Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/21/17
Area Forecast Discussion...Updated
National Weather Service Billings MT
821 PM MDT Mon Mar 20 2017
Widespread precipitation across the CWA this evening as Pacific
moisture interacts with short wave energy in westerly flow aloft.
Bumped up PoP`s for rest of evening in many locations.
Precipitation is mainly light, but there is indication of some
pockets that look a little heavier. Rather warm yet in SE corner
of state where winter weather advisory is in play until 18z
tomorrow. Will need some dynamic cooling to help change phase to
snow later tonight, but models still suggesting this will happen
so will let the advisory ride for now. Still, expect any impacts
to be limited. BT
.SHORT TERM...valid for Tue and Wed...
Radar shows shower activity beginning to become more widespread as
it begins to move back north from the foothills. Precipitable
water value over the area are likely close to .75 inch so weak
dynamics is being overcome by deep moisture to aid production of
precipitation. RUC and HRRR show this precipitation band moving
into southeast Montana and intensifying and while overnight
precipitation begins to taper off central and western zones.
Timing of precipitation over southeast Montana and weak
frontogenesis help amplify snowfall amounts and have put out a
Winter Weather Advisory for Carter and Powder River counties where
2 to 4 inches of snow is expected. Further west...including
Billings...precipitation will be decreasing while the temperatures
get cold enough to change to snow so only expect snow on grassy
areas and wet roads.
Shortwave ridging on Tuesday dries out the airmass and shifts the
precipitation into the Dakotas by afternoon. Temperatures will
remain on the cool side as easterly surface flow maintains a light
upslope and prevents mixing. Tuesday night into Wednesday a
trough moving into the Pacific Northwest increases the mid level
flow and causes leeside troughing to developing. The weather
remains dry with this regime but downslope flows develop
supporting much better mixing and temperatures rebound strongly
into the 60s. borsum
.LONG TERM...valid for Thu...Fri...Sat...Sun...Mon...
Two main weather features on the extended forecast will be on
Thursday, and again on Saturday night into Monday.
A western upper trough will push into Utah/Nevada early Thursday.
This system will spread upper divergent forcing for ascent into
northern Wyoming and southern Montana. The core of the system and
strongest dynamics will drive well to the south, but will still have
adequate moisture available over our area, and thus models were
generating roughly 0.25 to 0.50 inches of liquid over parts of
southern Montana and north central Wyoming. Have kept likely PoPs
over most of the area for Thursday. System is progged to be warm
and thus precipitation should mainly be in the form of rain
outside of the mountains.
Shortwave ridging moves in for Friday, giving a dry and mild day.
For Saturday into Monday, models are progging upper troughs to
move eastward across the region with chances for showers. The best
dynamics again look to track well south of the area, over the
central Plains, so precipitation amounts should be light.
High temperatures will generally range from the mid 50s to low
60s Thursday-Monday. RMS/Borsum
MVFR to IFR conditions will continue with rain and snow across
the area. Precipitation will likely change to snow later this
evening. Mountains will be obscured through tonight. Conditions
will improve during the day tomorrow. Reimer/RMS
.PRELIMINARY POINT TEMP/POPS...
Tue Wed Thu Fri Sat Sun Mon
BIL 032/046 036/067 041/054 034/061 039/060 038/057 035/054
83/S 22/W 36/R 20/U 12/W 33/W 23/W
LVM 031/047 036/064 035/054 029/061 037/058 035/056 031/053
52/S 32/W 45/R 21/U 14/W 53/W 33/W
HDN 032/050 032/070 039/056 032/063 033/062 036/058 034/056
93/S 21/B 36/R 30/U 02/W 23/W 23/W
MLS 032/043 034/066 040/057 035/060 036/061 037/059 035/055
53/S 22/W 14/R 10/U 01/B 23/W 22/W
4BQ 031/040 032/067 039/053 033/059 033/062 037/059 035/055
94/S 21/B 36/R 40/U 00/B 13/W 33/W
BHK 026/037 028/056 034/054 031/055 030/057 033/056 033/052
63/S 22/J 14/O 10/B 00/B 13/W 22/W
SHR 033/052 036/067 038/051 032/059 033/062 036/058 034/054
81/E 11/B 46/R 40/B 01/B 23/W 33/W
MT...Winter Weather Advisory in effect until noon MDT Tuesday FOR
Area Forecast Discussion
National Weather Service State College PA
1145 PM EDT Mon Mar 20 2017
A weakening cold front will pass through the region overnight.
A stronger cold front will move through Tuesday night bringing
sharply colder air for mid week. Temperatures will moderate
toward the end of the week into the weekend.
.NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
Regional radar still shows the remnants of an MCS diving SE
through southern Ohio into WV and eastern KY. To the north
rain showers are becoming a little better organized over Ontario
and the lower Gr Lakes. The HRRR still brings a slug of rain
into the region mainly between about 11PM and 4AM, keeping the
areal coverage limited and the QPF on the low side. Showers will
tend to dissipate toward morning leaving little more than
spotty drizzle. Overall I knocked POPS down a bit to better
match latest timing.
