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000 
FXUS62 KRAH 300744
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
335 AM EDT Sun Apr 30 2017

.SYNOPSIS...
Bermuda high pressure will extend across the Southeastern states 
today. A cold front will approach the Appalachians tonight, then 
cross the region late Monday afternoon through Monday evening. Warm 
high pressure will build in from the southwest Tuesday through 
Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 320 AM Sunday...

Little change required to the near term forecast.

Another warm day in store for much of central NC though high 
temperatures will average about 3 degrees cooler compared to highs 
observed on Saturday. The slightly lower max temps can be attributed 
to the potential for morning stratus to linger longer than Saturday, 
reducing the amount of insolation for the first part of the day, 
especially across the Piedmont, and to a weakening of the mid-upper 
level ridge. Highs should range from the lower 80s across the nw 
Piedmont to the mid-upper 80s elsewhere. While an isolated shower 
cannot be ruled out, primarily across the western Piedmont, coverage 
expected to be too limited to mention a PoP at this time. 

A mature cyclone over the central U.S. will lift slowly newd 
tonight. The approach of this system coupled with an area of high 
pressure anchored offshore will tighten the pressure gradient over 
central NC, especially after 06Z, resulting in a steady sly sfc wind 
overnight. This sly flow will maintain a warm moist low level air 
mass, leading to the development of a low cloud deck overnight. The 
cloud cover along with a steady sly flow will maintain warm 
overnight temperatures in the mid-upper 60s.

&&

.SHORT TERM /Monday and Monday night/... 
As of 335 AM Sunday...

A cold front associated with the mature cyclone lifting newd across 
the upper Midwest Monday will approach from the west late in the day 
and cross central NC late Monday night. The air mass ahead of the 
front will become convectively unstable with MLCAPE values off of 
the GFS in the 500-1000J/Kg range (and this model is typically too 
stable in this type of set-up). Meanwhile adequate shear for 
organized convection will be in place thanks to a low level jet 
around 40-45kts crossing overhead Monday afternoon. The latest 
convective allowing models suggest isolated-scattered 
showers/isolated t-storms crossing the Piedmont late Monday morning 
through early afternoon, with an increasing threat for a broken line 
of organized convection crossing the Piedmont late Monday afternoon-
Monday evening, and into the coastal plain and Sandhills Monday 
evening-Monday night. At this time, a few strong/severe storms will 
be possible, primarily across the Piedmont due to the favorable 
timing of late afternoon when low level instability is maximized. 
Appears the main severe weather threats with the stronger storms 
will be large hail and damaging straightline winds. 

Breezy south-sw winds will occur ahead of the front Monday afternoon 
with gusts 25-30 mph probable across the region.

High temperatures Monday dependent upon shower extend in the late 
morning-early afternoon and thickness of cloud cover. Feel fairly 
confident that locations along and east of highway 1 will reach the 
low-0mid 80s due to later arrival of showers. Favor max temps in the 
west in the upper 70s-lower 80s though if shower coverage is much 
less than expected, high temps 80-84 will be more probable. 

Bulk of showers and storms should be east of highway 1 by 03Z, and 
exit the coastal plain counties of central NC by 06Z-08Z. Cooler 
more stable air will gradually filter into our region after 06Z, 
though not likely reaching our eastern periphery until close to 
daybreak. May see a 10 degree spread in the overnight temperatures, 
ranging from the mid 50s in the west to the low-mid 60s along the I-
95 corridor.

&&

.LONG TERM /Tuesday through Saturday/...
As of 315 AM Saturday... 

Tue/Tue night: A strong mid level low will track from the northern 
Great Lakes NE over E Canada as it fills Tue/Tue night. The surface 
front will be pushing off the NC coast early Tue, with falling lapse 
rates, much drier air, and a shift in low to mid level flow to 
westerly by Tue night. A very dry and stable column, with weak mild 
high pressure building in from the SW, will ensure plenty of 
sunshine and good mixing. Thicknesses start out slightly below 
normal, countered by strong heating, and expect near-normal highs of 
75-81, with a WSW breeze. Passage of a weak mid level perturbation 
Tue night should bring some high cloudiness, but otherwise expect 
fair skies and lows in the lower-mid 50s.

