Turner Downs Forecast Discussion

000
FXUS62 KRAH 261328
AFDRAH

AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
925 AM EDT Tue May 26 2020

.SYNOPSIS...
High pressure over the western Atlantic combined with a developing
surface low near the Southeast coast will produce an onshore flow of
moisture through mid week. The surface low and an upper level
disturbance will bring a period of unsettled weather for mid to late
week period. A cold front will approach the area on Friday and move
across the region on Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 925 AM Tuesday...

Once again today, the mid-morning update is primarily an hourly
temperature update, with the rest of the forecast in good shape.
Skies are expected to remain mostly cloudy through the day, although
there should be some occasional breaks in the cloud cover.
Precipitation should generally stay south of the area today.
Previous discussion follows.


As of 345 AM Tuesday...

Early morning surface analysis shows surface high pressure
centered off the New England coast ridging west and southwest
into the mid Atlantic and into the northern Carolinas. In
addition, a weak surface low was developing across eastern
Florida. An upper level ridge extended from the western Atlantic
into the mid Atlantic.

Widespread stratus and some high level cloudiness across central
NC will result in a cloudy start to the day across the area.
The stratus deck won`t be as tenacious today as Monday and it
will lift and show breaks late this morning and especially this
afternoon. Even with fewer low clouds, high clouds will increase
and thicken from the south and southeast today. Generally dry
weather is expected across much of central NC today although a
few of the CAMs suggest an area of showers will move north from
SC and into the Sandhills and southern Piedmont late this
afternoon into this evening. While low level thickness values
are similar to perhaps slightly cooler than yesterday, some
statistical guidance especially the EC ensemble support raising
highs a couple of degrees into the 75 to 80 degree range.

Most of the diurnally supported scattered showers across SC
that will move into southern NC during the evening will wane as
they lift northwest. The result will be mainly dry conditions
tonight. As the surface low near Florida lifts north, a surge in
moisture and isentropic lift will support a large area of
showers that will approach and move into the southern Coastal
Plain and Sandhills toward daybreak on Wednesday. Lows tonight
will range in the 60s. -Blaes

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of 400 AM Tuesday...

...Another period with potentially heavy rain on Wednesday and
Wednesday night...

The combined flow from an upper level ridge near and off the mid
Atlantic coast and a closed low moving slowly east from Texas
into the Mississippi Valley with result in a notable increase in
deep layer moisture across the region. At the same time, a
developing surface low near the Savannah Georgia area around
daybreak Wednesday will lift slowly north across the Carolinas
through Thursday morning. The result will be a surge in
precipitable water values that climb in excess of 2 inches
during the period. Strong forcing for ascent combined with
modest instability will result in the development of a large
area of showers and possibly a thunderstorm with heavy rain that
slowly lifts north across central NC on Wednesday and Wednesday
night. have raised PoPs to categorical for the period and
included a slight chance of thunderstorms. The best focus for
any strong storms will be just to our southeast, near the coast
in a region of surface based instability. The heaviest rain
will likely fall late Wednesday morning across the south and
then lift north through Wednesday evening with rainfall amounts
averaging between 0.75 inches and 1.5 inches with locally higher
amounts possible. WPC is expected to place much of the area
from Fayetteville to Wadesboro to Greensboro in the slight risk
area for the day 2 excessive rain outlook. These rainfall
amounts and periods of possibly heavy rain will likely result in
rises on areas stream and creeks and potentially flooding of
poor drainage areas. Highs on Wednesday will range in the lower
70s across the Triad to the upper 70s across the Coastal Plain.
Lows will only fall back into the mid 60s to around 70. -Blaes
&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 400 AM Tuesday...

The upper-level ridge centered off the mid-Atlantic coast will
slowly expand south through the end of the workweek, and combined
with surface high pressure off the coast of New England, will
continue the transport of moist, southerly flow into central NC
through the end of the week. Model forecast soundings display a
deep, moist profile across the region through the end of the week,
with precipitable water values near 2.00 inches. Although the
surface and upper-level low will exit the region Thursday morning,
abundant atmospheric moisture and sufficient instability aloft will
continue the possibility of moderate to heavy showers and
thunderstorms Thursday afternoon, with lower chances Thursday night.
Confidence in location of heaviest rainfall remains low due to model
to model and run to run disagreements, however saturated soils will
aide in runoff and could create a flooding threat where heavy
rainfall occurs and downstream of rivers. WPC has declared parts of
central NC in a marginal risk of excessive rainfall Thursday.

With the tropical airmass still in place Friday, weak CAPE will be
enough to generate areas of showers and thunderstorms across much of
the region, with coverage of storms decreasing overnight Friday. On
Saturday, an upper-level trough will swing across the region
followed by the associated cold front late Saturday. The front will
tap into the moist airmass still in place across the region,
generating numerous showers and thunderstorms, especially late
Saturday.

Chances of precipitation decrease from NW to SE Sunday morning, with
most of the Piedmont dry by the afternoon. Surface high pressure
will then build in across the region with NW flow aloft early next
week creating dry weather and partly cloudy skies across the region
for the start of meteorological summer.

Near seasonal normal highs in the low to mid 80s mid to late week
will lower to the 70s early next week after the cold front moves
through. Although highs for the end of the week will be near normal,
dewpoint temperatures in the upper 60s to low 70s will make it feel
more muggy. The front will help low temperatures of 5 to 10 degrees
above normal late this week lower to around 5 degrees below normal
by Monday morning, with lows in the mid-50s Monday morning.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
As of 725 AM Tuesday...

Through 12Z Tuesday: areas of MVFR to IFR stratus was spreading
across central NC this morning with the greatest coverage across the
Coastal Plain, Sandhills, and the eastern Piedmont with VFR ceilings
across the western and northwestern Piedmont. Low ceilings just
arrived at KRDU. Sky conditions should improve with lifting ceilings
into the VFR range around midday and the early afternoon. Low
stratus is expected to redevelop again tonight and early Wednesday
morning with more widespread coverage and developing earlier,
generally between 06 and 09Z. Light northeast to east winds
averaging around 5 to 10 kts are expected through the period.

Outlook: An unsettled period with prolonged intervals of adverse
aviation conditions is expected into the weekend as surface low
moves slowly north across the area through Thursday and then as a
cold front approaches on Friday and moves across the area on
Saturday. A considerable amount of clouds and periods of ceilings
restrictions along with periods of visibility restrictions in showers
and storms, especially on Wednesday into Thursday and again late
Friday into Saturday. -Blaes

&&

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

&&

$$
SYNOPSIS...Blaes
NEAR TERM...Green/Blaes
SHORT TERM...Blaes
LONG TERM...JJT
AVIATION...Blaes

NWS RAH Office Area Forecast Discussion