Premium Long Range: More Heat & Severe Weather Risks Going Into July

After a few showers and thunderstorms this afternoon, more pleasant weather with temperatures near to slightly below normal will continue over the next few days. But there are many signs of overall pattern change support more typical mid-summery weather with some hot temperatures, humidity and some thunderstorms over the region, as we move into the few weeks of July.

A trough will dig into the Northern Rockies and Plains during the middle of this week. This will cause ridge build over Northeast and Mid-Atlantic region late this week and into this weekend. This will much warmer and humid airmass to return to region. Temperatures with more southwest flow and enough sunshine could exceed 90°F degrees in many spots by Friday and Saturday. Some afternoon sea-breezes each day will likely some coastal sections a little cooler. But it still be uncomfortably humid.

But a couple of disturbances rolling northern periphery of this ridge, may trigger some complexes of scattered showers and thunderstorms, that could move south into region by Thursday night or  Friday.  Then the trough over Northern Plains, the progress east into Great Lakes and Northeast by early next week. This will frontal boundary to begin pushing southward for rest of holiday weekend. This will result more cloud cover on by late Saturday and perhaps into Sunday with perhaps more widespread showers and thunderstorms. Stronger wind fields and a plume of subtropical moisture may support a more organized threat for severe weather and heavy rainfall, in our region.

Then a some cooler, drier airmass may come in for Monday. Before another frontal system and shortwave trough may bring more showers and thunderstorms on July 4^th. Another brief cooldown may follow behind this system. However, much of the guidance indicates next week will feature a split flow out over the West Coast and North Pacific region with a Rex block- like configuration over parts the Western Canada, Alaska with an upper-level low over the Gulf of Alaska. Meanwhile the AO/NAO will be trending positive with deep vortex positioned near Baffin Island. This pattern will support more expansion of the ridge from Central and Northern Plains into the Mid-Atlantic and Northeast regions, particularly during the July 6th – 12th period.

Now we need to consider that, troughiness more positioned over Northeast Pacific or Northwest US, may support more prolonged, extreme heat ridge will to be over Western and Central Parts of United States. But this pattern will likely support more than just a couple days of some heat and humidity over the Northern Mid-Atlantic and Southern New England regions. Perhaps even a heat wave that last for several days with temperatures peak out near 95-100°F. This pattern may also lead to severe weather for parts of Northern Mid-Atlantic region, with EML (elevated mixed-layer) advection occurring on mid-level northwesterly flow and more disturbances running enhance dynamics along a frontal zone or thermal gradient.

Looking beyond this period, it may be more difficult to sustain more extreme heat in the Northeast.Sea-surface temperatures current over the North and Tropic Pacific support neutral ENSO conditions. Latest indications, based on zonal wind analysis and forecast charts are that the QBO easterly winds are descending from 10mb to 30mb and 50mb. Recent research has shown the QBO modulates the MJO less during the more easterly phase. Thus this all the  MJO to strengthen and propagate from the Western Pacific to over Western Hemisphere and Africa sometime in the next 2-3 weeks. But with more heat prior, temperatures for July may still average above normal by couple degrees.

This could support more cooler or wetter pattern with more profound troughiness over Eastern US during last two full weeks of July. The MJO passage may also result in another period more heightened tropical cyclone activity over Eastern Pacific and Atlantic Basin. So we may have to watch for more tropical remnants or influence from the tropics in our  convective pattern. This systems tend to add more warm, tropical moisture in the atmosphere, that washout EML plumes before the reach the Northeast or Mid-Atlantic regions.

 

So don’t worry, if you enjoy more typical heat and humidity and with afternoon and evening thunderstorms we see during the mid-summer for our area. Nothing too extreme or out of the ordinary is anticipated for the Northeast of Mid-Atlantic. Later in the month, we may have to deal with more cooler, wetter conditions, as well. But that is still a long time from now. Stay tuned for more premium article or video updates on the long range pattern over the next few weeks!