Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/06/20

AREA FORECAST DISCUSSION

National Weather Service Raleigh NC

 942 PM EST Wed Feb 5 2020

.SYNOPSIS...
A backdoor cold front moving toward the region will settle across
north central North Carolina before moving back northward as a warm
front early Thursday. A slow-moving storm system will push into our
area from the west beginning Thursday morning, introducing heavy
rain and a risk of strong thunderstorms on Thursday. The region
should finally begin to dry out on Friday as high pressure and
cooler temps build in for the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 940 PM Wednesday...

As mentioned in the previous update, the backdoor cold front in the
vicinity of the NC/VA border may sink a little further south over
the next few hours, stalling near the Triad and along/just north of
the I-40 corridor before lifting northward again early Thursday
morning. Temperatures vary significantly across the area due to the
front, with mid to upper 40s north and low to mid 60s south.
Dewpoints south of the front are in the 55-60 degree range, with the
moist nose riding just east of the Appalachians. The primary surface
low as of 00Z was centered over the TN/AL border with the cold front
extending southwest through MS and LA. Severe convection continues
ahead of the front. This surface low is displaced to the southeast
of the H85 low (centered over MO/IL). A large area of heavy rain and
thunderstorms over the Southeast will continue propagating northeast
into the mid-Atlantic and moving into central NC tonight, while the
primary pre-frontal line of convection lags behind. Expect PWATs to
increase overnight from 1.2" to upwards of 1.5" by daybreak. The
front draped across the area should lift northward as the rain moves
into/through central NC tonight. As previously mentioned, lows will
be a bit tricky as they will depend on the front but generally
expect mid 40s north and NE to low/mid 60s across the south, which
leave a good margin for error in between.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
As of 425 PM Wednesday...

...Threats for flooding and severe storms Thu into Thu night...

Very impressive moisture flux strengthens further ahead of the
approaching front, which should reach the western NC border Thu
afternoon, the western CWA by early Thu evening, then move E of the
CWA shortly after midnight. Record high PW values for this date are
a near certainty as they approach or exceed 1.5", and model forecast
integrated vapor transport is some of the strongest in recent
memory, over 1200 km m-1 s-1, signaling a distinct atmospheric river
with both Pacific and Gulf/Caribbean sources. Forcing for ascent
will remain intense as well with vigorous kinematics, as the
strengthening 55-65 kt 850 mb jet shifts E across the area during
the day and evening. The greatest upper divergence over western NC
Thu morning will shift E through the day and night, attending mid
level height falls of 150-230 m. Will carry categorical pops, in the
west early and expanding eastward through the day, then shifting to
E sections Thu night with decreasing pops in the W late.

Confidence in the flooding risk is high for the Piedmont, given the
intense moisture transport and deep lift, and have issued a flood
watch for the Piedmont of central NC for Thu through Thu evening for
storm totals of 2-5". Models and ensemble systems have been pretty
consistent in depicting the band of highest totals over the western
half of NC, where the multiple hours of steady moderate to heavy
showers will be augmented locally by convective elements generating
locally heavier amounts. Cells and segments will also pass
repeatedly over the same areas, enhancing totals in swaths.
Confidence is lower further E, where models are generating lower
amounts as the approaching upper trough gives an eastward kick to
the main band of precip, resulting in lower rain residence time. If
this scenario changes in later runs, the watch may be expanded in
area and forward in time.

The risk of severe storms continues as well. Despite the surging
dewpoints, CAPE values are expected to be generally less than 1000
J/kg, but with strong shifting winds producing long gently curved
hodographs, discrete cells and bowing segments are likely near the
front end of the precip shield. Any of these could tap into the
strengthening winds just off the surface and produce damaging
straight line winds, and a few cells feeding on sufficient low level
vorticity may result in a quick spinup of a tornado. Irrespective of
storms, background winds near the surface and aloft will be quite
blustery with gusts over 25 kts likely, especially over the E half
of the forecast area where the low level height gradients will be
tightening through the day. With the wet ground potentially
resulting in loosening root systems, some trees may be knocked down
even away from storms. An impact-based wind advisory is not out of
the question, although gusts may not meet traditional criteria.

Expect highs Thu to be in the mid 60s NW ranging to mid 70s SE,
with lows Thu night from the mid 40s W to the upper 50s E. -GIH

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
As of 205 PM Wednesday...

By Friday morning, the cold front should have moved east and
offshore of the Carolinas, so the bulk of the rain will have also
moved east, but there will still be leftover showers with the upper
trough moving through. Kept chance pops generally from Raleigh to
the north and east, with areas to the north of Raleigh still having
a slight chance of showers into the afternoon. Friday will be
another windy day because of a tight pressure gradient, with wind
gusts ranging from 30 mph across the Triad to 40 mph in the
southeast across Sampson County.

