Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS62 KRAH 060826
Area Forecast Discussion
National Weather Service Raleigh NC
325 AM EST Tue Dec 6 2016
Cool and wet conditions are expected today, ahead of a Miller B low
pressure system and associated cold air damming. An arctic cold
front will approach the area Wednesday night and cross the Carolinas
.NEAR TERM /THROUGH TONIGHT/...
As of 320 am Tuesday...
Deamplifying closed low over the Lower MS Valley will eject
northeast across the Carolinas this afternoon and off the southern
Mid-Atlantic Coast this evening. Miller-B low pressure system will
overspread the region, with the primary sfc low filling over the Tn
and Ohio Valley this afternoon as the secondary coastal low
currently developing off the SE coast deepens as it lifts up the NC
Strong low to mid-level warm moist advection ahead of the
approaching shortwave trough and associated developing coastal low
will result in widespread rain across the area this morning, and
will persist through lunch time when the approach of the upper
wave/trough could result in a more showery nature of precipitation.
Dry air aloft will begin to overtake the area between 18 to 21z,
which will lead to precip tapering off to drizzle before ending
across the area largely by 00z. By the end of the day, rainfall
amounts are expected to range between 0.50 to 1.0" across the area.
Still not impressed with thunder chances across Central NC with the
GFS and ECMWF only showing 100-200 J/KG of MUCAPE across the area
this afternoon with the approach of the upper wave and associated
cold pool with 6-6.25 C/Km lapse rates. Will leave out the mention
of any thunder.
Near steady temperatures across the Piedmont, possibly falling
slightly due to evap cooling once the steadier precip sets in. The
far eastern/southeastern zones could warm slightly(2 to 3 degrees)in
proximity to the warm front. Highs ranging from mid 40s NW to
lower 50s SE.
Low-level moisture could be slow to mix out tonight. However, in
areas that do clear out, wet soils could result in some areas of
fog, potentially dense in spots. Lows in the upper 30s to lower 40s.
.SHORT TERM /Wednesday through Thursday Night/...
As of 220 AM Tuesday...
Minimal drying will occur on Wed (in the wake of the low pressure
system progged to track offshore the Carolina coast tonight) as low-
level flow quickly backs to the south/southwest (giving rise to weak
warm advection) in response to upstream height falls as potent
shortwave energy ejects E/ENE from the Rockies toward the central
Appalachians and the leading edge of an arctic cold front progresses
eastward through the TN/OH valley to the western slopes of the
southern Appalachians by 12Z Thu. Low-level frontogenesis, glancing
DPVA, strengthening cyclonic flow aloft and lingering low-level
moisture are expected to result in the development of light
rain/sprinkles /anafrontal precipitation/ along and behind the
arctic cold front as it progresses through central NC during the day
Thu. 00Z ECMWF guidance has trended wetter compared to yesterday and
is in relatively good agreement with the 00Z GFS now, indicating
that a few hundredths of an inch of rain will be possible between 12-
18Z Thu, with the relative best chance of measurable precip in the
Northern Piedmont and NE Coastal Plain. Expect highs in the 50s on
Wed and lows in the lower 40s Wed night. Highs on Thu will depend on
fropa timing, timing/amount of precipitation and cloud cover. At
this time, will continue to indicate highs ranging from the upper
40s/lower 50s far NW to mid /upper 50s far S/SE. Lows Thu night will
highly depend on fropa timing and ensuing cold advection. Anticipate
lows ranging from the mid/upper 20s NW to lower 30s SE. -Vincent
.LONG TERM /Friday through Monday/...
As of 220 AM Tuesday...
Expect cold/brisk conditions on Friday with highs in the mid/upper
30s to lower 40s and a NW breeze assoc/w strong cold advection as
1040 mb arctic high pressure builds eastward from the central plains
toward the Appalachians in the wake of the cold frontal passage
Thu/Thu night. Expect cold lows in the upper teens to lower 20s Sat
morning as the arctic high settles over the Carolinas late Friday
night. Highs on Sat will be similar to Friday (albeit a few degrees
warmer). Forecast confidence decreases at the end of the weekend and
early next week as guidance diverges with regard to the onset of
southerly return flow /warm advection/ as the next cold front
approaches the mountains from the west and modified arctic high
pressure shifts offshore the Carolina coast. -Vincent
.AVIATION /06Z TUESDAY THROUGH FRIDAY/...
As of 115 AM TUESDAY...
24-Hour TAF period: Conditions will Deteriorate to IFR to LIFR
between 06 to 12z and should remain that way through the taf period
as rain overspreads the area ahead of Miller B low pressure system
and associated CAD. The low pressure system will lift northeast away
from the area during the late afternoon, allowing precip to taper
off from SW to NE across the area between 21 to 00z. However, IFR to
LIFR conditions in low clouds and possibly fog could persist well
into the overnight hours Tuesday night.
Finally, concerning LLWS, given little variation in directional wind
component between 1000-925mb along with recent guidance showing
sustained winds of 10 to 12 kts at KRDU, KFAY, and KRWI, have
removed the mentioned of LLWS from 06z terminal forecast.
Looking ahead: VFR conditions will return on Wednesday. However, sub-
VFR ceilings could return Wednesday night and linger into the day on
Thursday ahead of an arctic cold front moving through the area. &&