Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/09/18
Area Forecast Discussion
National Weather Service La Crosse WI
545 PM CST Sat Dec 8 2018
.SHORT TERM...(Tonight through Sunday Night)
Issued at 143 PM CST Sat Dec 8 2018
Another day of stratus across the area with temperatures sitting in
the teens to middle 20s. Loop of GOES Visible however, does show
this stratus thinning out some with the ground showing up beneath
it. In addition, loop was showing showing a slow northeast push of
the clouds. If this continues, and RAP 0.5-1km RH trends work out,
we will see some clearing this evening, given influx of drier Plains
air on southwest winds of 10-15mph in that layer. We will then be
watching a mid-level focus/closed low dropping south from the
Northern Plains tonight into the Central Plains. Some cirrus from
this feature looks to push through the area but should end up
mostly clear/mostly sunny tonight into Sunday. Otherwise, plan on
lows tonight in the lower/middle teens and highs Sunday in the upper
20s to lower 30s. Mid-level ridge of high pressure builds back
into the area as that closed low continue to sink southward away from
the area. Continued mostly clear Sunday night with drier west-
southwesterly flow. Look for lows again in the teens.
.LONG TERM...(Monday through Saturday)
Issued at 143 PM CST Sat Dec 8 2018
A mid-level trough/weak surface low passes just to our north Monday.
Other than a few higher level clouds, skies should remain mostly
sunny with highs topping off n the 25-30 degree range.
Strong mid-level ridging on Tuesday will keep the area dry Tuesday
with some increasing high clouds ahead of an approaching trough over
the Northern Plains. Highs are expected to be in the middle 20s to
the lower 30s.
A chance of light snow or rain/snow mix moves in Wednesday as that
Northern plains trough makes its way across the area. Plan on highs
in the 30s.
Another trough rolls across the region Thursday, keeping a chance
of light snow or rain/snow mix in the forecast. Otherwise, look for
highs again in the 30s.
Although ECMWF and GFS are in fairly good agreement in keeping a
strong low and associated precipitation well south and east of the
area Friday, The GEM keeps the system tied with northern stream
energy and spread precipitation well into our area. Will hold onto
30-40 pops for now and let models decipher with later runs.
GFS and ECMWF build a ridge into the area on Saturday while the GEM
keeps closed low overhead with light snow. Will keep a low-end pop
and again, let models work this out with time.
Otherwise, temperatures look to be right around normal or even a
couple degrees above Friday and Saturday with highs in the upper 20s
to middle 30s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 545 PM CST Sat Dec 8 2018
Satellite imagery late this afternoon is finally providing some
hope that the low clouds may clear out of the area. The clouds are
caught in the low level southwest flow between the back side of
the ridge that was just east of the area and the area of low
pressure dropping south across the Dakotas. The clouds are
progressing to the northeast and expect this trend will continue
through the night, although most likely at a slower pace that
previously expected and will hold the MVFR ceilings for most of
the evening at both airports. Once the low clouds move out, some
concern for fog development. The visibilities are currently in the
5 to 9 mile range already but hoping the light south winds will
create enough mixing to keep any fog from forming. Also, not
really seeing a signal in any of the short term meso-scale models
for widespread fog formation overnight.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...DAS
LONG TERM...DAS
AVIATION...04
Area Forecast Discussion
National Weather Service Charleston SC
951 PM EST Sat Dec 8 2018
...HEAVY RAINFALL AND TIDES REACHING NEAR MAJOR FLOODING
THRESHOLDS IN CHARLESTON HARBOR COULD PRODUCE WIDESPREAD
FLOODING IN DOWNTOWN CHARLESTON SUNDAY MORNING...
.SYNOPSIS...
A strong low pressure system will move through the area tonight
through Sunday. High pressure will gradually build in from the
west early next week. A cold front may approach the region by
the end of the work week or into early next weekend.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
No additional changes were made from the early evening update
other than some minor grid tweaks.
A highly complex surface pattern is in place this evening
featuring strengthening cold air damming inland, a sharping
coastal front offshore and low pressure located near the mouth
of the Mississippi River at 08/23z. The low is forecast to track
just inland along the northern Gulf of Mexico coast tonight and
along the Georgia and South Carolina coasts Sunday morning. AS
the low approaches, widespread precipitation will develop across
the Southeast U.S. featuring heavy snows across western North
Carolina, northeast Georgia and the South Carolina Upstate with
moderate to heavy rainfall across the remainder of the region. A
variety of sensible weather and hazards will impact Southeast
South Carolina and Southeast Georgia tonight as the low draws
closer. Details on these specific hazards are found below:
Temperatures: The onset of diabatic cooling within the wedge has
accelerated temperature falls more than expected this evening.
The latest RAP wet-bulb progs suggest temperatures really only
have a few more degrees to cool before leveling out, so opted
only nudge lows down a few degrees. As the low approaches, it
appears the low will track close enough to the far southern and
coastal zones to draw warmer air in from off the Atlantic, even
as the inland wedge hold tight. It was decided to introduce
some rising temperatures during the early morning hours, but not
quite as warm as the RAP and H3R consensus would suggest. This
will have to be watched as this warmer trend has been a
consistent signal in a number of the HREF members.
Rain: The lower troposphere is steadily moistening this evening
as light rain continues to develop. Most stations are reporting
light rain with vsbys >6 miles, but are still measuring several
hundredths. Rain intensity is expected to increase after
midnight as low-level convergence intensifies across the coastal
counties as multi-layer moisture transport and isentropic
assent intensify atop the CAD region. The rain will likely
become locally heavy at times right ahead of the surface low, so
a "rain heavy at times" qualifier has been been introduced into
the weather grids. There is some concern that hourly rainfall
rates could become high enough as high tide approaches to create
some flooding concerns, but opted to hold off on a Flash Flood
Watch at this time.
Wind: Early evening observations show winds are already gusting
35 mph along the coast from roughly Edisto beach northward. High
resolution guidance with support from both the NAM and GFS show
a nasty wind maximum working up along the Charleston County
coast overnight into the mid-morning Sunday ahead of the surface
low. This should support winds of 20-30 mph with gusts to 40-45
mph across Charleston County and into the Edisto Beach area. A
Wind Advisory has therefore been issued with the greatest
impacts expected to occur across the beach communities between
McClellanville and Edisto Beach, including areas around the
Charleston Harbor. The elevated bridges around Charleston Metro
will also be exposed to these winds. For Lake Moultrie,
northeast winds 15-20 kt with gusts 25 kt will persist and a
Lake Wind Advisory remains posted there.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Sunday and Sunday night: a vigorous surface low pressure system is
shown by all models to be near or just off the GA coast by 12z
Sunday, then move rapidly northeast away from the area Sunday
afternoon. The day should start with widespread rain, possibly heavy
at times, then tapering off during the afternoon. Given the rain,
cloud cover and cold advection behind the storm during the
afternoon, temperatures are not expected to climb much from the
morning, only reaching the lower to mid 40s inland to the lower to
mid 50s near the coast. Still expect storm total rainfall to be 1 to
3 inches, with lower amounts possibly over the southeast GA zones.