Wed/Wed night: By midweek, the fairly flat and westerly steering 
flow across the SE quarter of the CONUS will give way to a deep 
digging longwave trough over the Southern Plains, resulting in a 
backing of our mid level flow to SSW and an increased number of weak 
waves traversing the area. The most pronounced of these waves moves 
NE across W NC Wed night, helping to moisten the column above 600 mb 
overnight and foster a trend to mostly cloudy skies west, partly 
cloudy east. At the surface, a diffuse frontal zone is expected to 
dip southward into the Mid-Atlantic region but stay to our north as 
the weak surface high pressure drifts overhead and offshore, keeping 
NC within a light mainly southerly flow Wed night. Models continue 
to slow the progression of any prefrontal warm advection showers Wed 
night, although I still think isentropic and terrain-influenced 
upglide is possible near the mountains/foothills Wed night, 
resulting from a light but long-fetch low level Atlantic inflow, so 
have retained a slight chance of light showers over the far W 
Piedmont Wed night. Expect slightly warmer temps Wed, especially S, 
with highs of 77-83. Warm lows Sat night with the increase in 
clouds, 58-62. 

Thu-Sat: The weather becomes much more active, but forecast 
confidence in the details plummets. The GFS shows the aforementioned 
digging longwave trough cutting off over the mid and lower Miss 
Valley then drifting eastward over the Mid South and Gulf/Southeast 
states through Sat, before becoming phased with a northern stream 
trough and shifting east and offshore as a deeply amplified trough 
along the East Coast on Sun. The ECMWF, on the other hand, keeps its 
southern stream trough more open and nearly phased with the northern 
stream as it progresses more quickly over the E CONUS Thu-Sat. Both 
models have vacillated in recent runs between a more closed/slower/ 
deeper system and more open/faster one, and the GEFS mean is 
actually closer to the ECMWF than the GFS, thus confidence is lower 
than usual. But both operational models do focus the greatest chance 
of showers/storms Thu-Fri, so will place the highest pops then, with 
a lower chance Sat with expectations of the longwave trough axis 
either shifting overhead or just to our east as we head into the 
weekend. The risk of strong to severe storms appears to be greatest 
Thu afternoon/evening on the ECMWF and Fri on the GFS, with both 
showing DPVA ahead of the trough, focused upper divergence, mid 
level height falls, and strong deep layer shear, although potential 
instability may be marginal with mid level warming ahead of the 
longwave trough. Will monitor and wait for models to come into 
better agreement on timing. Expect warm highs in the low 70s to near 
80 Thu, trending down to cooler than normal temps for Fri/Sat. -GIH

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/... 
As of 145 AM Sunday...

Widespread IFR/low end MVFR ceilings will develop over central NC 
after 08Z and likely persist through much of the morning hours. 
Ceilings should lift dissipate in the 15Z-18Z time frame with a 
scattered cumulus cloud field highly probable this afternoon. Any 
showers that occur will be very isolated and limited to the 
Yadkin/Pee Dee River Valley. 

Low stratus expected to once again envelope most of central NC after 
05Z Monday and linger into the first half of Monday morning. An 
approaching cold front will increase the threat for a few showers in 
the western Piedmont by late Monday morning. Showers and a few 
thunderstorms will increase in coverage across central NC Monday 
afternoon and Monday evening as the cold front is in our vicinity. 
MVFR ceilings/visibility highly probable in proximity to the heavier 
showers and storms. Proceeding the front, sfc winds will be gusty 
out of the south-southwest with gusts 25-30 mph probable Monday 
afternoon.  The showers and storms should exit the coastal plain 
counties of central NC shortly after midnight.

VFR conditions anticipated behind the cold front Tuesday into 
Wednesday. Another low pressure system will approach from the west-
southwest by Thursday, increasing the risk for sub VFR ceilings and 
scattered showers.


&&

.Climate...

Daily Record High Minimum Temperatures

April 30 /
Greensboro... 64 (1970)
Raleigh.......65 (2014)

May 1 /
Greensboro... 65 (2012)
Raleigh.......67 (2012)

The all time April Monthly Record High Minimum Temperatures

Greensboro... 68 set April 14, 1912 - then tied on April 23, 1920 
and April 27, 2011.

Raleigh.......71 set on April 14, 1922 - then tied on April 25, 
1925. 

&&

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

&&

$$

SYNOPSIS...Hartfield

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