Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/19/19
Area Forecast Discussion
National Weather Service Columbia SC
839 PM EDT Thu Apr 18 2019
High pressure will be located over the western Atlantic tonight.
Thunderstorms are expected Friday with the passage of a cold front.
Much cooler air will move into the area behind the front
Saturday. Conditions will moderate Sunday into the middle of
next week as another area of high pressure moves into the
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Upper trough, currently over the central CONUS, will deepen and
shift east, with an upper low cutting off over the lower
Mississippi Valley. Surface high centered well to our east will
shift east, as a surface front approaches from the west.
Associated line of strong to severe thunderstorms currently to
our west will continue to track east into GA. Warm moist
southerly flow expected ahead of the line of storms, and may
promote scattered showers late tonight mainly eastern areas.
The main line of strong storms is expected to remain west of our
forecast area through 6am.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/...
While there is still some differences in the models, generally I am
expecting the squall line/QLCS to be just west of the CSRA at
daybreak. It then should make steady progress eastward during the
day, with the main threat for severe convection in the CSRA during
the morning and the Midlands during the late morning and afternoon.
While all areas are currently under a day 2 enhanced risk, diurnal
trends would indicate a greater chance for severe weather in
the central and eastern Midlands where there will be time to
develop more surface-based CAPE. The wind fields are very
favorable for some damaging wind gusts, especially in favored
locations along bows in the QLCS. Any bows that do form have the
potential to produce brief tornadoes where low-level helicity
is locally enhanced.
There will be heavy rain with the convection as well given high PWs
at least 2 SD above normal, but given the steady movement of the
line, it seems unlikely that we will see excessive rainfall in any
one place. We may need a Flash Flood warning for our highly
vulnerable locations, but elsewhere flood advisories for ponding
of water on roads or low lying intersections should be the worst
Even away from convection, it will be breezy tomorrow with winds up
to 20 to 25 MPH (with gusts to 35 mph) ahead of the front in the
warm advection. A lake wind advisory has been issued.
The meaningful threat for severe weather will end by dark as the
squall line moves east of the area. The cold front will trail
behind by a few hours Friday evening, likely kicking up a few
showers. There will also be another bout of breezy conditions
with the frontal passage, so the lake wind advisory will stay in
effect through the evening. Temperatures will gradually fall
through the evening, then fall a little more quickly late at
night when the strongest low-level cold advection moves into the
Saturday will be unseasonably cool as 850 temps struggle to stay
above 0 C. Morning sunshine will turn to afternoon clouds in
the unstable air mass, and there is a chance of showers. Highs
will only be 60 to 65.
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Saturday night, skies will begin to clear and winds will decrease as
the low pressure area moves farther north and weakens. Unseasonably
cool air will still be in place, so min temps by morning will
be well down into the lower to mid 40s. Could even see some
upper 30s in wind protected outlying locations, but haven`t gone
that low in the grids, yet.
Sunday will be mostly sunny and milder as high pressure settles back
into the Southeastern States. Temps will rebound into the 70s during
the afternoon with light winds.
A warming trend will commence Monday and continue into the middle of
next week as a deep layer ridge sets up over the Southeast. Temps
will be as much as 10 degrees above normal, and the chances of
rain are on the low side.
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
Conditions will deteriorate late tonight and early Friday morning
ahead of the approaching cold front. Severe thunderstorms may
occur Friday. Low-level wind shear will be an issue tonight and
Friday morning. It will be windy Friday and Friday night.
Moisture will increase ahead of the cold front tonight. The bulk
of the moisture will hold off through the night. The high-
resolution models keep showers to the west of the terminals.
Mainly followed the GFS LAMP for the timing of developing MVFR
ceilings. The HRRR and LAMP suggested a surge of moisture may
move into the east part and the lowering ceilings may occur at
the OGB terminal first. Wind should limit fog. There will be an
increasing low-level jet ahead of the front. Followed the NAM
and included low-level wind shear in the terminal forecasts.
Used an average of the HRRR and ARW for the most likely timing
of thunderstorms ahead of the cold front. Strong wind shear will
be associated with the front supporting organized thunderstorms.
There will be possibility of damaging wind and hail. The bulk
of the showers should be east of the terminals later Friday
afternoon, but convergence near the front and cooling aloft
because of the upper trough supports a continued shower chance.
It will generally be windy through the end of the TAF period and
followed the GFS LAMP plus GFS and NAM Bufkit momentum transfer
tool for the wind gust forecast.
EXTENDED AVIATION OUTLOOK...Strong and gusty winds will continue
Friday night and Saturday.
GA...Lake Wind Advisory from 8 AM Friday to midnight EDT Friday
night for GAZ040-063>065-077.
SC...Lake Wind Advisory from 8 AM Friday to midnight EDT Friday
night for SCZ016-018-020>022-025>031-035>038-041-115-116.
Area Forecast Discussion
National Weather Service Caribou ME
1059 PM EDT Thu Apr 18 2019
A warm front will lift north across the area overnight. High
pressure to the east combined with a large low pressure system
to the west will keep a moist southerly flow Friday through the
weekend with rain at times.
.NEAR TERM /THROUGH FRIDAY/...
