A couple storm systems will impact NYC this week. The first of these could bring some thunderstorms and gusty conditions tomorrow afternoon. Later this week on Thursday, a second storm bringing steadier rain will move through. Temperatures throughout this period will be generally 5ºF below normal. Tuesday and Wednesday overnight lows could bottom out in the upper-30s.
Rest of today – mostly cloudy, with clouds diminishing later, high temperatures in the upper-50s. Overnight lows in the mid-40s.
Weather Prediction Center surface forecast for 8AM Tuesday
Tuesday – quick moving storm will push a warm front and then a strong cold front through Tuesday afternoon. Showers should begin in the afternoon and a line of thunderstorms is possible with the cold front. High temperatures around 60ºF with southwesterly flow ahead of the cold front. Overnight lows in the mid-30s.
Wednesday – the low bringing the rain and thunderstorms on Tuesday continues to strengthen. The pressure gradient will tighten around this low and bring windy conditions but with sunny skies. High temperatures cool off into the low-50s. Overnight lows in the upper-30s.
GFS 2-meter above ground level temperature anomalies for 2AM Thursday. A cold night in store for many parts of the Northeast!
Thursday– partly sunny skies with high temperatures climbing into the upper-50s. Overnight lows around 50ºF with rain developing.
An extended period of cool temperatures continues for the rest of the week into the weekend. During this period, highs will generally 10ºF below average. A weak storm passes through Friday night into Saturday bringing the chance for rain. Temperatures finally warm up to start next week though this may not last.
Rest of today – mostly sunny with high pressure building. High temperatures in the low-50s. Cold overnight lows in the mid-30s with a cool air mass in place. If skies remain clear and winds decouple overnight, we could see even colder overnight temperatures.
Weather Prediction Center surface forecast for 2AM Friday
Friday – with a cold start to the day, high temperatures will be hindered around 50ºF. Clouds increase as a low pressure center moves towards us. Rain chances increase later in the day and into the overnight. Overnight lows around 40ºF
Saturday – rain ending early, as the storm system slides east of us. High temperatures hampered by this early rain and clouds, reaching into the mid-50s. Overnight lows around 40ºF.
Climate Prediction Center temperature outlook for April 21-25, showing chances for below normal temperatures in the Northeast
Sunday– high temperatures start warming up to around 60ºF. Overnight lows will likewise warm into the upper-40s.
A powerful storm tracking over the Great Lakes that brought a deadly outbreak of severe weather and strong tornadoes to the Deep South will continue tracking northeast over the Great Lakes. A warm front and cold front associated with this storm could bring thunderstorms, though regardless, dangerously strong winds will be present. After this storm passes, this gives way to a cooling pattern with a second, weaker storm coming Wednesday. Temperatures during this period start above normal in the 60s to below normal in the low-50s.
Rest of today – a powerful surface low over tracking over the Great Lakes with minimum central pressure below 984 mb will bring a period of dangerous winds to the region. The pressure gradient between this low and high pressure over the Atlantic will be very tight, as you can see below. This will result in sustained winds easily in the 30 mph range, with stronger gusts of 60-65 mph possible due to the very strong winds aloft. Both the warm front and cold fronts of this storm could touch off some isolated elevated thunderstorms, though instability will be modest at best. High temperatures should peak in the upper-60s with robust warm air advection due to these strong winds eventually turning southwest. Overnight lows in the mid-40s as this storm pulls away.
Weather Prediction Center surface forecast for 2PM Monday
Tuesday – skies clear up overnight into the morning. Partly cloudy to mostly sunny skies should prevail with high pressure building. High temperatures in the upper-50s. Overnight lows around 40°F.
Wednesday – a second, weaker low is forecast to form over the northern Gulf of Mexico along the southerly extremes of the cold front from this first storm. This low then slides northeast along the coast. Although this second storm will pass far to the south of us, it could still bring some rain during the day. With clouds, rain, and an onshore northeasterly/easterly flow, temperatures will struggle to hit 50ºF. Overnight lows in the upper-30s.
