Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 181138

Area Forecast Discussion
National Weather Service Raleigh NC
638 AM EST Sun Feb 18 2018

A weak cold front will continue to cross our region this morning.
High pressure will build into the area this afternoon, then quickly
drift offshore later tonight.


As of 330 AM Sunday...

GOES-16 1-minute infrared satellite imagery shows continued
orographic enhancement along the back edge of the cloud cover. This
is supported by the 00z observational soundings with a strong low
level inversion and unidirectional flow out of the southwest
increasing with height. While northwesterly would be the optimal
flow for orographic enhancement, southwesterly flow cases are well
documented and not unusual. Forecast soundings show extremely dry
airmass aloft that will eventually penetrate to the surface and
clear things out but that might not be until 15z or so. Until then
expect low ceilings and reduced visibilities. Once clearing occurs
expect winds to gradually swing around to northeasterly by this
afternoon. Despite the northerly component to the winds most of the
day, insolation will be plenty and temperatures will rise back into
the upper 50s to mid 60s, quite a bit warmer than yesterday.

After 00z this evening expect clouds to start filling back in from
the southwest. Pops will begin to increase in association with
another shortwave expected to move through early Monday morning with
showers possible as it does. Lows in the 40s with lowest temps in
the northeast.


As of 330 AM Sunday...

After the shortwave moves out on Monday morning, central NC will
enter an extended period of summer like conditions with a strong
Bermuda high in place bringing southerly return flow and warm air
advection to the area. While it may take a CAD wedge a little while
to break down, southern locales will see high temperatures pushing
the 70 degree mark by Monday afternoon. The airmass will be fairly
moist with dewpoints in the upper 50s across the south. If the wedge
scours out sooner, temperatures in the Triad could be underdone. As
is the case with moist southerly return flow, pockets of showers
will be possible throughout the day on monday but largely
inconsequential. Lows Monday night will be quite a bit more
moderate, only reaching the low to middle 50s.


As of 257 AM Sunday...

A 595 ridge centered off the SE coast and resulting warm southerly
flow over our area will give us unseasonably warm conditions during
the middle of the week, with perhaps some record highs. This ridge
will flatten and shift south during the latter half of the week,
which will allow a cold front to approach from the north (perhaps in
backdoor fashion) on Thursday, dropping southward to roughly the I-
85 corridor.  Thereafter, model solutions diverge regarding whether
the front pushes all the way through our CWA on Friday per the GFS,
or lifts back north early Friday per the ECMWF.  Either way, it
appears that low-end PoPs will be needed for at least the northern
half of our CWA for late Wednesday through Thursday.  Thereafter, if
the front lifts back north on Fri per the ECMWF, that would result
in a drier forecast for Fri and Sat.  However, if it pushes through
on Fri then lifts back north on Sat per the GFS, that would result
in lingering rain chances both days.

As for temps...There`s decent agreement in the guidance through at
least Thursday with thickness profiles, which suggest highs in the
upper 70s to around 80. Readings this warm would break some high
temp records Tue, Wed, perhaps Thu. (see climate section below).
Overnight lows in the 50s to around 60 will also come close to
record warm lows.


As of 635 AM Sunday...

24 Hour TAF Period: Orographically enhanced cloud cover has hung on
longer than expected this morning but fog is starting to clear the
Triad at this time. Some pockets of patchy dense fog will remain
through 15z but will give way to clear skies. After fog dissipates,
the main story will be the wind direction as winds will gradually
swing around to northeasterly by this afternoon. Some gusts to 15
kts will be possible, particularly in the south. MVFR ceilings may
creep into the southern areas by the end of the TAF period.

Long term: Another shortwave will move through Sunday night
presenting a good chance of sub-VFR conditions and precipitation. A
frontal zone will reside northwest of the area for much of the work
week and could present some problems for aviation conditions in the
Triad on Thursday before the front sinks south for next weekend.



RDU Records:

Date     |  High  Year  |  High Min  Year
02/20       75    1939        62     1939
02/21       76    2011        55     1939
02/22       75    1897        60     1897
02/23       79    1980        57     1962
02/24       81    1982        58     1985

GSO Records:

Date     |  High  Year  |  High Min  Year
02/20       74    1922        56     1939
02/21       74    2011        50     1954
02/22       74    1925        57     1980
02/23       74    2017        52     1922
02/24       79    1982        55     1985

FAY Records:

Date     |  High  Year  |  High Min  Year
02/20       82    2014        60     1939
02/21       80    1991        61     1953
02/22       77    2003        56     1989
02/23       80    1922        55     1922
02/24       83    1930        60     1975




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