Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/17/20
Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
600 PM CST Sun Feb 16 2020
For the 00Z TAFs, areas of fog and low clouds are forecast to
develop once again across eastern and northeast parts of the OK
and TX Panhandles late tonight into Monday morning, dissipating
thereafter. At this time, the low clouds and fog are expected to
remain just east of KGUY and well east of KDHT and KAMA. Trends
will be monitored closely this evening. A brief period of LLWS is
also foreseen at KAMA late tonight. Finally, a cold front will
move across the TAF sites late tonight through mid morning Monday
with north and eventually northeast winds in its wake.
.PREV DISCUSSION... /Issued 206 PM CST Sun Feb 16 2020/
SHORT TERM...Tonight and Monday
Low clouds and fog lifted by 17Z/18Z today but likely will return
after 06Z Monday through 16Z Monday across much of the
northeastern portions of the Panhandles. The NAM and HRRR are once
again forecasting fog and low clouds advecting north and west
across most of the eastern Oklahoma and also the northeastern and far
eastern Texas Panhandles late tonight into Monday morning. Dry
northwesterly upper flow across the Panhandles tonight will
transition to zonal upper flow by 12Z to 18Z Monday. High level
cloudiness will continue to track southeast across the forecast
area tonight into Monday. A cold front front will push across the
Panhandles late tonight through Monday morning shifting the winds
to the north and northeast becoming breezy by early Monday
afternoon. Highs on Monday will remain above normal but slightly
cooler from Sunday`s high temps. No precipitation is expected
Tuesday will start out fairly close to normal, with low
temperatures in the lower 30s, but the highs won`t get much
higher than the mid 40s. There remains a small chance for a few
snowflakes to fly in the far northwest, mainly in the Oklahoma
Panhandle. Have reduced our PoPs even more, as snow chances
through the day on Tuesday will be decreasing.
CLoud cover and north winds remain during the day on Wednesday,
keeping temperatures well below seasonable normals. For the second
straight day, high temperatures will struggle to break 40 degrees
across much of the area. Thursday will be the coldest day of the
week, with highs struggling to get above the freezing mark. At
least the current trend of warming up over the weekend looks to
remain intact, with temperatures rebounding into the 60s by
Saturday and Sunday.
Precipitation chances increase somewhat during the middle part of
the week as well, with the best chances for snow begin on
Thursday. By Tuesday, the medium range models are in decent
agreement in developing a strong, but narrow band of mid level
frontogenesis to our south, keeping precipitation chances mainly
to our south until the next short wave trough moves through late
Wednesday/early Thursday. By this time, chances for snow remain
for much of the area, yet at the moment, we`re talking about a 1
in 3 chance of light snow. We will continue to refine the forecast
through the week.
While the prospects look pretty good for some sort of
precipitation on Thursday, keeping the 1 in 3 potential for
a variety of reasons. The first is the inherent lower confidence
of a day 4 forecast and secondly because of the subtle, yet
important differences in the guidance. GFS and ECMWF deterministic
12Z runs appear to be in close agreement with the large scale
pattern by 00Z Friday (Thursday evening) with short wave ridging
just to our west and troughing to the east. The GFS ensemble mean
500mb flow shows the ridging will be much farther to the west, as
a result of about half of the GFS ensemble members showing a much
slower solution. Depending on exactly what happens with the speed
and strength of said system, this brings in uncertainty for day
4. The uncertainty is necessarily in the chances for snow, but the
timing of the snow.
Area Forecast Discussion
National Weather Service Columbia SC
1034 PM EST Sun Feb 16 2020
Low pressure will lift northeastward and farther away from the
forecast area tonight. Ridging will briefly dominate Monday. A
slow moving frontal system will be in the region Tuesday through
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Lingering light rain should end from west to east as low
pressure shifts farther away from the area. High-level moisture
will continue with stratus and fog through the night. Dense fog
may occur but have held off issuing a dense fog advisory for
now. The fog may be limited by cloudiness. The HRRR suggested
the lowest visibilities mainly northwest of the forecast area
closer to more shallow moisture and greater cooling.