GFS model 500 mb height anomalies for 2PM Thursday. Negative height anomalies at the 500 mb level can often translate to below normal temperatures at the surface.
Thursday– temperatures remain cool despite more sun, only reaching into the low-50s. Overnight lows around 40ºF.
We have a stormy start to the forecast period with the Storm Prediction Center putting us under a slight risk for severe weather this afternoon. Behind this storm, windy conditions will prevail Friday with the pressure gradient tightening between an incoming high pressure and the departing low. This pressure gradient eases Saturday as high pressure moves more directly overhead. Decent weather continues Sunday before another storm rolls in Monday. Above normal temperatures for Thursday in the low-60s. Temperatures drop below normal in low-50s this weekend before picking up Monday into the upper-60s.
Rest of today – lighter stratiform rain in the morning hours with a warm front moving through. This will be followed up by a possible round of strong to severe thunderstorms in the afternoon hours (most likely around 1-2PM). The primary risk for severe weather comes from the potential for damaging wind gusts, with very fast winds aloft potentially mixing down to the surface. High temperatures in the low-60s. Overnight lows around 40ºF as gusty winds bring in strong cold air advection. See this detailed forecast for more info about today.
Storm Prediction Center convective outlook for Thursday, showing us in a slight risk area for severe weather later today.
Friday – despite a high in the low-50s, strong winds around a deepening low will make it feel significantly cooler. Clouds should gradually diminish during the day. Overnight lows cool, in the upper-30s.
Weather Prediction center surface forecast for 8AM Friday. A strong low pressure cetner is indicated tracking northeast out of Maine.
Saturday – winds ease as an area of high pressure moves more directly over us. High temperatures should range in the mid-50s with plenty of sun. Overnight lows will be in the mid-40s.
Sunday– clouds increasing with high temperatures in the upper-50s. Overnight lows will warm into the low-50s.
It’s been nearly three months since my last detailed forecast, so forgive me if I’m a bit rusty. Thursday in NYC will be an active weather day. A rather complex picture will unfold, with a warm front passing early, then a triple point passing nearby, followed by a trailing cold front that could bring the potential for thunderstorms later in the afternoon. Strong winds will be in the picture, and these winds will persist (if not increasing in intensity) into Friday.
My Forecast High: 61°F | Low: 49°F | Max sustained winds: 33 mph | Total precipitation: 0.24″ – verification will come from METAR data for the period between 2AM Thursday and 2AM Friday (06Z Thursday to 06Z Friday) at LGA (LaGuardia Airport), and the KLGA Daily Climate Report.
Verification High: 58°F | Low: 44°F | Max sustained winds: 44 mph | Total precipitation: 0.26″ – this ended up being a decent forecast for the high temperature. The cooler scenario depicted by NAM ended up being correct, and siding with a more conservative high was the right call. Amazingly, I was only 0.02″ off from the precipitation total! However, in my focus on that aspect of the forecast, I neglected some basic signs about the winds and low temperatures. These two ended up being connected. Winds in the wake of the cold front were likely boosted by subsidence (sinking cold air), and these provided a boost to cold air advection, leading to the low actually occurring around midnight, as opposed to the overnight hours going into the day. This was actually apparent in the statistical guidance, but was something I failed to spot. Lesson learned: never forget to check the entire data set – and when cold fronts with convective activity swing through, consider being aggressive about the winds associated both with the storms themselves, and behind the front.
