Disc: The header sums it up thru Tuesday. Got a later start today, due to data ingest. A bitterly cold weekend will be followed/ended by the beginnings of what looks to be a classic major East Coast snowstorm. Of course, details are not perfect yet, but I will explain that further down.
Currently: Strong storm offshore and Arctic high pressure over the MS Valley will create gusty winds that will only add to the chill today into tomorrow.
Tonight: Took a couple deg off guidance, due to fresh CAA and a little radiational cooling, though winds will be up, so we won't radiate all that much. Lows generally near 10, except 0 to 5 above NW hills.
Tomorrow: Sunny, bitterly cold, and windy. Wind gusts increase to 45-50 at least for a time. NBM guidance generally accepted for temps. Highs only near 20 degrees, and it will feel much colder with strong winds!
Tomorrow Night/Sat: Tomorrow night's temps should be similar to those of tonight- another bitter night in store. Sat will recover a little, as advection becomes neutral, but still cold. Highs Sat 20-25, except upper 20s along the I 91 corridor.
Long Term: Long Term concerns revolve around the major winter storm potential, beginning Sunday night and lasting thru Tue night. It's too early for any maps or anything, but I'll go thru some details regarding the storm as of now.
First, all models are basically in agreement, except the UKMET, that this track will evolve like a classic East coast snowstorm. I will not give much weight to the UKMET at this time, since nothing really agrees with it. It also has flipped and flopped a lot with this storm and a lot this winter in general. Heaviest weight for this package is being given to the ENS and OP models minus the UKMET, since they're all in reasonable agreement. I am also discounting the UKMET because it is very, very rare for all of the "big three" (EURO/GFS/GGEM) operational models AND their ensembles to be pretty much in lock step and ALL be wrong. That said, models will likely bounce around some more until they arrive at a final solution. I did give a tiny bit of weight to the UKMET, in that I'll paint the entire state pretty much in likely POPS, but hold them at chance N of I 84. At any rate, it is going to start later N of 84, because it is a slow-moving system, so we have more time to refine the fcst up there.
As far as storm timing, as I mentioned, this is a VERY slow moving system. In SW CT, a flurry is possible any time on Sunday, with light snow/snow showers becoming more likely by dawn Monday. Steadier snow then arrives Monday afternoon and ends around midnight Monday night. However, light, accumulating snow, with a few moderate bursts, continues all day Tuesday, and even until late Tuesday night.
For NE CT, light snow arrives Mon afternoon, and quickly becomes heavier. The steadiest snow ends by dawn Tuesday, with light snow and snow showers continuing another 24 hours.
This storm has the potential to produce major (double digit) accumulations for the entire state, esp S of I 84.
Things to Watch: As with many large East Coast lows, there will likely be areas of deformation snow, where it snows very heavily, and keeps snowing over the same spot repeatedly, as well as a large dry slot. Unfortunately, these are absolutely the last things we know with these storms. We often do not know where these zones will be until the storm has already started and has a presentation on radar. We also do not know what kind of dry slot will set up. What I mean by that is, there are two types of dry slots: a "clean" dry slot, and a "dirty" dry slot. A "clean" dry slot has very little or no precipitation at all inside of it, while a "dirty" dry slot has showers inside of it, some of which could be locally heavy. In addition, this storm will likely stall, or come very close to doing so, and could even perform a bit of a loop, before heading out to sea. Where it stalls and performs this loop is critical to our sensible wx here. A stall too far S would keep the bands of snow down over SNJ and SE PA. A stall too far N would lash Boston, RI, and far NE CT. A stall further NW could bring p-type issues to the SE Coast. Right now, I am calling for all snow to keep it simple, but this is just something to watch.
Finally, some of the guidance, not all, namely the ECMWF/UKMET and EURO ENS showed a subtle shift to the south today. It could be the start of a trend. It could be a hiccup. Or it could just be a "tightening up" of the guidance, where it comes into better agreement. There won't be any way to really know about that until tonight's 00Z cycle is complete, to see where the modeling goes. But for this reason, I kept POPs north of I 84 to chance.
Winds could also be very strong, with wind gusts to at least 50 MPH and blizzard conditions possible, esp along the S coast. All of this will come into better focus as the event draws closer. Stay tuned!
As for temperatures, expect highs in the 20-25 Sunday, near 30 Monday, and around freezing on Tuesday. There will likely not be much diurnal variation on Monday and Tuesday, and depending on when/where heavier snow falls, they may follow a non-diurnal trend.
We clear out Wed behind the storm. I shaved a deg or two off guidance assuming snowcover, but I did not really spend much time fussing over temps. Highs should be somewhere near the mid 30s.
Thu clouds increase ahead of the next sys. That storm is probably a mostly rain event, but with cold air around, could certainly start as snow or a mix, esp N of 84. I cut several deg off temps on Thu due to snowcover and increasing clouds. Expect highs around freezing.
Long Range: Obviously, with all that's going on in the short and medium term, I did not really have time to dig deeply into the long range. However, the aforementioned rain storm next Fri sets the wheels in motion for what appears to be an extended period of intense winter, w/many chances for coastal storms and Arctic blasts. Let's just leave it at that for now...
Since the fcst is really focused around one event this time, I'll post the GFS and GGEM models valid at the same time (7 PM Monday)... that seems like a good time where much of the state will be in on the action. I'll just post the maps, no commentary. GFS will be on top, GGEM on bottom. EDIT: Scratch the GGEM. It never ran on most sites today, and the Environment Canada site is a strain on the eyes. So here is the GFS:
Currently: Strong storm offshore and Arctic high pressure over the MS Valley will create gusty winds that will only add to the chill today into tomorrow.
