Disc: a very active pattern is set to take hold on the area. One of the biggest questions will be temperatures, for two reasons. First, for much of the forecast period, the air mass is marginal, so we'd need a perfect track and a strong storm to get snow,. Secondly, there is uncertainty regarding temperatures in the long term, because of model disagreement.
Currently: High pressure extended from near the NJ shore to off of Nova Scotia. This high pressure area was keeping fair weather over the area. Since the high is about to move offshore, a gradual warming trend has commenced.
Tonight: Guidance is in good agreement. With a bit of a battle between radiational cooling and warm air advection, I prefer taking a guidance split. There will be a wide range of temperatures tonight, due to radiational cooling. Lows will range from the upper teens up north to near 30 along the south coast.
Tomorrow: With an onshore flow developing and becoming deep layered ahead of our next storm as the day wears on, I prefer the cooler guidance (GFS based) for tomorrow's highs. Expect highs in the mid to upper 40s, with the cooler readings along the south coast. Otherwise, we'll call it a mix of sun and clouds and a nice day for the time of year.
Tomorrow night/Sat: A large storm system will affect the area. This storm is loaded with moisture. However, because of its track generally along the Delaware River watershed, I would not expect frozen precipitation in the area. The time of precipitation arrival will range from mid-morning west, to mid-afternoon east. Because precipitation will be arriving after temperatures have had a chance to warm up some after overnight lows, I do not even expect any freezing rain in the coldest locations. Rain could come down heavy at times. With partially-frozen ground, flooding could become a concern. As far as temperatures, I'll split the difference between the cooler NAM and warmer GFS temperatures, but with a hedge toward the warmer numbers, as I don't see any real cold air damming. Therefore, expect highs generally in the low 40s, with a few mid 40s possible along the I 91 corridor. Rain ends from west to east from 6PM to midnight Saturday night.
Long Term (Sunday and beyond): For Sunday, a few snow flurries are possible as some moisture rotates around the departing low. However, since no measurable precipitation is expected, I prefer to leave them out of the forecast for now. As usual, in a cold air advection regime, guidance looks too warm. However, this time the cold air advection is weak. So I'll only chop a couple degrees off the guidance. Expect high temperatures generally in the 40 to 45 degree range.
The rest of the long term looks quiet, at least as far as the range of this operational forecast. The only threat of any precipitation is a passing flurry or two Monday. Again, with no measurable precipitation expected, I can leave it out of the forecast.
As far as temperatures for the long term, expect a trend toward colder weather as time moves on.
Monday: low 40s
Tuesday: low 40s, maybe staying in the upper 30s NW hills.
Wednesday: mid to upper 30s
Thursday: low 30s.
Looking into the long range, it appears the pattern is set to feature multiple waves in a suddenly very stormy pattern. The air mass may be just cold enough for wintry weather if the storms are strong enough and follow a perfect track. Some of the modeling is now advertising the idea that troughiness near Alaska may begin to break down in the long term, which would break off pieces of the very cold air that is over that region, and point them at our area. However, there is still not much agreement yet, so I do not want to bite too hard on any one solution yet.
Now, let's take a graphical look at systems slated to affect the area in the upcoming week. Note that since there really is only one system and no extreme temperatures, I will only post one map today- from Saturday, to show that storm. You can see from this mao, that there are two lows- one near Cleveland, and one near Philadelphia, and very hevay rain moving into the region. Although the storm may not last that long, there is a lot of moisture getting ready to affect the area!
