341
FXUS61 KRLX 071911
AFDRLX

AREA FORECAST DISCUSSION
National Weather Service Charleston WV
311 PM EDT Tue May 7 2024

.SYNOPSIS...
Daily chances for showers and storms continue, with the
frequency of storms posing concern for localized flooding.
Severe storms are possible thru tonight and Wednesday night.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 1208 PM Tuesday...

Showers and storms, some strong to severe are expected in the near
term period. A large low pressure system will continue to meander
across the northern plains, sagging south tonight into Wednesday,
filling as it does so. Convection across the midwest last night into
this morning, should weaken as it continues eastward, but could
reinvigorate later this afternoon/evening as it travels eastward
towards our area into an increasingly unstable atmosphere, along
with additional rounds of storms expected overnight from additional
shortwaves crossing the area. Strong cape on the order of around
2000 J/Kg, and increasing shear of 50+ kts, along with curved
hodographs and low lcl heights, lead to threats for all hazards,
including large hail, and strong damaging winds/downbursts, and
perhaps an isolated tornado, although the greater risk for that
looks to lie to our west.  Period of greatest threat appears to be
by 20Z through 03Z.

There may be a bit of a lull in the activity for the first part of
Wednesday, but another potent wave will move through the area later
Wednesday evening into the short term period, with heavy rains and
severe weather potential, although this period damaging winds and
hail look to be the primary risks, with a lesser risk for
tornadoes, although it cannot be completely ruled out either.

In addition, increasing southwesterly flow across the area should
allow for PW values to rise into 1.4 to 1.5 inches today, and
approach 1.7 inches on Wednesday, and this with areas of saturated
soils from recent days, elected to issue a flood watch for flash
flooding across parts of the region. That will include the potential
for any convection today, plus additional rounds on Wednesday, and
continues into Thursday morning.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 310 PM Tuesday...

A complex, moisture-laden system crosses Wednesday night into
Thursday morning.

Ahead of it, a roughly west to east oriented front draped
roughly across central portions of the area lifts north
Wednesday night. Instability is maximized in an axis along the
front and present south of it Wednesday evening, and
thunderstorms quickly become possible throughout the area
Wednesday night.

Surface low pressure rides along the front, which then reverses
course and moves southeastward across the area overnight
Wednesday night into Thursday morning. instability along and
ahead of the cold front becomes increasing elevated throughout
the night time period. However, ample forcing, shear, and
moisture convergence keep showers and thunderstorms going
through the overnight and into Thursday morning.

Convective parameters peak ahead of the cold front across
southern, mainly southwestern, portions of the area Wednesday
night, and will largely depend upon how strong a nocturnal low
level jet we can develop before the front passes. While there
would be more time for this farther east, instability will
continue to maximize farther west until the front crosses. A
self-feedback mechanism is likely to modulate these factors
with MCS development, with large hail, damaging wind and even
tornadoes possible across southwest portions of the area after
sunset and through about midnight.

PW values peak in the 1.6 to 1.9 range, also dependent upon the
strength of the nocturnal low level jet. Nonetheless, with low
flash flood guidance getting lower with each round of
convection, high rainfall rates are likely amid numerous
showers and thunderstorms Wednesday night into Thursday morning,
and the Flood Watch for Flash Flooding runs through Thursday
morning to cover this scenario.

The thunderstorm threat and associated hazards wane overnight
and especially toward dawn Thursday, followed by decreasing
coverage Thursday morning, amid a deepening post-frontal/post-
MCS inversion.

A trailing mid-upper level short wave trough and reinforcing
cold front, and diurnal heating, may bring one more uptick in
showers and thunderstorms Thursday afternoon into Thursday
evening, but the thunderstorms should be far less impactful
this time given far less CAPE and lower echo tops. The weather
dries out but remains cloudy Thursday night as the second front
then reinforces the low level frontal inversion in its wake.

Central guidance reflects a mild, well above normal night
Wednesday night, and highs Thursday tempered by the post-MCS
environment, but still above normal. Lows get closer to normal
for Friday morning behind the second cold front.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 140 PM Tuesday...

The weather remains active but nowhere near as impactful in the
long term, compared with the near and short term periods.

Friday morning finds the area in west to northwest low level
flow between low pressure off to the northeast and moving away
to the northeast with its associated mid-upper level short wave
trough, and surface high pressure approaching from the west.

There is another mid-upper level short wave trough that crosses
Friday afternoon, but models evince that enough low level cool
air comes in behind the cold front to create an unbreakable mid
level inversion 6 kft agl south to 12 kft agl north. Thus, only
low top showers are anticipated, with no hail or impactful wind
gust threat even where if we do manage charge separation.

The weather dries out Friday night as the high ridges in from
the southwest. However, another mid-upper level short wave
trough and surface low intercept that ridging as they pass
north of the forecast area Saturday afternoon and evening. This
gives rise to the chance for mainly afternoon and evening
showers and perhaps thunderstorms in the mixed layer below the
inversion which, at this point, can be eroded.

Another short wave trough pivots through Sunday afternoon, all
this around evolving broad mid-upper level low pressure over
eastern Canada, again with the mainly afternoon chance for
showers and perhaps a thunderstorm. The mid-level inversion
manifests as just a less steep lapse rate layer, but it and dry
low level air limit CAPE and keep it narrow.

We may manage daytime dry whether at times early next week
depending upon timing of frequent but weak weather systems
moving through.

Central guidance reflects below normal temperatures Friday and
this weekend, before climbing back to and eventually above
normal early next week, as mid-upper level ridging tends to
build amid the weak systems.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
As of 145 PM Tuesday...

Still some areas of MVFR cigs across the region, but most of this
should generally improve to low VFR this afternoon. However, a line
of showers and storms will sweep from west to east across much of
the area generally through 00Z. This will create brief MVFR or IFR
conditions, and brief erratic gusty winds. If storms should
strengthen, severe winds and large hail can also not be ruled out.

Otherwise, a brief lull in the activity is expected after 00Z, but
showers and storms will refire again from north to south after 03-
05Z, with brief MVFR/IFR conditions and strong gusty winds in
vicinity of storms, with widespread MVFR and local IFR conditions in
low ceilings forming again Wednesday morning, before improving to
VFR generally after 15Z. In addition, a period of LLWS is expected
generally 06-11Z Wednesday.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z
WEDNESDAY...

FORECAST CONFIDENCE: Medium.

ALTERNATE SCENARIOS: Timing of convection may vary from
forecast. Timing/development of MVFR/IFR ceilings Wednesday
morning may vary from forecast.

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       18   19   20   21   22   23   00   01   02   03   04   05
EDT 1HRLY       14   15   16   17   18   19   20   21   22   23   00   01
CRW CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H
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    H    H    H
PKB CONSISTENCY  M    H    H    H    H    H    H    H    H    H    H    H
CKB CONSISTENCY  M    H    H    H    H    H    H    H    H    H    H    H

AFTER 18Z WEDNESDAY...
IFR conditions at times in showers and thunderstorms into
Thursday, and in fog and stratus Friday morning.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Flood Watch through Thursday morning for WVZ005>009-013>017-
     024>026.
OH...Flood Watch through Thursday morning for OHZ075-083>087.
KY...Flood Watch through Thursday morning for KYZ101>103-105.
VA...None.

&&

$$

SYNOPSIS...TRM/SL
NEAR TERM...SL
SHORT TERM...TRM
LONG TERM...TRM
AVIATION...SL