Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
220 am EDT Thursday Aug 21 2014
abundant humidity remains in place. A warm front remains near
stationary overnight through Thursday. Shortwave passes Thursday.
The warm front crosses Thursday night into Friday.
Near term /through today/...
200 am update...
looks like a dry remainder of the nt...with next convective complex
riding along warm front not arriving until near dawn.
updated forecast to include slight chance probability of precipitation across Harrison and
Taylor counties for an isolated shower. Decreased probability of precipitation over rest
of County Warning Area as showers are exiting. Also increased coverage of patchy
fog across the County Warning Area with clearing...before clouds increase again by
morning. Slowed the timing of probability of precipitation for tomorrow morning as well.
Temperatures OK. No other changes are expected.
challenging forecast tonight through Thursday...starting little or
no precipitation through at least 05z. An mesoscale convective system crossing southern in at
18z...is expected to continue its trajectory southeast through
tonight. More often than not...this system diminish in intensity
and die before it reaches southeast Ohio...northeast Kentucky and portions
of WV overnight. Nevertheless...due to the uncertainty...introduce
small probability of precipitation from west to east around 06z...spreading east towards
12z Thursday morning. Low level stratus is also a possibility due
to high dewpoints in the upper 60s.
Areas of fog will be common over areas that received rain...and
along river valleys which skies clear overnight. Clouds will
increase and thicken overnight with the upcoming dying mesoscale convective system.
A warm front dissects our County Warning Area from north to south at this time and
will meander over the area tonight. Models have under played
nocturnal convection from previous runs. Only expect convection
associated with dying mesoscale convective system spreading from west to east during the
Increase probability of precipitation to likely on Thursday as the NAM and CMC models
suggest another 500 mb vortmax but stronger wave on during the
Went with a blend of bias corrected sref and all blend consensus MOS
for temperatures through the period.
Short term /tonight through Saturday/...
will be tracking several upper air disturbances in the northwest flow in
combination with a developing warm front to produce unsettled weather.
There will be a decent low level jet feeding into the aforementioned warm
front on the order of 35 kts Thursday night...with increasing
precipitable waters to just over 2 inches. As such...potential for heavy rain is
definitely there with some training/back-building possible Thursday
night into Friday morning. Having said that...the location of
where this sets up is in question. Models have shifted this axis
into northern zones from their previous location across east Kentucky/S WV
24 hours ago. After coordinating with some of the surrounding
offices...have held off on issuance of Flash Flood Watch with the
hope that the 00z runs can offer some continuity from the 12z runs
today regarding where the area of concern sets up. 1 to 3 inches
of rain is possible within this axis Thursday night into Friday.
NAM appears to develop potential a mesoscale convective vortex on Friday for a
continuation of the heavy rain threat. This would drive the boundary
south through the area as the day progresses but not totally buying
into a mesoscale convective vortex at this time. Will try to show a drying trend Friday night into
Saturday with moisture axis shifting to SW briefly.
Long term /Saturday night through Wednesday/...
will slowly transition to a drier regime as the upper heights
slowly build over the area courtesy of the Stout Ridge amplifying
over MS valley. The oppressive heat should stay west of the area but
will still be contending with the muggies with temperatures running 3 to
5 degrees above normal day and night.
Aviation /06z Thursday through Monday/...
some dense valley fog overnight into Thursday morning...but patchy IFR
and MVFR cloud will raise/keep visibility MVFR or better at times. Altocu
will also have mitigating affect on fog...especially southern taf
sites. As a result...have hit the dense fog hardest in the code for
the northern sites.
Clusters of showers and thunderstorms will ride east to southeastward along a
warm front set up across the lower Ohio Valley this taf period. One
cluster will cross during the day Thursday. Since the daytime hours are
not a favorable time for convection associated with warm front...it
is difficult to determine how much area coverage there will be...but
there should be a decrease in coverage Thursday nt. The next complex
should arrive Friday morning...beyond the current 24 hour taf period.
Post rain low cloud and fog may form in the interim.
Surface flow will be light and variable...mainly west...while light to
moderate west flow aloft becomes northwest Thursday.
Forecast confidence and alternate scenarios through 06z Friday...
Forecast confidence: low to medium.
Alternate scenarios: timing and intensity of fog will vary in
response to changing ceilings including MVFR to IFR ceilings. IFR is
possible but difficult to time in showers and thunderstorms Thursday.
Areas of Post rain fog and low cloud may form Thursday nt.
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 08/21/14
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 M M M h l l l l M h l M
heights consistency h h M M M h h M M M M M
bkw consistency h h M M M h h M M M M M
ekn consistency l l l l l l l l l h h h
pkb consistency l l l l l l l l M h h h
ckb consistency l l l l l l l M h M M M
After 06z Friday...
IFR conditions possible in any round of convection Friday through Friday
nt. Late night and early morning Post rain fog and stratus also
possible early Friday morning and Sat morning.