As has been mentioned on several occasions, our meteorological winter for the state is considered to be the calendar months of Dec-Feb. With that in mind, today is the last day of winter; but this is Oklahoma after all and it ain't over till it's over if you will pardon the expression. That will certainly be the case through this coming weekend with scary cold air for the time of year invading the state and only slowly moderating later in the week.
Before getting into that, a brief look back is in order. Notice the first map on the right, courtesy of the OK Mesonet. It shows the total liquid equivalent moisture over the last 90 days; in other words over the course of the winter. Not much. In fact, this will go down as one of the driest winters on record ranking in the top 10 in that particular category. Not only that, but so far the calendar year of 2014 is the driest on record here in Tulsa. Not only has it been dry, but each month this winter has been colder than normal and the month of Feb wound up about 6 degrees colder than normal.
And, our forecast for the beginning of March certainly suggests this is the winter that will not give up easily. Notice the second map on the right which shows the amount of the U.S. that is covered by snow. I point that out because some bitter cold air is moving southward from above the arctic circle in NW Canada and with snow covered ground into N KS, it will not be moderating much. As a result, another surge of arctic air will be arriving during the day Saturday which will keep temperatures below freezing all day Sunday and all day Monday. Notice the third map on the right which shows the number of days that we did not get above freezing so far this cold season. For the Tulsa area, we current stand in third place in that particular category and although we will add to the total over the next few days, we will not move up in the rankings because the cold seasons of 1977-78 and 1978-79 are so far ahead of where are to this point.
Now for the specifics. Overnight temperatures tonight will be fairly close to normal with morning lows in the low-mid 30s under partly cloudy skies and light NE winds. Temperatures Saturday will show a wide range across E OK with the more S and SE counties likely to reach the 60s before the cold air moves in later in the afternoon. The more northern counties will be in the 40s and perhaps the lower 50s before the leading edge of the real cold air arrives.
However, as the day wears on, northerly winds will become strong and gusty and temperatures will be plunging. We expect to be in the 20s by midnight and the low 20s to start the day Sunday. Sunday evening will likely be in the lower teens. Along with the bitter cold will come northerly winds of 20-25 mph with higher gusts. That will put wind chill values below zero pretty much all day. Single digits will be possible by Monday morning if the skies clear out quickly enough and daytime highs on Monday will be in the teens to low 20s. We do not expect to get back above freezing till sometime Tuesday afternoon. This event will likely set records for cold, particular with respect to cold daytime highs.
At the same time as this bitterly cold air is settling over the state, a strong disturbance aloft will be moving this way from the west. The main circulation of this system is still out over the Pacific Ocean as I write this so there remains some uncertainty regarding intensity/timing/location going through the weekend. One thing that is certain though is that a shallow dome of arctic air in place at the surface and warm, moist air forced over the top of it is a recipe for an ice storm. If you noticed the chart I provided in yesterday's discussion, you saw how the vertical profile of temperature impacts wintry precipitation type. Indications now suggest this event will be primarily composed of sleet with some freezing rain mixed in. That will be starting after dark Saturday night and not ending till Sunday night. As the event draws to a close there will be some colder air aloft moving in as the precipitation moves out, which will provide a window of opportunity for some snow late Sunday into Sunday night. Total amount of frozen precipitation in the form of sleet/snow could exceed 1" with locally higher amounts possible further north into KS where more snow is likely that night. In other words, this will likely have significant impacts on travel for Sunday/Sunday night and potentially power issues as well.
As mentioned, it appears the precipitation will be ending Sunday night and lots of sunshine is expected for Mon/Tue. Despite that, temperatures will be well below freezing all day Monday, single digits will be possible that night, and we will struggle to get above freezing on Tuesday. Conditions will be moderating as the week wears on although there are some indications of another weak system bringing clouds and perhaps some light precipitation late Wed into early Thu.
After that, we should end the week on a much milder note. However, as you can see from the last two maps on the right which take us into the middle of March, the long range signal is for below normal temperatures and not much in the way of precipitation through that period. Again, the winter that just will not give up easily.
So, stay tuned and check back for updates.