Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/09/18
Area Forecast Discussion
National Weather Service Bismarck ND
857 PM CDT Sat Sep 8 2018
.UPDATE...
Issued at 857 PM CDT Sat Sep 8 2018
Latest surface map shows the pre-frontal boundary slowing
as it moves out of western North Dakota. This is indicated by the
lack of a windshift to the northwest behind the pre-frontal
passage, and thunderstorms continuing to exhibit a pulse type
mode. Thunderstorms have remained sub-severe and think this will
continue to be the trend overnight as Effective Shear should
remain in the 20kt to 30kt range. The RAP indicates that
southeast to southerly winds will continue for all but the far
west overnight as the convection outruns the weakening surface
trough. Will be monitoring elevated convection overnight as 850mb
southerly flow continues to meet up with a 700mb shortwave over
north central North Dakota, including the Turtle Mountains. This
is where the bulk of the showers/thunderstorms will occur. An
isolated shower or thunderstorm grazing south central ND/Bismarck
vicinity is possible by around midnight. Otherwise, should be
drier across the far west. Adjusted PoPs based on the latest
radar, HRRR and RAP13.
UPDATE Issued at 552 PM CDT Sat Sep 8 2018
Showers and isolated thunderstorms developing along a pre frontal
trough across western North Dakota per regional radar. Effective
shear generally in the 20kt to 25kt range per SPC Mesoanalysis.
Thus far, the structure of the thunderstorms have been straight
up and down and would expect this to continue far west. A 700mb
shortwave in northeast Montana will shift into northwest North
Dakota this evening which may have a play into stronger thunderstorm
development and possible isolated severe. Current forecast on
track.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 257 PM CDT Sat Sep 8 2018
The focus the next 36 hours is on marginal severe-storm risks in
western ND this afternoon and evening, and centered on the south
central into the southern James River valley late Sunday.
As of 19 UTC, a broad warm sector is in place across most of the
area south of a warm frontal zone that extends from near Regina
toward Rolla, and east of a strengthening, north-south-oriented
pre-frontal pressure trough near the ND-MT state line. Surface
observations reveal mixing-lowered dewpoints in the mid 40s F in
southwestern ND. However, subtle sheltering by cirrus decks and
modest advection of slightly greater low-level moisture content
in western SD will likely offset the impacts of mixing at least
somewhat in southwest ND the rest of the afternoon. Moreover, in
northwest ND, slightly more backed surface winds drawing on the
relatively-greater moisture content marked by surface dewpoints
in the lower to middle 50s F in central ND, and greater cloud-
cover-related sheltering of the boundary layer will likely aide
in the maintenance of higher boundary layer moisture content. The
net effect should be a north-south axis of weak MLCAPE ranging
from 500-1000 J/kg in western ND this afternoon and early evening
as forecast by most model guidance including recent RAP cycles.
Forecast soundings suggest that MLCIN will not be minimized until
late afternoon, but GOES-16 visible satellite imagery reveals
gradually-deepening cumulus near the surface trough in eastern MT
concurrent with increasing confluence in surface wind fields and
an approaching shortwave trough, suggesting that initiation will
indeed occur in time. Having said that, disparity exists in
various CAM cores, with recent ARW-core HRRR simulations and NMM-
based HREF members more aggressive with convective initiation than
ARW-based members of the 12 UTC HREF, including the NSSL WRF and
EMC WRF-ARW. The consensus of this guidance supported PoPs of 20
to 40 percent in western ND in the late afternoon and early
evening, and then over central ND tonight. We are increasingly
skeptical of the ability for convection to be maintained in any
organized fashion into the central part of the state, though, as
weak background forcing will be in place as the synoptic-scale
pre-frontal trough is expected to only slowly advance eastward.
Moreover, boundary layer cooling is likely to be ongoing by the
time convection is able to propagate into central ND, further
reducing already-weak bouyancy.
We are still advertising the risk of a few strong to marginally
severe storms in western ND through this evening in respect to
steep low- and midlevel lapse rates and effective-layer shear on
the order of 30 kt in support of multicellular storms. Given the
orientation of deep-layer wind fields to the surface trough, the
initial convection may be semi-discrete, though the tendency for
outflows to spread from convection given a dry and deeply-mixed
boundary layer and multicellular organization may tend to yield
upscale growth in time, before updrafts weaken by mid evening.
On Sunday, a shortwave trough moving through southern Canada is
expected to shift a cold frontal zone eastward, but the buoyant
sector will likely still encompass areas along and southeast of
a line from Harvey to Bismarck/Mandan and Lemmon in the mid to
late afternoon. The consensus of 12 UTC models calls for around
1000 J/kg of MLCAPE given surface dewpoints in the lower 60s,
and effective-layer shear may approach 30 kt. That will support
another marginal risk of severe storms in south central ND into
the southern James River valley. Highs will be cooler area-wide
(generally 75 to 80 F), and given the potential for cloud cover
heralded in forecast soundings, there is some uncertainty with
regard to whether advertised instability will be realized. That
being said, the consensus of both convection-parameterizing and
convection-allowing model guidance strongly supports storms in
the late afternoon and evening.
.LONG TERM...(Sunday night through Saturday)
Issued at 257 PM CDT Sat Sep 8 2018
An active weather pattern is expected in the long term forecast
period, with near or slightly above temperatures favored along
with a few chances for showers and thunderstorms.
The 500 mb pattern is forecast to be characterized by a mean
trough in the northwestern United States in between positive
height anomalies in the northeast Pacific and the East Coast.
The 00 and 12 UTC global deterministic and ensemble guidance
suggests one shortwave trough and attendant cold front likely
crossing the region late Tuesday. Given that, the Monday and
Tuesday time frame could be the warmest days of the week as
a response to the pre-wave warm air advection pattern. There
will be a chance of convection with this feature, though both
the GFS and ECMWF and their ensembles suggest the front will
likely be east of the local area before surface-based storms
are able to form Tuesday afternoon. Thereafter, a cooler air
mass may arrive for the midweek period.