Cloudiness will limit net radiational cooling overnight. The
guidance was close with lows ranging from the upper 30s north
to mid 40s southeast Midlands and lower CSRA.
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
A brief return to zonal flow Monday will cut off the deep moisture
from the Gulf of Mexico. With weak high pressure ridging conditions
remain mostly dry. High temperatures will be return to above
normal with highs in the low/mid 60s. Clouds will be on the
increase Monday night as high pressure retreats to the northeast
and low-level flow becomes more southeast and southerly. This
will keep low temperatures up into the upper 40s to lower 50s.
With an increasing southerly flow ahead of an approaching cold
front deeper moisture will return to the region by Tuesday. The
cold front from this system will stretch into the southeastern
US. Models have come into better agreement with moisture
overspreading the area Tuesday/Tuesday night. Rainfall amounts
look to range from one half inch up to one inch across the
region through Tuesday night.
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Rain is likely again Wednesday with moisture remaining
plentiful and the front crossing the forecast area. Temperatures
will be closer to normal in the northern Midlands to above
average in areas that remain on the warm side of the front
longer during the day Wednesday. Lingering moisture Thursday
could lead to additional chances for showers. The frontal
boundary will slow across the region as it becomes parallel to
the mid/upper flow. Both the GFS and ECMWF show another wave
moving along the boundary Thursday with low pressure developing
along the Southeast Coast. The models however differ on how far
southward the boundary will sink south/east. The GFS is more
robust with the boundary remaining farther northward and higher
pops across the region, the ECMWF is a bit farther south with
most of the precipitation along the coast. The GFS has been more
consistent from run to run with the system Thursday. Will lean
toward higher pops for the period. With the boundary to our
south and high pressure building in from the north, expect
temperatures to average below normal Thursday through Saturday.
Once again, over the next 5 days, some areas of the Carolinas
into Georgia will see rainfall totals ranging from 1 to 2
inches. This will affect the area rivers, which remain higher
than normal. Expect additional river flooding or current river
Strong high pressure will begin to ridge into the area behind
this front ushering in a dry and colder air mass for Friday
through the weekend. Gusty winds from the north contribute to
cold air advection Thursday keeping highs below average across
the forecast area. This high pressure will hang on through the
end of the week promoting clear skies and below average
.AVIATION /04Z MONDAY THROUGH FRIDAY/...
IFR restrictions in stratus and fog overnight and into early
Monday. Some improvement expected on Monday.
Regional radar still showing a few light rain showers across the
area. Trends indicate some weakening, so not confident that any
showers will reach the terminals. Shower activity will continue
to diminish and move out of the area by 06Z as low pressure
along the coast lifts northeastward. Ceilings have generally
dropped to IFR levels and should remain IFR/LIFR through the
overnight period and into Monday morning. Visibilities are a
little less certain, but generally expect MVFR visibilities in
fog overnight with potential to drop to IFR. Ceilings and
visibilities should improve some with heating and mixing by late
morning, but still expect MVFR ceilings to hang around for much
of the day. Winds will be light through the period.
EXTENDED AVIATION OUTLOOK...Showers and associated restrictions
Tuesday and Wednesday.
Area Forecast Discussion
National Weather Service Cheyenne WY
421 PM MST Sun Feb 16 2020
.SHORT TERM...(This evening through Monday)
Issued at 200 PM MST Sun Feb 16 2020
Lots going on weather wise across southeast Wyoming. Forecast
challenges range from strong winds to headline level snow in the
Water vapor imagery showing a shortwave tracking into our western
counties this afternoon on the nose of a 115kt jet max over
southwestern Wyoming into northwestern Colorado. Has been snowing
very heavily over the Snowy and Sierra Madre Ranges with well over
a foot of snow widespread. SNOTELS at Blackhall Mountain...and
Little Snake River in the Sierra Madre Ranges are reporting Snow
Water Equivalent well over an inch as of noon. Snowy Range SNOTEL
at Medicine Bow closing in on 1.5 inches of SWE. WYDOT webcams out
near Arlington this afternoon showing quite a bit of snow has
fallen with I-80 snow covered. With that area in the upward lift
of the strong jet...winds have come down...with gusts in the low
40 mph range at County Road 402 and Halleck Ridge. Needless to
say...WYDOT has I-80 closed at this time and would not expect it
to open any time soon.
