Short Term Discussion [6/15]

Briefing

Nice day today
Showers begin late tonight west to east
Rainy period coming up along stalled boundary
Temps below normal

Radar and Satellite

Some showers moving through W. Pa and they may make their way into C. Pa later this morning. Most of the wetness remains over the Plains today.

Geocolor/Visible

We are seeing clouds trying to move into the area, but for now, we stay dry (this map will update throughout the day).

Temperatures today will feel like June

Most of the immediate Philadelphia area will see highs in the low to mid 80s. Up into the Poconos and the immediate shore points will be stuck in the 70s, perhaps a pot like Toms River breaks the 80 degree threshold.

Forecast Discussion

Current surface pressure charts show multiple areas of low pressure, one dropping in from Canada, and the other in the Plains. The one in the Plains is associated with a warm front boundary and this will slide into our area as it collides with the Canadian system. For the next several days the upper air pattern will be fighting it out over who is stronger.

NAM from this morning

Taking a look at 500mb (roughly 8000 feet), in the purple bubble in Ohio we have some shortwave energy, followed by shortwave trough energy in the Plains associated with the boundary. Then in Canada and further west over the Rockies are other disturbances.

Taking a peak at the wide view we see the root cause of the problem…

There is a strong -NAO block over Greenland! This causes a blockade and backs up the storm systems in Canada. Multiple low pressure areas that are having a difficult time advance. Towards W. Canada there is an Omega Block, another HP area that is not allowing storm systems through. Undercutting that are troughs in the W. US and Plains (in green), with another trough in Canada. This parade of troughs will move along a stalled upper air pattern, with the line of demarcation in orange.

So we see for tomorrow the beginning of a rainy pattern for the next several days. This is the NAM for early tomorrow morning around 8 AM. Most of these showers begin out towards W. Pa/W. NY later this afternoon and slowly make their way overnight through the region.

Continues through the afternoon…

And then overnight, a particularly vigorous shortwave energy along the stalled frontal boundary will bring with it frontogenesis (quick clash of airmasses) and we could actually see some strong storms overnight in the immediate Philadelphia area Sunday night into early early Monday morning.

And that will really be the theme of the week. On and off shower activity, some of it on the stronger side. Until the -NAO Greenland blocking fades later this week. The North American pattern is put on hold, and made all the worse with W. Canada ridging requiring storms to undercut it in the W. US and make their way east into the blocked pattern. The end result is several periods of rain each day.

Depending on which side of the boundary Philly ends up on will determine if it stays on the slightly above average side or slightly below average side.

Here is the NAM temperature anomaly forecast for tomorrow.

Before any warm boundary moves through, we will be slightly below average. And that may have to wait until Monday. And again, overnight Sunday into Monday storms may be on the stronger side.