Monday, March 25, 2013

Weather Summary Today 03/25/2013

Well, temps have stayed above freezing for the most part in Louisville. Accumulations were a little lighter than I expected here. Still, these off and on snow showers could put down some quick accumulations. However, temperatures will remain above freezing coupled with daylight hours inhibiting any roadway issues.

There were some hefty accumulations north of Louisville. Some totals include 10.5" in Muncie IN and 8.4" in Castleton in Marion county.

As of today, 48.7% of U.S. has snow cover. Remember last year about this time? The warmest March on record? Only 7.7% of U.S. was covered on this date.

Baton Rouge LA could be experiencing freezing temperatures the next couple of mornings, coming close to record lows.

Quite a bit of wind damage in Florida. Winds gusted to 86 mph in Orange county, not far from Orlando.

Here in Kentucky, Wayne county near Monticello reported roofs blown off storage building while concreted post was yanked out of the ground. Also, in Pulaski county, a large metal building was leveled. In Corbin, a roof was torn from a trailer and several trees down.

Mt Washington NH, home of the world's worst weather, has recorded about 280" snow since September. Their 109 mph wind gust yesterday was not the highest gust of the 2013 year. A 129 mph gust occurred last month. At one time, Mt Washington held the world's highest wind gust at 231 mph.

It's going to be close. Louisville still looks to break into the top ten coldest March months ever. Right now, the average is 40.4 degrees. The tenth place average is 40.0. Average temperatures in the 30's will be offset by warmer readings later this week.

Earlier this month, the Hydrometeorological Prediction Center (HPC) has been renamed the Weather Prediction Center (WPC).

Also, the Storm Prediction Center is updating its web page, starting March 28.

The Climate Prediction Center has a nice new tool, complementing its 8-14 day outlook. Check it out here. For Louisville, during the April 1-7 time frame, it shows a 46% chance for below normal temperatures, 21% chance for above normal temperatures, and a 33% chance for near normal temperatures. Pretty cool.


Sunday, March 24, 2013

Complicated Forecast

So much for attempting a forecast yesterday. There was and still is too much uncertainty with this storm system.

A slight southward shift has occurred with the models albeit not enough to bring the heaviest snow into our area. However, the Louisville NWS and local television mets will probably be yanking a few hairs from their scalp before this one is over.

The track of the low is still the most important part to watch. Yet, other significant variables are vying for closer inspection.

Surface-based instability - a fetch of -2 to -4 readings keep showing up in the forecast just south and southeast of Louisville. That could be a fair indication of convection that leads to thunderstorm activity.

CAPE Values - this is also an indication of convective activity that may flare up today in those same areas south of Louisville; values around 250, not bad for no atmospheric heating.

The above factors do not appear to have much influence on the snow that will be falling well north. Many areas today in the Louisville CWA will be seeing rain or a mix of rain/sleet/snow the farther north one goes.

However, as sunset approaches, temperatures in the upper levels will begin transitioning any liquid precipitation to frozen precipitation.

Right now, it looks like the transition to all snow in Louisville will not be till after 8pm tonight. HRRR models are indicating possible snow accumulations as close as the northern part of Louisville CWA by 5pm.

Core of cold air with low pressure - ahead of the low, warmer air will be in place. As the low moves overhead and just east, colder air will quickly change from rain to a mix to all snow though temperatures will be well above freezing. If the snowfall rates are heavy enough, accumulations will occur especially on grassy surfaces.

Just north of Louisville, surface temperatures will be cooling rapidly. Accumulations will be affecting travel before midnight.

I still think a slug of heavy wet snow will affect the Louisville area sometime between 11pm and 4am. Although roadways should generally stay wet, as we continue to cool and the snowfall rates are heavy enough, we could start to see slushy roadways just before morning rush.

This is nowcast mode. My current thinking is that Louisville could get 0.7 to 1.5 inches of wet snow by rush hour tomorrow. After that, convective snow showers could put down another inch in places during the daylight and evening hours. But roadways should be in better shape after rush hour and during the daylight hours.


Friday, March 22, 2013

Winter Storm Advisories/Watches

Update: 2:28pm edt
Just in...I didn't see that, just moments ago while I was writing my thoughts below, Indianapolis NWS has issued a Winter Storm Watch for much of their CWA, including Seymour, Bloomington, and Indianapolis. Accumulations of 5-9" expected along and north of Bloomington and 3-6" south of that line.

Winter Storm Watches and Advisories looking more likely for Indianapolis, Seymour, and Dayton. Cincinnati could still get in on some accumulation.

NAM puts deformation band in Indiana. Could be a southward retraction in the NAM's runs. My forecast comes out late tonight/tomorrow morning.


Analog Time: Accumulating Snow for Some

An early February-type system will be approaching our region later this weekend and promises to bring snow to parts of the region.

I've had some success looking at analogs for possible storm scenarios. One that caught my attention this time is from February 6, 2010.

