Area Forecast Discussion
Issued by NWS Charleston, WV-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KRLX 201055
Area Forecast Discussion
National Weather Service Charleston WV
644 AM EDT FRI MAY 20 2016
Low pressure approaches today and moves through tonight...then
shifts to our southeast on Saturday. Heavy rain threat exists
late today into this evening mostly for Ohio River Valley counties.
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --In the dawn update at 1030z...was an hour faster increasing pops
during the mid and late afternoon over southern counties...based on
rest from earlier discussion.
At 0730z...southeast wind flow increasing with lower clouds trying
to form along the eastern slopes. In the cool air...patches of fog
did form mostly in the colder sheltered mountain valleys.
Precipitable water jumps from around .5 inches at 06z to 1.5 inches
in nrn Ky and se Ohio bfr 00z Saturday.
Still concerned about a flash flood threat...but mostly in our
western counties after 20z today and lifting ne this evening. This
includes ne Kentucky...se Ohio and the mid Ohio Valley counties of
WV. The 00z nam had the 850 mb flow increasing from 15 to 20 knots
at 21z to 40 to 45 knots by 03z. Impressive. At least...there is
not a strong temperature gradient for that flow to act on. The best
850 mb moisture convergence should lift northeast today toward Sdf-
Cvg-Lex vcnty by 21z this aftn...then into the Uni-Hts-Pkb corridor
by 00z to 03z this evening. Rain amounts around 1.3 to 1.5 inches in
3 hours would start to get us concerned...but the new spring
vegetation is helping. Will not hoist a flash flood headline with
the predawn morning package but we will continue to revisit this
threat today. Mentioned the heavy rain and embedded thunder in the
area with best support. Will highlight the counties we feel are
most vulnerable in our hazardous weather outlook.
Thinking the southeast flow will help shield the Crw to Buckhannon
and Elkins...and maybe even Ckb from the heaviest rain. A secondary
rain max may be along the eastern slopes including Pocahontas County
Have moisture at 4 to 8 thsd ft increasing in southern West Virginia
this morning and spreading north. Warmest maximum temperatures
inserted toward Ckb-Buckhannon-Ekn. Counting on thicker clds and
pcpn arriving to hold Hts vcnty temperatures down a bit this aftn.
The biggest change in our hourly pops was to bring lowering pops
into our southwestern counties faster overnight...as the support
lifts into eastern Ohio and western Pennsylvania overnight after
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.SHORT TERM /SATURDAY THROUGH MONDAY/...
Main swath of 850mb Theta E convergence will have lifted well to the
northeast of the CWA by Saturday morning...so the short term will be
primarily dealing with the upper trough at 500mb with the extra lobe
dropping in from the north for Saturday night. By and large...this
will end up as the cold pool convection period as the surface low
regenerates along the mid atlantic coast and the aforementioned
500mb low all but stalls over the Delmarva Peninsula.
In the forecast grids...this has necessitated an increase of the
POPS back to the west for Sunday to low end chance that will peak
with the heating of the day. Could be difficult to get rid of the
isolated showers over the northeast mountains because of the
behavior of the upper level low...so those low chances will outrun
the lowlands from a time standpoint...lingering into Monday...as
high pressure tries to regain control.
Temperatures continue to be held in check given the lowering
heights...with slightly below average values across the board.
.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
SFC high pressure will push into the region for the start of the
new work week. This will give us some dry and warm conditions
through at least mid week.
Guidance is indicating a stationary boundary drifting over the
region by Wednesday or Wednesday night and this will not move
much through the end of the week. Several transitioning shortwaves
will bring the threat for showers and thunderstorms into Friday.
.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --The thicker fog did form in the cooler mountain valleys. Should evaporate
quickly between 12z and 13z.
Kept confidence at medium for coverage of heavier showers after 21z.
Moisture/clouds at 4 to 8 thsd ft should increase over southern WV
06z to 14z...and spread north today...lowering further over the eastern
On the 00z nam...the strongest 850 mb moisture convergence lifts out
of western Tennessee early today...through central Kentucky...and
into southeast Ohio this evening. at 1030z...heavier showers were forming
in western Tennessee.
Will have ceilings and vsby lowering in the Hts-Uni-Pkb corridor before
00z. With that support...also included embedded thunder in ne Ky...Hts
vcnty and se Ohio. Will include vcnty thunder in the hts taf
Figuring the southeast flow will keep Crw to Ekn in better shape in
the rain showers in terms of ceilings at least. In contrast...the same
southeast flow should lower ceilings after 23z in the eastern slopes including
the Bkw vcnty.
Between 06z to 12z...coverage of showers decreases...as bulk of activity lifts
north and east...with ceilings mostly 2 to 4 thsd ft.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z SATURDAY...
ALTERNATE SCENARIOS: Duration of the heavier showers late this afternoon and
this evening at any one location could be less than window mentioned in tafs.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
UTC 1HRLY 10 11 12 13 14 15 16 17 18 19 20 21
EDT 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17
CRW CONSISTENCY M H H H H H H H H H H H
HTS CONSISTENCY H H H H H H H H H H H M
BKW CONSISTENCY H H H H H H H H H M M M
EKN CONSISTENCY L M H H H H H H H H H H
PKB CONSISTENCY H H H H H H H H H H H H
CKB CONSISTENCY H H H H H H H H H H H H
AFTER 12Z SATURDAY...Ifr possible in low ceilings in Ohio Saturday morning...
and possible throughout area overnight Saturday night into Sunday morning.
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