Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/15/17
Area Forecast Discussion
National Weather Service Charleston SC
943 PM EDT Sat Oct 14 2017
High pressure will continue north of the area through Sunday. A
cold front will move through the region Monday. High pressure
will build north of Georgia and the Carolinas through mid week
and persist into late week.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
GOES-16 fog channel and 15/01z surface observations show
shallow ground fog beginning to develop across the southern Pee
Dee into portions of Berkeley County and upper Charleston
County. So far, RAP and H3R vsby guidance is doing a decent job
and matches the going forecast pretty well. Updated the
Hazardous Weather Outlook to highlight the potential for dense
fog across inland areas. Lowered overnight lows by several
degrees across parts of the Charleston Tri-County area into
northern Colleton County where temperatures were already
approaching the previously forecasted minima. Temperature falls
should level out in these areas as saturation occurs and
stratus begins to develop. Could see a few upper 50s in the
normally colder areas of the Francis Marion National Forecast.
The remainder of the forecast is on track.
The primary forecast concern for the overnight period centers
on the potential for fog, especially inland. The boundary layer
is poised to decouple shortly after sunset as high pressure
shifts east to the North Carolina coast. Guidance suggests a
weak gradient may linger across far southern areas to keep the
boundary layer coupled there through at least midnight, but
expect all areas to go either calm or calm for much of the early
morning hours Sunday.
Low-level moisture will pool beneath the noctural inversion
with boundary layer saturation expected. With skies remaining
clearing until late, expect areas of fog to develop away from
the coast. NAM12 soundings suggest there may be just enough flow
atop the boundary layer to support more in the way of stratus
versus fog, but the RAP soundings suggest a slightly weaker flow
will prevail thus favoring more in the way of fog. Suspect the
ultimate outcome will fall in between the two with a mixture of
fog and stratus encompassing much of the interior by daybreak
Sunday. Will continue to highlight areas of fog inland with
patchy fog at the coast. The best chances for dense fog look to
setup across interior Southeast South Carolina from roughly
Walterboro to Moncks Corner which is where the lowest 1000 hPa
condensation pressure deficits are progged to occur.
Lows will range from the lower 60s well inland to the lower 70s
along the Georgia coast where onshore winds will help moderate
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Sunday: The expansive upper ridge will begin to narrow but another
day of dry and warm weather is on tap across the forecast area. The
synoptic flow will gradually trend from the broad wedge pattern from
Saturday to a transitional/variable setup on Sunday. Pockets of
stratus and fog are expected to dissipate by late morning leading to
another unseasonably warm mid October afternoon across the area.
Diurnal cumulus fields will probably be a bit more prevalent in
southeast GA given the weak onshore component atop the boundary
layer. High temps are expected to reach the mid 80s most areas
inland from the beaches and barrier islands with some upper 80s not
out of the question in a few spots that may see near-full sunshine.
A progressive shortwave will push a cold front through the area on
Monday. Moisture will briefly surge ahead of the front with PWATs
above 1.75" on Monday. The latest model progs suggest convective
rains will shift east and southeast along and just ahead of the cold
front with likelihoods for showers and a few thunderstorms by late
morning across the northern and inland zones and across the
remainder of the forecast area during the afternoon hours. Rainfall
amounts will generally average 1/4" or so, perhaps some heavier
bands of 1/2" to 1" rains may occur. The arrival of the front will
induce some strong thermal gradients across the region with temps
falling through the 60s northwest zones by the afternoon while
readings in the lower 80s will linger southeast zones until
convective rains arrive mid to late day.
