Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/29/20
Area Forecast Discussion
National Weather Service Dodge City KS
800 PM CST Sat Nov 28 2020
Issued at 800 PM CST Sat Nov 28 2020
Based on radar trends (moderate rain in northern Clark county
moving north) and latest HRRR trends, increased and expanded pop
grids for the next several hours. Several short term high
resolution models show light rain reaching the US 50 corridor by
midnight. After midnight, the rain will dwindle and shrink
southeastward as the closed low pulls away.
.SHORT TERM...(This evening through Sunday)
Issued at 348 PM CST Sat Nov 28 2020
During the mid afternoon hours, an upper low continued to move
slowly east into the western Texas Panhandle. This system was quite
small and rather moisture-starved, but was still formidable enough
to produce light rain and even some snow across portions of the
Texas Panhandle today. This system was also cold-air starved, so
pretty much all the snow was confined to higher elevation areas of
the western Texas Panhandle and adjacent northeastern New Mexico
right near the cold-core center of the upper low itself. As the
upper low moves east tonight, it will continue to move across lower
elevation, and thus the preponderance of precipitation should stay a
cold rain this evening and overnight.
The question is how far north this precipitation will reach. Some of
the latest short term, high-resolution models suggest some very
light measurable cold rain may make it as far north as Highway 50
before dissolving. We will carry some 50-60 POPs mainly in the Red
Hills region nearest Oklahoma border through the night.
Precipitation amounts up to a tenth to perhaps fifteen hundredths is
about all that can be expected tonight.
As this upper low pulls away early Sunday, the active northern
branch of the polar jet will have a strong wave of its own, moving
southeast from the Dakotas across the Midwest region. A strong
surface cold front will push quickly south Sunday morning. The going
forecast already had north winds behind the front handled fairly
well, and our latest forecast is simply a continuation of what we
had going -- sustained 25 to 35 mph much of the day with gusts 40 to
45 mph. A couple of 50 mph gusts will also be possible, particularly
mid to late morning tied to the highest pressure rises immediately
behind the front. The airmass behind the front will not be bitterly
cold, but the strong winds will certainly create a bit to the air as
temperatures struggle to reach mid to upper 40s.
.LONG TERM...(Sunday night through Saturday)
Issued at 348 PM CST Sat Nov 28 2020
Interesting potential weather in the Long Term. There are some
changes that have started to show up in the global models this
morning that the latest NBM have not yet caught up to. The Canadian
GDPS and ECMWF models are now showing a potent jet digging south
across the Rockies, carving out an impressive upper low across the
Central Plains mid-week -- insomuch that both these models are
showing 0.25 to perhaps 0.50 of storm total QPF across portions of
southwest/central Kansas centered on Wednesday and Wednesday Night.
This is quite a drastic change in global models showing this
westward shift in upper level low formation. The thermodynamic
profiles would certainly support snow if this indeed pans out.
It should be noted that the official forecast going out this
afternoon has ZERO mention of any precipitation -- as there is not
quite the appetite yet to alter the NBM starting point -- as the
morning NBM has 12-hr POPs around 5 to 10 percent with no weather
mention. The GFS remains farther east with no precipitation, so
until all the major global models start lining up, blended solutions
(i.e. NBM) will be slow to show anything formidable with respect to
precipitation. It is something that will have to be watched closely,
however, and the end user should be cognizant of the fact that the
mid-week forecast may change quite a bit given how chaotic the large
scale hemispheric pattern is right now.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 435 PM CST Sat Nov 28 2020
Radar indicates areas of light to moderate rain near LBL as of
2230z. Included a TEMPO group for -RA for LBL through 01z Sun,
after which time rain in the vicinity of LBL is expected to
diminish. MVFR ceilings currently at LBL are expected to persist
much of the night, as a closed low drifts from near AMA at 00z Sun
to western Oklahoma at 12z Sun. Elsewhere, VFR will continue
tonight, with broken mid level cloud as far north as GCK/DDC and
light west winds. A strong cold front is expected to sweep through
the airports around, or just after, 12z Sun. After 15z Sun, strong
north winds will impact aviation operations at all terminals with
gusts of 35-40 kts. The strongest winds are expected during the
late morning/midday hours, before gradually relaxing late Sunday
afternoon. Very dry air will promote VFR/SKC Sunday and Sunday
.PRELIMINARY POINT TEMPS/POPS...
