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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 79 °
• Low: 57 °
• T-Storms

• Thursday
• 
• High: 77 °
• Low: 61 °
• T-Storms

• Friday
• 
• High: 86 °
• Low: 61 °
• Chance of T-Storms

• Saturday
• 
• High: 88 °
• Low: 63 °
• Chance of T-Storms

• Sunday
• 
• High: 88 °
• Low: 64 °
• Chance of T-Storms

Area forecast discussion...updated 
National Weather Service Blacksburg Virginia 
1152 am EDT Wednesday may 23 2012 


Synopsis... 
an upper level area of low pressure over the western Carolinas 
Wednesday will slowly move northeast and be centered over 
Virginia Thursday...then exit the region Friday. High pressure 
will build across the area for the weekend. 


&& 


Near term /through tonight/... 
as of 1145 am EDT Wednesday... 


Updating to make some downward adjusts to temperatures given thick cloud 
canopy over the west and scattered convection over the far north and 
west. Appears some locations across the southeast may be able to push 80 
degrees as drying works in from the south but appears going highs 
too warm elsewhere espcly based on the new NAM numbers. This may keep 
some mountain locations in the 60s unless more breaks develop 
later on. Also delayed onset of deeper convection central and SW 
sections where seeing less instability and expect only light 
showers for a few more hours if not longer. 


As of 1010 am EDT Wednesday... 


Upper low tracking across S Carolina this morning with the 
residual front across the southeast where seeing a weak surface low ride 
up the front. This was responsible for the earlier heavy rainfall 
overnight with plenty of leftover low clouds now stuck across 
much of the region north of the upper system in the rather deep 
onshore flow seen on morning radiosonde observations. Latest guidance indicating 
plenty of diffluence aloft across ther region through the 
afternoon with the deeper moisture axis gradually shifting north 
through later today. This in combo with high precipitable waters  and east/southeast flow 
should again set the stage for slow moving multicell heavy rain 
producing bands but all dependent on how much sun and subsequent 
instability develops. Latest model cloud fields suggest clouds 
will diminish during the afternoon but may be a bit slower given 
expanse of low deck early on. Modified morning radiosonde observations do show 1-2k 
j/kg convective available potential energy provided decent heating with mean flow again of 5-10 
kts. However wet bulb values and windex numbers a bit less so 
appears a bigger heavy rain than severe threat outside of pulse 
storms at this point. Thus will bump up probability of precipitation a bit more espcly 
north per local WRF quantitative precipitation forecast and add afternoon heavy rain mention after 
delaying coverage this morning. However still not confident enough 
where locations of more widespread heavy rain may be to hoist a 
Flash Flood Watch at this point. Bumped down highs some in the 
south and west per early clouds while keeping most in the 70s as 
supported via morning thickness. 


As of 400 am Wednesday... 


Upper low easily discernible on morning water vapor imagery... 
spinning over South Carolina...is prognosticated to lift northeast 
across North Carolina today. This will place most our our County Warning Area 
within diffluent zone with vigorous dynamic lift generating 
considerable cloud cover along with scattered to numerous showers 
and thunderstorms. Showers are likely across most of the 
County Warning Area...especially this afternoon per added instability from the 
daytime heating. May need to hoist a Flash Flood Watch for parts 
of the County Warning Area pending radar trends of the more organized deep 
convection. At this time believe greatest threat for potential flooding 
would be along the eastern slopes of the Blue Ridge where 
southeasterly upslope component would aid in the enhancement of 
rainfall. However...can't rule out water issues anywhere within 
the County Warning Area per fact that storm cells will be slow moving due to 
anemic looking mean wind profiles...10 kts or less. Temperatures 
today will be similar to yesterday with readings mainly in the 
70s...testing 80 degrees where more can manage to break through 
the cloud cover. 


For tonight...the upper low will gain latitude...the center 
creeping northeastward into Virginia. Similar to last night...showers 
and thunderstorms will linger into the overnight per dynamic lift 
vicinity of the upper low. Intensity however should fade per loss of 
daytime heating. Lows tonight will again be supported by cloud 
cover and dewpoints in the u50s/lower 60s...T-mins mimicking the 
dewpoints. 


&& 


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


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 /16z Wednesday through Sunday/... 
as of 800 am EDT Wednesday... 


Scattered to numerous showers and thunderstorms will develop 
this afteroon...coverage very similar to Tuesday with period of 
rain showers/thunderstorms and rain vicinity of all terminals during the afternoon. Flight 
conditions should be mainly VFR after morning fog/lower clouds 
then transistion to local MVFR/IFR vicinity of the developing thunderstorms and rain 
during the afternoon. 


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...none. 
NC...none. 
WV...none. 


&& 


$$ 
Synopsis...PM 
near term...jh/PM 
short term...nf 
long term...nf 
aviation...PM