Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Raleigh NC
1255 PM EST sun Feb 14 2016
Synopsis...Arctic high pressure will extend across the area today.
A developing storm system will approach from the west tonight and
move eastward across the region Monday through Tuesday. High
pressure will gradually build in from the northwest Tuesday night
Near term /through Sunday/...
as of 955 am Sunday...
Very few changes are needed with the forecast this morning... mainly
a tweaking of today's highs and a slight slowing of the arrival of
cloud cover based on morning trends. High resolution guidance still
supports highs today from 29-36... coldest in the northeast beneath
the core of the Arctic surface ridge centered over far eastern Virginia...
despite plenty of sunshine for at least the first half of the day.
Middle clouds are projected to spread in from the west from late
morning through the afternoon... with most places mostly cloudy by
late afternoon. The forecast for the upcoming storm still looks on
track... and while we may see some returns on radar as soon as late
afternoon / early evening... these hydrometeors will initially be
fighting dry air near the surface and thus the forecasted onset of
measurable precipitation still looks good. We will be considering winter
weather advisories this afternoon... and perhaps a Winter Storm
Warning in the far northwest... after a thorough assessment of morning
model runs. -Gih
Here is the previous discussion from 4 am... today: modified surface
high pressure over the area this will begin to slowly slide eastward
towards the middle-Atlantic coast this evening... with middle and high
level cloud covering increasing ahead of the next system. Afternoon
low level thickness values are expected to be well below normal...
generally in the 1250s and 1260s. This combined with the increasing
cloud cover will lead to another cold day across the area... with
highs expected to be generally range from around 30 north/NE to near 35
Tonight through Monday night: surface high pressure will shift
offshore tonight... while low level moist advection will commence
over top the lingering cold dome leading to the develop of some
light wintry precipitation. Precipitation is expected to first develop
across the northern/northwestern Piedmont initial very late this
evening/after midnight tonight (generally in the form of light snow
to start)... then filling in further south and east during the early
morning hours of Monday. This will result in the development of an
insitu cad wedge.
While the precipitation will generally remain light tonight into Monday
morning... the cold surface airmass deposited by the modified Arctic
surface high will lead to all precipitation early Monday morning falling in
the form of a wintry mix... with more snow/sleet across the
northern/northwest Piedmont.... to more of a sleet freezing rain mix
across the far south/southeastern counties. Given the surface high
will be transitory (continuing to move further away and offshore)
coupled with a surging warm nose expect we will see precipitation go from a
wintry mix to freezing rain... then all rain in a southeast to
northwest fashion on Monday. Expect locations across our far
southern and eastern counties will be all rain/drizzle by around
noon Monday... with the Triangle area turning to all rain/drizzle by
middle afternoon or so...while The Triad may hold onto some light
freezing rain or drizzle into the evening... before becoming all
rain by late evening. Most of the precipitation by midday Monday is
expected to be quite light... as the 850mb warm front lifts to the
north of the area. This should leave central NC will spotty light
precip/drizzle. With respect to to accumulations. Locations across the northwest
Piedmont/northern Piedmont will see the highest snow and sleet
totals... possibly 2 to 3 inches... with locations farther south and
east seeing less for a number of reasons (a little less quantitative precipitation forecast/less
time with higher snow/sleet to liquid ratios due to the warm
noes/and possible loss of saturation above -10c across the far
south/southeast). Thus... outside of the northwest/north Piedmont we will
generally see snow/sleet totals of around an inch or less. With
regard to ice accrual... think we should see at least trace amounts
across all of central NC... thus... at least a Winter Weather
Advisory will likely be needed in later shifts for the entire area.
