter's Last Gasp???

Winter's Last Stand???

Well, this is March. Anything can happen. One thing is for sure, most snow amounts do not stick around very long. So, if you get anything, be sure to enjoy it.

However, I'm taking a closer look at the 12z run of the NAM right now. I was not fully convinced of the 06z run, which did nothing but provide confusing data for everyone.

I'll update in a little bit....

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2PM UPDATE
This is not my forecast. However, it is my interpretation of the 12z run of the NAM. I chose this run because this should be the most accurate part of its run based on the time frame.

Based on temperature, 850mb temperature profile, precipitation type, and total precipitation, here are my thoughts.

Most of the precipitation looks to stay along and south of the Ohio River. There is still the potential for a few inches of snow to be realized across parts of central and eastern KY.

However, upper level profiles do not support the data for widespread accumulation amounts. Temperatures at the 850mb level suggest a mix while surface temperatures cool below freezing across much of the state by tomorrow night.

Therefore, expect a mix of rain, sleet, and snow, and possibly some freezing rain. Bowling Green should be all rain; however, they stand the best chance of seeing freezing rain, based on this run of the NAM.

Elsewhere, a mix of precipitation can be expected, especially as we approach nightfall. By midnight Sunday night into Monday morning, a mix of precipitation should be ongoing. If we get all snow, 1-3" can be expected from Louisville to E'town and points east along I-64 and points south to Mount Vernon and Pikeville in eastern KY.  However, a mix looks to negate much of the totals. The higher elevations of eastern KY and the Bluegrass may realize the best chances at accumulating snow.

According to the 12z run of the NAM, Louisville may see very little snow. Lexington could get some accumulation. Ashland, Mavity, and higher elevations near Pikeville and Drift could see modest snow totals.

MS

Monday, March 3, 2014

Winter Storm Update/Summary

Although snow totals were a bit inflated for several locations by the different models, I still believe the amounts I had forecast were not too far off.

My original and only forecast for Louisville was 2-4" accumulation, although I expected that to be mostly snow with minor sleet accumulation factored into that. I picked up 0.3" sleet; therefore, I still had 2.3" snow accumulation on top of that. So, there you go. At my location in Valley Station, 2.6" should be my final tally from this storm. But, I'm still monitoring the last of the snow now in western KY that appears to be shrinking because dry air is working into the mid-levels of the atmosphere.

I'm curious to hear additional totals from the area....

Reviewing my prior posts, I did notice that the 18z run of the NAM on Saturday was the final call I chose from that model. It showed 1-3" for Louisville and between 2-3" for Lexington. However, ice was not as big of a problem here in central and north-central KY. Otherwise, the model did well, according to my interpretation of the model. I could not understand all of the many inflated snow/sleet forecasts many were obtaining from the NAM. I never saw it, unless it was the GFS or a combination of both. I don't know.

I could not find it, but I could have sworn I had another forecast for Louisville and Lexington based on the 18z run of the NAM on Saturday (03/01). It was not on my blog posts. I actually found it on another blog site at kentuckyweathercenter.com. On Saturday, I posted a comment that showed Louisville in a 2-4" range while Lexington was in a 1-3" range.

Later, my favorite short term model, the Rapid Refresh (RAP) consistently showed 2-4" for Louisville while Lexington looking at 2-5". Then, several model runs hinted at a heavy band of snow developing somewhere over central KY. Even the RAP began sniffing it out in later runs (22z run last night). However, much of that did not materialize due to persistent sleet.

At this point, the RAP did not fare as well with this storm system; especially the heavy band of snow (which was probably the sleet it 'saw' in its run) that did not quite meet expectations. However, there's still time to see if the band in western KY moves into central KY and makes up for the lack of snow accumulations. Nevertheless, the RAP was still  pretty much in line with the NAM as the ice did not meet expectations, or perhaps my interpretation and expectation.

I'm still awaiting snow totals from Lexington and Louisville...

Updates soon.

