Good evening from SCW!
 
After our first summer-like day on Monday, Spring has finally found its way to Connecticut, with comfortable temperatures, low humidity, and plenty of sunshine. Of course the question you’re all asking is “will this hold on for Memorial Day Weekend?” and I’m happy to tell you that by and large it will. The “unofficial start of summer” looks like it’ll actually feel like summer this year!
 
Thursday-Friday
 
Tomorrow will be a bit cloudier compared to the last couple of days, and we’ll also see some sprinkles or scattered showers throughout the day. We’ll see shower coverage become a bit more widespread in the evening hours as a cold front passes through, but not seeing the ingredients needed to spark widespread convection at this time. Temps should hang near seasonal norms, which are right around 70.
 
For Friday, we’ll return to the sunshine and start warming up as well as highs creep into the low to mid 70s.
 
Saturday-Monday
 
Should see warmer and more humid weather for Saturday as a frontal system passes to our north. Right now Euro/GFS keep the QPF in northern New England/upstate NY but we’re still at the range where we could see a shift back south to bring showers to the area. Will carry a slight chance of precipitation to account for any southward shifts, but as of right now the odds favor a dry day and even some peeks of sunshine. Highs should be in the mid 70s.
 
On Saturday night, the front shifts south and east into our area, bringing a round of showers and possibly some thunderstorms. While some showers may linger into Sunday morning, we should dry out, and we’ll definitely warm up; 80s look like they could be in the cards by Sunday afternoon away from the immediate coastline. If that’s a bit too hot for you, Monday will be your winner; mid 70s and almost full sunshine is pretty unbeatable for Memorial Day. Get the BBQ and beach plans ready!
 
Here’s a look at afternoon temps on the GFS for Saturday, Sunday, and Monday. Nice!

​Tuesday-Wednesday
 
Another frontal system looks to move through for the start of the workweek which would bring a period of showers to the state and cool things off a touch. Some signs in the long range that we warm up significantly towards the middle of the week; if you believe the models we’d be well into the 80s and possibly approaching 90 in the warmer spots, but you’d need a blockbuster setup to get that this early in the summer and I’m not convinced that the signal is real. Will go with lower 80s for now and keep an eye on it, but just for fun, here’s a look at forecast high temps on Wednesday from the GFS.

The Dailies
 
Thursday: A chance of showers, otherwise, mostly cloudy, with highs around 70. Chance of precipitation is 40%.
 
Friday: Mostly sunny, with highs in the low to mid 70s.

Saturday: A slight chance of showers, otherwise, partly sunny, with highs in the low to mid 70s. Chance of precipitation is 20%.
 
Sunday: A chance of showers in the morning, then becoming mostly sunny, with highs in the mid 80s. Chance of precipitation is 30%.
 
Monday: Mostly sunny, with highs in the mid 70s.
 
Tuesday: A chance of showers, otherwise, partly cloudy, with highs in the low 70s.
 
Wednesday: Partly sunny, with highs in the lower 80s.
 
Have a wonderful long weekend and thank you for reading SCW!
​
-SA

As we head into the latter part of spring, a weather pattern more typical of this time of year is about to set up across the region.  The pattern we had over the last several days which was more reminiscent of March will depart.

Currently: A "quasistationary" boundary extended from near Lake Huron to along the Long Island Sound.  This boundary will be the focal point for uncertainty regarding temperatures for a good chunk of this forecasting period.  One fortunate thing for us this time is there is dry high pressure, rather than maritime high pressure, north of this front- for now.  So we get nice dry weather instead of low clouds and drizzle.

Tonight: Not much going on and generally mostly clear skies.  Model guidance is tightly clustered, so there is no reason to diverge.  Lows should generally range 50-55.

Tomorrow: A weak frontal boundary could trigger some showers and thunderstorms later in the day.  This time around, it does appear most of the state will be warm-sectored.  However, the question this time will be whether or not there is enough moisture that everyone gets storms or if it's just widely-scattered stuff.  For now, given trends in modeling, I think south of the Merritt Parkway should see more solid precipitation, with less as you head north (unless you head about 200 miles north of our forecast area, but that's not pertinent to this discussion).  As for temperatures, the 18Z GFS numerical guidance has come in quite a bit cooler than the 12Z, and that looks to be about correct, given increasing clouds and arriving precipitation. High temperatures should be generally in the 70-75 degree range.

