Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/06/16
Area Forecast Discussion
National Weather Service New Orleans LA
719 PM CST Mon Dec 5 2016
The sounding is near saturated this evening through a broad
inversion up to 880 mb, which represents the elevated portion of
the warm front. PW of 1.6 inches is well above average for this
time of year and there was localized heavy rain earlier today. The
chance for showers and storms continues this evening, but will be
ending from west to east overnight as much drier air moves in.
Instability is elevated, though there is still 1300 J/KG of most
unstable CAPE present. The primary threat from any storms will be
strong winds, though that is a low chance and mainly for the
eastern portion of the area. Winds are easterly at the sfc then
switch to southwest by 950 mb. Peak wind is 95 kts at 180 mb.
.PREV DISCUSSION... /issued 402 PM CST Mon Dec 5 2016/
Warm front situated along the immediate LA coast and cutting
across Plaquemines Parish near Pointe a la Hache to Mobile Bay at
this time. Surface based air to the south with elevated
instability on 50+kt low level flow over the stable marine layer.
1005mb surface low near Vermilion Bay moving NNE to bring cold
front through the forecast area through the evening hours.
Rainfall has tapered a bit but may re-ignite once low moves inland
a bit and some frontogenetic forcing takes hold with northward
surge of warm air. It does appear dry-slot moves the precipitation
east of the forecast area by midnight. Still have some potential
for severe wind gusts given amount of low level jet dynamics just
above the stable layer, but threat diminishes or ends with frontal
passage between 9 pm and midnight from west to east. Other concern
will be propensity for fog to form when it is not raining as
residual ground moisture and a light low level wind allow for
saturation to dewpoint despite cloud cover, but again, these
conditions should improve with frontal passage and dry air
advection overnight. Tuesday should be dry and cool to mild with
limited cold air advection. Better surge of cooler air takes place
Wenesday and Thursday.
Light to moderate freeze conditions expected for a couple of
nights Thursday night and again Friday night for the more interior
and drainage prone areas of the CWA. Air mass shifts east rather
quickly and moderates over the weekend for strong return flow to
onset later Saturday and Sunday. Models showing a deeper surge of
cold air poised to move out of the Plains States middle of next
The broad shield of rain over the area this morning and early
afternoon has dissipated with only scattered showers remaining.
However, IFR and LIFR ceilings ranging from 300 to 1000 feet will
continue to impact the terminals through the reaminder of the night
and into tomorrow morning. Ceilings should finally mix out and
conditions improve to MVFR and VFR range after 18z tomorrow. The
low ceilings should also allow for visibilities of 1 to 3 miles
tonight. HRRR model guidance continues to indicate the potential
for another band of convection developing around 00z and impacting
most of the terminals through 03z. Have kept in a tempo group with
TSRA wording to reflect this risk. 32
Small craft advisory has already been posted earlier this
afternoon in anticipation of wind increase this evening as
gradient tightens pre-frontal, followed by dry air enhancement
once the system and front moves through overnight. winds should
settle rather quickly Tuesday with little pressure gradient
support. Cold air surge enters north gulf late Wednesday with
colder air pushing off the coast during the day Thursday. This
should be another SCA situation until the cold air advection
abates Friday afternoon. Air mass modifies rather quickly over the
weekend with baroclinic return expected to bring moderate onshore
flow by late Saturday night into Sunday. 24/RR
DSS code: Blue.
Activities: Monitoring convective and heavy rainfall trends through
Decision Support Services (DSS) Code Legend
Green = No weather impacts that require action.
Blue = Long-fused watch, warning, or advisory in effect or
high visibility event.
Yellow = Heightened impacts with short-fused watch, warning or
advisory issuances; radar support.
Orange = High Impacts; Slight to Moderate risk severe; nearby
tropical events; HazMat or other large episodes.
Red = Full engagement for Moderate risk of severe and/or
direct tropical threats; Events of National Significance.
.PRELIMINARY POINT TEMPS/POPS...
MCB 52 62 45 65 / 50 0 0 0
BTR 52 63 47 69 / 40 0 0 0
ASD 53 65 46 68 / 40 0 0 0
MSY 57 64 52 68 / 30 0 0 0
GPT 56 65 48 66 / 40 0 0 0
PQL 56 65 46 66 / 40 0 0 0
GM...Small Craft Advisory until 9 AM CST Tuesday for GMZ530-532-534-
GM...Small Craft Advisory until 9 AM CST Tuesday for GMZ532-534-536-
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1044 PM EST Mon Dec 5 2016
High pressure will extend over the waters from the north overnight
with developing low pressure approaching from the southwest late.