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11:00am
Louisville Int'l (official) received 3.0" preliminary amount snow/sleet total. In line with RAP and NAM
**Lexington came in at 0.4" through midnight; however, a report of 4.6" has been received at the official station since midnight...for a total of 5.0" of snow/sleet. More in line with RAP
Bowling Green has picked up 2.5" since midnight, in line with an earlier forecast I had for them at up to 3". Again, though, bust on the ice, which is always a good thing
From CoCoRaHS and other storm reports, highest totals not much more than 4". Still awaiting on perhaps any 6" amounts. I expected a few of these.
RAP model looks like it finished strong after it faltered overnight for parts of central KY and the Bluegrass, except no 6" amounts to be found yet...update later if necessary.
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5:00pm
Reports of 6" came in from near Lebanon in Marion County. That helped the RAP's case further.
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MS

Sunday, March 2, 2014

Nowcast Mode Winter Storm 'Leo'

***Scroll down to see latest updates***

Leo? Well, think about it. The beginning of March typically has either calm, benign weather (comes in like a lamb, we'll name her Dolly) or stormy (comes in like a lion thus the name 'Leo').

This storm has the potential for being the strongest storm of the season (yes, the entire winter season). Meteorogically, this is the spring season. Therefore, this will be an unusually strong winter storm for our region.

This page will be updated throughout the day. Although, depending on how much precipitation is falling and the p-type, I may choose to update every few hours today.

Reason: Precipitation, even if it's freezing rain, will be fairly light through mid afternoon, according to the RAP model (latest run I looked at was the 08z run which takes through 9pm tonight).

After 4pm, things should start picking up in intensity for some in our region from the I-65 corridor (Louisville to Bowling Green) to the I-75 corridor (Cincinnati to London).

Brief Synopsis for today: 

Rain will be falling at several stations through 3pm. It appears most of this will be fairly light. But, in Louisville, by 12pm, freezing rain will become the dominant p-type as temperatures should be close enough to the freezing mark.

Lexington will follow shortly with freezing rain. Again, amounts appear light ( 0.1" or less) through 3pm.

Bowling Green may stay above freezing through 3pm. It will be close.

By or after 4pm, things will start going downhill. My biggest concern for this time period through 9pm is the Bowling Green area. They will be facing a long-lasting period of freezing rain. For a time, any moderate to heavy freezing rain will preclude any serious ice accretion on power lines and tree branches. However, amounts will be on the rise as we head into the overnight.

For Louisville, light freezing rain (which is an efficient ice accumulator) should be transitioning to a mix of sleet by 4-6pm time frame and continuing for a few hours through 9pm. Snow may begin mixing in by then.

Lexington could have similar amounts today. However, there is a possibility of an enhanced amount of sleet/freezing rain by the 6-8pm time frame. Let's hope it's sleet. Yet, it will not be a prolonged event through 9pm.

I want to see how this synopsis compares to future runs of the RAP. As a side note, I looked at the NAM (0z) run for comparative purposes. For Bowling Green, a prolonged period of freezing rain from 4pm to 1am is possible.

Louisville could see its heaviest snow by 1-3am overnight and Lexington from 3-7am.

As I conclude this part, some may be disappointed by snowfall totals. I'm seeing a lot of enhanced forecast amounts. I will say there is the potential for those amounts to be realized. However, any sleet accumulation will cut down many snow totals. And I do see a good chance for quite a bit of sleet. Nevertheless, amounts of at least 6" in some areas are likely.
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07:30am
Did you know that just as we have a snow to liquid ratio, there is also a sleet to liquid ratio?
Typically, a 3:1 sleet to liquid ratio is common. For every 1" of liquid precipitation, you would have 3" sleet. I do think a few locations could see up to an inch of sleet, or roughly a third of an inch of liquid accumulation.
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07:45am
Radar - A complex of precipitation is streaking eastward across the Ohio and Wabash rivers. Precipitation should reach Louisville by the 10am hour. Presently, it's 33 degrees at my house in Valley Station, southwest of Louisville Int'l airport. By 10am, we should be at the freezing mark. Therefore, freezing rain will be commencing.
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07:55am
Storm Report - Cape Girardeau MO: Heavy thunder sleet is occurring...0.2" sleet
        Carbondale IL: 0.5" sleet accumulation
        Hamilton IL: Thunder with freezing rain and some sleet...0.2" ice accumulation
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08:00am
At this rate, sleet could become the early p-type leader here in Louisville before 4pm? It looks like any moderate freezing rain is already mixing with sleet across MO and IL. Hope the trend continues. Go away ice.
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3:00pm
According to recent run of RAP through 5am, 2.5" snow for Louisville, perhaps more, depending on ratio. Therefore, I'm still sticking to 2-4" for Louisville. However, am concerned about a southward shift of heaviest snow axis. If this trend continues, amounts may need to be lowered.
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6:30pm
Between 4:00 and 5:00 this afternoon, freezing rain and sleet moved into my area. Small glaze on mother-in-law's deck. My wife slipped and bruised her hip. Sleet has accumulated about 0.1".
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8:10pm
22z run of the RAP showing a heavy band of snow developing just south of Louisville stretching to Lexington between 3 and 5am. Going by the model, snowfall amounts of 3-4" for Louisville and at least 5" for Lexington. This is the most aggressive I've seen the RAP since Louisville was forecast to receive 4-6" earlier in the winter season and the RAP nailed it then. Bardstown to Lexington could see 6+" as long as the sleet is done.
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8:45pm
Sleet accumulation of 0.25" here at my house in Valley Station; read report of 0.30" sleet in Okolona. I still think transition to snow between 9 and midnight here in Louisville.
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9:05pm
NWS Louisville thinking about upping snowfall totals for some. Air is cooling quicker than expected. A transition to snow may occur sooner....Of course, this morning the RAP showed a transition to snow by 9-10pm for Louisville. We'll just have to wait and see.
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9:25pm
Some places in Missouri have received up to 2.5" Sleet accumulation. That would almost be 8" snow if it was all snow instead of sleet.
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10:45pm
Snow/sleet in Valley Station - sleet/snow accumulation of 0.4"
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11:40pm
LAST UPDATE tonight...all snow here in Valley Station...total snow/sleet at 0.7"...Still on target to get at least 3-4" but heavier south. Good night and stay safe.