Temps should be mild overnight, running in the 30s. The coldest
air up north could lead to a rain/snow mix as the precipitation
tapers off late. Little or now accumulation is expected.
.SHORT TERM /7 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
High pressure will begin to build in for Tuesday. Clouds will
likely hang tough over the region for much if not all of the
day, but temperatures should be able to rebound a bit and
return to near or slightly above normal.
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Secondary/arctic front drops SSE across the region later Tuesday
night/Wednesday morning with much stronger cold advection in the
upper boundary layer (thanks to nearly orthogonal NW-NNW flow
of 25-35 kts to the isotherms in 925-850 mb layer).
The base of the subsidence inversion will be quite low (only
around 4 kft AGL) and the fetch over the upstream glakes will be
relatively short. So, the chance for significant LES will be
rather low. However, the shallow strato cu deck will reside
within the favorable DGZ thermal ribbon of -12 to -18C, so
light accums of snow (up to around an inch) should occur across
parts of the NW mtns and Laurel Highlands with just flurries
The coldest air we`ll likely see until sometime later next fall
will occur Wednesday into Thursday. Daytime highs and overnight
lows will be 12-15F below normal. Mins early Thursday will range
from near 10F along the PA/NY border, to the lower 20s in the
larger metro areas in the Lower Susq Valley as a nearly 1040 mb
sfc high drifts overhead. Some lows in the upper single digits
will be a good possibility in the perennial cold spots up north.
After a partly to mostly sunny and still rather cold day
Thursday (by late March standards), clouds will increase
Thursday night into Friday as a warm front drifts NE across the
commonwealth. Sfc temps, and temps aloft (850 mb) will be a few
to several deg C above freezing, so any light precip that occurs
with this front will be light.
The Warm front will likely lift into New York State and the warm
sector should expand NE cover the entire CWA Friday afternoon
through most of Saturday with temps surging well into the 40s to
around 50F Friday, then into the lower 50s (north) to lower 60s
(south) on Saturday.
Timing and location of the deep cold air and associated 1040+
sfc high over southeastern Canada will play a key role in the
storm track of a southern stream wave that will be sheared east
from the Mid Miss Valley late Saturday...through the Ohio River
Valley...Central Appalachians and Mid Atl Coast Sunday through
Pops for rain/showers will increase Saturday night through
Sunday night, but capped them off in the likely range at this
Shallow cold air could backdoor us from the NE later in the
weekend per the continued/consistent trend of the 12Z EC and
GEFS. This could lead to some precip type issues across
northern PA at a minimum.
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
Low pressure entering the Ohio Valley this evening will track
south of Pa late tonight, spreading rain showers and falling
CIGS across the region. Latest HRRR and SREF probability charts
suggest IFR conditions are possible between 10Z-14Z at JST/BFD,
MVFR conditions are likely at UNV/AOO and perhaps no sig
reductions at the lower elevations airfields of eastern Pa,
Any showers should push east of the region around 12Z, as the
low pressure system passes off the east coast. However,
residual low level moisture ascending the Allegheny Mountains
could create lingering MVFR stratocu at BFD/JST into early
afternoon. The arrival of high pressure and drier air should
result in widespread VFR conditions by late in the day, even
Wed-Thu...No sig wx expected.
Fri-Sat...Showers/reduced CIGS possible, mainly BFD.
NEAR TERM...La Corte
Area Forecast Discussion
National Weather Service Cheyenne WY
553 PM MDT Mon Mar 20 2017
.SHORT TERM...(This evening through Wednesday night)
Issued at 230 PM MDT Mon Mar 20 2017
Forecast challenges deal with precip chances through the short
Currently...Frontal boundary lays across the southern CWFA,
generally from Cheyenne to Shirley Basin to just north of Rawlins
this afternoon. AFternoon humidities have been fairly high
compared to recent days north and east of the front. Looking at RH
values ranging in the mid to upper 30 percent for these areas.
South and west of the front, upper teens to low 20 percent reports
were common. Radar not showing a whole lot of activity at this
time, but short range guidance shows this ramping up later this
afternoon. Water vapor imagery showing a pretty strong low off the
coast of northern California around 40N 138W that we need to be
watching in the long term.
Latest run of the HRRR shows a band of showers and isolated
thunderstorms developing towards 00Z this afternoon. This looks to
be basically along the front from Alliance to Wheatland to maybe
Casper. Convection stays north of Cheyenne through the overnight
hours, so kept the city fairly dry for tonight. Front continues to
slowly lift north through the overnight hours. Though I did not
add fog into the forecast for the northern Panhandle and Niobrara
County, the evening and mid shift will need to monitor conditions
overnight. Forecast soundings showing more of a stratus event
than a fog event.
Front does south southwest again Tuesday afternoon, so think
Cheyenne`s best chance looks to be the tomorrow afternoon.
