For almost a year now, amateur and professional astronomers have been tracking the progress of Comet ISON. Discovered in 2012 and named after the International Scientific Optical Network (ISON), ISON was of unusually large size with estimates ranging from 1 to 3 miles in diameter. It’s track toward and around the Sun was going to make it very susceptible to disintegration, but the size had an equal number of forecasters predicting that the comet would survive the encounter and produce a beautiful sky show for us in December.
That tight pass around the Sun occurred yesterday, and initial observations gave every indication that the results were not good. The comet started to dim upon final approach, then appeared to vanish all together. The reports started flying out that the comet didn’t make it, and thousands of observers all over the world started to agonize in disappointment. After all, some had declared that this could be the comet of the century, a once in a life-time event. For a sky observer, to have that yanked out from under you is hard to swallow. Will I even be alive the next time a good comet comes around?
Then the incredible happened. As images of the Sun were monitored, something appeared to start tracking away on ISON’s projected path. There were many initial questions. Was this just a debris trail? Was it a very small remaining chunk of the comet? Was it a lot of little pieces? By late evening on the 28th, it had become apparent that a substantial piece of the comet was still intact. By this morning, it had started to brighten rapidly and emitting a nice tail of dust and gas. Basically, Comet ISON had survived! A common line among comet observers is that a comet is like a cat, it has a tail and will do whatever it wants. Well, if this comet is like a cat and had nine lives, it just spent about eight of them!
The hard part is over. Over the next few days, ISON will be monitored closely to see how much of it is left and what kind of display in the night sky will be possible. However, it does appear that “something” will be around for sky photographers over the next several weeks. With a little luck, it will be a nice naked-eye object as well.
There is pretty good agreement among model solutions concerning the weather over the next several days. Oklahoma will reside under increasing moderate west southwesterly upper level flow through Sunday. A weak wave embedded in the flow will result in low pressure tracking eastward near the Red River on Sunday. This will help increase low level moisture and result in an introduction of showers to the forecast across the southeast 1/2 of the state. Otherwise, this period remains dry.
Temperatures will slowly modify to normal levels through the weekend.
Thursday morning: 29
Friday morning: 27
Saturday morning: 32
Sunday morning: 36
Temperatures across much of Central and Northern Oklahoma dropped to the teens – or colder – this morning. The low temperature in Alva reached 9 degrees. In Okarche, the low of 16 degrees set a record for the date. The previous record was 17 degrees set in 1993 and reached again in 2002.
Snow fell across portions of Western and Southern Oklahoma on Sunday, November 24th. A localized, but very heavy band of snow set up from Northern Harmon County to Central Kiowa County, where snowfall amounts ranged from 8 to 13 inches. The heavier amounts were at Granite (10 inches) and Vinson (13 inches). The attached satellite image is from Tuesday morning (26th) showing remaining snow cover over Southwest Oklahoma and the Panhandle.
The area most likely to see widespread precipitation over the next 18 to 24 hours will be Southeast Oklahoma. Across the remainder of the state, there will be patches of very light snow through Monday afternoon as the upper low currently over the Texas Panhandle slowly digs toward the Texas Gulf Coast. No accumulating snow is expected outside of far Southeast Oklahoma where 1 to 2 inches will be possible through Monday.
High pressure will build over the Rockies as the low shifts east of the Southern Plains by Wednesday. Surface high pressure will continue to build into the state through Wednesday, but falling pressures over the High Plains will result in a return to south winds over the western half of Oklahoma late on Wednesday.
Monday will be mostly cloudy across the state, before clearing begins to occur late on Tuesday. With a little bit of remaining snow cover and varying sky conditions, temperature forecasts will be a challenge. However, it is likely that temperatures will be below to much below normal through the period.
Monday morning: 25 / Flurries likely
Monday: 33 / Flurries possible
Tuesday morning: 24
Wednesday morning: 19
Another round of winter precipitation affected Okarche on Sunday the 24th. The total snowfall of 1.1 inches broke the old record for the day of a Trace set in 2004. Also, the high temperature only reached 27 degrees – setting a record for the coldest high temperature on the date. The previous record was 32 degrees set in 1993 and again in 1996. The low high was only two degrees away from the all time November record of 25 degrees, which was the high on November 25th, 1993.
