Weather with Bill Evans

Good Day On This Monday May 16, 2022 A strong cold front moves through the area this evening, followed by a secondary cold frontal passage on Tuesday. High pressure will briefly return on Wednesday, then a series of weak disturbances may skirt the area Thursday and Friday as a warm front slowly approaches from the southwest. The front should lift through Saturday morning. Dense fog has not been a problem over land overnight like it has been the past several nights. On night fog satellite imagery it can actually be seen eroding away from the eastern half of the area. However, with some clearing over the western half of the area, patchy radiation fog has been able to develop. The main story today is the round of severe thunderstorms expected later this afternoon and through the evening. SPC`s 06z update has nudged the "enhanced" risk east just slightly and then extended the "slight" risk eastward to the edge of the cwa. The "enhanced" risk includes the Western half of the Lower Hudson Valley and northeast NJ. In the mid-upper levels a negatively tilted trough approaches from the west, as associated surface low pressure forms and deepens as it passes to our north and west. A strong cold front extending down from the surface low will pass through the area tonight, with severe thunderstorms possible ahead of and along the front. There will be two chances at seeing severe thunderstorms today. The first will be out ahead of the cold front and will be more in the form of discrete cells. With an environment mainly north and west of NYC characterized by MLCAPE ~1500 J/kg, effective deep- layer shear ~45 kts and effective SRH 100-150 m2/s2, any discrete cells that get going could produce large hail or even an isolated tornado. With the passing of the cold front storm mode will be QLCS and damaging wind gusts will be the main threat at that time. As for timing, any discrete cells would likely develop around 1pm - 3pm. The more organized line of storms will follow, likely reaching far western portions of the cwa ~5pm, nyc by ~6pm. As the line of storms continues east it will run into a more stable airmass and likely weaken quickly, common for this time of year. Any thunderstorms will be able to produce heavy downpours as well. See hydrology section below. Highs reach the upper 70s across northeast NJ, Lower Hudson Valley and interior CT. Across NYC, coastal CT and Long Island highs will tap out in the mid 60s to low 70s. Behind the cold front, skies will clear and dewpoints drop from the low 60s to the upper 40s. Lows will be in the lower to upper 50s. On Tuesday a secondary cold front will move through at the surface while shortwave energy rotates around an upper level low in eastern Canada. A dry day is expected, with some gusty conditions in the afternoon with northwest wind gusts 20 - 25 kt. Brief high pressure builds in on Wednesday and another dry day is forecast. Skies remain clear in the morning hours, but cloud cover increases in the afternoon ahead of the next system. Highs both days will be similar. Lower 70s on Tuesday and a few degrees lower on Wednesday. Dewpoints in the low 40s Tuesday afternoon lower to the mid 30s by Wednesday afternoon. To start the long term period, models suggest multiple disturbances riding along a warm front but differ on exact impact to the CWA. Will have some slight chance PoPs on Thursday. Will keep POPs out of the forecast for Friday, however will need to keep an eye on the timing of one of the weak waves. Models then in good agreement with a warm frontal passage Saturday morning and then a very warm day, with highs close to 90 in NE NJ per NBM. A blend of the NBM 50^th/75^th percentile suggests potential for temps a few deg warmer than that, with lower 90s most areas NW of NYC, 80s most elsewhere, and 70s for the south facing coastlines out east. .MARINE... A Dense Fog Advisory remains in effect over the eastern two ocean zones and South Shore Bays of Long Island through 14z this morning. Visibilities will be as low as less than a mile. Fog can be seen eroding from west to east on satellite imagery, so it is possible the Advisory could end earlier than 14z. Winds and waves remain below SCA criteria through the day. Gusts up to 25 kts are likely just ahead of and behind a cold frontal passage tonight on the eastern two ocean zones. A SCA is in effect for these two zones from 00z tonight until 10z Tuesday morning. Waves will also build to 5 ft during this time period. Pwats are progged to be 1.5 inches or slightly higher. According to SPC`s Sounding Climatology Page, this is between the 90% moving average and the max moving average for OKX. Given these high pwat values any showers or thunderstorms that move through the area today could produce heavy downpours. This could lead to minor flooding in urban and poor drainage areas. Generally, 0.50 - 0.75 inches of rainfall is expected for NYC and points north and west, with locally higher amounts possible. WPC has placed the western half of the area in a marginal risk for excessive rainfall. Rainfall rates will generally between 0.25 - 0.50 inches per hour. The CAMs are showing a few bulls-eyes of 1 inch per hour rainfall rates, so this cannot be ruled out completely, but will likely be very localized if at all. HREF and NBM probabilities of >1 inch per hour rainfall rates suggest it is unlikely. Astronomical tides are running higher than usual. Departures of only about 1/2 ft are needed to cause minor coastal flooding along the western Sound, Nassau back bays, and possibly also lower NY Harbor with the high tide cycles tonight.