Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/12/17
Area Forecast Discussion
National Weather Service Goodland KS
830 PM MST Sat Nov 11 2017
Issued at 830 PM MST Sat Nov 11 2017
Difficult forecast regarding coverage and extent of clouds, fog,
freezing fog, visibilities and temperatures.
At 0330z low clouds extend from near McCook to Colby to north of
Tribune with a clear sky to the west. Areas in the clear are below
freezing and starting to get dense freezing fog.
Right now trended temperature/dewpoint forecast to the RUC which
has a pretty good handle on things and for visibility the rap13
and gfslampgrid visibility forecasts. Basically dense fog/freezing
fog is expected to expand east/northeast tonight then dissipate a
bit across the west toward morning. Models are showing another
batch of low visibilities moving south into the area during the
mid to late morning hours which may have to be dealt with with
some type of advisory.
Anyway, dense fog advisory is published and out.
.SHORT TERM...(This evening through Sunday)
Issued at 232 PM MST Sat Nov 11 2017
Forecast problem will continue to be the stubborn saturated low
level air mass that remains across the area. As has been the case
the last week, models have had trouble in resolving the low level
thermal and moisture fields. Weak surface low with its associated
boundary was located to our southeast. This kept weak north to
northeast winds across the forecast area today. This setup kept
the saturated low level air mass over the area. Clearing line to
the west has been creeping slowly east due to lack of a strong
At this time it looks like the clearing line barely makes it to
the east of the Colorado border. Then the moisture moves back to
the west once again. High resolution guidance is consistent in
redeveloping stratus and fog but disagrees on how far west to put the
next round of fog. At this time am thinking the Nam may be a
little too far east with the Hrrr a little better.
The general consensus is to develop fog along and east of the
Colorado border and move it slowly east through tomorrow morning
before dissipating it. Some dense fog looks possible again but
models disagree on where. So will not issue an advisory and will
let the evening shift take another look at it. Forecast soundings
and high resolution guidance would support some patchy drizzle in
the eastern third and inserted that into the forecast.
The stratus looks like it may last into the afternoon which will
wreak havoc on the temperature forecast and probably make for a
wide range of high temperatures. All in all the temperatures look
near to slightly cooler than todays maxes.
.LONG TERM...(Sunday night through Saturday)
Issued at 1249 PM MST Sat Nov 11 2017
The extended period (Mon-Sat) looks dry even though a couple cold
fronts drop through the area. Sunday night through Tuesday a
broad ridge will prevail aloft with southerly flow at the surface
resulting in milder temperatures Mon-Tue and max temps 10-15
degrees above normal. A cold front will drop rapidly through the
area Tuesday night, associated with a weak short wave aloft moving
east across the northern Plains. Timing among the various models
is fairly consistent. No precip is expected but max temps
Wednesday will return to normal in the 50s.
The next system to affect the Central Plains will occur Thu
night-Friday. There is a timing difference with GFS guidance
bringing the front through Thu evening while the EC is about 12
hours slower. Either way, temps Friday will be about 10 degrees
colder. Given the speed of the system, location of better forcing
to the north and better moisture displaced southeast of the area,
the chance of any significant precipitation with the late week
system looks slim.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 400 PM MST Sat Nov 11 2017
Forecast issues for both terminals will be timing and extent of
low clouds/br/fg and associated visibilities as low level moisture
remains across the area.
For KGLD, currently expecting sub ifr conditions to continue
through about 08z with visibilities possibly lowering to 1/4sm
creating lifr/vlifr conditions. Should see conditions improve to
vfr after 09z as northwest winds under 10kts move in and push the
low clouds to the east. NAM model continues with high amounts of
low level moisture and should it verify keep ifr cigs at the
terminal for the entire taf period.
For KMCK, currently expecting mvfr/ifr conditions to continue
through maybe 16z before moving east of the terminal allowing vfr
conditions to return from 17z-00z.
Adjustments and updates will likely be needed through the evening.
KS...Dense Fog Advisory until 8 AM MST /9 AM CST/ Sunday for
CO...Dense Fog Advisory until 8 AM MST Sunday for COZ090>092.
