If this were December, we’d have quite an interesting setup tomorrow. Sadly, it’s the end of July which means that instead of a fascinating concoction of rain, sleet, snow, and ice, we will be experiencing a dull, cool, drizzly, cloudy, showery day. Low pressure to the west will try to sling some tropical moisture our way but dry Canadian high pressure will be playing goalie and doing a fairly job blocking any shots of heavy rain thrown our way. The end result will be a day where conditions will vary greatly depending on location with the nicest (least dreary?) weather north and west and the worst (least nice) weather south and west.
A weak area of low pressure is currently drifting NE out of the Ohio Valley and into western PA. A warm front extends out ahead of it into Southern New England while a cold front trails it into the Midwest. Most importantly for our forecast is the high to the north. That high will constantly feed cool, dry air into the region as tropical moisture tries to stream north (as I said, if only it was December!). If upper level winds were strong enough and the flow amplified (wavy) enough, it might not matter but a look at this morning’s upper air analysis reveals why our chances for a super soaking are super low (if not zero).
Winds aloft over North America are still generally blowing out of the WNW. This is slowly changing as a disturbance drops south into the Pacific NW (that disturbance (red line) may bring showers and storms next weekend) but for now, our disturbance for tomorrow (blue line) still has little room to amplify and move north. The lack of strong upper level forcing means that the dry high pressure over northern Maine will likely win the day and prevent any steady, heavy rain from impacting Northern New England (southern New England has a better chance at heavier showers/storms as they are closer to the moisture). That doesn’t mean that you’re good to go the beach though, we likely do see at least some rain.
This map is valid at 10 AM tomorrow morning and is showing light rain/drizzle over SW ME and most of NH with heavier rain towards SW SNE and the Mid Atlantic states. Drizzle/light rain and fog are likely to be the name of the game tomorrow as onshore flow develops in between the high to the north and the low to the south/west. Aside from lots of drizzle/light rain, not a lot is expected to happen outside of southern NH and perhaps York County Maine. In that area, pockets of heavier rain are likely with a rumble or two of thunder possible. In terms of total rainfall amounts, a general .1 to .25″ is likely SW of the black line. NE of the black line, lesser amounts are likely with many far northern areas getting little or nothing in terms of rainfall. Some pockets of a half inch are possible across SW NH with up to .75″ possible if any downpours develop and decide not to move for a while. While this rain is better than nothing, we will need something a lot bigger to erase our 3-6″+ deficit and the accompanying moderate/severe drought conditions across SW areas.
The best way to get that rainfall in the summer would be through a tropical system of some sort. There are a couple weak disturbances down in the tropics that I am keeping an eye on but it is highly unlikely we see any tropical drought easing in the next 10 days.
Our next chance for rain will arrive next weekend when the disturbance over the Pacific NW moves across Canada and joins up with the remains of a storm currently south of Alaska. I’ll be watching that this week and will have more updates as we get closer.
I’ll have a morning update tomorrow but will be heading to Boston for much of the afternoon and thus won’t have time for an evening update.