Depending on how heavy the rainfall comes down, there could be some
localized ponding/flooding of low lying areas and roads, especially
Sunday Morning. Breezy northeast winds in the morning are expected
to back to northwest and decrease some during the afternoon as the
storm pulls away to the northeast. By Sunday night, the surface low
moves well to the northeast, but at upper levels, a broad upper
trough and associated moisture stick around, especially over the
northern half of the region. Therefore, have kept chance PoPs over
the north and slight chance to low end chance well to the south
through the night. Lows by morning in the mid 30s, except around 40
closer to the coast.
Monday and Monday night: A broad upper trough and some moisture
remain over the area. This will keep conditions unstable enough to
warrant mention chance of light showers through the period, tapering
off Monday night. Highs will be quite cool, only in the lower to mid
40s most areas with mostly cloudy/cloudy skies. Clouds should
gradually diminish through the night as the upper trough moves east
with lows cold in the lower to mid 30s.
Tuesday: The upper trough looks to finally move east of the region
with deep layer ridging building from the west. Expect skies to
clear, with temperatures topping out in the lower to mid 50s, which
is still about 10 degrees below seasonal normals.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Any lingering precipitation should end by daybreak Wednesday
after the secondary shortwave moves offshore. Temperatures will
moderate mid to late week as surface high pressure moves east. A
cold front is expected to bring another round of rain to the
area Friday and Friday night, followed by cooler high pressure.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
IFR cigs will quickly overspread the terminals this evening as
light rain blossoms over the region. Rain intensity will
steadily ramp up overnight with periods of heavy rainfall likely
setting up at both KCHS and KSAV after 09z as low pressure
approaches from the southwest. Steadier rains will end from
southwest to northeast Sunday morning as low pressure pulls
away. Gusty winds near 25 kt will continue for much of the
period.
Extended Aviation Outlook:
Sunday: Still expect MVFR to possibly periods of IFR conditions
possible, which is also coincident with the timeframe for
widespread rainfall, possibly heavy at times. Also, gusty
northeast winds, backing to northwest later in the day.
Sunday night through Monday night: MVFR ceilings will be possible as
the area remains an upper level trough with the threat for scattered
showers.
Tuesday and Wednesday: Conditions expected to improve to VFR as deep
layer ridging moves over the area from the west.
&&
.MARINE...
Buoy and pilot boat reports indicate gales have spread south
across the entire local marine area and Gale Warnings have been
expanded south to include the two Georgia marine zones. The
Charleston Harbor Pilot boat recently reported NE winds 30-35 kt
with seas 7 ft about 12 miles east of the Charleston Harbor
entrance.
High surf: Seas across the Charleston County waters are expected
to build into the 7-10 ft range late tonight into Sunday morning.
This could produce 3-5 ft breakers along the Charleston County
coast during this time and a High Surf Advisory could be needed.
Sunday: Models continue to show a strong northeast gradient, which
is expected to produce marginal gale conditions over the Charleston
coastal waters, where a gale warning remains in effect. There could
be marginal/short lived Gale conditions, especially within gusts,
near the mouth of Charleston Harbor, but to marginal to go with a
Gale Warning at this time. Otherwise, solid Small Craft conditions
all other areas through the day.
Sunday night: the surface low continues to pull away, with a gradual
weakening of winds, but still 15 to 20 knots from the northwest,
with higher gusts. Seas may force a Small Craft Advisory to remain
posted for outer waters beyond 15 nm in SC and the offshore GA
waters.
Monday and Tuesday: High pressure gradually builds from the west,
but north-northwest winds remain in the 15 to 20 knot range. Again,
with offshore flow, seas could linger around 6 ft beyond 15 nm
offshore, which may require the issuance of an extended Small Craft
Advisory for marginally high seas.
Tuesday night through Thursday: High pressure slowly builds over the
area with decreasing winds/seas below highlight levels.
&&
.HYDROLOGY...
Rainfall totals of 1-2" across southeast Georgia and 2-3" over
southern South Carolina are expected through Sunday. Rainfall
rates will probably not be high enough to cause significant
flash flooding. However, there is concern that moderate to
potentially heavy rain will occur around the Sunday morning high
tide, which could exacerbate existing saltwater flooding along
coastal locations, particularly in Southeast South Carolina.
Longer term, we expect additional rivers to rise above flood
stage and ongoing flooding to worsen.
&&
.TIDES/COASTAL FLOODING...
The latest tidal predictions have come down slightly since the
12z run and tides are now expected to peak at 7.9 ft MLLW or
about 0.1 ft below major flood thresholds. It is very possible
the latest run is underestimating the degree of gales along the
Charleston County coast, which may eventually push tides above
8.0 ft MLLW. However, confidence is not high enough to justify
an upgrade of the Coastal Flood Watch to a Coastal Flood Warning
at this time. The final call will be made by the incoming
overnight shift. The combination of moderate to locally heavy
rainfall and high tides on the high-end of the moderate flood
range could still a yield a fairly nasty situation in Downtown
Charleston tomorrow morning.
Guidance has also been indicating the tides could reach marginal
Coastal Flood Advisory during the Monday morning high tide, but too
marginal to get too specific at this time. Stay tuned for the
potential for additional Coastal Flood Advisory issuances.
&&
.CLIMATE...
Rainfall records for 9 December:
KCHS: 0.64/1948
KCXM: 0.99/1948
KSAV: 2.44/1885
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Lake Wind Advisory until 11 AM EST Sunday for SCZ045.
Wind Advisory until noon EST Sunday for SCZ049-050.
Coastal Flood Watch from 6 AM EST Sunday through Sunday
morning for SCZ049-050.
MARINE...Gale Warning until 8 AM EST Sunday for AMZ352.
Gale Warning until 7 PM EST Sunday for AMZ350.
Gale Warning until 5 AM EST Sunday for AMZ354-374.
Gale Warning until noon EST Sunday for AMZ330.
