Halloween Headlines

ALERT For Strong S-SW Winds Today Shifting W-NW_Much Colder Air With Plunging Late PM And Evening Temps

A strong pressure gradient developing along and in advance of a potent cold front will increase winds across the mountains, beginning at high elevations on Wednesday and mixing downward into middle-lower elevations on Halloween. In addition, there will be a marginal risk that some thunderstorms could become severe with damaging winds and hail. Orographic forcing will be activated with this system to also generate a heavy rainfall potential, especially within favored upslope locations along the High Knob Massif and Black Mountains.

ALERT For The Potential Of Strong-Severe Thunderstorm Development Ahead Of A Halloween Cold Front

*Strong winds will be driven by huge temperature anomalies between much above and below average conditions which develop pressure differences that form gradients to move air, as the atmosphere works vigorously to restore geostrophic equilibrium into Halloween.

*Orographic Forcing is a multi-parameter phenomenon of the Climate System whose foundation is based upon three-dimensional terrain interactions with wind speed and direction, as well as all associated aspects of advection and fluxes. It is a dual phase phenomenon featuring positive and negative (inverse) phases possessing both high predictability (in terms of weather) and long-term statistical influence (in terms of climate) on the natural world.

*Showers develop by mid-day Wednesday. Rain may be heavy at times during the afternoon, and increasingly wind driven at upper elevations where orographic pilatus clouds will develop to generate dense, ground-level fog.

*Wind driven rain, with a chance of thunderstorms, will develop Wednesday night into Thursday. Unseasonably warm conditions are expected in advance of a cold front. Locally heavy rainfall amounts are likely, with capping orographic feeder clouds at upper elevations to enhance the amount of rainfall reaching the surface in upslope locations (expect a prolonged period of dense, ground level fog, in orographic clouds, at upper elevations).

This will be the first system during Autumn 2019 to activate orographic forcing to any significant extent, with previous systems during September-October producing little variation in rainfall between the Tennessee Valley and mountains amid weak orographics. As is common during transitional seasons, mixed modes will remain possible with both convection and orographic forcing modes in operation which could act to skew precipitation amounts more than typically observed with only orographics and dynamical forcing.

*A significant fall of leaves are expected, especially at higher elevations where wind speeds will be strongest. Caution is advised on roadways across the area.

*A temperature crash will occur starting late Thursday afternoon into Friday morning, with widespread sub-freezing air temperatures and bitter wind chill factors. Rain could become mixed with sleet, snow, or freezing drizzle prior to ending, especially at higher elevations along the Cumberland-Allegheny Front and highest peaks of the Blue Ridge.

**A temperature drop of 35 to 45 degrees is expected between prefrontal warmth and invading cold by early Friday. Wind chills will drop into the 10s and 20s, except single digits to around 0 degrees on highest peaks by early Friday.

While 40+ degree temperature changes are common in mountain valleys between AM and PM readings, this will be the first system of Autumn 2019 to drive such a temperature drop across all locations within 12-18 hours, the first system to generate a widespread freeze, and the first system to drop wind chills on high peaks toward 0 degrees.

Colder November Weather Pattern

Temperatures will turn colder at the dawn of November and this will be a pattern that will dominate the first 1-2 weeks of the new month, at least in the mean, with a trend toward cold conditions across the eastern USA.

Persistent blocking supported by anomalously warm sea surface temperatures around Alaska will help to anchor a colder pattern downstream into the central-eastern portions of the USA.

Everything in the natural world can be modeled in wave form, including sea surface temp anomalies and all aspects related to the fluid atmosphere and climate system.

Wavelengths around the Northern Hemisphere, and planet, follow the physics law formulated by Wien, with longer wavelengths developing in colder air at this time of year replacing the shorter wavelengths of the summer season.

This pattern is currently predicted to strengthen during the 5-10 day period. Stay tuned for later updates.