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Area Forecast Discussion (AFD)

Issued by Huntsville, AL (HUN)

FXUS64 KHUN 250529

Area Forecast Discussion
National Weather Service Huntsville AL
1229 AM CDT Sun Jun 25 2017

For 06Z TAFS.


.NEAR TERM...(Tonight)
Issued at 808 PM CDT Sat Jun 24 2017

Significantly quieter weather across the Tennessee Valley this 
evening as opposed to the last couple of evenings as "drier" air
continues to the filter into the region. The latest surface analysis
shows a frontal boundary stretching from the NC/SC coastal plain
across central Georgia and into southern AL/MS. In its wake, high
pressure continues to slowly build across north Alabama with light
northerly flow and dewpoints in the lower to middle 60s. Infrared
imagery and the last few visible images for today show scattered to
broken mid/high clouds streaming across the area so not expecting
completely clear skies overnight. Given some continued surface
gradient and cloud cover along with drier air filtering in not
anticipating too many fog issues. Will issue quick update to account
for temp/sky trends but no major changes are planned.

One quick hydro note, the Paint Rock at Woodville crested early today
below action stage and is now falling steadily. However, we are
monitoring the Flint River at Brownsboro which has risen to 16.6 feet
or about 1/2 a foot below flood stage. 

.SHORT TERM...(Sunday through Tuesday)
Issued at 240 PM CDT Sat Jun 24 2017

The forecast area will remain beneath a broad cyclonic flow regime  
on Sunday/Sunday night, although mid-level winds are expected to veer
more to the west-northwest as the subtropical ridge weakens and 
retreats to the east while the Great Lakes vort max dampens and 
ejects northeastward into New England. At the surface, a reinforcing 
dome of high pressure will build southeastward across the Great 
Plains on Sunday...providing a steeper pressure gradient and a 
maintaining north-northeast flow around 10 knots. Although CAA will 
not be particularly strong, forecast soundings from the NAM/GFS/ECMWF
all indicate that an early morning inversion will be slow to mix out
through the day...and this should translate to high temps a few 
degrees cooler than those observed today. Scattered mid and high- 
level clouds will prevail through the day, but may diminish 
sufficiently tomorrow night to allow for stronger radiational 
cooling. Lows on Monday morning have been adjusted to reflect this, 
with most locations falling into the m50s-around 60. Conditions will 
also be favorable for early morning fog development...especially in 
valleys and near large bodies of water...and this has been included 
in the forecast.

A slightly stronger mid-level wave forecast to dig into southern  
Ontario by 12Z Monday should lead to gradual amplification of the 
broader longwave trough Monday night/Tuesday. The base of this trough
will likely spread southeastward across the region on Tuesday...but 
with synoptic scale ascent expected to be maximized late Monday night
a low chance POP for light showers has been included for the 
northern half of the region between 27/06-12Z. Based on the dry 
nature of the boundary layer, the coverage of any shower activity 
should be quite low. Regardless, an increase in cloud cover during 
the same period should result in slightly warmer low temperatures on
Monday night/Tuesday morning. Any lingering precipitation/cloud 
cover will rapidly clear the region by 18Z Tuesday...with afternoon 
temps warming into the l80s once again.

.LONG TERM...(Tuesday night through Friday)
Issued at 240 PM CDT Sat Jun 24 2017

The TN Valley will be on the western periphery of a departing  
longwave trough, with northwest flow over much of the region at the 
start of the long term period. This trough will shift off the 
Atlantic coast early Wednesday morning as a broad upper ridge builds 
into the central CONUS. After a rather cool start on Wednesday 
morning, with temps dropping into the upper 50s, a moderating trend 
will begin and persist through the end of next week. The subtropical 
ridge tries to build northward into the region, with winds shifting 
to the south. This will filter in warm and moist Gulf air to the TN 
Valley, bringing us our more typical conditions expected for late 
June. Temperatures will generally warm into the mid to upper 80s each
afternoon, and overnight lows will drop into the 60s. Rain returns 
to the forecast area beginning on Thursday, as moisture continues to 
advect into the region. This will bring a return of diurnally driven 
thunderstorms Thursday and Friday afternoon, which will diminish 
after sunset each night. The better rain chances look to be on 
Friday, as a trough digs through the Central Plains and into the MS 
and TN Valleys, helping aid in the diurnally driven convection.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1130 PM CDT Sat Jun 24 2017

High pressure continues to build slowly into the region on the heels
of a cold front sinking toward the Gulf Coast. The result will be VFR
conditions across the Tennessee Valley over the next 24 to 48 hours
with primarily middle and high clouds through the day on Sunday.
Northerly winds may be briefly gusty at times on Sunday during peak 





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at weather.gov/huntsville.