Southwest flow is expected to strengthen by late week as the
trough in the northwest United States deepens, which may yield
increasing precipitation probabilities in western and central
ND. However, the amplitude of the synoptic-scale trough is an
uncertain forecast element at this time. The 00 UTC ECMWF and
ECMWF ensemble, and to some extent the FV3-GFS, portrayed a
much more amplified trough and resulted in warmer temperatures
and greater convective opportunities by next weekend. However,
the 00 and 12 UTC GFS and the 12 UTC ECMWF suggest a much more
progressive and less amplified pattern, and therefore they are
simulating a cooler regime, especially by late next weekend. For
now the the multi-model consensus is the most reasonable forecast,
which calls for highs around 70 F by Friday along with modest
PoPs.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 552 PM CDT Sat Sep 8 2018
Showers along a pre-frontal trough will affect KISN/KDIK/KMOT with
a tempo group added to these terminals through 06z Sunday. A vcsh
at KBIS and KJMS for the remainder of the tonight period. Low
Level Wind Shear will affect KMOT from 02Z through 15Z Sunday. An
are of mvfr clouds are forecast into KBIS/KJMS from 12z Sunday
until 16Z at KBIS and 21z Sunday at KJMS. Expect a round of
showers/thunderstorms developing Sunday afternoon and evening
between KBIS and KJMS. Low clouds lingering into KJMS may Details
on this still too far out.
&&
.FIRE WEATHER...
Issued at 257 PM CDT Sat Sep 8 2018
Near-critical fire weather conditions are occurring in southwest
ND this afternoon due to strong south winds and relative humidity
values as low as 20 percent in some areas. However, cloud cover is
increasing from the west and will likely temper conditions during
the late afternoon. That, combined with adjective fire danger
ratings in the moderate category in many areas, kept us from
issuing a Red Flag Warning.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...KS
SHORT TERM...CJS
LONG TERM...CJS
AVIATION...KS
FIRE WEATHER...CJS
Area Forecast Discussion
National Weather Service Columbia SC
1037 PM EDT Sat Sep 8 2018
.SYNOPSIS...
A weak cold front will approach from the north late tonight but
likely stall across North Carolina on Sunday. Expect a continued
chance of mainly afternoon and evening thunderstorms next few
days with the chance for scattered thunderstorms with near
normal temperatures. Tropical Storm Florence could affect the
weather by the second half of next week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Weak upper-level ridging continues across the area. A cold front
is forecast to remain just north of the area in North Carolina
overnight. Expect most convection associated with the front will
remain north of the forecast area as indicated by the HRRR. Have
forecasted just slight chance pops in the north part. High low-
level moisture in the low-level southeasterly flow combined
with nocturnal cooling may result in fog toward sunrise. SREF
probabilities were highest in the southeast section. Expect low
temperatures again in the lower 70s.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
The area will remain in the warm sector ahead of a low pressure
system Sunday and Monday. Despite moist southerly flow, mid-
level ridging will continue to limit convection Sunday. The
greatest chances for storms will be to the southeast along the
sea breeze, and across the Upstate closer to the front. As the
cold front approaches from the west Monday, precipitation
chances should increase, and could become likely from the central
Midlands westward. Models also give some indication that a
shortwave trough could move up from the southwest, increasing
convection across the eastern Midlands as well.
Temperatures will remain above normal through this period with
highs in the low to mid 90s and lows around 70.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
The big unknown at this point for the longer term period
continues to be Tropical System Florence. Please refer to the
NHC for the latest track and intensity guidance. Much
uncertainty exists due to the unknowns surrounding the final
track of the hurricane. Have kept a chance of convection each
day per model consensus and latest WPC guidance. Have also
leaned towards WPC for wind guidance.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
VFR through 06Z. There is some potential for some fog during the
early morning, although cross-over temperature suggest a lower
threat for radiation fog. The Lamp and HRRR suggest higher fog
probabilities at AGS and OGB terminals 08Z-13Z. Mainly VFR
conditions expected at all TAF sites after 13Z. Convection may
be a bit more widespread Sunday afternoon, so have included VCSH
at all sites.
EXTENDED AVIATION OUTLOOK...Abundant low-level moisture and
onshore flow will continue the potential for late night and early
morning stratus. Flight restrictions are possible in scattered
afternoon/evening showers and thunderstorms. Any potential
impacts from Tropical Storm Florence will not be in the area
until Thursday.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
635 PM CDT Sat Sep 8 2018
.UPDATE...
Issued at 635 PM CDT Sat Sep 8 2018
Please see the 00Z Aviation discussion below.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 357 PM CDT Sat Sep 8 2018
A quiet short term continues through the next 24 hours as a ridge
of high pressure slides off to the east, and a low pressure system
develops over Saskatchewan and slowly pushes a cold front towards
the area. Southeast winds have already developed over the area,
and should keep temperatures from dropping off as much as they did
last night, and have raised min Ts slightly. Southeast winds will
pick up for Sunday and expect highs to warm as well. Dewpoints
will increase some, and it will feel a bit more humid than today.
However, without having the front closer or having a good leading
shortwave to initiate convection have kept all pops out of the
forecast area for the daytime.
.LONG TERM...(Sunday night through Saturday)
Issued at 357 PM CDT Sat Sep 8 2018
The main areas of focus for the extended forecast continue to be a
more active weather pattern for the upcoming week, with temperatures
near to above average.
Sunday night and Monday will have increasing chances for showers,
and possibly a thunderstorm, as a mid-level trough and attendant
surface cold front move into the Northland. Some clear skies will
linger over northwest Wisconsin through at least sunrise on Monday,
so temperatures could be a little on the chilly side due to
radiational cooling. Lows over northwest Wisconsin will dip in the
lower to middle 40s.
In general, a brief respite from precipitation is anticipated on
Tuesday before more widespread chances for precipitation return for
Tuesday night and Wednesday. Gusty southerly flow on Tuesday will
bring some warmer temperatures, with most areas seeing temperatures
nearly 5 to 10 degrees above average. Winds between 20 to 30 mph
should usher in high temperatures in the middle to upper 70s across
much of the Northland. A 35 to 45 knot low-level jet will make its
way into the region, enhancing low-level warm air advection, and
lift for precipitation as well.
Model trends are now indicating a more active pattern for the latter
half of the upcoming week, due in part to a shifting flow pattern
aloft. A large longwave trough deepens over the northwestern United
States, with large scale ridging over the eastern United States.
