So far this March, temperatures across the Contiguous US have average out very slightly below average. The West and much of the East Coast as featured below average temperatures while the Central US into New England have been on the warmer side of average. Big changes are on the way for some areas, in addition to more nor’easters. Winter is making a comeback keeping spring on hold.
One of the key favors to the current pattern is the state of the pressure pattern across the Northern Hemisphere. The NAO (North Atlantic Oscillation) has been in negative territory for weeks now, which signifies a blocking pattern with a high pressure over Greenland, allowing for cold air to spill into the Eastern US along with stormy weather. This negative NAO has been responsible for the three nor’easters that have slammed the Northeast so far this March.
Based on the model guidance, they are already honing in on the next potential nor’easter mid-next week, as another trough of low pressure moves across the country from the West Coast. Depending on the orientation of this trough, and the position and timing of the separate pieces of energy that will go into this next storm, there is certainly some risk for snow in the Mid-Atlantic and New England. It depends on when these components come together to form the coastal low. This storm can simply head out to sea, it can hug the Mid-Atlantic coast, or head toward the 40/70 benchmark and slam New England once again. At this point, we don’t know where this storm is headed but its development is likely. Then beyond then, another nor’easter may form next weekend or early in the following week. At this time, monitor the forecast from WeatherOptics and if the threat for the impact from a nor’easter increases, we’ll be sure to let you know.
Another interesting factor to point out is how the NAO is expected to evolve to a neutral or slightly positive phase beginning mid-next week. This is the same time the next potential nor’easter would form. Not always, but sometimes when you get this change in the NAO, it triggers a coastal low. When the NAO reached a record low sigma value on March 2nd, that sparked a highly-impactful coastal storm. The same can happen during these transitions from negative to neutral or from negative to positive.
Along with the risk for an additional nor’easter or two through the end of March, the weather pattern is expected to be very active out West, which is great news because states like California are in a rain and snow drought. Storms every few days are expected to move into the West Coast, keeping the region wet and snowy at times. One last area where wetter than normal weather can be expected is across the Southeast as disturbances move through associated with troughs of low pressure. Severe weather may also become more prevalent across portions of the Plains and Southeast during the last two weeks of March.
Now in terms of temperatures for the remainder of March, cold air will dominate the Lower 48 overall. For the rest of this week, below average temperatures are forecast in the Northern Tier while the West sways from warm to cool and the South transitions from cool to warm this coming weekend. Brief bouts of milder air may invade the Northern Plains and Upper Midwest around this weekend, but cold air will be the dominant air mass.
Then as we get into week 4 of March, a cold outbreak is expected to occur. The warmth across the South will become a distant memory by the middle of the week as a new upper-level trough, which may spark that next coastal storm, leads to widespread below average temperatures for the East while warmer air from Mexico bleeds into portions of the Southern Plains during the latter half of the week. The Northern Tier and the West will also experience below average temperatures throughout the week. At times, especially in the Northern Tier and Northeast, temperatures could end up being as much as 20 degrees below average. Otherwise, it will generally be 5 to 10 degrees below normal.
By the final week of March, the pattern will evolve some more with a strengthening PNA (Pacific/North American Pattern), resulting in ridging along the West Coast US. What happens upstream will affect downstream, and because of that ridge over the West Coast and eastern Pacific, a trough will result over the Eastern two-thirds of the US, keeping temperatures cooler than average, although Florida and the Gulf Coast may enjoy warmer than normal temperatures.