Westerly mid level flow returns Tuesday night into Wednesday,
which will force the surface front eastward into the Panhandle.
700mb winds increase to 35-40kts Wednesday afternoon, leading to
breezy to locally windy conditions across southeast WYoming.
.LONG TERM...(Thursday through Monday)
Issued at 230 PM MDT Mon Mar 20 2017
Main focus this period will be with the system that will be moving
across the central Rockys late Thursday through Friday. Models
have shifted the track a bit farther south thus the main effects
from this system look to be over the southeast part of the CWA.
main problem will be where pcpn transitions to snow...and how
much. Not much cold air associated with the system so snow looks
like it will be highly elevation dependent. Snow should fall over
the mtns by late Thursday then reach out into the adjacent higher
plains Thursday night into Friday morning. Right now looks like
several inches of snowfall over the mtns with lesser amounts over
the adjacent higher plains of southeast Wyoming. Have undercut
guidance temps as they look too warm especially on Friday given
clouds and pcpn. Rather windy as well Friday. Clearing friday
night with dry and warmer conditions Saturday as an upper ridge
slides across the area. Progressive pattern brings the next system
to the CWA Sunday with rain and snow showers. Short break early
Monday before the next upper system approaches.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 553 PM MDT Mon Mar 20 2017
Scattered light rain showers are moving east across the forecast
area this evening and will continue to do so through 09Z or so.
Winds across the plains are generally out of the east behind the
cold front that moved through earlier. Cigs may drop to MVFR/IFR
across the plains in shower activity overnight, and as easterly
upslope flow persists through Tuesday morning. Southwest winds
look to gust to 25-30kts at KLAR and KRWL Tuesday afternoon.
Issued at 230 PM MDT Mon Mar 20 2017
A more unsettled and wetter weather pattern setting up for
southeast Wyoming and Nebraska Panhandle. Showers and isolated
thunderstorms are possible this afternoon and this evening as a
stalled out front interacts with upper disturbances to produce
increased chances for wetting rains. This front will stay in the
area east of the Laramie Range through Wednesday before being
shifted east. For late in the week, a Pacific low pressure system
is forecast to track through Colorado, bringing at least a
heightened threat for mountain snow and widespread rain to areas
along and east of the Laramie Range. In the meantime, afternoon
humidities are expected to fall to the low 20 percent range east
of the Laramie Range for Tuesday and Wednesday with fair to good
overnight recoveries. Fire weather concerns are therefore low
through the upcoming week.
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
504 PM PDT Mon Mar 20 2017
Extend the wind advisory for 3 more hours through 8 pm this
evening for elevations above 2000 feet in SW Humboldt, and
Humboldt Interior. High resolution model HRRR shows that the 925
mb level winds of around 45 to 50 kt will persist through this
evening before diminishing. This means gusty winds of 40 to 45 mph
for ridgetop locations through this evening. /RCL
.PREV DISCUSSION... /issued 339 PM PDT Mon Mar 20 2017/
SYNOPSIS...A frontal system will bring periods of rain tonight
through Tuesday. Cold air aloft will result in a slight chance of
thunderstorms on Tuesday. A stronger front will arrive Thursday
night through Friday, resulting in another round of rain.
DISCUSSION...A front just offshore has been producing light to
moderate rain through most of the day today. The greatest rain
amounts have been over Del Norte and Humboldt counties where a
moisture plume has been streaming into the area from the southwest.
We will see a brief rain break early this evening, before another
front currently crossing 130W merges with the first boundary
tonight, resulting in more widespread rain. Locally heavy rain
will be possible late tonight as the two boundaries merge and an
upper trough pivots toward the North Coast. Instability parameters
look favorable for some low topped thunderstorms late tonight,
primarily over the waters and near the coast.
Winds have been borderline for an advisory, with gusts from
42 to 47 mph over the higher elevations of Humboldt county this
afternoon. ARW continues to indicate the potential for gusts up to
50mph over the higher terrain of Humbodlt county through early
evening. Therefore will continue with the wind advisory. Breezy
conditions will continue tonight into Tue. Advisory level gusts
appears unlikely for Tue.
Instability and moist onshore flow will result in occasional
showers Tue through Tue night. The potential for low topped
thunderstorms looks best over the waters, however with daytime
heating and steep mid level lapse rates, isolated tstms may also
fire up over the interior. The threat for significant hail
accumulations appears to be low due to the relatively high
freezing levels and low buoyant energy for strong updrafts. The
main threat will be lightning activity.
The upper trough will finally pass across the area on Wed. There
will probably still be showers on Wed, though the frequency and
coverage should decrease. Ridging aloft Wed night into Thu morning
will result in a period of dry weather. With moist ground
conditions, light winds and partially clearing skies, there will
probably be some fog in the interior valleys Wed night.
A fairly strong front will approach Thursday night and bring yet
another round of rain by Friday morning. A period of moderate to
heavy rain appears probable as the front moves east across the
area. More rock and mudslides are possible during this time frame.
