Cold tonight and tomorrow, otherwise a relatively quiet week in weather

After getting bombarded by storm after storm this winter, it appears that the pattern for the next several days will finally relax, as no major storm systems will be on the horizon. There is a storm system developing in the Southeast states, but it will be become disconnected with the jet stream. This means that there will be no northern stream piece of energy to phase with it and bring it up the coast, thus the storm will stay to our south for Thursday and Friday.

Another inconvenience we have to deal with, however, is the cold temperatures for tonight and tomorrow. Today saw decent moderation, as the previously cold high pressure system slid out to sea, and allowed our flow to become more maritime in nature. But as this high pressure system moves out, another strong one will be moving in tonight and tomorrow. A 1040mb high pressure system will pass overhead, and allow for our winds to turn due northerly tonight, which is the most efficient way to generate cold into our area, since that wind direction allows for no downsloping, nor moderation.

While this run may be slightly overdone in cold, the 4KM NAM shows bitterly cold temperatures being advected into the region tonight. (PSU E Wall)

While this run may be slightly overdone in cold, the 4KM NAM shows bitterly cold temperatures being advected into the region tonight. (PSU E Wall)

The wind direction coming purely from the north via a 1040mb high (strong cold air source) leads to forecast very cold temperatures tonight — dropping into the mid teens in the City, and perhaps upper single digits to around 10 in northern and northwestern suburbs. There won’t be any true radiational cooling, however, due to the strong winds, so temperatures may tend to run a bit more uniform tonight.

Some data indicates the initial slight chance for a snow shower tonight as temperatures aloft drop more than they do at the surface initially, creating some instability. However, we feel that the strong high pressure system will create enough subsidence to limit any snow shower activity, except for areas further north and west with a bit more elevation/orographic lifting.

Moving forward to tomorrow, the high pressure will slowly be moving eastward, but primarily remain anchored on top of us. The strong March sun angle, plus the winds turning a tad more easterly thanks to the high departing throughout the day will allow temperatures to recover somewhat, but cold air may still remain stubborn at the surface. The high will not move away quickly enough for temperatures to get above freezing, thus we feel that temperatures will remain in the upper 20s tomorrow.

Today's GFS (above) as well as many other models show the northern stream and southern stream staying separate, which allows precipitation to miss out to sea. (PSU E Wall)

Today’s GFS (above) as well as many other models show the northern stream and southern stream staying separate, which allows precipitation to miss out to sea. (PSU E Wall)

Going back to the storm system down south, notice on the top left panel, there is a potent piece of energy off the Carolina coast. But it remains entirely separate from the northern stream, as that piece remains in Canada. Since they miss interacting with each other, the cold from the northern stream stays to the north, and the southern stream goes out to sea, as evidenced by the bottom right panel showing precipitation missing us. We may have some high clouds on Friday from the storm system, keeping temperatures into the upper 30s to around 40, but no precipitation is expected.

What this does mean is that once the clouds clear, we can expect a decent warmup for Saturday, with temperatures potentially eclipsing 50 degrees.  Winds will turn westerly from the counterclockwise flow via the northern stream energy, but the airmass will already be relatively warm — downsloping westerly winds in a warm airmass could definitely yield 50+ degree temperatures. The northern stream energy may finally drop down on Saturday night into Sunday, producing a cold front to cool things back down a tad. But we are leaning towards Saturday being a very enjoyable day to be outside, at least relatively speaking.

The next significant storm threat does not appear to be until March 12 or so, give or take a day. There are lots of uncertainties regarding precipitation type, but there are indications that the pattern next week does support a large storm system of some kind.

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