Morrisville, North Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

405
FXUS62 KRAH 261013
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
615 AM EDT Tue May 26 2026

.WHAT HAS CHANGED...

* No major changes.

&&

.KEY MESSAGES...
As of 255 AM Tuesday...

1) Isolated to scattered storms today may produce pockets of heavy
rainfall. This heavy rainfall signal is not as clear as it was
Monday.

2) Progressively decreasing humidity and chances of convection will
result mid to late week.

3) A mainly dry and mild period will follow a chance of Saturday
convection/rain.

&&

.DISCUSSION...
As of 255 AM Tuesday...

KEY MESSAGE 1... Isolated to scattered storms today may produce
pockets of heavy rainfall. This heavy rainfall signal is not as
clear as it was Monday.

The airmass and overall atmospheric pattern is virtually unchanged
from Monday, with a few subtle differences. The mid-level ridge off
the SE US coast edges a tad westward, resulting in slightly higher
heights over the region. The larger parent trough over the lower MS
valley will gradually move north into AR/MO later today and tonight.
Ripples of energy along its eastern flank will promote remnant MCVs
to track once again across AL/GA/SC and western NC. Most of central
NC will again be in that moist SSW flow aloft, with PW`s unchanged
at around 2 inches, about 160-percent above normal, with 15-20 kts
of mean-layer flow.

Although the pattern is nearly identical to yesterday, confidence on
storm coverage is somewhat less given the lack of defined forcing.
Satellite imagery reveals perhaps another remnant MCV in upstate SC
that rides up into areas along/east of US-1 this afternoon and
evening. But its location is difficult to make out. Across the
northwest, perhaps a remnant outflow from convection northwest of
the Triad last night may force additional convection in our
northwest Piedmont. Regardless, much of the high-res guidance
depicts a near persistence forecast, with storm coverage blossoming
in the mid-late afternoon to early evening hours, perhaps an hour or
so later than Monday and tapering off by late evening. Guidance
shows a higher preponderance of storms in our southeast, perhaps
driven in part by a sea-breeze, but accurate initiation may have to
wait until daytime visible satellite imagery to examine mesoscale
boundaries. A decaying MCV may again track into the northwest
Piedmont later tonight before showers once again wane overnight.

As for the heavy rainfall threat, it remains in place, though our
confidence is low. The HREF/REFS 24-hr LPMM does indicate some
isolated 1-2 inch rainfall totals across our southern zones, but
overall coverage of heavy rainfall appears limited relative to
Monday. Isolated flooding may be confined to areas that received
rainfall on Monday.


KEY MESSAGE 2... Progressively decreasing humidity and chances of
convection will result mid to late week.

A plume of waning PWs of 1.5-1.75" and 125-150% of normal and
embedded MCVs will be directed from the Gulf to the Carolinas,
between a sub-tropical high offshore and a reloading trough over the
srn Plains. Weakly falling mid-level heights (20-40m/12hr) will
result across NC Wed-Wed night from both the progression of MCVs and
also ahead of a positive tilt trough that will dig from James Bay to
offshore the Middle Atlantic and New England coast and which will
culminate in the development of a cyclone and negative height
anomaly invof Atlantic Canada by Thu-Thu night.

At the surface, preceded by an Appalachian lee trough and sea breeze
over NC on Wed, a couple of fronts now over the Virginias and
another now over the upr MS Valley and upr Great Lakes will progress
swd and across cntl NC Wed night through Thu night. The preceding
airmass over cntl NC will progressively dry owing to both
increasingly wly to nwly downslope flow even ahead of the fronts and
especially in dry advection behind them.

Wed will be the last of the current stretch of above average chances
of convection in this unseasonably moist/humid pattern, which
materialized at the surface and aloft following delayed CAD erosion
over the weekend. Strengthening deep layer flow, more-so across the
Middle Atlantic but with up to 25-30 kts of 0-6km bulk shear over
cntl NC, will probably support an uptick in organized convection
that will include multi-cell clusters capable of strong downbursts
across cntl NC. The presence of the aforementioned deep moist axis,
and forecast Corfidi vectors of only around 5 kts, suggest a threat
of excessive rainfall from training/backbuilding convection may also
result.

While it will remain warm and well into the 80s on Thu, the richer
low-level moisture and humidity will likely have been swept swd by
the lead front forecast to progress across the forecast area Wed
night. Decreasing low-level and deep layer moisture, and increasing
downslope flow, should limit convective coverage (to isolated or
widely scattered) and intensity Thu afternoon.


KEY MESSAGE 3... A mainly dry and mild period will follow a chance
of Saturday convection/rain.

A blocking high will develop and strengthen across cntl Canada
through the weekend-early next week and be flanked by troughs over
both sides of NOAM and undercut by srn stream flow across sub-
tropical latitudes. The primary forecast uncertainties in this
developing pattern will be timing and amplitude of shortwaves
progressing through the ern NOAM trough and to what degree any may
interact with srn stream flow progressing beneath the blocking high
and across the Southeast. The models have come into better agreement
in the past couple of days regarding the progression of a compact
cyclone across and offshore the nrn Middle Atlantic and New England
early this weekend, but with continued wide model spread in ern NOAM
trough amplitude and location through early to mid next week.

At the surface, weak high pressure and a continental airmass will
progress from the Great Lakes to offshore the Middle Atlantic Fri-
Fri night, ahead of a frontal system that will accompany the compact
cyclone and trough in nw flow aloft early this weekend. The
associated cold front will likely settle swd and across cntl NC on
Sat, with a chance of both along-frontal convection and post-frontal
rain/showers. It should then turn dry and otherwise remain mild for
the latter half of the weekend into at least early next week, as a
stronger area of high pressure and related dry/continental air
progress from the Great Lakes to the Middle Atlantic, beneath and
downstream of the aforementioned blocking high over cntl Canada.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
As of 615 AM Tuesday...

Areas of IFR/MVFR ceilings are expected to start the TAF period. A
gradual improvement is expected towards MVFR and then VFR between 15
and 18z. Our overall confidence in storm coverage is low given the
lack of an appreciable forcing mechanism this afternoon and evening.
Outside of a remnant MCV, storms look to fire along small-scale
boundaries, which are presently difficult to discern with the lack
of visible satellite. High-res guidance is also mixed on storm
coverage, further complicating matters. Given these concerns, opted
to go with PROB30 groups this afternoon and evening with respect to
storms. We will let the day shift take a closer look and adjust as
needed with the 12z model guidance. Some pre-afternoon convection
may initiative near GSO in association with a weak MCV upstream in
western NC. Storm coverage should lessen between 02-05z, followed by
sub-VFR stratus developing again by early Wednesday morning.

Outlook: Morning low stratus will again be possible Thursday
morning. Storms are again favored Wed, but drier VFR weather is
expected Thu and Fri. Showers may return Sat with another frontal
system.

&&

.CLIMATE...

Record High Minimum Temperatures:

May 26: KGSO: 70/2019 KRDU: 73/2011 KFAY: 75/2004

May 27: KRDU: 72/1991 KFAY: 72/2006

May 28: KGSO: 70/2012 KRDU: 74/1914

&&

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

&&

$$

DISCUSSION...Kren/MWS
AVIATION...Kren
CLIMATE...RAH