That this has been the coldest day of the winter so far is evident from the map on the right courtesy of the OK Mesonet which shows the high and low temperatures for today. Notice that very few locations even made it above the freezing mark today and with clear skies and light winds, temperatures will really plummet tonight. In fact, the normally colder valley locations will likely be in the single digits with lower teens elsewhere to start the day Sunday.
Usually, the really cold air will stick around for awhile, but the surface high pressure ridge is expected to slip rather quickly on eastward during the day Sunday. That will allow our surface winds to veer around to a more SE and eventually a more southerly direction by late in the day. Together with lots of sunshine to start the day, that should allow for a nice rebound with highs at least above freezing for Sunday afternoon.
Then, it starts getting interesting as a disturbance in the upper levels of the atmosphere will be moving across the state Sunday night and Monday. This system does not appear all that impressive now, but it is coming from the Pacific so we really have not had a good look at it just yet. Better data sampling tonight and Sunday will give us a better idea of what we are dealing with when it reaches Oklahoma.
At any rate, this is shaping up to be an unusual situation to say the very least. As mentioned this morning, it is very rare for us to get wintry precipitation and have a southerly surface wind, but that is what we are facing for late Sunday night into the morning hours of Monday. The surface high will be sliding on eastward allowing our surface winds to become more southerly and with the disturbance aloft approaching, it will cause a stronger low level jet to develop as well. This combination usually produces temperatures that are too warm for us to have any significant wintry weather. But this time, it appears that the surface air will be cold enough and dry enough that when precipitation does develop there will be enough evaporative cooling to maintain a vertical thermal profile that will be below freezing at least till mid morning of Monday. So, with that in mind all indications point to snow developing around midnight Sunday night and continuing into the morning hours of Monday. Temperatures Monday morning will start off near freezing so some travel issues can be expected. However, as the day wears on those strong southerly winds will bring temperatures up so that the precipitation should be changing over to a rain/snow mix or perhaps a snow/sleet/rain mix at times before ending as a light drizzle by late afternoon.
Total amounts are expected to be on the light side with a liquid equivalent of only ¼" or so. That would translate to snowfall accumulations on the order of 1-3" with locally higher amounts if it were all to fall as snow. Since that is not likely to happen and since there will be a transition to sleet or rain as it is ending, then there may not be very much on the ground at all by the time it is all said and done.
That will be followed by much milder conditions for the rest of the week and even another chance of rain by late Wednesday or that night.
Of course, this is all subject to change as we get better data over the next 24 hours. So, stay tuned and check back for updates.
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