FXUS62 KRAH 252029 RRA

Area Forecast Discussion
National Weather Service Raleigh NC
330 PM EST Sat Feb 25 2017

A strong cold front will push across the region this afternoon and 
move offshore by early evening. High pressure will build into the 
area tonight and Sunday. A warm front will approach from the south 
late Monday.


As of 330 PM SATURDAY...

Deepening cyclone will lift north into Ontario and Quebec, with 
associated strong mid-upper trough over the OH and TN Valleys 
becoming negatively tilted as it progress eastward into the Mid-
Atlantic States tonight. Attendant cold front currently approaching 
the Triad will advance east through central NC through 00 to 03z.  

It will remain breezy ahead of the front, with swly sustained winds 
of 15 to 18 kts, gusting to 25 to 30 kts, with similar magnitude 
west-northwesterly wind gusts in the wake of the front through 00 to 

Dry air and a strong boundary layer mixing is proving difficult to 
overcome and will continue to limit convective coverage across the 
area through 00z, though there still remains an isolated threat for 
a severe thunderstorm across the northern Piedmont and northern 
coast plain. Weak to moderate instability(MLCAPE 500-1000 J/Kg) has 
developed in response to steep low-level lapse rates from the 
unseasonably warm temperatures and mid-level lapse rates of 7.0 to 
7.50 C/Km, left behind by the EML that pushed through the area 
earlier this morning. Impressive effective unidirectional shear of 
50 to 60 kts, coupled with inverted-V sounding profiles and DCape 
values of 1000 to 1200 J/Kg from the entrainment of dry air aloft 
will make it possible for an isolated severe storm to produce 
damaging straight line winds across the northern/northeastern tier, 
with even 40 to 50 mph winds possible in the heaviest shower. Hail 
up to size of quarters is also possible. 

Convection should be exiting the area at or by 00z, with strong post-
frontal dry cold air advection resulting in abrupt clearing and 
seasonable overnight lows in the lower 30s NW to upper 30s SE.


As of 315 PM SATURDAY... 

Flow aloft will become quasi-zonal flow in the wake of upper trough 
exiting the Mid-Atlantic region. High pressure building into the 
area from the west will quickly move offshore late Sunday night, but 
will maintain east to west surface ridging into Monday. This means 
that the cooler-more seasonable air will not stay around very long. 
Highs ranging from from mid 50s NW to around 60 SE.  

Sheared shortwave energy ejecting eastward across the Lower MS 
Valley in the progressive low-amplitude flow will bring an increase 
in high clouds late Sunday night/early morning and could temper low 
temps Sunday night. Lows in the 30s.  


As of 200 PM Saturday...

After the brief return to near normal high temperatures on Sunday,
we will have a progressive warmup back into the 70s through midweek 
as high pressure moves offshore and southwest flow ensues. Moisture 
will be on the rise, as will cloud coverage and the chance of rain 
through the midweek period. Showers are expected as early as Monday 
night in the west as a weak upper disturbance lifts northeast in 
prevailing southwest flow aloft. It's hard to find a really 
confident feature that might enhance coverage Tuesday night through 
Wednesday but we will be in the warm moist airmass with potential 
for any passing weak impulse to kick off spotty showers. Will 
maintain generally uniform low chance PoPs across the area pending 
later model resolution of these impulses. Temps will be rebounding 
on Monday into the 60s...with low to mid 70s on Tuesday and mid to 
upper 70s on Wednesday.  

A cold front driven by a rather strong shortwave moving into the 
Ohio valley will provide a focus for a line of convection Wednesday 
night in the west...with the convection moving east rapidly and 
offshore by Thursday evening. The convection will be east of central 
NC by early afternoon. This timing is not ideal to benefit from 
maximized diurnal instability, but strong upper diffluence and the 
low level convergence with a 50+ knot h85 jet will be sufficient for 
inclusion of at least a modest chance of thunderstorms at this 
point. Highs Thursday will be hampered by the onset of cold air 
advection fairly early in the day, with western areas topping out in 
the upper 50s...while the southeast might see some mid 60s.  

Dry weather and a cooler airmass will be in place Friday and 
Saturday, with highs both days mostly in the upper 50s to lower 60s.


As of 1242 PM Saturday...

24 Hour TAF Period: 

A cold front an associated broken band of showers and storms that is 
approaching the Triad at this time, will cross the area through 00z.
Weak to moderate buoyancy in place across central NC could allow in 
an uptick in convection as it moves through the area, with best
coverage expected across the northern terminals. A brief period of 
sub-VFR conditions could accompany the stronger convection with 
strong wind gust as high as 40 to 45 kts possible.  

SWLY winds of 15 to 20 kts with gusts of up 25 to 30 kts will be 
frequent ahead of the cold front, with slightly weaker post-frontal 
wind gusts from the NW into the early evening. Winds will decrease 
to around 7 to 13 mph range between 03 to 06z with VFR dominating
Sunday as cooler high pressure builds over the area. 

Outlook: The next chance for sub-VFR conditions will be Mon night, 
lasting through Tue night and perhaps into Wed, as southwest flow 
brings in low level moisture and an increased risk for showers, as 
well low stratus and fog, especially dusk through dawn.



Record highs for February 25:

Greensboro:      81 (1930)

Raleigh:         82 (1930)

Fayetteville:    85 (1930)






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