Action 3 News Weather Blog

Our weather has been very active so far this winter to say the least. The latest storm will pass just to the south of the area tonight and Friday. If you are planning to travel in that direction stay tuned to the weather forecast for a lot of snow and ice across the Central and Southern Plains into the Midwest. For us it has been a very quiet week and that will continue into the weekend. Our biggest concern is the cold temperaures the next few days but nothing like we saw a couple of weeks ago. Our next chance of snow will arrive Monday but looks to be a quick shot with minor accumulations.

Hello all,

Just a quick update on our weather and the forecast into the weekend. We are actually in a bit of a break from an active weather pattern across the country. There has been severe weather in the Ohio River Valley today and already Winter Storm Watches are posted across the Dakotas for the next storm. Here across the metro we need to look out for more fog and slick spots tonight into Friday Morning. Our next storm system is still forecast to move in late Friday into Saturday. This time around the track will be farther north and brings us breezy conditions and rain to start the weekend. In fact, high temps will be in the 30s Friday and in the 40s Saturday. We will see some snow out of this system Saturday Night through Sunday Night but the worst of the snow will remain north.

Good Morning, Everyone!

Depending on where you live… you either didn’t see anything of issue or a full-blown ice storm.  The range between the two may be as little as 50 miles.  The surface temperatures since rain started to fall late yesterday evening determined the severity of the freezing rain event.  As of 10 am, the reports of ice accumulations from the National Weather Service I have is as follows:

Audubon, IA – 0.5″

Oakland, IA – 0.4″

Harlan, IA – 0.3″

Onawa, IA – 0.25″

Little Sioux, IA – 0.25″

The immediate Omaha metro seems to have experienced icing confined mainly to untreated side streets, parking lots and sidewalks.  The Omaha icing appears to have been localized since overnight low temperatures (eyeballing the overnight surface observations out of Millard, Offutt and C.B.) bottomed out at 32°/33° which would’ve been MUCH worse if temps fell into the upper 20s as I originally forecast.

The worst of the icing occurred north and east of Omaha where temperatures fell into the upper 20s overnight.  You can see a loop of the surface weather observations (temperatures are in red) between 10 pm and 10 am CST here:

http://www.rap.ucar.edu/weather/surface/displaySfc.php?region=dsm&endDate=20100120&endTime=16&duration=12

Here are liquid equivalent (or rainfall) reports from 6 am Tuesday through 6 am Wednesday CST, from the National Weather Service:

It appears that the heaviest of the precipitation occurred over much of central and western Iowa with precipitation totals of at least 0.50″!  Keep in mind that the time range of the image included precipitation that occurred before the freezing rain began yesterday evening.

For the remainder of the day today, look for some leftover patchy drizzle and patchy freezing drizzle.  Overnight, watch for some patchy black ice as low temperatures will fall into the middle/upper 20s in the Omaha metro, so any puddles of water that occurred as a result of the rain and snowmelt from the ice event will become frozen.

Looking ahead…our next round of precipitation will occur over the weekend.  We’ll see mostly rain from late Friday night through Saturday, but there is a possibility of a rain/snow mix or just snow on Sunday.  The 1200 UTC GFS shows a track of the surface low still taking the potential heavy snow well to our north across the Upper Midwest.  We’ll refine our forecast for the weekend tomorrow and Friday, but this weekend system appears to not be a big snow event for our neck of the woods.

Have a great rest of your day and take it easy with the patches of ice out there!

-C.T.

CT gave very good detail with the sounding and the type of situation we are in. Not much has changed and the going forecast still looks good. Just a quick update on the advisories and warnings from this evening. Omaha is now under a freezing rain advisory with an ice storm warning just to our north and east. Temperatures will slip just under the freezing mark tonight and back up to 32 on Wednesday. Watch for slick spots to develop on exposed surfaces and untreated surfaces especially later tonight into tomorrow morning. The worst of the weather looks to be north and east of Omaha during this time where temperatures will be a few degrees cooler.

Ryan

Hi everyone!

Ryan, Liz and I have been looking at a potential for freezing rain since late last week for tomorrow.  Well…tomorrow is upon us!  In a situation like this, the first thing I do is look at a forecast sounding.  For those unfamiliar with what a sounding is, it’s simply a vertical temperature and wind profile of the atmosphere.  It can be created from a simple weather balloon launch, but also can be created from computer forecast model data. Meteorologists can interpret lots of information from a sounding.  Click on the image below to see the Wednesday 6 am forecast sounding for Omaha from the 1200 UTC Eta, courtesy Northern Illinois University:

Not trying to get into a lot of detail on this image, but the higher up on this image you go, the higher you climb in the sky.  The sounding warms as you go farther right and cools as you go farther left.  The white, curvy vertical lines represent the temperature (on the right of the two) and dew point (on the left of the two).  If they’re close together or overlap especially in the bottom half of the image, this simply means the lower and mid-atmosphere is full of moisture sufficient for clouds and precipitation.  One more thing I should point out, is the freezing line, which is 0°C on the bottom axis (marked in blue).  You can see the 0°C isotherm (freezing line) going diagonally toward the upper right the higher you go.

As a forecaster, I pay close attention to where the temperature and dew point lies above or below the 0°C isotherm in the lowest third of this image…when forecasting wintry weather.  In reality, if temperatures are well above freezing, let’s say 3,000 or 4,000 feet above the ground, but you have a very cold airmass at the surface well below freezing…any rain precipitating from the cloud won’t have enough time to freeze before it reaches the ground.  Effectively, the hypothetical rain will hit the ground as water, but will freeze upon contact since the surface is below freezing.  This, by definition, is freezing rain.  It’s just the traditional rain that we get during the warm season, but in the wintertime, this causes a glaze of ice on everything.  This is the setup we’re looking at for our area tonight into Wednesday.

As far as amounts, the 1200 UTC model guidance (MOS) shows QPF codes of 3+2 from the NAM and 2+2 from the GFS models between 6 pm this evening and 6 pm Wednesday for Omaha (Eppley Airfield).  Translated into actual value ranges, the NAM shows a potential liquid equivalent of 0.35″-0.73″ and the GFS shows a range of 0.20″-0.48″.  Therefore, the minimum liquid equivalent from this storm is 0.20″ based on the GFS for Omaha and since surface temperatures are expected to generally remain at or below freezing through the event, there’s a good chance that the 0.20″ could be ice accumulation.  For your reference, please see the latest MOS for Omaha (Eppley) here: http://www.nws.noaa.gov/cgi-bin/mos/getall.pl?sta=KOMA

The Action 3 News viewing area is currently under a WINTER STORM WATCH from midnight tonight through 6 pm Wednesday.  It’s very likely that the shift and lead forecasters at the Omaha/Valley National Weather Service office will consider upgrading to a Freezing Rain Advisory (if potential ice event accumulations will be less than 1/4″) or an Ice Storm Warning (if ice accumulations are expected to exceed 1/4″).  Since other types of precipitation (such as snow or sleet) won’t be likely tonight and tomorrow, I have a good feeling that it will be either one of the two advisories I mentioned that are being strongly considered for our area.

I’ll simply be restating my thoughts on Action 3 News Live Midday, but you can also see what Ryan’s thoughts are on Action 3 News Live tonight at 5, 6 and 10.

In a nutshell, just plan on an ice storm affecting much of our area, including the Omaha metro beginning tonight, lasting through early Wednesday afternoon.

-C.T.