Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 180206

Area Forecast Discussion
National Weather Service Raleigh NC
1005 PM EDT Thu Aug 17 2017

A trough of low pressure at the surface will extend across the
Piedmont of Virginia south into the Carolinas through Friday. A cold
front will move across the area from the west late Friday into
Saturday and then stall along the Carolina coast on Sunday.


As of 1005 PM Thursday...

00Z upper air analysis depicts a weak zone of speed convergence
exists between 850mb-500mb immediately west of central NC. This
region of lift interacting with available moisture may trigger
isolated convection overnight across central NC. This threat appears
a bit higher over our western counties versus east. With
precipitable water values around 2 inches in the west, any
showers/storms will be efficient rain producers, dumping locally
heavy/excessive rainfall. In addition, steering flow rather weak at
10kts. Otherwise, expect a mixture of clouds/stars until 08Z when
areas of low clouds or fog will begin to develop, especially in the
coastal plain. Muggy, with overnight temps in the mid-upper 70s.


As of 345 PM Thursday...

Short wave ridging across the Carolinas will give way to falling
heights as a short wave trough dives from the upper Midwest
into the Ohio Valley by late friday night. The associated cold
front will approach the southern Appalachians friday morning
and then move across central NC Friday night reaching the
coastal region of the Carolinas on Saturday morning. Another
convectively active day is expected on Friday with widely
scattered showers and storms expected to develop around midday,
especially across the eastern Piedmont and Coastal Plain. Some
of the higher resolution convection allowing models suggest that
the majority of the convection will be attendant to the surface
front and will move into the RAH CWA from the west late in the
afternoon and then move southeast across the area during the

It will remain humid on Friday with dew points in the lower to
mid 70s which combined with highs of 89 to 95 will result in
heat index values of 100-105. Dew points today over performed
and were in the upper 70s across the Coastal Plain and if that
occurs again, a heat advisory would be needed. Will hold off for
now and defer to the mid shift to issue any headlines.

As of 341 PM Thursday...

A short wave trough axis will cross the area during the day and
evening Saturday, thus a few scattered showers may reform along the
stalled front near the best chance for rain on Saturday
and Saturday evening will be east of I-95. Any showers over our area
should end shortly after sunset with dry conditions Saturday night.

Sunday looks mostly dry as ridging aloft to our south begins to
build northward over our area.  Then for Monday, the forecast has
been trending better the past few model runs, regarding cloud
coverage and rain chances, although we`re keeping an eye on the weak
short wave in the westerly flow aloft, which both the GFS and ECMWF
suggest will pass by mostly to our north, but heights over us do
trend down during the day.  For now will hold cloud coverage around
50% with PoPs slightly below climo...20-30% during the afternoon

The pattern for the rest of the long term period will feature a
deepening through over the East, so look for mostly diurnal chance
PoPs each day Tue-Thu.

Temps Sat-Mon will run a couple degrees above normal with a building
ridge, then falling back to or below normal mid-late next week with
the deepening trough.


As of 840 PM Thursday...

24 Hour TAF Period: VFR conditions are generally expected to
continue this evening, with a small chance of a shower and/or storm
at KGSO/KINT. Another rounds of sub-VFR fog and/or stratus (low end
MVFR to IFR/LIFR) is again expected across eastern portions of the
area early Friday morning, possibly lingering until mid morning.

A cold front will approach the area from the west Friday, with an
associated band of showers and storms expected to move into the
region late in the day. Thus, have included mention of storms at
KGSO/KINT late in the day (from 20Z onward in a prob30 group).
Further east we may see showers and storms initially develop along a
surface trough located across eastern portions of central NC during
the early to mid afternoon, before another round of storms
potentially affects eastern portions of the area on Friday
evening/early Saturday morning.

Outlook: The aforementioned cold front will shift southeast on
Saturday and Sunday with any isolated to scattered diurnal
convection expected to generally be south and east of the area
(with a small chance at KFAY each day).




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