This ridge, along with the influence of what is currently Tropical
Storm Florence, will act to block the flow, placing the Northland
under a strong upper-level jet and west to southwesterly flow, which
will allow a series of mid-level impulses to impact the region. The
GFS, ECMWF, and GEM synoptic-scale models all show repeated rounds
of precipitation over the Northland, with some subtle differences in
the spatial coverage and timing of precipitation, but the overall
picture for this pattern appears similar. Instability during this
period doesn`t appear to be too favorable for severe storms, with
MUCAPE values generally around 500 to 1500 J/kg through the period,
although a strong storm or two can`t be ruled out. However, repeated
rounds of rainfall, and Pwat values progged by the GFS in the 1.4 to
1.9" range should provide ample moisture for a heavy rainfall
scenario, particularly if the low-level jet is in play. The most
likely time frame for heavy rainfall will be Friday into Saturday.
Generally, temperatures for the rest of the week will be in the
lower to middle 70s, still above normal for this time of the year.
The average high is in the upper 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 635 PM CDT Sat Sep 8 2018
High pressure will influence the region as it builds into western
Quebec. A developing low will move into the Northern Plains
tonight and on Sunday. Expect VFR conditions overnight. A strong
low level jet will develop across western Minnesota due to the
approaching low and departing high. This will bring low level wind
shear to INL/BRD between 06Z until approximately 14Z. Expect the
mixed layer to grow on Sunday and gusty winds to develop as the
low moves eastward on Sunday. Utilized a combination of NAM and
RAP guidance in the latest TAF set.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 47 68 50 71 / 0 0 10 20
INL 51 73 54 72 / 0 0 60 20
BRD 51 71 54 73 / 0 0 30 20
HYR 44 70 46 72 / 0 0 0 10
ASX 46 71 48 73 / 0 0 0 10
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement until 8 PM CDT this evening for WIZ001.
MN...Beach Hazards Statement until 8 PM CDT this evening for MNZ037.
LS...Small Craft Advisory until 10 PM CDT this evening for LSZ146>148.
Small Craft Advisory until 4 AM CDT Sunday for LSZ143>145.
Small Craft Advisory until 10 AM CDT Sunday for LSZ140>142.
&&
$$
UPDATE...WL
SHORT TERM...LE
LONG TERM...JTS
AVIATION...WL
Area Forecast Discussion
National Weather Service Des Moines IA
616 PM CDT Sat Sep 8 2018
.SHORT TERM.../Tonight through Sunday/
Issued at 310 PM CDT Sat Sep 8 2018
Confidence: High
Remnants of Gordon continue to exit the region to the east of Iowa
and now over Illinois/Indiana as the upper level wave shifts east,
taking the system away from Iowa within easterly flow. Ridging aloft
and at the surface will take over for the next 24 hours with gradual
return of east southeast surface winds with time. Weak cold air
advection has been making inroads across eastern Iowa this
afternoon...providing the region with a pleasant day despite mid to
upper level cloud cover lingering over the southeast half of the
forecast area at this time. By tonight the ridge axis will be
moving across the area with light winds over most of the region.
This will allow for a rather cool Sunday morning with lows in the
40s to the lower 50s. There is one uncertainty tonight in a rather
high certainty forecast...with ample soil moisture, light winds
and cool temperatures expected...fog may become an issue over
portions of our area due to radiational cooling. Hires ARW/NMM
favoring low lying river valley regions but even urban areas may
see brief period of fog between 10 to 13z. The HRRR is not picking
up on any fog potential for now By afternoon only a slight rise
in H850 temperatures is anticipated as the ridge slowly slides
east. Highs should hold in the lower 70s for the afternoon with a
few fair weather cumulus.
.LONG TERM.../Sunday night through Saturday/
Issued at 310 PM CDT Sat Sep 8 2018
Confidence: Medium to High
Main challenge for the extended will be extent of possible impacts
from several northern stream shortwaves that attempt to pull weak
cool fronts through the region. High pressure ridge axis aloft and
at the surface is anticipated to move little from the Great Lakes to
Southern Plains over the next 5 to 7 days. This is in part due to
Hurricane Florence approaching the eastern seaboard...which will
result in a slowing in the pattern...eventually developing a
blocking pattern for the central portions of the country. The
tropical system is expected to be nearing the southeast US coast
around 00z Friday of next week with some uncertainty regarding the
movement of the system thereafter. Consensus remains modest between
the operational GFS/Euro with the Euro showing a consistent signal
to bring the storm inland over the mid-Atlantic/southeast states.
Though the central US will not see any direct effects of the
storm... the track will help logjam the upper level pattern forcing
most of the western Plains shortwaves north into Canada along with a
tendency to weaken any system heading east. Tuesday and Wednesday
two weak waves will move across western Iowa with accompanying warm
air advection. The pronounced east northeast flow through Tuesday
should limit moisture over much of the region. Also the Gulf of
Mexico is essentially shut down for now as the expansive Ohio
Valley/Great Lakes ridge remains in place. The result will be
continued limited chances for rain/thunder over our forecast area
through Wednesday. Beyond Wednesday there is actually a retrogression
of the upper level pattern which will force any Plains shortwave
energy farther northwest of the area for the remainder of the
forecast period. During the period building heights and warming
H850 temperatures as southern Plains dry air moves back into the
region should promote high temperatures well into the 80s by late
week into next weekend and some adjustments to forecast highs may
be needed over the next few days. The below normal temperatures
we are seeing today will become near to slightly above normal
again with the rise by the end of the week.
