Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
848 PM EDT Friday Jul 3 2015
low pressure moves through area tonight...then to our east on
Independence day. Drier air tries to ooze southeast Saturday
afternoon. Middle level disturbance eastern slopes Sunday-Monday.
Near term /through Saturday/...
815 PM update...extended higher probability of precipitation through early tonight to
mainly follow the slow moving frontal system. Front at 8 PM
basically along the Ohio River...so best probability of precipitation are to the east.
Front reaches mountains by 10z...but convection will be diurnally
decreasing by 06z.
baggy surface low slowly moving through Kentucky this afternoon. Convection has
fired ahead of decaying mesoscale convective vortex crossing SW Virginia. This broken line of
convection extends northwest into southeast Ohio as of 18z. Some good dumpers over
Kanawha valley the next few hours...with areas further north getting in
on the action late afternoon/early evening. Once the low tracks along Ohio
River this evening...expect bulk of the activity to depart with
it...leaving much less coverage of rain showers/thunderstorms and rain over the area.
Still...with the upper trough yet to cross and the surface boundary
lingering...was hesitant on letting east extent of the watch go at
00z. After collaboration with neighbors...extended to 12z while
letting west portion of the watch expire on time. It is entirely
possibly even the East Part of the watch can be let go before 12z.
Think low stratus will settle in overnight with patchy areas of
dense fog in this moist low flow environment. Drier air will be
advecting into southeast Ohio near dawn...but will be stubborn to make much
further southeast progress until midday. As such...held the low clouds east
of the Ohio River for much of the day...especially over the
mountains...closer to the old boundary.
Short term /Saturday night through Sunday night/...
a cold front move south and stalls along the WV/Kentucky border by 00z
Sunday. The NAM/ECMWF/GFS/CMC models bring drier air at all levels
suggesting clearing skies spreading from northwest to central WV
Saturday night. Models also show boundary layer winds about 5 knots
for the same time period. Therefore...expect mostly clear skies
Saturday night except for some low stratus developing around pkb
south and east to crw and ckb after midnight...and fog developing
along river valleys during the predawn hours Sunday morning. Kept
clouds and low chance probability of precipitation along the eastern mountains as low level
moisture can get trapped over the western slopes and extreme
southern sections where will be closer to an old frontal boundary south
of the area. Any precipitation should be out of the area by 12z Sunday.
However...the frontal boundary meanders south of the area Sunday
while a short wave at h500 moves from the southwest. This wave
will bring chance probability of precipitation back north across southern WV and eastern
mountains through Sunday evening. Additional middle level
disturbances will keep low chances for precipitation further north through
Monday mainly during the afternoon hours.
Went with a blend of NAM and sref for temperatures through the
period. Generally...highs in the low to middle 80s lowlands ranging
into the middle 70s higher elevations. Lows will will be in the middle
to low 60s...except int he upper 50s over the northeast mountains
and portions of southeast Ohio.
Long term /Monday through Friday/...
a frontal boundary meanders south of the area Monday keeping low
chance probability of precipitation as weak middle level disturbances passing by. Any precipitation
would be more during the afternoon hours with the maximum heating.
A rumble of thunder can not be ruled out each afternoon through
Tuesday. Models show very dry air aloft which should help to suppress
showers and storms to become strong.
A cold front approaches from the northwest Wednesday...crossing
Wednesday night into early Thursday. Coded high chance probability of precipitation with
this feature mainly across the southern third of the area for
now. Another weak high pressure should develop behind the front
Thursday into the end of the period.
Went with wpc guidance for temperatures through the period.
Aviation /01z Saturday through Wednesday/...
00z Saturday through 00z Sunday...
slow southeastward moving frontal system at 00z basically along
the Ohio River. Very moist and unstable atmosphere will continue
chances for showers and a few storms mostly along and ahead of
the front...through these will weaken overnight with loss of
heating. By 12z...best chance for showers will be in southeast
With the more widespread showers earlier...the very moist air and
wet ground...expect a general lowering of flight category to
IFR/LIFR by 06z at the major terminals. Conditions slowly improve
after 13z from northwest to southeast to MVFR and finally to VFR
ceilings. Look for VFR to occur by 18z in the west and by 22z in
Forecast confidence and alternate scenarios through 18z
Forecast confidence: low.
Alternate scenarios: timing and extent of downpours and storm
early tonight may vary. Spatial extent and timing of fog and
stratus in question tonight...in addition to improvement Saturday.
After 18z Saturday...IFR expected in valley Fog/Mountain clouds
Saturday night into Sunday morning...mainly in WV. IFR possible in
showers and/or low ceilings along eastern slopes Sunday night.
WV...Flash Flood Watch until 8 am EDT Saturday for wvz015-016-
Virginia...Flash Flood Watch until 8 am EDT Saturday for vaz003-004.