DDC 32 46 19 49 / 30 0 0 0
GCK 30 45 16 49 / 20 0 0 0
EHA 28 46 19 53 / 30 0 0 0
LBL 28 47 17 51 / 60 0 0 0
HYS 31 45 17 47 / 0 0 0 0
P28 38 49 23 47 / 50 20 0 0
Area Forecast Discussion
National Weather Service Des Moines IA
530 PM CST Sat Nov 28 2020
.DISCUSSION.../Tonight through Saturday/
Issued at 212 PM CST Sat Nov 28 2020
High pressure centered over southern Missouri has allowed for clear
skies today. In fact, the nearest clouds on GOES-East satellite are
several hundred miles away in Oklahoma/southern Kansas or North
Dakota. Abundant sunshine and southwest winds into the area allowed
temperatures to climb into the mid to upper 50s by 2 pm for most
Big changes are on the way, however, as a cold font draped across
the northern plains will dive south and across Iowa Sunday morning.
Southwesterly winds will shift to northwesterly with temperatures
dropping rather substantially. Highs for Sunday will will have a
hard time cracking 40 degrees with most places topping out in the
mid 30s. This will be accompanied by gusty northwest winds behind
the front thanks to a tightening pressure gradient with decent cold
air advection and subsidence into the area. Model soundings indicate
winds at the top of the mixed layer of 30-36 knots depending on
model or location with sustained winds at 18-23 kts. Hi-res models
such as the hrrr and href suggest better gusts will occur in the
southern Nebraska/northern Kansas vicinity. Thus, have opted not to
issue a wind advisory as the area remains a few knots shy of
criteria. Regardless, it will be a cold and blustery day exacerbated
by the relatively mild conditions seen Saturday. Temperatures will
continue to drop Sunday evening and with brisk winds continuing
overnight Monday morning wind chills will be rather unpleasant...in
the single digits.
The forecast for the upcoming week is rather quiet with no
precipitation chances in the current forecast at all. While the area
will be moisture starved, this does not mean that the pattern is
quiet. In fact, the atmospheric pattern over the upcoming week is
quite complicated with a number of deep closed lows moving across
the country with embedded shortwaves. At certain points the
evolution of the systems resembles somewhat of a fujiwhara effect
before lifting east. The split flow cuts off moisture to the area
but the complicated pattern yields high uncertainty in the
temperature forecast for the upcoming week as these systems drop
out of Canada. Placement of these systems could result in fairly
substantial differences in temperatures.
.AVIATION.../For the 00Z TAFS through 00Z Sunday evening/
Issued at 530 PM CST Sat Nov 28 2020
Quiet aviation weather is expected overnight prior to a cold
front arriving toward daybreak. Widespread VFR conditions are
forecast along with southwest surface winds. The front is forecast
to pass through the state on Sunday morning with very strong
northwest winds on the backside. Have increased wind speeds and
gusts during the day on Sunday and also have added additional
cloudiness as climatologically very favorable for status
development on backside of frontal passages this time of year.
Have kept any ceilings VFR at this time given only limited support
for status in guidance.
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
648 PM CST Sat Nov 28 2020
...Short Term and Aviation Update...
Issued at 647 PM CST Sat Nov 28 2020
Some thoughts on wind speed potential Sunday:
As already outlined by previous forecast in main afternoon
discussion below, strong north winds are the main feature on
Sunday. However, after perusing various model soundings and
leaning a bit more toward the latest RAP13, have slightly-
increased mainly gust potential in our official forecast, with
worded products now calling for more in the way of 40-45 MPH than
35-40 MPH. In turn, have refreshed our Hazardous Weather Outlook
(HWOGID) to hit winds a bit harder as well. Even so, am a little
concerned that we still may not be hitting max gust potential
quite hard enough, as the more aggressive solutions (not only the
RAP but also the HREF mean) suggest that especially the 8-11 AM
time frame could feature sporadic gusts to around 50 MPH, as this
time frame features the greatest overlap between the onset of
diurnal mixing and the strongest winds a few thousand feet off the
deck (before they weaken somewhat heading into afternoon).
Fortunately, do not think we will see gusts quite as high as
.DISCUSSION...(This evening through Saturday)
Issued at 229 PM CST Sat Nov 28 2020
The biggest issue for this forecast will be wind for Sunday.