&&
$$
ST
Area Forecast Discussion
National Weather Service Duluth MN
943 PM CST Sat Dec 8 2018
.SHORT TERM...(This evening through Sunday)
Issued at 255 PM CST Sat Dec 8 2018
High pressure was centered near southern Michigan with a ridge
extending well northwest into the Wisconsin and Minnesota this
afternoon. Despite a dry air mass and the high, stratus was moving
north through the Northland. Much of the guidance was doing a poor
job depicting this cloud but we leaned toward the RAP although
adjusted timing to bring the cloud in faster. Fog will occur as well
and we added that into Sunday. Temperatures will be quite variable
tonight with any areas that take longer to cloud over or that
develop breaks will be much colder. We have lows from 10 to 15 but
will have to adjust based on short term satellite trends. There was
a back edge to the stratus over southern Minnesota but we expect
that to slow tonight, perhaps working into southern parts of our
area overnight. The stratus was at least partially driven by warm
air advection. The warm air advection will bring in 850mb
temperatures from 0 to 2C by Sunday afternoon and will serve to
further strengthen the inversion. We do decrease cloud cover through
the day Sunday but confidence is not very high, especially over much
of northern Minnesota. We have highs in the upper teens to mid
twenties.
.LONG TERM...(Sunday night through Saturday)
Issued at 255 PM CST Sat Dec 8 2018
The period will feature high temperatures near or a few degrees
above normal and a few opportunities for light snow.
A few shortwaves will move through the region from Tuesday night
through Friday bringing chances for light snow with minimal
accumulation. The shortwave Tuesday night/Wednesday will be weak
with little significant moisture and we have low POPs and not even
in all areas. A stronger shortwave will arrive Thursday and depart
Friday but again we only expect light snow amounts. An upper level
ridge will build in later Friday and remain over the region into
Saturday.
High temperatures will be near or a few degrees above normal and
overnight lows are expected to be quite a bit above normal Tuesday
night through Friday night.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 532 PM CST Sat Dec 8 2018
Large area of IFR stratus under strong inversion will linger
through the night while advecting around. Could not see a reason
to improve any site to VFR before morning. Models not handling the
stratus very well, so a lower confidence forecast particularly on
timing of flight cats.
&&
.MARINE...
Issued at 939 PM CST Sat Dec 8 2018
West to southwest winds will continue overnight as a sharp
pressure gradient noses into the region. Expanded the Small Craft
Advisory to all zones except the far western Lake Superior zones.
The wind will slowly decrease Sunday from west to east but it
will take the waves a bit longer to diminish.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 14 23 13 26 / 0 0 0 0
INL 10 21 8 25 / 0 0 0 0
BRD 13 24 11 29 / 0 0 0 0
HYR 14 26 12 26 / 0 0 0 0
ASX 15 27 16 29 / 0 0 0 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory until 4 PM CST Sunday for LSZ121-146>148.
Small Craft Advisory until 10 AM CST Sunday for LSZ140>143.
&&
$$
SHORT TERM...Melde
LONG TERM...Melde
AVIATION...Wolfe
MARINE...Wolfe
Area Forecast Discussion
National Weather Service Hastings NE
514 PM CST Sat Dec 8 2018
.SHORT TERM...(This evening through Sunday)
Issued at 340 PM CST Sat Dec 8 2018
No major concerns in the short term as dry conditions continue.
Water vapor and upper air analysis indicates a fairly
complex/convoluted upper pattern with several disturbances of
note. The largest/most impactful disturbance is located across the
S. Plains and will shift E well away from our area. Another
potent/compact vort max was located over the N. Plains. Finally, a
third (weaker) disturbance was located over the Intermountain
West near SLC.
The latter two disturbances will combine to carve out a new
trough over the Central Plains tonight and into Sun, but the
impact to sensible wx will be limited due to meager moisture left
behind the initial S. Plains system. The main impact to local wx
will be a wind shift tonight, though some models are showing fog
potential as well. The NAM (and associated hi-res NAMNest, ARW,
and NMM) along w/ SREF are most aggressive with fog development,
though feel this is overdone. There is only limited support from
the HRRR, RAP and MET/MAV guidance and relegated to mainly the far
W CWA. Will insert patchy fog per coordination w/ neighbors to
W/SW, but feel the veering winds at 4-8kt will be enough to
preclude repeat of last night.
For Sunday, no big changes to the forecast. Increased cld cover
in morning to account for high level cloudiness associated with
disturbance pinwheeling S across the CWA. The system is actually
fairly strong in the upper levels, but as mentioned above,
moisture is extremely lacking in the low-mid levels. Thus, no
precipitation is expected. Models tweaked high temps up a bit for
Sun aftn, which is plausible given deep W/WNW downsloping flow in
low-mid levels, but didn`t go drastically higher given some high
cloudiness and modest CAA to help offset downsloping effects.
.LONG TERM...(Sunday night through Saturday)
Issued at 340 PM CST Sat Dec 8 2018
The main story for the extended will be a modest, gradual warmup
through midweek then the POTENTIAL for a system & wintry
precipitation mid-late next week.
We`ll start off the week on a quiet note as un upper level trough
initially over the Central Plains Sun night quickly opens up and
shifts E to the SE CONUS Mon AM. In its wake, we`ll see shortwave
ridging/subtle height rises Mon PM into Tue. Highs Mon will range
from low 30s to low 40s. Temps warm some for Tue with highs mid
30s to upper 40s. Warmest readings both days will favor areas with
little to no snow cover (S and SE CWA). However, these readings
along with periods of sunshine should be enough to erode some of
the snow cover we still have.
A weak, open and moisture starved northern stream system will
quickly move W to E across the Central/N. Plains Tue night into
Wed. Pcpn chcs remain very low with this system and since it is of
Pacific origin, there is not a lot of cold air either. In fact,
there is little change in temps from Tue into Wed.
The forecast becomes a little more interesting for the second
half of next week. While all models show at least some sort of
disturbance passing thru late Wed night thru Thu night, there are
considerable differences amongst the models in terms of strength,
track and timing. The GFS is the fastest/weakest solution
(glancing lgt pcpn S/SE CWA), and the latest Canadian run is by
far the strongest/slowest/furthest N solution (shows significant
pcpn for much of CWA). The EC is somewhat in the middle of the
road in terms of timing and eventually strengthens system
similarly to Canadian, but it is much further S (mainly dry for
CWA). Neither the GFS or EC presents much potential for pcpn for
CWA, so the Canadian is clear outlier. After extensive
coordination with other NWS offices across the region, felt it was
prudent to cap POPs around 50 percent on Thu, then go with a dry
forecast Thu night thru Fri night despite the blend (which takes
Canadian model into account) giving extensive 30-50 POPs that
entire time frame. Plenty of time to work out details, obviously,
but wanted to avoid painting entire time frame with POPs when
really only one run of one model was showing that sort of
potential.
Otherwise, temps should be near to slightly below normal for the
latter portions of next week.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday)
Issued at 508 PM CST Sat Dec 8 2018
VFR conditions are expected through this TAF period.