1055 PM Update: Hrly temps/dewpoints were lowered as the temps
have been slow to warm w/a sse wind in place. Some northern
sites such as Frenchville(KFVE) had some sleet at times
w/dewpoints in the upper 20s. The latest HRRR was doing quite
well showing this latest batch of rain moving across the region
adn the handling of the temperatures. Decided to lean w/the HRRR
for it precip scheme and temps for the overnight period. The
sfc analysis showed the warm front taking its lifting n toward
the region. Therefore, kept temps lower through 2 AM, and then
started to warm things up by daybreak. Stayed close to the
daycrew`s QPF into Friday morning.
A large trough of low pressure digging into the Midwest
combined with a big high pressure system off to the east will
produce a persistent southerly flow of warmer and moist air into
the region beginning overnight tonight. An initial wave of low
pressure lifting up out of the trough will bring periods of rain
across the north tonight with the increasing humidity likely
resulting in fog, especially over the old snow cover. This first
batch of rain will taper off to showers on Friday with a warm
frontal boundary stalled across the north. Low clouds will
persist Downeast with a bit of drizzle and fog still possible. A
few showers will continue across the north on Friday along the
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
Expect a cold front to become stationary across Northern Maine
Friday Night. An area of low pressure will move along this front
from southwest to northeast Friday Night into Sunday. This
system will Produce rain through the period. With high dew
points, fog is expected during night periods into mid mornings.
The combination of the fog and rainfall will produce
considerable snow melt and run-off into rivers and streams,
especially in the north where the greatest amounts of rain is
expected and where deepest snow pack exists.
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Low pressure is expected to move to the north of the region on
Monday as an upper level low pressure moves across the region
resulting in showers. Scattered showers are expected again on
Tuesday as an upper level trough moves across the northeast.
Strong high pressure is then expected to build in from the west
Wednesday and crest over the region on Thursday.
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
NEAR TERM: Conditions will lower to IFR tonight and remain IFR
to LIFR in variable low clouds through Friday.
SHORT TERM: Expect MVFR/IFR conditions Friday Night through
Monday. VFR conditions expected on Tuesday.
NEAR TERM: Winds will increase to SCA tonight and remain SCA on
Friday as south southwesterly wind picks up. Fog will become
likely as increasingly humid air moves over the waters. Seas in
response to the long southerly fetch will build to around 10 ft
tonight and remain high through Friday.
SHORT TERM: Have used the Nam to initialize winds however will
lower all model winds by 20 percent due to cold sea surface
temperature and expected strong warm advection. For Waves: A
southerly fetch is expected to persist across the Gulf of Maine
from Friday Night through Sunday. Expect waves to build to
around 8 feet/8-9 seconds then to subside to 6-7 feet on Monday
and Tuesday. Total Water Level: High tide levels are close to
highest levels of the month next few days due to spring tide
however expect wind speeds to be suppressed due to cold sea
surface temperature which in turn will reduce storm surge
potential. Therefore expect total water level to remain 1-2 feet
below minimum flood level. In Bangor fresh water run-off
continues to increase anomaly at low tide +5 to +6 feet and
also produce 1-2 foot anomaly at high tide.
A flood warning remains in effect along the Aroostook River in
the vicinity of Washburn and Wade. The gauge at Washburn is
hovering near 17 ft this evening and fluctuating indicating
some continued ice movement. Rain and continued snow melt
overnight will likely continue to add to the flow.
There is also a flood warning in effect for the Mattawamkeag
River at Mattawamkeag for minor flooding. The river is
continuing to rise and approaching 14 ft as of this evening.
Concerns turn to open water flooding over the weekend and into
next week. Rainfall amounts may exceed 2 inches in spots from
tonight through the weekend with the highest totals across the
northern half of the HSA. The combination of rain and snowmelt
is expected to cause significant river rises beginning Saturday
night and likely continuing into early next week. There is the
potential for moderate to major flooding, but the details on
just how much rain falls and how much snow melts make
predictions of the magnitude of the flooding uncertain although
there is a high likelihood that there will be some areas that
experience significant flooding. Please continue to closely
monitor the latest forecasts from the National Weather Service
for possible flood watches and warnings this weekend and into
MARINE...Small Craft Advisory until 6 PM EDT Friday for ANZ050>052.
