NY NJ PA Weather Forecasts

The digging trough over the eastern two-thirds of the nation is producing several areas of potential severe weather across the country.  

Over the eastern Great Lakes, an upper low will move into the Great Lakes with a strong cold front at the surface focusing strong to severe thunderstorms over the eastern Great Lakes.  The disturbances associated with the upper low will produce strong wind shear over the region combined with significant lifting.  The strongest thunderstorms will be capable of tornadoes, large hail, wind gusts exceeding 60 mph, frequent lightning, and heavy downpours.  

An old cold front over southern Florida will enhance lifting, which will support strong to severe thunderstorms.  The cold front will support some weak vertical directional wind shear, but any tornado will be isolated in nature.  The main threat from these thunderstorms will be large hail, frequent cloud to ground lightning, and very heavy downpour.  

The cold front over the eastern Great Lakes will extend southwestward into the Central Plains.  There, a developing area of low pressure over Oklahoma and a warm front driving towards northeastern Oklahoma will support strong isentropic lifting.  The isentropic lifting will enhance showers and thunderstorms over southern Kansas and northern Oklahoma.  The main threat from the thunderstorms will be the very heavy rain, which may lead to localized flooding of small streams and rivers.

Finally, the combination of up slope winds and a weak disturbance over the Northwest will lead to strong to severe thunderstorms over Montana and Idaho.  These thunderstorms will be capable of large hail, very heavy downpours, and frequent lightning.

Okay, local forecast discussion is done and ready to be viewed.  While I’m typing here and listening to one of the many Olympic events (I didn’t realize woman’s soccer was so violent), I want to quickly touch upon the thunderstorms from yesterday.  

So what happened?  Well, there were several factors at play yesterday.  First, the combination of the cold air aloft and the sun warming the lower atmosphere, lead to thermal mixing.  This destabilized the atmosphere, and allowed for the environment for showers and thunderstorms to develop.  Next, a disturbance took a slightly more southern track than expected, which lead to the enhancement of showers and thunderstorms.  Then, BAM, showers and thunderstorms.  Some nasty one’s too with some reports of hail, strong wind gusts, and heavy downpours as seen in the post below.  

So although I think the threat for showers and thunderstorms are low, I’m not ruling them out with all of these weak disturbances rotating around the region.  This is what I mean by an active pattern, but not a complete wash out.  So if you are going out today, beware of those stray showers and thunderstorms between 2 PM and 5 PM.

Here are some of the thoughts I’ll cover in the technical forecast discussion, after my protein shake.

1. Disturbances everywhere.

2. To close or not to close, that’s part of the question.

3. Trough remains?

The thunderstorms that developed yesterday was a direct result to the strength and depth of the cold air aloft at 500 MB and a passing disturbance rotating around the base of the trough.  The thunderstorms quickly developed, moved northwest to southeast, and produced very heavy downpours, small hail, and strong wind gusts.  

The following are official local storm reports from the National Weather Service:

0257 PM     TSTM WND GST     ALLENTOWN               40.60N 75.48W

08/08/2008  M32.00 MPH       LEHIGH             PA   ASOS

            A 32 MPH THUNDERSTORM WIND GUST WAS MEASURED AT THE

            LEHIGH VALLEY INTERNATIONAL AIRPORT.

0350 PM     TSTM WND GST     DOYLESTOWN              40.31N 75.13W

08/08/2008  M32.00 MPH       BUCKS              PA   ASOS

            A 32 MPH THUNDERSTORM WIND GUST WAS MEASURED AT THE

            DOYLESTOWN AIRPORT.

0423 PM     TSTM WND GST     PHILADELPHIA            40.01N 75.13W

08/08/2008  M32.00 MPH       PHILADELPHIA       PA   OFFICIAL NWS OBS

            A 32 MPH THUNDERSTORM WIND GUST WAS MEASURED AT THE

            PHILADELPHIA INTERNATIONAL AIRPORT.

0425 PM     HAIL             TRENTON                 40.22N 74.76W

08/08/2008  E0.25 INCH       MERCER             NJ   PUBLIC

            HAIL JUST UNDER THE SIZE OF PEAS WAS REPORTED IN TRENTON.

0430 PM     HAIL             EWING                   40.27N 74.80W

08/08/2008  M0.25 INCH       MERCER             NJ   TRAINED SPOTTER

            PEA SIZE HAIL REPORTED IN EWING.

0155 PM     HAIL             KINGSTON                41.93N 74.00W

08/08/2008  E0.75 INCH       ULSTER             NY   TRAINED SPOTTER