Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 282020 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 320 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/...
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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.
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&& .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 125 PM Tuesday... Pockets of low end VFR/high end MVFR ceilings will persist across parts of the coastal plain and sandhills this afternoon. The MVFR ceilings may briefly occur at KRWI and KFAY. A mid/upper level disturbance lifting east-ne across the TN Valley into the central Appalachians this evening. This feature may produce a few showers in the vicinity of the Triad terminals between 00Z-06Z. The showers should be more concentrated to the north of the Triad. 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. 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 500 AM Tuesday... Critical fire weather conditions are expected on Friday, after a day Thu with low RH and drying fuels, and marginal NWly winds. Behind a cold front that will cross central NC Wed night, surface dewpoints will fall into upper teens over the NW Piedmont to 20s elsewhere on Thu. When combined with afternoon temperatures in the upper 50s to middle 60s, relative humidity values between 20 and 25 percent will result. However, NWly winds will be strongest between 10 AM and 1 PM - prior to the lowest humidity values being met during the afternoon hours. In addition fuel moisture values will probably be residually elevated after a round of showers and storms accompanying the cold front Wed evening-night. Nonetheless, the low RH will at least set the stage for Fri, when a reinforcing cold front and following NWly winds and low RH will result in critical fire weather conditions. Cold and dry air advection behind the cold front, and associated deep mixing up to 7 or 8 thousand ft, will favor the development of breezy NWly sustained winds of 14-19 mph, with 25-30 mph gusts. Afternoon surface temperatures and dewpoints in the 50s to around 60 degrees, and teens to lower 20s, respectively, will yield minimum RH values between 20-25 percent. Rapid/explosive fire growth may result; and a Fire Weather Watch may be coordinated with NCFS on Wed. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...KC AVIATION...WSS FIRE WEATHER...MWS

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