Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/30/17
See below for an aviation forecast discussion for the 00Z TAFs.
.SHORT TERM...(This Evening through Thursday Afternoon)
Issued at 319 PM CST Wed Nov 29 2017
Winds continue to be the main story this afternoon, along with the
fire danger. The strongest winds are currently in the Coteau region
where gusts earlier this afternoon were in excess of 60 mph.
Conditions seem to have relaxed slightly, but still solid Wind
Advisory criteria across the east. This section of advisory is set
to expire at 22Z, and will evaluate at that time for possible
expansion for a couple hours, or just let it expire. It does appear
things are on a slow downward trend. Further west in the post-
frontal air mass, winds are creeping up again - mainly over western
SD and into ND. Corson/Dewey counties are seeing some rather gusty
winds so plan for now is to leave the Wind Advisory in place through
01Z. Will have to keep an eye on possible expansion into central SD
based on upstream obs and latest guidance. May need to make some
hazard adjustments yet in the next hour or so.
In regards to fire headlines, will leave the eastern Red Flag
warning in place through its scheduled expiration time. Winds are
plenty strong enough with humidity in the 20 to 30 percent range.
For the western Red Flag warning, may need to cancel it during the
next hour as humidity has actually been rising a bit through the 30s
in the post-frontal air mass. Even though winds are strong, humidity
may be getting to the point where fire headlines are not warranted.
Conditions will be much quieter on Thursday, with dry conditions and
mild temperatures continuing. Surface high pressure will be moving
into the central plains. The high center is off to our south so
there is just enough gradient to keep a west to northwest breeze
going through the day, but certainly much lighter than what we saw
.LONG TERM...(Thursday Evening through Wednesday)
Issued at 319 PM CST Wed Nov 29 2017
Mostly dry and mild conditions will continue through the extended
period. Nearly zonal upper level flow will be in place Thursday
night through the early part of the weekend, then a broad shortwave
trough will slowly drift across the area Sunday night and Monday,
with a secondary lobe moving through late in the period.
At the surface, high pressure will be over the area Thursday night,
then the region will be under a more neutral type pattern until a
low pressure system tracks across the Northern Plains Sunday
afternoon and night. May see some light precipitation with this
Sunday night into Monday, but amounts will be minimal. A frontal
boundary looks to swing through on Tuesday, with just a few light
post frontal showers possible into the day Wednesday.
Mild temperatures will continue through about the first half of the
period, with highs in the 40s and 50s. Will then see a bit of a
cooling trend with highs in the 30s on Monday, and in the 20s and
30s Tuesday and Wednesday. Overnight lows in the 20s Thursday night
through Sunday night will then trend to lows in the teens Monday
night and Tuesday night.
.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 617 PM CST Wed Nov 29 2017
Expect good VFR to persist over the next 24 hours. Breezy to windy
west-northwest winds this evening will gradually diminish
SD...Wind Advisory until midnight CST /11 PM MST/ tonight for
MN...Wind Advisory until midnight CST tonight for MNZ039-046.
Area Forecast Discussion
National Weather Service Columbia SC
629 PM EST Wed Nov 29 2017
High pressure will prevail across the area through tonight. A
weak cold front will approach Thursday and move into the area
Thursday night. The front will stall and remain in the region
through Saturday. The front will move off the coast Saturday
night with high pressure moving into the area Sunday. A stronger
cold front will approach the region by the middle of next week.
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
High pressure and a dry atmosphere will maintain fair weather.
Dry air aloft, light winds, and some low level moisture/dewpoint
recovery may will allow areas of fog to develop. At this time,
guidance indicates better favorability over southern and
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY NIGHT/...
Cold front currently well west of the region is forecast to be
moving east of the Mississippi valley area during the day on
Thursday. Deeper moisture through the majority of the day will
remain limited, and expect any rainfall ahead of the approaching
front the be well west of the cwa through the afternoon hours.
Temperatures through the afternoon on Thursday will continue to
be above normal ahead of the front. By Thursday evening,
rainfall chances will be increasing from west to east, with the
best chance for rain occurring late Thursday night into Friday
morning. GFS seems to diminish the areal coverage of rainfall as
the system moves east of the mountains, while the ECMWF
indicates a little more widespread coverage. Still believe that
the chance pops that have been advertised the past few days
remain on track. QPF Amounts should be rather light. Models
still try to indicate some very light rainfall across the
southern portions of the cwa on the backside of the front on
Friday. Deep moisture will be exiting the area, and confidence
remains low in any lingering rains, so have only gone with
slight chance pops across the southern counties Friday.
