Disc: This forecast will be quite different from many you have been reading the past few days. It now appears there will be very minor effects from this coastal storm west of I-91. New London County may very well still get a decent storm, but the rest of the state, especially west of I 91, should see very little.
Currently: Low pressure analyzed fairly far east of the benchmark. High pressure extends from Quebec and New Brunswick, Canada, down into Central PA. It is that little extension of the high pressure down into PA that is killing the chances of this nor'easter extending further west. Synoptically, that is not where you want high pressure to get a big storm, especially not for western New England.
Tonight: We'll divide tonight's forecast into three groups: Western CT, I 91 corridor and nearby locales, and Eastern CT. For Western CT, other than a rogue light shower, expect no precipitation tonight. For the I 91 corridor, a period of light rain will continue for the first half of the night. For Eastern CT, rain will fall heavy at times the first half of the night, then conditions should improve. Even out here, I'll improve the weather tonight and make tomorrow dry. See below. As for temperatures, I am going to go with the warmer guidance and maybe even a degree or two warmer than that. Here is the reasoning: for the Western half of the state, no rain is falling and the MOS is "falsely cooled" by falling rain. In Eastern CT, skies will be cloudy and after the rain ends, temperatures will likely rise a couple degrees and then not fall much with a cloudy night. This results in going warmer than guidance nearly everywhere. Low temperatures should range from the upper 40s to near 50- fairly uniform and with no real "cool areas" or "warm areas". Winds will also be an issue for parts of the area. Expect gusts up to 50 MPH in SE CT, closer to the sfc low. For the rest of southern CT, expect gusts from 35 to 45 MPH, highest east. Winds could also gust to 35 MPH in NE CT. The NW Hills should see little impact at all from winds.
Tomorrow: With that high pressure continuing to nose in and low pressure already well east of progged, the low will continue to drift slowly further east. With that in mind, I have pulled all precipitation out of the state tomorrow. Winds will slowly diminish in E CT as well. Despite the fact that it won't rain, models are "cloudier" for tomorrow. I can buy this, as the low pressure system will be stacking and getting larger in geographic size. So we could see a very cloudy day tomorrow. For that reason, tomorrow will be chilly. I'll go close to the cooler guidance for highs tomorrow, and those highs should range 55 to 60.
Tomorrow Night/Saturday: Skies should gradually clear as the low pulls further away, I feel models are too cloudy, so I'll go warmer than guidance for Saturday's highs. Highs should range 60 to 65. In fact, if clouds leave earlier than expected, which is a distinct possibility in this forecaster's opinion, some portions of the CT valley may exceed 65 degrees. The air mass aloft is really not all that cold, and the cool temperatures have been caused more by clouds, rain, and NE flow with the offshore low than because of an exceptionally cold air mass,
Long term (Sunday and beyond): Some changes will be necessary for the beginning of the long term period (Sunday) as well, as a result of the faster flow. Because the coastal low will be long gone by Sunday, the cold front that goes through late in the day will be more potent. When there is a low offshore and a front approaching, there is an area of subsidence between the coastal low and the frontal precipitation, where you are too far west for the coastal low's precipitation, but the frontal precipitation weakens as it begins to absorb the coastal low. Originally, our area was progged to be in this area. However, with the coastal low now further east than originally forecast, the frontal precipitation will likely remain intact. This results in significant changes to Sunday's forecast. I have made the day much cloudier, as clouds will increase ahead of the front. Frontal precipitation should arrive around dinner time in western sections and around 9 PM eastern sections. It should last until around midnight in the west and 3 AM in the east. In fact, there could be a period of very heavy rainfall associated with this front. There's even a slight chance of thunderstorms, especially in western CT. With clouds arriving, temperatures will also be lower than expected originally. I went a couple degrees below current guidance, to try and "catch up" to current trends. High temperatures should generally be in the mid 60s.
Monday and Tuesday should feature fair weather. The full effects of the cold air advection won't really be felt until Tuesday. Therefore Monday's temperatures will be warmer than Tuesday's, but I think the GFS guidance is 2-5 degrees too warm. Therefore, look for highs in the mid to upper 60s on Monday and near 60 on Tuesday, except 60 to 65 in the CT valley.
The next frontal system that will cause precipitation in our area will be later on Wednesday. Precipitation should overspread the state from west to east during the afternoon hours and end during the evening. Once again, there are decent dynamics associated with this system, so there is a chance of thunderstorms as well. Guidance looks reasonable from this far out, and only minor modifications were made. Highs should generally be 60 to 65.
Expect fair weather Thursday behind the front. Models typically do not pick up well on cold air advection in the longer ranges, and that could be happening here as well, so I went a couple degrees below guidance on Thursday. Highs should be within a few degrees of 60.
I haven't had much time to look at the long range, with all the changes that were required to the short and medium ranges. But from what I have seen, it appears that we will see weather very typical of "transition season" in Southern New England- that is to say that we will have warm days and cool shots, with rain marking our frontal passages. In the coming weeks, I'll take more of a look into what the upcoming winter may hold.
Now, let's take a graphical look at systems that could affect the region. I am going to show a map for Friday. Even though I do not anticipate any precipitation to affect the state on Friday, I wanted to show the coastal low and where it's going to be. You can see from this map that the low is now far enough offshore that only far Eastern New England gets any appreciable precipitation.
