Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/22/19
Area Forecast Discussion
National Weather Service Amarillo TX
950 PM CST Sat Dec 21 2019
VFR conditions expected at all three terminals over the next 24
hours. Skies will be mostly clear with gradual increase in high
clouds from west to east after 00Z Monday. Winds will be light, less
than 10 kts, out of the south to southwest until 18Z Sunday. After
18Z winds should be out of the southwest around 10 kts.
.PREV DISCUSSION... /Issued 514 PM CST Sat Dec 21 2019/
VFR conditions expected at all three terminals over the next 24
hours. Skies will be mostly clear with surface winds less than 10
kts from the south, then southwest.
PREV DISCUSSION... /Issued 301 PM CST Sat Dec 21 2019/
SHORT TERM...Today through Tomorrow...
Current mid-level water vapor satellite and RAP 500mb heights show
the upper level closed low over southeastern Oklahoma with a ridge
building over Baja California and southwestern Arizona. Dry air
is wrapping around the back side of the closed low with clear
skies across the forecast area today. Light winds and sunny skies
make for a beautiful Saturday with temperatures getting up to
around 60. The upper level ridge will build east over the
Southern Plains through tomorrow night.
Crisp low temperatures tonight with a continuation of clear skies
and light winds. South southwest winds of 5 to 15 mph will
prevail through tomorrow with high temperatures warming into the
60s and possibly the lower 70s in the far western Oklahoma
Panhandle. The forecast area will continue to remain dry with no
chances of precipitation today and tomorrow.
LONG TERM...Monday through Saturday...
Latest 21/12Z model and numerical data continue to show a dry
start to the forecast period with possibly some fire weather
conditions for parts of the region. This will be followed by a
trend of cooling temperatures with our next chance of
precipitation by the end of the forecast period.
The main H500 ridge centered over western Oklahoma by Monday
afternoon in-conjunction with a surface trough developing over
SW KS/SE CO will help establish good southwesterly flow. With good
adiabatic heating, temperatures will rise into the mid and upper
60s. Fire weather concerns are possible and will be further
discussed in the fire weather section.
Going from Christmas Eve Day into Christmas Day, the first mid
level disturbance will move east across the Four Corners Region.
By Christmas morning, as the system weakens quite a bit with
limited moisture in-conjunction with fast forward prorogation,
beside a light isolated shower, it will remain mainly dry with
high temps on Tuesday and Wednesday ranging from the mid 50s to
A second, and potentially stronger H500 level disturbance will
move equatorward along the California coastline by Thursday
before moving east across the far SW CONUS on Friday. Going past
Thursday, latest 12Z model data are not in an accord. Stronger
disturbance with further northern track illustrated by the GFS/CMC
taps into Gulf of Mexico moisture, especially areas downstream of
the main trough. This will help bring more moisture into the
region starting Friday through Saturday. A second solution
illustrated by the ECMWF showing the center of the upper level
low further south moving east across northern Mexico displacing
the moisture transport further to the east across Texas hill
country north into central Oklahoma by the end of the forecast
period. Precipitation type may follow diurnal trends with rain
during the day and a wintry mix during overnight hours. Exact
precipitation type is uncertain at this time, if precipitation
makes it to the panhandles. Some guidance even shows some CAPE in
the SE TX panhandle with some thunder possible as well. Will
monitor and update accordingly as we get to the end of next week.
Temperatures will drop to below average by the end of the
forecast period, especially in the wake of a cold front moving
through the region.
Elevated to localized near critical fire weather conditions are
possible Monday mainly over the western and central Oklahoma
Panhandle and the northwest Texas Panhandle. This is due to dry
fuels, increasing southwest winds, and low minimum relative
humidity values. Min RH values maybe as low as 9 percent with SW
20 ft winds of 15-20 kts.
Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
728 PM CST Sat Dec 21 2019
Updated forecast to add patchy fog to much of the CWA for the
09-15z Sunday period, despite a low risk for fog given recent
SREF visibility probabilities. Considering the expected surface
mininum temperatures and the most recent dew points, anticipate
the development of near zero dew point depressions. Further, the
NAM and RAP deterministic soundings at select locations suggest a
nearly saturated surface with much drier aloft at 12z Sunday. The
surface wind speeds are expected to be light/variable along with
significant radiational cooling.
