... A warm front will head north into the Tennessee Valley tonight into Sunday. This feature will remain parked over the region through at least the middle of the week, along with its associated showers and some afternoon storms. For the latter half of the week, the front will head north to the Ohio Valley, taking with it the bulk of the showers, and temperatures will be on the increase.
NEAR TERM /THROUGH SUNDAY/... As of 200 PM EDT Saturday...
...Trending towards cloudier and wetter conditions...
Surface high pressure was centered over southeast Georgia. Low pressure near the KS/OK border was strengthening and shifting slowly east. In response, low level southerly flow to its east was intensifying, and prompting the development of a warm front over AR/west TN. Cloud cover over our region was currently diurnally based, with LCL bases in the 7000-9000 ft AGL range thanks to a surface dew point depression around 25-30 deg F. We are expecting these clouds to quickly dissipate around sunset, and allow for a brief period of relatively cloud-free skies early this evening.
Overnight, the developing warm front in the Mid-Mississippi Valley will continue to organizing and expand into the Tennessee Valley. With it will come increasing/lowering cloud cover into first the western portions of our area by daybreak Sunday. With these lower clouds will also come some isolated light showers.
Low temperatures tonight will average about 10 to 15 degrees warmer in the west compared to readings this morning thanks the increasing dew points and cloud cover. Look for the mid to upper 40s for lows across the mountains and upper 40s to lower 50s across the Piedmont.
For Sunday, isolated to scattered showers will continue to expand in coverage from west to east. While chances are on the low side, there may be enough instability aloft for the development of isolated thunderstorms in areas near, north, and east of Roanoke, VA. Despite light south to southwest winds start to begin some weak warm air advection into the region, the presence of mostly cloudy to cloudy skies will allow for high temperatures around, or slightly cooler than those realized today. Readings in the low to mid 60s are forecast for the mountains with values around 70 to the lower 70s across the Piedmont.
Confidence in the above forecast scenario is high.
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... As of 150 PM EDT Saturday...
...Unsettled Weather Pattern to Begin the Week...
The work week will begin with a continued rather unsettled pattern that will gradually become more summerlike toward the end of the week. An active west-northwest flow will remain in place at the beginning of the week as an upper trough exists the east coast and another one approaches from the Midwest. A frontal boundary should be draped across the midsection of the country as a result from the Midwest into the Mid-Atlantic region during this time frame. The combination of the disturbances aloft, increasingly warm/humid air tracking northward into the region, and the presence of the frontal boundary will provide a focus for convection.
The first disturbance of significant will track across the region Sunday night into Monday. The northern and western sections of the CWA appear to be the most favorable for convection during this time frame. with any convection developing across the OH Valley and WV having the potential to ride through the west-northwest flow aloft into the Mid-Atlantic region before diminishing Monday morning.
Outflow boundaries, the continues proximity of a weak boundary and the second disturbance tracking out of the northwest will likely refire convection across central WV into central VA Monday afternoon and this activity could persist into the afternoon and evening hours as well as it tracks southeast and diminishes somewhere across east central or southeast VA and near the NC border. With ridging aloft beginning to amplify across the eastern states at this point, this convection could become slower moving, resulting in heavier rain production across specific areas, such as east central VA/piedmont.
At this point, parameters do not seem to favor much in the way of severe. However, as the convective activity becomes more organized in clusters or potentially into an MCS Monday Night/Tuesday early morning, the potential for strong wind gusts becomes more likely. Will just go with SPC outlooks for now and just show probability is low in the eHWO and HWO text product.
Temperatures will moderate slowly during this time frame but no dramatic warmup is indicated as 850mb temperatures slowly creep up into the +10C to +12C during the first half of the week. This will result in afternoon high temperatures in the 60s and 70s with lows still in the 40s and 50s at night, about 10 degrees warmer than the past couple of days. Winds will be light through the period.
/Confidence Levels in Forecast Parameters/ - Moderate Confidence in Temperatures, - Low to Moderate Confidence in Probability of Precipitation Values, - Moderate to High Confidence in Wind Direction and Speeds, - Moderate Confidence in Thunderstorm Probabilities.
LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 200 PM EDT Saturday...
...A More Typical Summer Like Pattern Expected During the Later Half of the Week...
The models have definitely trended more and more toward a typical summerlike pattern during the extended periods with today's model runs. A strong ridge of subtropical high pressure is progged to build across the eastern U.S. during the later half of the week as a broad area of negatively tilted low pressure becomes anchored in the southwestern U.S. This will bring the tale of two weather stories to the CONUS, namely west and stormy in the central U.S., warm and humid with more summerlike weather conditions in the eastern U.S. In fact, given all of our cool weather conditions in recent weeks, this may be our first real taste of summer since last year. There are a few caveats, however, that may temper the warming across our region.
As the ridge first builds during the mid part of the week, the chance for diurnal convection continues across the mountains with lessening chances as we move from Wednesday into Thursday. By Friday, but more likely into Saturday, the ridge will weaken and/or back off enough to the west to allow a backdoor cold front to sag southward into the northern Mid-Atlantic. More organized convection would be possible along a backdoor front and could sneak into central VA toward the end of the forecast period.
Otherwise, conditions look very much like early summer with isolated to scattered afternoon/evening convection, mainly across the western mountains, with warmer and more humid conditions. With some models showing 850mb temperatures potentially reaching the +20C level by the end of the week, that would indeed translate to some of our warmest temperatures so far this year. For now, will stick with highs in the 70s and 80s, a few areas near 90 in the Piedmont by the end of the week, with milder/more humid nights and lows in the 50s and 60s.
/Confidence Levels in Forecast Parameters/ - Moderate Confidence in Temperatures, - Moderate Confidence in Precipitation Probabilities, - Moderate to High Confidence in Wind Direction/Speed, - Moderate Confidence in Thunderstorm Probabilities.