NE...Dense Fog Advisory until 8 AM MST /9 AM CST/ Sunday for NEZ079-
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
906 PM CST Sat Nov 11 2017
Issued at 905 PM CST Sat Nov 11 2017
Radar mosaic shows a broad N-S swath of light pcpn across western
MO and is starting to edge into central MO currently. Out ahead
of this, a batch of heavier pcpn has developed around the UIN-HAE
area. Examination of RAP vertical temp profiles and the high
potential for evaporational cooling and seeing some higher pockets
of reflectivity on radar, there does appear to be a small window
of opportunity for sleet to mix in with the rain. It should not be
persistent enough to dominate to where a mention is necessary and
with relatively warm ground, it should not be a factor on
impacts. Temps ranged from the upper 30s in parts of southern IL
to lower 50s in central MO. A rather substantial 15-20F dewpoint
depression exists. Satellite has cloudy skies areawide.
For the most part the previous forecast is on target and made few
changes, with pcpn chances, light as they will be wrt QPF,
ramping up to at least likely for a 2-3 hour window later tonight.
Much of the pcpn that falls will be light rain, but moisture will
become more shallow with time and by daybreak Sunday and into much
of Sunday morning, enough shallow moisture with weak convergence
from a cold front moving thru will justify a switchover to drizzle
for a short time before pcpn ends.
Persistent clouds thru the day on Sunday nearly everywhere and a
cold FROPA will limit any temp rises and should keep most areas in
.SHORT TERM... (Through Late Sunday Afternoon)
Issued at 250 PM CST Sat Nov 11 2017
Thick cirrus will quickly give way to lower clouds this evening in
response to broad warm advection ahead of an approaching shortwave
from the Plains. Rain is expected to develop this evening in central
Missouri where low level moisture convergence is maximized and then
spread/expand east toward the Mississippi River by midnight and into
Illinois through daybreak on Sunday. DPVA from the approaching
shortwave will also aid in synoptic lift across the area. While we
are not expecting a signficant amount of precipitation with this
system, measurable precipitation will be widespread enough to
warrant likely and categorical PoPs tonight. Thickening cloud cover
and a southerly wind will keep temperatures from falling too much
tonight and have given the nod to a blend of short term model
guidance for minimum temperatures Sunday morning.
Surface low and cold front, associated with the shortwave, will move
across the CWA on Sunday. Have maintained a slower solution, with
best chances of rain along and east of the Mississippi River. Light
wind, due to the proximity of the surface low, will become northwest
during the afternoon in the wake of the surface cold front. Did
shave a few degrees off high temperatures for Sunday given thick
cloud cover and lingering precipitation.
.LONG TERM... (Sunday Night through Next Saturday)
Issued at 250 PM CST Sat Nov 11 2017
Active pattern this week as two upper level trofs will impact the
region. The first trof will move into the Upper Plains Tuesday.
Associated cold front will drop into the CWA early Wednesday. Ahead
of the front decent moisture transport from LLJ and WAA should allow
for some widespread showers. Cannot rule out an embedded
thunderstorm with the system.
The second system moves into the area Thursday night into Friday. As
a surface low moves into southern MO a warm front is draped across
the CWA before low moves east into IL and pushes associated cold
front through the CWA. Models lack agreement with the onset of
precip with this system. GFS is more agressive with precip
associated with the warm front and the ECMWF keeps the period dry
until the cold frontal passage Friday morning. Both models agree
with pre frontal precip but are not consistent with timing, The
ECMWF seems to lag behind GFS by 12 hours.
Temps for the period will be close to seasonal normals with some
slightly above normal temps Wednesday through Friday.
