Possible Storms Thursday, Cooler & Wet to Start the Weekend

Have mentioned on several occasions in recent blogs regarding the persistent zonal or W-E flow aloft that has dominated our weather pattern since early in January.  That flow has kept the really cold air bottled up far to the north and has also produced heavy precipitation along the W Coast of the U.S. but very little for us.  I mention all that because the longer range guidance is coming into better agreement that this pattern will finally begin to change over the coming week or so and that will bring colder air our way along with better chances of precipitation. 

To illustrate, the first map is valid for Noon today at the 500 mb pressure level or approximately 18,000’ above sea level.  The second map is for the same level only valid for Tuesday morning of next week.  The colors in both represent where the strongest winds at that level are located, in other words the jet stream which I have labeled.

Notice the very strong W-E or zonal flow from the Pacific and across much of the continental U.S. evident on the map for today.  Embedded within a flow such as that will be weaker disturbances that are difficult to time and difficult to measure since much of the energy is out over the Pacific and the very fast flow moves systems along at a very rapid rate which is difficult to resolve.  Current data runs suggest a couple of those embedded systems will be impacting our weather with a chance of showers/storms for Thursday, particularly for the afternoon into the early night time hours.  Another, stronger one, now looks to be headed our way for Saturday with a more widespread chance of showers/storms.

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Now, notice the second map which is valid for Tuesday morning of next week.  Clearly, the flow aloft is much more amplified with a more northerly component over OK.  That northerly component is not connected to the arctic, but even so that flow will bring noticeably cooler air our way.  In fact, as you can see on the forecast page, we are trending the forecast for a period of cooler than normal temperatures starting this weekend and into next early week.  Not arctic air by any means, but quite a contrast to the last half of January and February.

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Now for the details.  Southerly winds will continue through the night tonight and with very dry air still in place, temperatures will be dropping into the upper 40s to start the day Thursday.  Certainly not as cold as we were this morning when we bottomed out at 35.  High level clouds will be streaming this way during the day, but strong southerly winds and plenty of sunshine should still push our afternoon temperatures above the 74 that we registered today.  Those strong southerly winds means another high fire danger day, but moisture will also be surging northward during the day.  Together with the daytime heating and a cool front moving this way that night will produce at least a chance of a few storms, some of which may be severe with primarily a wind/hail threat.

A more NE wind on Friday will counter mostly sunny skies so temperatures will be cooler with afternoon highs in the 60s.  A stronger system aloft will then move across the state on Saturday as the flow aloft begins to amplify as described earlier.  As a result, have trended the forecast much cooler and wetter throughout the day Saturday as NE winds for most of the day and widespread rainfall should hold us in the 40s for the most part.  Notice also that the QPF valid through Saturday has also picked up on these trends and is now showing the potential for some significant rains for the eastern half of the state.  We certainly need the moisture but they need it out west also. 

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At any rate, Sunday should see some clearing and if the skies clear quickly enough by morning, then freezing temperatures now look to be a good bet.  The mostly sunny skies should allow temperatures to make it back into the 50s during the day along with a return to southerly winds that afternoon.

Yet another system will be moving through on Monday with winds shifting around to the north during the day keeping us cooler than normal.  As the flow aloft continues to amplify as described above, then even cooler air will be moving in Tuesday and there may be enough energy aloft to produce some light precipitation by Tuesday morning before the skies begin to clear later in the day.  Right now, it does not appear that adequate moisture will return in time for anything more than some very light precipitation with that particular system.  But, this air looks to be much cooler and widespread freezing temperatures are currently anticipated for Tuesday morning.

Wednesday will also get off to a chilly start but a return to southerly winds should result in a nice rebound.  In fact, the long range guidance still suggests that temperatures will average above normal over the 8-14 day time frame which would be the rest of next week and that following weekend.  Notice there is also at least a chance of scattered showers/storms during that time frame as well.

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So, stay tuned and check back for updates.

Dick Faurot