Currently: Low pressure analyzed fairly far east of the benchmark. High pressure extends from Quebec and New Brunswick, Canada, down into Central PA. It is that little extension of the high pressure down into PA that is killing the chances of this nor'easter extending further west. Synoptically, that is not where you want high pressure to get a big storm, especially not for western New England.
Tonight: We'll divide tonight's forecast into three groups: Western CT, I 91 corridor and nearby locales, and Eastern CT. For Western CT, other than a rogue light shower, expect no precipitation tonight. For the I 91 corridor, a period of light rain will continue for the first half of the night. For Eastern CT, rain will fall heavy at times the first half of the night, then conditions should improve. Even out here, I'll improve the weather tonight and make tomorrow dry. See below. As for temperatures, I am going to go with the warmer guidance and maybe even a degree or two warmer than that. Here is the reasoning: for the Western half of the state, no rain is falling and the MOS is "falsely cooled" by falling rain. In Eastern CT, skies will be cloudy and after the rain ends, temperatures will likely rise a couple degrees and then not fall much with a cloudy night. This results in going warmer than guidance nearly everywhere. Low temperatures should range from the upper 40s to near 50- fairly uniform and with no real "cool areas" or "warm areas". Winds will also be an issue for parts of the area. Expect gusts up to 50 MPH in SE CT, closer to the sfc low. For the rest of southern CT, expect gusts from 35 to 45 MPH, highest east. Winds could also gust to 35 MPH in NE CT. The NW Hills should see little impact at all from winds.
Tomorrow: With that high pressure continuing to nose in and low pressure already well east of progged, the low will continue to drift slowly further east. With that in mind, I have pulled all precipitation out of the state tomorrow. Winds will slowly diminish in E CT as well. Despite the fact that it won't rain, models are "cloudier" for tomorrow. I can buy this, as the low pressure system will be stacking and getting larger in geographic size. So we could see a very cloudy day tomorrow. For that reason, tomorrow will be chilly. I'll go close to the cooler guidance for highs tomorrow, and those highs should range 55 to 60.
Tomorrow Night/Saturday: Skies should gradually clear as the low pulls further away, I feel models are too cloudy, so I'll go warmer than guidance for Saturday's highs. Highs should range 60 to 65. In fact, if clouds leave earlier than expected, which is a distinct possibility in this forecaster's opinion, some portions of the CT valley may exceed 65 degrees. The air mass aloft is really not all that cold, and the cool temperatures have been caused more by clouds, rain, and NE flow with the offshore low than because of an exceptionally cold air mass,
Long term (Sunday and beyond): Some changes will be necessary for the beginning of the long term period (Sunday) as well, as a result of the faster flow. Because the coastal low will be long gone by Sunday, the cold front that goes through late in the day will be more potent. When there is a low offshore and a front approaching, there is an area of subsidence between the coastal low and the frontal precipitation, where you are too far west for the coastal low's precipitation, but the frontal precipitation weakens as it begins to absorb the coastal low. Originally, our area was progged to be in this area. However, with the coastal low now further east than originally forecast, the frontal precipitation will likely remain intact. This results in significant changes to Sunday's forecast. I have made the day much cloudier, as clouds will increase ahead of the front. Frontal precipitation should arrive around dinner time in western sections and around 9 PM eastern sections. It should last until around midnight in the west and 3 AM in the east. In fact, there could be a period of very heavy rainfall associated with this front. There's even a slight chance of thunderstorms, especially in western CT. With clouds arriving, temperatures will also be lower than expected originally. I went a couple degrees below current guidance, to try and "catch up" to current trends. High temperatures should generally be in the mid 60s.
Monday and Tuesday should feature fair weather. The full effects of the cold air advection won't really be felt until Tuesday. Therefore Monday's temperatures will be warmer than Tuesday's, but I think the GFS guidance is 2-5 degrees too warm. Therefore, look for highs in the mid to upper 60s on Monday and near 60 on Tuesday, except 60 to 65 in the CT valley.
The next frontal system that will cause precipitation in our area will be later on Wednesday. Precipitation should overspread the state from west to east during the afternoon hours and end during the evening. Once again, there are decent dynamics associated with this system, so there is a chance of thunderstorms as well. Guidance looks reasonable from this far out, and only minor modifications were made. Highs should generally be 60 to 65.
Expect fair weather Thursday behind the front. Models typically do not pick up well on cold air advection in the longer ranges, and that could be happening here as well, so I went a couple degrees below guidance on Thursday. Highs should be within a few degrees of 60.
I haven't had much time to look at the long range, with all the changes that were required to the short and medium ranges. But from what I have seen, it appears that we will see weather very typical of "transition season" in Southern New England- that is to say that we will have warm days and cool shots, with rain marking our frontal passages. In the coming weeks, I'll take more of a look into what the upcoming winter may hold.
Now, let's take a graphical look at systems that could affect the region. I am going to show a map for Friday. Even though I do not anticipate any precipitation to affect the state on Friday, I wanted to show the coastal low and where it's going to be. You can see from this map that the low is now far enough offshore that only far Eastern New England gets any appreciable precipitation.
Finally, let's take a look at the front expected to approach the region later on Sunday. It is important to note the changes here, as this was originally progged to be a dry frontal passage. Now, in the absence of the coastal storm, there is nothing to rob the moisture from the cold front, and we'll get an active frontal passage.
Anyway, that's all for now, I'll see you next week!
-GP!
-GP!