Snow levels should remain relatively high during the peak of the
rain, above 5kft. Strong wind gusts will also be a factor with
this front. Gusts around 50-60 mph will be possible as a low
level jet develops along/ahead of the front Thursday Night.
Shortwave ridging and drier conditions should follow on Saturday
before another front brings another threat of rain for Sunday and
perhaps into Monday.
AVIATION...A low pressure system will move through the region
today and tonight bringing periods of rain and gusty winds. MVFR
will generally prevail with periods if IFR in heavier rainfall. In
addition to the gusty surface winds, even stronger winds are
anticipated just off the surface, which will result in some wind
shear at the coastal terminals. Rain will decrease to showers
early Tuesday morning and winds should weaken both at the surface
and aloft. /RPA
MARINE...A low pressure system is bringing gusty south winds to
the Northwest California coastal waters today. Buoy observations
are indicating gusts to nearly gale force in the southern waters
and these gusts should spread north over the next few hours. At
this time only localized gusts to 35 kt are expected around Cape
Mendocino and Point Arena, so advisory products should suffice.
The seas will build in response to the winds and become steep at
around 9-10 ft at 6-8 seconds by this evening.
Winds and seas will subside late tonight into Tuesday morning only
to ramp up again in the northern waters Tuesday afternoon. Another
round of small craft winds are anticipated with a few gusts
exceeding 30 kt.
Winds will become significantly lighter Tuesday night through early
Thursday as an upper level ridge moves overhead and the surface
pressure gradient becomes weak. Seas will subside back to 5-6 feet
by Thursday morning. However, as has been typical this winter, this
respite will be short lived as another strong cold front is forecast
to approach the waters Thursday and move through Thursday night into
early Friday. Again, strong south winds are anticipated with the
potential for gales along the leading edge of the frontal boundary.
Gale watches may need to be issued Tuesday night or Wednesday for
the Thursday-Friday system. /RPA
CA...Wind Advisory until 8 PM PDT this evening for CAZ104>106.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 10 PM PDT this evening for PZZ450-455.
Small Craft Advisory until 3 AM PDT Wednesday for PZZ470.
Small Craft Advisory until 3 AM PDT Tuesday for PZZ475.
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Area Forecast Discussion
National Weather Service Louisville KY
1107 PM EDT Mon Mar 20 2017
Issued at 1052 PM EDT Mon Mar 20 2017
Have trimmed back chances for showers and isolated thunderstorms
this evening based on high-res model trends. Some light echoes have
begun popping up behind the front in southern Indiana, but have
struggled to maintain themselves. Latest HRRR guidance suggest we
could see some light showers develop toward the early morning
hours in Central KY. With SPC mesoanalysis showing some elevated
instability, could see isolated thunderstorms as well ahead of the
front. Otherwise, rest of forecast is on track.
.Short Term (Now through Tuesday Night)...
Issued at 259 PM EDT Mon Mar 20 2017
The precipitation from this morning has finally mostly moved out of
the region. Warm air advection through the day has contributed to
temps rising into the 70s across south and west central KY this
afternoon while much of the Bluegrass remains near 50. However,
winds have shifted to southerly across the whole area and become
gusty this afternoon. This will lead to a surge in temps through the
remainder of the afternoon for the cooler areas. Still think that
most will see highs at least in the 60s today, though it will come
later in the afternoon. Mid to upper 70s for highs are in reach for
southwest central KY.
As far as precipitation goes, a weak surface low will cross the
region this evening and a cold front will sag south overnight.
Showers and a few storms will accompany these features, mainly after
0Z tonight. The best chance for precipitation looks to be over the
Bluegrass, but even there it still looks to remain scattered in
nature. Soundings do show steep mid level lapse rates with a strong
inversion at the surface. There looks to be quite a bit of elevated
instability, on the order of 1000+ J/kg CAPE, so if storms do form,
some hail will be possible.
Precipitation should mainly end from the north overnight as the
front sinks southward. A few showers and storms could linger into
tomorrow morning across south central KY, but most areas look to be
dry. Another shortwave moving through the upper level flow will
approach and move through tomorrow afternoon into the evening. This
will bring a renewed chance for showers and storms, particularly
across south central KY, though the area of highest coverage does
look to be a bit further to the south than in previous model runs.
The storms across south central KY could become strong to marginally
severe in the afternoon and evening with hail and some gusty winds.
Precipitation looks to finally end tomorrow night.
Temperatures tonight will remain on the warm side ranging from the
upper 40s across southern IN to the mid to upper 50s across south
central KY. Highs tomorrow look to be in the 60s with lows back into
the 30s tomorrow night.
.Long Term (Wednesday through Monday)...
Issued at 308 AM EDT Mon Mar 20 2017
Mainly dry weather is expected from midweek through the end of the
work week. Surface high pressure will build in from the north on
Wednesday. Temperatures will be on the cooler side Wednesday with
highs in the mid 40s to mid 50s. Through the end of the week, upper
level ridging will build in. A warm front will move north across the
region on Thursday. The GFS/ECMWF then show a disturbance rounding
the top of the upper ridge on Thursday evening and possibly bringing
showers to the Bluegrass region. Will carry just low end pops with
this due to the uncertainty associated with it. Temperatures will
quickly rebound back into the 60s to lower 70s by Friday.
