Apr 19, 2015 7:38 PM
FLOOD WATCH FOR NH FROM 8PM MONDAY THROUGH 8AM WEDNESDAY for expected rainfall amounts of 1 - 2.5 inches. ALSO A COASTAL FLOOD WARNING WILL BE IN EFFECT FROM 11PM MONDAY UNTIL 3AM TUESDAY for the 1:21am Tuesday hi tide cycle which may result in minor coastal flooding or splashover on shore roads resulting from strong easterly winds and tidal surge due to the storm center.
Marathon Monday will start off cloudy, cool and dry. By midday showers will begin to develop then turn into a steadier rain for later in the afternoon and evening along with an increasing easterly wind at 15-25mph and gusts of 30-35mph.. A deep upper low will be shifting towards the Great Lakes, helping to steer this rain right up into the Northeast along with a warm front. Timing is everything. If you're running in the marathon...the sooner you can finish the better off you will be weather-wise, because conditions will be going downhill in the late afternoon.
Throughout New Hampshire, raw easterly winds will become rather gusty during the day. The inclement conditions will help keep temperatures in the 40s to near 50. Afternoon showers will turn to a steadier rain that will become heavier Monday night through early Tuesday. During Tuesday morning, another wave of low pressure will be developing on a cold front which will track through Southern New England. As this passes by the rain will taper to showers and taper off for the afternoon. Rainfall totals look to be on the order of 1 - 2.5 inches and that combined with runoff from snowmelt could cause rivers & streams to rise to bank full or possible begin to overflow in the typical springtime flood prone areas.
An Upper level low over the Great Lakes will be shifting east for most of the week. This will keep temperatures seasonally cool, along with providing periodic instability showers almost every day as pieces of energy rotate around in the upper level flow. Temperatures will be cool enough in the mountains for even a few snow showers Monday and again Thursday.
Beyond this the long range forecast is not looking good. It appears that a typical springtime pattern will be setting up which means an upper level Low will cut off from the main flow in the jet stream over southeast Quebec province for about 10 days. That in turn will send plenty of cool air our way along with several days of unsettled conditions, meaning rain or showers will become an almost daily threat through the end of the month as spokes of energy pinwheel around this stalled system.
Bill Gile | Meteorologist
New Hampshire One News