Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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799
FXUS62 KRAH 261046
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
646 AM EDT Wed Apr 26 2017

.SYNOPSIS...
A shortwave ridge will build eastward over the Carolinas this
afternoon into tonight as an upper level low lifts northeast along
the Mid-Atlantic coast.

&&

.NEAR TERM /Today and Tonight/...
As of 345 AM EDT Wednesday...

A shortwave ridge aloft will build eastward over central NC today as
an upper level low NE along the Mid-Atlantic coast. Although
lingering low-level moisture (dewpoints in the lower 60s) and highs
in the upper 70s to lower 80s may result in scattered diurnal Cu at
3000-4000 ft AGL, strengthening subsidence in the wake of the
departing upper level low (and approaching shortwave ridge) will
result in pronounced mid-level warming/drying and the development of
a strong capping inversion over central NC this afternoon. This,
combined with a thorough lack of forcing will result in dry
conditions through tonight. Expect lows in the upper 50s to lower
60s. -Vincent

&&

.SHORT TERM /Thursday and Thursday Night/...
As of 345 AM EDT Wednesday...

A strong subsidence inversion /cap/ will remain over central NC on
Thu. As such, one would expect dry conditions to persist. A squall
line over MO/AR at 06Z this morning is expected to propagate
eastward into the TN valley by 12Z Thu as a potent (albeit
deamplifying) shortwave trough lifts NE from the lower Midwest
through the OH valley. Despite decreasing/departing forcing, the
ongoing squall line in the TN valley Thu morning is expected to
propagate eastward into the southern Appalachians during the
aft/eve. An increasingly hostile thermodynamic environment with
eastward extent over the Carolinas should result in rapid weakening
(and eventual dissipation) of the squall line as it progresses
over/east of the Appalachians, however, it is possible that
lingering convection could affect portions of the western Piedmont
between 21-00Z before dissipation occurs. Outflow assoc/w the
remnants of the squall line could result in gusty westerly winds and
a 10-15F temperature drop in the Foothills/western Piedmont late Thu
afternoon, complicating the temperature forecast. Will indicate a
chance for showers and thunderstorms in the western Piedmont during
the late afternoon, with dry conditions elsewhere and highs in the
80s, coolest west and warmest (mid/upper 80s along/east of Hwy 1).
Expect warmer low Thu night (mid 60s) in assoc/w low-level moisture
advection from the SW and likely development of low stratus during
the pre-dawn hours. -Vincent

&&

.LONG TERM /Friday through Tuesday/...
As of 355 AM EDT Wednesday...

Classic summertime pattern emerges for late week and into the
weekend under the influence of a strengthening ~590 dm H5 ridge over
the western Atlantic. By Saturday, low-level thicknesses are progged
to peak between 1410-1420m(40m above normal) with H8 temps warming
to around 18C. Highs Friday 85 to 90, followed by upper 80s to lower
90s on Saturday, when we could challenge the record high max at RDU.
Heights are forecast to lower slightly on Sunday, with highs Sunday
similar to Friday`s temps.

Rain/convective chances through the weekend will be limited by the
dominate ridge. Will retain slight/small chance pops across the
western Piedmont, where initial convective development in the nearby
higher terrain could propagate downwind into the area. If storms do
develop or move east into the area on Saturday, strong instability
~3000 J/Kg aided by steep lapse rates aloft associated with a
modified EML, coupled with deep layer shear of ~25kts could support
some vigorous updrafts capable of producing large hail and damaging
thunderstorm winds.

A closed upper level low and associated deepening sfc low lifting
through the Upper Midwest will push a cold front into the area
Monday afternoon/evening. Attendant cold front will bring a chance
for showers and storms to the area Monday-Monday night with cooler
temps following on Tuesday.

&&

.AVIATION /12Z Wednesday through Sunday/...
As of 645 AM EDT Wednesday...

24 Hour TAF Period: Sub-VFR ceilings across central NC will lift to
VFR (3000-4000 ft AGL) by mid to late morning. A westerly wind at 5-
10 knots this morning will back to the SW/SSW at ~10 knots this
afternoon, then become light/variable after sunset.

Looking Ahead: Sub-VFR conditions assoc/w the remnants of a
weakening squall line are expected to affect the western Piedmont
(INT/GSO) late Thu aft/eve. With an offshore ridge, expect a
persistent southerly return flow over the Carolinas through the
weekend. As such, expect a potential for IFR/LIFR stratus each
morning (08-13Z). A conditional potential for isolated severe
thunderstorms will exist during the late afternoon hours Fri/Sat/Sun
across western portions of the state, potentially affecting the
INT/GSO terminals (should convection develop and/or propagate into
the area). -Vincent

&&

.HYDROLOGY...
As of 230 AM EDT Wednesday...

Small creeks and streams will gradually recede over the next 24
hours. Main stem river flooding will likely persist for several more
days. See water.weather.gov/ahps2/index.php?wfo=rah for the latest
forecasts and for additional information.

&&

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

&&

$$

SYNOPSIS...Vincent
NEAR TERM...Vincent
SHORT TERM...Vincent
LONG TERM...CBL
AVIATION...Vincent
HYDROLOGY..Vincent/MLM



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