Temperatures Friday still above normal for portions of the day
as the colder air lags slightly behind the front.
Models have trended drier for Saturday, and expect that it will
be cooler and drier as high pressure moves through the region.
Highs Saturday a good 10 degrees cooler than previous few days.
Saturday night will see a return of lows in the upper 30s to
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Dry high pressure dominates for Sunday and Monday. After that
period, longer range models showing a deepening eastern US
trough beginning to set up into the middle of the week and
beyond. This will drive a stronger and colder front towards the
area by the middle of next week. Current timing has the front
moving into the area late Tuesday into Wednesday, with an
increase in rainfall in advance of the front.
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
VFR conditions outside of possible fog development early
High pressure and a relatively dry air mass over the area this
evening. There is potential for radiation fog late tonight
although some mid level clouds may advect toward the area late
tonight associated with short wave trough limiting threat. Lack
of abundant low level moisture may also be a limiting factor
for fog. The latest HRRR model and Lamp guidance suggest
LIFR/IFR visibility/ceilings in the CSRA region including AGS
terminal...although DNL visibility may stay up. Will continue
MVFR at other terminals where confidence is lower. Stratus may
linger thru the mid morning with scattered/broken VFR cumulus in
the afternoon as low level moisture increases. There may be a
few light showers late in the day mainly CSRA. Winds light and
variable becoming west.
EXTENDED AVIATION OUTLOOK...Showers and associated restrictions
possible Thursday night into Saturday as a frontal system
crosses the region.
Area Forecast Discussion
National Weather Service Charleston SC
939 PM EST Wed Nov 29 2017
High pressure will prevail over the region through Thursday. A
cold front will move through late this week with generally dry
high pressure to follow through early next week.
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Late this evening: Model guidance including recent runs of the
HRRR and RAP have been much more aggressive with the coverage
and intensity of fog for late tonight. This seems to support the
fact that numerous observation sites have already started
reporting fog periodically. As such, have increased the coverage
in the forecast to "areas" of fog. Still not confident that
dense fog will be an issue so no mention has been added to the
Hazardous Weather Outlook as of yet.
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
Thursday: Mid-levels: Nearly zonal flow over the Southeast,
with winds generally from the west northwest. At the surface:
High pressure centered over New England in the morning will move
offshore. Meanwhile, weak high pressure in the lee of the
Southern Appalachians will gradually dissipate through the day.
A weak cold front will approach late at night. Moisture: The air
mass will start out dry. But moisture will increase ahead of
the front, with PWATs rising to ~1.25" late. We are forecasting
POPs to increase from west to east late at night as light
showers with the front begin moving through our area.
Temperatures: Well above normal during the day, continuing
through the night, especially as clouds increase/thicken.
Friday: Mid-levels: Semi-zonal flow over the Southeast, with winds
generally from the west northwest. At the surface: A cold front
located just to our west in the morning will slowly move through
during the day, dissipating during the evening and overnight hours.
Behind the front, high pressure will move towards the Northeastern
U.S. late, and stretch down the lee of the Appalachians. Moisture:
Despite the cold front, there is not much moisture in place. PWATs
may barely be ~1.25" early in the morning, declining during the day
as drier air tries to moves in from the west. POPs remain in the
slight chance category during the day due to the front and at night
due to remnant activity from the dissipating front. But it`s
possible the shower activity will be less at night than what we`re
currently forecasting. Total QPF will be minimal, generally a few
hundredths. Temperatures: Above normal.
Saturday: Mid-levels: Semi-zonal flow over the Southeast, with winds
generally from the west northwest. At the surface: An elongated area
of high pressure will be in lee of the Appalachians. Moisture:
Despite dew points in the 40s across the northern half of our
area, models indicate that an area of increased moisture (dew
points in the 50s) may remain over the southern half of our
area. Even with minimal lift, some light showers are possible
here and POPs are in the slight chance category. Total QPF will
be minimal, if anything. Temperatures: Northern half of the
area, a few degrees below normal. Southern half of the area,
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Dry high pressure will remain the dominant influencer of tangible
weather through early next week. Above normal temperatures are
anticipated through the period. A stronger cold front could affect
the region mid-next-week.