Ice accrual is expected to generally be a tenth of an inch or
less... with the highest totals across the Piedmont. After
coordination with surrounding offices we will keep the current watch
as is for now. However... as mentioned above at least a Winter Weather
Advisory will be need for tonight into Monday for the entire area...
with perhaps a Winter Storm Warning needed for a the far north/northwest
Piedmont. Lows tonight are expected be in the lower to middle 20s. High
temperatures Monday will range from the lower 30s northwest to the lower to middle
The main short wave energy and accompanying surface low are expected to
move through the area Monday night into Tuesday... with heavy rain
and possibly a few storms. Temperatures will increase ahead of the surface
low as the coastal front attempts to move inland. This will allow
for near steady to rising temperatures overnight... with lows for the
overnight period likely occurring at the start of the period. Temperatures
at around 12z are expected to be in the upper 30s northwest to the 50s southeast.
Short term /Tuesday and Tuesday night/...
as of 335 am Sunday...
Surface cold front attendant with the short wave crossing the middle Atlantic will
advance quickly eastward across central NC Tuesday morning. Numerous
showers ahead of this feature should quickly diminish west-to-east
through 17z. Westerly flow in the wake of this feature will also aid
to dissipate cloud coverage and lead to a fairly mild afternoon.
Afternoon temperatures should vary from the lower 50s northwest to the lower 60s
Another short wave will cross immediately north of central NC Tuesday
night...dragging a secondary cold front across our region. This
feature will basically be moisture starved though decent middle level
lapse rates may lead to a few sprinkles or light rain showers near
the Virginia border.
Long term /Wednesday through Saturday/...
as of 335 am Sunday...
Amplified l/west trough that has persisted over our region for much of
February will relax...leading to short wave ridging aloft by the end of the
week. This will lead to a deep zonal flow...initiating a return to
near normal and eventually above normal temperatures. Afternoon temperatures will
generally be in the 50s Wed-Fri. The approach of a surface cold front
from the northwest late Friday into Saturday will back the flow to a more
SW direction...pumping warm air residing over the deep south into
central NC. Afternoon temperatures Saturday should climb into the 60s
areawide. Overnight temperatures will generally be within a few degrees of
above freezing until late into the week when an uptick in cloud
coverage and a SW flow yields min temperatures in the 40s. Dry weather
expected through the period as moisture return will be characterized
Aviation /18z Sunday through Thursday/...
as of 1255 PM Sunday...
A period of wintry weather is expected starting this evening and
lasting through middle evening Monday... mainly affecting northern taf
sites (int/gso/rdu/rwi)... although accrual amounts should be fairly
light at rdu/rwi with only trace amounts at Fay.
VFR conditions hold at all taf sites currently. Clouds will thicken
this evening but remain VFR through 03z. After this time... between
03z and 08z... ceilings will lower to MVFR from southeast to northwest
(deteriorating first at Fay then at rdu/rwi and finally at int/gso).
During this period... areas of precipitation will spread in mainly
at int/gso... with much more light and patchy precipitation at rdu/rwi/Fay.
Initial precipitation type will be mostly snow or snow/sleet tonight...
changing to mostly freezing rain from southeast to northwest (first changing at
Fay then at rwi-rdu-gso-int in that order) Monday morning through early
Looking beyond 18z Monday... areas of precipitation should be all rain at
rwi/Fay by 18z... at rdu by 21z... and at gso/int by 02z (mid
evening mon). Ceilings Monday afternoon will drop to mainly IFR/LIFR with
MVFR to IFR visibilities... holding through midday Tuesday with a period of
widespread heavy rain expected late Monday night into Tuesday morning...
moving west to east. An isolated storm or two is possible early Tuesday
morning at rwi/Fay. VFR conditions are expected to return Tuesday
afternoon with a period of gusty winds from the west. VFR conditions
will then dominate through Friday as high pressure builds in. -Gih
Here are the record lows and record low maximum temperatures for
Rec yr rec yr
low low maximum
02/14 6 1905 22 1914
02/14 -2 1899 27 1916
02/14 12 1968 33 1916
Winter Storm Watch from late tonight through Monday evening for
Winter Storm Watch from Monday morning through Monday afternoon for