Forecast Discussion
Summary
SYNOPSIS
... Clouds slowly erode from the south and east through tonight. Low pressure brings showers and isolated storms Wed and Thu. High pressure returns to round out the month of September.
NEAR TERM /THROUGH TONIGHT/... As of 1034 AM Tuesday...
Tinkered with sky conditions for late this morning into this afternoon based on current satellite trends. Some clearing spots are beginning to take shape in the southern coalfields and up the I-79 corridor, but still holding strong along the Ohio River Valley. Despite these changes, temperatures and dew points remain on track from the top of the hour, so no changes were necessary to those parameters.
As of 310 AM Tuesday...
Abundant low level moisture, left behind by the departing upper level disturbance, remains trapped beneath a low level inversion keeping widespread low clouds and morning fog in the forecast. Satellite imagery shows show how this stratus deck is eroding from south to north across southeast VA early this morning. Clouds will continue to erode especially across the western half of the area this morning, and may bring clearing in some areas, spreading from west to east during the afternoon hours. However, clouds and some periods of light precipitation may linger across the higher terrain into tonight.
Clearing and near calm flow across the western half of the area tonight will allow for areas of dense fog to develop into early Wednesday morning.
With some sunshine across northeast KY and southern WV, expect temperatures to reach the lower 80s this afternoon. Temperatures across the rest of the area will reach the lower 70s, ranging into the mid 50s highest elevations of our northeast mountains.
Lows tonight will be a bit warmer than last nights as H850 flow becomes southeast. Lows will generally be around 60 degrees, ranging into the low 50s higher elevations.
SHORT TERM /WEDNESDAY THROUGH FRIDAY/... As of 305 AM Tuesday...
An upper level low transiting the Midwest initially supported by a northern stream jet streak, will lose northern stream support during the day Wednesday and begin to fill as it wobbles toward the Lower Great Lakes through Thursday. Cooler air aloft associated with this feature will steepen mid-level lapse rates yielding up to 1000J/kg both Wednesday and Thursday afternoons, primarily west of I-77. On Wednesday, some more robust convection is expected across the Lower Ohio Valley, likely focused at a shortwave pinwheeling around the aforementioned low. Generally think by the time this forcing arrives in our western counties, instability will already be starting to wane with the loss of heating, with cells generally trending down below strong/severe limits as they approach. A possible exception to this will be with any discrete convection - good low level turning should allow for any low topped supercells to persist into a less favorable environment for at least an hour or two after other storms begin to dissipate.
Thursday looks less favorable for any strong to severe storms with weaker shear, more cloud cover, and even later timing of a feature for forcing.
Overall, this slow moving system is expected to produce around an inch of beneficial rain across our west with minimal accumulations across the east. Outside of one or two supercells moving into a less favorable environment Wednesday, the risk for severe storms is expected to be low.
The upper low completes its transition into an open wave Friday with the mid-level trough axis passing around daybreak with lingering showers becoming confined to the mountains by Friday afternoon.
LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... As of 305 AM Tuesday...
For the balance of the forecast, the dominant feature will be ridging building across the middle of the country yielding mostly quiet weather in our neighborhood with above normal temperatures.