There will be a brief break in rain Friday night, but an upper level
shortwave should bring a chance of showers Saturday afternoon across
the Triad and most of the area Saturday night. Temperatures still
look very marginal for supporting snow, and even if there were a few
snowflakes, the ground should remain too warm to allow any snow to
stick. High pressure will yield another short period of dry weather
Sunday, Sunday night, and Monday morning. After that, low pressure
will move over New England, dragging a cold front across the region.
Behind the cold front, high pressure will attempt to build in from
the north, but models are on the fence as to how far south the front
will drop before coming stationary. Have continued chance pops
Monday night through Wednesday.

As for temperatures, Friday will be a transition day, with highs
still a couple degrees above normal before dropping below normal on
Saturday. Temperatures return to normal on Sunday, then rise above
normal again Monday through Wednesday.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 655 PM Wednesday...

A strong storm system approaching slowly from the west will bring
adverse aviation conditions to central NC. Aviation conditions are
likely to remain poor for the next 24 hours at INT/GSO as IFR to
LIFR cigs with periods of MVFR vsbys in patchy rain are expected to
dominate. These showers will become steady and heavier after 13z
Thu, when vsbys may drop to IFR or LIFR. Further E, at RDU/RWI/FAY,
cigs will be mostly MVFR (and perhaps briefly VFR this evening) with
spotty showers through tonight. But as more steady rain pushes E
into central NC after daybreak Thu, cigs should lower to mostly IFR
by late morning (after 15z) at RDU/RWI/FAY, although VFR to MVFR
cigs and VFR vsbys may persist at FAY into Thu afternoon. Surface
winds will be mainly from the S or SSW under 10 kts through much of
tonight (although northern terminals will be from the SE briefly
this evening as a backdoor front sags into the area), however winds
will then increase from the SW just before dawn to 10-15 kts gusting
to 20-28 kts, continuing through Thu, with the strongest winds at
eastern terminals (RDU/RWI/FAY). Winds will be very strong aloft, 60-
70 kts from 5000 to 10000 ft AGL, presenting potential mechanical
turbulence and problems with handling some aircraft Thu. While we
are expecting an increased risk of storms after about 15z Thu, given
the isolated nature of the storm threat and with the focus in the
last 6-9 hours of the forecast where uncertainty in the details is
greatest, will not carry thunder as a prevailing condition at this
time. However, aviators should expect a line of showers and storms
to cross central NC from mid afternoon through early evening Thu.

Looking beyond 00z Fri, poor aviation conditions with strong gusty
winds and heavy rain ahead of the approaching front will dominate
through the rest of Thu evening. Rain should taper down W to E
overnight but it will remain blustery with sub-VFR cigs likely
through at least Fri morning. Cigs should lift to uniformly VFR Fri
afternoon with VFR vsbys and winds shifting to be from the WNW,
still gusty through the rest of the day. Clearing is expected Fri
night, but a risk for sub-VFR conditions and brief precipitation is
possible late Sat and Sat night with a passing disturbance. VFR
conditions should follow for Sun/Mon. -GIH

&&

.HYDROLOGY...
As of 555 PM Wednesday...

Heavy rainfall remains very likely Thu and Thu night, particularly
over the NC Piedmont and points westward into the mountains.
Increasing deep moisture transport and surging PWs to daily record
values in the presence of strengthening forcing for ascent through
the column will lead to heavy rainfall, and the orientation of
convective bands parallel to the steering flow will result in slow
movement and higher rainfall amounts. Storm totals of 2-5" are
expected from tonight through Fri morning from the Triangle west,
with 1-2" totals in the east. This rainfall over the headwaters of
expansive basins will push many mainstem rivers near or over flood
stage, including parts of the Dan, Yadkin, Haw, Deep, Rocky, Cape
Fear, Neuse, and Tar Rivers and their tributaries. Flashier rivers
like the Haw will see quicker response Thu into Thu night, resulting
in a good chance of moderate or greater flooding. While most other
sites are currently expected to peak at minor flood, we`ll keep a
close eye on upstream rainfall as this event unfolds. River flooding
may extend well into the weekend over eastern sections as this
rainwater flows through the tributaries and downriver. -GIH

&&

.CLIMATE...

Record high minimum temperatures for February 5.

Raleigh area...      60 degrees (1890)
Greensboro area...   53 degrees (1943)
Fayetteville area... 53 degrees (1957)

Record high minimum temperatures for February 6.

Raleigh area...      61 degrees (2008)
Greensboro area...   60 degrees (2008)
Fayetteville area... 63 degrees (2008)

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Flood Watch from Thursday morning through late Thursday night for
NCZ007>010-021>026-038>041-073>076-083-084.

&&

$$

SYNOPSIS...JJM
NEAR TERM...KC
SHORT TERM...Hartfield
LONG TERM...Green
AVIATION...Hartfield
HYDROLOGY...Hartfield
CLIMATE...Badgett