Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
1017 am EDT Tuesday may 26 2015
the area will remain in a south to southwest flow of warm and
humid air. An upper level trough slowly lifts through today
through Thursday. Low pressure approaches late in the weekend.
Near term /through tonight/...
sent a quick update to trim probability of precipitation a bit following latest radar
images. Rainfall activity is very limited at this time. However...kept
likely probability of precipitation as expected convection should affect portions of
southeast Ohio...and northeast Kentucky later this afternoon and evening.
Also...tweaked hourly temperatures per latest surface observation.
Previous discussion below...
630 am update...
there remain some question as to how much rain showers associated with
morning middle level wave come together in terms of measurable
rainfall. Kept the small likely probability of precipitation moving northeastward through forecast area
this morning but lowered the chance for the under.
warm moist air on the move keeps the chance for thunderstorms in
the forecast this period. Afternoon instability is limited to a kg per
kg or less this afternoon on account of morning cloud cover and
precipitation...as precipitable water values reside mainly between 1.5 and 1.75
Otherwise weak ripples in the upper level SW flow out ahead of a
short wave trough drifting northeastward from the Central Plains this morning...to
the Midwest Wednesday morning...will drive convection timing. One ripple
was producing an area of showers from the southern Appalachians to eastern
Kentucky early this morning and should move across the forecast area this
The main short wave trough axis then lifts northeastward and is replaced
by another...the larger feature effectively much slower than the
smaller ripples within the flow. The tail end of the original short wave
trough approaches the forecast area from the west late today and then
crosses tonight. Showers and thunderstorms are likely to progress
generally from west to east across the forecast area tonight.
The strong middle level flow associated with this feature coupled
with the late day instability...could lead to strong to damaging
wind gusts in thunderstorms over the middle Ohio Valley late
today...especially if one if far enough north and west to avoid much of
the clouds and showers associated with the disturbance moving
through this morning. Will continue the severe weather potential statement mention in line with
the new swody1.
Locally heavy downpours are also possible...but the storms will be
on the move...limiting any high water to the acute poor drainage
Blended in mosguide for slightly lower highs especially east
today...still at the high end of the guidance envelop. Lows
tonight close to guidance and accepted.
Short term /Wednesday through Thursday night/...
active Summer like pattern continues in the short term period.
Upper ridge will be off the East Coast...with a southwesterly flow
across the area on Wednesday. Will continue to have a warm and
humid air mass in place...and this along with several upper
disturbances moving through the flow...will continue to see
showers and thunderstorms...particularly during daytime heating
hours. Any showers/storms will be capable of heavy downpours in
the humid atmosphere. The area is highlighted in a marginal for
severe weather on Wednesday. The best location for severe looks
to be to the west and north of the County Warning Area...where better
instability...shear...and upper dynamics will exist. Will however
mention the marginal in the severe weather potential statement as an isolated storm going severe
in the unstable conditions cant be completely ruled out.
An upper shortwave and surface cold front will approach the County Warning Area
Wednesday night...before stalling or washing out across the
area. Thus...there appears to be no relief in the short term
period to the heat and humidity. In addition...heights will build
during the day on Thursday behind the departing shortwave...with
maximum temperatures on Thursday a few degrees warmer than Wednesday.
Long term /Friday through Monday/...
followed along with wpc guidance through the long term. Front
crosses late in the period with some cooling and drying north and
west. Still not confident enough to drop probability of precipitation completely out of
the forecast so late in the period...with front being in the
area. Thus...Summer like broad brush of chance probability of precipitation carry through
much of the forecast period.
Aviation /14z Tuesday through Saturday/...
warm and humid air in place...and ripples in the upper level SW
flow...spell rounds of showers and thunderstorms. This keeps
confidence at medium...with uncertainty on the coverage of showers
and embedded thunderstorms forming/moving up from the S early this
morning...plus timing new rounds of convection arriving from the
west-southwest late in the day Tuesday.
Have ceilings mainly atop mixing layer 4-5 kft and prevailing VFR
visibility. A short period of MVFR is still possible as showers move
through this morning...and thunder is possible but not likely.
After a relative afternoon lull...another round of convection is
likely to arrive from the west late today or this evening.
Thunderstorms associated with this convection may produce strong
wind gusts...especially over the middle Ohio Valley. Brief IFR is
possible beneath any thunderstorm late today or tonight.
Surface flow will be light S to SW by day and S to southeast by nt...with
moderate SW flow aloft.
Forecast confidence and alternate scenarios through 18z Tuesday...
Forecast confidence: medium.
Alternate scenarios: timing of convection may differ from
forecast. There may be IFR in showers...thunderstorms and rain
induced fog overnight tonight.
After 00z Wednesday...local IFR in showers/storms...and rain
induced low stratus and fog into Wednesday morning. IFR may linger
in the mountain counties Wednesday afternoon.