Getting A Pumped Up Ridge

Channel your inner Hans and Frans -- Mother Nature is about to pump *clap* up the atmosphere with a ridge of high pressure in the mid atmosphere, resulting in a stretch of rather hot weather late next week or next weekend locally, with a run at 100 degrees not out of the question locally.

Mercifully, we will not see the worst of the heat and humidity.  That honor belongs to the Midwest, where this ridge will set up shop and temperatures could reach or breech 100 degrees in Minneapolis, Chicago, St. Louis, and other cities for a few days next week, with Chicago potentially seeing several days of upper 90's and near 100 degree temperatures.   This heat wave has the look of 1995's long duration heat wave to it...thankfully, it should not last as long but it could be just as nasty for Chicago and for the Midwest and it would not surprise me if there were fatalities in a number of the big cities from the heat.

 The question regarding "how hot we get" comes down to position of the upper ridge over us for Thursday-Saturday.   The GFS in the afternoon runs on Friday centered the ridge over the Appalachians, a pretty good spot for us to get some hot weather as upper levels are rather warm nearby.   The core of the heat ridge is near us and temperatures could approach 100 in such a scenario.  The Euro is a bit farther west with the heat core, over the Ohio Valley on Friday evening, which results in mid 90's for highs...still hot but not "prime heat."    The models have flipped and flopped over which scenario they prefer but in either scenario we're talking mid 90's, at least, for Thursday through Saturday.

If the "cooler" solution were to verify we could see some thunderstorm complexes track closer to the region around the periphery of the heat ridge.   The "ring of fire" of thunderstorm activity around the upper ridge is certainly possible...if the ridge isn't quite as strong or is centered a bit farther west we could see some thunderstorms in/close to the region during the heat event.

Factoring in humidity, heat index values could reach 105 during this time frame.   It will be oppressive but not as bad as in the Midwest, which could see heat index values around 120 on Monday or Tuesday in some locations.   The heat is back on...and this is likely the prime heat event for the year across the country.

Omega For The Block

A developing and strengthening ridge of high pressure in the Central Atlantic is putting the brakes on the upper level low in the Western Atlantic from moving anywhere anytime soon, with the resulting weather pattern stuck in a rut of dryness...not that anyone will complain about a prolonged dry stretch of weather!   The upcoming pattern, called an omega block because of the Greek letter Omega, typically means weather patterns change little...if any...over a period of days.

You can see the evolution of the high pressure ridge from Tuesday on across the Central portions of the Atlantic.  These strong ridges of high pressure and blocking patterns are rather common at this time of the year -- thanks in part to a weaker jet stream unable to break down ridges of high pressure and also in part to upper level lows that still have some pop in them thanks to lingering chill in the upper atmosphere.   However, the high pressure ridge's strength plus the lack of a "kick" from the jet stream means the upper level low moves little over the coming days.   With the upper low in the Western Atlantic, we are in the confluence of the western side of the low, which means air is generally stable and storm systems that try to move east are shunted southeast around the flow of the upper level low.    While day to day variations may occur, with Tuesday possibly a bit more cloudy than the other days early this week, the next five days will be dry and generally mild.

As we work into late week, the upper low slowly slides east and a second storm system in the Midwest begins to nudge eastward.   This system will move as slow as the upper low in the Western Atlantic -- again, thanks to the strong Central Atlantic high pressure that's preventing much movement.  The fair weather in place for much of this week gives unfortunately to a thunder threat from this Midwest storm system...just in time for the weekend.

The storm system in the Midwest moves little between Friday and Sunday, also stuck in place the last remnants of the upper low in the Western Atlantic spin themselves out just east of Bermuda.   This means off and on thunderstorms will eventually work in -- probably Saturday -- and could last into the early parts of next week, with the potential for a fair bit of rain if this pattern holds.

In any case, the next five days should be rather nice and a great stretch of late Spring weather.