Area Forecast Discussion
National Weather Service Charleston SC
1020 PM EDT Thu Apr 18 2019
A strong cold front will approach from the west tonight, then
sweep through the region on Friday. Low pressure over the Ohio
Valley will prevail Saturday, followed by high pressure
building into the region Sunday and into early next week.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Atlantic moisture transport will continue to increase overnight
as southerly flow strengthens and deepens ahead of the powerful
upper trough. Initially only scattered low clouds exist,
however stratocumulus will thicken overnight with the increase
in low-level moisture. Most model guidance shows a surge in
low-level dewpoints across coastal SC later tonight, along with
cooling temperatures aloft. This will yield modest surface-
based instability. The high-res guidance continues to show a
slug of moisture convergence moving off the Atlantic into the
Tri-County area after 2 or 3 am, bringing scattered showers and
perhaps a few thunderstorms into the area. Surface winds will
persist overnight, strengthening a bit toward daybreak as the
low-level jet begins to strengthen. As a result of the robust
mixing overnight, temperatures will not drop more than a few
degrees from current values.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
Friday: The focus of the short term forecast continues to be the
potential severe weather event Friday. Overall, there has been no
change to the overall dynamic setup. A deep trough is still forecast
to dig across the lower Mississippi Valley and close off into an
upper low. This anomalous setup will push impressive forcing into
the forecast area as a strong cold front moves west to east across
the forecast area. The ambient wind field is progged to be quite
impressive, producing strong shear profiles and notable low level
veering. The shear environment continues to look supportive of an
elevated damaging wind threat and isolated tornadoes. As is almost
always the case, the biggest question mark remains instability and
that will likely hinge on the timing of the frontal line of
History favors a faster timing as the convection tends
to race out ahead of the main front. The ECMWF and GFS continue to
be the faster solutions, while the NAM is a few hours slower. Also
of note, we are now getting into the window of time where the HRRR
and RAP extend into Friday morning. It`s a bit concerning that both
the HRRR and RAP are even slower than the NAM, with the RAP showing
the line of thunderstorms still west of our inland zones (Jenkins,
Candler, and Tattnall counties) at 15 UTC. The slower the line is in
getting into the area, the more the atmosphere can destabilize,
further enhancing the severe weather threat. The forecast does slow
arrival down a bit, but still depicts the line knocking on the
doorstep of southeast Georgia around 12 UTC. This would make the
main time period for severe weather for southeast Georgia roughly
from 8am-noon, then noon-4pm for southeast South Carolina. This
timing will likely need adjusting overnight as the line develops and
we can make better assessments of how various models are
initializing. As SPC notes in the Enhanced Risk severe weather
outlook, MLCAPE values of 1000-1500 J/kg are possible. This
instability combined with the ambient shear will favor a linear
convective mode with embedded supercellular elements. The line is
expected move east of the area by mid/late afternoon at the latest,
ending the severe weather threat.
Also of note, the strong wind field will produce gusty winds outside
of thunderstorms on Friday. Confidence has increased to the point
where we have issued a Wind Advisory for Beaufort, Coastal Colleton,
and the entire Tri-County region for frequent gusts to 40-45 mph.
Such winds will also be possible further to the southwest, primarily
along the Georgia coast, but confidence isn`t high enough at this
time to include in the advisory. The advisory will run from late
morning through late afternoon.
Friday night: The front will move well to the east and mid/upper
level moisture will strip out of the region. There doesn`t appear to
be much support for lingering shower activity so the bulk of the
overnight will be dry. Low temperatures should dip into the low to
mid 50s in most areas.
Saturday through Sunday: The large and deep upper low will encompass
much of the eastern CONUS on Saturday and then start to drift
eastward on Sunday. The surface low will spend much of Saturday
across the Ohio Valley, leading to a breezy and cool day with clouds
filling in from the west and northwest. Cold temperatures aloft,
around -20C at 500 mb, could help produce isolated showers during
the day, but virtually every model keeps shower activity upstream of
the forecast area. We still show a slight chance of showers but this
area has been trimmed to a smaller region. For Sunday, high pressure
will begin building in and skies will clear out. Look for Saturday
highs to range from the low 60s inland to the mid/upper 60s closer
to the coast. Then for Sunday, a nice warmup with highs rising into
the mid and upper 70s.
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Dry sfc high pressure will prevail across the region Sunday night
through the middle of next week with temps warming each day as a
mid/upper lvl ridge axis shifts over the Southeast United States. In
general, high temps in the the low 80s Monday will warm into the low
80s Tuesday, then low/mid 80s Wednesday. Overnight lows should range
in the low mid 50s away from the coast Sunday night, then mid/upper
50s inland to lower 60s near the coast Monday night, followed by
low/mid 60s Tuesday night.
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Stratocumulus will thicken overnight, particularly southern SC
as convergence increases late. Fairly good chance for MVFR
ceilings moving in off the Atlantic at KCHS a few hours prior to
daybreak, along with scattered showers.
Winds will rapidly increase during the morning at both
terminals, peaking in the late morning through early afternoon
hours. The latest timing on the line of strong to severe
thunderstorms has it pushing toward KSAV after 18Z and KCHS
after 20Z. Damaging straight line winds will be the primary
threat with this line, though isolated tornadoes are also
possible. The convection should be off the Atlantic coast by 00Z
Saturday. Flight restrictions are a near certainty with the main
band of storms but given the timing uncertainty this far out we
have yet to include specific mention of restricted vsby/cigs.
Although winds at the 1 kft and 2 kft levels will be very strong
on Friday, ample mixing down to the surface should preclude
low-level wind shear concerns.
Extended Aviation Outlook: VFR conditions should return
Tonight: Conditions will deteriorate with time tonight. As a
strong cold front approaches from the west and south winds
strengthen, Small Craft Advisory winds/seas will spread across
the coastal waters, including Charleston Harbor overnight, and
gale force gusts are expected to spread into AMZ374 overnight.
Seas 2-3 feet nearshore and 3-4 feet beyond 20 nm to start will
build to as high as 4-8 feet nearshore waters and 7-9 feet
beyond 20 nm by late tonight.