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
The main forecast issue for overnight will be the fog potential.
Recent runs of the hi-res HRRR and RAP models have shown an
increase in the coverage and intensity of fog, and area
observations have started to report fog. So, confidence is
increasing that it will impact the terminals. Will amend both to
feature an earlier start time for the fog and will add a TEMPO
for a period of IFR conditions at KCHS. Beyond that, there are
Extended Aviation Outlook: Periods of flight restrictions
possible due to a front Friday, then it`s remnants Saturday.
Tonight: Northeast winds will persist with winds 10 kt or less.
Seas will average 2-4 ft.
Thursday through Tuesday: High pressure will prevail over the region
Thursday. A cold front will move through late this week with
generally dry high pressure to follow through early next week. No
hazardous marine conditions are expected.
Astronomical factors will increase tide levels this weekend into
next week. Elevated winds behind a passing cold front mid-next-week
could additionally enhance water levels, creating a possibility for
minor coastal flooding around the times of high tide, primarily
along the South Carolina coast.
Area Forecast Discussion
National Weather Service Jacksonville FL
935 PM EST Wed Nov 29 2017
Weak high pressure ridge is north of the area with broad low level
trough off the Atlantic coast. Generally light north to northeast
flow around 5-10 mph is noted along the coastal zones. Light to near
calm winds inland at this time. Weak mid to upper level ridge is
noted across nrn FL and portions of GA...which is forecast to move
southward through Thursday.
Mostly clear skies expected most of the night though may see thin
high clouds move in toward early morning. The main issue tonight is
the fog potential and given temps expected to be cooler than last
night...the fog chances appear to be higher than last night. The
main hindrance for at least some parts of the area is boundary layer
mixing...but this is probably going to be short-lived as a
moderately strong low level inversion forms per RAP soundings. The
primary updates to the current forecast were to lower min temps a
bit and to delay the onset of fog patchy to areas of fog. Also put
in a few showers for the offshore waters where a weak convergent
line continues. Best estimate of where more persistent dense fog
forms is from Clay and Bradford counties northward through Jax and
Callahan through Woodbine and to around Brunswick.
.AVIATION...We continue to forecast restrictions due to stratus
and fog late tonight and have not changed prior forecast of IFR
developing. Due to model discrepancies have not gone below IFR
conditions but highest chances of seeing LIFR/VLIFR seem to be at
JAX, VQQ, and SSI. Fog and stratus expected to erode through mid-
morning Thursday trailed by prevailing VFR conditions under light NE
.MARINE...No significant changes to the current marine forecast.
Winds will be north to northeast around 10-15 knots and then slowly
decreasing overnight. Sea forecast may be a bit lower for this
.PRELIMINARY POINT TEMPS/POPS...
AMG 51 78 53 74 / 0 0 10 10
SSI 57 72 56 72 / 0 0 10 10
JAX 54 77 53 75 / 0 0 10 10
SGJ 60 73 56 74 / 0 0 0 0
GNV 54 78 52 77 / 0 0 0 0
OCF 56 80 53 78 / 0 0 0 0
...Updated Forecast Discussion...
Issued at 832 PM EST Wed Nov 29 2017
No significant changes needed for the overnight period as weak mid
level wave passes overhead. Increasing clouds and weak warm air
advection should keep lows in the 40s.
Looking at the latest hi-res models for tomorrow, did adjust the
timing for precipitation onset across the area. HRRR and RAP coming
in a couple hours slower, especially for areas along/east of I-65.
Overall the message for scattered showers with light rainfall
amounts is on track.
.Short Term...(This evening through Thursday night)
Issued at 250 PM EST Wed Nov 29 2017
Weak front is now quasi-stationary across central Kentucky, as the
high center is already scooting farther east and winds have shifted
to the ESE ahead of the next system moving into the mid-Mississippi
Valley. The more significant player is a sharper northern stream
wave moving into the Upper Midwest this afternoon.
Weaker southern stream wave will quickly push into the Appalachians
tonight without much fanfare, but leave just enough mid-level
moisture in place for the northern stream disturbance as it moves
into the Great Lakes on Thursday. Scattered to numerous showers will
be characterized by high-end chance or low-end likely POPs and low
QPF, and temps will only be a few degrees cooler than today with
increased cloud cover but not much change in air mass.
