Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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FXUS64 KMRX 241912

Area Forecast Discussion
National Weather Service Morristown TN
312 PM EDT Thu May 24 2018

.SHORT TERM...(Tonight and Friday)...

Convection this evening should decrease with the loss of daytime
heating. May have some patchy fog in areas that received rainfall
today, but clouds may limit it somewhat in southern portions of
the forecast area. With ample boundary layer moisture and ridging
in place, min temperatures remain about 10 degrees above normal.

Ridging begins to break down on Friday with southerly flow
advecting in additional moisture. In addition, a surface trough
and area of convergence currently in central GA will move
northward during the day as southerly flow increases. Still expect
to see a majority of convection develop across the higher
elevations of the TN/NC mountains and the southern plateau where
the greatest combination of moisture and lift will be co-located.
With ridging breaking down and additional cloud cover, expect
temperatures to be several degrees cooler than Thursday.

.LONG TERM...(Friday night through Wednesday)...

The extended fcst period kicks off on Friday night amidst deep
ridging aloft, while high pressure at the surface weakens. Sustained
southerly flow will yield increasing moisture through the profile
each day through the weekend with dewpoints holding in the mid/upper
60s to lower 70s. Little in the way of synoptic forcing is favored
across the southern Appalachians through the weekend, therefore the
fcst will lean heavily on a diurnal convective trend, with pops
generally featured in the high chance to likely range Saturday and
into Sunday.  By Sunday the focus begins to shift toward the Gulf of
Mexico where a tropical disturbance is progged to lift northward
onshore across the FL gulf coast.  With that, the overall upper
ridge over the western Atlantic looks to slow the system and keep
any forward motion generally more westward.  Long range guidance
currently suggests this system meandering over south AL/GA and north
FL through at least midweek, potentially dumping large amounts of
rainfall across the I10/I20 corridors.  However in the meantime
closer to home, further enhanced moisture advection consequent of
this approaching tropical system will keep pops elevated into the
start of the new work week.  Thus, the fcst highlights mid/high
chances generally north of I40, to low/mid likely pops along/south
given proximity to deepest moisture, all mainly on a diurnal trend
given high uncertainty in the track/timing of this system. All in
all, looking like a wet and potentially stormy week ahead with
temperatures remaining above normal.


Chattanooga Airport, TN             69  84  68  85 /  20  40  40  60
Knoxville McGhee Tyson Airport, TN  67  84  67  84 /  10  50  30  60
Oak Ridge, TN                       67  86  68  85 /  20  40  30  60
Tri Cities Airport, TN              62  83  64  81 /  10  50  40  60




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