Unsettled Weekend and Watching Next Week Closely

Thu 4/3: Lots to look at so here we go:

Behind Tuesday's storm system, a large high pressure area built eastward from the Ohio Valley yesterday to near New York City Thursday morning. This fair weather center has provided us with mostly clear skies and seasonably cool / dry air both Wednesday and Thursday. Unfortunately, this high will continue to press eastward over the next 24 hours, eventually losing its grip on our weather as it heads out to sea, allowing unsettled weather to return.

This unsettled weather is seen nicely on the National Radar Mosaic, which shows precipitation increasing in areal coverage from the Central Plains eastward to the Tennessee and Ohio Valleys Thursday morning. Much of the precipitation is focused to the north of a stationary frontal boundary draped west to east from low pressure over North Texas to off the Southeast US coast. This frontal boundary is actually the southern remains of the same cold front that pushed through our area on Tuesday. The blossoming precipitation north of the front comes in response to the developing storm over Texas and an increasing southerly flow behind the departing east coast high pressure center interacting with the frontal boundary.

Over the next 18 to 24 hours, the low pressure center over Northern Texas will ride northeastward, dragging the stationary front back to the north in the form of a warm front along the East Coast. This front will eventually align itself parallel to the upper level steering currents over the weekend, stalling out once again and establishing a path for numerous waves of low pressure to ride northeastward from the Gulf of Mexico to just south of New England. This should lead to a prolonged period of unsettled weather beginning Friday morning, lasting through Saturday and perhaps lingering into Sunday. And along with the unsettled conditions, temperatures will be quite chilly through the period. Northeast surface winds combined with moisture added to the currently dry cool air will tend to cap temperatures in the low to mid 40s Friday, Saturday and Sunday.

Rainfall with the upcoming system will come in two main pieces, corresponding to two main surface low pressures - one on Friday and another likely arriving Saturday night, possibly lingering into Sunday morning. Fortunately, this means it won't rain for 48 hours straight. Unfortunately, we shouldn't expect much in the way of dry pleasant weather either, as in between these main waves of rain, we will see plenty of leftover low level moisture around the area in the form of scattered showers and pockets of drizzle - nice spring Cape Cod weather.

The first slug of moisture should produce several hours of steady moderate rain Friday, yielding nearly 1 inch of rain by the time it tapers down in the evening - pretty much a complete washout of a day Friday. So how much more rain comes during the weekend? Well while the follow-up rains are sure to add to the that 1-inch average total, it remains to be seen just how much more rain we squeeze out. There are still some question marks as to the exact timing, intensity and placement of the follow-up storm centers based upon the placement of the frontal boundary. Some computer guidance is more progressive in pushing the front offshore Saturday night, allowing for better conditions on Sunday as drier air pushes in to the region. However, there is more support for the idea of pushing a second storm center just south of Cape Cod Sunday afternoon, keeping showers going right through the morning, holding drier air at bay until later in the day. Either way we slice it, we've got a good soaking rain in the cards and if you haven't done so, tonight might be a good night to get some fertilizer down on your lawn.

Now while all of this is going on, it's next week's weather that COULD prove more interesting. High pressure will build in behind this weekend's storm system and set up shop well to our northeast, allowing for a long fetch of easterly flow to develop during the first half of next week. This alone should spell a period of cool, perhaps cloudy/damp weather as cool air moves *westward* and onto the coast. It's possible we are stuck in the 40s Monday through Wednesday with lots of clouds and periods of mist or drizzle. That's a tough call right now. Minimally, expect a continuation of cooler-than-average temperatures by day with the onshore wind.

BUT this potentially gray chilly weather isn't the direct concern for next week. The concern lies with this overall set up and its relation to the tides and any potential storm system that might try and sneak up the coast. Next week marks the Spring Tides - a period when we see some of our highest astronomical tides of the calendar year. If all we were to do was to add the previously mentioned onshore flow to these tides (a highly likely scenario right now), we could end up with some minor coastal flooding issues just because of the high nature of the tides. It doesn't take much of an onshore flow to through spring tides into flood. Now, throw a storm into the mix or a stronger east wind, and we've got some trouble. But is there a storm? Well it's not out of the question. It appears as though a low pressure area will develop off the Southeast U.S. coast on Monday and begin to drift northward towards the Carolinas or Mid-Atlantic by mid-week. This by itself would increase the pressure gradient and help to strengthen our surface winds, even if we stay removed from the true force of the storm. But what-if, what-if, as the European model suggests, this system really gets cranking and lifts all the way up the Eastern Seaboard to a position east of Cape Cod by Thursday or Friday?? That would be bad news...