... A relatively dry cold front will move southward across the area tonight. Another cold front, with a little more moisture, will cross the region from the west on Monday. A shift to a wetter pattern is then expected through the middle of the week as a series of disturbances bring Gulf moisture back into the region.
NEAR TERM /THROUGH SUNDAY/... 1015 PM EST Saturday: Main update this evening was the lowering of cloud cover slightly across the southern CWA as cloud cover has decreased the last few hours. Cirrus continues tracking across the northern CWA this evening. Vort energy from a southern stream shortwave trough over the Lower Mississippi Valley and Deep South is the main cause of this sporadic cloud cover.
A weak cold front continues pushing south across the area from the north tonight and is currently draped across the southern CWA. A broad surface high will slide across the Ohio Valley and Mid- Atlantic behind the fropa allowing winds to veer and come out of the northeast, setting up a weak wedge configuration overnight. Southerly component in the 925mb - 700mb level will promote a deeper moisture influx as WAA gets underway above the wedge. This will help lower clouds bases and thicken the cloud cover as a whole. Moist upglide will begin to filter in and could allow for enough isentropic lift for a few isolated showers to develop after daybreak Sunday in the southwest mountains. However, this chance for PoPs seems fairly low so kept PoPs below 15% through the morning hours. Model guidance has PoPs "ramping up" so to speak after 18z Sunday across the SW mtns and eventually spreading into more of the western zones by Sunday afternoon/early evening. Coverage looks mostly isolated to scattered at best. So, unfortunately not everyone will see rain across the western zones on Sunday. Most of the activity will be very light and should stay mainly confined to the mountains/foothills, with a low chance of isolated showers pushing east of the mtns towards the end of the near term forecast period. Winds will be a bit on the breezy side tomorrow morning into tomorrow afternoon, especially across the mtns, thanks to a slight pressure gradient between the sfc high pressure over the Mid- Atlantic and the low pressure system over the Great Plains and Midwest.
Overnight lows will be 10-15 degrees above normal due to the extensive cloud cover and warm low-level thicknesses. The wedge potential on Sunday will drop max temperatures to near normal or just below normal.
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... As of 225 PM EST Saturday: The short-term fcst picks up at 00z on Monday with broad upper trofing digging down over the Dakotas and Minnesota as broad upper ridging gets pushed farther of the Atlantic Coast. By late Monday/early Tuesday, the trof axis will translate eastward and pass to our north as flat upper ridging persists to our south over the Gulf of Mexico. By the end of the period late Tuesday, the upper trof will get reinforced and broaden as the SE CONUS remains under relatively flat upper ridging. At the sfc, a weak wedge front will retreat northward early Monday as a fairly strong cold front approaches the southern Appalachians from the west. These features will permit deeper moisture to accumulate along the approaching cold front west of the Appalachians, with mountain PoPs ramping up as the period begins early Monday. The moist frontal band will likely dry up as it crosses the higher terrain, with minimal QPF surviving east into the Piedmont for Monday aftn/evening. I maintain likely to Categorical PoPs across the mtns and into the foothills on Monday, and taper them down east of the higher terrain. Surface high pressure will move from the Ohio Valley to the Mid-Atlantic region on Tuesday, with the high nosing southward into our region. Upglide moisture should get started once again from the south on early Tues, but onset time uncertainty will contribute to PoP/temperature uncertainty. Good cloud cover is likely for much of the day, so temps should remain well-below normal, even if full-blown wedging does not set up early. If any precipitation does develop over the mountains early Tuesday, a mixed bag of ptypes could be possible as initially dry profiles wet bulb down. Fortunately any QPF should be light, but conditions will need to be monitored for the possibility of very light snow/ ice accumulations at the higher elevations.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... As of 220 PM EST Saturday: The extended fcst picks up at 00z on Wednesday with very broad upper trofing centered over the Central CONUS and flat upper ridging centered over the Western Caribbean. Over the next 24 to 36 hrs, the trof axis is expected to pass to our north with heights recovering very modestly in its wake on Thurs. For the remainder of the period, upper ridging will steadily build just off the Atlantic Coast while deep upper trofing digs down across the Western CONUS. At the sfc, the pattern will remain fairly active thru the period with a good amount of uncertainty wrt how the synoptic pattern will evolve. As the period begins, high pressure will be lifting NE from the Mid-Atlantic region and away from our area. At the same time, a low will develop over the deep south and lift up and over the Carolinas on Wed. The combination of deeper forcing and more abundant moisture centered around this period should yield widespread one inch rainfall totals, with event totals possibly reaching two inches (or more) in some southern mtn locations. Profiles still appear to only support rain during nearly all of the QPF window. The low is expected to quickly lift offshore with high pressure spreading back over the fcst area on Thursday. Beyond this point, there are hints of a secondary southern stream wave reaching the southeast Thursday night into Friday, while the better moisture still appears relegated to our south and east late in the week. Nonetheless, deeper low-level moisture will persist across much of the area and require a prolonged isolated/scattered shower mention into the weekend. Temps rebound to near climatology by Friday and well above climo for next weekend.