Good agreement in short term models bringing the upper shortwave
into east central Wyoming this evening. HRRR and Hires mesoscale
guidance showing precip blossoming across Converse and Niobrara
Counties after 00Z as the shortwave lift moves over the area. At
the same time...snow out west begins to decrease quite a bit.
Only change with the afternoon package was to add central Laramie
County to the High Wind Warning. GFS 750 and 800mb winds over
Cheyenne this evening pick up to 50-55kts as winds shift northwest
behind the surface trough. Expecting enough subsidence behind the
shortwave to mix some of these winds down to the surface.
Some concern for the Arlington area tonight for possible blizzard
conditions with increasing winds. But given the decrease in snow
seen on mesoscale models for this evening...decided to stick with
the Winter Weather Advisory and High Wind Warning. Evening shift
will need to monitor closely. WOuld also advise to watch Converse
and Niobrara Counties as we are getting quite an increase in snow
totals up there for tonight.
Precip and winds begin to decrease Monday as shortwave exits east.
Snow ends from west to east through the afternoon Monday.
.LONG TERM...(Monday night through Sunday)
Issued at 200 PM MST Sun Feb 16 2020
Still looking at better conditions after Monday with lighter winds
and drier weather. Do have a dry shortwave that moves through the
area Wednesday that will likely bring us another shot of cold air.
Those trying to make plans late in February...we are starting to
see the GFS and ECMWF coming together on a potential winter storm
around the 24th of February. GFS further south...thus less snow
while the latest ECMWF hitting us with a classic Colorado low with
over 1 inch liquid equivalent. Stay tuned as the event draws
closer as this could be our next significant winter storm.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 421 PM MST Sun Feb 16 2020
IFR conditions expected at KRWL for low cigs and snow into Monday
morning before improving during the day. VFR elsewhere this evening
then some mainly MVFR cigs should develop over KCDR and KAIA after
06Z with snow showers around. Otherwise some gusty winds through
the period especially over the se Wy terminals.
Issued at 200 PM MST Sun Feb 16 2020
Minimal fire weather concerns as heavy mountain snow expected
through Monday afternoon. Even lower areas expected to pick up
accumulating snow...especially along and west of the Laramie
Range. A drier less windy pattern sets up after Monday for
southeast WYoming and Nebraska Panhandle...but colder temperatures
and favorable less wind should keep us from seeing critical fire
weather issues through the upcoming week.
WY...Winter Weather Advisory until 8 PM MST Monday for WYZ101>105-109-
High Wind Warning until 8 PM MST Monday for WYZ106-110-116-117.
High Wind Warning from 6 PM this evening to 8 AM MST Monday for
Winter Storm Warning until 5 PM MST Monday for WYZ112-114.
Winter Weather Advisory until 7 PM MST Monday for WYZ110.
NE...Winter Weather Advisory until 8 PM MST Monday for NEZ002-003-095.
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
828 PM CST Sun Feb 16 2020
Issued at 815 PM CST Sun Feb 16 2020
A few modifications made to the ongoing forecast overnight and
into Monday. First of all, easterly flow over the lingering
snowpack has allowed stratus to thicken and lower tonight. In some
areas along the edge of the cloud layer, fog has increased and
visibilities may drop below 1 mile at times. Latest RAP CPD plots
suggest that winds within the high RH layer will begin to turn
more southerly after midnight, which may allow this moisture to
advect northward slightly.
Other concern is a shift towards more liquid precipitation into
Monday morning away from snow. High-resolution model data through
the afternoon and early evening continue to emphasis stronger warm
advection in the 900 mb layer overnight, pushing temperatures
aloft between +2 to +3 along and south of interstate 90.