Weather Prediction Center surface forecast for 2AM Thursday
Weather Prediction Center surface forecast for 8AM Thursday
Weather Prediction Center surface forecast for 2PM Thursday
Weather Prediction Center surface forecast for 8PM Thursday
Synoptic Setup At the surface, two lows will be influencing the picture, one centered further north over Ontario, and another tracking closer to the area. Early in the forecast period, a warm front associated with secondary low pushes through. This could lead to some lighter stratiform rain due to isentropic (overrunning) lift. After this, a triple point passes just north of the area in the afternoon, and this should provide a locus for some some enhanced lift. This will be followed shortly thereafter by a trailing cold front passing through in the late afternoon hours. This cold front could trigger some thunderstorms with NAM showing some instability, though GFS isn’t as aggressive.
GFS is less bullish on showing a saturated layer at 850 mb. NAM does have wetter conditions which explains why the QPF totals are higher with this model. One thing both models agree on is the presence of strong winds at this level, anywhere from 35-50 knots. Should moisture content be better upstream, we should see effective moisture transport from this low-leve jet.
Further up in the atmosphere at 500mb, a shortwave trough attached to a closed 500 mb low over Ontario/Quebec border is forecast pivot through the region. Models are suggesting very strong positive relative vorticity associated with this feature. This should lead to ample divergence aloft and enhanced lift potentially supportive of organized convective activity. Low-mid level lapse rates due to the presence of the closed low could also be decent enough to support convection.
Finally, at the 300 mb level, a jet streak with very fast core winds in excess of 140 knots looks to set up over the Ohio Valley. We will be in the favorable left exit region of this jet streak, a set up that further favors enhanced divergence aloft. This should likewise increase lift in the atmosphere. This is reflected by SREF that shows a decent probability of moderate to strong omega over the region during the passage of this storm.
NAM model 850 mb relative humidity and winds valid 2PM Thursday
GFS model 500 mb height and relative vorticity valid 2PM Thursday
GFS model 300 mb height and winds valid 2PM Thursday
High Temperatures There was a large spread between NAM and GFS statistical guidance, with NAM much cooler and coming in only in the mid-50s, while GFS came in with low-60s. Given that there should be some warm air advection with southerly winds ahead of the cold front, I tend to buy more into the warmer end of the guidance envelope. However, both sets of statistical guidance also show a period of winds backing to the ESE in the afternoon which would bring a characteristically onshore flow and introduce a marine air mass. That might cut into overall high temperatures. Some limited evaporational cooling and clouds could also keep a cap on temperatures warming too much. With all this in mind, I’m going with a high temperature of 61ºF.
Low Temperatures There is likewise a big spread between GFS and NAM on low temperatures. NAM is close to climatological averages for low temperatures in the low-40s while GFS is a full 10ºF warmer. Southerly winds are indicated during most of the overnight hours seem to suggest erring on the warmer end of guidance. I think that EKDMOS 50th percentile of 49ºF seems reasonable.
GFS MOS guidance for KLGA
NAM MOS guidance for KLGA
Max Sustained Winds Both GFS and NAM indicate that a well-mixed layer will form by the late afternoon. As referenced above, winds aloft at 850 mb will be quite strong. This mixed layer should enable these strong winds to work their way down to the surface. This will be aided by any downward momentum transfer effected by falling rain. Layer mean wind analysis shows max wind speeds well above statistical guidance, and I few reasons to disagree with this, so I’m calling for max sustained winds of 29 knots, or 33 mph.
GFS forecast sounding for KLGA valid 2PM Thursday. The presence of a well mixed layer is apparent from the surface up to just above 850 mb. This should allow for strong winds at this layer to mix down to the surface, something that would be enhanced by precipitation drag effects from rain falling.
Total Precipitation There is high bust potential for total precipitation forecasts here with convective precipitation in the picture. The earlier light stratiform precipitation with the warm front probably will not result in too much overall precipitation. However, just one strong thunderstorm/heavy downpour could wreck any forecast here. The blended GFS/NAM mean is about 0.25″ and SREF probabilities for precipitation greater than this are not a lock, despite the overall synoptic picture showing decent support for good lift. SREF gradients are quite sharp going south. In addition, onshore winds that are possible could help stabilize the area by bringing in a cooler marine layer. I don’t feel confident that we’d see more than 0.25″ unless a convective burst hits KLGA head on, so I am going with 0.24″ as a conservative play.
