Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 220217 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 917 PM EST Sun Jan 21 2018 .SYNOPSIS... High pressure will continue to drift offshore through tonight. A frontal system will approach from the west Monday, and cross central NC late Monday night through early Tuesday. A seasonably cool air mass will settle into the region for mid-week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 920 PM Sunday... Very mild January evening continues across central NC as temperatures still above 50 degrees in some locations at this hour. Another notable difference over last night is the substantial increase in dewpoints across the area with upper 30s to low 40s across the board. Looking at 00z soundings, GSO still quite a bit drier at the low levels whereas MHX has come in with a fairly moist surface layer. Once again we have the question of some overnight fog and in this case, the best chances will be in the east, closer to that MHX sounding. That being said still not a slam dunk forecast and will probably occur much later, showing up between 6 and 9z. Back to the west don`t expect as much of a chance but either way, temperatures will remain well above freezing, avoiding any confrontation with freezing fog. Upper 30s to low 40s.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY/... As of 330 PM Sunday... A deep, mature upper level cyclone over the central Plains will lift newd into the Great Lakes Monday and Monday night. A sly flow ahead of this system will strengthen during the afternoon-evening with sustained wind 10-15kts Monday night, and gusts 20-25kts probable after midnight. While clouds will thicken/lower Monday, and more so Monday night, based on model rh cross sections and upstream observations, expect a veil of high clouds Monday, likely thin enough to allow at least partial sun to occur. This warming, coupled with a steady sly flow, should allow temperatures to recover into the low-mid 60s, possibly upper 60s across the southeast. Cannot rule out the possibility of a shower or two toward sunset across the southern counties though feel that most locations across the south will remain dry. Kinematics very strong Monday night thanks to a 130+kt upper jet crossing the TN Valley and a low level jet 45-50kts. Bulk shear more than sufficient to support banded convection. However, sfc based instability meager at best, with most of the instability elevated as per skinny areas of CAPE seen on model soundings. Thus, while expect band of heavy showers with the system, an isolated storm or two possible. As better upper level support passes to our nw late Monday night, expect a band of showers to lift east-ne across central NC after 06Z, with the band projected to be in vicinity of highway 1 around 10-12Z. The warm sly flow and thickening cloud cover will maintain mild temperatures. Overnight temps mainly 55-60 degrees. Tuesday, a band of showers will exit the coastal plain counties by mid day as the sfc cold front sweeps across the region. Strong subsidence and a surge of drier air wrapping around the mature cyclone will lead to rapid clearing sw-ne across the region Tuesday morning. The onset of sunshine will initiate mixing which will bring the stronger winds aloft toward the surface. Expect a period of wind gusts 30-35kts through mid afternoon. If the GFS winds verify, could see gusts 5-10kts stronger, possibly prompting the need for a wind advisory. The low level west-sw flow will maintain a warm air mass, delaying the onset of cold air advection. Based on this, have adjusted max temps upward a few degrees, ranging from the low-mid 60s nw to the lower 70s southeast. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... As of 340 PM Sunday... Dry weather is expected from mid to late week. A weak reinforcing cold front is expected to move through the area on Wednesday. Mid level ridging will return behind the departing system late week, with surface high pressure shifting offshore by Friday. This will lead to near normal temps through Friday, with temps increasing by the weekend as the mid/upper level flow becomes more amplified with the approach of the next system. The main surface low with the next system is expected to lift northeastward from the Central Plains to the upper MS Valley, while additional s/w energy will dig southeastward into the southern plains/base of the trough and shift eastward. This will allow for a good chance of showers and possibly some thunderstorms to occur across central NC as the surface front moves into the area on Sunday (showers possible as early as Saturday afternoon/night though, all liquid expected). Ahead of the front temps are expected to be above normal again, with well above normal values across eastern and southern portions of the area. Expect highs will be in the 50s and 60s, with possibly even a few 70s across the far SE. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... As of 630 PM Sunday... VFR conditions are expected to persist across all TAF sites through 06z tonight. A mid level SCT/BKN cloud deck could inch into KINT/KGSO during this time period, but CIGS should remain above 7KFT. After 06z, higher dewpoints should allow for fog formation, especially across the coastal plains. This will cause VSBY reductions a few hours before daybreak, with a few hours as low as IFR conditions possible. Confidence remains medium to low on location and timing of the BR. A cold front approaches from the west late in the period, with dropping ceilings to near MVFR likely. With confidence low, have kept CIGS VFR through 00z Tue with no weather impacts, but this may need editing if showers begin to overspread KINT/KGSO a bit earlier than expected. The chance for MVFR ceilings along with scattered showers will increase after 00Z Tuesday in the west, more so after 04Z. By 08Z, expect a high potential for MVFR/IFR ceilings and scattered to numerous showers across the bulk of central NC as a cold front approaches from the west. This boundary expected to sweep eastward across the area early Tuesday morning, leading to improving ceilings and diminishing the shower coverage west-to-east. In the wake of the front, a period of strong sw sfc winds expected with gusts 30-38kts possible. This wind threat should diminish/subside by mid-late afternoon Tuesday. VFR parameters anticipated Tuesday night through Friday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...Ellis SHORT TERM...WSS LONG TERM...BSD AVIATION...JJM/WSS is the U.S. government's official web portal to all federal, state and local government web resources and services.