We`re still expecting light precipitation to develop over
northern Nebraska late this evening and move eastward into western
Iowa after midnight. Models show increasing frontogenesis within
the 700:750 mb layer pivoting back northward after daybreak as the
subtle shortwave arrives. This should assist in developing a
narrow corridor of light precipitation along and either side of
the Interstate 90 corridor through mid-morning. Boundary layer
temperatures will hold near to slightly below freezing, but may
attempt to rise in areas along and just north of Highway 20
Thermal profiles indicate that there will remain a stout melting
layer AOA 900 mb, which should should promote a mixture of sleet
and freezing rain. This idea has been supported by simulated
p-type data from HRRR/RAP along with the latest 00Z runs of the
ARW/NMM. The 00Z NAM remains an outlier solution, this evening,
with it`s QPF likely overly influenced by the presence of minor
All that said, modified forecast suggested the need for a winter
weather advisory for portions of southern Minnesota and northern
Iowa into mid-day Monday for up to a half inch of snow, potential
for a tenth of an inch of ice, and sleet.
.SHORT TERM...(This Evening through Monday)
Issued at 344 PM CST Sun Feb 16 2020
Complex, low confidence forecast in the near term with many
variables still in play. Models are offering a variety of
solutions, but have sided with a GFS/HRRR/RAP blend.
Trough of low pressure is expected to work out of the
intermountain west this evening and work into the plains
overnight. Low level warm air advection leads to weak isentropic
lift on the 290K surface after 06Z along the South Dakota/
Nebraska extending into northwest Iowa, however, models are
disagreeing on amount of low level saturation. If ample low level
saturation develops, then could see drizzle or light precipitation
develop, but CAMs are suggesting low level saturation would be a
struggle. Therefore, may have to wait till upper wave approaches
from the west towards 12Z. At that point, upper jet streak noses
into southern Iowa. Forecast soundings are suggesting a dry wedge
from just above the surface through 700 mb, with the warm nose
well above freezing. Models suggest band of 700mb frontogenetic
forcing across northwest Iowa, but with upper level div Q focused
further south, may trigger closer to the 800-850 mb front which is
just south of the forecast area. If that occurs (as the CAMs
suggest), there is a question as to how much precipitation will
fall in the forecast area. Have therefore trended down in
Surface temperatures at the time appear to be in the low to mid 30s,
favoring either rain or snow. Could be an area where conditions set
up just right for a brief period of freezing drizzle, but precise
location is a bit uncertain. As cooler air collapses southward
tomorrow afternoon, mid levels of the atmosphere dry out fairly
quickly. Therefore, there is a fairly confined window of
precipitation from approximately 09-19Z Monday, but precipitation
type is really uncertain. Best chance for precipitation looks to be
mainly across northwest Iowa, where up to a 0.10" of an inch of
precipitation will result in a light mixture of rain/snow. Snow
amounts are expected to be fairly light totaling around an inch or
less. With minor amounts of precipitation, will not issue any
headlines at this time, but will need to keep a close eye on model
trends in case icing potential increases.
.LONG TERM...(Monday Night through Sunday)
Issued at 344 PM CST Sun Feb 16 2020
Low level temperatures continue to fall into Tuesday morning behind
the departing wave. Colder air surging south Tuesday evening may
produce additional light snow. With a deep dendritic layer near the
surface across eastern South Dakota, have raised pops with
surrounding neighbors. Amounts look to be light, but snow ratios
will be near 20:1.
Extended forecast looks to be mainly dry. Have not made any changes
beyond Tuesday night with challenging forecast in the near term.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 519 PM CST Sun Feb 16 2020
Bit of a tricky aviation forecast this evening. IFR ceilings over
the snowcover areas will continue into the evening and early
overnight hours as easterly winds remain. However, precipitation
does begin to increase across Nebraska and slides east towards
Sioux City after midnight. This will likely fall in liquid form
with a cold rain expected.