Friday through Tuesday: A strong cold front and associated line
of thunderstorms is expected to move across the local waters on
Friday. Southerly winds will increase significantly Friday
morning ahead of the cold front and confidence has increased
such that Gale Warnings are now in effect for all waters
including Charleston Harbor. Expect frequent gusts into the
35-40 knot range beginning in the morning and continuing into
the afternoon. The likelihood of gales will end from west to
east as the cold front moves through and the warnings will come
down at various times. However, all the warnings should be down
by late Saturday night. Seas will increase significantly, and
could rise into the 6-10 ft range out to 20 nm on Friday, and
9-12 ft beyond. Conditions will improve Friday night, but we
will certainly need Small Craft Advisories through Saturday
evening to account for elevated west-southwesterly winds and
seas in an enhanced pressure gradient around low pressure well
to the north. Much more tranquil conditions can be expected
starting Sunday and continuing into early next week as high
pressure builds in across the Southeast.
As thunderstorms move across the waters on Friday, strong
damaging winds and isolated waterspouts will be possible through
the day, first in the Georgia waters and then in the South
Surf Zone Hazards: Strong winds could produce high surf and a
High Surf Advisory could be needed for breakers of 5 ft or
greater. A Moderate Risk of Rip Currents is in effect Friday at
Although the tides are not expected to reach advisory criteria
with the high tide around 9 am Friday, there is a chance that
some heavy rainfall will occur around Charleston close to the
high tide which could cause some minor flooding issues.
Blow-out tides are possible along the SC/GA coast with Saturday
morning`s low tide.
SC...Wind Advisory from 10 AM to 5 PM EDT Friday for SCZ044-045-
MARINE...Small Craft Advisory until 10 AM EDT Friday for AMZ352-354.
Gale Warning from 10 AM to 8 PM EDT Friday for AMZ330-352.
Small Craft Advisory until 7 AM EDT Friday for AMZ350.
Gale Warning from 7 AM to 11 PM EDT Friday for AMZ350.
Gale Warning from 10 AM to 5 PM EDT Friday for AMZ354.
Small Craft Advisory until 4 AM EDT Friday for AMZ374.
Gale Warning from 4 AM to 11 PM EDT Friday for AMZ374.
Small Craft Advisory from 2 AM to 10 AM EDT Friday for AMZ330.
Area Forecast Discussion
National Weather Service State College PA
1111 PM EDT Thu Apr 18 2019
A slow moving cold front will push into western PA late Friday
bringing numerous showers and thunderstorms which will produce
a soaking rain. The cold front will take until Sunday to move
east of the Keystone state. It will then remain unsettled on
Easter Sunday into much of next week. Much of the time from
Sunday into mid week will be dry, but no long term dry spells
are seen at this point.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
All is gone from the radar - and from satellite, too. It will
take quite a few hours for significant clouds to work back into
the region. There is still the expectation that lower clouds and
perhaps a little drizzle/light SHRA may affect the eastern hill
tops by morning. Otherwise, it should remain by and large dry.
Perhaps only Warren County could have a passing showers before
sunrise. Temps have been jumping around a bit this evening as
the sky cleared. It is very mild for this time of year, with
current readings much above normal maxes.
An area of showers and thunderstorms is racing NE through the
NRN Mountains as of 18Z. It is along the leading edge of the low
level Theta-E gradient/warm front. The HRRR and high res NAM do
not see it so model depictions of dry weather lasting well into
the evening are not as convincing as they otherwise would be.
Regardless, with this feature moving quickly into NY, we kept
only small chances for additional showers in the forecast
Otherwise, the strong spring sunshine has melted the low clouds
almost completely away leaving scattered to broken mid and high
clouds moving quickly NE under the strong flow aloft. Visible
loops show a swirl over SW PA, a remnant MCV???
The southerly breeze will increase overnight. Most of the area
should be mild and dry in the warm sector, with the best chances
for showers being over the far W and NW after midnight.
Min temps overnight will be quite mild - in the 50s and lower
.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
Increasing deep-layer SSW flow ahead of a sharp upper trough
and an intensifying sfc low moving through the Ohio Valley will
help to transport significantly higher PWAT air into the region
priming the airmass for increasing coverage of moderate to
heavy rain and embedded thunderstorms.
Models are showing marginal instability but potent deep layer
shear ahead of the low and wavy front that will be moving into
western PA by nightfall. SPC has inched the SLGHT Risk into my
far southern counties, and the feeling is that they will likely
keep creeping the outlook northward in time.
Strong winds just off the deck and low LCL heights will produce
the threat for damaging wind gusts along with an isolated
tornado given the impressive shear and helicity.
Heavy rain will also be a threat in the increasingly soupy
airmass with the GEFS lighting up much of my eastern CWA with a
high probability of at least 2 inches of rain in 24 hours. HPC
has highlighted all of eastern PA with a slight risk of
Excessive Rain, prompting the issuance of a Flash Flood Watch
for tomorrow afternoon and evening for my eastern zones.
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Main changes were to edge temperatures up some Friday night into
Also did cut pops down in a small area on Saturday.