The low will move across the area Tuesday and then northeast
Tuesday night. A strong cold front will move through late
Thursday, followed by cold high pressure Friday into Saturday.
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
As of 1000 PM Monday...based on radar trends and latest model
data, increased POPs all zones overnight and sped up timing of
rain developing across hour a few hours, with categorical wording
all zones by morning. Leading edge of widespread rain shield with
increasing WAA and isentropic lift has spread across SC this
evening and latest models support activity moving into Eastern NC
overnight. Temps on track.
As of 305 PM Monday, low pressure continue to move away from our
northern coast as high pressure ridges into the area from the Ohio
Valley. Skies have cleared from the north and west this afternoon
ahead of next area of low pressure that will move northeast from
the western Gulf of Mexico region. Leading edge of light
precipitation has now moved into far western South Carolina and
models have decent agreement showing bulk of precipitation
arriving around midnight. PoPs have been ramped up accordingly
from chance this evening to likely/categorical after midnight,
highest over the S/SW CWA. Low temperatures tonight should be in
the 45 to 50 degree range.
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
As of 305 PM Monday, as surface low traverses eastern NC Tuesday,
expect widespread light to moderate rain. Think amounts will be
similar to the event from last year, with 1-2 inches possible per
latest guidance, heaviest over southern and western counties.
Highs will range from the lower 50s far northwestern areas to
lower 60s coast. Looks like precipitation should cut off from
southwest to northeast and end in most areas between 21z and 00z
Weds as low exits off the Delmarva Peninsula.
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
As of 215 AM Mon...A strong cold front will cross late Thu with
cold temps Fri through the weekend.
Tuesday Night...Good cold air advection will develop in the wake
of the exiting low leading to lows in the lower 40s inland to
lower 50s beaches.
Wed and Wed Night...Dry with seasonal temps as weak high pres quickly
crosses. Highs Wed upr 50s to around 60 with lows Wed night lower
40s inland to upr 40s/around 50 OBX.
Thu through Sunday...Cold front with limited moisture will cross
late Thu/Thu evening cont slight chc to low chc of shra with
front. High temps ahead of front Thu will be in the upr 50s to
lower 60s. Main story will be cold air assoc with strong high pres
building in behind front Fri thru Sat...highs both days mainly
low to mid 40s with lows Fri night and Sat night reaching couple
dgrs either side of 25 inland to lower/mid 30s beaches. As the
high begins to slide E on Sunday temps and moisture will increase
with high around 50 inland to near 60 coast. Slight chc of shra
poss mainly coast as moisture increases.
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
Short Term /through 00Z Wednesday/...
As of 645 PM Monday...VFR conditions expected to continue over
area this evening but deteriorating overnight with IFR to possibly
LIFR CIGs likely after 09Z and persisting through the day Tuesday.
Developing low pressure will approach from the SW overnight and
move across area during the day Tuesday. Patchy light rain will
spread in from SW 02Z-06Z, then widespread heavier rain will move
in 06Z-09Z with CIGs lowering to IFR and VSBYs MVFR to IFR. Main
rain shield will move E of area during afternoon but low CIGs
expected to persist into evening even with winds shifting to west
around 10 KT.
Long Term /Tue Night through Friday/...
As of 215 AM Mon...Rain will end as the low departs offshore Tue
night however fcst soundings indicate low lvls will remain
saturated with IFR cigs much of the night. High pres builds in Wed
and slides offshore Wed night with dry weather and VFR expected
once low clouds lift early Wed. A strong cold front with limited
moisture will cross late Thu or Thu evening and dont think will be
much precip with cont VFR. Cold high pres will build in thru Fri
with clearing skies and gusty NW winds.
Short Term /Tonight and Tuesday/...
As of 1000 PM Monday...Winds have diminished to 10-15 KT most of
waters with seas down to 3-5 FT so forecast on track into
overnight. Latest models do indicate stronger winds developing
late tonight over southern waters with tightening pressure
gradient ahead of developing low from SW and adjusted wind speeds
upward with blend of HRRR into Tuesday morning. Could see period
of SCA winds 6-9 AM but will let next shift take a look at
complete 00Z model suite to decide on starting SCA sooner than
As of 310 PM Monday, gusty N/NE winds 15-20 knots continue across
the northern waters with seas around 6 feet at Diamond Buoy and
likely offshore of the northern waters this afternoon. Will
continue SCA through midnight for these areas. As next surface low
tracks inland from the western Gulf of Mexico region into the
Carolinas tonight and Tuesday, gradient tightens and seas build to
SCA range by early afternoon Tuesday over the southern waters and
have issued a new SCA from Ocracoke South starting at 18Z Tuesday
extended into late Wednesday evening. Another SCA will be needed
for the northern waters as gusty winds/rough seas occur behind
departing low Tuesday afternoon/evening into Wednesday morning.
