Thursday will probably end up being the best day of the week. High pressure will be in control from most of the period allowing for a sunny day with seasonable temperatures. Winds may be stiff overnight as well as late Thursday night into Friday. Rain associated with a low pressure system moving in will hold off until Friday.

My Forecast
High: 50°F | Low: 38°F | Max sustained winds: 20 mph | Total precipitation: 0.00″ – verification will come from METAR data for the period between 1AM Thursday and 1AM Friday (06Z Thursday to 06Z Friday) at LGA (LaGuardia Airport), and the KLGA Daily Climate Report.

Verification
High: 53°F | Low: 39°F | Max sustained winds: 14 mph | Total precipitation: 0.00″ – high temperatures ended up being a bit warmer than expected, more towards the EKDMOS 90th percentile range. I think this had to do with the fact that overnight lows were warmer (did a good job edging up on that), and because northwesterly winds backing to the west introduced an element of downsloping. Compressional warming from this was not offset by any other temperature advection, and allowed for temperatures to hit exactly the average high for this time of year. The other aspect I missed on was max wind speed. Here, looking at surface analyses from yesterday compared to the forecast models, there was a larger distance between the center of high pressure and the departing coastal low, leading to a weaker than expected pressure gradient early. The fastest winds ended up being clocked from the southwest as a result, ahead of the approaching cold front.

Synoptic Set Up
The forecast period starts with a north-south elongated high pressure over much of the Eastern US, centered over the Ohio Valley. The coastal low that impacted the area Monday is still forecast to linger southeast of Nova Scotia. A decent pressure gradient will be in place at the beginning of the forecast period as a result (high pressure measuring ~1025 mb, low ~998 mb). An approaching low pressure center will travel northeast from the Midwest across the Great Lakes into Southwestern Quebec during the forecast period. The low will continue intensifying and will erode the northern part of the high pressure center. Precipitation associated with this low won’t reach NYC until Friday, though. The primary influence of this low for the forecast period will be in shifting winds from the northwest to the southwest.

Above the surface, at 850 mb winds are forecast to start off northerly, between 20-25 knots. Wind speeds ease as they continue backing from north to west, then pick up in intensity to 30 knots from the southwest. Dry air, though moistening, will prevail at the 850 mb level throughout the forecast period. At 500 mb, slight ridging takes place during the day, then increased vorticity starts to pivot through ahead of the primary shortwave axis associated with the maturing surface low over the Great Lakes. Finally, at 300 mb we’ll start in the entrance region of a jet streak, then followed by a period of calm before the exit region of another jet streak approaches from the west.

• 

• 

High Temperatures
Statistical models (GFS, NAM, NBM) are good agreement, within a degree or two of 50°F. EKDMOS at 12Z similarly showed a tight band around 50°F, though this widened a bit at 18Z. 50°F is just a touch below climatological norms. I’m not seeing too many surprises here. Moisture is lacking for clouds to form until late in the period after the sun goes down. As winds shift to the southwest later in the day, they will largely parallel local isotherms so there won’t be appreciable warm air advection to look at either. I think 50°F is a good bet here.

Low Temperatures
Stiff winds from the northwest will offset relatively clear conditions in terms of radiational cooling. Cold air advection (CAA) is looking modest. While the wind direction is looking to cut at almost perpendicularly across temperature contours from cold to warmer temperatures, wind speeds aren’t going to be sustained at strong speeds for too long. I think 38°F is reasonable because statistical guidance is only a degree cooler or so, with EKDMOS showing this temperature at about the 50th percentile.

• 

• 

Max Sustained Winds
850 mb winds have two peaks and so do surface winds in EKDMOS: one early, then one late in the forecast period. I tend to concur the fastest winds will come early in the forecast period, since northwest winds are climatologically favored to produce fast high speeds. However, I also don’t see evidence to support mixing of strong winds aloft down to the surface. One wrinkle is if the pressure gradient ends up being tighter between the lows and the high pressure, as that would drive stronger than anticipated winds. 20 mph is above statistical guidance, but not that much higher.

Total Precipitation
This is the easiest part of the forecast as strong high pressure and dry air throughout most of the atmospheric column for most of the day makes it nearly impossible for precipitation to materialize.