.PREV DISCUSSION... /Issued 524 PM CST Sat Dec 21 2019/
Note Aviation Discussion below corresponding to the 00z TAFs.
VFR conditions during the period, except for brief MVFR
visibilities during the 09-15z Sunday period. light north wind.
PREV DISCUSSION... /Issued 259 PM CST Sat Dec 21 2019/
SHORT TERM (Tonight through Sunday Night)...
Surface ridging continues to infiltrate the region with drier north
winds. Although stratus should be scoured away from the region late
this afternoon, a lingering subtropical plume of moisture high aloft
will keep some high clouds intact before this plume departs after
midnight. Not yet biting on the NAM`s radiation fog potential
tonight even following the recent soaking rains over much of the
area. Lower theta-e advection and steady north winds should tend to
offset fog potential, but this will be monitored through the night.
Full sunshine awaits tomorrow as the surface ridge axis arrives
with very light north winds and highs closer to seasonal norms.
LONG TERM (Monday through Saturday)...
Warming trend continues Monday under surface high pressure and a mid-
level ridge building in the from the west. Surface high pressure
sliding east Monday night/Tuesday while an area of surface low
pressure developing across the southern High Plains will result in
weak to moderate onshore flow redeveloping by Tuesday.
In the meantime, a mid-level longwave trough will begin to move
inland along the Pacific coast and dig through southern California
and Desert Southwest Tuesday, becoming slightly stationary. This
trough will, however, nudge the mid-level ridge eastward, creating a
southwest to northeast flow aloft across Texas. Embedded shortwaves
in the flow aloft Thursday will introduce a slight chance for rain
across the Brush Country.
Moisture will continue to gradually increase through the week, so
that by Friday, PWATs of 1.0 to 1.3 inches are to be expected. Rain
chances will also increase for the latter half of the week. The
longwave trough will move east late in the week, bringing a cold
front through the region. Timing and development of the trough
differ between the GFS/ECMWF long-term models, resulting in timing
differences at the surface with regard to the front. GFS continues
to run slightly faster, while the ECMWF is slower due to the model
attempting to create a cut-off low which would slow any progression.
Continued to lean with the GFS with timing of the fropa for
Saturday, but will linger POPs through Sunday.
Daytime highs are expected to warm into the upper 70s to lower 80s
through the week. Overnight lows will also gradually warm into the
50s, although are expected to cool Saturday night in wake of the
Moderate northerly flow will continue tonight and reach SCEC levels
by Sunday morning. As high pressure draws closer Sunday afternoon,
offshore flow will gradually lessen. Weak offshore flow will become
onshore by late Monday afternoon as the high pressure ridge moves
to the east. A weak to moderate onshore flow will occur Tuesday
through Thursday as a trough of low pressure forms over the
southern high plains. Rain chances will increase late in the week
as another cold front approaches the region.
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 42 65 40 68 43 / 0 0 0 0 0
Victoria 40 64 37 69 40 / 0 0 0 0 0
Laredo 39 69 40 72 43 / 0 0 0 0 0
Alice 40 67 38 70 41 / 0 0 0 0 0
Rockport 44 62 45 66 49 / 0 0 0 0 0
Cotulla 35 69 36 73 38 / 0 0 0 0 0
Kingsville 41 67 39 70 41 / 0 0 0 0 0
Navy Corpus 48 62 47 64 50 / 0 0 0 0 0
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
539 PM CST Sat Dec 21 2019
Issued at 229 PM CST SAT DEC 21 2019
Main challenge in the short-term continues to be potential for low
clouds and fog development. Latest satellite imagery shows an area
of low clouds and fog extending from south-central KS into parts of
east-central KS that has been eroding around its edges. Models
have really struggled with this low-level moisture the last few
days. However, the NAM, ARW, NMM, and 3km NAM, are handling this
area of clouds reasonably well. Where they`re failing is the
eastward extent. The GFS, RAP, and HRRR are doing a better job
with the moisture further east into our forecast area. Feel like
with the clouds eroding that the GFS, RAP, HRRR will be a better
choice for this afternoon into the overnight hours. So have
generally clear skies forecast through the overnight. But I can`t
rule out the possibility that the stratus deck builds east with
time this evening and overnight.
