Rain for This Weekend

Written by on January 20, 2015 in Local Forecast Discussion

Today high temperatures reached the mid to upper 60s under mostly sunny skies. Temperatures Tuesday night should drop to the lower 40s with some low-level clouds associated with a cold front that will pass through the area during the day on Wednesday. Clouds will begin to clear out by late morning as the cold front moves well offshore with high temperatures only dropping a few degrees from Tuesday’s highs.

Cold air returns as northerly flow develops on Thursday and Friday with highs in the low to mid 50s both days.

Mid and upper level trough will dig southward over the Gulf States and interact with the nearly stationary boundary over the Gulf of Mexico. This will allow cyclogenesis over the Gulf of Mexico before tracking up the east coast this weekend. A warm front will approach the area on Friday which will bring in warmer air as well as an increased chance of rain.

18Z GFS forecast for Friday.

18Z GFS forecast for Friday.

Both GFS and ECMWF have the rain reaching the area during the day on Friday and lasting into Saturday. This could be another heavy rain weekend as the ECMWF has nearly a 1″ forecast for ENC and the GFS exceeds 1″ for mainly the eastern sections of ENC and 1″ for western sections. It appears there is enough dynamics in place (ie. upper-level difluence leading┬áto strong lift as the high 700mb omega values indicates) to give the GFS some credibility here so this scenario is possible. (Note for images, the 18Z GFS is not an official forecast but is used here as an illustration for my forecast opinion).

18Z GFS for Sunday.

18Z GFS for Sunday.

The low pulls away from ENC during Saturday afternoon and deepen as it moves northeastward. Winds behind the low will from the northeast at first which will filter in more cold air for Sunday.

It is after this point that things get a little complicated.

Medium range models have been showing a vigorous “clipper” diving into the area from the northwest on Monday.

18Z GFS forecast for Monday 4pm.

18Z GFS forecast for Monday 4pm.

As the surface low reaches NC/VA, another surface low will develop off the coast and will become the parent low in this “Miller type B” system.

18Z GFS 300mb forecast for Monday/Tuesday.

18Z GFS 300mb forecast for Monday/Tuesday.

In this scenario, the surface low developing along the coast would fall between the left exit region of the southern jet streak and the right entrance of the northern jet streak potentially leading to quick deepening.

What does that mean? This is the type of situation that historically places ENC in a higher probability for wintry precipitation though not a guarantee. Here the main concern is the lack of a strong cold air damming east of the mountains which tends to lead to warmer air over ENC and as a result a liquid type precipitation. If, however, the stars were to align (or in this case the high pressure and the Appalachian Mountains) enough cold air could be in place for wintry precipitation. It is still too early for any type of forecast as model consistency has been terrible over the past couple of days and leads me with low confidence at this time. This weak setup usually doesn’t produce wintry precipitation for ENC so other factors will need to come into play before this becomes a possibility. I bring this up as early as I do so it is something that could be tracked during the week and drum up some excitement over what has been a relatively boring winter.

I will keep posting updates as things progress.

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