The weekend continues to look wet as a deep upper level low slowly
approaches and moves from the Midwest into the Great Lakes region.
Showers and storms look to move in from the west Saturday morning as
we sit solidly in the warm sector of the system. Precipitation will
overspread the area through Saturday into Saturday night. We could
still see scattered showers Sunday behind the front. These look to
move out Sunday night. The more spring-like temperatures will
continue this weekend with highs in the 60s to lower 70s.
.Aviation (00Z TAF Update)...
Issued at 750 PM EDT Mon Mar 20 2017
Regional radar shows two clusters of storms, one passing to the
southwest of BWG and the other to the northeast of LEX. In between
these two areas of convection, VFR conditions will prevail, at least
over the next two hours. A surface boundary that has been slipping
south is currently draped over the Lower Ohio Valley. Expect
ceilings to gradually lower to MVFR and then to fuel alternate
levels overnight. Isolated showers and storms are expected to flare
up as well, primarily affecting SDF and LEX.
Post-frontal low level moisture is expected to maintain low ceilings
into Tuesday morning. Fuel alternate levels look likely, especially
after 05z, and a dip to IFR isn`t out of the question. Winds will be
erratic overnight with the cool front moving through, but around 5
kts or less.
An increasing northerly breeze behind the front will help ceiling
and visibility restrictions lift during mid to late morning. Shower
and thunderstorm chances will return to BWG Tuesday afternoon and
Area Forecast Discussion
National Weather Service Morristown TN
940 PM EDT Mon Mar 20 2017
.DISCUSSION...Another quick update this evening to raise POPs to
account for incoming activity out of Southern Middle TN. Latest
HRRR and RAP runs bring this activity further into our CWA than
previous runs. New runs still show this activity weakening and
dissipating by around midnight. Will continue to monitor this
area of showers and storms as it moves in. Will send new zones for
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 55 77 54 64 / 20 60 70 30
Knoxville McGhee Tyson Airport, TN 49 72 48 58 / 30 70 80 20
Oak Ridge, TN 52 72 49 61 / 40 60 80 20
Tri Cities Airport, TN 49 68 45 57 / 50 50 70 20
Area Forecast Discussion
National Weather Service Raleigh NC
1030 PM EDT Mon Mar 20 2017
A warm front will push northward through the area tonight, bringing
mild air for Tuesday. A cold front will push slowly southward
through the area Tuesday evening through Tuesday night. Cool high
pressure will build into the region from the north Wednesday through
.NEAR TERM /Through Tonight/...
As of 1030 PM Monday...
Earlier update is on track. The earlier MCS over S OH has weakened
considerably as it has crossed WV and become farther removed from
the best wind fields and moisture flux. The residual area of showers
(and a couple of isolated embedded storms, although these too will
weaken) will continue a slow decrease in coverage and intensity,
following the HRRR and WRF-ARW, but still expect enough showers
across the far N and NE CWA to keep chance pops, highest near the
Kerr Lake and Lake Gaston areas. Lows from the upper 40s east to
lower 50s west. -GIH
Earlier discussion from 730 pm: Forecast was updated to account for
greater shower chances across the north and NE tonight, along with
greater cloud cover (earlier increase from NW) and warmer temps
tonight. The MCS covering southern OH (including a bow echo tracking
along the Ohio River) is on track to cross WV into VA over the next
several hours, following the mean steering flow, although as it does
so, it will move out of both the low level theta-e ridge and low
level jet nose, and this loss of support should result in a decrease
in intensity and coverage of showers as it approaches far north-
central and northeast NC late tonight. That said, however, the
HRRR/RAP/WRF-ARW, as well as the latest GFS/NAM/ECMWF, all show a
batch of scattered showers crossing the NE CWA very late evening
into the overnight hours. Have raised pops late evening through
tonight from the Triangle N and E, with good chance near Kerr Lake
and Lake Gaston. This should be mostly showers by that point,
especially given the lingering lower dewpoints and cooler temps over
the NE CWA, where mid level lapse rates will still be under 6 C/km.