For Sunday - Wednesday, models have trended dry and as a result,
warmer. We should see highs climb to near 60 degrees each day. Low
cloud cover, like the NAM, ARW, and NMM show would keep hold
temperatures back though. But for now, confidence is higher that
we`ll be warmer like the GFS, Canadian and ECMWF show. It`s
possible highs could get into mid 60s, especially across the
southwestern quadrant of the forecast area. Records for the KC
area are 67, 66, and 67 for 12/23, 12/24, and 12/25 respectively.
These seem out of reach at this point given the latest suite of
The next chance for any precipitation continues to looks like next
weekend. Models move a strong trough through the middle of the
country Saturday into Sunday. For now, this looks like primarily a
rain event for the area as cold air lags behind until late, as the
system is exiting, with only a brief wrap around chance for snow.
.Aviation...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 538 PM CST SAT DEC 21 2019
Unfortunately the forecast for tonight is still a tough one
regarding fog/low stratus potential. The NAM12 and NAM3km still
have the entire area socked in with fog/low stratus. These models
tend to go overboard with moisture though, so don`t feel
comfortable leaning on them. The ARW is more in the middle with
some patchy to areas of fog possible across the area. The RAP,
HRRR, GLAMP, and GFS all show some low level moisture in the area,
but not enough for fog/low stratus development. Given that the
area of fog/low stratus that has been in eastern KS still looks to
be eroding, going to lean on the conservative solutions.
Therefore, have kept the one line TAFs going for now, but will
continue monitoring for any signs of a change. Right now, if there
are drops in visibility, they should stay above 6 SM. As for
winds, they should stay light and out of the south-southwest.
Area Forecast Discussion
National Weather Service Grand Forks ND
934 PM CST Sat Dec 21 2019
Issued at 930 PM CST Sat Dec 21 2019
Reports of BR and fog have been reported in Pembina, Cavalier, and
Walsh counties this evening. Continued warm air advection over the
snow pack will lead to continued chances for mist or patchy fog
overnight, mainly for the northern portions of the Red River
Valley, where temperatures remained lower today; lows here will
fall into the middle to upper teens. Elsewhere, partly cloudy
skies prevail with overnight lows falling into the lower to middle
UPDATE Issued at 711 PM CST Sat Dec 21 2019
Made slight adjustments to temperatures within the Red River
Valley through Sunday evening to reflect persistent southerly
winds. Warmer temperatures remained outside the Valley through
much of the day today. Looking at the latest guidance, we could
see a similar setup for Sunday but with a slightly better chance
of warming as west to southwest winds look to work slightly
.SHORT TERM...(This evening through Sunday night)
Issued at 259 PM CST Sat Dec 21 2019
Little to no impactful weather is expected through Sunday night,
except for potential for fog during the overnight hours.
The latest satellite imagery shows broken cirrus clouds continuing
to stream eastward overhead amidst strong upper and mid level
ridging. A stout inversion in the 850-925 mb layer will persist
through Sunday. Given the heightened potential for snowmelt today
and Sunday, snowmelt-enhanced moisture may become trapped in the
near surface layer under this inversion prompting potential for fog
development with nocturnal cooling tonight and Sunday night.
Deterministic model soundings and the latest SREF and HRRR
guidance suggest the best chance for fog development tonight would
be in the northern Red River Valley and northeast ND where winds
are progged to be weaker. Confidence is low regarding coverage and
duration of potential fog, so will monitor overnight.
