Downhill we go!
After a beautiful and nicer day than I expected (nicer = more sun), things go downhill tonight. Rain should develop in places overnight as we enter the overrunning scenario I talked about in Sunday night's discussion. Rain should move in from the SW and W overnight as the dying cool frontal boundary to our south gets attached to a warm front and begins to inch northward. Temps tonight should drop to the upper 40's N/W of Philadelphia to low 50's in Center City to mid 50's S DE/NJ.
Tuesday is a tricky day as far as timing of warm frontal boundary and in terms of precip. The GFS is more aggressive in overrunning event and wants to kick out a quick 1/2 to 3/4 inch of rain while the NAM keeps things in perspective and goes lighter. I tend to side with the NAM as the GFS was more aggressive in bringing showers into our area today with the overunning event and that did not happen (as you can tell with the nice weather we got). It seems to continue this aggressive thinking and I just don't see enough lift from the warm front, nor is there a great enough temperature contrast from one side to another, to justify a significant overruning event. I do think it will be cloudy and the steady rain will stop once the warm front passes to our north. The warm front will lift through Philadelphia by early afternoon and into the Poconos by late afternoon and early evening but this is a not very high confidence thinking. This is November and we are dealing with an east wind north of the warm front, which is bringing in maritime air (low 50's ocean water) and with 65-70 degree air and dewpoints near 60 south of the front tomorrow, the cooler and more stable air might be a bit more stubborn in getting moved out of the way. I do think, however, the warm front will be north of us by the evening thought and Tuesday night should be pretty mild with temperatures not dropping much with a S and SW wind beginning to pick up.
Showers are possible at any time from later Tuesday night after the post-warm frontal lull as moisture from the storm system continues to get pumped into the area. The frontal passage should be early evening Wednesday (5 PM Harrisburg, 9 PM Jersey Coast) and the temperature drop behind the front will be steep as NW winds howl behind the front. We should experience off and on periods of rain during the day Wednesday with a quick burst of heavier rain and wind accompaning the frontal passage. The NCFR (narrow cold frontal rainband) will bring some very gusty winds (50kt low level jet) down to the surface, with some tree damage possible.
The GFS, above, is more aggressive with the system and tends to develop a quasi-squall line while the NAM (below) goes into more of a NCFR scenario. Given the lack of instability based on the idea of a mainly cloudy Wednesday keeping the sun at bay, the NAM makes more sense.
HOWEVER, keep in mind that any significant sunshine on Wednesday will put us in the running for a late afternoon and early evening squall line. I would not be surprised given the wind dynamics with the front and the low pressure system if we get tossed into a slight risk for severe weather on Wednesday. Temperatures for our area should be 65-70 on Wednesday, cooling down to 48-53 on Thursday. Total rainfall for the event should run near an inch for most of us, with some isolated heavier amounts north and west of the area.
Tuesday is a tricky day as far as timing of warm frontal boundary and in terms of precip. The GFS is more aggressive in overrunning event and wants to kick out a quick 1/2 to 3/4 inch of rain while the NAM keeps things in perspective and goes lighter. I tend to side with the NAM as the GFS was more aggressive in bringing showers into our area today with the overunning event and that did not happen (as you can tell with the nice weather we got). It seems to continue this aggressive thinking and I just don't see enough lift from the warm front, nor is there a great enough temperature contrast from one side to another, to justify a significant overruning event. I do think it will be cloudy and the steady rain will stop once the warm front passes to our north. The warm front will lift through Philadelphia by early afternoon and into the Poconos by late afternoon and early evening but this is a not very high confidence thinking. This is November and we are dealing with an east wind north of the warm front, which is bringing in maritime air (low 50's ocean water) and with 65-70 degree air and dewpoints near 60 south of the front tomorrow, the cooler and more stable air might be a bit more stubborn in getting moved out of the way. I do think, however, the warm front will be north of us by the evening thought and Tuesday night should be pretty mild with temperatures not dropping much with a S and SW wind beginning to pick up.
Showers are possible at any time from later Tuesday night after the post-warm frontal lull as moisture from the storm system continues to get pumped into the area. The frontal passage should be early evening Wednesday (5 PM Harrisburg, 9 PM Jersey Coast) and the temperature drop behind the front will be steep as NW winds howl behind the front. We should experience off and on periods of rain during the day Wednesday with a quick burst of heavier rain and wind accompaning the frontal passage. The NCFR (narrow cold frontal rainband) will bring some very gusty winds (50kt low level jet) down to the surface, with some tree damage possible.
The GFS, above, is more aggressive with the system and tends to develop a quasi-squall line while the NAM (below) goes into more of a NCFR scenario. Given the lack of instability based on the idea of a mainly cloudy Wednesday keeping the sun at bay, the NAM makes more sense.
HOWEVER, keep in mind that any significant sunshine on Wednesday will put us in the running for a late afternoon and early evening squall line. I would not be surprised given the wind dynamics with the front and the low pressure system if we get tossed into a slight risk for severe weather on Wednesday. Temperatures for our area should be 65-70 on Wednesday, cooling down to 48-53 on Thursday. Total rainfall for the event should run near an inch for most of us, with some isolated heavier amounts north and west of the area.