&&
.AVIATION.../For the 00Z TAFS through 00Z Sunday evening/
Issued at 616 PM CDT Sat Sep 8 2018
Mainly VFR conditions expected with mainly clear skies and winds
to diminish out of the east to northeast. Could see some fog late
tonight toward sunrise so did introduce some MVFR VSBYS. Low
confidence in the fog at this time. However if the fog does
develop could see some dense fog and then VSBYS would likely fall
into IFR or lower.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
AVIATION...Beerends
Area Forecast Discussion
National Weather Service Wichita KS
650 PM CDT Sat Sep 8 2018
.SHORT TERM...(This evening through Tuesday night)
Issued at 244 PM CDT Sat Sep 8 2018
Still seeing some very light showers for areas east of the KS
Turnpike as main shortwave makes slow progress into south central
KS. Remnants of Gordon look to have shifted further east of the
forecast area today, keeping most of the heavier showers to the east
as well. Low levels remain very moist, with low clouds and stratus
over most of the forecast area, as wraparound remnant moisture
remains high. So not expecting any clearing in the low clouds until
better mid level drying associated with the shortwave moving east of
the area occurs late this evening over overnight. As with the
previous few nights, high soil moisture and very moist low layers
will probably lead to some fog formation across portions of central
KS after midnight. Latest SREF data and RAP bufkit soundings hint
that some of the fog may become dense early Sun morning, especially
near KSLN and possibly south between I-135 and the KS Turnpike into
KICT. Will let the evening shift look at things further before going
with a dense fog advisory, but the potential is there, if any
clearing occurs across central KS early Sun morning. So plan on
going with patchy/areas of fog for now.
Cloud cover will be stubborn to clear off during the morning hours
on Sun, but drying and subsidence in the wake of the shortwave
moving across the area, will lead to the low layers finally drying
out for the afternoon hours on Sunday. With morning cloud cover
temps will again struggle to climb out of the middle 70s as surface
dewpoints will remains fairly high and soil moisture will be high.
Could see another round of patchy fog for Mon morning, given the
high soil moisture from recent rainfall, especially for areas east
east of the KS Turnpike underneath the ridge axis that will be
situated over the eastern half of Kansas. So will go with a mention
of patchy fog again for late Sun night into early Mon.
Southerly flow and a warming trend will begin for Mon, as the ridge
axis moves east of the area.
Ketcham
.LONG TERM...(Tuesday through Saturday)
Issued at 244 PM CDT Sat Sep 8 2018
Dry weather is expected for most of the work week with the upper
flow becoming more zonal or slightly back out of the SW. Medium
range models show a lee side trough developing in wrn KS with a
gradually tightening of the pressure gradient as we move into the
middle of the week. This will lead to some breezy conditions across
central KS by Wed-Fri.
Ketcham
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 639 PM CDT Sat Sep 8 2018
Primary concern through Sunday morning will be low clouds and the
potential of fog.
Low level drying is finally beginning to take shape early this
evening as evidenced on satellite by an area of clearing over NE
KS. Recent surface obs in this area show VFR conditions for a
change and these improved conditions should begin to work into
central KS over the next several hours. The question, then, is
how quick does the clearing occur and will there be enough time
for BR/FG development. Given the ongoing clearing, confidence in
the development of BR/FG is increasing and the latest TAF issuance
reflects this (ie. changing TEMPO groups with BR to FM groups).
There is certainly some potential for LIFR conditions in FG
overnight, especially near KRSL/KGBD/KSLN/KHUT where clear skies
look to last the longest. We`ll closely monitor this potential and
adjust the TAFs accordingly should confidence increase. For
KICT/KCNU, it is less certain how quick the clouds will clear (if
at all at KCNU) and the BR/FG potential is lower there for now.
Low clouds and any fog should begin to mix out from west to east
on Sunday. - Martin
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 60 76 58 80 / 10 0 0 0
Hutchinson 58 76 57 80 / 10 0 0 0
Newton 57 75 56 78 / 0 0 0 0
ElDorado 57 74 55 78 / 0 0 0 0
Winfield-KWLD 59 76 57 79 / 10 0 0 0
Russell 58 76 58 81 / 10 0 0 0
Great Bend 58 76 57 81 / 10 0 0 0
Salina 57 76 56 80 / 10 0 0 0
McPherson 56 76 56 79 / 10 0 0 0
Coffeyville 61 75 58 79 / 0 0 0 0
Chanute 59 74 57 78 / 0 0 0 0
Iola 58 74 56 77 / 0 0 0 0
Parsons-KPPF 60 75 58 78 / 0 0 0 0
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Ketcham
LONG TERM...Ketcham
AVIATION...RM
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1110 PM EDT Sat Sep 8 2018
.UPDATE...
Issued at 1110 PM EDT SAT SEP 8 2018
Updated the forecast package for latest trends in PoPs and temps.
Surface warm front will begin to edge northward between now and
dawn. PoPs south of this feature were lowered for the remainder
of the night as most of activity through the evening has been
along and north of the front. HRRR has had a good handle on
things thus far and suggest this trend will be the case through
the remainder of the night. However, cold front to west is making
a move eastward as well. Thus PoPs will be gradually rising from
the west through early morning Sunday. Finally, band of very heavy
rainfall (nearly a half inch fell in 5 minutes at Frankfort
mesonet) accompanied by gusty winds of 30 to 40 mph continues to
march eastward at a somewhat slower pace than one might expect. It
has been showing signs of weakening over the past hour. If this
line holds together it should reach our Bluegrass counties by
around midnight. Will be watching this feature closely as it
pushes into our area for possible hydro issues and/or special
statements.
UPDATE Issued at 841 PM EDT SAT SEP 8 2018
Moisture continues to stream into the area. A surface warm
frontal boundary is draped across eastern Kentucky, roughly
stretching from Whitesburg to Mount Vernon. The warm front is
expected to gradually lift northward Sunday morning. Until then
this feature will continue to be a focus for isolated to
scattered shower and thunderstorm activity through the overnight.
WPC has placed portions of Fleming and Bath counties in a moderate
risk for flash flooding over the next 3-6 hours due to a couple
of training bands of heavy precipitation upstream. Will be
watching these carefully as they approach and possibly pass
through our Bluegrass counties. Mason County mesonet has already
pick up nearly three inches, half of that total through mid-day
and the other half through the evening. Seeing estimates of
similar totals for a few locations up in that area. Updated grids
for latest observations and will freshen up the zone package.
Otherwise forecast is on track.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 352 PM EDT SAT SEP 8 2018
Current conditions across the area feature a warm front set up
across the area as strong convection has developed along and north
of it this afternoon. Due to heavy rainfall this morning north of
I-64 and the expected convection this evening, some FFG is a bit
lower in the north. Given model soundings in the short term with
PWATs in the 2 inch range and skinny CAPE profiles, have decided
to issue the Flash Flood Watch starting this afternoon and
continuing into Sunday evening.
