Weather Update 1-29-10 0925

Although additional amounts of freezing drizzle and light snow were recorded overnight, we have not experienced the magnitude of icing as originally predicted for our area. Road crews continued clearing and treatments throughout the night, however as additional bands of freezing precipitation passed through the area early this morning, additional accumulations on roadways and exposed surfaces were experienced. Snow continues to fall throughout the area with anticipated accumulations of up to three inches predicted.

State-wide road conditions reports indicate “slick and hazardous” through all but southeastern Oklahoma. Travel is discouraged throughout our area. Reports of power outages are becoming more prevalent, including in some specific areas of the metro, however no wide-spread outages in the metro right now. Larger outages are reported in southwestern, southern and now southeastern portions of the state. We are not receiving significant reports of downed tree limbs in the metro as of yet, however, as the precipitation continues to fall, particularly if wind speeds increase, additional outages, falling lines, broken poles and tree limbs will compound the problems and potential for outages. Attached graphics from the National Weather Service depict a storm update and predictions for today.

From the National Weather Service –

Light snow will continue across northern and western Oklahoma early this morning. While western, southwestern Oklahoma and north Texas will see areas of freezing drizzle and freezing rain. A transition to snow across central and southwestern Oklahoma and western north Texas with 1 to 3 inches of snow possible. Travel is discouraged and even walking outdoors can be hazardous due to slick and ice covered surfaces and the potential for falling tree limbs. Precipitiatioin is expected to end and winds diminish later this afternoon and evening. Temperatures wil remain cold through Sunday.

Winter Weather Update 1-28-10 1630

Power outages in western and southwestern Oklahoma are still significant as tree limbs and heavily weighted power lines an poles continue to be problematic. Outages are occurring in our area, although typically smaller and of shorter duration.

Although precipitation is still falling, there is some good news in two areas. One, we are moving more toward receiving sleet as opposed to freezing rain. Secondly, for some odd reason the “back edge” of the precipitation coming from north Texas has rapidly cut off, with at least a temporary reprieve in precipitation an estimated four hours from Oklahoma City (if it stays as it is). This will not be the end of precipitation as regeneration is anticipated, but it may represent a reduction in overall amounts. Meteorologists are still calling for sleet and/or freezing rain in our area through 10 PM tonight, followed by snow into at least mid-day tomorrow. Actual accumulations are uncertain, but still potentially two inches of ice/sleet and possibly up to eight inches of snow.

We are continuing to monitor the situation and will provide updates as necessary.

Winter Weather Update 1-28-10 13:30 PM

We are currently at Level two activation at the RMACC.
Conditions continue to deteriorate in western and central Oklahoma, including ice accumulations in portions of Oklahoma County as a mixture of freezing rain and sleet continues to fall. Reports of broken tree limbs and downed power lines and poles are beginning to be more prevalent, particularly west of the County and into southwest Oklahoma where several areas have already been severely impacted. We can anticipate additional accumulations particularly on structures and items not in close contact with the ground, although ground coverage is being experienced.

An approaching/developing low pressure system in the SW part of the US will cause moisture and overall storm development to increase, thus “feeding” the situation here in Oklahoma and central Oklahoma. Current temperatures are in the upper 20’s in Oklahoma County with wind speeds recorded at 24-28 mph, although a large number of Mesonet sites throughout the state are beginning to be covered with ice and are unable to provide wind-related information.

All flights at Will Rogers Airport have been cancelled and travel is discouraged in a large portion of the state. OG & E currently reports no power outages in our area although larger portions of southwest Oklahoma have experienced power loss.

Precipitation is expected to change to snow sometime this evening or tonight and eventually end sometime tomorrow (Friday) afternoon.

I have attached two National Weather Service graphic products depicting both the current situation and predictions for this afternoon and evening.

We are continuing to monitor the situation and will provide additional information as available.

Winter Weather Update 1-27-10 1400hrs-EOC

We have just completed two additional conference calls with State Emergency Management and the Tulsa and Norman National Weather Forecast Offices, all of which continue to emphasize and reinforce the same basic information as has been previously provided, with one potentially significant modification, that of a shift in the “bands” of precipitation (by type) slightly to the northwest. As the attached graphics indicate, we here in central Oklahoma are now potentially facing increased amounts of ice and/or sleet, with slightly decreased amounts of snow. The heavier snowfall is still anticipated in northwestern portions of the state. This does not mean central Oklahoma will not receive snow, just comparatively lesser amounts than previously predicted, with a potential increase in ice or sleet (see graphic 1-27-10 1300 Predicted Totals).

I continue to emphasize that storm tracking differences of even a few miles can significantly change actual precipitation amounts and type. Additionally, air temperatures above the surface are the determining factor as to what type of actual precipitation will be experienced, and because of the slow movement of these “air masses” and their relative depth or thickness, exact predictions are difficult. Also, weather professionals continue to emphasize the importance of wind conditions with this event, which are expected to be 20 to 30 mph with higher gusts possible.

One of the greatest challenges with this event is determining the exact timing of freezing conditions as the system moves into Oklahoma. Current predictions indicate freezing air temperatures will likely exist in our area around the 0700-0800 timeframe tomorrow (Thursday) morning. It sounds like the major portion of the precipitation may not actually arrive until closer to noon, but again, we are looking at specific details and they are difficult to accurately identify.

Please note that central Oklahoma is included in a Winter Storm WARNING for Thursday morning into Friday. From the National Weather Service-

Today is the last day to prepare before a major winter storm arrives in Oklahoma and north Texas. Beginning tomorrow…. rain will change to freezing rain and sleet from western North Texas and northeast across southwest and central Oklahoma. Widespread power outages will be possible… further north, across northern Oklahoma… the main impact will come from very heavy snow, possibly up to 10 inches in some areas.


We will continue to monitor conditions and forecasts and keep you updated as information is made available.

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