Winter Weather Update-1/27/10

Updates and additional information continue to come in and I have attached the latest graphic products from the National Weather Service. Additional meetings and conference calls are scheduled for various points during the day today and I will provide information updates as necessary and available. Again, winter weather is difficult to track and specifically forecast, however, the consistency in available models and information we receive tends to indicate pretty much what we have been saying, at least at this point. There will likely be some modifications as the event and storm elements draw closer to the state.

Latest from the National Weather Service-

Mild weather will continue today, before a strong cold front and storm system approach from late tonight through early Friday. This storm will produce a mixture of heavy rain, ice, sleet, and snow over Oklahoma and western north Texas. Most of the precipitation will occur Thursday, which will be windy and much colder. Snow is expected in northern Oklahoma. Central and southern Oklahoma are expecting freezing rain and sleet before the snow. The precipitation will end Friday morning while the cold air will persist into Saturday. A warming trend begins on Monday.

Winter Weather Update-EOC/NWS

There is still a great deal of uncertainty among forecasters and computer models as to the exact impact the approaching winter weather event is going to have, but it does appear that virtually all of Oklahoma will in fact be affected. We continue to participate in planning meetings and discussions, conference calls and briefings, and although there are a variety of opinions and observations, the information below appears to be the best representation, at least at this point. Again, please remember that winter weather is difficult to forecast and a variance in storm system or individual storm attribute movement of even just a few miles can significantly change what is actually experienced in any given area.

I have attached three graphic products from the National Weather Service, one depicting anticipated conditions on Wednesday, one for Thursday and a third with current precipitation predictions for the main impact of the event. Additional information from the latest Sperry-Piltz Ice Accumulation Index posting (SPIA Index, an additional tool typically used by electric utilities and other applications to evaluate ice conditions and the resulting impact) indicates that our area may experience significant power outages including main feeder lines and broken tree limbs, etc. Some of these outages, should they occur, may last for several days. Freezing temperatures and strong winds are expected to continue into the weekend, with Sunday potentially being the first day above freezing (barely).

In addition to constant monitoring of weather forecasts and actual conditions, planning should include the consideration of:
1) potential power outages, including what critical aspects of your home or business will be affected (heat, water supply, medical-related power, etc.)
2) cancellation of travel plans, both incoming and outgoing. Should the event occur as currently predicted, all travel will be strongly discouraged.
3) plan for and make accommodations for the elderly, very young, pets and those who need other forms of assistance. Do not wait until adverse weather happens!

Additional meetings, briefings and conference calls are scheduled to continue throughout the upcoming event and I will keep you advised as conditions change or additional information is made available. For now, here is the latest from the National Weather Service-

Dry and mild weather will continue through Wednesday, before a strong cold front and storm system approach. This storm will produce a mixture of heavy rain, ice, sleet, and snow over Oklahoma and western north Texas. Most of the precipitation will occur Thursday, which will be windy and much colder. Snow is expected in northern Oklahoma. Central and southern Oklahoma are expecting freezing rain and sleet before the snow. Precipitation will end Friday morning and the cold air will persist into Saturday. A warming trend begins Sunday.


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Weather Info/Links From Greg Whitworth

I'm short on time to write a forecast discussion since I too was one of the people out getting groceries last night. I want to make you aware of some weather links you can check yourself to get snow forecasts and maps; the same information I look at.

I'm quite concerned about a major event. The ECMWF model has been saying this system will track across slower than projected. The NAM and GFS models are slowly catching onto this and with each version, are increasing the total amount of moisture in the forecast. It's now well over 2" in OKC and in one case, the NAM was dumping out 3" of moisture over OKC. I'm less concerned about the panhandle, I don't think the impacts will be quite as high as what the models have been saying.

This system looks to take a trek very close to the December 24th storm. That means heavy snow in central and southern Oklahoma. Unfortunately, the cold air doesn't look as deep as it did with the December 24th storm, which means there may be some significant icing especially central and southern OK before the change over to snow.

I think the ice will begin around sunrise on Thursday and change to snow near mid-afternoon to sunset in central OK, and sooner in northwest OK. I haven't looked at too many detains for the northwest part of the state, but that's why I'm providing links to the maps so you can look for yourself.

We're talking about a significant, possibly historical event; one that will likely require another disaster declaration for some parts of the state. The models are dumping out over 10" of snow in the main band with anywhere from 1/4 an inch of ice to nearly an inch. They are very persistant with the high totals for the most part. See the maps to know if your area is going to be one of the high impact areas. I will try to write a forecast discussion up sometime this evening.