An upper level trough will swing through within progressive flow
tomorrow with an associated cold front pushing through overnight
tonight. Surface pressure rises near 5 mb/3 hours will give us 30-35
mph wind gusts overnight, with wind gusts likely subsiding in the
early morning, before increasing as low-level mixing occurs and
brings momentum transfer to the surface near 40 mph wind gusts. This
will be a dry frontal passage with bone dry air and plenty of
subsidence behind the front. Temperatures should stay cool enough to
avoid critical fire weather criteria, although it still looks like
we could get into the near-critical range in our southwest, and with
wind gusts near 40 mph with such dry conditions, I would not be
surprised about a random grass fire or two for Sunday. Wind speeds
should be on the decrease during the afternoon as relative humidity
bottoms out, so we would at least have that going for us, although
Mid and long term models indicate some ridging at the beginning of
the work week until a sort of dumbbell-looking feature toward mid-
week. Although we will lack deep level moisture, there could be
enough lift to squeeze out some non-measurable precip.
Temperatures will be largely seasonable, although could be a bit on
the cool side during mid-week if a dumbbell upper low passes
overhead and brings in cooler air and more sky cover. Still, a dry
forecast for the next seven days outside of the mid-week shot at
some non-measurable precip that would not be out of the question.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday)
Issued at 647 PM CST Sat Nov 28 2020
High confidence in VFR ceiling/visibility and dry weather through
the period, with only some passing mid-high level clouds
anticipated. That leaves strong winds as the paramount concern
both at the surface and slightly aloft, as the early morning hours
Sunday are likely to feature some fairly strong northerly low
level wind shear (LLWS). More wind-specific details follow.
By far the lightest winds of the period will focus these first 8
hours or so, as speeds average under 10KT as direction gradually
shifts from southwesterly to westerly. Then a passing cold front
will arrive between 8-10Z, bringing increasing north-northwest
speeds with gusts around 20KT possible initially. The overall-
strongest winds of the period will focus during the daytime
Sunday, with several hours of sustained speeds 20-25KT/gusts
30-35KT. Although not officially included in current TAFS, gusts
could briefly reach 40KT mainly during the 14-17Z time frame.
Have introduced a period of fairly strong northerly low level wind
shear 08-14Z, as although surface winds will be on the increase
through this time, winds no more than 1-1.5K ft. above the surface
will be quite intense at around 50KT, resulting in a solid 35-40+
KT of shear magnitude between the surface and this level.
Area Forecast Discussion...UPDATED
National Weather Service Miami FL
802 PM EST Sat Nov 28 2020
High pressure over the Western Atlantic waters will move slowly
southward tonight into the Bahamas, as low pressure develops over
the Northwest Gulf of Mexico. This will allow for the steering
flow over South Florida to become more south/southeast but light
and allow for some low level moisture to work into the region from
the south. Therefore, the weather will remain mostly dry tonight
over South Florida with only an isolated shower over the east
coast metro areas and the adjacent Atlantic coastal waters.
Light winds and low level moisture over South Florida will allow
for some fog to develop over the interior and west coast metro
areas especially west of Lake Okeechobee late tonight into early
Sunday morning. Therefore, Fog has been expanded to include rest
of the interior and the west coast metro areas with even areas of
fog west of Lake Okeechobee for late tonight into early Sunday
Rest of the forecast looks good at this time and no other changes
.Prev Discussion... /issued 622 PM EST Sat Nov 28 2020/
The winds will remain light and variable over all of the TAF sites
tonight along with mostly dry conditions. Patchy fog should
develop over the interior areas of South Florida late tonight, but
remain away from most of the TAF sites. The only exception is for
APF taf site where the vis and ceiling could fall down into MVFR
conditions between 08Z and 11Z due to fog.
Prev Discussion... /issued 303 PM EST Sat Nov 28 2020/
Short Term (Rest of today through Sunday)...
Rest of today...
A broad area of weak low-level high pressure is evident across
the region via the latest RAP analysis and GOES-16 water vapor
imagery loops. This is supporting very weak low/mid-level flow
across southern Florida. The MFL 12Z RAOB captured this weak low-
level flow pattern quite well -- depicting a cloud-layer mean wind
of 9 knots from the WNW. Aloft, a swath of enhanced mid/upper-
level southern steam flow is evident across northern Florida.
While there may be some weak upper-level divergence associated
with this area of enhanced flow, large-scale forcing for ascent
remains nearly negligible across the South Florida CWA.
