Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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253 FXUS62 KRAH 282148 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 445 PM EST Tue Feb 28 2017 .SYNOPSIS... A mild southwest flow will persist across central NC through Wednesday. A strong cold front will cross the area Wednesday night, followed by cooler temperatures for the later half of the week. && .NEAR TERM /THROUGH TONIGHT/... As of 300 PM Tuesday... Tonight...main forecast concern is the convective coverage. Scattered-numerous showers and a few thunderstorms over eastern TN- sw Virginia will continue to slide ne in a plume of favored moisture transport/advection extending from western NC into western Virginia. The air mass over the Piedmont and coastal plain is not as moist as the atmosphere to the west, so should see a gradual decrease in shower coverage/intensity as the system advances east from the mountains. Still, should see a decent chance for showers after sunset through the evening in the Triad vicinity, though coverage will quickly dwindle to the south and east. Closer to home, heating of a slightly unstable air mass along and east of highway 1 may support an isolated shower late this afternoon- until sunset. Overnight, good potential for a deck of low clouds to develop as strengthening sly flow pulls an increasingly moist air mass into our region. The combination of overcast skies and a steady sly flow will result in very mild overnight temperatures, primarily in the 60-65 degree range. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... As of 320 PM Tuesday... A s/w dropping sewd out of the upper Midwest into the Great Lakes will propel a lead s/w across the TN Valley Wednesday and into the Carolinas Wednesday evening. This system will be accompanied by a band of convection. A strengthening low level jet (50-60kts) will support a strongly kinematic atmosphere. While the low level air mass will be toasty with afternoon temps in the upper 70s-lower 80s. Sfc dewpoints are forecast to be no worse than around 60-lower 60s. This is supportive of a weakly unstable air mass but not supportive of a widespread severe weather event. So, expect a band of convection with locally strong/severe wind gusts to enter the western Piedmont sometime close to or after sunset, then progress east into the highway 1 corridor in the 9 PM-Midnight time frame. Expect intensity of the showers/storms to diminish as it enters a relatively more stable air mass. Ahead of the showers and storms, southwest sfc winds will be gusty/windy with sustained winds 15-20 mph and gusts 30-35 mph. A deck of mid-high level clouds may deter insolation enough to prevent optimal mixing, leading to slightly lower wind gusts. Conversely, if more sunshine occurs than expected, wind gusts around 40 mph may occur, prompting the need for a wind advisory. Band of convection expected to progress east and exit our coastal plain counties in the overnight hours. Low level flow from the nw will advect a drier more stable air mass, leading to a decrease cloud trend nw-se overnight. This clearing line will likely lie across the Triangle region at daybreak, then progress swiftly se early Thu morning. Low level cold air advection will send temperatures tumbling north and west of Raleigh, leading to min temps in the low-mid 40s. Later arrival of the colder air will result in min temps in the 50s se of Raleigh. && .LONG TERM /THURSDAY THROUGH TUESDAY/... As of 220 PM Tuesday... Thursday and Thursday Night: The current timing of the cold front may result in a slight chance of showers lingering over the far southeast early Thursday morning, but the rest of Central NC should be dry and beginning to clear. Skies will continue to clear through the day, however the cold air advecting into the region behind the front will likely limit highs to upper 50s NW to mid 60s south. Winds will be northwesterly behind the front and remain quite strong through the day Thursday afternoon with sustained winds up to 15 kts with gusts to around 20 kts, diminishing late in the afternoon. Expect winds of 5 kts or less overnight, backing slightly to more westerly. The light winds combined with clear skies and continued cold advection will yield lows generally in the mid 30s across the area Thursday night. Friday through Sunday Night: This period is expected to remain dry. Highs Friday will be in the mid 50s NW to mid 60s South, though they will be somewhat dependent upon the timing of a reinforcing dry cold front expected to push through late Friday/Friday night. Highly confident the coldest temperatures will occur Saturday morning as a result of the aforementioned cold air (mid to upper 20s), as well as the surface high moving overhead. With the high overhead and continued northerly flow, highs Saturday will struggle to recover, maxing out in the low to mid 50s. Expect moderating temperatures once again through Sunday night as southerly flow sets up once again. Lows Saturday night in the low to mid 30s, increasing into the mid 40s by Sunday night and highs Sunday in the mid 60s. Monday and Tuesday: The surface high will shift off to the southeast as yet another low pressure system develops out west. The warm southerly flow increases over the Carolinas Monday and Tuesday as the aforementioned system moves east toward the Mid-Atlantic. There are still issues with timing of this system, thus confidence is somewhat low in that regard, but expect a chance for showers ahead of the front as it moves into the region early to mid week. As expected, temps will increase ahead of the front and decrease in its wake, however the timing is uncertain at this time. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... As of 445 PM Tuesday... Isolated showers will lift north across sections of the coastal plain and sandhills through early evening. Otherwise expect VFR parameters. A mid/upper level disturbance will lift east-ne across the TN Valley into the central Appalachians this evening. Areas of showers associated with this system should mainly occur west-northwest of our region, though a few showers in the vicinity of the Triad terminals may occur between 00Z-06Z. The sly low level flow will continue to advect moisture into our region. After 03Z, this added moisture should lead to the development of IFR/LIFR ceilings over most of our region, most likely between 09Z-13Z. A strengthening low level jet a few thousand feet above the surface will create marginal low level wind shear conditions, primarily in vicinity of the Triad, and mainly in the form of speed shear rather than directional shear. The IFR/LIFR ceilings will lift/dissipate by 14Z-16Z. In its wake, expect abundant mid-high level clouds and windy sfc conditions. Southwest winds Wednesday will likely gusts 30-35 mph with a few gusts topping 40 mph. A strong cold front will approach from the west late Wednesday and cross our region Wednesday night. Ahead of the sfc feature, expect and 15-30 mile wide band of showers and thunderstorms, producing MVFR/IFR conditions. The stronger storms may produce wind gusts 45- 55 kts. The convection threat will rapidly decrease west-to-east between 04Z- 08Z as the front sweeps across the region. Breezy sfc winds will occur early Thursday with gusts generally 25 kts. Otherwise expect VFR conditions late Wednesday night through Sunday. && .FIRE WEATHER... As of 445 PM Tuesday... A cold front will cross central NC Wednesday night. Out ahead of the boundary, south-southwest 15-20 mph expected with gusts 30-40 mph. Minimum RH values Wednesday afternoon should bottom out 45-50 percent. Scattered convection should occur Wednesday night, though precip will be in the form of showers, and fall in less than an hour. This will not allow the rain to soak into the dry/dead grasses/leaves. Minimum RH values Thursday afternoon will fall to near the critical level of 25 percent. Gusty NW winds are expected Thursday morning though the winds are expected subside Thursday afternoon (at the time when the RH reaches the critical level). A secondary cold front is expected to cross central NC Friday afternoon. Again, RH values will bottom out around 25 percent. Sfc winds may gusts 20-25 mph out of the NW by Friday afternoon. These parameters may result in increased fire danger over the region. This may require the issuance of fire weather statements, per coordination with the NC Forestry Service. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...KC AVIATION...WSS FIRE WEATHER...WSS

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