Tomorrow Night/Saturday: No precipitation should fall during this period (aside from leftovers from Friday afternoon's possible storms).  However, a bit of a wrinkle has arrived in the Saturday forecast.  The NAM model is showing deep marine layer that actually penetrates into much of interior New England in the form of low clouds and much lower temperatures.  As I have mentioned before, the NAM does have a tendency to overdo this.  However, the GFS also has a tendency to completely ignore this when it does, in fact, exist.  Therefore, with low confidence, I have gone for a compromise, so Saturday's highs should be in the upper 60s.

Long Term (Sunday and beyond): Temperatures: For the most part, the GFS extended range temperature guidance has been fairly accepted, with the exception of a few tweaks here and there, except for Monday and Tuesday when I've lowered GFS temperatures by a few degrees.  The GFS is running significantly warmer than all other guidance.  It should also be noted that this isn't the highest confidence forecast in history.  It isn't a case of a cut-and-dry Bermuda Ridge pumping heat into the area.  Yes, the Bermuda Ridge is there, but so is an extension of the ridge into Nova Scotia, which would imply the potential for backdoor cold fronts.  So, while I am going mostly warm in the long term, it should be noted that it is low-confidence, and if any adjustments are needed, they would probably be in a downward direction.  Now, for the aforementioned temperatures: Sunday: 70-75, Monday: upper 70s, Tuesday: near or just above 70 Wednesday: similar with temperatures near 70 for highs, and Thursday: mid to upper 70s.

As for sensible weather in the long term, right now it is my belief that the best chances for showers and thunderstorms in the long term are later Sunday and later Wednesday as a couple cold fronts move through.  A typical late spring pattern....

Looking out into the longer range, a lot of the longer range model guidance says we regress back into a trough in the east, which would result in a cooler, wetter pattern returning.  While this is a departure from some recent guidance (and this usually lowers confidence), it is also a repeat of the pattern we've been in, so this does increase confidence a bit.  All in all, I'd rate confidence in that happening at a moderate level.

Now, let's look at the Friday and Sunday systems in graphical format.  (The Wednesday potential system is a ways out yet and can be discussed more in depth in future AFDs). 

On this map, you can see the highest concentration of storms is roughly along the Merritt Parkway and adjoining SR 15 corridors.  The precipitation maxima should be around BDR-HVN-OXC.

On this map, you can see the precipitation is heaviest over the Catskill Mountains on Sunday, which makes sense in that type of setup.  However, there is still enough precipitation blanketing Connecticut, which suggests Sunday could see more widespread precipitation than tomorrow.

That's all for now! Have a great week!

​-GP!

Disc: The pattern that has been ongoing since about 8 weeks ago looks to just roll on through at least the next 10 days- frequent unsettled weather with highly variable temperatures and frequent bouts of "onshore flow".

Currently: The frontal boundary (which we could almost analyze in the same spot every day) extends from SW MI down to the Srn Delmarva.  An associated low pressure system was near Green Bay.  This has placed the state in a maritime, cool flow.

Tonight: Lots of clouds, but not much in the way of precipitation.  Models (and radar) do not particularly show drizzle well.  But tonight does not appear to be a "drizzly" night because right now the winds are up a bit.  If winds calm down, the south coast could see drizzle and fog.  This is possible in Srn Fairfield County after midnight, but for now I think it will be too patchy to really include in the forecast.  As for temperatures, we're probably at our low temperatures right now, with temperatures staying steady or slowly rising through the night.  Two things should be noted, however.  First, models tend to rush warm frontal passages.  And secondly, we are currently a few degrees colder than any model currently has.  So basically for lows, just go with whatever temperature it is right now.

Tomorrow: Tomorrow appears like the classic type of spring day where you get a period of steady rain in the morning, followed by some clearing, and then a line of showers and thunderstorms in the afternoon.  The biggest question on a day like that is how much, if any clearing, occurs.  This affects the strength and coverage of showers and thunderstorms with the cold frontal passage and of course, also affects temperatures.  I really do not have a whole lot of confidence in temperatures tomorrow.  However, the best forecast for tomorrow is to go a few degrees under guidance, since models are all showing "OV" (overcast skies) in the MOS.  This implies very little, if any, clearing.  If this is true, high temperatures stay in the 60-65 degree range, coolest along the south coast.   In addition, the morning "warm frontal rains" would be more likely in the morning.  As for afternoon convection, we'd be likely to have to rely on a weakening line heading from the west with the cold frontal passage.  This should weaken rapidly as it heads into a very stable maritime air mass.  So I think coastal and eastern locations may just see a passing shower with the cold front.  Over western and especially interior sections, scattered thunderstorms may survive, especially since the air mass will be a bit warmer.