The large-scale pattern discussed above is supporting a strong
750- mb subsidence inversion -- below which a relatively moist
layer is evident via this previously mentioned MFL RAOB
(characterized by low- level RH near 80%). This shallow moisture
combined with a north- south oriented mesoscale coastal boundary
across the Atlantic waters is supporting shallow convective
showers with very little in the way of motion. In fact, most of
these showers appear to be anchored along the western periphery of
the Gulf stream, where localized heat/moisture fluxes are
supporting higher theta-e marine boundary layer air.
Considering the relatively rich low-level moisture below the
above mentioned inversion and fairly dense cloud coverage/debris
over the Atlantic coastal waters, the coastal boundary layer has
remained somewhat sheltered from diurnally-driven inland vertical
mixing. This has preserved the surface moisture -- supporting a
small uptick in weak surface-based buoyancy along the southeast
coast (nearing 500 J/kg this afternoon). Further west, nearly
clear skies is supporting efficient surface heating, which has
generally mixed out the above mentioned rich low-level moisture
and actually stabilized these areas to an extent. That being said,
areas over western Miami- Dade County/inland South Florida could
see isolated showers develop, owing to the interface of deeper
inland boundary-layer mixing and the above mentioned
moist/sheltered coastal boundary layer. Therefore, isolated
mesoscale driven convective showers remain possible along the
immediate Atlantic coastline of Miami-Dade and Broward Counties,
with lower chances extending inland.
Any showers that do manage to develop over land areas today will
be shallow in depth -- owing to warm/dry mid-level air and
associated strong convective inhibition (SBCINH near -150 J/kg). A
lack of any appreciable large-scale forcing for ascent will
inhibit parcels from reaching their LFCs within this fairly
hostile thermodynamic environment. That said, the very slow/non-
existent storm motions and slow propagation vectors will support
some light rainfall accumulations across metro Miami-Dade County.
The relatively light nature of these showers should greatly limit
the threat of urban/street flooding, but if any shower becomes
locally enhanced and moves slowly over a particular coastal area,
ponding of water could occur, though unlikely.
Weak high pressure will remain in place across the region,
supporting very similar conditions to that of today. Isolated
coastal showers will be possible, but coverage and intensity
should be low. Temperatures will remain seasonable for this time
of year. Winds begin to transition to a southerly direction, but
remain light overall.
Long Term (Monday Through Saturday)...
The extended period opens up with high pressure retreating into
the Atlantic as a complex low over the Gulf Coast states begins to
traverse northeastward, pushing a frontal boundary down the
peninsula and across South Florida mid Monday into early Tuesday.
Current model solutions, albeit still showing minor differences
in timing, depict the low quickly progressing up the eastern
Seaboard along with the best upper level dynamics. Therefore,
showers with perhaps a few thunderstorms are possible with the
Behind the front, high pressure builds back across the peninsula,
with northwesterly to northerly flow advecting a colder and drier
airmass into the region. The coldest temperatures should be felt
Wednesday morning with overnight lows dipping into the upper 40s
to lower 50s across coastal metro areas and mid to lower 40s over
the interior and western Lake Region. This will be somewhat short-
lived as high pressure slides further eastward, veering the flow
out of the northeast then east, essentially inciting a warming
and slight moistening trend as the airmass modifies by late week.
Guidance then hints at the potential for cyclogenesis in our
vicinity, along with a second frontal boundary by the tail end of
the week and into next weekend. Unsurprisingly, agreement this
far out is poor in regards to timing, location, trajectory, and
overall impacts to South Florida. This will be something that will
be monitored with each model run and as we get closer in time.
A weak area of high pressure over the region will continue to
support light winds and generally benign marine conditions across
the local waters through this weekend. Early next week, a cold
front will approach the area and bring an increase in winds and
associated hazardous marine conditions, which will persist until
late next week.
Aviation (18Z TAFs)...
Primarily VFR throughout the period, with weak high pressure and
light/variable wind flow in place. Shallow moisture continues to
support VFR cigs along the southeastern portions of S FL this
afternoon, as well as brief passing SHRA. Convective coverage is
too minimal to mention in the TAFs, but brief MVFR cigs/vis could
accompany this activity along the eastern terminals.
.Preliminary Point Temps/PoPs...
West Palm Beach 68 82 70 84 / 10 10 10 30
Fort Lauderdale 70 83 70 84 / 10 10 10 20
Miami 69 83 71 84 / 10 10 10 20
Naples 67 83 70 81 / 0 10 10 70