Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 161428 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1030 AM EDT Mon Apr 16 2018 .SYNOPSIS... A deep upper level low over the lower Great Lakes will produce blustery and cool conditions across central NC today and tonight. An area of high pressure over the northern Gulf will drift eastward Tuesday and Wednesday. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1030 AM Monday... A much drier but still somewhat unsettled day ahead. We`ve see a few light showers rotate through northern sections of the CWA this morning, in response to waves of DPVA rotating around the large/deep mean mid level trough/low and oriented along one of several surface troughs pinwheeling around the low over the Northeast. These showers have mostly lifted northeast and out of the area, on pace with RAP output. A lull in shower chances is expected until late afternoon, when another vorticity max swinging through the trough base over the Carolina should spur development of another round of isolated showers, mainly across southern and eastern sections, late afternoon into early evening. Winds will remain blustery with frequent gusts into the afternoon, although the MSLP gradient over NC will slacken a bit today. The 25-35 kt 925 mb winds will diminish to 15-20 kts for awhile through mid afternoon, but will strengthen again to 25-35 kts toward evening, so the occasional gustiness should persist into this evening, as we should remain mixed. Have gone slightly under guidance for highs with the periodic cloudiness and cold air advection today, 58-65. -GIH Earlier discussion from 330 am: 06Z meso analysis depicts a sfc low in proximity of Danville, VA with a trailing sfc cold front extending from the low across central NC. West-SW flow behind the boundary advecting a drier air mass into our region has evidence by sfc dewpoints in the 40s across the southern Piedmont and western Sandhills versus dewpoints in the 60s across the coastal plain and northeast Piedmont. This sfc boundary projected to lift newd and exit our northern coastal plain counties by sunrise. A sfc trough extending from the sfc low will cross central NC later this morning and through the afternoon. As the atmosphere destabilizes later today due to heating, lift along this boundary interacting with available residual moisture may produce a few showers. Aloft, a deep upper level low will drift ewd across the lower Great Lakes today and tonight. Weak perturbations in the cyclonic flow around this feature will cause periods of cloudiness across our region through this tonight. The westerly low level flow will advect a cooler air mass into central NC as the 850mb thermal trough will lie immediately west of our region. This should result in a lower than normal diurnal temperature recovery, with high temperatures later today about 10 degrees warmer than early morning lows. Tonight, the 850mb thermal trough settles overhead. The cool dry air mass will yield overnight temperatures in the mid-upper 30s. Potential for spotty light frost over portions of the Piedmont though a light westerly sfc wind and a relatively dry air mass may inhibit frost from developing. Will refrain from mentioning patchy light frost for now though if it appears that the sfc wind will decouple, a frost advisory would be necessary for sections of the Piedmont.
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&& .SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/... As of 330 AM Monday... Relatively quiet weather pattern for much of the work week. The deep upper level low over southern New England early Tuesday lifts nwd. This will subside/abate the cyclonic flow over our region. A sfc high to our south-southwest Tuesday will drift eastward and be off the FL peninsula by Wednesday. This will turn our low level flow to a more swly direction, advecting a warmer air mass int our region. Thus, after highs Tuesday in the low-mid 60s, highs Wednesday will jump well into the 70s to around 80. A sfc cold front associated with a s/w crossing the northern Mid Atlantic , will drop across central NC late Wednesday night through Thursday morning. The frontal passage will be pretty much uneventful as the atmosphere appears too dry and stable to support anything more than a few clouds. The cooler air associated with the front will likely not take hold of our region until later Thursday, behind the passage of the 850mb trough. Thus, it will remain mild over most of the region Thu with afternoon highs ranging from the lower 70s NW to around 80 southeast. Overnight temperatures through the period will vary as well with 40s expected Tuesday night, mild 50s Wednesday night ahead of the front, and cooler 40s anticipated Thursday night. Finally, the difference in sfc pressure between the high off of the Southeast U.S. and an area of low pressure to our north will maintain breezy conditions. Expect wind gusts 20-30 mph Tuesday through Thursday. These breezy conditions along with low afternoon relative humidity may result in slightly elevated fire danger parameters. && .LONG TERM /FRIDAY THROUGH SUNDAY/... As of 255 AM Monday... The upper-air pattern on Friday morning will feature a trough with an embedded closed low over New England with another trough and closed low over the four corners area with narrow ridging in between. Central NC will experience a northwest flow aloft for Friday and most of Saturday which typically features cooler than normal conditions and a generally dry pattern. At the surface, high pressure centered over the upper Midwest on Saturday will shift east in the northern Great Lakes on Saturday as it extends into the region. The result for Friday and Saturday will be dry weather, mainly clear skies, and temperatures generally about 5 degrees cooler than average. Confidence decrease significantly when the pattern begins to change on Sunday as the closed low over the southern Rockies shifts east into the southern Plains and the ridge axis moves over the Carolinas. Not surprisingly, NWP guidance is struggling with the handling of the closed low. The operational GFS moves the system eastward faster than the EC but the available ensemble means are in closer agreement and provide a middle of the road compromise. Will follow the compromise for now and keep the forecast dry for Sunday morning with a chance of rain Sunday on afternoon and Sunday night, especially across the south and southwest. Given the placement of upper low and the surface reflection, central NC is currently progged to be on the cooler and more stable portion of the storm system. Morning lows on Sunday will range in the mid 40s with highs in the mid 60s to around 70. -Blaes && .AVIATION /12Z MONDAY THROUGH FRIDAY/... As of 740 AM Monday... While aviation conditions will improve southwest-northeast across central NC this morning, a series of perturbations in the cyclonic flow aloft will result in periods of cloudiness through tonight with a few isolated showers possible. Expect ceilings bases to gradually lift through the morning hours, then hover between 3500-5000ft this afternoon. It will remain blustery with frequent gusts in the 25- 30kt range through late this afternoon. While VFR parameters will dominate through the work week, it will remain quite breezy for this time of year with wind gusts in the 20- 25kt range expected each day Tuesday through Thursday. A dry cold front will cross the region late Wednesday night into Thursday morning with just a smattering of clouds anticipated with the frontal passage at this time. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...Hartfield/WSS SHORT TERM...WSS LONG TERM...BLAES/Ellis AVIATION...WSS

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