Long Term /Tue Night through Friday/...
As of 215 AM Mon...As the low departs to the NE Tue night into
Wed will have a period of gusty NW winds keeping seas
elevated...espcly outer central and northern waters. High pres
builds in Wed and moves offshore early Thu with light winds and
seas subsiding to 2 to 4 feet by first part of Thu. Gusty W winds
develop later Thu ahead of cold front then become NW and remain
gusty later Thu night and Fri behind the front with strong CAA.
SCA a good bet most waters later Thu night into Fri.
MARINE...Small Craft Advisory from 1 PM Tuesday to 10 PM EST Wednesday
Area Forecast Discussion
National Weather Service Spokane WA
403 PM PST Mon Dec 5 2016
Light snow is forecast for the Columbia Basin, Palouse, and
southern Idaho Panhandle tonight as a low pressure system moves
through the area, otherwise expect dry weather with some rather
colder temperatures Tuesday afternoon through Wednesday night.
More snow will be on the way Thursday into Friday, and this snowy
pattern may continue into the weekend.
Tonight through Tuesday night...A small and compact closed area of
low pressure drifting across the cold airmass over the area will
spread snow slowly from west to east across a portion of Eastern
Washington and Northern Idaho tonight and into Tuesday morning...
primarily south of a line from Omak to Deer Park to Prichard. The
overall trend is for this compact low and associated bands of snow
slowly rotating counterclockwise around it to all translate west to
east tonight and Tuesday morning. 700-500mb lapse rates of the cold
and quite conditionally unstable airmass are quite steep and in the
8.0-8.0 deg C/Km range which will aid in allowing for moderate snow
ratios generally near 15 to 1. Have favored the numerous high
resolution models coming in more frequently such as the HRRR which
have reasonable consistency in the positioning and movement of the
low and its associated snow bands. Greatest intensity snowfall
expected in the ongoing winter weather advisories during the early
afternoon and evening and highlights were issued to address the
higher intensity snowfall occurrence impact during the afternoon and
early evening commute rather than the overall quantity of snow.
Afterword snowfall intensity should decrease substantially but not
stop until the low and its associated snow bands move out of the
area and into Northeast Oregon late Tuesday morning. Otherwise
behind the exiting low continually cold northerly flow of a dry and
cold continental airmass allows the cooling trend to continue with
decreasing cloud cover and brisk northerly winds in the north to
south oriented northern valleys such as the Purcell Trench and the
Okanogan Valley down to the Waterville Plateau. /Pelatti
Wed through Mon Nt: Wed and Wed Nt will be the coldest
temperatures we`ve had the pleasure of enduring this "winter" so
far, with low and high temps generally ranging from the single
digits to mid teens, and mid teens to mid 20s, respectively. With
this antecedent very cold continental polar air mass in place, it
will set the stage for the next round of snow and potentially
mixed pcpn Thurs through Fri Nt. The only significant changes to
the fcst were to follow the consistent model guidance trends of
slowing down the front for Thurs and decreasing pcpn amnts.
Most model guidance is still trending closer to the ECMWF as far
as timing of the inbound front. This moist cool front (more like a
warm front from a sfc perspective) overtakes the region by Thurs,
with plenty of isentropic ascent, steep lapse rates aloft, and
orographics helping to generate sufficient lift. Even though we
reduced pcpn amnts for the Thurs to Sun Nt period, the very cold,
deep air mass in place will allow for 20-25:1 SWE ratios in
general. Thus, it won`t take much pcpn to produce significant
powdery snow accumulations. Confidence in our current predicted
snow accumulations are low to moderate. It WILL snow, however.