There is an outside chance for some patchy fog to develop
tonight, although short-term models models continue to show the
best potential west of the terminals. Therefore, I don`t foresee
any impact at this time. Any fog that does develop in the vicinity
will also be short- lived as winds become westerly to
northwesterly by sunrise on Sunday.
Otherwise just expect scattered high clouds tonight into Sunday
morning.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
SHORT TERM...Thies
LONG TERM...Thies
AVIATION...Mangels
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
957 PM EST Sat Dec 8 2018
.SYNOPSIS...
With cold Canadian high pressure to our north and low pressure
passing to our south, we are having a major winter storm. The
low pressure moves off the Carolina coast Sunday evening taking
most of the wintry weather with it. The last of the light
precipitation finally ends Monday night when the upper trough
passes. Cool high pressure will be in control Tuesday and Wednesday,
then the next storm system arrives at the end of the week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 930 PM EST: No significant changes to the forecast as of mid-
evening. Caught a nice radar bright band strung out west to east
across the nrn Upstate earlier this evening, which essentially
marked the transition zone between the rain with some sleet
across the srn 2/3 of metro GSP, and the mostly snow across nrn
Greenville and nrn Spartanburg counties. That boundary has since
drifted north toward the NC state line. Meanwhile...the northern
extent of the light precip can`t seem to make it into the nrn
foothills and nw Piedmont, which is only allowing temps up in that
region to cool off this evening, which means lower wet bulb temps,
which means even more certainty that precip will either start as
snow or quickly change to snow in the I-40 corridor east of the
mtns later tonite. We await more guidance before applying any
mid-course corrections.
Otherwise, a 1013 mb surface low center was analyzed over southeast
Louisiana this afternoon, while water vapor imagery and RAP upper-
level initializations reveal a vigorous southern stream wave over
east Texas. There is good model agreement on the eastward evolution
of these features, but subtle, yet important differences exist with
regard to the thermal profiles. The 500 mb low over east TX will
lift northeast over the MS River Valley tonight and then across
the Appalachians on Sunday. Meanwhile, the surface low center
is expected to move across southern GA tonight and then exit the
southeast coast by midday Sunday. Mid-level frontogenetical forcing
over the baroclinic zone draped over our region this afternoon will
give way to robust deep forcing overnight. These mechanisms will
come together atop the western Carolinas and northeast Georgia in
the form of strong, deep-layer Q-vector convergence ahead of the
main wave, strong right entrance region upper jetlet divergence,
and improving isentropic lift and upslope in the stout southeasterly
or easterly 850 mb flow. The best forcing and deepest moisture
will arrive just as 850 mb temperatures cool rapidly from north to
south circa 06Z-12Z. A blend of cooler GFS and warmer NAM profiles
were used for this period. The 850 mb low center track through the
SC midlands/piedmont will be very favorable for heavy snow across
the southern Appalachians and adjacent NC foothills. In addition,
the very classic and deep cold air damming east of the Appalachians
will drive freezing or near freezing surface temperatures nearly
through the southern piedmont to permit freezing rain and icing
to mix in at times.
All told, the warnings, advisories, and amounts still look
reasonable with predominantly snow across most of the mountains and
foothills, a broader sleet band developing early Sunday morning,
with freezing rain making the best southern tier appearance by
daybreak Sunday. As the 850 mb low pivots off to the southeast
early Sunday, thicknesses will cool once again to lead to more
dominant snow/sleet returning from the north. This transition is
complicated by some mid and upper level drying wrapping in from
the southwest Sunday afternoon. There is some potential for more
freezing drizzle and light freezing rain in these dry pockets
where ice nuclei are unavailable, but the moisture in the profiles
is quite uncertain and continued forcing west of the surface low
could lead to some ice nucleation. Will thus stick to the top-down
hydrometeor ptype approach through the duration of the event with
the assumption that ice nuclei exist. At any rate, precipitation
rates will experience a lull Sunday afternoon and early evening
as the better forcing moves east for most areas.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 215 PM Saturday: The weakening phase of CAD will begin
Sunday night, with both the low pressure and the parent high
having drifted east off the Atlantic coast. The low to midlevel
flow over the wedge airmass will have backed somewhat, but still
driving reasonably strong WAA into the western Carolinas. The
depicted 500mb pattern is complex, with an ill-defined shortwave
and vort max slowly moving over our CWFA from the west. As the
CAD-associated forcing diminishes, the shortwave will make up for
it to some degree. Accordingly, 850mb heights recover little in
the wake of the sfc low. The warm advection is expected to maintain
sufficiently warm temps in the midlevels that a change from rain to
a wintry mix will occur over a portion of the Piedmont overnight,
with precip rates likely to pick up again early Monday. Moisture
becomes increasingly shallow as a new area of continental high
pressure exerts increasing influence, but our remaining PoPs will
be bolstered by upper divergence and/or deformation occurring
with another cutoff shortwave diving into the Deep South on
Monday. As this feature moves south of the area Monday night and
subsidence/drying continue, we finally are able to let PoPs drop
below slight-chance.
Sfc temps in this period are perhaps the least confident part
of the fcst. The expectation that heavy snow/ice cover will be
present over most of the area implies we should continue to favor
the colder guidance into Monday. The higher resolution members, such
as the NAMNest and HiRes windows, seem to show the wedge weakening
enough to allow some warming over the Piedmont, and becoming shallow
enough for temps to warm appreciably Sunday night in the higher
elevations along the Blue Ridge, plus a portion of the Savannah
River Valley. For now these sources have been minimized in the fcst,
but guidance still supports enough warming for wintry precip to
change to rain over some areas. Additional accumulation after 00z
Mon is not expected to be significant compared to what falls prior
to that time. Monday`s highs will be high enough to support some
partial melting, though with generally mostly cloudy or overcast
skies it likely won`t reduce snow/ice pack very much. Roadways
are likely to become wet and with much colder temps still expected
Monday night, black ice will be widespread around the region. After
the end of the Winter Storm Warning we likely will need to issue
an Advisory to cover the black ice threat through early Tuesday.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 235 PM EST Saturday: The guidance agrees an a very energetic
storm system affecting the area next weekend. However, there are
some significant differences in the details. Before then, expect dry
and cold high pressure for Wednesday. Lows will be 10 to 15 degrees
below normal with highs 5 to 10 degrees below normal.
The high will remain ridged in place across the area Thursday in a
cold air damming pattern. The center of the high is progressive so
this will not be classical damming. Moisture begins to increase
ahead of the next weather system with weak isentropic upglide as
well. Small rain chances will develop during the day. Lows will
range from near normal to 5 degrees below normal with highs around
10 degrees below normal. If the precip starts early enough, then
some would fall as snow before warming begins. However, the chance
of any accums is near zero.