Further north, as ceilings improve slightly (still IFR along the
Buffalo Ridge), mid- lvl frontal forcing begins to develop after
3am and could yield a mixture of snow/sleet/freezing rain along
the I-90 corridor and into portions of northern Iowa. Confidence
too low to indicate in current TAF, but may amend this evening if
guidance continues to hint at this development. Anticipating some
improvement in ceilings by mid- morning but still anticipating
MVFR to high IFR ceilings through the day.
MN...Winter Weather Advisory from 3 AM to noon CST Monday for MNZ080-
IA...Winter Weather Advisory from 3 AM to noon CST Monday for
Area Forecast Discussion
National Weather Service Key West FL
1013 PM EST Sun Feb 16 2020
A mild and dry evening is underway across the Florida Keys. Radar
detects just a few showers well west and southwest of the Dry
Tortugas, while satellite imagery shows only thin cirrus passing
overhead. Very light winds of 5 mph or less to calm have allowed
temperatures to drop down to around 70 degrees at some sheltered
interior locations, and even down to 67 degrees as of 9 PM at the
usual cool spot on North Big Pine. Temps are holding in the mid
70s at more exposed and waterside locations. Surface analysis
depicts a weak high pressure ridge extending from the western
Atlantic across the Florida peninsula and into the central Gulf of
Mexico, while a stalled frontal boundary lies to the north of
this ridge axis. The 00Z Key West sounding measured only a slight
reduction of PW to 1.50 inches, but did show a weak inversion
developing near 2500 feet. Recent MIMIC-TPW imagery shows a drier
airmass, with estimated PW values around 1.2 inches, spreading NW
from the Florida Straits across the Keys. This drier airmass,
along with the very weak low level flow, is likely responsible for
the lack of shower activity across our area this evening.
Overnight, the pocket of dry air currently moving through the area
should prevent any shower activity along the Keys. Although some
of the CAM guidance including the HRRR does depict scattered
showers developing near the Keys after midnight, it seems more
likely that any such activity would remain over the Straits and
south of the island chain. The lack of any shower activity or even
clouds over the Straits at present also brings into question the
accuracy of the CAM guidance forecast. Otherwise, expect clear to
partly cloudy skies due to the passing high clouds, with light
winds allowing temps to drop into the lower 70s for most areas.
Some sheltered interior locations, mainly in the Lower Keys, will
cool off a bit more into the upper 60s to near 70 by morning, as
has already occurred at North Big Pine. Have made minor
adjustments to the gridded forecasts, but no updates are planned
for the zone forecast this evening.
Evening observations show benign conditions across the Keys
waters, with NE to SE winds of 10 kt or less prevailing. Similar
conditions are expected to continue through the rest of the night.
No significant changes are planned for the late evening forecast
VFR conditions will prevail overnight and Monday at the EYW and
MTH terminals. A brief episode of MVFR ceilings cannot be totally
ruled out during the late night and early morning hours, but the
probability is much too low to mention in the terminal forecasts.
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Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
719 PM EST Sun Feb 16 2020
Latest RAP model has a subtle short wave trough...with a weak
surface reflection...tracking across across the northern part of
the state tonight then exiting to the Atlantic Mon morning. During
Mon zonal aloft begin to return to the region while Atlantic high
pressure ridges westward...through FL to the Gulf of Mexico.
A swath of deep moisture...model PWAT values up to up 1.8 inches...
with the short wave trough/surface reflection sweeps across the
area over night with considerable cloudiness and patchy fog. This
system will support slight chance to likely showers but mainly
north of the I-4 corridor. These showers exit to the east early in
the day. The clouds and fog begin to lift and clear by mid-morning
although some cloudiness will linger.
17/00Z TAFs. Anticipate VFR clouds giving way to prevailing MVFR VSBY
and CIGS AFT 06-08Z and lifting/clearing by 15-17Z. LCL IFR VSBY and
CIGS PSBL 09-13Z mainly at inland and southern terminals where winds
are expected to become calm. Otherwise light and VRBL winds become
SE in the morning and SW for the afternoon. Afternoon SHRA which
hit some of the airports have exited to the east. Associated SHRA
with system moving by to the north overnight is expected to stay
north of terminals.