More concern for heavy rain than severe, as unlike last Sunday,
the upper level energy cuts off and the upper level trough
becomes negative tilt.
A deep low lifting northward across the Great Lakes will tend to
slow down and cutoff at some point late this week or early next
week. This system will pull a cold front across the area late
Friday into Saturday.
The heaviest rain Friday afternoon into early Sat is still
expected to exceed 2 inches across portions of our eastern CWA,
with 1-1.5 inches across the west.
While it will start off mild, the Easter weekend looks to be
cold and wet. Best chance of dry and sunnier conditions will be
later on Easter Sunday.
Another cold front on Monday, followed by high pressure trying
to build southward. Still some chance of showers at times, given
the front being nearby.
See hydro section below for more detail on the potential for
Overall, just minor adjustments made to the forecast.
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
VFR conditions to begin the overnight, but low clouds are
expected to begin to overspread the area towards daybreak.
An approaching storm system will spread showers and
thunderstorms into central PA Friday afternoon into Friday
night. Localized downpours are expected, and a few of the
storms could produce gusty winds. Expect widespread flight
restrictions Friday afternoon into Friday night.
Unsettled, showery weather will persist into Saturday and
possibly Sunday as well.
Sat...Widespread restrictions in the morning with some
improvement despite continued chc of showers.
Sun...Scattered showers and areas of sub-VFR.
Mon-Tue...Mainly VFR with scattered showers.
Only minor changes made to the QPF at this point.
Flash flood watch issued for Friday afternoon into Saturday
morning for eastern areas.
Earlier information below.
Rainfall from showers and thunderstorms on Fri/Fri night could
be enough to produce flooding, though mainly on tribs of the
Susq Mainstem and North Branch, where MMEFS shows 4-5 points of
concern for exceedance of minor FS.
Storm total QPF via model consensus and EFSs has decreased
slightly since 24 hours ago, but still in the 1-1.5 range across
much of Central and Western PA, with locally 2-3 inches expected
across the east between Noon Friday and noon Saturday.
Latest runs having that convective look to the precip with big
stripes of heavy/intense rain and gaps in between. No solution
in particular should be followed verbatim when it comes to QPF.
Model solutions generally keep the heaviest rain over the east,
with relatively lighter amounts elsewhere.
The larger waterways (Susq, Juniata) should be fine until at
least Saturday or Sunday if they ever get high.
Flash Flood Watch from Friday afternoon through Saturday
morning for PAZ028-036-037-041-042-046-049>053-056>059-063>066.
NEAR TERM...Dangelo/La Corte
SHORT TERM...La Corte
Area Forecast Discussion
National Weather Service North Platte NE
628 PM CDT Thu Apr 18 2019
.SHORT TERM...(This evening through Friday night)
Issued at 359 PM CDT Thu Apr 18 2019
Through tonight... Scattered showers and thunderstorms have
developed across western Nebraska today in association with a piece
of energy embedded in nearly meridional mid level flow. Strong winds
have also been reported as 50kt flow at H7 and 35kt winds at H85 are
mechanically mixed toward the surface, especially in the showers. RAP
soundings indicate nearly unidirectional flow through the
troposphere and nearly adiabatic lapse rates to H5. Stronger showers
are also dropping pea size hail, likely attributed to low freezing
and -20C levels (around 5kft and 12kft respectively). Slowly taper
PoP through the evening and end the activity shortly after sunset as
lapse rates recover, isentropic downglide takes over, and the best
mid level forcing moves east of the area. Looking at a rather cool
night with a clearing sky and lighter winds. Went with a general
model blend for lows to result in widespread lower 30s.
Friday and Friday night... The large upper ridge centered over the
Intermountain West slowly spreads onto the Plains. Downsloping winds
and noticeable WAA at H85 along with fair conditions and efficient
mixing should translate to highs in the 70s. A thermal ridge rides
off the higher terrain and into the Sandhills overnight while low
level winds remain somewhat elevated (around 10 mph). Low temps will
be milder in the lower to mid 40s.
.LONG TERM...(Saturday through Thursday)
Issued at 359 PM CDT Thu Apr 18 2019
The upper ridge pushes east over the weekend and breaks down ahead
of a digging trough and the main northern stream slowly sagging
south. The trough nearly stalls over the central US early to mid
next week. Toward the surface, a strong cold front pushes through
the area Saturday evening, corresponding with the ridge breakdown.
Overall, a warm and dry end to the week transitions to a cool and
somewhat wet Easter week.
Saturday... The heart of the H85 thermal ridge bisects the forecast
area with temps exceeding 20C and southerly flow strengthening to
around 20kts. Guidance has trended warmer, and jumped on board to
give most of southwest/central Neb. 80s for highs. A pre-frontal
trough or dryline is progged to cross the CWA early/mid afternoon,
while the cold front pushes through late evening or night. Some
thunderstorms will be possible along the front, but moisture will be
a limiting factor. The strong forcing will have to overcome remnant
dry air below H7 and dew points in the 40s. For the showers or
storms that do develop, a strong one cannot be ruled out due to
marginal instability (MUCAPE around 500j/kg) and modest deep layer
shear (up to 35 kts).