Here's a timeline chart forecast for Norman, OK produced by a computer at WLNS TV in Lansing, Michigan. It takes all the model information, reprocesses it, and dumps out snow and ice total forecasts. Keep in mind this forecast is ONLY for Norman, OK and the computer does not do any other cities.around here other than Amarillo and Wichita.
It has the date and time in GMT, the wind, Here's what the categories mean:
SfcT = surface temperature
Ptype = preciptation type
SRat = snow ratio, 1 inch of rain equals this many inches of snow (for instance 15 inches of snow to 1 inch of rain)
TotSN = total snow
TotQPF = if you melted the frozen stuff, how much rain it would be (the liquid equivalent of the event)
TotPL = total sleet
TotZR = Total Freezing Rain

http://66.70.209.226/weather/snow/oun.txt


Here's another site I use a lot. Earl Barker's modeling site. It has total snowfall and total ice on a map. The site is somewhat complex, so let me explain what you should look at and give some shortcuts.

http://www.wxcaster.com/models_main.htm

The links like this are the ones you'll want:

NAM Radar Site Snowfall Overlays: NAM Snowfall - fixed 12/08/2009 0630Z
http://wxcaster.com/gis-snow-overlays.htm
Click on the dot on the map.
Total snow from the NAM model for it's versions that come out around 10 pm and 10 am.

GFS Radar Site Snowfall Overlays: GFS Snowfall
http://wxcaster.com/gis-gfs-snow-overlays.htm
Click on the dot on the map.
Total snowfall from the GFS model for it's versions that come out around 10 pm and 10 am.

More regional maps and ice charts:
Region Snowfall: Regional Snowfall
NAM snow (the version that comes out around 10 am and 10 pm):
http://wxcaster4.com/nam/CONUS1_ETA212_SFC_ACCUMSNOWFALL-KUCHERA_84HR.gif
NAM sleet accumulation:
http://wxcaster4.com/nam/CONUS1_NAM212_SFC_ACCUM-SLEET_84HR.gif
NAM freezing rain accumulation:
http://wxcaster4.com/nam/CONUS1_NAM212_SFC_ACCUM-FZRN_84HR.gif

NAM model (the version that comes out around 4 am and 4 pm):
Total snow:
http://wxcaster4.com/nam/CONUS1_MESO-ETA212_SFC_ACCUMSNOWFALL-KUCHERA_84HR.gif

GFS snowfall (10 am and 10 pm version):
http://grib2.com/gfs/CONUS_GFS0P5_SFC_ACCUM-SNOW_84HR.gif
GFS freezing rain:
http://grib2.com/gfs/WINTER_GFS0P5_SFC_ACCUM-FZRN_84HR.gif
GFS sleet:
http://grib2.com/gfs/WINTER_GFS0P5_SFC_ACCUM-SLEET_84HR.gif

GFS snowfall (4 am and 4 pm version):
http://wxcaster4.com/gfs/CONUS2_GFS0P5_SFC_ACCUM-SNOW_84HR.gif
GFS sleet:
http://wxcaster4.com/gfs/CONUS2_GFS0P5_SFC_ACCUM-SLEET_84HR.gif
GFS freezing rain:
http://wxcaster4.com/gfs/CONUS2_GFS0P5_SFC_ACCUM-FZRN_84HR.gif

Greg Whitworth

Potential Winter Weather-EOC and NWS

Despite our best wishes and intentions, it appears that another significant winter weather event may be heading for our area. As mentioned on previous occasions, winter weather is more difficult to accurately forecast, particularly specific attributes in specific areas. That is why you will likely notice some “generalities” in the information provided below. We will continue to monitor the situation and keep you advised as this event moves closer and more accurate information is made available.

Latest from the National Weather Service, potentially affecting all areas of Oklahoma in one form or another-




URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE NORMAN OK

...WINTER STORM WATCH IN EFFECT FROM THURSDAY MORNING THROUGH
LATE THURSDAY NIGHT...

THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A WINTER STORM
WATCH...WHICH IS IN EFFECT FROM THURSDAY MORNING THROUGH LATE
THURSDAY NIGHT.

* AFTER TWO WEEKS OF RELATIVELY MILD WEATHER... A WINTER STORM
WILL TAKE AIM ON THE SOUTHERN PLAINS AROUND THURSDAY. COLD AIR
CURRENTLY IN PLACE OVER CANADA WILL MOVE INTO THE AREA WEDNESDAY
BEHIND A STRONG COLD FRONT. AS THE COLD AIR DEEPENS OVER THE
AREA LATE WEDNESDAY INTO THURSDAY...A STORM SYSTEM WILL
APPROACH FROM THE WEST. A VARIETY OF WINTER WEATHER WILL BE THE
RESULT.


* TIMING: THE MOST LIKELY TIME FOR HAZARDOUS WINTER WEATHER WILL
BE FROM EARLY THURSDAY MORNING THROUGH EARLY FRIDAY MORNING.

