River Flood Warning 25, NWS Raleigh, NC

Area Forecast Discussion
National Weather Service Raleigh NC
640 PM EDT Fri Apr 12 2019

.SYNOPSIS...
Southerly low level flow will maintain a moist air mass over
central NC while upper level disturbance approaches from the west.
Saturday into Sunday, a series of upper level disturbances will
traverse the region, producing periods of showers and a few
thunderstorms. Strong low pressure is expected to track
from Texas to the Ohio Valley Saturday night through Sunday
night. A trailing cold front will cross central North
Carolina early Monday morning.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 330 PM Friday...

Through 00Z Saturday, the highest risk for showers and storms will
generally be along and west of highway 1. Bulk shear of 40kts and
MLCAPE values around 1000 j/kg will support a few strong-severe
storms with the primary severe threat being locally strong or
damaging wind gusts. The atmosphere is quite moist in the lowest
10kt feet with precipitable water values around 1.5 inches. Thus,
the heavier showers and storms will likely produce instances of
heavy rainfall with upwards of an inch per hour probable. Since
storms vectors suggest a steady newd movement, not too concern at
this time about the potential of training cells. As the showers and
storms move east into the Coastal Plain this evening, the atmosphere
is ore stable and the shear not as strong. Thus, anticipate the
showers and storms to demonstrate a weakening trend as they approach
I-95.

Overnight, a sfc boundary will approach the northern Piedmont. This
boundary appears to stall immediately NW of our region. This
boundary will serve as focus for additional shower development
overnight into Saturday morning across the northern Piedmont.
Elsewhere shower coverage should be no worse than isolated to
scattered.

It will remain mild for this time of year with overnight
temperatures no cooler than the mid 60s.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 430 PM Friday...

An unsettled and conditionally unstable air mass over central NC
will likely become convectively active Saturday afternoon-early
evening. A stalled boundary in vicinity of the northern Piedmont
will serve as a focus for showers and possibly a thunderstorm
through much of the morning. As heating occurs in the afternoon,
expect the atmosphere to become slight-low end moderately unstable
south of the boundary, extending across the southern and northeast
piedmont. In addition, bulk shear, the result of mid level winds
~50kts, will be of sufficient strength to aid in organizing the
storms into broken bow segments with a cell or two potentially
exhibiting supercellular characteristics (persistent rotating
updrafts) with large hail and a brief weak tornado). Caveat to this
is the potential for the low overcast to be thick enough to prevent
insolation, leading to an atmosphere only marginally unstable. This
would lead to a lesser threat for severe convection.

Modest height rises Saturday night and associated weak subsidence
should lead to a brief lull in the threat for showers. Considering
that the atmosphere will remain quite moist, a few showers will
still be possible.

It will remain warm/a bit muggy for April with afternoon
temperatures generally in the mid-upper 70s. If partial clearing
occurs, temperatures in the 80-85 degree probable. Mild overnight
with lows in the 60s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
As of 320 PM Friday...

An impressive closed low exiting west TX on Saturday will move
northeast and open up across the MO and MS Valley on Sunday with the
trough axis reaching the Carolinas by Monday morning. A vigorous mid
level jet with 100+ kts at 500 mb lifting ahead of the trough across
MS and western TN will shift east and extend across the spine of the
southern Appalachians on Sunday evening. A deepening surface cyclone
centered near KMEM on Sunday morning will lift northeast into
upstate NY on Monday morning and into the Canadian maritime
provinces on Tuesday. A trailing cold front will approach the
southern Appalachians on Sunday evening and reach the coast before
midday on Monday. A more subtle east to west surface boundary will
likely linger across northern NC Sunday morning and then lift into
VA as pre-frontal trough extending southeast lift north across
central NC Sun evening.

The airmass across central NC on Sunday morning will be moist with
surface dew points ranging in the mid 60s with a widespread deck of
stratus clouds. With time, the stratus should lose its grip and
surface heating from intervals of sunshine will allow temperatures
to climb into the mid 70s in the Triad and Yadkin Valley to the
lower 80s across the Coastal Plain. This will result in weak to
moderate instability with MLCAPE values peaking between 750 to 1250
J/kg. It's worth noting that lapse rates are not terribly impressive
with a signal for a couple of stable layers aloft. This combined
with at first modest forcing for ascent on Sunday will limited the
convective coverage and intensity. As the upper trough approaches,
stronger forcing will arrive late in the afternoon and evening
resulting in a more organized and widespread region of showers and
thunderstorms that will spread from west to east. The primary
convective mode will be linear associated with the approaching upper
trough/associated cold front with a wind and embedded QLCS
mesovortices/tornado risk. The previous shift noted that a pre-
frontal trough/confluence axis on Sunday evening would provide a
threat for a few discrete or semi-discrete cells ahead of the main
line. The shower and storm threat will shut down from west to east
as the trough axis moves offshore.

