Area Forecast Discussion
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FXUS62 KRAH 231943
Area Forecast Discussion
National Weather Service Raleigh NC
330 PM EDT Sun Apr 23 2017
A strong mid and upper level storm system will move slowly east
from the Tennessee Valley into the Carolina`s through Tuesday.
A surface low pressure will track from Georgia east to the Carolina
coast through Tuesday.
.NEAR TERM /Tonight through Monday/...
As of 330 PM Sunday...
Flood Watch through 800 AM Tuesday...
For the rest of the afternoon and evening...
Periods of rain will continue through the evening across most
of the area. Widespread rain will continue across our western
and northern zones of the Piedmont. Hourly rates are in the
0.05 to 0.10 range in these areas are not expected to produce
any significant or widespread type flooding issues through the
evening. However, these rains will wet and in many cases begin
to saturate the soil. This will prime the area for runoff
when the heavier rainfall rates develop from the west later
tonight. We will maintain 100 POP in the west and north, with
70 (likely) POP in the southern tier of counties where the
current radar trends are in a lull there. Temperatures will
be in the 50s west and north, with readings falling into the
Concerning the Flood Watch through 800 am Tuesday...
The main flood threat is expected to develop into our region from the
west tonight. The latest models are in good overall agreement in
depicting entire positively tilted mid/upper low over middle TN
to slowly track ESE through the TN valley to over northern GA later
tonight and Monday, evolving into a negatively tilted system aloft
with time. Strong mid level lift is forecast to arrive over much of
southern and western areas later today and tonight, then in the east
The negatively tilted system will tap very deep moisture
which will be pulled NW from the Gulf Stream and western Atlantic
into northern SC and much of NC. This surge of moisture will be
forced to lift over the cool stable dome - north of the stationary
boundary across our region. The result will be increasing rainfall
rates with heavy rain likely to spread eastward into our western
Piedmont late tonight, then progress slowly east through the
Piedmont, Sandhills, and Coastal Plain Monday and Monday night. It
is still a bit too early to pin point where flooding will occur;
however, it appears that the western and southern part of central NC
may end up the most likely location for widespread type flooding.
Storm totals are still expected to range between 3 and 5 inches,
with locally 6+ inches possible. Just about any area could see the
6+ inches in the current watch area and we will continue the Flood
Watch for all zones. The main time frame for flooding will be Monday
through Tuesday morning. The heaviest rain should end early to mid
General meteorological and sensible weather discussion:
Driven by the 1022+ mb surface high pressure that was nosing down
into our region from PA/NY, strong CAA with the low level NE wind
had overspread all our region. The cold front has made it well south
into South Carolina. All of our region including even the SE Coastal
Plain is on the cool side of the boundary.
Temperatures were a good 30 degrees colder today than this time on
Saturday. Readings were in the 40s NW ranging into the 50s
elsewhere. Rain was widespread over the western half of NC west and
south through the Tennessee Valley and northern GA.
Rain continued to overspread areas along and NW of a line from
Albemarle to Raleigh and Roanoke Rapids. This covers all the
Piedmont and portions of the northern Sandhills and northern Coastal
Plain. Rainfall thus far has been generally 0.50 to 1.50 inches in
the west with between 0.25 and 0.50 east - locally 1+ inches. This
is just about as expected thus far. The maximum rain thus far has
been in a SW to NE corridor from the Mountains along the northern
tier of NC and southern VA where 1 to locally 4 inches has been
observed. The rainfall thus far has simply wet down the dry ground
as many areas had received only 50 to 75 percent of normal
precipitation in the past 1 to 2 months before this rain even began.
The latest models support the ongoing forecast and reflect the
current radar and satellite trends very well. Strong layer lift is
forecast to develop east to cover much of southern and western areas
tonight, then slowly move east over all of NC, especially strong
over the southern zones Monday and Monday night. The negatively
tilted system will tap very deep moisture which will be pulled NW
from the Gulf Stream and western Atlantic into northern SC and much
of NC. Thus, the heavy rain with storm totals of 3 to 5 inches still
appears likely if not probable, with 6+ inches possible.
The possibility of thunderstorms may exist, mainly over the
Sandhills and SE Coastal Plain late Monday and Monday night as the
warm sector may penetrate these areas. This occurs as the low
pressure tracks east and the warm front tries to nudge inland. The
front may be able to reach into portions of our SE zones and if so,
there would be a risk of a brief tornado with any storms that
develop near or along the boundary.
Cool temperatures in the 50s tonight will warm only into the mid 50s
to mid 60s Monday, except near 70 SE. Lows Monday night will hold in
the 50s NW and range to the mid 60s SE.
.SHORT TERM /Monday night through Tuesday/...
As of 330 PM Sunday...
The threat of flooding will continue with heavy rain gradually
tapering off from the west Monday night into Tuesday morning. The
severe threat should end as the low pressure and cold front shift
offshore early Tuesday. Rain will continue over much of the eastern
half of the region through at least mid day as the low tracks up the
Cloudiness and northerly low level flow will keep many areas in the
upper 50s and 60s Tuesday, with the warmest readings in the SW,
where some clearing may take place.
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
As of 330 PM EDT Sunday...
A short wave ridge will quickly move across our region Tue Night
through Thu night, resulting in dry warming weather during this
time. Highs Wed and Thu in the 80s and lows in the upper 50s to
A weak short wave in the sw flow is progged to move across the area
early Fri. Will include a slight chance pop for daytime Fri.
Otherwise, the ridge over the se is progged to amplify over the
weekend, keeping the precip-makers to our north and west, and an
above normal airmass over our area. Highs in the upper 80s and lows
in the mid 60s during this time.
.AVIATION /18Z Sunday through Friday/...
As of 145 PM Sunday...
IFR to LIFR CIGS with MVFR VSBYS in rain and fog are expected
through the TAF period. Period of heavy rain will occur at KINT/KGSO
tonight, then all areas Monday and Monday night. The rain should
begin to taper to drizzle on Tuesday. However, low CIGS and VSBYS
below MVFR range should continue through 12z/Tuesday.
Cigs should rise gradually to MVFR areawide Tue as the mid level low
slowly departs the area, then trend to VFR Tue night lasting through
Fri with a drier air mass.
As of 300 PM Sunday...
...A Flood Watch is in effect through 800 AM Tuesday...
Flooding of creeks and small streams is expected to begin later
today and tonight as the ground saturates and the rainfall becomes
heavier. This is expected to occur over the western Piedmont,
including the Triad region first, then shift east with time (later
tonight and Monday) to bring the threat across all areas.
River flooding will become more likely on Monday and could linger
into midweek. Based on our expected rainfall distribution at this
time, the Haw river would be particularly prone to minor flooding
above Lake Jordan, but any of the mainstem rivers could reach minor
to flood stage, especially given just a bit more rain than currently
On a positive note, we were on the cusp of drought conditions due to
rainfall deficits over the late winter and spring, so this event
will turn that around and possibly eliminate much of a drought
threat for the rest of the spring season.
Flood Watch through Tuesday morning for NCZ007>011-021>028-038>043-