Subtle daytime boundary layer mixing into the aforementioned
inversion combined with WAA in westerly and southwesterly winds
brought significant warming today, with temperatures climbing into
the mid to upper 30s across portions of eastern ND along and west of
the RRV escarpment. Further east along the Red River Valley, south
winds and a persistent cold dense valley airmass have kept
temperatures lingering in the mid to upper 20s. East of the
valley across treed areas in portions of northwest and west
central MN, lower albedo has allowed for temperatures to climb
warmer into the mid 30s to near 40 degrees. Cirrus clouds are
expected to persist overnight and into Sunday, tempering nocturnal
cooling with lows expected to fall into the 20s. Assuming that
any nocturnally developing low level stratus and fog do not linger
for very long, localized temperature trends should be similar on
Sunday, relying heavily on the solar radiative influences of
terrain, land cover, and snowpack. However Sunday will be slightly
warmer as even warmer 850-925mb air reaches the 10-15C range.
.LONG TERM...(Monday through Saturday)
Issued at 259 PM CST Sat Dec 21 2019
A return to seasonal temperatures is expected for Christmas week
with snow chances Christmas night and into Thursday.
Monday through Tuesday...
A progressive upper level impulse propagating across southern Canada
within a larger ridging regime is forecast to bring a weak attendant
surface cold front through the region late Sunday into early
Monday morning. This will bring increased cloud cover and cooler,
more seasonal temperatures for Monday and Tuesday with highs in
the upper 20s and possibly low 30s. There are some indications in
recent guidance that boundary layer saturation may be
sufficiently deep enough to promote patchy freezing drizzle at
times during the Monday night/Tuesday morning time frame, but high
variability between recent model runs yields low confidence in
this occuring. While this appears to be a reasonable worst-case
scenario for now, any freezing drizzle may cause local travel
impacts. The most likely scenario is for cool and cloudy
conditions to prevail.
Christmas Day through Thursday...
The first half of Christmas Day is expected to be dry and
seasonable for the region with afternoon temperatures in the 20s.
Snow chances will increase for the evening/overnight hours and
As upper level ridging shifts eastward through mid week, a southwest
flow regime is expected to be in place over the region by late
Wednesday. A shortwave trough with an attendant surface low
propagating into the central Plains are expected to deepen as they
move northeastward towards the upper Mississippi valley region on
Thursday. Widespread light snowfall is likely to begin Christmas
night as broad-scale ascent associated with the approach of the
upper level wave moves into the region. Stronger ascent due to mid
level warm advection, and possibly areas of frontogenetical
banding, will slowly move into the region through Thursday and may
bring areas of higher snowfall amounts.
Confidence in snowfall occurring is fairly high as most GEFS members
show at least light snowfall during the Wednesday night/Thursday
time period. However, confidence in amounts is generally low due to
high ensemble spread and low confidence on the strength and
placement of stronger ascent associated with warm air advection and
possible frontogenetical banding. Looking through a historical
lens, current guidance suggests that this storm will not be
unusually strong for this time of year and so is not likely to
bring high-end impacts to the region. However, even light to
moderate snowfall during the holiday travel period may cause some
travel concerns. Those planning on traveling on or after Christmas
day should continue to monitor the forecast for potential travel
Friday through Saturday...
Generally quiet and cool weather is expected following the Wed
night/Thursday system as surface high pressure builds over the
region. Temperatures will remain fairly seasonal with highs in the
There are some indications in ensemble guidance that a second upper
level shortwave moving through the mean southwesterly flow aloft
could bring snow chances to the central US late Saturday and into
Sunday. While this potential will be monitored, there is currently
too much ensemble spread to say for certain whether the region will
see any impacts.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 516 PM CST Sat Dec 21 2019
VFR ceilings prevail this evening for most sites. For GFK, look
for a broken stratus deck and a slight chance of mist or freezing
drizzle. Westerly winds are expected to continue outside of the
Red River Valley, with southerly winds persisting into Sunday
for the Valley locations of KGFK and KFAR. This will create a
tendency for LLWS beginning during the mid-morning, then
persisting through much of the day as winds aloft will remain out
of the west.