Tomorrow Night/Saturday: Probably the easiest part of the forecast.  We clear out behind the front and Saturday turns out to be a very nice day.  It will still be a bit chilly for the time of year.  I'll go close to the cooler NAM MOS, given a fairly strong NW (cold advection) flow.  Highs should be in the lower 60s.

Long Term (Mother's Day and early next week): A complex storm system affects the region.  There are big-time model differences, with the GFS being dry for Sunday and focusing the storm on Mon-Tue.  The ECMWF is wetter Sunday.  An alternative solution, which I am favoring at this time, is that Sunday may be "mostly" dry during the day, but be dank and cloudy with areas of light rain and drizzle, then a steadier heavier rain developing later Sunday evening and continuing all day Monday.  I also tend to like the GFS' idea of continuing, at the very least, showery rains into Tuesday, since the coastal may have not pulled all the way out yet, and even if it does, there will be an upper level low around to continue at least showers.  So, having said all that, expect the bulk of the rain to fall during the day on Monday.  But Sunday will likely be drizzly and dreary.  Then expect lingering showers on Tuesday.  It should also be noted that the freezing level is unseasonably low for the time of year on Tuesday, only around 800 MB.  With a freezing level that low, it is not even out of the question to see some small hail or snow pellets with any heavier showers, especially over the NW Hills! As for temperatures in the Sun-Tue period, I'll go a couple degrees below guidance on Sunday and Monday.  Then on Tuesday, soundings show convective temperatures at levels more typical of late March.  This indicates to me that showers will be plentiful.  With cold air aloft (34F at 850!), any showers will cause temperatures to really drop.  So I have gone six to eight degrees below guidance for Tuesday! This yields highs of 60-65 Sunday, 50-55 Monday and struggling to reach 50 Tuesday!

The weather calms down a bit after Tuesday.  Wednesday should be a pleasant, albeit chilly, day for the time of year.  The next frontal system should bring at least the threat for a few showers by later Thursday.  With lingering cool 850s, I've opted to go a couple degrees below guidance Wednesday.   Convective temps are still pretty low.  This does not mean we'll get storms, but lots of puffy cumulus should form, which would put a cap on high temps.  With increasing "synoptic scale" clouds on Thursday, I've gone 3-5 degrees below guidance.  So expect high temperatures of 60 to 65 both days.  Thursday could turn out a degree or two warmer than I am forecasting if clouds hold off a bit longer.

Looking into the long range, the GFS-based guidance really wants to warm us up to summertime heat for at least a few days, perhaps a bit longer than that, in the day 10-15 time frame.  The ECMWF based products show no such thing.  Given a few facts, a) we've seen no such pattern yet, b) models tend to rush pattern changes (with the GFS-based guidance being a worse offender than the ECMWF), and c) it's still way out in time, I tend to caution jumping on this type of solution yet.  It should also be noted that even if the GFS guidance did verify, the hot weather would appear to be very transitory in nature.

Now, let's examine some of the systems slated to affect our area in graphical format.  First, let's look at tomorrow morning's warm frontal rains (which I think will be the bigger "show" in CT).  This map, valid midday tomorrow, shows steady light rain over the entire state.

Next, let's look at the coastal low slated to affect the region from Sunday through Tuesday.  You can see the low off the coast of NJ generating heavy precipitation, with one last batch poised to move through Monday night.  You can also see the precipitation gathering from the upper level low over Western PA.

That's all for now! See you next week!

​-GP!

A series of frontal systems will continue to impact the area through the weekend.  Through the weekend, expect lots of clouds and precipitation chances.  By next week, high pressure will finally build in and allow for much nicer weather.

Currently: A warm front was arced in typical cold air damming fashion from Niagara Falls to near Wallops Island.  This front will be the key to tomorrow's weather.