I like the moisture placement for the most part. Granted, these analogs do not mean the exact weather that happened then will happen again in these places.

However, it does show the storm's potential and most likely locations to be impacted.

Remember, this is not a forecast. This is just a look back in time at a weather system that has similar features to the one that will be impacting the region later this weekend.

The February 6, 2010 event put down less than 1" here in Louisville. However, just to the north at Indy and Cincinnati, they had amounts around 6". There were some isolated heavier amounts exceeding 8" around the Cincinnati area.

I'll be looking at the NAM as my trusted source within 36 hours of the main event. Meanwhile, I thought I'd share that little bit of snow history with you looking at analogs.

Some places primarily north of Louisville could be looking at the potential for 4-8". Not bad at all by mid-January standards if you ask me. And this is March???


Tuesday, March 19, 2013

Top Ten Coldest March???

What a difference a year makes. Last year, Louisville recorded its warmest March ever at an average of 59.6 degrees (70.5 / 48.6).

This year, as of the 18th, the average temperature has been 41.2 degrees (49.5 / 33.0). At this time, we still do not qualify for top ten status for coldest March ever. The tenth place average is 40.0 degrees.

However, looking at medium-range forecasts, there is a likely chance we will continue to see below-average temperatures for the rest of the month.

In fact, based on those forecasts, I'm already projecting a finish in the bottom half of the top ten list. For that to happen, our average temperature would have to be in a range of 39.0 and 40.0 degrees, or 6th through 10th place.

I think this is a conservative projection. In other words, we could be looking at a colder scenario, which could vault us as high as 3rd place (38.5 degree average).

For the record, pun intended, the first and second coldest March ever were 1960's 32.5 average and 1947's 37.1 average.


Monday, March 18, 2013

Weather for Second Half of March

Talk about March Madness and I don't mean basketball.

I woke up to my windows vibrating and my dog's paws skittering across the hardwood floors attempting to hide from the sound of thunder this morning. That didn't work. A few more tremendous rumbles found him in his hiding place as well.

On Saturday we exceeded 70 degrees in Louisville. On Sunday, a short trip outside of the city's limits, 3 inches of snow accumulated for a time. This morning, it was 37 at my house with thunder, wind, and heavy rain.

What a way to begin the second half of March.

The weather professionals are promising temperatures well into the 50's today. That's actually down from the lower 60's. Looking at recent observations, though, just before the 10:00am time frame, I'm seeing the warmer air getting pinched off, sliding eastward across the southern and southeastern parts of our viewing area. I would be surprised if we see over 50 degrees today here in Louisville.

Speaking of 50 degrees, I looked at a recent chart of high temperatures here. Here's what I found....

Temps >= 50 degrees (number of days during the month)

January - 10
February - 12
March - 7 (through the 17th)

Technically, we're over half way through the month. If we don't reach 50 today, don't look for it again for the rest of the week. Can you imagine March being cooler than February (which was below normal cool as well)?

I hate to bring up the past. But did you know that at this time last year, we reached 82 degrees? That would begin a 5-day stretch of temperatures in the 80's! And this was after we had already recorded 80 degrees or better for a couple of days earlier in the month.

Looking ahead, here's what the CPC is saying for the rest of the month....

>70 percent chance that temps will be below normal for the March 23-27 time frame.
>50 percent chance that temps will be below normal for the March 25-31 time frame.

Most locations will have equal chances for slightly above or slightly below normal precipitation.


Tuesday, March 5, 2013

Snow Accumulations Likely Tonight Mar 5-6 2013

Update: 4:40pm
Temperature down to 37. That's a 3 degree drop in 15 minutes. Large flakes have begun falling here in Valley Station.

Update: 4:25pm
Front has pushed through Valley Station during the last few minutes. Gusty winds will increase along with a heavier rain band. Temps have dropped 6 degrees in the last hour from 46 to 40 here in Valley Station sw of Louisville. Snow is getting closer.

Update: 2:55pm
Forgot to update the front. Temps are crashing out west, low to mid 30's. Winds are gusting 30-35 mph as close as Breckinridge and Grayson counties.

In Nowcast mode, we can still access short-term models such as the HRRR or High Resolution Rapid Refresh for a look at possible accumulations. I'll be posting updates as to whether this storm may overachieve or fizzle out for the region.

Temperatures will be key. As long as surface temperatures are close to the freezing mark, main roads should be slushy to wet. However, I've seen main roads that I travel become snow covered quickly.

Banding of snow will be another key. Where heavier and persistent bands set up, expect robust accumulations.

In general, 2-4" is forecast for the region from Louisville to Lexington. I like that forecast. Some 5-6" amounts are possible in these areas.

The 1400z run of the HRRR at 15 hours out or midnight tonight has Louisville to Cincinnati in a 1-2" range by then. The snow is expected to continue at least till daybreak.

The 1600z run at 15 hours out or about 2:00am still has Louisville closer to 1" while 1-3" surrounds Louisville by then.

Updates later...


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