Expect precip in the north to weaken and and become more
stratiform with a steady rainfall into the night but still putting
down some decent amounts. Later tonight, the front will begin to
push east into central Kentucky. This will bring a bit more
forcing into the the area and thus a bit more efficiency in the
precip amounts and with a saturated air mass in place across the
area, flash flooding will certainly be possible.
The continued heavy rainfall chances will continue into Sunday as
the front pushes east. While the NAM seems to be over doing QPF
amounts, models do suggest a slower passage of the front as it
crosses eastern Kentucky. This will make for moderate to heavy
rainfall amounts over a prolonged period of time. The front
finally pushes into eastern Kentucky by 00z. Thus will keep the
watch out through 00Z Monday. In fact, with the front still
hanging out across central portions of eastern Kentucky, another
day of strong storms is possible. Some areas in the south will see
some breaks allowing some instability to build south of the warm
front and even as the cold front pushes east across the area.
By Sunday night, as the front pushes into far eastern Kentucky,
much of the heavier precip will come to an end. Thus will insert
lower chance pops behind the front as much of the precip winds
down. Some fog may be possible behind the front for Monday
morning. Overall, a wet short term, period of the forecast is
likely with flash flooding possible.
.LONG TERM...(Monday through Saturday)
Issued at 326 PM EDT SAT SEP 8 2018
At the start of the period an upper level low pressure system will
be over northern MI with surface low pressure in southeast MI. A
cold front trailing from the surface low will be in the far
southeast part of the forecast area. The front will slowly push
southeast of the forecast area on Monday, before stalling in the
Appalachians.
There is good model agreement that upper level high pressure over
the western Atlantic will build west through the middle to latter
part of the week. This will result in rising heights back into our
area. The front that will have pushed southeast of KY on Monday will
likely meander back to the northwest by midweek. By late in the week
the front will still be in the area but will become increasingly
diffuse.
All eyes will be on the Atlantic during the coming week as Hurricane
Florence makes its way west under the large mid/upper level high
pressure system sprawled from the western Atlantic into the eastern
U.S. There is still considerable uncertainty with the path of the
hurricane and what if any impact it will have on our weather by next
weekend.
The threat of showers and thunderstorms will remain in the forecast
through the week as the already noted front moves through the area,
stalls, and then likely returns by mid week. However, any showers
and storms will mainly be diurnally driven and should only be
isolated to scattered in nature. Temperatures will be a little
cooler to start the week with the front having passed to our
southeast, but temperatures will climb to well above normal readings
again by the middle and latter part of the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 841 PM EDT SAT SEP 8 2018
Moisture continues to stream into the area. A surface warm
frontal boundary is draped across eastern Kentucky, roughly
stretching from Whitesburg to Mount Vernon. This feature
continues to be a focus for shower and thunderstorm activity this
evening. CIGS are considerably lower along and north of this
boundary. And of course VSBYS lower as showers and thunderstorms
pass any given location. In general a bad night to be out flying
in this area. Stayed close to guidance for terminal forecasts.
That being said looking for showers on and off through the
overnight. Can not rule out some rumbles of thunder here and
there. Do expect a relative lull in showers late tonight into the
pre-dawn time frame. But shower and thunderstorm activity picks
back up through the day tomorrow ahead of a cold front as it bears
down on our area from the west late in the day. Light east-
southeast winds will become more southerly with time as the
surface warm front gradually lifts northward through the early
morning Sunday, generally after sunrise for our eastern and
northern most sites, just a few hours before sunrise for our
southern most terminals.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Sunday evening for KYZ044-050>052-
058>060-104-106>112-119-120.
&&
$$
UPDATE...RAY
SHORT TERM...SHALLENBERGER
LONG TERM...SBH
AVIATION...RAY
Area Forecast Discussion
National Weather Service North Platte NE
710 PM CDT Sat Sep 8 2018
.SHORT TERM...(This evening through Sunday)
Issued at 207 PM CDT Sat Sep 8 2018
A northern stream trough will keep low level moisture and stratus
over the forecast area tonight. In addition, there will be a
slight chance for showers and a few thunderstorms. The 12z GFS
look to high on QPFs, and favored the drier NAM, and latest HRRR
and RAP runs. Chances look to remain mainly north of I80, and west
of Burwell, Stuart and Naper. Low fairly mild in the upper 50s.
On Sunday, lingering showers possible until 10 am cdt, from North
Platte northeast through Ainsworth and Bassett. Otherwise,
widespread stratus will erode from west to east. South winds will
increase to 10 to 20 mph, as the surface pressure gradient
tightens up. Highs to reach around 85 northwest sandhills to
around 75 far southeast zones, which remains near the previous
forecast.
.LONG TERM...(Sunday night through Saturday)
Issued at 207 PM CDT Sat Sep 8 2018
Another northern stream disturbance Sunday night will bring a
slight chance for showers or a few thunderstorms to mainly Keya
Paha and Boyd counties.
Beginning Monday, zonal flow aloft will become increasingly
southwesterly as the week progresses, along with a warmup to above
normal highs. Highs Monday in the low to mid 80, will range in the
mid to upper 80s Tuesday through Friday, then back in the low to
mid 80s Saturday. Dry in the extended, except for a slight chance
for thunderstorms Tuesday evening in north central Nebraska.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 710 PM CDT Sat Sep 8 2018
Low cloudiness will push into western and north central Nebraska
overnight with IFR ceilings developing at the KLBF terminal after
05z Sunday. MVFR ceilings will set in across northern Nebraska
overnight. Skies will gradually clear Sunday afternoon at both
terminals.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Roberg
LONG TERM...Roberg
AVIATION...Buttler
Area Forecast Discussion
National Weather Service Medford OR
857 PM PDT Sat Sep 8 2018
.SHORT TERM...A low pressure system is located well to the
northwest off the British Columbia coast with zonal flow aloft over
the area tonight into Sunday. As the low moves into the British
Columbia coast, a cold front will push into the Pacific Northwest
coast Sunday evening and night. Models continue to show that this
front will bring light showers to the southern Oregon coast and
inland over Coos and portions of Douglas County Sunday night and
Monday morning. Also expect this system to bring a cooling trend
on Monday. High temperatures are expected in the 70s to around 80
for inland areas on Monday. Additionally some east side valleys
may see lows in the mid to lower 30s Monday morning. With the
front, also expect breezy northwest winds across many inland
areas, including from the Cascades east and into the Shasta and
Rogue valleys, late Monday afternoon and Monday evening.
