NY NJ PA Weather Forecasts

Today’s Technical Forecast Discussion

10/22/08  7:40 AM

TODAY THROUGH WEDNESDAY:

The forecast area will be in between two strong storms for the next 66 hours, which means strong high pressure will move over the forecast area.  Strong convergence and confluence at 500 MB over eastern Ontario and western Quebec will support a strengthening Canadian high pressure over the forecast area.  

Winds will slowly decrease through today as the pressure gradient weakens, however with 850 MB temperatures falling below 0°C for the next 36 hours, expect cool conditions to continue.  Temperatures will continue to run around 5 degrees below normal for highs this afternoon and many locations will fall into the 30’s tonight.  

The high pressure system will move over the forecast area on Thursday and Friday, producing light and variable winds along with very cool conditions through the period.  Although 850 MB temperatures will be slightly warmer, the combination of clear skies, light winds, and low humidity will allow for temperatures to fall into the 20’s and 30’s throughout the forecast area on Friday morning.  

Meanwhile, a strong upper low will continue to deepen over the Mississippi Valley.  This upper low will produce a strong area of low pressure that will track from the Gulf Coast to the Tennessee Valley by Friday evening.  This low pressure will have plenty of moisture available from the Gulf of Mexico, Pacific, and eventually the tropical Atlantic.

SATURDAY THROUGH TUESDAY:

The pattern will continue to be highly amplified through this period.  The strong upper low over the Tennessee Valley will begin to fall under the influence and phase with the northern branch of the Polar jet stream.  This will produce strong ascent along the coastal plain, which will support heavy rainfall over the forecast area Saturday night through Sunday morning.  The surface low pressure will track from Tennessee to Ohio and then towards the central Hudson Valley through this period.  

This storm will result in an impressive negative NAO omega structure over the western Atlantic, Greenland, and eastern Canada; which will lead to a surge of cold Polar air into the forecast area.  By Sunday afternoon and evening, temperatures will quickly fall into the 30’s and 40’s.  

The pattern becomes very interesting on Monday evening and Tuesday.  As heights continue to fall and pack along the coast, a strong disturbance will round the trough on Monday night.  There is a high potential for coastal cyclogenesis over the coastal waters of the forecast area due to a strong thermal gradient coupled with significant divergence aloft.  Given the falling temperatures, which I think the model guidance is having a difficult time handling, I think there is potential for some areas over the interior like the central Hudson Valley, interior Connecticut, and northeastern Pennsylvania to get a minor snow accumulation out of this low pressure system on Tuesday morning.  This situation will have to be watched carefully.  

The pattern will eventually relax, but not before the forecast area will have a very cold end to the month of October.  Winter months tends to remember what happens in October and note the strong blocking that has developed this month and the trends of the NAO, AO, and EPO as we head towards Halloween.