With a faster and greater increase in cloud from the west and NW
this evening, hindering radiational cooling, have bumped up lows to
around 50 / lower 50s, except for upper 40s east of Highway 1. -GIH
Earlier discussion from 100 pm: Low-level moisture will increase
from the W/WNW tonight as the aforementioned front progresses slowly
south/east into TN/WV/VA and low-level flow strengthens downstream
in the Carolinas. Model guidance is fairly unanimous in showing
measurable precipitation in the N/NW Piedmont late tonight (06-12Z
Tue). Model guidance is most likely picking up on remnants of the
MCC, e.g. the eastern portion of the complex as it progresses S/SE
through WV into southwest VA overnight. Alternately, strengthening
low-level warm advection may result in marginal/elevated
destabilization and a potential for elevated showers at the leading
edge of a 925 mb warm front lifting NE from Upstate SC through the
Foothills/Western Piedmont of NC between 06-12Z Tue morning. Given
the dry airmass (PWAT 0.20-0.40") currently in place east of the
mountains, confidence remains low with regard to whether or not
sufficient moistening/elevated destabilization and/or sufficient
forcing will be present to maintain lingering MCC remnants or
support the development of elevated showers late tonight. At this
time, will continue to indicate a ~20% of showers after midnight
across the W/NW Piedmont. Given broken/overcast cloud cover and a SW
breeze, expect lows Tue morning to be much warmer than this morning,
in the mid to upper 40s, coldest in the E/NE Coastal Plain. -Vincent
.SHORT TERM /Tuesday and Tuesday Night/...
As of 216 PM Monday...
A broad surface low and associated cold front progressing SE into
the Appalachians tonight will track slowly southward through central
NC as a backdoor cold front late Tue aft/eve into Tue night, in the
presence of small amplitude shortwave energy traversing the region
in NW flow aloft. Aside from elevated convection that may develop
over or propagate into portions of central NC early Tue morning,
expect dry conditions to otherwise prevail through mid Tue afternoon
given weak forcing and a strong capping inversion associated with a
pronounced elevated mixed layer (H7-H5 lapse rates ~8c/km) advecting
into the Carolinas from the west. Expect highs Tue afternoon in the
mid/upper 70s to lower 80s. By late Tue afternoon, convection is
expected to develop over and/or propagate into central NC from the
west as the cap weakens via diurnal heating and forcing strengthens
as the low/cold front progresses southward into central NC and
shortwave energy traverses the region in NW flow aloft. The latest
guidance suggests the potential for convection will be greatest
along/south of Hwy 64 between 21Z Tue afternoon and 06Z Wed morning.
Lows Tue night will be driven by cold advection in the wake of the
front, ranging from the mid 40s (N) to lower 50s (S).
Severe Potential: Very steep mid-level lapse rates, Spring
insolation and seasonable low-level moisture (dewpoints rising into
the mid/upper 50s) will yield as much as ~1000 J/kg of MLCAPE late
Tue aft/eve, in the presence of deep layer shear sufficient for
supercellular organization. With the above in mind, deep convection
that develops and/or propagates downstream into central NC Tue
aft/eve will have the potential to become severe, with a primary
threat of large hail and damaging winds. The threat for severe
weather will be greatest (relatively speaking) south of the
Highway 64 corridor between 5pm and Midnight. -Vincent
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 325 PM Monday...
Surface cold front and attendant axis of deeper moisture will push
south of the area by daybreak. Rain/showers should be exiting
southern portions of the forecast area by the morning rush hour
commute, with NW-SE post-frontal clearing during the late
morning/early afternoon, as the leading edge of the strong Canadian
high builds in from the north. Highs Wednesday a good 15 to 20
degrees cooler than Tuesday, ranging from lower to mid 50s NE to
lower 60s SW.
With the cP airmass centered over the area Wednesday night through
Thursday night, temperatures through the period will average a good
10 to 15 degrees below normal. Thursday morning looks to be the
coldest morning, with most area at or below freezing, lows in the
upper 20s to lower 30s. Highs in the 50 to 55.
The Nam is a wet outlier in the depiction of spreading precip into
the area Wednesday night and into the day on Thursday, in response
to shortwave disturbances moving through the area. The remainder of
the NWP guidance keeps this overrunning precip suppress south of the
area and thus will keep forecast dry.
The modified Canadian parent high will shift offshore on Friday, with
southerly return flow allowing for a quick moderation to 70 degree
readings by Saturday with ridging aloft keeping it dry through
Friday night and possibly through much of the day on Saturday.
Strengthening warm moist air advection on the eastern periphery of
the closed mid/upper level cyclone moving east-northeast into the
Ohio Valley will result in increasing chance of showers and possibly
a few thunderstorms late Saturday and into the day on Sunday. The
closed cyclone is forecast to gradually weaken as it moves east-
northeast, and thus the threat for severe weather is minimal at this
time. Continued mild with highs in the 60s and 70s. Lows in the
upper 40s and 50s.
.AVIATION /00Z Tuesday through Saturday/...
As of 745 PM Monday...
24 Hour TAF Period: Medium confidence of VFR through the TAF period
with SSW/SW winds becoming more variable and light overnight.
Scattered to broken clouds near 5 kft can be expected into the
overnight hours giving way to higher ceilings later Tuesday
afternoon. Light precip at the northern terminal sites is possible
between 6 and 12Z Tuesday morning as a disturbance moves along the
VA border. No thunder is expected with the precipitation at this
time. Other than a brief period of gusty winds (15-20 kts) at KFAY
late tomorrow morning into early afternoon, winds at most terminals
should remain variable between 5-10 kts.
