Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 260554
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
154 AM EDT Tue Mar 26 2024

.SYNOPSIS...
Cold high pressure will extend southward through the region through
Tuesday. An area of low pressure will lift northeast along the
Southeast US coast on Wednesday, then continue along the Carolina
coast Wednesday night and Thursday. A cold front will move eastward
through central NC Thursday night.

&&

.NEAR TERM /TONIGHT THROUGH TUESDAY/...
As of 850 PM Monday...

The primary change with the evening update was to tweak hourly and
overnight minimum temperatures. Did go a touch colder in some
locations, particularly along the VA/NC border, and added patchy
frost in a few locations. Considered the possibility of issuing a
frost advisory for some counties along the state border, but after
collaborating with neighbors, did not feel that there was enough of
a widespread threat for frost, plus the temperatures below 36
degrees should only occur for a limited time. Previous discussion
follows.


As of 252 PM Monday...

Through tonight: Light nely flow continues this afternoon with some
upstream cirrus moving in from the west. Expect this cloud cover to
gradually thicken overnight.  Low-level thicknesses will rise some
compared to this morning allowing a bit milder lows in the mid to
upper 30s. Given this, and perhaps a little residual stirring
tonight, the ambient weather conditions should preclude any
widespread frost.

Tuesday: Flow aloft will turn more swly Tuesday as an upper trough
over the central US eases eastward.  At the sfc, central NC will
remain wedged between an offshore low to the east, a retreating high
to the north, and an approaching cold front well to the west.
Residual dryness will prevail through much of Tuesday, but dew
points will start to recover some under esely sfc flow.  Despite
decent cloud cover, expect a mild day with highs in the mid to upper
60s.

Weak vorticity lobes out ahead of the main upper trough will
approach the southern Appalachians Tuesday afternoon and evening.
Associated rain chances, however, will largely hold off for our area
until after 00Z Wednesday as the deeper moisture arrives later
Tuesday evening. Still, can`t rule out at least some light
isentropic-driven rain in the Triad late Tuesday afternoon. Any
observations will mostly read trace.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 330 PM Monday...

Confidence is high in a somewhat prolonged and briefly moderate to
heavy rainfall event during this period, as the expansive upper
level trough extending from Saskatchewan/Manitoba to N Mexico (with
embedded waves) lumbers eastward through central NOAM through early
Wed and into E NOAM by late Thu. PW begins to ramp up above normal
late Tue, peaking at 150-200% of normal over our area (approaching
daily record maxes) and E NC Wed afternoon through early Thu before
the anomalously high values gradually shifts E.

Confidence is fairly high on the timing and placement of rainfall
with this event, and is moderate regarding amounts, as some degree
of model variability regarding amounts remains. Potential reasonable
alternate scenarios for this event include slightly earlier or later
rain arrival, likely not more than 6-9 hours in either direction.
The LREF 25th and 75th percentiles for storm total amounts differ by
1-2", so the uncertainty there is still fairly high.

The overall rainfall timing, based on the latest operational models
and ensemble solutions including the LREF, is to bring chance pops
to the W mainly after midnight Tue night, followed by the heaviest
and most expansive rain Wed afternoon through Thu morning with
likely to categorical pops, followed by a WSW to ENE taper to no
pops after midnight Thu night. The heavier rain window late Wed
through Wed night will coincide with passage of an upper divergence
max and the approach of a strong shortwave trough pivoting through
AL/GA toward the Carolinas, becoming negatively tilted in the
process. This will coincide with likely multiple surface lows along
the front which track through the central and eastern Carolinas.

Regarding storm total rainfall, the model consensus, including the
NBM, LREF, and WPC superensemble output, support values just
slightly under the previous forecast, still a range of 1.5-3.25"
over central NC. Given that there is expected to be very little in
the way of convective elements to this rainfall ( and the fact that
it will be spread out over 36+ hours in most spots, the excessive
rainfall outlook is maintained this afternoon at a marginal risk.
But if total values ramp up in later forecasts, esp heavier rain
over a shorter time of just a few hours, an upgrade may be needed.
At this time, we could see considerable minor urban flooding esp in
poor drainage areas, with an uptick in river levels across the
board, but there is uncertainty of any situation more dire than that
occurring.

Expect lows 41-54 Tue night, highs 56-71 Wed, lows 45-55 Wed night,
highs 53-64 Thu, and lows 36-43 Thu night with clearing skies. Given
the complexity of the expected surface pattern, confidence in the
details of these temps is not high. -GIH

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 215 PM Monday...

Surface high pressure over MS/AL on Friday, will shift south over
Florida by Saturday. A few disturbances are expected to move over
the OH valley and then over the Mid-Atlantic late Sunday into
Monday. Easter Sunday is expected to be dry across the majority of
the region. However, some models do show precipitation to along the
VA/NC border late Sunday/Sunday night. For now have introduced
minimal slight chance PoPs in portions of the Northern Piedmont near
the VA border. High temperatures are expected to be above average
over the weekend with highs in the low to mid 70s, with some areas
in the south could near 80 on Sunday.  Lows will generally be in the
upper 40s to low/mid 50s.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
As of 145 AM Tuesday...

VFR conditions will continue across much of central NC through this
evening. MVFR stratus may develop near KRWI between 12-15Z this
morning, however confidence is too low to include in the TAF at this
time. SHRA and MVFR ceilings will approach the Triad by late
evening, with portions of the Triangle observing VCSH by early
tonight.

Outlook: Rain showers and sub-VFR conditions will develop across
most areas tonight into Thursday. Isolated TSRA are possible
Wednesday and Thursday. VFR conditions will return from west to east
late Thursday into Thursday night and continue into Saturday. Gusty
winds are expected at times Thu and Fri, with northerly isolated
gusts to 25 kt Thu and NW more widespread gusts to 25 kt Fri.


&&

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

&&

$$

SYNOPSIS...KC
NEAR TERM...Green/Luchetti
SHORT TERM...Hartfield
LONG TERM...CA
AVIATION...JJT


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