Quieter weather is expected for the beginning and middle of the
upcoming work week as a dry northwest to westerly flow aloft is
expected on Monday and Tuesday. Surface high pressure will develop
to our west on Monday and build into our region on Tuesday. Morning
low level thickness values fall into the 1330 to 1340m range and
could support some lows in the upper 30s on Tuesday morning with
highs in the upper 60s to lower 70s on Monday and Tuesday.

An upper level ridge to our west builds east on Wednesday and then
moves offshore on Thursday as a southwesterly flow aloft develops.
Another potent springtime upper trough develops across the central
U.S. on Thursday and Friday, this one further north than the current
system. The upper level trough axis slows and approaches the region
on Saturday. This will result in moderating temperatures on
Wednesday and Thursday with an increased chance of showers and
thunderstorms late Thursday and especially Friday. -Blaes

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
As of 640 PM Friday...

There is a high probability that MVFR/IFR ceilings will occur across
central NC through 18Z Saturday as a moist and unsettled air mass
covers the region. A band of showers and a few thunderstorms will
traverse nwd across the eastern Piedmont and Sandhills early this
evening, and into the Coastal Plain during the mid-late evening.

A sfc boundary will move sewd into the northern Piedmont late
tonight, then stall before moving back as a warm front on Saturday.
This feature will likely maintain a few showers well into the night
and through Saturday morning across the northern counties. A few
strong storms are possible this afternoon across the western
Piedmont, producing sfc wind gusts 40-50kts and visibility aob 2
miles in heavy rain showers and frequent lightning.

Ceilings in the IFR/LIFR categories will be common late tonight into
Saturday morning with MVFR/IFR ceilings expected Saturday afternoon.
With heating of the moist atmosphere, expect scattered to numerous
showers and a few thunderstorms to develop across the region, with
most of the convection focused across the Piedmont counties
including KRDU, KGSO, and KINT. The stronger storms will produce
very heavy rain showers reducing the visibility to less than 2
miles, wind gusts 40-50kts, and frequent lightning.

The sub VFR ceilings will linger into Saturday night and Sunday
morning. A relative lull in the precipitation may occur late
Saturday night through early Sunday. Another round of scattered to
numerous showers and storms may affect the region late Sunday into
Sunday night. A cold front will cross central NC early Monday,
leading a drier more stable air mass into the region. This will
initiate a period VFR parameters Monday afternoon through Wednesday.

&&

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

&&

SYNOPSIS...WSS/Haines
NEAR TERM...WSS
SHORT TERM...WSS
LONG TERM...BLAES
AVIATION...WSS

Hazardous Weather Outlook...UPDATED
National Weather Service Raleigh NC
451 PM EDT Fri Apr 12 2019

NCZ008>011-026>028-041>043-077-078-088-089-131000-
Granville-Vance-Warren-Halifax-Franklin-Nash-Edgecombe-Wake-Johnston-
Wilson-Harnett-Wayne-Cumberland-Sampson-
451 PM EDT Fri Apr 12 2019

This Hazardous Weather Outlook is for central North Carolina.

.DAY ONE...Tonight.

Hazardous weather is not expected at this time.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

There is a threat for a few strong to severe thunderstorms Saturday
afternoon through early evening. The primary severe weather threat
will be locally strong to damaging wind gusts and large hail. A weak
tornado cannot be ruled out.

A cold front approaching from the west late Sunday into Sunday night will
be accompanied by a band of thunderstorms, some of which may be
severe. The main severe weather threats will be damaging wind gusts,
large hail and possibly a weak tornado.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed Sunday night.

NCZ007-021>025-038>040-073>076-083>086-131000-
Person-Forsyth-Guilford-Alamance-Orange-Durham-Davidson-Randolph-
Chatham-Stanly-Montgomery-Moore-Lee-Anson-Richmond-Scotland-Hoke-
451 PM EDT Fri Apr 12 2019

This Hazardous Weather Outlook is for central North Carolina.

.DAY ONE...Tonight.

An isolated strong to severe thunderstorm will be possible through 8
PM.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

There is a threat for a few strong to severe thunderstorms Saturday
afternoon through early evening. The primary severe weather threat
will be locally strong to damaging wind gusts and large hail. A weak
tornado cannot be ruled out.

A cold front approaching from the west late Sunday into Sunday night will
be accompanied by a band of thunderstorms, some of which may be
severe. The main severe weather threats will be damaging wind gusts,
large hail and possibly a weak tornado.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed late Sunday into Sunday evening.