* MAIN IMPACTS: FREEZING RAIN MAY BEGIN TO ACCUMULATE ON
POWER LINES AND ELEVATED SURFACES DURING THE DAY THURSDAY. THE
MOST LIKELY AREA FOR SIGNIFICANT ICE ACCUMULATIONS APPEARS TO BE
ACROSS SOUTHERN OKLAHOMA AND PARTS OF WESTERN NORTH TEXAS. SLEET AND
SNOW ACCUMULATIONS APPEAR MORE LIKELY ACROSS CENTRAL AND
NORTHERN OKLAHOMA ALTHOUGH SOME FREEZING RAIN WILL BE POSSIBLE.

* OTHER IMPACTS: GUSTY NORTH AND NORTHEAST WINDS AROUND 25 TO 35
MPH WILL ADD ADDITIONAL STRESS TO POWER LINES THAT HAVE ICE
ACCUMULATIONS. SOME BLOWING AN DRIFTING OF SNOW WILL ALSO BE
POSSIBLE.

* PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.
CONTINUE TO MONITOR THE LATEST FORECASTS.

Wind Chill Advisory

Statement as of 4:52 AM CST on January 07, 2010


... Wind Chill Advisory remains in effect until 6 PM CST Friday...
... Winter Weather Advisory will expire at 5 am CST early this
morning...

* frigid air will continue to plunge southward from the northern
plains as strong northerly winds continue at 25 to 35 mph.

* Timing: the coldest wind chill values are expected Thursday
through Thursday night. The winds will not be as strong on
Friday but dangerously cold wind chill values will still
occur.

* Central Oklahoma can expect wind chills to range from -15 to -5
with 0 to 5 degrees along the Red River valley.

* Impacts: light snow showers and snow flurries will be possible
through the mid morning but no accumulations will occur.
Freezing drizzle last night and early this morning has left some
roads and sidewalks slick and hazardous. Please use caution when
venturing outside.


Precautionary/preparedness actions...

A Wind Chill Advisory means that very cold air and strong winds
will combine to generate low wind chills. This will result in
frost bite and lead to hypothermia if precautions are not taken.
If you must venture outdoors... make sure you wear a hat and
gloves.

Winter Weather Update

In case you haven't heard, it's cold and about to get a lot colder!!

We will experience some of the coldest temperatures we've seen in the last 10-15 years beginning Wednesday and continuing into the weekend. The cold temps will combine with nasty north winds to produce dangerously low wind chills.

The front that will usher in the cold air and strong winds will move through the area Wednesday afternoon. Behind the front, there may be enough moisture to cause some very light freezing drizzle and/or light snow. We don't expect this to be a big problem, but as cold as it's been, it would only take a little freezing drizzle to make roads slick and hazardous Wednesday evening into Thursday morning, so keep that in mind. The bitter cold will persist into Saturday before temperatures moderate and allow us to climb above freezing.

Most locations will see a prolonged period - 18-24 hours or more - of wind chill readings at or below zero, with the colder values further north. This obviously is dangerous for people who are outside for any period of time. We do not anticipate issuing any type of advisory for the light winter precipitation, but there could be some travel issues if it develops. We will definitely be issuing a Wind Chill Advisory either this evening or Wednesday morning. As of right now, the forecast wind chill values are not expected to reach -20 degrees, which is the threshold for a wind chill warning, but we will be close across far northern Oklahoma.

Here are some other links that you might find helpful:

CDC Guide on Extreme Cold Safety - http://www.bt.cdc.gov/disasters/winter/pdf/cold_guide.pdf
WFO Norman Winter Weather Safety Page - http://www.srh.noaa.gov/oun/?n=safety-winter
WFO Norman Wind Chill Information - http://www.srh.noaa.gov/oun/?n=safety-winter-windchill
NWS Wind Chill Page - http://www.nws.noaa.gov/om/windchill/
Protecting your pipes (Plano TX EM Facebook Page) - http://www.facebook.com/note.php?note_id=235104348525

As always, if you have questions, let me know.

Rick
--
Rick Smith
Warning Coordination Meteorologist

National Weather Service - Norman Forecast Office

Weather Situation for This Week/D.Barnes/EOC

Latest from the National Weather Service- anticipated extremely cold temperatures later this week and a 40% chance of freezing precipitation Wednesday night.

NWS - A cold surface high pressure, extending from the upper Midwest into the southern Plains, will maintain cold northerly winds today. Southerly winds will return tonight into Tuesday which will help warm temperatures for Tuesday (mid-30’s for central OK). On Wednesday a strong arctic cold front will arrive. Late week highs will struggle to reach 15 to 25 degrees, while lows could drop below zero degrees by Friday morning. Dangerously low wind chill temperatures and an extended period of sub-freezing weather are likely.

Graphic representations for today (Monday) and Tuesday, Wednesday, and later in the week are attached. We will continue to monitor and provide updates as necessary.

Thanks-

David K. Barnes, Director
Oklahoma County Emergency Management