Enjoy Wednesday, Turning Colder Thursday, Cold & Wet Fri/Sat.

As mentioned yesterday, could get real interesting across the state starting on Friday and continuing through the weekend.  Thought the following cartoon would be appropriate regarding our use of that particular phrase.

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At any rate, enjoy the day on Wednesday as the much above normal conditions of today will continue through tomorrow.  The max/min for today was 71/56 as compared to the normal values of 47/27.  Somewhat drier air brought in by the NW winds of this afternoon will result in a morning low in the 40s to start the day, but that is close to our normal daytime high at this time of year.

Gusty southerly winds will quickly return on Wednesday and despite a good bit of high level cirrus cloud cover, we should still make it into the lower 70s.  Those gusty winds together with the dormant vegetation will also create another high fire danger situation throughout the day so be careful with the outdoor activities.

A cold front will be arriving by early Thursday morning shifting our winds back to northerly and also bringing much cooler air back over the state.  In fact, would not be surprised if temperatures are warmer that morning than they will be to end the day.  Right now it looks like the wind shift should be arriving along the I-44 corridor around the 6 AM time frame with temperatures well into the 40s ahead of the wind shift.  We will then drop into the upper 30s following the wind shift with potentially a bit of a rebound that afternoon if we have some sunshine.  However, the much colder air will be arriving that night along with cloud cover and increasing chances of precipitation.

That is where it starts getting interesting as the cold air will be very shallow and likely hang up in the hills of E/SE OK as you can see on the projected temperature map valid for Friday morning at 6AM.  Notice the freezing line is basically located right along the I-44 corridor and given the shallow nature of this system there continues to be considerable uncertainty regarding how well it is being handled.  So far, the data runs have been pretty consistent in having that freezing line in that general location, but there remains the distinct possibility that the surface freezing line could shift a county or two either direction of the I-44 corridor.

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That could be significant as at the same time a strong storm system aloft will be headed this way and will bring abundant moisture up and over the shallow cold air providing widespread precipitation.  That is where the position of the surface freezing line becomes so important as there will likely be a sharp changeover from just a cold rain to freezing rain.  Obviously, the more NW counties are more likely to remain below freezing and therefore have the potential for a significant freezing rain event and the more SE counties look to just have a cold rain.  But, any shifts in that freezing line will make a huge difference in exactly where that changeover takes place. 

Conditions aloft are also very significant in determining the precipitation type and the following graph pretty well describes those conditions in differentiating between snow, freezing rain, and sleet.  Since our ability to monitor the location of the freezing line aloft is even more uncertain than at the surface, that adds additional question marks regarding the precipitation type.

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One thing that is relatively certain is that this will be a very wet system.  The precipitation of whatever form that we receive on Fri/Sat should be relatively light but much heavier showers or storms appear more likely for Sunday when the heaviest rainfall will likely occur.  Again, any amount of freezing rain can cause significant issues, but as you look at the QPF map for this period, keep in mind that the heaviest amounts will likely occur on Sunday when temperatures will be well above freezing everywhere.  However, this could also result in going from drought to flood for some locations.

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Another caveat that needs to be kept in mind is that the storm system that is projected to cause all these issues is still out in the Pacific Ocean where it has not been sampled by our observational network.  That adds additional uncertainty and cannot rule out the possibility of significant changes in the forecast over the next few days until the system does move on shore where it can be sampled and better accounted for in the model projections.

At any rate, as you can see on our forecast page, the showers/storms are expected to be coming to an end early Monday followed by a return to warmer than normal conditions for the rest of next week. 

So, stay tuned and check back for updates as this is a very dynamic system and certainly poses the possibility of some significant winter weather issues, primarily in the form of freezing rain followed by the possibility of some significant flooding issues.

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Dick Faurot