MS


Saturday, March 1, 2014

Nowcast Mode - One Last Look at the NAM

The 18z run of the NAM is as far as I'll take these types of models. I will be switching to nowcast mode after this post. In addition to current observations and radar trends, the Rapid Refresh short-term model will be my model of choice. Quite literally, it will produce an hour by hour look at things like precipitation type, accumulated snowfall in 1-hour increments, preferably, and 850mb temperatures.

First, look at the 18z run of the NAM. Funny thing. If you look at the total snowfall map, you would think omg, it's Snowmageddon. However, I feel quite certain that Bowling Green will not get over a foot of snow from this system.

Why? One look at the 850mb temperature profile shows that when it appears Bowling Green is getting slammed with white-out conditions, the temperatures at this level are forecast to be too warm for snow. However, freezing rain and sleet will be the main precipitation types for the first two 3-hour periods. Snow will finally mix in just before and during the last 3-hour period of their Snowmageddon. Therefore, their 12" snowfall will probably only amount to 3" snow if that. However, I would be more concerned about ice and sleet accumulation for them.

In Lexington, what looks like at least 4" will probably only amount to nearly half that, 2 - 2.4". Again, ice accumulations could become a problem, but not as bad as downstate.

Louisville could be looking at 1-3" snow. Ice accumulations of at least 0.2" with some sleet accumulations of up to 0.5" as well.

This is what I consider to be the most accurate part of the NAM.

However, these types of systems are always hard to forecast. This same model wants to show a heavy band of snow developing somewhere in central KY. Where that sets up, someone is going to get at least a half-foot of snow with ice accumulation underneath.

Nowcast mode next....

MS

Winter's Biggest Punch - No Holds Barred

Winter has won nearly every round this season, with the exception of a brief warmup accompanied by a benign severe weather outbreak not too long ago.

Our region could be in store for another nasty ice storm. The latest NAM run (0z) paints an ominous scenario unfolding for much of the state, as it has for the past several runs.

Just looking at Louisville, the model shows a total precipitation amount of nearly an inch. Some of that will be rain with temperatures above freezing for a little bit. But, it appears that rain will continue to fall while temperatures slip below freezing during the late afternoon and evening and into the overnight before changing to a mix of sleet and snow late.

Ice accumulations could range from -- 0.25" / 0.50"; Snow and sleet accumulation of 1.5 - 3.0 inches by Monday morning.

As a side note, if we get heavy freezing rain, this may actually help reduce the amount of ice accretion on power lines and tree branches as well as roadway surfaces. Hey, it worked out that way for the last ice system we had.

I still would like to consider the next few runs of the NAM. I believe that 30-36 hours out is the most accurate part of the model's forecast. Nevertheless, this will be a challenging forecast for meteorologists as precipitation types will be an issue. So, forecast amounts of each type will naturally be a challenge too.

I will update this page throughout the day.

Winter is not done yet. A flurry of punches to end the season perhaps? Not bad for an Old Man.

MS

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