Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 220711 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 211 AM EST Mon Jan 22 2018 .SYNOPSIS... High pressure will drift offshore this morning, and subsequently allow a warm front to retreat north across the southeastern U.S. today. The warm front will lift across NC and VA tonight, immediately ahead of a lead cold front that will cross the region on Tuesday. A secondary cold front will follow and cross the region Tuesday evening. && .NEAR TERM /THROUGH TONIGHT/... 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. && .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 MONDAY/...
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As of 210 AM Monday... Expect dry weather through Friday night. An upper level shortwave and a reinforcing dry cold frontal passage is expected Wednesday night/Thursday. Surface high pressure is expected to build into the area in the wake of the secondary cold front and remain over the area into Saturday. The upper level ridge will move eastward over the Carolinas through Friday night. Another upper level trough and surface cold front will develop over the Midwest and progress eastward toward the Mid-Atlantic over the weekend. As southwesterly flow increases, so will the warm, moist advection into the region. As a result, cloud cover and chances for precipitation will increase late Saturday into Sunday as the cold front approaches. As of the latest forecast cycle, the front progresses through Central NC by Sunday night, with cool high pressure building in behind it. Highs will be generally in the upper 40s north to mid 50s south through Friday and lows in the upper 20s to low 30s Wednesday and Thursday nights. Temperatures will moderate through Sunday, cooling down once again in the wake of the front.
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&& .AVIATION /06Z MONDAY THROUGH FRIDAY/... As of 110 AM Monday... The exception to VFR conditions through the first 12-18 hrs of the TAF period will be a chance of radiation fog at RWI, FAY, and RDU in the few hours centered around 12Z this morning. Otherwise, high pressure now over ern NC will drift offshore later this morning. The flow around the high will allow a warm front and associated leading edge of more humid/moist air to surge into cntl NC from south to north between 22Z-06Z. A lead band of 2500-4000 ft stratocumulus will accompany the warm front; and this may result in an MVFR ceiling and a widely scattered shower around FAY as early as 22Z. Sly flow will strengthen, particularly just above a shallow layer of stability near the surface, to around 40-45 kts at 1500 ft late this evening; and this will result in both the newd development of widespread 500-1500 ft ceilings, and low level wind shear conditions, between 02Z-06Z. Outlook: The above-referenced IFR-MVFR conditions will persist until a cold front, and preceding axis of showers and even a few thunderstorms, cross cntl NC from west to east on Tue. A subsequent return to VFR will result behind the cold front, generally between 12Z-15Z at Triad sites and around 18-20Z at ern ones. A very breezy swly wind will also develop behind the front, with gusts between 25 and 35 kts probable for at least a few hours on Tue. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...Ellis SHORT TERM...WSS LONG TERM...KC AVIATION...MWS

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