Cooler and much drier air will spread into the area Monday night
into Tuesday. Tuesday morning lows will be in the 50s and the highs
will top out in the mid 70s. High pressure will prevail on Wednesday
with highs again in the mid 70s with persistent northeast
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A large surface high will remain to the northwest during the
extended period, maintaining dry conditions and slowly
moderating temperatures. A few showers will be possible over the
coastal waters and immediate coast as a weak coastal trough
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
* Fog and low-stratus yielding IFR or lower conditions
Conditions look favorable for low stratus and fog to develop
across the region early Sunday as high pressure holds firm. The
best fog/stratus probabilities look to occur just inland from
the terminals, but guidance is similar in showing KCHS
positioned right along the eastern fringe of the lowest
conditions. Will show prevailing MVFR in ground fog beginning
around 09z with a TEMPO group from 10-12z highlighting vsbys
just below alternate minimum thresholds. Opted to keep skies
VFR with a scattered deck 200-400 ft. It is very possible that
low cigs could become established and could approach airfield
minimums, but confidence in this is not high enough to mention
right now. For KSAV, looks like the best stratus/fog potential
will remain west, so will only show high- end MVFR vsbys at this
time with no cigs. Low cigs/vsbys should return to VFR by mid-
morning and prevail through the remainder of the 00z TAF
Extended Aviation Outlook: Areas of fog/stratus are possible Monday
morning, resulting in MVFR/IFR visibilities and/or ceilings. Brief
flight restrictions possible Monday afternoon in convective and post-
Tonight: No highlights. A ridge of high pressure will be centered
just north of the waters. East-Northeast winds of generally 5
to 10 knots with seas 2 to 4 feet.
Quiet conditions will persist Sunday into Monday morning before a
strong cold front sweeps through Monday afternoon and evening. A
strengthening northeast flow behind the cold front will likely
result in a prolonged period of Small Craft Advisory conditions from
Tuesday through much of next week. Strong moisture and thermal
gradients will develop several hours around daybreak on Tuesday
morning and pinching gradients may result in at least occasional
gale force wind gusts off the GA coast beyond 20 NM. Seas will build
to 4-6 ft with 7-9 ft seas likely beyond 20 nm off the coast Tuesday
into mid-week. Seas may reach 10-11 ft out close to the Gulf Stream
Minor coastal flooding will be possible around the times of high
tide beginning Tuesday morning. Coastal Flood Advisories could
eventually be needed, especially along the South Carolina coast.
Record Highs for October 15th:
KCHS: 87 set in 1985.
KCXM: 88 set in 1925.
KSAV: 90 set in 1925.
Area Forecast Discussion
National Weather Service San Angelo TX
912 PM CDT Sat Oct 14 2017
Cold front moved through Amarillo around 9 PM, with gusts over 40
mph at times behind it in the Panhandle. HRRR short range model
appear to be on track, moving the front through Sweetwater and
Abilene between 2 and 3 AM...San Angelo and Brownwood just after 4
AM...and the I-10 corridor between 6 and 7 AM. North winds of 25
to 30 mph with higher gusts indicated after frontal passage
support the wind advisory from 1 AM to 7 AM for the Big Country
and Concho Valley.
.PREV DISCUSSION... /issued 655 PM CDT Sat Oct 14 2017/
A strong cold front will move across the terminals from north
to south overnight, bringing gusty north winds and some scattered
convection along and behind the front through the morning hours.
Frontal passage is expected at the northern terminals between 07Z
and 08Z and across the southern terminals between 10Z and 11Z.
North winds will gust to around 30 knots behind the front through
early afternoon, with winds slowly subsiding towards the end of
the forecast period. Expect some MVFR ceilings behind the front
Sunday morning, with VFR conditions returning by Sunday afternoon.
PREV DISCUSSION... /issued 330 PM CDT Sat Oct 14 2017/
(Tonight and Sunday)
Expect colder temperatures, windy conditions and a chance of rain
late tonight through Sunday. A strong cold front will move south
across West Central Texas, arriving at the I-20 corridor around 07Z
and south of the I-10 corridor by 13Z. Strong north winds will occur
behind the front with gusts to around 40 mph across the Big Country
and Concho Valley, and a Wind Advisory is in effect for these areas
from 1 AM to 7 AM Sunday. The winds should remain below advisory
criteria across the remainder of the area, but will be quite gusty
at times. Still will be windy through mid morning Sunday, and
then speeds decrease during the rest of the day. Temperatures will
be much cooler Sunday(at least 20 degrees) due to low level cold
air advection. For precipitation, the Hi Res models are indicating
a line of showers and thunderstorms will form along and just
behind the front across much of the the area late tonight through
Sunday morning. The best chance of storms will be across the
northern half of the area due to better upper support and some
elevated instability. The storms will produce dangerous lightning
and strong wind gusts. The Highest Pops(Cat to Lkly) across the
northern half of the area for late tonight. Most of the
precipitation should end by 18Z Sunday.
