Sunday, August 26, 2012

Forecast for Monday, August 27, 2012

A flash flood watch is in effect for Lancaster County as well as most of South-Central Pennsylvania and the Baltimore/Washington D.C. areas. An upper low across Virginia continues to meander and spin around and has ample moisture associated with it. This system should slowly move northeast. So far, most of our region has been spared from flash floods and spotty severe weather due to an area of high pressure that has come in from the northeast. This high should slowly retreat allowing for some showers and thunderstorms to enter the picture in our region for Monday. Some have not been that lucky in our region however... such as southern portions of Delaware where more than ten inches of rain has fallen over the last 24 hours. At this time, some heavier showers could push into our western areas tonight as that high pressure area begins to retreat. We will continue to watch the radar, but the heaviest thunderstorms should remain just to our southwest.

On Monday, a cold front will approach the region. On Tuesday, this cold front is expected to move through and push offshore. Ahead of the cold front will be scattered showers and thunderstorms. Some scattered heavy rainfall producing thunderstorms that may lead to localized flooding and some gusty winds are possible. Overall, expect more clouds than sun during this period. Refreshing air and clearing skies arrive for Tuesday Night and Wednesday. Temperatures should warm up by the end of the week, but with humidity still in check. During next weekend, the humidity will return and we could actually have another one of those 90 degree days!

Eventually, we may have to evaluate and change our forecast for the latter half of the seven day once the track of Issac’s remnants becomes clearer. At this time, there still remains some spread on the computer model guidance as to where the landfall will occur along the Gulf Coast. There is no doubt that the trend over the last 24 hours has been westward with more of a target centered on Louisiana. However, I would like to see the model spaghetti plots locked in on a landfall area for a solid day to boast confidence. Eastern Texas to Florida should continue to monitor the progress of this system. For us, if this trend holds, it is unlikely we would get a straight shot of heavy moisture from the actual low itself…but a cold front approaching late in the weekend could be loaded up with moisture due in part to Issac. For the first 15 days of September, all eyes will be on a few tropical waves in the Eastern Atlantic to see if they threaten interests in the Western Atlantic.

Some tornadoes are also possible this week as a result of Issac across the Southeastern United States, especially any place that falls on the eastern side of the rain bands associated with Issac.