As mentioned above, the guidance agrees that a strong upper low
forms in a deep trough over the central CONUS on Friday. The GFS and
Canadian are farther north and faster than the ECMWF. The GFS has
the upper low moving into the TN valley Friday and to the mid-
Atlantic on Saturday. The ECMWF has the low moving to near Mobile
Friday and to central GA on Saturday. The GFS swings an occluding
front across the area Friday with the occluded low moving east
across VA Saturday. The ECMWF has the occluding low passing by to
our south in Miller-A fashion. Both models have good in-situ damming
forming but are still relatively warm keeping the precip liquid
Friday. The GFS is very dynamic with strong shear and helicity
developing. There is some elevated instability ahead of the front
across the I-77 corridor. The ECWMF has little to no instability.
The GFS shows a long period of NW flow snow developing with some
snow showers breaking containment across the NC foothills and
piedmont. The ECMWF would suggest snow showers across much of the
area with the farther south low. Given the big change in the ECMWF
forecast, have trended toward the GFS solution with low confidence.
That said, it does look like Friday will be wet either way, so have
likely PoP for that period. Kept thunder out for now. Have highs
warming above normal for Friday and cooling to near normal for
Saturday. Lows will be above normal both mornings.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
At KCLT and Elsewhere: Damming continues to build in with precip
overspreading the area. PL reported at KCLT at 23z, it`s been
snowing for a while at KAVL, and precip hasn`t gotten to KHKY just
yet; still all rain in the Upstate but the cooling temps are slowly
working south. Expect a mess of wintry precip across the area, with
KGMU/KGSP/KCLT seeing the most mix, while KAVL/KHKY should see
mostly -SN. KAND mostly -RA with some -FZRA or PL mixing in in the
morning. Cigs will vary between LIFR and low MVFR through the
period, with vsbys sometimes <1/2SM in the heavier SN. Should see
some increasing gusts across the Piedmont TAFs tomorrow morning as
well, and have introduced LLWS at KAVL per latest guidance. Precip
rates will diminish Sunday afternoon but incredibly messy until then.
Outlook: The winter storm will linger late Sunday through Monday,
with plenty of wintry ptypes and low restrictions. Snow showers may
get reinforced from the west Monday as an upper disturbance arrives
from the west. Significant improvement is not expected until Tuesday.
Confidence Table...
03-09Z 09-15Z 15-21Z 21-00Z
KCLT Med 72% Med 64% Med 78% High 100%
KGSP Med 75% Low 58% High 91% High 91%
KAVL Low 56% Med 75% High 86% High 100%
KHKY Med 78% Med 69% Low 58% High 100%
KGMU Med 77% Low 58% High 91% High 100%
KAND Med 78% Med 75% High 100% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Winter Storm Warning until noon EST Monday for GAZ010-017.
Winter Storm Warning from 1 AM Sunday to noon EST Monday for
GAZ018.
Winter Weather Advisory from 1 AM Sunday to noon EST Monday
for GAZ026-028-029.
NC...Winter Storm Warning until noon EST Monday for NCZ033-035>037-
048>053-056>059-062>065-068>072-082-501>510.
SC...Winter Storm Warning until noon EST Monday for SCZ001>003-
005>009.
Winter Storm Warning from 1 AM Sunday to noon EST Monday for
SCZ004-010-012>014.
Winter Weather Advisory from 1 AM Sunday to noon EST Monday
for SCZ011-019.
&&
$$
SYNOPSIS...DEO
NEAR TERM...HG/PM/TDP
SHORT TERM...Wimberley
LONG TERM...RWH
AVIATION...TDP
Area Forecast Discussion...cor
National Weather Service Wilmington NC
912 PM EST Sat Dec 8 2018
.SYNOPSIS...
A strong low pressure system moving across the Gulf states will
strengthen and send a surface low offshore of Savannah Georgia
Sunday morning, passing by Cape Fear late Sunday afternoon.
Periods of rain, wind, and daytime temperatures below normal,
can all be expected through at least Tuesday, as the entire low
pressure complex clears the Carolinas. Mild high pressure will
bring drying and warming into late week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 900 PM Saturday...Just a quick update to add immediate
coastal SC counties to the Wind Advisory. HRRR soundings coming
in showing a solid 30-35 kt sustained winds in the 1000-1500 ft
layer with 45-50kt at 2000 and 2500 ft, respectively. Granted,
these heights are in the layer that is thermally strongly
inverted and thus relatively stable to vertical thermal mixing
it is more than plausible for the rainfall to reach sufficient
intensity to overcome said stability and mix those momentum
levels to the ground.
As of 730 PM Saturday...Forecast holding, temperatures nearly on
the mark, all liquid falling, chilly liquid. No changes were
needed, but will take a second look at 00z data sets regarding
winds along the SC coast on Sunday, presently, just below
advisory criteria. Rain rates across NE SC and SE NC 0.07"
per hour or less, so not flood threat anytime soon. A few
moderate rain pockets could introduce brief ponding and a
hydroplaning danger on high speed thoroughfares overnight.
Most hourly temperature guidance showing leveled-off temps
overnight or dropping a few degrees.
As of 315 PM Saturday...Overrunning, ie. Isentropic lift, will
initially be the primary cause of the pcpn across the FA this
aftn into this evening. Later this evening and overnight, the
old frontal boundary will be lifting northward as a warm front
and by daybreak Sun, it will extend ENE over the Atlantic waters
from the sfc low progged over coastal Georgia. In addition to
overrunning, the FA will have dynamics from mid- level s/w
trof(s) to further enhance the pcpn across the FA. At this point
do not expect any pcpn type issues across the FA. Not enough
cold air will make it to the FA prior and during this Pcpn Event
and although the warm front is progged to stay over the
Atlantic waters, it`s close proximity will produce NE to ENE
winds in the low levels, enough to tap those mild SSTS.
