Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Raleigh NC
145 am EDT Sat Oct 25 2014
Synopsis...high pressure will build over the Gulf states and
southeast through the weekend. This high will shift east and
offshore early next week... bringing a mild southwest flow into the
region with above normal temperatures.
Near term /today through Sunday night/...
as of 145 am Saturday...
For today/tonight: continued dry with lots of sunshine. A strong
upper level vorticity maximum will push southeast off the SC/Georgia coast this
morning... leaving behind rising heights aloft as weak shortwave
ridging pushes in from the SW... while surface high pressure noses
in also from the SW. Forecast soundings and upstream conditions
including water vapor imagery support deep dry air over NC today
with stable middle levels. Plentiful sun and thicknesses near to
slightly above normal will support above normal highs of 72-76.
Strong vorticity diving through the Great Lakes/northeast through
the base of a low crossing southeast Canada will help push a cold front
(now over the midwest) to the southeast toward NC tonight. Surface
flow from the west or west-southwest will pick up a bit with the tightening
mslp gradient... however the front itself should hold north of the
NC/Virginia border overnight. Models indicate a shallow pocket of moisture
from 850-750 mb dropping southeast through NC associated with weak trough
passage at this level... however the downslope nature of the low
level flow will limit cloud cover... and expect mostly clear skies
for the large part of tonight. Slightly stirred near-surface air
along with higher dew points south of the front should keep temperatures up
overnight... and expect lows of 45-50.
For sun/sun night: dry air through the column and stable middle levels
will persist over NC. The middle level low over New England and
extending down through the midatlantic coast early in the day will
move into the Canadian Maritimes and lift NE away from our area Sun
afternoon and night. Models show the front dipping southward into NE
NC sun... however The Dip in low level thicknesses should be
marginal and be confined to far northern and NE NC. In fact...
thicknesses over the southern County Warning Area should be several meters higher sun
than Sat. Expect highs in the middle to upper 70s... perhaps touching
80 in the SC border counties... with sunny skies. Surface high
pressure will build over the forecast area from the west Sun
night... and the calming air and cloud-free skies will facilitate
good radiational cooling... favoring lows a tad below normal...
Short term / /...
as of 1230 PM Friday...
To be updated shortly.
Long term /Monday through Friday/...
as of 302 PM Friday...
Warm and dry conditions can be expected through Wednesday... then a
backdoor front should bring clouds and cooler conditions Wednesday
night and Thursday. A stronger cold front should push southeast through the
region Thursday night bringing cooler air Friday.
Upper ridging will build from the plains eastward to the Atlantic
Seaboard through Tuesday. Rising heights aloft with a mean westerly
flow mean drying and warming for central NC. Highs should push or
surpass 80 over the sandhills and possibly the eastern and southern
Piedmont into the coastal plain Monday... then should maximum out
Tuesday in the lower to possibly some middle 80s. These readings should
be close... but not quite at the daily records for October 28...
which are 86... 86... and 87 at gso... rdu... and Fay (all recorded
Slight cooling will begin mainly because of the cloudiness expected
to increase out ahead of a cold front Wednesday afternoon. Highs
should still reach well into the 70s and possibly 80 again in the
south central and southeast zones Wednesday with the SW flow at 10-15 miles per hour.
The wind is expected to shift to the north-northeast Wednesday night into
Thursday with the passage of the "backdoor" front. Caution is
advised on the extent southward that this front will make it given
the model forecasts of a fairly "weak' surface high pressure to push
the front southward... down the eastern Seaboard. Current
projections indicate the front may stall west to east across NC...
and this may be too far south if the current models verify with the
lack of push of cold air advection with the 1016-1017 mb high pressure behind the
Regardless... the lack of deep moisture should prevent significant
rain along this front... and it should retreat back northward
quickly Thursday afternoon or night as a new storm tracks near the
Great Lakes. This mean storm track well to our north will drive
another stronger cold front southeast across the Appalachians and NC late
Thursday night and early Friday. However... only scattered showers
are currently anticipated with the front with the main storm track
well to our west and north. A push of cooler and drier air should
follow the front... but temperatures should remain near normal even behind
this front as the cold Canadian air will not get pushed to our
Aviation /06z Saturday through Wednesday/...
as of 1255 am Saturday...
High confidence that VFR conditions will dominate through tonight. A
strong upper level disturbance will push off the SC/Georgia coast early
this morning... and surface high pressure centered to our southwest
will nose northeastward over NC today into tonight. Very dry air
from the low levels on up will minimize cloud cover... and only
scattered to briefly broken clouds based above 6 000 feet above ground level are
expected from middle evening until shortly after midnight as a dry cold
front approaches NC from the north. The one exception: we are
watching out for potential shallow patchy fog mainly affecting rwi
early this morning between 09z and 13z. But at this time the
potential looks too low to include in the terminal forecast at this
time. Winds will remain very light... coming from a SW/W/NW
direction under 6 kts today... before becoming light mainly northwest
Looking beyond 06z early Sun morning... patchy shallow fog is
possible again at all sites 09z-13z sun... but otherwise VFR
conditions will dominate through Wednesday... with initial dry flow
aloft from the northwest transitioning to a building middle level ridge over
the southeast states through early next week. -Gih