(Sunday Night through Saturday)
The of surface high pressure, a dry air airmass and mostly clear
skies will bring cool temperatures to the area Sunday night
through Tuesday. Lows will be mainly in the 40s Monday and Tuesday
mornings, with a few upper 30s possible especially in low lying
areas and river valleys. Highs will be in the 70s. A warming trend
will take place mid to late this week across the area as low
level southerly flow returns. Highs will be in the lower to mid
80s, with lows in the 50s, lower 60s by Friday and Saturday. Also,
going with a mainly dry forecast.
.PRELIMINARY POINT TEMPS/POPS...
Abilene 54 67 43 70 / 80 20 0 0
San Angelo 56 68 43 73 / 60 30 5 0
Junction 61 71 45 73 / 30 40 5 0
Brownwood 57 68 44 72 / 70 30 0 0
Sweetwater 52 67 45 69 / 70 20 0 0
Ozona 57 66 44 72 / 40 30 5 0
Wind Advisory from 1 AM to 7 AM CDT Sunday for Callahan-Coke-
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Sunday)
Issued at 258 PM CDT Sat Oct 14 2017
19Z water vapor imagery shows an upper trough over the central
Rockies moving towards the NEB panhandle. At the surface, a trough
axis extends from near SLN to MYZ and a cold front was located from
HLC to HSI. Objective analysis from the RAP and LAPS shows some
surface based instability of 1500 to 2000 J/kg has developed across
east central KS, generally southeast of an EMP to TOP line.
All the guidance shows thunderstorm coverage increasing along the
front as it surges southeast through the area. Unidirectional wind
shear and strong winds aloft continue to support the potential for
damaging winds with the thunderstorms later this afternoon and this
evening. So will need to keep an eye on severe potential. Current
convection over east central KS could have a big impact on where the
stronger storms develop. Based on some of the convective allowing
models, the window for strong or severe storms looks to be from
around 5 pm through about 9 pm. Precip will come to an end shortly
after the frontal passage as much dryer and cooler air advects
southeast. Winds are also going to strengthen behind the front with
gusts up to 35 MPH possible across north central KS this evening.
Thought about a possible wind advisory, but RAP and NAM progs of the
pressure gradient force suggest the stronger winds should not last
but for a few hours. And most objective guidance shows most areas
remaining below criteria. So will not issue a wind advisory at this
time and monitor conditions as the front moves through.
Lows are expected to be in the lower to mid 40s. Continued cold air
advection through Sunday is expected to keep highs in the lower 60s
on Sunday. Although full insolation and relaxing winds will make it
feel a little better.
.LONG TERM...(Sunday night through Saturday)
Issued at 258 PM CDT Sat Oct 14 2017
Surface high pressure over the Central Plains on Sunday night moves
off to the southeast on Monday and remains over the southeast into
the southern Plains keeping the gulf moisture off shore. Northwest
mid level flow aloft on Monday then continues across the central
Plains into mid week then transitions to southwest flow by then end
of the week. Models move an upper trough off the eastern Pacific and
into the Rockies on Saturday. There are some model differences with
the timing and the strength of the trough next weekend so confidence
is not high with precipitation chances. With return flow from mid
week onward low level moisture will increase through the end of the
week with dew points increasing into the mid 50s by Saturday. High
temperatures for the week start out around normal on Monday with
highs in the lower 70s on Monday warming up into the mid 70s for
much of the week and into the upper 70s on Friday. Lows will start
out Monday morning in the upper 30s, then in the 40s through Thursday
morning with lows in the 50s for Friday and Saturday morning. Will
monitor potential for Monday morning for some patchy frost in
sheltered areas possible if temperatures are able to cool a few more
degrees under good radiational cooling conditions.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 641 PM CDT Sat Oct 14 2017
FROPA past KMHK while boundary is hovering near KTOP/KFOE with
westerly winds increasing and veering to the northwest. Kept a
mention of VCTS at KTOP/KFOE given the proximity of the front
through 02Z and the current convection to our south and
southwest. Post frontal MVFR stratus builds in behind the boundary
as strong northwest winds gust in excess of 25 kts through 09Z.
Dry air advection is progged to erode stratus quickly before 12Z
with VFR prevailing for the remainder of the period.