We have above normal warmth to start the week in the mid-60s. Clouds increase Tuesday going into Wednesday as a low is forecast to form along a warm front. This brings us the first chance for rain Tuesday night into Wednesday morning. There appears to be a brief pause in rain chances before before a more potent storm passes Thursday. As pointed out by forecasters, this storm looks to be associated with a vigorous upper low that should enhance lift. Some thunderstorms could be possible with this.. Temperatures will trend lower towards end of week.
Rest of today – high pressure in control with plenty of sun, high temperatures should rise into the mid-60s with downsloping northwesterly winds. Overnight lows in the mid-40s.
Weather Prediction Center surface forecast for 8PM Tuesday
Tuesday – a warm front associated with a low tracking into the Great Lakes makes its approach. Ahead of this low, clouds will increase, though temperatures should still be able to reach into the low-60s. Overnight lows around 50°F with rain chances increasing.
Wednesday – rain early in the day as the warm front lifts through the region. High temperatures still reaching into the low-60s. There may be possible partial clearing of skies in the afternoon as we get into the warm sector behind the warm front. Overnight lows in the upper-40s.
GFS model 500 mb height, and relative vorticity valid 2PM Thursday. This model depicts a closed upper low over the Great Lakes spawning very strong vorticity (and hence divergence and lift aloft).
Thursday– a second, more powerful storm hits the region. A closed upper low over the Great Lakes will provide enhanced lift for this storm as it pushes a cold front through the area later on Thursday. High temperatures in the upper-50s. Showers and possibly thunderstorms will accompany the cold front passage. Overnight lows in the low-40s.
A retrograding low will bring increasing clouds, wind and rain to end the week. This low will be blocked from moving east until late Friday. High pressure will move in Saturday and should dry things out, and bring more sun. A weak cold front is forecast to pass through Sunday. Some rain will be possible with this frontal passage. Temperatures during this period should remain at or above normal for this period in the mid-50s.
Rest of today – increasing clouds with a low retrograding west towards the area. High temperatures in the mid-50s. Winds will pick up also as the pressure gradient builds between the retrograding low and high pressure to the west. Overnight lows should be around the mid-40s.
Friday – chances for rain, mostly in the morning hours, with high temperatures in the mid-50s under mostly cloudy skies. Rain chances will diminish as this low finally pulls off to the south. Overnight lows again in the mid-40s.
Weather Prediction center surface forecast for 2AM Friday
GFS model 500 mb height, vorticity and wind forecast valid 10AM Thursday. Note the presence of the closed upper low offshore of the Northeast, with an omega blocking pattern over the eastern Atlantic (two lows, with a ridge in between, literally looks like the Greek letter for omega)
Saturday – as high pressure moves in, we’ll see a better day with partly to perhaps mostly sunny skies and high temperatures in the upper-50s. Overnight lows will be in the mid-40s.
Sunday– a weakening cold front may bring a chance for showers, but ahead of this, temperatures will be mild in the upper-50s. Overnight lows will warm into the mid-40s.
It’ll be a cloudy start to the week with possible thunderstorms later today. Rain chances continue Tuesday with a surface low in our vicinity. Once this low moves off, our weather calms Wednesday. High pressure builds in Thursday and should bring us mostly sunny skies. High temperatures start off slightly below normal in low-50s with clouds and rain, and will warm into normal ranges in the mid-50s later on.
Rest of today – energy from an upper level low will support development of a surface low around its base. Surface troughs from this low may touch off some isolated showers and thunderstorms later this afternoon with the aid of a cold pool aloft (increasing lapse rates and increasing instability). Best chances for this activity will be north of the city. High temperatures in the mid-50s with clouds and rain. Overnight lows in the low-40s.