Sunday and beyond... Temperatures struggle to recover in the wake of
the front, especially with an unsettled upper pattern in place. Not
looking at persistent rainfall or a washout, but an extended period
of scattered showers. Southeast low level winds feed moisture into
the region, while isentropic upglide and mid level fgen provide
additional forcing. H85 temps around 5 to 10C should give seasonable
highs in the 50s and 60s.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 626 PM CDT Thu Apr 18 2019
Instability showers are diminishing across western Nebraska with
the approach of sunset. Expect isolated rain showers until 01Z,
with skies becoming SKC this evenning. VFR conditions the next 24
hours, with mainly thin high clouds on Friday. Gusty northerly
winds until 01Z up to 30KT, especially near any showers.
Otherwise winds will quickly diminish to below 10KT after 01Z,
with light west to southwest winds on Friday.
Area Forecast Discussion
National Weather Service Raleigh NC
1055 PM EDT Thu Apr 18 2019
Southerly flow will strengthen, between Bermuda high pressure and a
strong frontal system approaching from the west, through Friday. A
related cold front will cross central NC Friday night. A mid and
upper level low will then linger over the central Appalachians and
middle Atlantic states through the weekend.
.NEAR TERM /OVERNIGHT/...
As of 1055 PM...
Little change required to the near term forecast.
Steady sly sfc flow, sustained 7-12 mph with gusts around 20 mph
will persist into the overnight as the sfc pressure pattern tightens
between an area of high pressure offshore and an approaching cold
front. This sly flow will advect additional low level moisture into
our region, aiding in the formation of low clouds overnight. The
variably/overcast skies and the steady sly wind will result in very
mild overnight temperatures. Most locations will see low
temperatures in the mid-upper 60s.
Scattered showers will become more likely across sections of the
southern Piedmont, Sandhills and southern Coastal Plain towards
daybreak as isentropic upglide increases with the approach of a low
Looking ahead to Friday, 12Z convective allowing models verifying a
little too slow with the eastward movement of the convective system
across the Deep South, especially the 18Z NAMNest and the HiRes NMM.
The HiRes ARW and the HRRR appear to be a little closer to reality.
Based on this, the earlier arrival time of early afternoon in the
western Piedmont may be more correct.
.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
As of 450 PM Friday...
Enhanced risk for severe storms, non-convective warm sector winds
near Wind Advisory criteria, and a risk of flash flooding in cntl
A shortwave trough amplifying sharply across the cntl Plains this
afternoon will help close off a deepening mid level low over the TN
Valley region by 00Z Sat, within an increasingly phased, full-
latitude trough from sern Canada to the Gulf of Mexico. Related low
level mass response will accelerate a 60 kt 850 mb jet across the
Carolinas and middle Atlantic region through Fri afternoon-evening.
Associated strong Q-vector convergence will consequently be
maximized over cntl NC during peak heating, between 18Z Fri and 00Z
At the surface, low pressure will consolidate/deepen over ern KY/TN
through 00Z, along an arcing frontal zone draped from the Northeast
swwd to the low, then sewd across the wrn Carolinas and ern GA/FL.
Preceding that front, a band of pre-frontal convection will likely
be ongoing at the start of the period over the srn Appalachians; and
that convection and related effective front and triple point/
mesolow(s) will migrate ewd across the Carolinas through Fri
evening. The two fronts will then likely merge near or just offshore
the srn middle Atlantic coast by 12Z Sat.
In addition to the aforementioned pre-frontal QLCS likely to be
ongoing over the srn Appalachians, a plume of WAA-driven convection
streaming nwd from the Gulf Stream Atlantic will likely also be
ongoing over the NC Sandhills/Coastal Plain vicinity Fri morning.
Destabilization via advective processes may offset a lack of early
day diabatic heating owing to widespread low overcast, which may
contribute to the realization of around 1000 J/kg of MLCAPE there
through 15Z. Already strong, and strengthening deep layer flow would
favor some organization with this even early day activity, including
some rotating updrafts and risk of a brief/weak spin up.
There may then be a brief lull in that morning activity that will
subsequently continue newd and out of cntl NC, followed by scattered
cellular development over the Piedmont, immediately ahead of what
will likely be a strengthening QLCS from the early day convection
initially over the srn Appalachians. All severe hazards would
accompany any such scattered, discrete cells ahead of the QLCS, in
an environment characterized by strengthening environmental shear/
lengthening hodographs, aided by both the strengthening wind fields
aloft and increasingly backed surface flow in the warm sector. The
QLCS will then pose a risk of widespread 35-50 kt winds, locally up
to 60-65 kts, and a few mesovortices/tornadoes. Additionally,
forecast environmental parameters suggest the potential for a
Precipitable water values are forecast to be near 1.7" - around a
monthly record high and 3-4 SD above climo. So while basin average
rainfall amounts of one to two inches are anticipated, the unusually
high PWAT values and related IVT courtesy of both that excessive
moisture and a similarly anomalous LLJ, will favor convective
rainfall rates, and amounts in especially urban areas, that may near-
exceed 1-2 FFG values over at least the NC Piedmont. A short-fused
FFA may consequently be needed, though it was the collective
decision by adjacent offices to hold off on issuance at this time.