.Long Term...(Friday through Wednesday)
Issued at 255 PM EST Wed Nov 29 2017
...Pattern Change Coming Early Next Week...
Pattern remains fairly progressive through the weekend, resulting in
mild and dry conditions Friday through Sunday. Toward the end of the
weekend, the pattern starts to amplify with ridging on the East
Coast and trofiness in the Rockies.
POPs will ramp up on Monday as southerly flow deepens and draws more
moisture into the Ohio Valley. Best rain chances appear to be Monday
night into early Tuesday as a deepening surface low lifts NE from
the Plains to Lake Superior, driving a cold front through the Ohio
Valley. Forecast confidence diminishes Tuesday-Wednesday as models
diverge on how the front will continue to progress into the Deep
South. Precip timing becomes iffy at best, but what we can hang our
hat on is strong cold advection on the backside of this system, and
temps solidly below normal by Wednesday.
.Aviation...(00Z TAF Issuance)
Issued at 617 PM EST Wed Nov 29 2017
Plan on increasing and lowering ceilings late tonight ahead of a
cold front that will bring scattered showers to southern Indiana and
central Kentucky starting around daybreak. Ceilings should drop down
below fuel alternate levels by mid/late morning into the afternoon
hours, especially at HNB, SDF, and LEX. Winds will be southwesterly
ahead of the front then become westerly to northwesterly late in the
period once the front passes. Showers and lower ceilings should end
late in the period or Thursday evening.
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
826 PM CST Wed Nov 29 2017
826 PM CST
Overall, going forecast looks to be in good shape with just some
cosmetic changes made to the grids tonight. Some large patches of
mid level cloudiness moving across the region have been playing
havoc with temperatures and hourly temps will likely fluctuate as
depending on state of the sky (drop when clear, rebound when
cloudy). Over time, cloudiness will become more the rule as large
scale ascent ahead of approaching trough overspreads the area and
encounters narrow corridor of higher moisture content. Once clouds
lock in, temps will hold more steady. Short range guidance
continues to suggest some rain will break out in advance of the
front over mainly the east 1/4 of our CWA
137 PM CST
Several features of note, but there are no significant impacts in
the near term.
A compact upper low across southern Illinois will spread into the
Ohio valley tonight, while a secondary trough axis across the
northern Plains will cross the eastern Great Lakes later tonight.
Warm advection on the northern end of the low to our south and
ahead of the approaching northern stream trough will lead to an
expansion and lowering of clouds later this evening and tonight.
The atmosphere is pretty dry in the lower levels, especially
across NW/NC Illinois. While the upper forcing is not superb, RAP
cross sections depict some omega above a mid level baroclinic
zone for a brief window later tonight to support some sprinkles or
even some light rain showers. The cloud deck will also not be too
high and a modest increase in PWATs will occur ahead of the
front. The better chances will occur as the front makes progress
Significant mid level drying will occur behind the cold front
late tonight such that precipitation chances and sky cover will
decrease quickly Thursday morning. 950-925 mb temperatures do not
change much behind this front. Since this is roughly the mixing
height this time of year, temperatures on Thursday under mostly
sunny skies will lead to similar highs in the upper 40s to low
50s. It may feel a tad cooler with a breezy northwest wind.
308 PM CST
Thursday night through Wednesday...
The main concerns are with periods of rain/showers potential
Sunday night through Monday night with a possibly stronger
synoptic system and then a major pattern change to much colder
weather next week.
To kick off meteorological winter, December will start out
decidedly un-winter like, as the area will temporarily remain in
the mild pattern we`ve been in of late. After a relatively chilly
Thursday night-Friday morning behind the cold front passage late
tonight/early Thursday, the Pacific origin air mass will modify
quickly. Expecting highs in the mid-upper 40s Friday, upper 40s-
low 50s Saturday and lower-mid 50s Sunday, compared to normal
highs for the first few days of December in the upper 30s-low 40s.
Clouds and southerly winds will increase on Sunday afternoon into
early Sunday evening in advance of surface low pressure over the
central and northern Plains. Confidence remains on the lower side
regarding the evolution, track and intensity of this surface low
into Monday. However, conceptually, there is decent agreement in
the area being firmly on the warm side, and periods of
rain/showers late Sunday evening into late Monday. The coverage
and duration of the rain will be dictated by the track and
intensity of the surface low, which still varies on the guidance,
with recent runs of the ECMWF on the stronger side. In the strong
warm advection pattern, will need to watch for elevated
instability and at least embedded thunder potential, though have
not yet made thunder mention in the grids. High temperatures will
likely be well into the 50s on Monday.
