... Light rain begins to overspread the region late tonight. More widespread rain Friday with rain and snow showers lingering into the weekend.
NEAR TERM /THROUGH FRIDAY/... As of 840 PM Thursday... Quick update to hourly temps and dew points. Otherwise, no significant changes. A light wintry mix is still a possibility early Friday across parts of the northern mountains. However, lots of uncertainty remains in terms timing of any precipitation reaching the ground/able to overcome dry air in lower levels of the atmosphere, and temperatures at onset. Have elected to not issue any winter weather headlines due to this, and will allow the mid shift to keep an eye on the situation.
As of 1250 PM Thursday...
Increasing south-southeasterly flow coupled with thickening mid- level cloud cover will limit overnight cooling with much of the area remaining above freezing. The only exceptions will be the higher ridges of WV mountains as well as some of the more protected valleys, the Greenbrier in particular where temperatures look to bottom out right around the freezing mark. Strong warm air advection overnight will result in increasing precipitation chances, although a substantially dry sub-cloud layer may delay precipitation onset somewhat. Given the aforementioned temperatures, not overly concerned about a brief freezing rain potential across our sections of the Greenbrier Valley, although will need to keep an eye on temperature trends overnight. The initial round of precipitation through Friday morning will be rather light with accumulations less than a tenth of an inch. A strengthening low level jet this evening will yield some gusty winds, mainly along the lee slopes extending out into the Lowlands as downslope flow develops. Initially think warm air advection will be too strong and wind field aloft too weak to support enough momentum transfer to the surface to support any wind highlights.
The main precipitation shield associated with an upper level low coming out of the Midwest will cross the region during the afternoon/evening hours Friday bringing additional rain accumulation of half to once inch, except less than half an inch in the most rain downslope favored areas downwind of the Cumberland and Allegheny Mountains. The biggest concern during this period will be the magnitude of downslope winds developing off the higher terrain as the axis of a 60+KT low level jet transits the area. Given battle between warm air advection and terrain induced downslope, do not currently have the forecast confidence to go out with any wind highlights for Friday afternoon, but these may eventually be required across portions of the lee slopes encompassing Nicholas, Webster, Pocahontas and Randolph County - will add this to the HWO with the afternoon package. Think outside of downslope enhancement higher momentum aloft will not see enough momentum transfer to the surface to support wind highlights, even as the more robust round of precipitation comes through during the day Friday under continued warm, transitioning to neutral temperature advection.
Still some uncertainty as to exactly how thermal profiles will ultimately evolve in the WV mountains into Friday afternoon, but currently thinking precipitation remains mostly rain, perhaps mixing with snow at times across the highest elevations with minimal accumulations through Friday evening.
SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 215 PM Thursday...
This period starts off in the trenches with warm sector rain showers spread across the region with expected cold frontal passage for Saturday morning. Looks like models are slightly warmer than previous runs nudging in a shallow warm nose, therefore rainfall will continue on through the morning with very little moisture residing in the dendritic ice growth layer anyways. However, there will possibly be some flakes in the highest peaks with very little accumulations. Moisture will become more prominent in the growth layer in the early afternoon where a transition to to a mix/all snow will take place into early Sunday morning. At this point a lee side trough associated with the parent low will have moved off and wont help much with moisture anymore contradicting previous thinking. This will likely drop rain rates and eventually snow rates.
Another transition will take place Sunday afternoon when the parent low shifts off to a more northern trajectory taking energy and moisture with it. At this point the lowlands will see very little in the way of snow showers due to the lack of moisture in the ice crystal growth layer. However, they stand to have a chance with possible seeder feeder moisture in place by Sunday afternoon allowing for some possible light snow showers although with very little accumulations expected. The mountains will still flourish with wrap around upslope flow adding to the snowfall amounts and moisture in the ice crystal layer. It seems like the system itself has weakened slightly according to the latest model runs and with that said, I lowered snow amounts fairly significantly even going on the low side of the global ensemble forecast models. This time around we are more in line with guidance plus upslope flow is not looking to impressive. Therefore, tweaked snowfall amounts significantly lower in the mountains and slightly in the northern lowlands. As the parent low moves further away through Sunday there wont be much left for activity in the lowlands by the evening. The mountains will still have some potential for lingering showers, dependent on enough moisture provided by upslope though, and this will eventually be cut off by Monday afternoon.
LONG TERM /MONDAY THROUGH THURSDAY/... As of 235 PM Thursday...
A fairly mundane long term period with a few disturbances possibly affecting the area on Wednesday/Thursday. With temperatures below seasonable during this time frame am expecting that the area would see snow flurries, but confidence is not high enough to place wagers on anything other than chance POPs right now at this time. High pressure dominates thereafter, with models hinting at the next system towards the middle of next weekend.