Lastly, warm sector winds may reach Advisory criteria outside of
convection, but since this appears to be similar to most of our WAA
wind regimes in that it will be sensitive to diabatic and mesoscale
influences (clouds/early day convection), such issuance will
similarly be passed to subsequent shifts as those details emerge.
A diminishing chance of showers will linger overnight, as we remain
under the influence of the dynamic upr low/trough, but any severe
risk should move east of cntl NC by 10-11 PM. Post-frontal flow will
also be swly, so the incoming air mass will not be particularly
cool, and instead characterized by lows generally in the low-mid
.LONG TERM /SATURDAY THROUGH THURSDAY/...
As of 345 PM Thursday...
An upper level low will be located just northwest of central
North Carolina at the beginning of the extended and will slowly
move east through the weekend. For the remainder of the
extended global ensembles are in good agreement with above
normal heights forecast.
The long term will open up with a vertically stacked low
pressure over the southern Ohio valley slowly heading
northeast. As this occurs saturation across the northwestern
zones working in combination with cold 500 MB temperatures (-20
to -22 degrees C) will allow for scattered showers to develop.
The other concern for Saturday will be the breezy winds. Cold
air advection with a tight pressure gradient will bring
wind gusts in the 20 to 30 MPH range. High temperatures
Saturday will be in the lower 60s across the northwest to mid
60s further southeast. Wrap around showers will persist through
Sunday as the upper level low will be slow to eject. Sunday
evening the upper level low will only be located over Maryland
with 1000/850 mb thicknesses on the rise.
Monday into Tuesday heights will rise across the eastern United
States with weak PV washing over the area with mostly dry
conditions expected. Late Tuesday height falls across the
Midwestern United States will slowly progress east. Model run to
run consistency here has been low the last couple days. In
particular, the GFS now has energy across the Midwest heading
east and closing off into an upper level low. This allows the
wave over southeastern Canada to quickly exit east. How does
this affect central North Carolina? The GFS solution pushes a
weak cold front through the region Wednesday morning with a
return of precipitation chances. The ECMWF cuts off the energy
across New Mexico allowing the upper level disturbance over
Canada to dig further south. This pushes the front well south
through the area, with precipitation returning Wednesday
evening. The ECMWF solution looks to be an outlier given
previous runs, but either way have increased the spatial
coverage of PoPs to account for this.
.AVIATION /00Z FRIDAY THROUGH WEDNESDAY/...
As of 750 PM Thursday...
24 hour TAF period: Expect VFR conditions to start the TAF period,
however MVFR cigs will fill in across central NC in the 04Z-08Z time
frame. Winds should remain fairly strong overnight, which may
inhibit cigs below 1000 ft to develop. However, given the chance
some brief periods of IFR cigs could develop, have included mention
via a tempo for the pre-dawn hours. Southerly winds will remain
around 10 kts overnight, with intermittent gusts to 15-20 kts. Gusts
will become more frequent after sunrise, increasing along with the
sustained winds. Largely expect sustained winds of 12-15 kts with
gusts of 20-25 across the area through the day.
The big forecast question will be the timing and location of the
showers and thunderstorms, of which two rounds are expected. The
earlier showers and storms will occur mainly at KRDU, KFAY and KRWI
in the 12Z-16Z range, ahead of the more pronounced and much stronger
line of storms. The second round will push across central NC from
west to east between 18Z and 03Z or so. Best guess of timing is as
follows; 18Z-22Z at KINT and KGSO, 19Z-23Z at KFAY and 20Z-03Z at
KRDU and KRWI. These storms could be strong to severe with the
chance of producing wind gusts to 35 kts or more and possibly
tornadoes. Expect the usual reduced visbys and cigs to accompany
them as well. -KC
Looking ahead: A cold front will cross cntl NC early Fri night, with
a wind shift to swly and continued breezy conditions for much of the
night. In such, somewhat atypical regimes of post-frontal swly flow,
low level drying is not as significant as the climatologically more
typical wly or nwly post-frontal flow regimes; and as such, some
patchy MVFR ceilings may linger through early Sat. Otherwise, the
lingering presence of a mid-upr level low in the vicinity of the
Appalachians will maintain a risk of mainly diurnal showers and
storms Sat-Sun. -MWS
Area Forecast Discussion
National Weather Service Tallahassee FL
809 PM EDT Thu Apr 18 2019
...ENHANCED RISK FOR SEVERE WEATHER STILL ON TRACK LATER THIS
EVENING THROUGH FRIDAY MORNING...HAVE MULTIPLE WAYS OF RECEIVING
Gonna be a busy evening and overnight across the tri state region
as a severe squall line is anticipated to move across the area.
The environment is becoming more suitable for severe weather with
each passing hour and expect the low levels to moisten up as the
LLJ strengthens this evening. Squall line extends from Mobile to
Birmingham and moving northeast around 40 MPH. Expect this line to
encroach on our western areas in a few hours. Threats remain
damaging winds and isolated tornadoes.
.PREV DISCUSSION [650 PM EDT]...
.NEAR TERM [Through Friday]...
