Unsettled Conditions (April 19-21)

Jonathan Carr
By Jonathan Carr April 18, 2019 21:57

Unsettled Conditions (April 19-21)

Discussion: We’re now in the warm sector supported by high pressure near Bermuda and a series of low pressure disturbances tracking just NW of the Appalachian Mountains into Canada. This is why non-coastal areas spiked so warm today and why tomorrow will also feel very mild. The S winds should rip fairly strong Friday as the front approaches from the W. It looks like the main storm activity is narrowing down its timing to early Saturday AM. This lessens the chance for Friday’s solar surface heating to enhance the main thunderstorm line. It could however produce pre-frontal showers and thunderstorm cells during Friday PM hours. There will still be adequate wind shear to produce severe thunderstorms overnight however. Also the surface low in W PA could help lifting as a trigger. It won’t be center of circulation pressure drops but some pressure drops nonetheless with a tight vertical gradient spanning the east coast. We also have the upper-level low centered near Ohio that will provide additional difluence/spreading in the upper levels via positive vorticity advection. When you factor this all together you have to allow the possibility for severe thunderstorms in that early Saturday AM period. At the very least a period of heavy rainfall with embedded thunderstorms. Once the main frontal activity moves E out to sea (hopefully by late Saturday morning but possibly as late as afternoon) the rest of the weekend still has an unsettled look. The upper-level low will be passing through which means cooler temperatures and possible nuisance showers at any time. The weekend is far from a washout however as dry and even sunny periods are also expected.

Friday (April 19) high temperatures should reach into the 70s for most areas. Skies should increase in cloud coverage throughout the day. Isolated-to-scattered rain showers and thunderstorms are possible especially during PM hours. Rainfall should intensify overnight as the main thunderstorm potential arrives. Winds should be breezy, likely gusty at times, out of the S. Overnight lows should fail to dip below 60 statewide.

Saturday (April 20) high temperatures should reach near-70 for most areas. Early AM hours should start rainy and stormy. Severe criteria thunderstorms are possible. Eventually the clouds should give way to sun. I wish I could tell you the exact hour but it’s too uncertain. Best I can do is a window between late-morning and afternoon. Conditions remain unsettled once the main batch of rain moves out over the ocean. That means smaller nuisance showers are possible at any time even after the sun breaks through. Winds should be breezy out of the S/SE. Overnight lows should fall to near-50.

Sunday (April 21) high temperatures should reach the mid-60s for most areas. Skies should be partly sunny with more nuisance rain showers possible at any time. Winds should be light out of the S. Overnight lows should fall into the 40s for most areas.

An early look at next week indicates seasonably-average conditions. Highs in the 60s and 70s with mostly dry and sunny conditions aside from passing spring showers. Not seeing anything special storm wise. Let’s take another look on Sunday night. Have a great weekend and please be safe! JC

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Jonathan Carr
By Jonathan Carr April 18, 2019 21:57