There`s even the chance of mixed pcpn in the form of sleet or
freezing rain...but confidence is low. We`ll focus heavily on
narrowing down the specifics of the fcst the next couple days. bz
00Z TAFS: The next wave will track by the Cascades, then through
Srn WA/Nrn ORE this evening through Tues. Moderate snow has began
to fall at KEAT, with snow just beginning to reach the ground at
KMWH. Expect this snow to expand slowly E through Tues morning,
lowering cigs and vsbys to IFR for KEAT/KMWH/KPUW through Tuesday
morning. The Ern TAF sites may not see steady snow until after
03-06Z. The precipitation threat gradually starts to wane
overnight and especially Tuesday morning from the west. The
Spokane area TAFs will likely fall to MVFR.
.PRELIMINARY POINT TEMPS/POPS...
Spokane 18 24 9 20 11 23 / 50 20 0 0 10 50
Coeur d`Alene 16 23 6 20 8 22 / 20 20 0 0 10 50
Pullman 21 26 12 25 15 26 / 80 50 10 0 10 60
Lewiston 23 30 16 26 16 30 / 80 40 10 0 10 60
Colville 16 24 9 20 9 22 / 20 0 0 0 0 40
Sandpoint 13 20 3 16 5 21 / 10 0 0 0 10 30
Kellogg 10 18 3 15 4 21 / 30 20 10 10 10 50
Moses Lake 22 31 13 26 15 26 / 80 40 0 0 10 70
Wenatchee 23 30 13 24 15 24 / 80 20 0 0 10 70
Omak 18 26 9 22 11 23 / 60 0 0 0 0 60
WA...Winter Weather Advisory until 7 AM PST Tuesday for Waterville
Winter Weather Advisory until 10 AM PST Tuesday for Moses Lake
Area-Upper Columbia Basin.
Area Forecast Discussion
National Weather Service Blacksburg VA
953 PM EST Mon Dec 5 2016
An area of low pressure in the Gulf of Mexico lifts northeast
tonight and reaches the Appalachians Tuesday resulting in
widespread rainfall overnight into late Tuesday. Moisture pulls
off the coast Tuesday evening allowing weak high pressure to build
in from the Midwest on Wednesday. A strong cold front will cross
the region on Thursday.
.NEAR TERM /THROUGH TUESDAY/...
As of 950 PM EST Monday...
Lows for tonight were bumped upward a few degrees due to the
latest observation trends. Rain has only reached the VA/NC border,
but the latest HRRR seems to fizzle it in the next hour or so
before a stronger wave of moisture pushes northeastward. Low
pressure over the western Gulf of Mexico will strengthen and
move northeast along a stationary front. With dewpoints rising
overnight, the bulk of the precipitation should primarily be
liquid. A small area of frozen precipitation could be possible in
the higher elevations of western Greenbrier County, WV. However,
this update has lowered the amounts and coverage of any sleet or
snow toward daybreak on Tuesday.
A strong cold wedge east of the Appalachians will remain in place
Tuesday morning as low pressure moves northeast with strong
isentropic lift including upper dynamic support. A coastal low
pressure center will develop off the North Carolina coast Tuesday
afternoon. Widespread precipitation will continue through the
first part of Tuesday before starting to taper off during the
afternoon. There is enough warm air advecting in Tuesday to
transition any light wintry mixed precipitation in Greenbrier
County, WV to all rain. A light glaze of ice or coating of snow
may possible at the highest elevations. High temperatures Tuesday
will range from the mid 30s in the northern mountains to the mid
and upper 40s in the south.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 215 PM EST Monday...
Surface low along the coast should exit Tuesday evening ahead of a
secondary trailing cold front that will help boot out residual deep
moisture overnight. However enough lingering wrap around rainfall to
keep chance to low likely pops going early Tuesday night espcly western
third as well as the far northeast sections with rain tapering
elsewhere. Will see a band of more shallow nature moisture along the
cold front that looks to cross the far west after midnight and the Blue
Ridge by early Wednesday. Appears enough to warrant a chance of added
showers western slopes overnight with a gradual transition to higher
elevation snow showers late as 850 mb temps fall below 0C.
Otherwise clouds lingering mountains with downslope clearing
east and lows mainly 30s.
Wednesday into Wednesday night will be the in between period separating
a more zonal trajectory from the impending digging upstream 500 mb
trough associated with the upcoming Arctic cold shot. Models even
suggest a period of warm advection in the afternoon under sunshine as
the flow backs from a weak northwest trajectory to southwest later in
the day. This should also push highs into the 50s from the Blue Ridge
east and close to 50 west. Flow deepens from the south/southwest
Wednesday night with guidance suggesting enough moisture return for a
few late night showers south/west, that should transition to snow
showers far west early Thursday when the Arctic front nears.
