Wisp Resort / McHenry

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McHenry, MD

Forecast Discussion



... Shower and thunderstorm chances increase Friday into Saturday with the approach and passage of a cold front. The rest of the holiday weekend is trending dry with above normal temperature.

NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... High pressure will begin sliding east of the region through the overnight hours while upper flow becomes more southwesterly ahead of an incoming shortwave trough. Warm, moist advection will develop, boosting overnight low temperature and allowing for more mid-level cloud coverage by dawn.

SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... The shortwave trough and cold front will continue to approach the region Friday. The speed of approach is expected to remain slow, with the cold front nearly parallel to the flow aloft. Diurnal instability is progged to build by afternoon, with model ensemble sfc based CAPE around 2000 j/kg. Diurnal heating and shortwave supported ascent should allow for isolated to scattered thunderstorm development during the afternoon, though the better frontal/shortwave support will remain to the northwest. There is potential that the lack of enough moist advection and the presence of warm air aloft may keep much of the environment capped and stunt initiation.

If storms do develop during the afternoon to early evening, the progged instability plus dry mid level air may allow for development of damaging wind gusts. Large hail is possible, but the main hazard appears to be wind. Will highlight this potential in the Hazardous Weather Outlook, as outlined by the SPC day 2 marginal risk/isolated coverage for severe weather.

Showers and sct thunderstorms should become more likely Friday night as the best shortwave support tracks across the Upper Ohio Valley region, and FROPA occurs from PIT nwd. Scattered showers/tstms are still expected Saturday morning invof the cold front, with the most likely activity S of PIT as the front completes its passage. Maintained some chance POPs Saturday night mainly S of PIT, should the progression of the front slow with the parallel flow aloft.

LONG TERM /SUNDAY THROUGH THURSDAY/... Broad upper troughing is progged to persist across much of the NE CONUS through next week, as the sfc front becomes nearly stationary south of the region in the vicinity of the OH river to the Mid Atlantic. Generally dry weather is expected to start with high pressure developing north of the stalled boundary, though relatively weak shortwaves embedded in the broad trough should result in periodic shower/tstm chances from Tuesday through late week. Precip chances could be higher should the sfc front stall farther N than currently progged.