Warmer, Chance of Rain This Weekend.

Thought perhaps a look at the upper level wind pattern will help to explain how our weather will be changing in the days ahead.  These charts show the wind flow aloft at the 500 mb level or approximately 18,000’ above sea level.  The colors represent where the strongest winds are at that level and I have labeled some of them as either the jet stream or as a jet streak. 

The first one shows the pattern as analyzed at noon today and the most obvious feature is the very strong jet stream in the Pacific and headed toward the W Coast.  There is also a very weak disturbance located just to our north which I have labeled with a capital L.  This system helped to keep us overcast today and will contribute to the low clouds and possible fog/mist/drizzle again tonight, particularly for the more northern counties.  As that system moves on eastward, drier air aloft will move in behind it so we expect the clouds to be thinning during the morning and lots of sunshine for the afternoon. 

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However, with dew points holding in the upper 40s today and a light SE breeze through the overnight hours, temperatures will not cool off much and we should hold in the mid-upper 40s through the night.  Southerly winds will become rather gusty during the day Friday which together with the sunshine should push daytime highs into the mid-upper 60s.  Keep in mind, the normal temperature range at this time of year is 48/27.

Saturday will also have a brisk southerly wind but cloud cover will be returning along with chances of rain that night.  It will be another very mild day for this time of year with morning lows again in the 40s and daytime highs well into the 60s. 

Notice this next chart of the wind flow at 18,000’ valid Sunday morning.  The pattern has buckled with a series of upper level storm systems, one located just SE of us, another in the Pacific off the W Coast, and another further out in the Pacific.  As mentioned yesterday, the one just SE of us is in a position that would ordinarily provide a major snow storm, except it has no cold air to work with.  Instead, we will have a good chance of rain and perhaps even some thunder Saturday night ending by Sunday morning as that system moves on eastward.

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As you can see on our forecast page, this system will push a cool front through Saturday night and the northerly winds at the surface will cool us off during the day Sunday and to start the day Monday.  The cool down will not last for long though as we will have another big warm-up for early next week.  Again, this system just does not have any cold air to work with and the quick return to southerly winds for Mon/Tue will result in very warm conditions once again.

However, the pattern aloft will undergo more significant changes later in the week as you can see on this final chart.  This one is valid for one week from today and you can see the wind flow aloft is much more amplified with more of a N-S flow as compared to the more zonal or W-E flow of today.  That will allow colder air from Canada to penetrate further south and into OK which is why we are expecting temperatures to be closer to normal if not cooler than normal for the latter part of next week and through that weekend.  However, that northerly flow aloft is not coming across the Polar regions, only out of Canada so it is not likely that we will see another arctic outbreak such as has already occurred on several occasions this winter.

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Now, notice the 7 day QPF and as was mentioned in yesterday's blog, it is painting a very wet pattern for the W Coast and locations further east of us.  That strong jet stream and the embedded storm systems moving onto the W Coast in the days ahead will keep them wet, but the storm system impacting us this weekend will only have limited moisture to work with.  That is, until it gets further on east where it will be tapping into a deeper layer of moisture from the Gulf of Mexico and producing locally heavy rains/storms for those locations.

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As for the cooler conditions of later next week, again no arctic air so not the bitter cold of recent events and the pattern does not currently support any big storm systems coming our way so little or no precipitation during that time frame either.

So, the bottom line is that the rest of this week and into early next week will continue to have much warmer than normal conditions despite a cool front arriving Saturday night.  But, the month will end on a cool note with temperatures back to near or below normal conditions.

As always, stay tuned and check back for updates.

Dick Faurot