Front then crosses from northwest to southeast Thursday with cold
advection/upslope driven snow showers western mountains and
possibly a few sprinkles east. However moisture appears much less
today off models per overall westerly flow, so cutting back on
pops, but leaving in some mention given light QPF showing up off
ensembles. High temps Thursday tricky pending timing of the 850 mb
front, with a possible range from 30s west to around 50 Piedmont,
before falling with a slightly slower trend likely the best bet
with the frontal passage.
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 130 PM EST Monday...
Strong cold advection will be ongoing to start the period as Arctic air
pours in ahead of high pressure that should shift east from the central
U.S. early Friday to about overhead the region by Saturday morning.
However latest models tending a bit weaker with the associated upper
trough per less digging that likely will keep the core of the Arctic
airmass to the north. This also along with very dry air advecting in
should help limit the degree of upslope snowfall behind the front as
the strongest northwest winds will only coincide with the coldest air
aloft Thursday night into Friday at best before moisture fades.
Thus going with only low pops northwest mountains Thursday night
with coverage gradually decreasing Friday. Elsewhere should remain
mostly clear but still cold and blustery into Friday evening with
overnight wind chills near zero across the higher ridges. Still
appears that Saturday morning will see the coldest temps as the
high settles overhead, although increasing high clouds may
curtail good radiational cooling per latest warmer guidance.
Otherwise lows mostly teens to near 20 mountains both nights, and
20s east with highs 20s to low 30s mountains Friday, to mid 30s to
lower 40s east.
Trough lifts out later Saturday with fast zonal flow aloft developing
Sunday into Monday as the surface high shifts east with
warming/moistening return flow developing. This will allow pieces of
energy ejecting out of the Rockies to perhaps bring some chance of
precip by late Sunday into Monday at this point. However guidance shows
considerable spread with consensus having a stronger northern stream
wave push a weak surface front with faint southern connection toward
the region by Monday. This could bring some chance of precip to mainly
the western counties by Sunday evening per faster GFS despite residual
low level dry air. Appears this would be mostly rain Sunday night into
Monday given column warming with possibly some mix late Sunday pending
timing. However quite iffy espcly given much slower timing off
the 12z ECMWF. Should see temps rebound into the upper 30s/40s
Sunday and 40s to mid 50s Monday as warm advection aloft reaches
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
As of 700 PM EST Monday...
Poor aviation conditions expected through the TAF valid period.
Negatively tilted short wave will move northeast from the
southeast U.S. Tuesday bringing widespread rain, fog, and low
clouds to the area through much of the TAF valid period. Local
radars indicate that light rain has already spread into northwest
NC and far southwest VA. A very dry layer of air just above the
surface to about 500mb will take a few hours to saturate, but this
should occur in the 04Z-08Z time frame from south to north. At
that times, ceilings will lower from just the mid/high cloud
shield presently in place quickly to MVFR/IFR and to widespread
LIFR by daybreak. Visibilities will quickly fall into the MVFR
range, the settle into the IFR range in the 08Z-10Z time frame and
hold there through much of the day Tuesday.
Strong short wave will lift to the northeast of the area in the
20Z-22Z time frame, at which time the steady rain will end, but
expect widespread low clouds, fog, and drizzle to remain in place
into Tuesday evening, smilier to what we saw yesterday, until
better drying can develop after daybreak Wednesday.
Winds will come around to the northeast east of the Blue ridge and
southeast to the west of the Blue Ridge, with the possible
exception of KLWB, where a northeast wind is also possible. An
850mb southeast jet will traverse the region early Tuesday, which
will likely equate to a period of gusty winds in the usual western
locations, namely KBLF. Some low end gusty winds are also possible
across the Piedmont later tonight into Tuesday morning. Otherwise,
generally look for speeds of 7-10ts through the TAF valid period.
Medium confidence in ceilings and visibilities through the TAF
Medium confidence in wind direction/speed through the TAF valid
Extended aviation discussion...
Drizzle, low clouds, and fog will likely remain in place Tuesday
night before drier air and westerly flow evolve across the area
Wednesday. Wednesday will be the transition day ahead of an Arctic
cold front that is expected to move through the region Thursday.
Limited moisture may result in a few showers in advance of the
front Thursday, but upslope conditions should support snow showers
across the mountains Thursday into Friday along with a significant
surge of cold air. This will lead to VFR conditions east of the
Blue Ridge through much of the period beyond Thursday, but MVFR
conditions may linger into Friday across the Alleghanys. West to
northwest winds behind the front will be strong and gusty into