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Nowcast

• 

• Now as of 7:02 PM EDT on May 22, 2012

  Scattered showers and thunderstorms will continue to develop along the higher terrain areas of east Tennessee...and southwest North Carolina. These storms are nearly stationary...drifting slowly southward...producing rainfall amounts up to 2 inches per hour in a few locations. However...most areas will see significantly less.

Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 79 °
• Low: 54 °
• Chance of T-Storms

• Thursday
• 
• High: 84 °
• Low: 61 °
• Chance of T-Storms

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

• Saturday
• 
• High: 90 °
• Low: 64 °
• Chance of T-Storms

• Sunday
• 
• High: 90 °
• Low: 64 °
• Partly Cloudy

Area forecast discussion 
National Weather Service Morristown Tennessee 
743 PM EDT Tuesday may 22 2012 


Aviation...convective precipitation will linger with at least 
scattered coverage through midnight...as an upper low/vorticity maximum moves 
NE from southern Georgia. Lightning strikes have been diminishing so limited 
to cumulonimbus/thunderstorms in the vicinity for just cha and tri for now. 


Precipitation amounts have been light so far for taf sites...so 
convective debris clouds should inhibit dense fog from developing. 
Convection will likely develop again in the heat of the afternoon 
on Wednesday...but it seems premature to try to pin down exactly 
where. Thus...I went for VFR conditions and just vcsh. 


Previous afd... 


Short term (tonight and wednesday)... 
convection very slow to move this afternoon as weak trough hangs 
over area. Much of the energy for the trough has headed south with 
vorticity maximum/possible upper low that's about to cross into SW Georgia. 
Persistent rains over Cumberland Plateau are mainly from diurnal 
heating and should dissipate this evening. Likewise much of the 
showers and storms over the area now will likely dissipate this 
evening. Best chances overnight will be in the east and northeast 
where upper level difluence keeps some slow lift going through the 
night. Keeping quantitative precipitation forecast values fairly light...considering some of the 
flow is having to Cross Mountain ridges to get into the area. 


For Wednesday...the upper trough axis should be east of the 
area...but a spoke or two of lift may sweep through the northeastern 
areas...making for better precipitation chances. 


For temperatures...went close to guidance...but slightly cooler for maximum 
temperatures Wednesday in northeast due to thicker cloud cover. 


Long term (wednesday night through tuesday)... 
the main forecast concerns for the extended period continue to be 
precipitation chances Wednesday evening into Thursday from a 
departing upper-low and the unseasonably warm temperatures expected 
for the Holiday weekend. 


An upper-level low pressure system will be slow to exit the southern 
Appalachians region as models still are showing it centered over 
west central North Carolina by 00z on Thursday. The potential for 
scattered showers and thunderstorms will persist into the evening 
hours Wednesday as some wrap around moisture infiltrates the eastern 
zones on the backside of the low. On Thursday...precipitation 
chances will be lessened as this storm system begins to track into 
the Middle Atlantic States. However...the potential for some lingering 
activity across the northeastern zones will exist during the 
morning...along with some orographically induced convection along 
the mountains during the afternoon. 


In the wake of this system...a strong upper-level high pressure 
ridge will move across the lower-Mississippi Valley and into the 
Tennessee Valley/southern appalachian region this weekend. With 
increased thickness values and 850 mb temperatures prognosticated to warm 
5-6c to around 20-21c by Saturday/Sunday...some near record to 
perhaps record highs will be possible this Memorial Day weekend. By 
Friday...highs in the lower 90s will be common across most of the 
area...and this weekend the Mercury could approach the middle 90s in 
some locations. By Memorial Day...the center of the ridge will shift 
east of the area...but warm temperatures in the upper 80s to around 
90 degrees are still expected to close out the Holiday weekend. Some 
increased precipitation chances and some cooler temperatures may be 
on the horizon heading into early next week as an upper-level storm 
system begin to track toward the Great Lakes/Ohio Valley. 


Climate... 
daily record highs may 25th through may 28th: 


... 
May 25th: 95 degrees /1953/ 
may 26th: 94 degrees /1962/ 
may 27th: 95 degrees /1911/ 
may 28th: 95 degrees /1962/ 


... 
May 25th: 93 degrees /2011/ 
may 26th: 94 degrees /1926/ 
may 27th: 94 degrees /1941/ 
may 28th: 94 degrees /1914/ 


..Tri Cities... 
May 25th: 90 degrees /1953/ 
may 26th: 89 degrees /1991/ 
may 27th: 89 degrees /1941/ 
may 28th: 92 degrees /1941/ 




&& 


Preliminary point temps/pops... 
Chattanooga Airport, Tennessee 60 83 61 89 65 / 30 30 10 10 10 
Knoxville McGhee Tyson Airport, Tennessee 60 80 59 87 64 / 50 50 10 10 10 
Oak Ridge, Tennessee 60 82 60 87 64 / 50 50 10 10 10 
Tri Cities Airport, Tennessee 56 78 55 84 57 / 70 50 30 20 10 


&& 


Mrx watches/warnings/advisories... 
NC...none. 
Tennessee...none. 
Virginia...none. 


&& 


$$ 


Tg/GM/amp