Have indicated, the heaviest rain occurring from late in the
pre-dawn Sun hrs thru late daytime morning Sun which corresponds
to the closest approach of the sfc low as it tracks NE over the
Atlantic waters parallel to the Carolina coastlines, reaching
the offshore waters SE of Cape lookout by sunset. It`s during
Sun when the best deepening phase will occur and as a result, a
tightening of the sfc pg. Winds along the immediate ILM NC Coast
will flirt with Wind advisory criteria in gusts during this
deepening phase and will go ahead and raise one for the coastal
zones from Surf City To Cape Fear which includes Bald Head
Island. The rainfall amounts will remain under FFA criteria but
unfortunately will lead to additional and revised upwards to
various River Flood Warnings across the FA. Ie. The Lumber River
at Lumberton progged to reach Moderate Flood Stage.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 315 PM Saturday...The mid levels will feature a cutoff
low forming across the Tennessee Valley which kinda morphs into
an east/west mid level trough Monday before being kicked to the
east by Tuesday morning. At the surface there will be a broad
but not necessarily frigid northeasterly flow with low pressure
offshore and high pressure well to the west. Really there is no
well defined forcing mechanisms around with the mid level as the
models show the mid level feature developing weak precipitation
along the trough axis in what essentially appears to be
dynamically driven moisture. The deeper moisture will have long
since exited the area. Basically continued to advertise chance
pops with an overall trend downward through the period. There
remains a small risk of a brief period of freezing precipitation
late in the period but moisture will be all gone as
temperatures become conducive.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 315 PM Saturday...A fairly progressive mid level pattern
will develop across the U.S at least briefly. Mid level ridging
and modified surface high pressure will bring dry and
reasonably warm conditions for mid week moreso on Wednesday and
Thursday. Tuesday still looks be a little on the dreary side as
mid level and surface low pressure move off to the east slowly.
Highs both Wednesday and Thursday could approach 60 in some
areas which is just about normal for this time of year. The main
focus of the extended period arrives late in the week in the
form of closed low pressure at the mid levels moving across the
Tennessee Valley. Plenty of moisture associated with this system
as it slowly progresses eastward for next weekend. Raised pops
incrementally to address some increase in confidence with this
system.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
As of 00Z...Cigs dropping at KFLO currently and confidence is high
IFR will spread to the remaining terminals this evening. Vsbys
should remain MVFR in light to moderate rain. Northeast winds will
increase overnight gusting to 25-30 kt, highest at the coastal
terminals. IFR likely to persist through tomorrow.
There is a chance for non-convective LLWS between 12Z and 17Z
tomorrow morning at coastal sites with winds at 2000 ft between 45
and 50 knots, but strong forecasted surface winds and low confidence
have kept mention out of TAFs for now.
Extended Outlook...Low pressure system will lead to MVFR/IFR/rain
Saturday through Monday. Clearing Tuesday. VFR Wednesday and
Thursday.
&&
.MARINE...
NEAR TERM /THROUGH SUNDAY/...
As of 315 PM Saturday...Solid Gale Warning to remain in effect
for all waters this period. During the closest approach of the
intensifying fcst low, the area waters could see gusts pushing
40 to 45 kt from early Sun morning thru early to mid-afternoon
Sun. Storm Force gusts will likely occur over the adjacent
offshore waters depending on the intensity of the low. With the
frontal boundary remaining over the offshore waters, wind
directions will 1st veer from NE to ENE tonight thru early Sun.
As the low passes by the area waters during Sun, winds will
back to N to NNE directions.
Significant seas will build rather quickly during the next 12
hours and peak in double digits across the waters extending from
10 to 20 nm out late tonight thru much of Sunday. The exception
will be from South of Cape Fear to Little River Inlet where
seas will be lower, especially near shore, due to NE winds
being an offshore trajectory for these waters. Seas will
primarily be composed of wind driven waves with not much, if
any, swell component added on.
SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 315 PM Saturday...Gale conditions will continue for a few
hours as the gradient is slow to subside with slow moving low
pressure offshore. Anticipate small craft conditions through the
remainder of the period with northeast winds either side of 20
knots. Significant seas will relax a bit from the earlier gale
forced values but remain well into small craft criteria, with a
still healthy 5-8 feet by Tuesday morning.
LONG TERM /TUESDAY THROUGH THURSDAY/...
As of 315 PM Saturday...Expect a northerly component to the
winds most of the period as high pressure moves west to east
across the northern Gulf of Mexico. A return flow may develop
late Thursday as the next storm system develops in the
Tennessee/Mississippi Valley. Elements may warrant a
continuation of a small craft advisory Tuesday but should
diminish enough to be headline free the other days.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Wind Advisory from 6 AM to 6 PM EST Sunday for SCZ054-056.
NC...Wind Advisory from 6 AM to 6 PM EST Sunday for NCZ106-108-110.
MARINE...Gale Warning until 10 PM EST Sunday for AMZ250-252-254-256.
&&
$$
SYNOPSIS...MJC
NEAR TERM...DCH/MJC/MBB
SHORT TERM...SHK
LONG TERM...SHK
AVIATION...MRR
Area Forecast Discussion
National Weather Service Lincoln IL
845 PM CST Sat Dec 8 2018
.UPDATE...
Issued at 845 PM CST Sat Dec 8 2018
An elongated axis of surface high pressure will continue to extend
across northern IL tonight, providing for winds ranging from
light and variable for some areas north of the Illinois River to
a light northeast wind elsewhere. Nearer to the high pressure
axis, some diurnal cloud cover is slowly dissipating, but may be
replaced by patchy fog late in the night as radiational cooling
increases. Afternoon forecast package had patchy fog mainly in
Knox, Stark and Marshall counties, and this still looks about
right. Lows should range from the mid teens over most of central
IL, to around 20 south of I-70. Otherwise, have made some minor
adjustments to cloud cover with the evening update.
&&
.SHORT TERM...(This evening through Sunday)
ISSUED AT 318 PM CST Sat Dec 8 2018
20z/2pm surface analysis shows a sprawling area of high pressure
over the southern Great Lakes...while a 1012mb low tracks across
southern Louisiana. The high will continue to suppress the
southern-stream system along the Gulf Coast through Sunday:
however, high clouds will stream as far north as southeast
Illinois. Latest satellite imagery continues to show the high
clouds across the E/SE, with lower diurnal clouds primarily
along/north of I-74 into northern Illinois. Think these will
largely erode toward sunset, but the HRRR hints at re-development
overnight as the boundary layer flow becomes E/NE. Have therefore
gone with mostly cloudy wording along the northern periphery of
the KILX CWA tonight, with partly to mostly clear conditions
elsewhere. With clear skies and light winds, radiational cooling
over the light snow pack will allow lows to drop into the lower
teens across the heart of central Illinois...with lower 20s south
of I-70 where a thick blanket of high clouds will persist. May
see some fog development late tonight as well...particularly
northwest of the Illinois River near Macomb and Galesburg. Any fog
will burn off by mid-morning, followed by mostly sunny and cool
conditions on Sunday with high temperatures in the lower to middle
30s.
