Wisp Resort / McHenry

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McHenry, MD

Forecast Discussion



... Northwest flow will maintain seasonably cool conditions with intermittent smokey and hazy skies through late-week. Shower chances will increase Thursday and Friday afternoon. The first sizable rain chance in weeks will come Sunday into Monday.

NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... A closed low remains centered over Maine, and will continue to spin over the interior northeast. A shortwave axis will pivot through this evening, through limited available moisture will minimize precipitation chances. Daytime mixing into a shallow near-saturated 700mb to 800mb layer has resulted in some fair- weather, elevated cu that will quickly dissipate at sunset.

Quebec wildfires are continuing to burn, releasing smoke into the atmosphere. The upper low will continue to pull this smoke southward toward our forecast region. Haze was highlighted area- wide due through the near term, though higher particulate densities are denoted as smoke in the forecast. Visible satellite indicates a plume of higher density smoke is currently advecting over the region from the north. Density will be locally higher northeast of the Pittsburgh metro today, then east of the Pittsburgh metro overnight. This has prompted Pennsylvania DEP to issue a code RED Air Quality Alert for today. Follow local Department of Environmental Protection air quality alerts to learn the latest impacts this could have for your given location.

Smoke has resulted in high temperatures peaking a few degrees below their radiative potential. Lows will be around 10 degrees below average.

SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... Additional PVA movement around the New England low and the gradual moistening of mid-levels as moisture wraps around the system will provide isolated to scattered shower chances Thursday and Friday afternoons. Pressure height falls and notable PVA will foster enough lift/instability to create showers/thunderstorms. Precipitation chances will be mostly likely towards northeast of the Pittsburgh metro, with the deepest moisture. Probabilistic QPF currently ranges between nothing to 0.25 inch on Thursday, and nothing to 0.4 on Friday for Dubois, albeit totals will be blotchy and limited with the their convective nature and limited moisture availability. This will do little to help current dry conditions.

The combination of an increase in afternoon clouds and falling pressure heights will cause area temperature to cool a few degrees below normal. In addition, northerly winds are expected to bring potentially additional rounds of smoke/haze to the region as the Quebec wildfires persist. Continue to monitor local DEP authorities for the latest on the impacts this will have on air quality.

LONG TERM /SATURDAY THROUGH WEDNESDAY/... Ensembles favor a notable pattern shift starting Saturday into early next week by first lifting the New England low farther northeast and nudge shortwave ridging just west of the region Saturday. The next area of low pressure will quickly drop and deepen as it moves around a northern Rocky Mountain high, likely becoming a closed low somewhere over the Great Lakes by Monday.

The briefing ridging Saturday will favor temperature moderation and return to areawide dry weather. Then, the approach of the upper low will support moist advection within SW flow over the Upper Ohio River Valley, with front/shortwave passage creating widespread precipitation chances. This will end chances of smoke from Canada through the rest of the long term.

Though timing and synoptic feature details remain muddy, ensemble consensus on the general pattern favors to providing the first notable period of QPF accumulation by Sunday night through Monday. Probabilistic QPF ranges between 0.1 on the low end to 1.25 on the high end. There is relatively high confidence at this point that dry streaks for any observing sites will come to an end. The strength and longevity of the upper trough over the Great Lakes will likely dictate how quickly the next precipitation chance arrives thereafter.