Areas of smoke are expected tonight and Sunday downwind of
wildfires. This will bring smoke impacts into Joesphine, Jackson
and Siskiyou counties with lesser impacts into Klamath, Lake and
Modoc counties. Areas of smoke are likely to continue into Monday
as well. However, some improvement is expected late Monday as the
front moves into the area, bringing cooler temperatures and
increased winds aloft to transport smoke out of the area.
Tuesday into Wednesday, models show and upper trough settling over
the area with an upper low moving down the Pacific Northwest. This
pattern is expected to bring additional cooling to the area and
more fall-like temperatures. Light showers are also possible over
area west of the Cascades, with best chances along the coast from
Cape Blanco northward and across Douglas county. Models continue
to show variability on how much shower activity will progress
inland south of the Umpqua Divide and east of the Cascades. So
confidence in any showers for these areas remains low.
&&
.AVIATION...For the 09/00Z TAFs...Stratus and fog with IFR to LIFR
ceiling and visibility will be common along the coastal strip
through the night, especially north of Cape Blanco. Stratus will
also gradually build into the western Umpqua Basin and may make it
right up to KRBG by morning. Elsewhere, conditions will be VFR with
the exception of those areas affected by smoke. Current high
resolution smoke models show this to continue be from Grants Pass to
KMFR and to a lesser degree KLMT. Visibility restrictions due to
smoke in these areas will vary greatly through the night, but
conditions are generally expected to remain MVFR or better. MVFR
and local IFR visibilities are also expected tonight and Sunday in
Siskiyou county, including at KSIY and KMHS. Periods of MVFR
visibilities may also occur east of the Cascades in Klamath
County. -CC/Wright
&&
.MARINE...Updated 800 PM PDT Saturday, 8 September 2018...
Relatively weak winds and low seas will persist into Sunday morning.
Northwest swell will increase Sunday into Monday night, but will not
become steep. A series of weak fronts will move across the waters
next week with seas slowly trending slightly lower Tuesday into
Friday. -DW/Wright
&&
.PREV DISCUSSION... /Issued 239 PM PDT Sat Sep 8 2018/
DISCUSSION...High pressure has built into the region behind a
departing cold front, but an upper level low has taken up
residence off the coast of the Queen Charlotte Islands of British
Columbia. This will keep cool onshore flow over our forecast area
for the next few days. It also means a few impulses will pass over
the area as they orbit the low, and these will provide reinforcing
shots of cool air, and at least a couple of chances for rain for
portions of the area.
For smoke, this pattern will mean relief for most areas, both by
blowing away the accumulated smoke and by toning down activity on
many of the local wildfires. However, west winds do mean that
areas in the vicinity and to the east of the fires will still
remain under the plumes, and therefore will not fully clear. HRRR
smoke models continue to push smoke from the Klondike and Natchez
fires into the Illinois, Applegate, and Rogue Valleys, while smoke
from the Delta fire streams into the area around Mount Shasta
City and southeastern Siskiyou County. With the next front`s
arrival late Sunday and into Monday, it is possible much of the
smoke production and fire activity will have died down enough to
more significantly clear the air.
This front appears a bit more robust than the last when it comes
to moisture, and we have increased the chances of light rain
along the coast and into the Umpqua Basin Sunday night and Monday
morning. Those south of the Umpqua Divide and east of the
Cascades will not be so lucky, as the weak front will wash out as
it crosses onshore, and the bulk of moisture and lift will stay
well to the north. The same can be said of the next, very similar
front due into the area Tuesday into Wednesday.
While moisture will be limited and most areas should remain dry,
the effects of the fronts will be felt by all when it comes to
temperatures, as highs on Monday through Wednesday are expected
to be 5 to 10 degrees below normal for this time of year. In fact,
it is possible that very few places in the forecast area will
reach 80 for a high Tuesday, and nighttime lows in our usual cool
spots may make a good run for the freezing mark. As a result,
some locations, such as Tulelake, may need to be on the lookout
for frost/freeze conditions beginning Monday morning.
The low itself finally drops south into the region Wednesday into
Thursday, before opening up and sliding inland late in the week.
This will keep a chance of showers in the area Wednesday night
into Thursday. With the trough passing overhead, it is even
possible that an isolated thunderstorm could develop along and
east of the Cascades in the afternoons, but chances are the area
will only see light showers, as once again moisture inflow and
overall instability are limited.
Heading into the weekend, models are coming into much better
agreement than we have seen over the past several days. Both the
GFS and ECMWF solutions show a ridge building into the area from
the south Friday into the weekend, with a thermal trough
redeveloping along the coast. This pattern would produce dry east
winds and a return to near or slightly warmer than normal highs
for Friday and Saturday, so the forecast has been changed to
trend towards this idea. -BPN
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.
CA...None.
Pacific Coastal Waters...None.
$$
CC
Area Forecast Discussion
National Weather Service New York NY
1046 PM EDT Sat Sep 8 2018
.SYNOPSIS...
The area will remain under the influence of high pressure to the
north and a stationary front to the south through Sunday. The front
then begins to move northward as a warm front Sunday night,
lifting north of the area Monday night. An approaching cold
front will then stall or dissipate across the area Tuesday into
Wednesday. High pressure builds to the north of the area for the
end of the week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Just a few minor adjustments to account for the bulk of the
light rain moving off to the east. Therefore conditions will
dry out from NW to SE the next couple of hours. Additionally,
slight adjustments were made over the next 6 hours with respect
to wind. HRRR and GLAMP blend was used here as this guidance
was lining up better with current conditions.
With the stationary front remaining south of the area and an upper
trough slowly approaching from the west, an overrunning pattern
remains over the area with occasional light showers expected through
the night, particularly across coastal areas. Precipitation chances
may briefly decrease across the Lower Hudson Valley and Connecticut
this evening as high pressure builds to the north, advecting drier
air southward. However, confidence is low in this scenario, as
precipitation has continued to redevelop through much of the day.
Otherwise, temperatures will remain below climatological normals
through the night, despite overcast skies, as cooler Canadian air is
advected into the area and onshore flow persists.
