Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 142350

Area Forecast Discussion
National Weather Service Raleigh NC
648 PM EST Thu Dec 14 2017

A weak and dry surface cold front will stall south of the area
tonight. An area of low pressure will develop along the NC coast
Friday, then tracks northeast while staying offshore Friday night.
High pressure will build into the area through Sunday.


As of 648 PM Thursday...

Just minor adjustments made to the near term forecast, primarily to
the sky cover and hourly temperatures.

Westerly flow in the mid-upper levels of the atmosphere will
transport moisture ahead of a pair of upper disturbances into
central NC. This will translate to increasing high level clouds this
evening into the overnight. By daybreak, another layer of clouds a
few thousand feet above the surface will develop.

The increasing cloudiness should cause temperatures to cool a little
slower than normal. This is already evident where temperatures
across the far north are in the mid-upper 40s while locations across
the central part of the forecast area, where skies are clear, have
dipped into the upper 30s. Once the clouds arrive in these
locations, temperatures will likely recover temporarily to
around 40 then fall back through the 30s.


As of 253 PM Thursday...

The aforementioned low pressure wave will quickly lift to the NE
Friday morning as a northern stream short wave, currently over the
central Plains, moves east and sweeps across our area during the
afternoon.  As the wave departs and the short wave trough axis moves
across, dry NW flow will return in their wake, clear the sky out by
late afternoon.  Other than clouds early in the day, look for fair
weather with highs from the mid 40s NW to lower 50s SE.

Clear and cold Friday night with high pressure building over the
area, light or calm winds, and good radiational cooling conditions.
That should set us up for lows dipping down in the mid 20s...perhaps
even colder in the usual spots.


As of 247 PM Thursday...

Surface high pressure over the area will produce sunny skies with
slightly cooler than normal temperatures to kick off the weekend.
Highs Saturday will reach the upper 40s north to low 50s south
followed by lows at or slightly below freezing Saturday night. The
high pressure will edge offshore Sunday, with cloudiness increasing
in return flow and associated moisture advection along with low
amplitude ridging aloft on Sunday. The warm air advection and rising
heights will produce modestly warmer highs in mostly the mid and
upper 50s.

Skies will become cloudy with scattered showers Sunday night as a
series of waves begin to lift northeast into the area in deep
southwest flow off the Gulf. The low amplitude ridge will linger
through Tuesday, providing a conveyor for these waves and associated
periods of enhanced shower activity. As we remain in the warm and
moist airmass through the period, highs will be similar both Monday
and Tuesday, ranging from upper 50s north to low and mid 60s south.
Very difficult to forecast how much rain we might get given the
duration of the event and model difficulties with timing and
strength of the waves.

A strong but relatively flat short wave in the northern stream
moving across the Tennessee and Ohio Valleys will push a cold front
east, effectively cutting off our moisture Tuesday night. The upper
flow is basically zonal and the high pressure building in behind the
front is only modestly colder than the air it is replacing, so highs
will take only a mild hit Wednesday and Thursday...mostly in the low
and mid 50s.


As of 648 PM Thursday...

VFR parameters should persist across central NC through 08Z. After
08Z, chances will increase for the potential for a deck of stratus
to develop with MVFR ceilings 1500-2500ft probable. This deck of
ceilings expected to persist until mid day, then gradually dissipate.

There is a high chance that VFR parameters will occur Friday night
through Sunday morning. The next threat for sub VFR parameters is
expected late Sunday into early next week as a low pressure system
approaches from the west-sw.




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