.LONG TERM...(Sunday night through Saturday)
ISSUED AT 318 PM CST Sat Dec 8 2018
High pressure will drift east of the region early next week,
allowing a southerly return flow to bring a gradual warming trend
to central Illinois. High temperatures will remain in the middle
to upper 30s on Monday, but will rise into the 40s Tuesday through
Saturday. The next significant chance for precipitation will hold
off until Wednesday when a weak disturbance brings a chance for
rain showers. After that, a stronger system will impact the region
by the end of the week. 12z Dec 8 models are in poor agreement
with the track of this feature, as well as the associated thermal
profile. With surface temps reaching the 40s, it appears mostly
rain can be expected on Thursday into Friday: however, snow will
be possible on the back side of the departing low Friday night.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 548 PM CST Sat Dec 8 2018
An area of MVFR cigs is expected to affect areas from around
KPIA-KCMI northward this evening as an expansive diurnal cloud
shield slowly dissipates. Current trends suggest KCMI will stay
just south of the edge of these clouds, while KBMI and KPIA may
stay in it for a few to several hours. Otherwise, conditions will
be SKC-SCT250. Winds E-NE 5-10 kts through the period.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...37
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...37
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
930 PM EST Sat Dec 8 2018
.UPDATE...
Issued at 930 PM EST SAT DEC 8 2018
Forecast still mainly on track at this early stage, and have not
made any substantive changes. Blended obs into the forecast, and
made some minor temperature revisions for tonight based on 18Z
runs. The 18Z runs still showed large differences between the NAM
and GFS for overnight and Sunday, with the NAM being colder and
wetter. There are model differences in the handling of a mid
level speed max over the TN Valley and southern Appalachians
tonight, and also low level flow over southeast KY late tonight
into Sunday, with the GFS showing more isentropic downglide around
850 mb. Low level differences could be partially due to handling
of cold air damming and terrain influence to our east. Will see
what 00Z runs look like. QPF differences for our area become a
factor already during the overnight hours, and continue into
Sunday. If the GFS were to trend toward the NAM, or it became
apparent that the NAM was verifying better early on, winter wx
would be more significant for our area and forecast changes would
be needed.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 434 PM EST SAT DEC 8 2018
The winter storm is set to begin impacting the region overnight.
However, instead of continuing the southward trend with this
system, 12Z model runs all began shifting farther north again.
Furthermore, they actually starting moving away from continuity
with vast differences in their solutions for precip types and
amounts across the CWA. The ECMWF and NAM became much more
robust with QPF, while the GFS remained more
conservative...ironically this is the complete opposite of
ongoing trends several days ago. The HRRR, the GFS and the RAP are
much warmer, with a good possibility that hydrometeors could melt
and end up falling as rain. The NAM and ECMWF show the potential
for a shallow warm nose, so while they have the highest QPF, you
can`t rule out some mixed precip, especially during onset.
To caveat this, air temperatures today, especially in the
southern CWA, rose into the upper 30s. With cloudy skies and
easterly winds, these temperatures are not expected to quickly
drop off during the evening. Even if snow is able to melt in the
warm nose and then fall back into a cold near-surface layer as
freezing rain, the surface temperatures will likely lag by several
hours before falling below freezing, helping to mitigate much of
the accumulating ice concerns. However, did keep with mention that
a glaze of ice could be possible in the hazard products. It may
actually be very possible that the best ice totals will be in the
highest terrain, due to the face that they were quite a bit cooler
today and will spend much of the night below freezing, while
being at a high enough elevation to cut into the warm nose of the
precipitation causing any melting precip to hit the ground before
having a change to refreeze. On that note, the highest terrain
will also have the best potential to accumulate snowfall.
Overall, this is a very very tricky forecast, and it is unlikely
that any one model is correct, or that the forecast is correct for
every location. However, tried to do the best to trend the
forecast farther north and find a happy medium between the current
models, WPC, and the neighboring offices. It is in somewhat high
confidence that the precip will be shifting east of the region by
Sunday evening/Sunday night. In it`s wake, the latest forecast
snow totals include a dusting to around an inch across the central
portion of the CWA, 1 to 3 inches in a swatch stretching from the
SW portion of the CWA to central/northern Pike County. The
counties near the VA border could range from 3 to 5 inches, with
locally higher amounts possible in the high terrain. Once again,
it is entirely possible that totals could range from 5 inches on
the peaks to almost no snow in the valleys depending on how the
temperature/moisture profile pan out.
Any snow that does fall will be heavy and wet, with impressively
low snow ratios being one of the few things that has remained
constant through this forecast. Snow of this nature can cause
major impacts even for small amounts, creating slushy, slick and
treacherous road conditions, as well as adding weight onto trees
which could lead them to break and possibly down power lines. Based
on the latest snowfall forecast, went ahead and upgraded counties
along the VA border to a Winter Storm Warning. Even if the valley
locations see less snow compared to the higher elevations, there
will likely still be impacts related to the heavy wet nature of
the snow. Kept the remaining counties within an advisory with 1 to
3 inches forecast. Since the models are trending farther north,
also added another tier of counties northward to the advisory,
including Rockcastle, Jackson, Owsley and Breathitt, where snow
totals have increased to between 1 and 2 inches and impacts are
likely.
.LONG TERM...(Monday through Saturday)
Issued at 444 PM EST SAT DEC 8 2018
The models are in good agreement with an amplified long wave
pattern to continue across the CONUS through the period. High
pressure will work in across the Ohio and Tennessee valleys
through the middle of next week, bringing dry weather. Another
deep system will then take shape across the central CONUS by
Thursday, eventually bringing a period of unsettled weather across
eastern Kentucky as we close out the work week and head into the
weekend. There is much uncertainty with details on the evolution
with this storm system, and have generally favored slower timing,
given the amplitude.
Clouds will be on the decrease on Monday, as high pressure builds
in from the west. Temperatures will average below normal early
next week, with highs in the low 40s and lows in the teens and
20s. Tuesday morning looks to be the coolest morning. By the
middle of the week, high pressure will shift off to our east, with
return flow ensuing. This will lead to some ridge/valley
temperature splits at night, and have gone purposely cooler in
our eastern valleys.
Again, have favored a slower solution with the deeper system to
impact the area Thursday through Saturday, reserving the higher
PoPs from Friday into Saturday. Temperatures will trend above
normal through Thursday and Friday, with highs back in the 50s.
Readings will then cool off to near normal by Saturday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 700 PM EST SAT DEC 8 2018
VFR conditions and winds less than 10 kts still prevailed at TAF
issuance. However, that will change during the night. As
precipitation develops northward into the area, ceilings and
visibility will lower. Sub-VFR conditions should arrive near the
TN border around 06Z, and reach their northward extent near the
Mountain Parkway late Sunday morning. Much of the area south of a
line from around KSME to KPBX is expecting a deterioration to IFR
during this time frame. Improvement is forecast from northwest to
southeast on Sunday afternoon, but locations near the TN and VA
borders will likely not climb above MVFR before the end of the
period.