The high risk of rip currents on the ocean beaches continues into
tonight, with waves and swell increasing well ahead of tropical
cyclone Florence.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Winds strengthen through the day on Sunday as the stationary front
to the south begins to slowly move northward, strengthening the
pressure gradient between the high pressure to the north. Cloudy
conditions are expected to persist, especially with opaque cirrus
ahead of the remnants of tropical cyclone Gordon to the west.
Similar to Saturday, an overrunning pattern will lead to the chance
for off and on showers through the day, gradually increasing into
the night.
Have delayed the onset of likely precipitation, as more recent
deterministic and high resolution models suggest an initial struggle
to saturate drier low levels, with the Canadian high pressure
remaining to the north. As the upper trough nears and attendant
front moves closer to the area, chances of showers will increase
overnight and towards day break, with moderate to heavy rainfall
possible at times, particularly to the north and west of the city.
The high risk of rip currents on ocean beaches continues into Sunday
and Sunday night. A high surf advisory is now in effect for
Sunday and Monday.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
A confluent flow between the southern and northern branches of
the polar jet will retreat to the northeast along with strong
surface high pressure over the Canadian Maritimes. The cool, dry
air over New England and a southern branch low over the Great
Lakes will result in deep-layered warm advection across the region
Monday with a moderate rainfall event. This will be more of a
stratiform rain, but weak elevated instability may allow for an
isolated afternoon/evening thunderstorm.
A warm front works north of the area Monday night with the return
of a warm, muggy airmass as winds become southerly. Precipitation
will become more scattered and convective in nature Monday
night through Wednesday. A weakening cold front will then move
into the area Tuesday afternoon. There is some uncertainty as to
whether or not the boundary passes just east of the area, or
dissipates across the region through midweek. The associated
southern branch shortwave trough dampens as it lifts northeast of
the region and the western Atlantic ridge expands westward into
the Ohio Valley. This in turn will likely suppress convection for
the second half of the week with high pressure building to the
north of the region. Easterly flow will likely develop and bridge
across whatever is left of the front.
The aforementioned upper level ridge will also become a big
player in the future track of Tropical Cyclone Florence. Global
models do differ in the magnitude of the western Atlantic ridge
with a potential weakness developing late next week near the
eastern seaboard. The latest official forecast from the National
Hurricane Center takes the system westward toward the southeast
and Mid Atlantic coasts toward the second half of next week.
Outside of a prolonged period of swells, resulting in rough surf,
dangerous rips currents, and beach erosion, it is still too early
to determine if the region will experience additional impacts. To
maintain good situational awareness, please refer to the latest
official forecast from the National Hurricane Center
(www.nhc.noaa.gov).
Temperatures moderate through the period with highs in the 70s
Monday, to the lower and middles 80s for the rest of the week.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Canadian high pressure builds to the north through Sunday
morning as a frontal boundary remains across the mid Atlantic
region. The high retreats to the northeast Sunday afternoon as
the frontal boundary begins to move north as a warm front.
VFR through the forecast period. Light rain has pushed south of
all terminals. Conditions should remain mainly dry through at
least 06Z, however, rain showers will slowly move back
overnight, so added VCSH after 06Z for metro terminals, with
later times for all other terminals. Better chances for rain
after 20Z Sunday for the metro terminals.
N to NE winds 10-15KT shift to the NE to E overnight with
occasional gusts as high as 20KT through this evening. Winds
increase to around 15 to 20KT on Sunday afternoon with up to
25KT by after 20Z.
.OUTLOOK FOR 00Z SUNDAY THROUGH THURSDAY...
.Sunday night-Monday...MVFR, with IFR possible. Rain, locally heavy
at times possible. E-SE winds 15-20KT, G20-30KT.
.Monday night-Tuesday...MVFR possible and a chance of showers/tstms.
SW winds G15-20KT possible.
.Tuesday night-Thursday...MVFR possible in a chance of showers/tstms.
&&
.MARINE...
Conditions will steadily deteriorate through the weekend,
particularly on the ocean, as swell builds and northeasterly to
easterly winds increase. The strongest winds are expected Sunday
night into Monday, and a gale watch is now in effect for the ocean
waters. SCA-level winds are expected elsewhere beginning Sunday
night. Winds will diminish late Monday, however seas will
remain well above SCA levels on the ocean due to long period
swells being generated by Tropical Cyclone Florence. To maintain
good situational awareness, please refer to the latest official
forecast from the National Hurricane Center (www.nhc.noaa.gov).
&&
.HYDROLOGY...
Around one to two inches of rain with locally higher amounts is fcst
Sun thru Mon ngt, with the greatest amounts expected across
northeastern NJ into the Lower Hudson Valley. Although the main
threat right now is for minor urban and poor drainage flooding, a
more significant flood risk will be possible if the axis of hvy rain
ends up further e than expected attm. Any tstms Tue-Fri will be
capable of producing locally hvy rain.
&&
.TIDES/COASTAL FLOODING...
Minor coastal flooding is possible with this evening and again
during the morning high tide cycles across portions of the
south shore back bays of Kings, Queens and Nassau counties.
The combination of increasing astronomical tides from a new moon
occurring Sunday, an increasing easterly flow and building SE swells
will bring the potential for more widespread minor to locally
moderate coastal flooding beginning late Sunday and persisting into
early next week.
Tidal departures of 1 to 1 1/2 ft are all that is needed at most
locations for minor coastal flooding benchmarks to be met, however
some of locations on the south shore of Long Island and western LI
Sound only need between 1/4 and 3/4 ft.
&&
.EQUIPMENT...
NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off
the air for an extended period of time.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Rip Current Risk through Sunday evening for NYZ075-080-
081-178-179.
High Surf Advisory from 11 AM Sunday to 6 PM EDT Monday for
NYZ075-080-081-178-179.
NJ...None.
MARINE...Small Craft Advisory from 6 PM Sunday to 6 PM EDT Monday for
ANZ330-335-338-340-345.
Gale Watch from Sunday evening through Monday afternoon for
ANZ350-353-355.
Small Craft Advisory until 6 PM EDT Sunday for ANZ350-353-355.
