An Alert For Frost And Freezing Temperatures Will Likely Be Needed For Parts Of The Mountain Area By This Weekend ( * ).
*River valleys and typically milder thermal belt ridges may be able to escape freezing temperatures, versus colder mountain valleys, but those with flowers and late season crops should stay tuned for later updates on this first major push of autumn air.
Meanwhile, Hurricane Marie will influence the mountain region with high clouds at times during the next few days. A general subsidence, or sinking air, regime will be a main influence that will continue to help support unseasonably warm conditions ( especially by day ). Air flow around her circulation field will also be a factor in wind directions.
Overnight Into Monday Morning
Partly cloudy ( high clouds streaming off Hurricane Marie ). Large vertical temperature spread between colder valleys and exposed mountain ridges-plateaus. SE winds 5-10 mph, with higher gusts, along mid-upper elevation ridges. Temps varying from 40s colder mountain valleys to low-mid 60s. Areas of dense river valley fog.
Monday Afternoon
Partly sunny ( high clouds may continue to stream off Marie into the region ). Unseasonably warm. Easterly winds less than 10 mph in most places. Temperatures varying from the lower 70s in upper elevations to the upper 70s to lower 80s ( warmer south into the Great Valley ).
Monday Night Into Tuesday Morning
Mostly clear. Light winds in valleys. Winds ESE-SSE at 5-10 mph, with higher gusts, on mid-upper elevation mountain ridges. Large vertical temperature spread between colder valleys and milder ridges-plateaus. Temperatures varying from 40s to lower 50s in the colder valleys to the lower-middle 60s. Areas of dense fog within main river valleys and around larger lakes.
Tuesday Afternoon
Partly-mostly cloudy. Light northerly winds generally less than 10 mph. Temperatures varying from lower 70s in the upper elevations to the lower 80s ( warmer south into the Great Valley and within lower elevations of river basins ).
Tuesday Night Into Wednesday Morning
Partly-mostly cloudy. Light northerly winds, except breezy along highest mountain ridges. Milder with temperatures generally in the 50s ( valleys ) and 60s ( ridges ).
Preliminary Outlook – High Knob Naturalist Rally
My initial outlook is forecasting clear skies and chilly conditions with a classic, deep blue afternoon sky above High Knob Lake on September 30. A northerly air flow is expected, especially for those who visit High Knob Lookout where conditions will mainly feel like 40s during the day.
Morning temperatures in the 30s to lower 40s will only rise into the low-mid 50s by 2:00 to 3:00 PM at High Knob Lake, then drop back into the 40s and 30s on Saturday evening. Generally an ideal forecast for those seeking a taste of the high country in early autumn. Hope to see you there!
Following morning lows in the 40s and 50s in mountain valleys, with low-mid 60s on ridges, another unseasonably warm day was observed. Monday afternoon maximums reached low 70s on High Knob and low 80s in Clintwood, with my official NWS max being 81.1 degrees.
My update this afternoon includes the first preliminary forecast for the 11th Annual High Knob Naturalist Rally. This forecast will become more detailed later in the week.
Meanwhile, a nice little group of stationary lenticular mountain wave clouds are featured at sunset on Monday ( September 25 ) as viewed from the High Knob Massif Webcam located on top of the Computer Science-Mathematics Building on campus.
High Knob Massif Webcam – University Of Virginia’s College At Wise
These clouds are being generated by east-northeast air flow streaming across the massif from the broad circulation field associated with Hurricane Marie.
NAM 12 KM Model 10-Meter Wind Field At 2:00 PM on September 25, 2017
A general subsidence regime is ruling, but orographic lifting along the High Knob Massif is taking advantage of just enough moisture to develop this group of stationary lenticular wave clouds.
Like Monday morning, when low temperatures reached the mid-upper 40s in cooler valleys, this will support another chilly night in typically cooler valleys of mid-upper elevations as the dry air allows for a large diurnal temperature spread in valleys.
NAM 12 KM Model 850 MB Wind Field At 2:00 PM Monday – September 25, 2017
Previous Discussion
Early Autumn at High Knob Lake Recreation Area – September 23, 2017
Although conditions vary significantly across the area, color continues to develop across the high country and is currently varying from green trees to bare trees!
Approaching Sunset At Upper Norton Reservoir – September 23, 2017
Big weather changes continue to look likely just in time for the 11th Annual High Knob Naturalist Rally, with 40s to mid 50s day-time temperatures ( at max heating ) currently in my forecast. A detailed forecast will be issued later.
Hurricane Marie – Overnight Of Monday – September 25, 2017
High clouds from Hurricane Marie are moving overhead tonight as she spins closer to the eastern coastline of the USA. Although chances for rainfall are looking to increase into the first week of October, the nearby presence of Marie will in part hinder precipitation development along and in advance of the first strong autumn cold front that sweeps into the region later this week ( pushing Marie away ).
National Hurricane Center Forecast Track
Tropical Storm Watches are in effect for eastern North Carolina.
Marie will impact our weather in a number of different ways, as already highlighted above, with winds along highest mountain crestlines being a little gustier even tonight due to a SE flow forced by the large wind field circulating around Marie. Winds will shift in direction through coming days as Marie changes her position.