Tonight: Took a couple deg off guidance, due to fresh CAA and a little radiational cooling, though winds will be up, so we won't radiate all that much. Lows generally near 10, except 0 to 5 above NW hills.
Tomorrow: Sunny, bitterly cold, and windy. Wind gusts increase to 45-50 at least for a time. NBM guidance generally accepted for temps. Highs only near 20 degrees, and it will feel much colder with strong winds!
Tomorrow Night/Sat: Tomorrow night's temps should be similar to those of tonight- another bitter night in store. Sat will recover a little, as advection becomes neutral, but still cold. Highs Sat 20-25, except upper 20s along the I 91 corridor.
Long Term: Long Term concerns revolve around the major winter storm potential, beginning Sunday night and lasting thru Tue night. It's too early for any maps or anything, but I'll go thru some details regarding the storm as of now.
First, all models are basically in agreement, except the UKMET, that this track will evolve like a classic East coast snowstorm. I will not give much weight to the UKMET at this time, since nothing really agrees with it. It also has flipped and flopped a lot with this storm and a lot this winter in general. Heaviest weight for this package is being given to the ENS and OP models minus the UKMET, since they're all in reasonable agreement. I am also discounting the UKMET because it is very, very rare for all of the "big three" (EURO/GFS/GGEM) operational models AND their ensembles to be pretty much in lock step and ALL be wrong. That said, models will likely bounce around some more until they arrive at a final solution. I did give a tiny bit of weight to the UKMET, in that I'll paint the entire state pretty much in likely POPS, but hold them at chance N of I 84. At any rate, it is going to start later N of 84, because it is a slow-moving system, so we have more time to refine the fcst up there.
As far as storm timing, as I mentioned, this is a VERY slow moving system. In SW CT, a flurry is possible any time on Sunday, with light snow/snow showers becoming more likely by dawn Monday. Steadier snow then arrives Monday afternoon and ends around midnight Monday night. However, light, accumulating snow, with a few moderate bursts, continues all day Tuesday, and even until late Tuesday night.
For NE CT, light snow arrives Mon afternoon, and quickly becomes heavier. The steadiest snow ends by dawn Tuesday, with light snow and snow showers continuing another 24 hours.
This storm has the potential to produce major (double digit) accumulations for the entire state, esp S of I 84.
Things to Watch: As with many large East Coast lows, there will likely be areas of deformation snow, where it snows very heavily, and keeps snowing over the same spot repeatedly, as well as a large dry slot. Unfortunately, these are absolutely the last things we know with these storms. We often do not know where these zones will be until the storm has already started and has a presentation on radar. We also do not know what kind of dry slot will set up. What I mean by that is, there are two types of dry slots: a "clean" dry slot, and a "dirty" dry slot. A "clean" dry slot has very little or no precipitation at all inside of it, while a "dirty" dry slot has showers inside of it, some of which could be locally heavy. In addition, this storm will likely stall, or come very close to doing so, and could even perform a bit of a loop, before heading out to sea. Where it stalls and performs this loop is critical to our sensible wx here. A stall too far S would keep the bands of snow down over SNJ and SE PA. A stall too far N would lash Boston, RI, and far NE CT. A stall further NW could bring p-type issues to the SE Coast. Right now, I am calling for all snow to keep it simple, but this is just something to watch.
Finally, some of the guidance, not all, namely the ECMWF/UKMET and EURO ENS showed a subtle shift to the south today. It could be the start of a trend. It could be a hiccup. Or it could just be a "tightening up" of the guidance, where it comes into better agreement. There won't be any way to really know about that until tonight's 00Z cycle is complete, to see where the modeling goes. But for this reason, I kept POPs north of I 84 to chance.
Winds could also be very strong, with wind gusts to at least 50 MPH and blizzard conditions possible, esp along the S coast. All of this will come into better focus as the event draws closer. Stay tuned!
As for temperatures, expect highs in the 20-25 Sunday, near 30 Monday, and around freezing on Tuesday. There will likely not be much diurnal variation on Monday and Tuesday, and depending on when/where heavier snow falls, they may follow a non-diurnal trend.
We clear out Wed behind the storm. I shaved a deg or two off guidance assuming snowcover, but I did not really spend much time fussing over temps. Highs should be somewhere near the mid 30s.
Thu clouds increase ahead of the next sys. That storm is probably a mostly rain event, but with cold air around, could certainly start as snow or a mix, esp N of 84. I cut several deg off temps on Thu due to snowcover and increasing clouds. Expect highs around freezing.
Long Range: Obviously, with all that's going on in the short and medium term, I did not really have time to dig deeply into the long range. However, the aforementioned rain storm next Fri sets the wheels in motion for what appears to be an extended period of intense winter, w/many chances for coastal storms and Arctic blasts. Let's just leave it at that for now...
Since the fcst is really focused around one event this time, I'll post the GFS and GGEM models valid at the same time (7 PM Monday)... that seems like a good time where much of the state will be in on the action. I'll just post the maps, no commentary. GFS will be on top, GGEM on bottom. EDIT: Scratch the GGEM. It never ran on most sites today, and the Environment Canada site is a strain on the eyes. So here is the GFS:
Anyway, that's all for now. I'll see you next week, or possibly earlier if conditions warrant!
-GP!
-GP!