.AVIATION... (For the 00z TAFs through 00z Sunday Evening)
Issued at 548 PM CST Sat Nov 11 2017
CIGs will lower overnight into at least low-end MVFR category at
all TAF sites as an area of light rain overspreads the area. There
will be a higher likelihood of IFR at COU and especially UIN and
have included in those forecasts. The rain may become drizzle
towards the end of the event heading into Sunday morning, and if
realized, will contribute to VSBY reductions into IFR, but short
of that, VSBYs should stay MVFR or better. A cold front will drop
thru Sunday morning taking light/variable winds and becoming NW
but speeds should remain less than 10kts. A region of low clouds
should hold together, especially around UIN, into Sunday afternoon
with this core region then dropping southeastward in the wake of
the front. With that in mind, could see low CIGs continue at STL
metro sites well into Sunday night, but should clear out of UIN
and COU shortly after nightfall Sunday evening.
SPECIFICS FOR KSTL: Deterioration of CIGs into MVFR by late
tonight but rain onset should occur around midnight. Rain
intensities should be light and may end as drizzle after sunrise
Sunday. Low-end MVFR should continue thru Sunday and into Sunday
night with the potential of IFR late Sunday afternoon and evening
depending on how it evolves, but this time period will be more
favorable for IFR to occur. Some clearing may occur by late Sunday
Area Forecast Discussion
National Weather Service Shreveport LA
958 PM CST Sat Nov 11 2017
The extensive cu field associated with an axis of H850 moisture has
now spread E to encompass the remainder of Ncntrl LA this evening,
with cigs beginning to lower a bit over Ecntrl TX as theta-e ridging
has developed along a 30-35kt Swrly LLJ axis. Meanwhile, the evening
water vapor imagery depicts a flat shortwave trough currently
traversing the Cntrl Plains, which will shift E into the Midwest/Upper
MS Valley by 12Z Sunday. This shortwave will help nudge a weak sfc
front (now extending from NW OK into Cntrl KS) SE late tonight and into
the region by late Sunday morning. Ahead of the front, H850 theta-e
ridging will shift farther ENE into NE TX/SE OK/SW AR overnight, which
should help enhance some weak isentropic lift along the 295-300K
surfaces over these areas along and S of the attendant W-E H850
trough. The 00Z NAM is in good agreement with the latest HRRR runs
suggesting that isolated -SHRA may develop along/N of the I-30
corridor after 06Z, which seems plausible as weak forcing aloft
associated with the H700 trough increases late as well over these
areas. Thus, have expanded slight chance pops a little farther S
across E TX and E across SW AR, but rainfall amounts (if any) should
be quite light.
The thickening and expansive cu field will also limit the temp fall
overnight, with temps expected to remain fairly steady through
daybreak across most areas, the exception being the Ern zones where
readings may fall another few more degrees. Have raised min temps
across the Wrn half of the area to the mid/upper 50s, with only
minimal warming expected Sunday as the sfc front slides S through the
area during the afternoon and the expansive cloud shield limits
insolation. -SHRA may increase a bit Sunday over portions of NE TX/NW
LA, but will leave slight chance pops as is (and defer to the mid
shift) as isentropic forcing weakens during the afternoon ahead of the
H850 trough with QPF amounts again quite light.
Zone update already out...grids will be available shortly.
.PREV DISCUSSION... /issued 610 PM CST Sat Nov 11 2017/
For the ArkLaTex, low to mid VFR cigs to continue with some MVFR
for TXK where most rain may occur. VCSH will likely keep decent
vsby elsewhere by around daybreak as a weak frontal boundary sinks
into the area shift winds from S to NE less than 10 KTS by mid to
late day. Climb winds attm are light SE then become W 25KTS by
5kft with moisture thick from 5-10kft. FZL is 12kft and air dries
significantly so no threat for ice. FL winds keep W 15-35KTS.
Rain ends by late on Sunday with dry wx until midweek expected.
.PRELIMINARY POINT TEMPS/POPS...
SHV 55 68 53 69 / 10 20 10 10
MLU 51 69 51 68 / 5 20 10 10
DEQ 54 62 48 64 / 20 20 10 10
TXK 55 63 50 66 / 20 20 10 10
ELD 54 63 48 66 / 10 20 10 10
TYR 58 68 54 69 / 10 20 20 10
GGG 56 68 54 69 / 10 20 10 10
LFK 56 72 56 73 / 5 20 20 10