GOES East Geo Color satellite image. You can see the large area of cloudiness associated with the upper level low
High resolution rapid refresh simulated radar showing the possibility for some convective activity associated with a cold pool later this afternoon around 5PM
Tuesday – this surface low will help move a backdoor cold front through, bringing cool, damp, northeasterly flow to the area. With this air mass, we’re only expecting high temperatures in the upper-40s. Rain chances continue with the low in our vicinity. Overnight lows in the upper-30s.
Wednesday – the low affecting our weather to open the week finally moves off. We’ll get a dry day with diminishing clouds and high temperatures around 50°F. Overnight lows around 40°F.
Thursday– high pressure builds and brings us a mostly sunny day. High temperatures rebound into the mid-50s in response. Overnight lows in the mid-40s.
The active weather pattern we’ve seen so far this week with alternating days of sun and rain continues with two more storms coming for the end of the week into the weekend. This time around, the rainy days will outnumber the sunny ones. We will start off with a beautiful Thursday before a weaker storm impacts the area tomorrow. A more significant system will move through later Saturday into Sunday. Temperatures during this time will range around normal to above normal in the 50s.
Rest of today – high pressure will be in control of the weather today, yielding a sunny day with temperatures steadily rising into the upper-50s. Overnight lows should be around the mid-40s.
Weather Prediction Center surface forecast for 8AM Friday
Friday – clouds will build overnight into the day and by the morning hours a weak area of low pressure will be moving through the area. We can expect some light rain with this system in the morning, rather than a full day washout. Clouds will remain through the rest of the day even after the system clears and rain stops. High temperatures around 60°F. Overnight lows will be in the low-40s as a result of radiational cooling as high pressure briefly builds.
Saturday – with high pressure positioned to our north to start, northeasterly flow will keep temperatures cool in the low-50s. A stronger storm system with origins in the lee of the Rockies will be moving towards us throughout the day. A warm front will slowly move up from the south bringing a steady rain ahead of it. Overnight lows will be in the mid-40s as rain continues.
GFS 500 mb height and relative vorticity valid 8PM Sunday. Note the presence of a closed 500 mb low over Michigan and southern Ontario generating lots of positive voriticity around it. This will provide divergence and lift at the upper levels to support the storm hitting us Sunday.
Sunday– With the warm front making its way through and flow turning towards the south/southwest, temperatures should rise to around 60°F. However, rain chances are expected to continue throughout the course of the day before tapering off overnight. Overnight lows will warm into the upper-40s.
We have an active weather pattern with two storms moving through NYC this first full week of spring. A nor’easter will pass offshore today, bringing mixed precipitation early then cold rain later. We get a lull Tuesday with temperatures rebounding into the mid-50s, before a second low hits Wednesday. This will bring another round of cold rain with temps back in the mid-40s. Temperatures rebound again Thursday after this second storm.
Rest of today – some light mixed precipitation has already moved through the region this morning. A second round of more consistent, moderate precipitation should hit around lunch. High temperatures only in the mid-40s. Overnight lows around 40°F.
High resolution rapid refresh simulated radar for 1PM Monday
Weather Prediction Center surface forecast for 8PM Monday
Tuesday – the nor’easter pulls away to the northeast and we get a brief period of calm with weak high pressure building in. Partly sunny skies expected with highs in the upper-50s. Overnight lows in the low-40s with rain chances picking up towards Wednesday morning.
Wednesday – a second storm system moves up from the south. This will bring us another round of cold rain, with highs back in the mid-40s. Overnight lows around 40°F.
GFS model 500 mb height and relative vorticity valid 2PM Wednesday. A shortwave trough is evident over the Northeast, providing upper-level divergence for the second storm to hit this week.
Thursday– similar to Tuesday with things drying out. Partly sunny skies with high temperatures in the mid-50s. Overnight lows in the mid-40s.
