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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 77 °
• Low: 59 °
• T-Storms

• Thursday
• 
• High: 81 °
• Low: 61 °
• Chance of T-Storms

• Friday
• 
• High: 82 °
• Low: 64 °
• Fog

• Saturday
• 
• High: 88 °
• Low: 66 °
• Chance of T-Storms

• Sunday
• 
• High: 86 °
• Low: 66 °
• Clear

Area forecast discussion 
National Weather Service Blacksburg Virginia 
755 PM EDT Tuesday may 22 2012 


Synopsis... 
a cold front slowly pushes east across the area through tonight...and 
then to the coast by late Wednesday. Showers and 
thunderstorms...with some potentially bringing heavy rain...will 
be possible through Thursday. High pressure and drier weather will 
arrive late in the week. 


&& 


Near term /through Wednesday/... 
as of 630 PM EDT Tuesday... 


Made some adjustments to probability of precipitation and temperatures according to latest radar 
trends and observations. 


As of 330 PM EDT Tuesday... 


Main threat continues with slow moving convection into this evening 
as storms develop along the ridges and then only slowly propagate 
north/NE in clusters. Appears heaviest rainfall will occur across the 
far west early on but likely develop east via outflow into better 
instability which remains aligned across the central County Warning Area. However 
this region was worked over to some degree since yesterday so better 
coverage may end up across the southeast this evening. Severe threat looks 
to be more of the pulse/microburst type as suggested by high windex 
values but limited by the cap aloft off soundings. Therefore will 
keep likely/Cat probability of precipitation going mountains where the Flood Watch will be 
maintained for now until midnight and edge some higher likely probability of precipitation 
out to the southeast where coverage may eventually developing in from the 
south by this evening. Otherwise will slowly decrease coverage later this 
evening given loss of heating but continue some probability of precipitation overnight with 
the upper low just south and the old front lingering along the Blue 
Ridge. Moist conditions with some breaks should again lead to 
patchy/areas of fog so included late. Lows again similar to the last 
couple of nights...mainly 55-62. 


Upper low and the associated 500 mb cold pool will pass just southeast of the 
area on Wednesday while enhancing the low level southeast flow into juicy moisture 
already in place. Models however differ on placement of best lift 
with some focused along the Blue Ridge and others in more of a 
banded nature across the north and west around the upper low. Also 
concern about seeing more clouds linger longer on the north side of 
the upper system similar to what happened to our SW today per the 
latest cooler NAM. Since the GFS/local WRF appear best with more of 
a conveyor belt a bit farther north and low level convergence out 
west will follow closer to these solutions at this point. This would 
suggest more heavy rain potential north half as steering aloft still 
weak and lower probability of precipitation south/SW in an area of less upper diffluence 
nearer the upper low. Degree of heating/instability will ultimately 
drive the convective coverage but may again need another watch Blue 
Ridge/north where more training bands appear possible. Since not as 
clear cut as today and guidance showing less pop/quantitative precipitation forecast will keep 
likely to chance probability of precipitation going and mention heavy rain again in the severe weather potential statement. 
MOS temperatures again showing quite a spread for highs and basically going 
with a comp pending amount of sunshine which if more could push the 
east above 80...otherwise mainly 70s elsewhere for now. 


&& 


Short term /Wednesday night through Friday night/... 
as of 330 PM EST Tuesday... 


Shower and thunderstorm activity will diminish gradually Wednesday 
evening as daytime heating ends...but expect isolated shower 
activity to continue through the early morning hours of Thursday as 
the upper level cutoff low remains parked over our region. Continued 
southerly flow...as well as debris cloud cover...will help keep our 
overnight temperatures on the mild side...with upper 50s expected 
across the mountains...and low 60s across the piedmonts. 


The weather pattern does not change much for Thursday...although the 
upper low begins to gradually open up during the morning and shift 
northeast. Regardless...will see another round of scattered showers 
and thunderstorms develop by late morning...with greater chances 
across the mountains. Upper level winds will remain light across our 
area...which will result in very slow moving storms...capable of 
producing prolonged periods of heavy rain. A few of these storms may 
pulse up to severe intensity for brief periods of time...producing 
large hail and gusty winds...before quickly weakening again. 


For Friday...the upper level trough will slide northeast of our 
area...and an upper level ridge of high pressure will begin to edge 
north from the central Gulf Coast region. As such...will still see 
showers and thunderstorms develop during the afternoon...but do not 
expect them to be as widespread across our area. Afternoon 
temperatures will also be a little warmer as the upper ridge draws 
near...with highs reaching into the upper 70s west to the middle 80s 
east. 


&& 


Long term /Saturday through Tuesday/... 
as of 330 PM EDT Tuesday... 


Looking into Saturday...will see another round of widely scattered 
afternoon showers and thunderstorms...mainly across the 
mountains...as a weak cold front sinks southward from the Great 
Lakes...before stalling out across the Ohio River valley...and 
eventually lifting back to the north. Any shower and thunderstorm 
activity will diminish quickly with sunset and the end of daytime 
heating. 


Through the remainder of the weekend into the early part of next 
week...an upper level ridge of high pressure will take over our 
weather pattern...resulting in very Summer like temperatures. We can 
expect afternoon temperatures to range from the upper 70s and low 
80s across the mountains...to the middle 80s to near 90 degrees across 
the piedmonts. With the upper level ridge situated along the Ohio 
River valley into our area...temperatures aloft will remain warm 
enough to keep afternoon shower and thunderstorm activity isolated 
across our area. 


Beginning Tuesday...the upper level ridge begins to break down...and 
shower and thunderstorm activity will become more widespread across 
our area as another cold front approaches from the west. With the 
increased cloud cover and shower activity...afternoon temperatures 
will be cooler...and much closer to normal. 


&& 


Aviation /00z Wednesday through Sunday/... 
as of 745 PM EDT Tuesday... 


Scattered MVFR convection with local IFR conditions this evening 
will diminish slowly tonight with the loss of solar heating. 
Areas of fog may develop where thunderstorms formed. Again will 
be a night similar to last night where ceilings/visibilities could fluctuate 
between LIFR to VFR at times...so went toward middle Route of 
IFR...mainly with fog instead of lower ceilings. Any location that 
does see heavy rain could drop into LIFR after midnight and not 
see much improvement until middle morning Wednesday. 


Scatterd showers and thunderstorms will develop Wednesday 
with the best coverage of storms shifting north of a line from blf- 
lyh. Mainly VFR after morning fog/lower clouds except in heavier 
thunderstorms and rain. 


Looking at the pattern shifting toward the end of the week...and 
until Friday should see nighttime threat of lower ceilings/fog and 
daytime thunder. By Friday will see high pressure working in to 
bring VFR weather...and temperatures heat up. Nighlty fog in the 
valleys bcb/lwb a good possibility given the ground should be 
moist...with little wind. 


&& 


Rnk watches/warnings/advisories... 
Virginia...Flash Flood Watch until midnight EDT tonight for vaz007- 
009>020-022>024. 
NC...Flash Flood Watch until midnight EDT tonight for ncz001-002- 
018. 
WV...Flash Flood Watch until midnight EDT tonight for wvz042>045. 


&& 


$$ 
Synopsis...jh/pw 
near term...jh/kk 
short term...nf 
long term...nf 
aviation...jh/kk