Tonight: Not too much change expected from where we are now  regarding temperatures.  The GFS guidance initialized 3-5 degrees too warm, so is basically discounted for tonight's forecast.  Expect temperatures pretty close to 50 degrees statewide.  Aside from some drizzle and fog, there is really no lift to produce significant precipitation tonight, so I will keep measurable precipitation out of the forecast.

Tomorrow: I may be taking a risk here, but when the forecasting gets tricky, sometimes it becomes necessary to do so.  On days like tomorrow, where you're dealing with a sharp temperature gradient along a front, the "compromise solution" almost never works out, although it usually busts by the least amount of degrees.  The NAM made a major cave to the GFS in the last run, by placing the front nearly 150 miles north of its previous run.  The GFS has been steadfast in insisting that the front will plow through the state.  I have sided with the significantly warmer GFS guidance for this reason.  Expect high temperatures in the mid 70s.  However, there still is the implied possibility that this forecast could be 10-15 degrees too warm.  Precipitation chances tomorrow are dependent on the position of the front.  If the front does in fact move through the state, there could very well be a line of showers and thunderstorms, some of which could be strong over interior sections, later in the day into the early evening.  

Tomorrow Night/Friday: Models are coming into better agreement that the front will sag back south.  The GFS had kept insisting that it would stay further north, but the latest GFS run has shifted well south.  The newest GFS actually is a very good compromise between the NAM, which tends to push these things a bit too far south, and earlier, warmer model runs, so will generally follow.  As for precipitation chances, there is ample lift for a some light rain, mainly during the morning hours.  With a fairly good consensus that the front will be south of the region by then, there will not be any instability available for thunderstorms.  High temperatures should be within a few degrees of 60, coolest along the south coast, due to onshore flow.

Long Term: Unfortunately, I do not have good news for the weekend, but don't shoot me, I'm only the meteorologist! Despite this, however, models have been slowing down with the overall progression of the frontal system and coastal low developing along the front for Saturday.  In fact, models have now slowed down enough that we may be able to salvage a dry day Saturday, although it will still be generally cloudy and on the cooler side.  As for Saturday's temperatures, with increasing clouds and a general onshore flow, I went a couple degrees cooler than the GFS-based long range guidance.  Expect highs generally in the low 60s, again cooler along the south coast, with an onshore flow expected.

Sunday does not look nice at all.  As a cold front stalls offshore, a coastal low, almost like a winter nor'easter will develop along the front.  Waves of rain, heavy at times will dominate the forecast from Saturday night all the way through Sunday night.  This could even become both a land-based flooding and coastal flood threat.  Stay tuned! As for temperatures, I feel the GFS guidance, which is not atypical at this range, is significantly too warm.  With a N-NE flow, heavy rain falling, and cool air aloft, I will shave 5-10 degrees off this guidance.  I expect Sunday to be quite chilly, with daytime temperatures staying in the low 50s!

The rest of the long term, namely Monday through Wednesday, look to feature very nice weather.  The next weather system does not look to impact the area until Thursday, and that is outside of our forecast period.  GFS guidance does not look too far off for Monday or Wednesday, but appears a solid 5 degrees too warm for Tuesday, given the upper level temperatures and the general wind flow.  Therefore, we'll be forecasting highs generally in the mid to upper 60s through that period.

The long range looks to feature more changeable weather, with a frontal system perhaps producing locally heavy rain every few days, not too atypical for the time of year.  Some of the ensemble guidance wants to produce a big-time warm up in the 12+ day range.  However, guidance often does this this time of year much like it produces Arctic outbreaks at that range in the winter.  So until that gets inside the day 8-10 period, confidence in that actually happening is pretty low.  

Now, let's take a look at a couple of systems slated to affect the area in the coming week.  First, let's take a look at the frontal system slated for tomorrow.   If you follow the wavy line that is the 1020 isobar, that's a pretty fair representation of where the warm front is located.  You can see it is through the SW part of the state, and probably has a good 50 miles or so more to move NE before it is finished.

​

Next, let's look at the coastal system for Sunday.  You can see on this map that the low is near the Chesapeake Bay and there is heavy rain over much of the northeast.  This is about as classic a setup as you can have for an all-day soaking rain in May.

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That's all for now, see you next week!

-GP!