Sunrise 6:03 AM   Sunset 8:17 PM Moonrise 3:45 PM   Moonset 2:52 AM

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FXUS62 KRAH 200206 AFDRAH

Area Forecast Discussion National Weather Service Raleigh NC 1006 PM EDT Sun May 19 2024

SYNOPSIS
High pressure will extend across and offshore the Middle Atlantic through Tuesday.

NEAR TERM /THROUGH TONIGHT/
As of 1000 PM Sunday...

Only minor tweaks were made to hourly temperatures and sky cover as stratocumulus deck has persisted longer in the Coastal Plain while widespread clearing has occurred across the Piedmont. Otherwise the forecast remains on track for areas of fog develop across northern portions of the Piedmont with patchy fog elsewhere.

As of 400 PM Sunday...

Water vapor imagery shows multiple embedded waves within an elongated trough axis extending from off the Northeast coast through the Mid-Atlantic with a compact shortwave at its base over the SC/GA coast. One wave sliding through south-central VA will continue southward and over central NC through this evening with some Hi-Res guidance indicating a light sprinkle or two, but most locations will remain dry as RAP point forecast soundings show multiple weak inversions aloft and relatively dry thermodynamic profile.

Widespread afternoon cumulus is expected to dissipate with loss of boundary layer mixing, minus pockets light rain/sprinkles and associated cumulus clouds, will briefly lead to mostly clear skies early overnight. Light northeasterly flow overnight will advect marine layer stratus into the Coastal Plain towards daybreak. West of this cloud deck, lingering rich boundary layer moisture and mostly clear skies will favor the development for areas of fog, potentially dense is some locations, from the Triangle towards the Triad by daybreak Monday morning. Overnight lows will settle in the mid 50s to low 60s.

SHORT TERM /MONDAY THROUGH MONDAY NIGHT/
As of 152 PM Sunday...

High pressure ridging will be in place at mid-levels for our Monday.
High pressure at the surface off the east coast will continue to nose down into the area, resulting in a NE flow once again. We will see some stratocumulus develop for the daytime, but more sunshine is expected as deeper mixing ensues, especially across the Coastal Plain. The airmass will warm some too, but highs should still be about a degree or so below seasonal norms in the upper 70s to low 80s, lowest in the NE Piedmont to northern Coastal Plain of perhaps mid 70s. Clear skies and light winds in the evening and overnight will favor lows a touch below average in the mid to upper 50s, except low to mid 50s in the NE Piedmont and northern Coastal Plain.
Lingering low-level moisture could favor fog development from the Triangle eastward into the Coastal Plain for early Tue morning.

LONG TERM /TUESDAY THROUGH SUNDAY/
As of 350 PM Sunday...

Dry conditions and mostly sunny skies are expected across central NC on Tuesday and Wednesday as mid/upper ridging extends from the western Gulf of Mexico to off the Mid-Atlantic coast. This ridging will be in between a series of shortwaves moving across the northern Plains and Upper Great Lakes and a cutoff low off the Southeast US coast. At the surface, elongated high pressure will extend from the NE down the Eastern Seaboard, initially bringing NE flow that shifts more southerly on Wednesday as the high shifts SE to near Bermuda.
This will help increase high temperatures from lower-80s on Tuesday to mid-to-upper-80s on Wednesday and upper-80s to lower-90s on Thursday. Lows will also increase from upper-50s to lower-60s on Tuesday night to lower-60s to upper-60s by Thursday night.

The pattern turns more unsettled from late this week into the weekend. As one shortwave moves across the northern Great Lakes and northern New England on Thursday/Thursday night, it will drag a cold front that approaches the Appalachians. However, with the best upper forcing to our north, only carry slight to lower chance POPs (highest north). A better chance for showers and storms comes on Friday and Saturday as a southern stream wave moves across the TN Valley and potentially over our region. Carry high chance POPs on these days, but didn't feel comfortable going likely considering timing differences between the different models and given this is Days 6-7. POPs decrease a bit again on Sunday as the shortwave exits, but still above climo. Temperatures are more uncertain during this period and will depend on how far south the aforementioned cold front is able to get, but the latest GFS and ECMWF keep it mostly hung up to our north. So forecast highs remain near to slightly above normal.

AVIATION /00Z MONDAY THROUGH FRIDAY/
As of 720 PM Sunday...

A challenging aviation forecast, with lower confidence than usual.
Broken VFR stratocu persists from RDU to the E (RWI) and S (FAY), streaming in from SE VA within light NE surface flow and beneath a 15-20 kt northeasterly low level jet nosing into the NC Coastal Plain from the Delmarva at 2000-4000 ft AGL. Lower MVFR cigs are found over coastal sections, while the NW Piedmont (INT/GSO) is mostly clear but with some VFR clouds drifting in from SW VA. With light surface winds within high pressure ridging nosing in from the north, in tandem with a lack of higher clouds and a high near-ground RH overnight, will foster good radiational cooling and perhaps shallow fog bank development in areas that see few clouds or partial clearing through this evening, however an extended mostly clear period to allow for fog formation is less than certain, given the persistent clouds in the E and upstream of the NW. The greatest chance for sub-VFR conditions (likely MVFR cigs/vsbys) will be across portions of the N Piedmont, but most likely to occur N and NW of RDU and holding E of GSO/INT. The most likely scenario is a thinning of the stratocu in the E (RDU/RWI/FAY), while scattered clouds continue to move in near INT/GSO, then MVFR cigs should develop after 07z at all sites, with MVFR vsbys in fog along with isolated banks of shallow IFR fog. Cigs may briefly dip to IFR around daybreak, but confidence in this is low. Conditions should improve to VFR gradually between 13z and 15z, and persist through the end of the TAF valid period. Dry weather will hold, with surface winds generally light from the NE, but increasing to around 10 kts at RDU/RWI/FAY after 14z Mon.

Looking beyond 00z Tue, a good chance for sub-VFR fog is expected late Mon night through daybreak Tue. Otherwise, VFR conditions will dominate through Thu, although the chance for showers and storms will return for Thu and Fri, mainly each afternoon/evening. -GIH Lows will bottom out in the mid/upper 50s to low 60s.

RAH WATCHES/WARNINGS/ADVISORIES
None.

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