A very complex weather event will be unfolding over the next 24 to 48 hours. Strong upper level flow extends from Western Canada to the Eastern U.S. Meanwhile, a strong closed upper low is located over the Southwest U.S. This feature is moving eastward toward the Southern Plains. Models are in general agreement that a strong short wave trough embedded in the northern stream flow will dive toward the Midwest as the Southwest U.S. low moves over the Southern High Plains. The interaction between these two features is expected to cause the approaching upper low to deepen and begin to dig toward South Texas from late Sunday through Monday. Precipitation will be expanding northeastward out of West Texas with the approach of the upper low. The question becomes how much and how far northeast will it expand? Currently it appears that the NAM/SREF are overdoing precipitation amounts, while the GFS seems suspiciously lacking. As the upper low begins to dig away from Oklahoma on Sunday, it becomes easy to lean toward the drier GFS, but not quite to the degree of recent solutions.
At the surface, temperatures over Oklahoma have moderated some this afternoon. However, a secondary surge of cold and dry surface air is moving south associated with strong high pressure currently located over Iowa. Temperatures by morning will have fallen below freezing across all of the state. They will have a hard time getting back to near freezing during the day on Sunday as precipitation begins to fall through the dry air near the surface. With this in mind, most places will be seeing all snow on Sunday, but a few places may see a sleet/snow mix at times.
Snow is expected to begin near or just before daybreak across Western Oklahoma. The most likely area to see significant snowfall will be across Southern and Western Oklahoma where amounts of 2 to 4 inches are possible. From Northwest to Central to Southeast Oklahoma, snowfall of 1 to 3 inches will be possible. Most of the heavier snow will have ended by Sunday evening, but some light snow may occur off and on through Monday.
The high temperature in Okarche on Friday the 22nd was 29 degrees. This sets a record for the lowest high temperature on the date. The previous record was 37 degrees set in 1937 and again in 1947.
The total snowfall for the day was 0.3 inches. Previously, no snowfall had been recorded on the 22nd.
Unseasonably cold air will remain in place across Oklahoma through the weekend. Our attention has now turned to a closed upper low over the Southwest U.S. which will be moving toward the Southern Plains over the next 72 hours. Model data is in fairly good agreement with the track and strength of the low. Increasing lift will overspread at least the southwest 1/2 of Oklahoma on Sunday, resulting in the development of widespread precipitation. Forecast soundings suggest that this precipitation will be a combination of a sleet/snow mix, and it is possible that some places will see all snow.
There exist many uncertainties regarding the exact location of the heaviest snow and snowfall amounts. However, at this time it appears that Southwest Oklahoma is most likely to see accumulating snow. A broad area from Northwest to Central to Southeast Oklahoma will also likely see some snow, but the impact is more uncertain.
Cold air already in place before lifting from an approaching storm system arrives is critical to heavy snow events in Oklahoma. With this in mind, the pattern is one that will be capable of producing a large area of 1-3 inch snow, with isolated amounts of 4 or 5 inches possible. While nearly impossible to nail down exact locations of the heaviest snow this far out, it appears that the most likely area will be across Southwest Oklahoma.
A very cold air mass at the surface will remain in place across the state today. Precipitation is increasing over the Texas and Oklahoma Panhandles and across Southern Oklahoma this morning. The precipitation is associated with a weak short wave trough which is moving northeastward across the Southern Plains.
As low level cold air advection begins to slow later this afternoon, and as precipitation begins to warm the low levels of the atmosphere from the top down, the freezing line which is over Eastern Oklahoma now will begin to retreat westward. Areas of Western Oklahoma will remain below freezing through the day, but Central Oklahoma will see the temperature climb above 32 degrees. Before temperatures warm, a combination of light freezing rain and sleet will advance northeastward, and the result will be areas of slick roads through the remainder of the morning. The Panhandle will see mostly light snow today which could result in the accumulation of 1 to 2 inches.