High pressure building across the waters will result in east and
southeast winds...but with an onshore shift near the coast in the
afternoons...through midweek. A front moves through the eastern Gulf
toward the end of the week with high pressure behind it...increasing
winds to 15 to 20 knots.
.Preliminary Point Temps/PoPs...
TPA 65 79 67 82 / 20 10 0 0
FMY 66 84 67 85 / 20 10 0 0
GIF 64 83 65 86 / 40 20 0 10
SRQ 65 81 66 82 / 20 10 0 0
BKV 61 82 63 84 / 40 10 0 0
SPG 66 80 67 79 / 20 10 0 0
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
856 PM MST Sun Feb 16 2020
Issued at 847 PM MST Sun Feb 16 2020
03z surface analysis had broad low across east central WY into
south central SD with weak cold front behind it into western WY.
Water vapour showed well-defined shortwave zipping through eastern
ID/southwest MT. Activity looks bumpy on satellite with KRIW/KTFX
soundings showing steep lapse rates from 800-500mb. Lightning
strike detected over eastern ID a bit ago. 00z KUNR sounding
showed a lot of dry air, which will impede initial lift ahead of
Late afternoon RAP was a bit concerning with a further north
depiction of accumulating snowfall, but after ingesting 00z
sounding data, latest runs keep pushing main snowfall southwest,
inline with current forecast across northeast WY into southwest
SD where best synoptic lift combines with 850-700mb frontogenesis.
Wild card for tomorrow afternoon will be combination of steep
lapse rates and downstream convergent flow over far southwest SD.
Might be a band of several inches of snow, but temperatures in the
30s may keep impacts low.
Current forecast updated a couple of times to reflect latest
trends and current thinking.
.DISCUSSION...(This Evening Through Sunday)
Issued at 149 PM MST Sun Feb 16 2020
General WNW flow will persist through the week. Shortwave
traversing the northern Rockies will advect ESE tonight into
Monday and support light snow over the SW third. Best overlap of
forcing and FGEN will occur over far SW Campbell county and south
with 2-3 inches possible there, and lesser amounts of an inch or 2
expected mainly from the Black Hills and SW through Monday
morning. Precip will then become more convective in the afternoon
as FGEN wanes and diurnal heating interacts with a weak cold pool
aloft. This will support snow shower activity over NE WY and the
Black Hills, with more persistent snow expected over the southern
Black Hills and SE onto the plains where NW flow will support eddy
convergence. An inch or 2 of snow will be possible if and where
this band develops. However, with highs expected in the 30s,
accums will be limited mainly to grassy sfcs, with limited road
impacts, esp on the plains. Arctic front will begin to settle
into the region Tues morning, with temps likely falling over
northern areas through the day. The speed of the front will
dictate how high temps rise in the southern half, with cooler
highs certainly possible. Expected FGEN band along the arctic
front may result in a high qpf low pop event with an inch or 2 of
snow possible along and just behind the front. This is esp the
case in the Black Hills (esp along the eastern slopes) where ENE
flow will enhance snow production in the afternoon and evening.
Have increased pops/qpf there for this. Arctic high will settle
south with cold temps expected Wed morning. Arctic airmass will be
short lived as dry conds with a warming trend can be expected the
remainder of the week, with much warmer conds expected by next
weekend as shortwave ridging occurs ahead of a digging eastern Pac
.AVIATION...(For the 00Z TAFS Through 00Z Monday Evening)
Issued At 417 PM MST Sun Feb 16 2020
Light snow will develop across northeast WY this evening and
spread into southwest SD overnight persisting Monday, although the
snow will become more showery in the afternoon. Expect MVFR/IFR
conditions with the snow. The SD plains north/east of the Black
Hills will see snow, but MVFR/IFR stratus/fog will develop
overnight into Monday.