Long Term: There will be another chance for precipitation at KFAY
just after the TAF period as a disturbance passes just south of the
forecast area. Otherwise expect mainly VFR conditions through much
of the period.
Area Forecast Discussion
National Weather Service Charleston WV
1042 PM EDT Mon Mar 20 2017
Cold front with showers and thunderstorms crossing the area.
Upper disturbance passes Tuesday night. High pressure Wednesday
night and Thursday. Warm front Friday. Cold front over the
.NEAR TERM /THROUGH TUESDAY/...
As of 1030 PM Monday...
Another PoP tweak due to shower/tstorm development over Ohio.
As of 820 PM Monday...
Updated PoPs and wind to better reflect radar trends and HRRR
guidance. Current batch of showers and thunderstorms moving
through the area is generally not causing any issues with precip
gages coming in at near a 1/2". A second band of showers is
developing over Ohio and looks to also cross tonight. Again, no
Zonal upper level flow quickly rushes impulses through the
region with on/off PoPs over the next 24 hours.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 420 AM Monday...
Tuesday morning finds a cold front at least half the way through
the forecast area, and an upper level wave moving off to the
east. The cold front slips southward, through the remainder of
the area, by Tuesday afternoon, taking any showers with it. Left
a small chance for thunder in the extreme south midday Tuesday,
just before the front moves through there.
Models show a flat wave moving across the area Tuesday Night,
bringing about a renewed chance for precipitation. Given the
sloping baroclinic zone on the north side of the front south of
the area, we are looking at mainly mid and upper level moisture
and hence light precipitation.
The colder air moving in behind the front may allow a
transition from rain to snow from north to south overnight
Tuesday night into Wednesday morning, with very light
accumulations possible in the mountains. Cloud temperatures
favoring crystal growth and dry air below the cloud base favor a
transition of any precipitation to snow during this time.
Strong high pressure featuring cold and very dry air dominates
Wednesday afternoon through Thursday, as it passes north of the
Temperatures close to central guidance including a very cold
Thursday morning, about ten degrees below normal, for a hard
freeze for any agricultural interests.
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 420 AM Monday...
Warm advection precipitation may scoot across northern portions
of the forecast area Thursday night into Friday. The retreating
cold air may hang on long enough for snow furthest east, across
The area breaks out into a warm sector Friday afternoon into
Saturday. A cold front approaches later Saturday and is likely
to cross later Saturday night or Sunday, ahead of which thunder
is possible. Low pressure approaching from the west on Monday
may lead to a continued or renewed chance for precipitation.
Have lows occurring early Thursday night as warm advection
develops overnight. Otherwise temperatures close to central
guidance, which is a little below the MEX over the weekend.
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
As of 1040 PM Monday...
Largely VFR becoming more MVFR and eventually IFR in places as
a cold front moves through though believe this forecast is a bit
pessimistic. IFR possible in tstorms, but not confident enough
to put in TAFs.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z WEDNESDAY...
FORECAST CONFIDENCE: Medium
ALTERNATE SCENARIOS: Timing of any showers or isolated
thunderstorms, and resultant MVFR or worse conditions may vary
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE TUE 03/21/17
UTC 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14
EDT 1HRLY 23 00 01 02 03 04 05 06 07 08 09 10
CRW CONSISTENCY H H L H H H H H M M M L
HTS CONSISTENCY H H H M M M M M M M H M
BKW CONSISTENCY H H H M M M L L L L L L
EKN CONSISTENCY L H H M L M H L L M H L
PKB CONSISTENCY M M H M M M H H H H H M
CKB CONSISTENCY H M M M L L M M M M M L
AFTER 00Z WEDNESDAY...
No IFR expected.
Area Forecast Discussion
National Weather Service Blacksburg VA
852 PM EDT Mon Mar 20 2017
Weak low pressure will push east across the Appalachians
overnight, triggering showers and isolated thunderstorms as a
warm front lifts across the mid Atlantic states. As the low
progresses east, a cold front will push south across the area
Tuesday as high pressure builds in from the upper Midwest for
the middle of the week.
.NEAR TERM /THROUGH TUESDAY/...
As of 845 PM EDT Monday...
MCV driven complex of showers and storms along the nose of the
850 mb theta-e axis continues to approach from the northwest
this evening and expect the initial band to cross the mountains
in the next hour or two. Appears main batch of more organized
coverage will clip the northwest as well through midnight with a
trailing line feature perhaps reaching the far southwest zones
as well before fading. Just how widespread/strong the
showers/storms will be remains iffy as evening soundings show
support for elevated convection above the dry near surface
inversion while surface instability remains about nil. Latest
HRRR tends to fade coverage crossing the ridges but doesn`t have
much of a handle on the trailing band to the southwest. Since
more of a dynamic system would expect shra/tsra to go further
than model guidance despite loss of heating. Thus upped pops a
bit sooner to categorical northwest while extending the likelys
farther south over the next few hours. Also appears feature will
exit sooner after midnight with showers fading out east with
possibly a few bands redeveloping far southwest where kept
higher pops while trimming eastern half shortly after midnight.
