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fxus61 krlx 200709 
afdrlx

Area forecast discussion
National Weather Service Charleston WV
309 am EDT Thu Jun 20 2019

Synopsis...
one upper disturbance crosses overnight. Another, along with a
surface cold front, crosses Thursday. Warm front moves through
early this weekend. Cold front early next week.

&&

Near term /through tonight/...
as of 215 am Thursday...

Adjusted overnight pops with one last band of mainly just
showers crossing overnight, and probably breaking up. The strong
thunderstorm and heavy rainfall threat seems to have waned for
the overnight.

As of 810 PM Wednesday...

The forecast remains on track, however made some minor
adjustments to match current observations and trends as well as
gave quantitative precipitation forecast a fresher look with the help of updated model
guidance.

As of 600 PM Wednesday...

The forecast still remains on track as things currently calm
down a bit, however some convection is still on The Table for
this evening into the overnight. No significant changes were
needed to the forcast at this time and with all the heavy
downpours and rain accumulations that have been observed for the
day, the Flash Flood Watch still remains in effect until
Thursday evening.

As of 200 PM Wednesday...

We are still stuck in the same pattern we have been for most of
the week, with southerly flow pumping moisture into the forecast
area, and ripples in the 500mb flow driving areas of showers and
storms. We did get some sunshine this afternoon, so have a bit
more cellular convection ongoing due to 500-1000 j/kg MLCAPE
added by the solar heating. With limited shear, not expecting
much organization to the storms, but any taller cells could be
capable of marginally severe wind gusts, which is reflected by
the Storm Prediction Center day 1 outlook.

Overnight, expect showers and storms to lessen in coverage
initially, but as another 500mb shortwave trough crosses think
coverage will pick up again and have gone with an area of likely
pops crossing from west to east after midnight.

A surface low will cross Northern Ohio on Thursday, with a cold
front crossing the forecast area. This, combined with 500mb
ripples working through the mean trough and lingering outflow
boundaries from earlier activity will lead to showers and
thunderstorms on Thursday. Tried to put some timing info for the
best chance of storms using the wrfnmm... but really a
shower/storm could be around any time with abundant moisture and
multiple modes of synoptic and mesoscale forcing moving
through. The NAM is not really impressed with instability for
Thursday, while the rap shows up to 2000 j/kg of MLCAPE.
Instability will be highly dependent on how much sun we get
during the late morning and early afternoon. Right now, think we
will have pretty widespread cloud cover, limiting the strength
of storms, but confidence is not great. We will see better bulk
shear moving through during the day, so if we do get some
sunshine, the rap could be on to something, with stronger storms
possible during the afternoon with strong winds the main concern.
Storm Prediction Center marginal risk across the eastern half of the forecast area
also reflects this possibility, with the better chance of
severe weather to the east where instability should be better.

Flash Flood Watch remains in effect into Thursday evening.
Precipitable water values will remain in the 1.5-2 inch range
along and ahead of the cold front, so any stronger shower or
storm could produce heavy rainfall and localized flooding.

&&

Short term /Friday through Sunday/...
as of 305 am Thursday...

A warm front Marks the return of higher humidity through the
column after a brief stint in a low pop forecast. Looking at
the thicknesses and layer moisture, the warm front will make
only slow progress through the County Warning Area Friday through Saturday. The
upper level flow will be nearly parallel to this warm front, so
there will be a possibility of convection running southeastward
along the boundary Friday night and Saturday night. Even though
the warm front should make a full push through the region, the
northwest flow aloft looks somewhat active for the duration of
the short term after Friday, particularly for the western County Warning Area.
The rises in the 500mb heights will signal a modest warm up that
will be affected by clouds and convection, but temperatures
should end up slightly above normal for the Max values this
weekend. The Standard threats for downpours and some gusty
winds in storms will be present.

&&

Long term /Sunday night through Wednesday/...
as of 305 am Thursday...

The upper level pattern becomes progressive again, with the
ridge passing early next week and the next trough axis in line
behind it. Expect frontal passage right now in the late Monday
night/Tuesday time frame, and will of course need to watch the
convective threats for as it does so. Some discrepancies in the
long term models give a lower confidence for this timing.

&&

Aviation /07z Thursday through Monday/...
as of 215 am Thursday...

MVFR conditions will occur in showers, with some thunderstorms,
overnight. A small band will move through ckb 06z to 08z. A
longer band, cutting through heights at 06z, MA also affect the
other five taf sites overnight, although there may be a
tendency for this band to weaken or even dissipate. Outside
these bands, expect mainly VFR conditions.

A cold front will cross the area Thursday afternoon. Strong
thunderstorms may impact the area ahead of the front later
Thursday morning into early Thursday afternoon, but confidence
in timing and placement was too low to include explicitly in
the tafs at this time, other than the cumulonimbus / thunderstorms in the vicinity mention. However,
any thunderstorm Thursday can bring brief IFR conditions, along
with strong wind gusts.

An MVFR cloud deck will set in behind the front Thursday night,
with MVFR visibility in showers in and near the mountains,
where ceilings may eventually go IFR overnight Thursday night.

Light southwest surface flow overnight will increase to 10 to
15 kts Thursday, with gusts of around 25 kts. Surface flow will
become west to northwest behind the front Thursday night, and
remain gusty initially, before gradually diminishing overnight
Thursday night. Moderate southwest flow aloft overnight and
Thursday will become moderate northwest Thursday night.

Forecast confidence and alternate scenarios through 06z Friday...

Forecast confidence: medium.

Alternate scenarios: timing of restrictions may vary, and
amendments may be needed for showers and thunderstorms. Gusty
winds will vary Thursday. Timing of lowering ceilings Thursday
night may vary.

Experimental table of flight category objectively shows consistency
of weather forecast office 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 Thursday 06/20/19
UTC 1hrly 06 07 08 09 10 11 12 13 14 15 16 17
EDT 1hrly 02 03 04 05 06 07 08 09 10 11 12 13
crw consistency h h h h h h M h h M h h
heights consistency h h h h h h h h h h h M
bkw consistency h h h h h h h h h h h h
ekn consistency h h h l l M h h h h h h
pkb consistency h h h l h h h h h h h h
ckb consistency h h h h h h h h h h h h

After 06z Friday...
IFR in fog/stratus possible overnight Thursday night into
Friday, especially in and near the mountains. Brief IFR possible
in showers and storms this weekend.

&&

Rlx watches/warnings/advisories...
WV...Flash Flood Watch through this evening for wvz005>011-013>020-
024>034-039-040-515-516.
Ohio...Flash Flood Watch through this evening for ohz066-067-075-076-
083>087.
Kentucky...Flash Flood Watch through this evening for kyz101>103-105.
Virginia...Flash Flood Watch through this evening for vaz003-004.

&&

$$

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