Area Forecast Discussion
Issued by NWS Charleston, WV

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774
FXUS61 KRLX 280009
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
809 PM EDT FRI MAY 27 2016

.SYNOPSIS...
Slow moving convection with heavy downpours again on Saturday.
Moist southeast flow will raise shower chance Sunday in the
mountains. Upper level ridge rebuilds next week.

&&

.NEAR TERM /THROUGH SATURDAY/...
Increased pops per thunderstorm development as needed otherwise
previous discussion follows.

Overall...no significant changes were necessary to the previous
forecast. Upper ridge along the east coast will build westward
today...with increasing heat and humidity. Isold showers and
thunderstorms...already starting to develop across the mountains
in the afternoon heat...will for the most part dissipate after
sunset...although a few may continue to linger through the evening
across the east as an upper disturbance rounds the edge of the
ridge. With a very light steering flow...generally less than
5kts...thunderstorms will be slow moving...and capable of
producing heavy downpours...with the moisture laden atmosphere in
place.

Otherwise...another warm muggy night on tap...with patchy fog
developing.

Saturday looks to be a carbon copy of today...perhaps a degree or
two warmer with ridge continuing to build westward. Afternoon
convection will fire again off the mountains...and possibly drift
westward in the southeasterly flow.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
Area sits in deep layer south to southeast flow Saturday night and
Sunday, between an upper level ridge along the eastern seaboard, and
an upper level shortwave trough lifting through the midwest. A
broad shortwave trough over the southeastern states serves almost
as an extension to the midwest one, but surface low pressure
associated with it comes ashore into the Carolinas and then
meanders northward.

It appears that the moisture associated with the system coming
from the southeastern states will be drawn northward in a
corridor up the appalachians, but no farther west. As such...have
pops going to likely in the northern mountains of WV Sunday
afternoon.

The moist corridor shifts east of the area late Sunday and Sunday
night, as the midwest shortwave turns eastward and moves across
the Great Lakes Sunday night, and then the northeastern states on
Monday. This brings us back into the diurnal thunderstorm mode for
Monday, and, as drier low level air arrives from the west in the
wake of the upper level shortwave trough, the late day
thunderstorm chance on Monday should be limited mainly to the
mountains, which will then quickly die down with the sunset.

Guidance continues to trend downward for highs on Sunday given the
moist corridor giving rise to plenty of clouds. Otherwise
temperatures were reasonable in light of the latest guidance,
with little if any change needed.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Upper level ridging rebuilds over the central Appalachians and
middle Atlantic seaboard in the wake of the exiting shortwave
trough. This leads to a dog day summer pattern for the middle
portion of the short work week, with diurnally driven
thunderstorms tending to favor the mountains per elevated heat
source.

Models begin to diverge on the strength and timing of the ridge,
which is stronger and peaks later, on Thursday, in the GFS
solution, while weaker and peaking on Wednesday in the ECMWF
solution. This model divergence continues on Friday, as the ECMWF
rolls an upper level low across southern Canada during the week,
which then pushes a cold front through the area on Friday. The GFS
has divorced itself from this solution, instead shearing out the
southern Canadian low, and dropping another southeastward through
the plains states toward the lower Mississippi valley.

The forecast does not bite on the left turn taken by the GFS, and
instead picks up on an increasing chance for showers and
thunderstorms Thursday into Friday, before turning slightly drier
and cooler late Friday and Friday night.

Temperatures close to central guidance with little change through
day 6, and then the trend toward slightly lower values.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Isold convection through about 03Z...with brief heavy
downpours...and brief mvfr/ifr conditions in vicinity of storms.

After 03Z...MVFR valley fog developing late...generally after
06Z...particularly in areas that received rainfall during the day.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z SUNDAY...

FORECAST CONFIDENCE: Medium to high.

ALTERNATE SCENARIOS: Fog may or may impact terminals, but went
with it for most sites given general clearing sky trend.

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.

DATE                                                            SAT 05/28/16
UTC 1HRLY       00   01   02   03   04   05   06   07   08   09   10   11
EDT 1HRLY       20   21   22   23   00   01   02   03   04   05   06   07
CRW CONSISTENCY  H    H    H    H    H    H    H    H    H    M    M    M
HTS CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H
BKW CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H
EKN CONSISTENCY  H    H    H    H    H    H    H    H    H    M    M    M
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 00Z SUNDAY...
No widespread IFR conditions expected.

&&

.HYDROLOGY...
The river gauge...and forecast point...at the South Side Bridge
in downtown Charleston has not be reading correctly. The NWS
hydrologist is working to correct this problem.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...None.
OH...None.
KY...None.
VA...None.

&&

$$
SYNOPSIS...TRM/JW
NEAR TERM...JW
SHORT TERM...TRM
LONG TERM...TRM
AVIATION...JW

HYDROLOGY...



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