In terms of precipitation, a mixed bag of wintery weather is
possible, but the majority is expected to be snow and rain. The
precipitation could be heavy at times, especially near the TN and
VA borders. Precipitation amounts and intensity will taper off
with the northward extent, and little if any precipitation is
expected north of the Mountain Parkway.
Winds during the period will remain generally below 10 kts and out
of the northeast.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 7 PM EST Sunday for KYZ087-088-118-
120.
Winter Weather Advisory until 7 PM EST Sunday for KYZ068-069-079-
080-110-112>117.
Winter Weather Advisory until 7 PM EST Sunday for KYZ083>086.
&&
$$
UPDATE...HAL
SHORT TERM...JMW
LONG TERM...GEOGERIAN
AVIATION...HAL
Area Forecast Discussion...UPDATED
National Weather Service Lubbock TX
811 PM CST Sat Dec 8 2018
.UPDATE...
Several reports have been received of dense freezing fog in and
around the Lubbock area. The fog does not show up on satellite yet
at the moment because this fog is likely less than 10m thick. The
HRRR certainly has the best handle on this fog and should expand
over the next several hours favoring the snow covered areas.
&&
.PREV DISCUSSION... /issued 523 PM CST Sat Dec 8 2018/
AVIATION...
Snow cover in place providing abundant moisture will allow for
freezing fog to develop later this evening lasting until mid
morning on Sunday. KLBB is most likely to experience this with the
deepest snow depth around that terminal. Lesser chances will exist
at KPVW with less snow depth.
PREV DISCUSSION... /issued 150 PM CST Sat Dec 8 2018/
DISCUSSION...
Our winter storm has now pushed east of the region. Only a few
little snow showers remain across the eastern half of the forecast
area while out west clearing skies have pushed in from New Mexico.
Skies are expected to clear this evening, but that will lead to
additional issues, especially in the snow-covered parts of the
forecast area. The combination of snowpack and clear skies will
result in rapid cooling having the effect of refreezing moisture
on area roadways and the likely development of some freezing fog
and stratus. Some of the fog could become dense, something that
will be monitored as the evening progresses.
The remainder of the forecast remains relatively quiet. Models
continue to hold onto a progressive pattern with a long-wave
trough over much of the CONUS through the upcoming week. Short-
wave ridging is still on track to cross the region Tuesday
followed quickly by southwesterly mid and upper flow. These two
days with their westerly low level component will result in the
warmest days of the week. Finally, another upper level short-wave
trough will approach the region, this time from the northwest.
There is still some hint that this trough could bring a brief shot
of rain showers Thursday. Will maintain slight chance wording for
that day with this forecast.
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
Freezing Fog Advisory until 10 AM CST Sunday for TXZ027>030-
033>036-039>042.
&&
$$
01
Area Forecast Discussion
National Weather Service Paducah KY
622 PM CST Sat Dec 8 2018
.UPDATE...
Issued at 619 PM CST Sat Dec 8 2018
For aviation section.
&&
.SHORT TERM...(THIS EVENING THROUGH Monday NIGHT)
ISSUED AT 230 PM CST SAT DEC 8 2018
No major changes expected for the advisory area for tonight.
Models are struggling with the dry air from high pressure centered
over Indiana this afternoon. HRRR and most other models continue
to push precipitation northward, but progress is slow. Have had
reports along our southern border of snow and some sleet.
On the larger scale, radar returns are drying up in northwest
Arkansas, but should return to that area and our southern border
late this evening as the upper low tracks east into central
Tennessee by 12z Sunday.
I have trimmed the northern PoPs from CONSHORT for tonight based
upon current trends. May still be too far north. Precipitation
should generally be snow/sleet this evening then transition to
more of a mix of snow, sleet and freezing rain. The system should
depart the area around daybreak.
Snowfall amounts look to be 1 inch or less and any ice generally
less than 1/10 of an inch. The combination may cause some issues
traveling so will keep the advisory going.
Model soundings vary by model, of course. Dry air near the surface
will gradually be overcome during the evening over the extreme
southern sections. A warm nose develops this evening with warm
advection at 925 over the HOP area. This will help to create a
variety of precipitation types. However, the precipitation is
expected to be generally light.
As this system moves east, high pressure will keep the area dry
through early Tuesday. Optimistic sky forecast to actually see
some sun.
.LONG TERM...(Tuesday THROUGH Saturday)
ISSUED AT 230 PM CST SAT DEC 8 2018
The medium range models were in reasonable agreement, for the most
part, in the extended forecast period. Tue/Tue night should be the
beginning of a modest warming trend for us under ridging aloft and a
developing westerly to southwesterly low level flow. Most model
solutions suggest that by Wed, measurable pcpn is possible by the
evening, as it may take all day for the lower troposphere to moisten
up. The source of energy for this minor rain event will be mid level
shortwave energy embedded in the quasi-zonal flow over the country`s
midsection.
Just behind this feature, the models continue to advertise a dynamic
low pressure system digging/deepening through the southern Plains,
though the 12Z ECMWF showed a much more southerly path of this low,
moving into the Deep South by Fri. Most model solutions suggested
that the dynamic low will be stacked or nearly so by then as it
continues moving eastward, and eventually into the eastern Great
Lakes region (most models). The ensemble means tended to suggest the
more northerly track possibility.
A slightly modified initialization blend suggests PoPs for generally
light amounts of rain will steadily ramp up in the warm advection
pattern ahead of this system Wed night and Thu. At this time,
forecast high precipitable water values, the apparent slow movement
of this system, and robust Gulf moist advection will promote heavy
rain potential primarily Thu night and into the daylight hours Fri.
For now, we will go with 1-2 inches of total rainfall. The system
should continue to move away to the east on Fri, possibly leaving
Sat mostly dry. Lighting is a possibility, but not a certainty. It
is dependent on where the surface low will be, the location of which
is vague at this time. It was left out of the forecast for now. What
is more certain is that the latter half of next week will be wet at
some point.
&&
.AVIATION...
ISSUED AT 620 PM CST SAT DEC 8 2018
Relatively calm on the north side of the storm system moving
through the southern states. All TAF sites VFR through the period.
Only precipitation/ceiling issues will be confined to the
southern borders of Missouri and Kentucky where MVFR conditions
possible 06z-12z. Light FZRA/IP also seem a good possibility
along/just north of the AR and TN borders.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...Winter Weather Advisory until 6 AM CST Sunday for MOZ108>110-112-
114.
IN...None.
KY...Winter Weather Advisory until 6 AM CST Sunday for KYZ001-002-006-
009-012-017-022.
&&
$$
UPDATE...GM
SHORT TERM...PS
LONG TERM...DB
AVIATION...PS