Upstream mid and upper level changes heralding the major pattern
shift to colder will be taking place on Monday. Namely, a highly
amplified blocking ridge of high pressure will take shape along
the Pacific NOAM coast up to Alaska, along with strong blocking
developing over the Arctic region. These teleconnection patterns
are known as a positive Pacific North American pattern (+PNA) and
negative East Pacific Oscillation pattern (-EPO) for the Pacific
based blocking ridge and negative Arctic Oscillation (-AO) for the
Arctic blocking. These three features occurring in concert are
quite favorable for to below to much below normal temperatures
across the region, which will be the big story by Tuesday or
Wednesday and continuing likely well beyond day 7.
A stronger storm system Monday-Monday night will serve to speed up
the arrival of the cold air mass, with which there remains
uncertainty as described earlier. When the very deep downstream
trough (piece of the PV) fully drops south over the area in the
mid to late work week in response to the upstream blocking, the
pattern will be more favored for possible clipper type systems and
of course lake effect snow off to the east. However, overall the
extent of any snow potential outside of lake effect is low
confidence. Given strong and unanimous ensemble agreement in the
pattern change over the last several days and no signs of a
weakening of the signal, confidence is high in the turn to much
colder temperatures. Day to day details with temperatures are
lower confidence, but the bottom line is be ready for an abrupt
change from the mild weather. Very cold to even bitterly cold
temperatures and wind chills are possible at times mid to late
next week and beyond.
For the 00Z TAFs...
VFR conditions expected through the period. A cold front will move
across the terminals overnight with VFR cigs expected and a chance
of some light rain or sprinkles during the pre-dawn hours. In the
wake of the cold front look for winds to swings around to west to
west northwest early Thursday morning. Skies will clear Thursday
morning and the sunshine will help promote decent mixing allowing
for winds to become gusty by late morning through late afternoon,
with some gusts around 20kt likely.
336 PM CST
Once high pressure shifts away from the eastern Great Lakes this
evening, winds that will have shifted to southerly over the entire
lake will then increase substantially out of the south-southwest
later this evening and tonight. This will be in response to
another quick eastward moving area of low pressure over western
Ontario. Gales to 35 kt will be likely over the northern half of
the lake after 11pm tonight through mid to late morning on
Thursday, for which a Gale Warning remains in effect.
Surface high pressure will shift across the Mid-Mississippi
Valley and the Ohio Valley later in the week following a cold
frontal passage on Thursday morning. As this occurs, expect
brisk west-northwesterly winds in the wake of Thursday morning`s
frontal passage to ease and back southwesterly by Friday. It
appears that the weather pattern across the region will become
more active into next week, and this is likely to result in
additional periods of strong winds over the lake. The first period
of interest is Friday night into Saturday, when southwesterly
winds up to 30 kt are likely on the northern portion of the lake.
Sunday night through Monday is the next period of interest, with
strong southerly winds likely due to stronger low pressure passing
west and north of the lake.
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Area Forecast Discussion
National Weather Service Nashville TN
840 PM CST Wed Nov 29 2017
FOR EVENING DISCUSSION.
A weak surface front is situated to our west this evening, even as
the 00Z sounding gives us a stable and relatively dry profile.
Scattered echoes showing up to our south are likely not reaching
the ground, or at least very little, although dew points in these
areas have risen considerably, so at least evaporation below the
cloud bases is helping to moisten up the low levels there. HRRR
shows random, light echoes moving across Middle Tennessee the rest
of tonight and tomorrow as the front makes its way through the mid
state. Given the dearth of deep antecedent moisture and weak
dynamics, this just isn`t going to be a significant rain event. In
the meantime, hourly grids are holding up well. Will probably
issue a forecast update later this evening to update the wording,
but no significant changes are planned at this time.
00Z TAF DISCUSSION.
A cold front will approach Middle TN Thursday morning bringing a
shot at some light rain and MVFR cigs. Lower cigs should begin to
move in after 13Z and spread across the mid-state, reaching KCSV
by 17Z. Will cover the rain with VCSH for now and try to narrow
times with the 06Z issuance.
Winds will be light throughout, with a wind shift to the northwest
occurring during the late morning hours on Thursday.