Area Forecast Discussion
Issued by NWS Charleston, WV

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FXUS61 KRLX 282326
AFDRLX

AREA FORECAST DISCUSSION
National Weather Service Charleston WV
726 PM EDT Wed Oct 28 2020

.SYNOPSIS...
Significant rain event begins tonight with Zeta passing close by
and other systems converge. Drier Friday and Saturday. Next
cold front to arrive on Sunday.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 245 PM Wednesday...

Warm front pushing up from the south is already spreading a rain
shield into the southern zones, marking the beginning of an
extended period of rain across the CWA. The rain over the next
24 to 36 hours will be driven by a combination of this warm
front, a land falling Zeta accelerating northeastward into the
southern Appalachians, a desert southwest upper low ejecting
into the southern plains, and a weaker northern stream upper
level trough moving into the Great Lakes. The forcing mechanisms
will be plentiful. Expecting multiple waves aloft to ripple
through tonight and several bands of strong deformation/f-gen to
push through tonight and Thursday, including a stronger one
north of the Ohio River. There will be some elements of larger
scale ascent combined at times with overrunning/isentropic
lift. High PWAT/saturated atmosphere provides plenty of moisture
for the whole event, although the bulk of the tropical moisture
transport will stay to the south of the CWA. The same holds
true for the leftover wind with the tropical system. Plenty
available from a pressure gradient standpoint, so some wind is
possible area wide, but off the deck, it is clear that the bulk
of the tropical system winds will be more of an issue further
south and east as evidenced by the 925mb flow. Still could be
gusty in the highest elevations of the southern CWA such as Flat
Top where 20-30mph is not out of the question, but for the most
part, the CWA on the whole is looking at 10-20mph, again with
slightly higher gusts in the mountains.

Flood Watch pushed for the mountains where the highest QPF of 2-3
inches is possible into Thursday night as the systems depart.
Lowlands will be closer to 1-2 inches, but will need to monitor the
state of the ground as basins fill over time. Minor high water
impacts are possible CWA wide, and will be constantly evaluating
those lowland areas. The relatively dry period over the last
few weeks leaves room in the creeks and main stem rivers which
will be needed in a rainfall that will hit most/all of the
basins.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 230 PM Wednesday...

Light rain will likely continue into Thursday night, gradually
tapering off from west to east as a low pressure system moves
offshore. By Friday morning, rain should be over though some
showers may linger over the mountains. Drier air will filter in
during the day as surface level high pressure builds in from
the southwest. This will allow dry weather to continue through
Saturday when high pressure will begin to drift off towards New
England.

Northwest flow will bring cold air into the area, lowering
temperatures on Friday with highs in the upper 40s to low 50s in
the lowlands and upper 30s to 40s in the mountains. Friday
night lows will likely fall near to or just below freezing.
Warmer air returns on Saturday though temperatures will still
remain just below normal.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 230 PM Wednesday...

The next chance for precipitation will be Sunday through Sunday
night when an upper level trough brings a cold front across the
area. Temperatures are projected to drop considerably as cold air
flows in behind the front. Monday`s high temperatures may very well
be a good 15 to 20 degrees below season normals and lows both Sunday
and Monday night are projected to settle at or below freezing
areawide.

During the day Monday, high pressure will return to the area and
then settles in for the duration of the long term period. Warm air
advection in the lower levels is expected to begin by Tuesday
and will gradually allow temperatures to rise back to normal
for the middle of the week.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 725 PM Wednesday...

Conditions will begin to deteriorate shortly after TAF issuance
mainly across the southern and central terminals as abundant low
level moisture and areas of stratiformed rain advects into the local
region. Long periods of IFR ceilings and visibility will start to
affect BKW first by 00Z, then spreading north to affect CRW and HTS
overnight tonight. This reasoning comes along with the LAMP and
NAM guidance with IFR/LIFR conditions developing overnight into
Thursday. AMD NOT SKED could be coded later if HTS ASOS stops
sending METARs per communication issues.

Tropical moisture from remnants of Zeta, combined with moisture
pulled by a low pressure system from the west with move across the
southern Appalachians Thursday. Ceilings should remain IFR for most
part of day Thursday mainly across the central and southern sites.
Northern sites could also see IFR conditions but it will depend how
far north the moisture travels on Thursday. Winds will generally be
light and variable through the period.

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

FORECAST CONFIDENCE: High.

ALTERNATE SCENARIOS: Timing of rain rain and category changes
could vary.

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       22   23   00   01   02   03   04   05   06   07   08   09
EDT 1HRLY       18   19   20   21   22   23   00   01   02   03   04   05
CRW CONSISTENCY  H    H    H    H    L    L    M    L    M    M    H    H
HTS CONSISTENCY  H    M    H    H    M    M    M    M    M    L    H    H
BKW CONSISTENCY  L    L    H    M    M    L    M    L    L    M    M    M
EKN CONSISTENCY  H    H    M    H    M    M    L    L    L    M    M    M
PKB CONSISTENCY  M    M    H    H    M    M    H    H    M    H    H    H
CKB CONSISTENCY  H    H    H    H    H    H    L    L    L    L    H    L

AFTER 00Z FRIDAY...
IFR to LIFR conditions continue in rain on Thursday after 18Z.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Flood Watch from midnight EDT tonight through Thursday evening
     for WVZ033-034-515>526.
OH...None.
KY...None.
VA...Flood Watch from midnight EDT tonight through Thursday evening
     for VAZ003-004.

&&

$$
SYNOPSIS...26/JLB
NEAR TERM...26
SHORT TERM...JLB
LONG TERM...JLB
AVIATION...ARJ



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