Area Forecast Discussion
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FXUS62 KRAH 191633
Area Forecast Discussion
National Weather Service Raleigh NC
1132 AM EST Thu Jan 19 2017
An upper level trough over the Tennessee Valley this afternoon will
pivot northeast over western North Carolina into Virginia tonight
and Friday. This will be followed by a brief quiet period Friday
afternoon and night. Then... a strong storm system is expected to
affect the region over the weekend into Monday.
.NEAR TERM /THIS AFTERNOON THROUGH TONIGHT/...
As of 1132 AM Thursday...
The cooler and drier air mass was in place over the region courtesy
of the surface high pressure. The latest data indicated mostly sunny
to sunny skies. Satellite and surface observations support sunny
skies becoming partly sunny in the west later today. Highs are still
expected to reach the upper 50s to lower 60s with light and variable
Cloud cover will begin continue to increase from the southwest this
evening as a southern stream system approaches. Rain chances will
increase for the SW Piedmont after 06z, and spread northeast
overnight. QPF of around 0.25 NW to less than 0.10 expected SE.
Lows in the mid 40s to near 50.
.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
As of 335 AM Thursday...
Rain will continue across central NC on Friday as a disorganized
frontal system moves across the area. Rain will continue into the
late afternoon or early evening ending from west to east as it does
so. Total accumulations of rainfall are expected to be somewhere in
the neighborhood of a tenth to a quarter of an inch. Temperatures
will be dictated by cloud cover but warm air advection ahead of the
system will bring max temps up into the mid 60s across the south,
with upper 50s to low 60s across the north. Lows Friday night in the
upper 40s to low 50s.
.LONG TERM /Saturday through Wednesday/...
As of 340 AM Thursday...
A wet and somewhat stormy pattern will reach a crescendo late Sun
through Sun night as a powerful mid level low and mature surface
frontal system impact the region. A drier and quieter weather period
will begin late Mon and last through Wed.
Sat/Sat night: A subtle mid level wave will sweep NE through the
region, accompanied by a slug of upper divergence in the nose of a
weak southwesterly low level jet. With PW surging well up above
normal, this forcing for ascent should have no trouble producing
showers over NC, most numerous across the S and E. A brief lull will
follow late Sat afternoon into the evening, however the approach of
another stronger perturbation from the SW and an even stronger and
extensive low level jet nosing in from the south will prompt a
return to widespread rain late Sat night. Highs in the low-mid 60s
and lows in the mid-upper 50s with cloudy skies.
Sun through Mon night: Widespread rain should be ongoing early Sun,
fueled by the aforementioned wave, strong low level mass
convergence, and another batch of vigorous upper divergence
associated with an upper jetlet on the SE side of the digging low
over the Gulf States. This should be followed by yet another short
lull in precip coverage and intensity early Sun afternoon, before
the powerful mid level low tracks east then northeast across GA and
the Carolinas through Mon, bringing numerous showers and storms,
peaking Sun evening and night before tapering from south to north
Mon as the dry slot wrapping around the low punches in from the
south. An uptick in shower coverage is possible Mon afternoon as the
core of the mid level low and attendant steep lapse rates drift over
the region. Rapidly rising heights as the low shifts to our NNE will
induce drying and an end to precip Mon night. A few strong storms
remain possible from mid afternoon Sun through Sun evening, with a
70-90 kt mid level jet streak accompanying the powerful upper
divergence and steep 700-500 mb lapse rates, topping 7.5 C/km
according to the GFS. Timing will be crucial, as the ECMWF is up to
12 hrs faster than the GFS with the arrival of the mid level low.
CIPS analog guidance at this range hints at a greater threat for FL,
historically speaking, but GFS forecast soundings for central NC
showing lengthy wavy hodographs and moderate instability support at
least a modest risk of severe storms in our area, including a
tornado risk along and north of the occluding frontal system. Highs
in the 60s to near 70 Sun, lows from the upper 40s to mid 50s Sun
night, and upper 50s to mid 60s for highs Mon. Lows in the 40s Mon
Tue through Wed: Mid level heights rise over the Southeast as a mid
level ridge axis shifts over the region, while surface high
pressure crosses the northern Gulf and FL. Expect fair skies with
slightly cooler but still above normal temps. -GIH
.AVIATION /18Z TODAY THROUGH MONDAY/...
As of 1130 AM Thursday...
VFR conditions will continue through 06Z/tonight. Ceilings will
begin to lower from the SW later this evening and overnight. MVFR TO
IFR conditions expected with areas of rain and fog between 09Z-
15Z/Friday. The rain is expected to end by late morning, with a
return to MVFR then VFR conditions during Friday afternoon.
Long term: VFR conditions will continue into Friday night. However,
a warm front will approach late Friday night and Saturday. This will
bring IFR to MVFR conditions Saturday with areas of rain and fog.
Another system will bring adverse aviation conditions with rain,
fog, low ceilings, and thunderstorm chances Saturday night through