To follow up on meteorologist Steve Glazier’s blog, we have a marked warming trend coming for the late week and weekend time frame it seems! This will come as the jet stream shifts its pattern. Recall, the jet stream is a fast flowing river of air in the atmosphere (about 8-12 miles above the Earth’s surface), and generally acts as the “tracks” for storm systems. It is also the divider between warm air (to it’s south) and colder air (to it’s north).
For the past couple of weeks, the jet stream has been generally south of us, allowing for seasonably (and unseasonably) chilly weather! By the end of this week and the weekend (at least), it would appear as though most of the eastern US will see a warming trend. Why? The jet stream will set itself up so that it will be north of our region (meanwhile, a large dip/trough develops out west allowing for cooler air). That ridge (or crest of a wave in the jet stream) will allow warmer air to develop along much of the eastern half of the US.
So, just how warm are we talking? Well, in my experience, these “extremes” or “abnormal” trends are difficult to forecast and typically underforecast several days out. We can look at the temperature field of the middle troposphere temperature around 850mb (or about 5000′ elevation) to see different airmasses. Take for instance Sunday…the 850 temperature was around -6 Celsius. The surface temperature was mostly in the lower 30s. This time of year with a low sun angle, a general rule of thumb on dry days would be to add about 5 or 6c to your 850 temp and convert to Fahrenheit for the surface temp. This rule worked well today. Now think ahead to next weekend…the 850 temp pushes to around +6 to +8c by Sunday! With rain and clouds in the plans, I’ll add about 2 or 4c to that and convert. So a loose thought is that we’ll make it to the upper 40s or low 50s! With any dry time, or sunshine (should it emerge), temps may actually be even warmer than that in the valleys. To make the mountain conversion, we shouldn’t add quite so much to the 850 temp (since the mountain top is much closer to 850 mb than the valleys…). Maybe just add 1 or so and convert. Even here, we are looking at mountain top temps in the mid 40s!