Some upward adjusts to temps overnight given moistening
dewpoints with lows mostly in the 40s to around 50.
Previous discussion as of 345 PM EDT Monday...
Currently keeping an eye on a complex of showers and
thunderstorms over central Indiana which are associated with a
low pressure system that is advancing up the Ohio River Valley
this afternoon. Weather forecast models are in good agreement
that this low will pass across the central Appalachians
overnight, with the associated showers and possibly isolated
thunderstorms advancing to the Interstate 64 corridor shortly
before midnight. Believe this convection will begin to diminish
as it drifts southward toward the North Carolina/Virginia state
line as winds in the wake of the cold front dragging behind the
low shift increasingly westerly and downslope. Despite frontal
passage, cold air does not yet truly enter the area, and
overnight low temperatures will hold in the 40s nearly
Through late Tuesday morning, expect residual rain shower
activity to linger along the ridges of southeast West Virginia
through the highlands of North Carolina, as well as in the
vicinity of the passing cold front south of Highway 460 across
the Piedmont. Latest forecast model solutions have become a
little faster with the passage of the front, indicating less
instability than previously called for along the southern end of
the forecast area during the afternoon where temperatures are
expected to rise into the 70s. Still, cannot rule out a slight
chance of thunderstorms from late morning through mid afternoon
across the south, though instability will be minimal. Scattering
of clouds during the afternoon will promote high temperatures
in the low/mid 70s across the Piedmont, while areas along and
west of the Blue Ridge will hold in the 60s.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 300 PM EDT Monday...
Models are trending faster and further to the south with a
west-to- east oriented frontal passage Tuesday night. Even
though models have most of the area dry by midnight, we decided
to cut PoPs by half going from 60 percent to 30 percent. The
highest PoPs remain along the VA/NC border south. The dew point
front lags behind with the colder, drier air not entering the
northern portion of the CWA (Lewisburg Wv-Lynchburg VA) until
around sunrise Wednesday morning. Therefore, leaned toward the
warmer MET guidance Tuesday night with most areas staying above
freezing with the exception of higher ridges across Greenbrier
County to the Alleghany Highlands. Moisture should be gone by
the time cold air filters into the area Wednesday to limit
accumulating snow to these ridges.
High pressure will build in from the north Wednesday. The
coldest air should not sink south until Wednesday evening as the
center of the high wedges south across the piedmont. Wednesday
temperatures will range from the upper 40s to lower 50s west to
upper 50s-lower 60s east Wednesday. Cold air Wednesday night
will send temperatures down into the mid to upper 20s across the
forecast area. We will see uniform temperatures Thursday in the
upper 40s to lower 50s as dry cool wedge engulfs the region.
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 300 PM EDT Monday...
Cool wedge of high pressure will begin to move off the VA/NC
coast Thursday night. As the center of the wedge tracks east, a
warm front will push moisture over the mountains which should
only result in an increase in cloud cover Friday and Friday
night. However, a bubble high will likely remain east of the
Blue Ridge and over the foothills and piedmont counties into
Friday night. This bubble of cool air and easterly flow will
keep high temperatures east of the Blue Ridge close to 60F while
the mountains warm into the lower to mid 60s. The wedge should
be completely erode out of the region by Saturday afternoon with
temperatures warming into the mid 60s to lower 70s across the
An area of low pressure is expected to track from the Midwest
Saturday night towards the Ohio Valley Sunday. This system has
the potential to bring severe weather to the region Sunday and
Sunday night. The track of the system and timing of prefrontal
convection into the region will be the biggest influence on how
widespread severe potential may become.
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 745 PM EDT Monday...
Slow moving front approaching from the northwest is acting as a
focus for elevated convection in the Ohio valley at nose of low
level jet. Expect the convection to sink into the region from
the north in the next hour or two, and expect enough forcing
with modestly steep mid/upper lapse rates to support mention of
thunder. The front is in no hurry to clear the region and expect
lingering showers mainly in the west to persist through most of
the overnight period. The lingering boundary will also start to
generate new convection south and west later tomorrow but it
does not appear likely to affect TAF sites so will maintain a
dry forecast for Tuesday.
The flow will become northwesterly behind the front and combine
with low level moisture to generate upslope MVFR/IFR low clouds
mainly west of the Blue Ridge late tonight into Tuesday morning.
Believe the lower cigs will hang in for most of the day in the
west, while sites east of the Ridge should become VFR toward
daybreak and remain as such through Tuesday. Expect winds to
generally remain light through the period.
Extended Aviation Discussion...
High pressure builds in for Wednesday which should improve
ceilings back to VFR.
By Thursday the high will wedge in from the northeast, so will
remain mainly VFR. It is possible that residual lower ceilings
may get trapped especially along and east of the Blue Ridge
Wednesday night into Thursday, resulting in possible MVFR
ceilings. Dry and warmer weather is expected on Friday.