Area Forecast Discussion
National Weather Service Key West FL
1023 PM EST Sat Dec 21 2019
The next 48 hours will need to be watched for a few different
types of weather-related hazards. These include heavy rain,
severe thunderstorms, and rising tides within Florida Bay. The
weather will be generally windy or breezy, but no more so than
What will be causing this? A multi-lobed non-tropical area of low
pressure is in the process of developing in the Central Gulf over
the warm 80+ degree waters of the Gulf Loop Current. A warm front
extends east from this feature near or just north of the Keys,
with a weakly to moderately unstable air mass along and south of
the warm front. A strongly veered wind profile has been in place,
with easterly winds at the surface and west-southwest mid-level
flow. Convection has not been able to root well into the boundary
layer this evening, but that should be less of an issue on Sunday
as surface winds veer more southeasterly and blow more directly
off the 81-degree Gulf Stream waters south of the Keys.
Interestingly, a persistent convective cluster has been
continually re-developing in place this evening between the
Marquesas Keys and the Dry Tortugas, perhaps where lift along the
front has been maximized. Radar indicates a large area of storm-
total rainfall of 3-6 inches today from the Marquesas Keys
westward. What`s concerning is to see a couple of more reliable
mesoscale models such as the HRRR and the ARW slowly gyrating and
morphing this glob of heavy rain eastward across the Lower Keys
sometime on Sunday. On one hand, some convective cells will be
slow to move, but the veered wind profile will favor training and
re-generation of convective cells. By Sunday night, the
experimental Caribbean HRRR shows much of the Keys getting 5+
inches of rain, and the ARW shows a more splotchy and variable 2-8
inches of rain, heaviest over the Lower Keys. This raises a
concern for localized flooding, especially if this develops in the
more urban environment of Key West. This could make a drive on the
Overseas Highway a slow, sloggy affair with hydroplaning and
On Sunday PM, a cold front trailing from the deepening low over
the northeast Gulf will reach our western waters and move
eastward. It appears that a frontal wave will develop along the
advancing front as it crosses the southeast Gulf and crosses South
Florida toward the northwest Bahamas. This sharpening of the front
as it reaches our area could also sharpen a line of thunderstorms
as it progresses across the Keys on Sunday evening. The 3km NAM
and shows potential for discrete cells in advance of the main
line. Any discrete cells preceding the main line of thunderstorms
will have a favorable unstable and sheared environment for
organization and rotation. This poses the greatest threat for
severe thunderstorms. SPC currently has the Keys in a Marginal
Risk for severe thunderstorms on Sunday and Sunday night, and
their outlook discussion leaves room for a targeted increase to
Slight Risk. The main severe mode will be damaging wind gusts, but
a tornado cannot be ruled out.
Once the front sweeps through late Sunday night, rain chances will
drop significantly, with a few weak showers following the front.
The main threat following the front will be a rise in tide levels
over Florida Bay due to west winds pushing water into the basin.
This threat should peak around late Monday.
Many harbors in the Keys are on west-facing shorelines, which is
good for our normal easterly trade winds. So the west winds on
Monday will bring choppy and rough conditions into those harbors.
The Florida Keys and surrounding coastal waters are currently
wedged between a developing low center over the Central Gulf and
strong high pressure over the U.S. Mid- Atlantic region. This
pressure gradient will continue to support strong breezes
overnight. Low pressure will deepen as it moves through the
northeast Gulf tonight and Sunday morning. Strong, thundery
squalls will be possible across the coastal waters Sunday and
Sunday night. A trailing cold front will cross the coastal waters
of the Florida Keys Monday morning. Breezes will diminish Tuesday
night and Wednesday.
Through 22/24Z, prevailing VFR conditions are expected at both EYW
and MTH. For overnight and Sunday morning, occasional MVFR ceilings
are possible as fast-moving light rain showers move within the
vicinity of EYW and MTH. The chance for thunderstorms and IFR
ceilings and visibilities gradually will increase Sunday and Sunday
afternoon as a frontal system approaches from the Gulf of Mexico.
The best chance for a sub-VFR episode will be from 22/18Z-22/24Z.
Finally, southerly crosswinds will increase throughout the day.
GM...Small Craft Advisory for GMZ031>035-042>044-052>055-072>075.
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