Chapel Hill, North Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

427
FXUS62 KRAH 180840
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
340 AM EST Fri Jan 17 2025

.SYNOPSIS...
Milder air will continue over the region into Sunday. However, A
strong Arctic cold front will cross the area from the west Sunday.
Arctic high pressure will then bring bitterly cold air into the
region through the middle of next week.

&&

.NEAR TERM /TODAY AND TONIGHT/...
As of 340 AM Saturday...

...Spotty light rain through midday with rain chances returning
tonight...

Lead southern stream shortwave, that`s currently over eastern TN,
will become increasingly sheared as it ejects east through the
region through midday. Following closely on the heels of the lead
shortwave, another shortwave trough diving through the base of the
long wave trough will approach the southern and central Appalachians
late tonight.

Modest southerly moisture transport is underway. Clouds have filled
in nicely across the area, but the lowest 10kft of the atmosphere
remains quite dry and it will take a few hours the column to moisten
before rain reaches the ground. Have slowed down the onset of precip
until right around daybreak across the western Piedmont. The
freezing surface wet-bulb temps have already lifted to the  Va, so
do not expect any frozen precip, just rain.

Energy transferal to a developing low pressure center off the SE
Coast will result in a significant reduction in QPF inland over the
Carolinas. Spotty light rain will spread east across the areas
between 12 to 20z with latest QPF trends indicating only a few to
several hundredths of an inch.

As the lead shortwave trough pushes east of the area and the coastal
low moves further out to sea, an afternoon and evening lull in
precip looks probable. Forecast guidance still suggests we could see
a few peeks of afternoon sun. However, clouds could quickly fill
back in with models suggesting that low clouds could quickly spread
in from the SW through the afternoon, which could curtail heating.
Guidance has trended slight cooler. Highs ranging from around lower
50s across the northern Piedmont to mid 50s.

Rain chances will increase after midnight, with spotty light rain
once again overspreading the area from the SW  owing to renewed lift
associated with the next shortwave trough and attendant complex
frontal zone and weak cyclogenesis over the region. No p-type
concerns with precip falling as all rain. Areas of fog is also
looking probable overnight, potentially dense in some spots. Lows
ranging from upper 30s north to mid 40s south.

&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 340 AM Saturday...

...Widely scattered rain showers through the afternoon with Arctic
air arriving late Sunday...

The next shortwave trough diving SEWD through the base of the deep
long wave trough will provide a glancing shot of moisture and lift
across the area. As the subtropical and polar jet streams converge
and strengthen over the region, the incoming cold front will
temporarily slow down/stall with a weak area of low pressure developing
over the Carolinas Sunday morning. The front will progress slowly
east and offshore during the evening with the low deepening as it tracks
up the mid-Atlantic coast.

The better rain chances look to occur overnight/early morning hours,
followed by multiple rounds of widely scattered rain showers through
the afternoon, limited in coverage and QPF amounts due to
entrainment of mid-level dry air.  The drying aloft will also
significantly decrease chances of ice in the cloud to support a
change-over to snow across the northern counties during the late
afternoon/early evening as the Arctic air pours into the area. Thus,
will not carry any snow accumulations.

Highs Sunday will depend on the actual timing of the frontal
passage. However, given the slowness of the passage, expect a large
temperature gradient across the area, ranging from mid/upper 40s
north to lower 60 SE. Temperatures will crash from NW to SE during
the afternoon and evening as the frigid Arctic airmass begins to
pour into the area. Skies will clear out overnight with lows ranging
from middle teens in the NW Piedmont to lower/mid 20s SE.


&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 300 AM Saturday...

On Monday morning, strong high pressure will be centered over
Montana and extend southeast all the way into Florida. Monday will
be a sunny but sharply colder day. Highs on Monday will be anywhere
between 20 and 25 degrees colder than Sunday and will only reach the
mid 20s to the upper 30s. Clouds will begin to increase Monday
night, and slightly greater cloud cover is the primary reason that
Monday night`s lows have come up ever so slightly from the previous
forecast - while teens are still forecast, single digit lows have
been removed from the forecast.

Focus then shifts to the storm that will develop in the Gulf of
Mexico Tuesday, cross Florida, and move up the Atlantic shoreline
Tuesday night into Wednesday. Over the last several days, the
European ensemble has consistently been the farthest northwest
(inland) with precipitation, and while that remains the case, the
deterministic European, GFS, and GEFS have all shifted precipitation
farther to the northwest now as well. There is rather good agreement
now that Tuesday night will be the period with the greatest
precipitation, and considering the cold temperatures that will be in
place, the precipitation would be all snow. Have bumped up pops to
likely Tuesday evening generally along and east of the US-1
corridor, but we do not produce snowfall accumulation forecasts that
far out. Some snow could linger Wednesday morning, but conditions
should be dry by Wednesday afternoon. Temperatures Tuesday, Tuesday
night, and Wednesday should be similar to the Monday and Monday
night period, with highs ranging from the mid 20s to the mid 30s and
lows in the teens.

As low pressure moves over the Atlantic Ocean, there should be a
brief respite from precipitation as high pressure becomes centered
over the mid-Atlantic states by Thursday morning. The ECMWF and GFS
both show yet another system developing off the Southeastern coast,
and vary in timing and how far inland precipitation will spread. The
GFS is quicker and gives more of a glancing blow to the eastern half
of the state Thursday and Thursday night, while the ECMWF is slower
(Thursday night and Friday) and is much farther inland with its
precipitation. While there will be some moderating of temperatures
from the first half of the week, the high to the north will still
have cold air in place before the precipitation and allow for
another round of snow mixing with rain. Won`t get too cute with
details for now, but do have chance pops approximately east of US-1.
Highs will be in the 30s on Thursday and in the 40s on Friday, with
lows in the mid teens to mid 20s Thursday night.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
As of 1250 AM Saturday...

Clouds will thicken from west to east overnight and will lower to 5-
10 kft by 12z as precip spreads in from the west. Spotty light rain
will overspread the area between 12 to 18z, before exiting.
Conditions are expected to remain predominately VFR as the rain
moves through the area. A lull in precipitation is expected during
the remainder of the afternoon and evening, during which time
ceilings are to lower to IFR and eventually LIFR overnight.
Additionally, areas of fog, potentially dense, will be possible as
an area of low pressure and occluded front lifts into the area.

Light S-SWLY winds of 5-10 kts are expected today, with some brief
gustiness of 15-20 kts possible, though confidence is low if these
gusts will materialize.

Outlook: Widespread IFR to LIFR restrictions will linger through
midday midday Sunday as a cold front and associated scattered rain
showers move through the area. Conditions will improve and
eventually return to VFR from SW to NE during the afternoon and
evening. Additionally, precip could end as a brief changeover to
snow across the northern TAF sites late Sunday afternoon and
evening.

VFR conditions are expected Monday and Tuesday. Forecast
uncertainty is high, however a potential winter storm system could
bring sub-VFR restrictions in snow Tuesday night/early Wednesday.


&&

.CLIMATE...

Record Low Maximum Temperatures:

January 20:
KGSO: 29/1983
KRDU: 28/1970

January 21:
KFAY: 31/1983

January 22:
KGSO: 29/2014
KRDU: 27/1970

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...Badgett/CBL
NEAR TERM...CBL
SHORT TERM...CBL
LONG TERM...Green
AVIATION...CBL
CLIMATE...RAH