A widespread severe weather event is still on tap for late tonight
into Friday morning. Guidance is in good agreement in bringing a
squall line across the area as a deep upper trough moves into the
eastern half of the U.S. Strong to severe storms are currently
ongoing across Louisiana and Mississippi within a large MCS forced
by the lead shortwave. This shortwave will lift northeast through
the evening as the MCS propagates into southern Alabama and the
western Florida Panhandle. This will bring a threat of damaging
winds and isolated tornadoes supported by substantial deep (50+kt)
and low-level (40+kt) shear along with sufficient instability
(MLCAPE 1000-1500j/kg). Outside of QLCS tornadoes, the threat for
stronger supercellular tornadoes is contingent upon the
development of discrete cells ahead of the main squall line. It is
still unclear if such cells will develop, so this will continue
to be monitored.
There is some potential for the line to weaken or become a bit
disorganized during the overnight hours as is moves through the
Panhandle and SE Alabama, with the influence of the lead
shortwave diminishing. However, a trailing shortwave will move
through the base of the trough by morning, resulting in the
strengthening of the low-level jet across the Big Bend into south
central Georgia. This may lead to reintensification of the line
as it moves through the eastern half of the area. Regardless of
any possible weakening, the kinematic environment will support
widespread severe wind gusts and isolated tornadoes across the
entire forecast area. Some higher end (60-70kt) gusts cannot be
ruled out with the most intense cells/segments.
Timing-wise, the line is forecast to enter the western zones
between midnight and 2am, before exiting to the east by mid to
late Friday morning.
.SHORT TERM [Friday Night Through Saturday Night]...
A cooler and drier airmass will push into the region behind the
exiting cold front. Expect lows in the 40s Saturday and Sunday
mornings with highs on Saturday mostly in the mid to upper 60s.
.LONG TERM [Sunday Through Thursday]...
Quiet weather will return following the exit of the deep trough and
associated front. Building high pressure will allow highs in the
upper 70s to warm into the low 80s, with lows warming from the upper
40s to the low 60s. The next system won`t approach the region until
[Through 00Z Saturday]
Strong to severe squall line will cross over the tri state region
overnight into Friday morning. Timing of the line seems fairly
consistent and used the HRRR and NAM for timing. Again, not much
change in timing from the previous TAF set. Did increase the
predominate wind speeds during the TSRA line and that may be
conservative. Will metwatch and amend as needed. Expect MVFR/IFR
cigs/vsbys to accompany this line. Also added stronger gradient
winds in the late morning through afternoon hours well behind the
convective line as winds shift to the northwest.
Winds and seas will continue to increase overnight ahead of the
approaching cold front. Small Craft Advisory conditions are
expected. While a few gusts to Gale Force are possible, this will
mainly be associated with the thunderstorms moving through the
waters, so have not upgraded to a Gale Warning. Winds and seas
will remain elevated through Friday before gradually diminishing
through the weekend. Light winds and low seas are expected for the
first half of next week.
A line of thunderstorms will move through the region tonight and
Friday morning. High dispersions above 75 are likely Friday and
Saturday Otherwise no fire weather concerns.
Rainfall amounts will generally be in the 1 to 2 inch range with
the system tonight and early Friday. This should not cause any
widespread issues with flooding or river rises.
.SPOTTER INFORMATION STATEMENT...
Spotter activation is requested. Spotters should safely report
significant weather conditions and/or damage by calling the office or
tweeting us @NWSTallahassee.
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 65 75 49 70 46 / 90 90 20 0 0
Panama City 64 69 53 67 53 / 100 60 20 0 0
Dothan 60 67 46 66 45 / 100 60 20 0 0
Albany 66 72 49 66 47 / 90 90 20 0 0
Valdosta 65 74 48 66 46 / 70 90 20 0 0
Cross City 66 77 54 70 49 / 60 90 20 0 0
Apalachicola 65 71 53 67 52 / 100 80 20 0 0
FL...Coastal Flood Warning from 2 AM to 5 PM EDT Friday for Coastal
High Rip Current Risk through late Saturday night for Coastal
Bay-Coastal Franklin-Coastal Gulf-South Walton.
High Surf Advisory until 2 AM EDT /1 AM CDT/ Saturday for
Coastal Bay-Coastal Gulf-South Walton.
Coastal Flood Advisory from 2 AM to 5 PM EDT Friday for Coastal
Franklin-Coastal Jefferson-Coastal Wakulla.
GM...Small Craft Advisory until 8 PM EDT /7 PM CDT/ Saturday for
Apalachee Bay or Coastal Waters From Keaton Beach to
Ochlockonee River FL out to 20 Nm-Coastal Waters From
Ochlockonee River to Apalachicola Fl out to 20 Nm-Coastal
waters from Suwannee River to Keaton Beach FL out 20 NM-
Coastal waters from Mexico Beach to Apalachicola FL out 20
NM-Coastal waters from Mexico Beach to Okaloosa Walton
County Line FL out 20 NM-Waters from Suwannee River to
Apalachicola FL from 20 to 60 NM-Waters from Apalachicola
to Mexico Beach FL from 20 to 60 NM-Waters from Mexico
Beach to Okaloosa Walton County Line FL from 20 to 60 NM.