&&
$$
SYNOPSIS...MD/DW
NEAR TERM...JE/DW
SHORT TERM...MD
LONG TERM...DW
AVIATION...JP
MARINE...MD/DW
HYDROLOGY...MD/DW
TIDES/COASTAL FLOODING...
EQUIPMENT...
Area Forecast Discussion
National Weather Service Pueblo CO
608 PM MDT Sat Sep 8 2018
.UPDATE...
Issued at 600 PM MDT Sat Sep 8 2018
Updated to adjust sky cover and fog potential across the Plains
for tonight into Sunday morning. Most models are in agreement that
low stratus and area of fog are expected to develop, especially
given the low level flow and similar conditions to last night. No
other changes at this time. Mozley
&&
.SHORT TERM...(This evening through Sunday)
Issued at 301 PM MDT Sat Sep 8 2018
Relatively tranquil and mild conditions currently gracing southern
Colorado with recent GOES imagery indicating developing cumulus
fields over many western mountain locations. Latest data indicate
that next upper disturbance moving into northwestern Colorado with
recent lightning strikes noted over far northeastern Utah.
Incoming HRRR computer simulation indicates that isolated primarily
higher terrain showers and thunderstorms will be possible over
southern Colorado from this afternoon into this evening, while
recent NamNest solution is slightly more aggressive with
precipitation over higher terrain locations generally along and west
of the Interstate 25 corridor into this evening.
So for sensible weather, will depict isolated primarily higher
terrain thunderstorms into this evening. In addition, conditions
again favorable for areas of low clouds/fog over eastern sections
from later this evening into Sunday morning. For now, will trend
with low cloud development over far eastern locations before
midnight, with west-ward push into/near portions of the Interstate
25 corridor a few hours after midnight. Then, low cloud conditions
expected to improve as the morning progresses Sunday morning with
far eastern sections the latest to experience improvement.
For Sunday, next upper disturbance is expected to rotate across the
forecast district and will be capable of producing next round of
isolated to scattered primarily afternoon into evening showers and
thunderstorms. In addition, gradient winds are expected to remain
light during the next 24 hours, while maximum temperatures on
Saturday are projected to run near to a few degrees warmer than
values noted Saturday.
.LONG TERM...(Sunday night through Saturday)
Issued at 301 PM MDT Sat Sep 8 2018
...Some Lingering Moisture Monday then Mainly Hot and Dry...
Models still have a little bit of lingering moisture over the
forecast area Monday as a very weak upper level disturbance moves
across. However, the airmass will be drying out in the lower levels
with dewpoints generally in the 30s or less from the I-25 corridor
westward. Dewpoints will be higher east of the corridor but the
airmass will be too stable for storms. So, there will be some
isolated afternoon and evening storms along and west of the I-25
corridor Monday but little activity east of the corridor. The
primary storm threats will be lightning and gusty winds.
On Tuesday, forecast models have dry southwest flow spreading into
Colorado, boosting temperatures and decreasing storm chances. The
chance for storms will be just about zero on Tuesday. An isolated
storm may find a way to fire along or near the Kansas border during
the afternoon but confidence is pretty low. Temperatures Tuesday
afternoon will climb back to midsummer levels.
Wednesday through Saturday will be hot and dry with temperatures
holding at midsummer levels through the period. The heat won`t be
quite as bad as midsummer, though, as the nights will be a little
longer and cooler than midsummer.
With hot and dry weather in the forecast, now is a good time to
think about how fire danger levels might change in the weeks ahead.
This is the time of year when daily afternoon showers decrease and
periods of dry weather increase. As a result, it`s also the time of
year when grasses begin to dry out. If we fail to see some decent
amounts of wetting precipitation from time-to-time, we`ll see
fire danger levels escalate once again. Guess it`s time to hope
for the best but prepare for the worst. Any fire mitigation that
could be done where you live?
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 301 PM MDT Sat Sep 8 2018
Overall, VFR conditions are anticipated over the TAF sites into this
evening, with recent HIRES model solutions continuing to indicate
that isolated showers and thunderstorms will be possible near but
not directly impacting the TAF sites into this evening.
In addition, recent HIRES models indicating that stratus is expected
redevelop over the far southeast Colorado Plains later this evening
and push west towards the I-25 corridor after 09Z tonight with KPUB
having the highest potential to notice some low cigs/etc. with this
development.
Computer simulations then project that VFR conditions
will return to far eastern locations of southeastern Colorado by
later Sunday morning with next round of isolated to scattered
showers and thunderstorms then impacting southern Colorado from
Sunday afternoon into Sunday evening as next shortwave impacts the
area.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...MOZLEY
SHORT TERM...77
LONG TERM...LW
AVIATION...77
Area Forecast Discussion
National Weather Service Blacksburg VA
841 PM EDT Sat Sep 8 2018
.SYNOPSIS...
A wedge of cool air will surge south through the region tonight
resulting in lingering showers as well as patchy drizzle into
the early morning hours of Sunday. The wedge will remain in
place through Sunday with a continued chance for showers through
the latter portion of the weekend. Low pressure crossing from
the Ohio Valley through New England will erode the wedge on
Monday then stall a weak front over the Mid Atlantic Tuesday and
Wednesday, before Florence begins to impact parts of the East
Coast late in the week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 830 PM EDT Saturday...
Cold front near the Blue Ridge should continue to surge
southwest through the region overnight reaching southern sections
by morning. This will result in a quick 10-15 degree drop in
temperatures along with a round of gusty northeast winds.
Convergence zone just ahead of the boundary continues to help
fire heavy rain producing convection per lingering decent
instability across southern and southwest sections. Latest HRRR
continues to develop showers/storms along the front over
the far southern sections with some of this becoming elevated
upon crossing into the cooler air to the north. Expect once the
shallow cool pool undercuts the rest of the convection will
gradually see a transition from showers to more stratiform
nature light rain/drizzle after midnight. Thus adjusted pops to
account for more coverage east and less west where the earlier
band continues to stay just off to the west. Also slowed down
the switch from convective mode over the south/west a few hours
but maintained overall high chance to likely pops through early
Sunday. Kept low temps close to previous with only a small bump
up in lows across the south at this point.
Previous discussion as of 230 PM EDT Saturday...
Showers and thunderstorms have developed ahead of a developing
wedge pushing down from the south. Precipitable water values
remain elevated so the threat of excessive rainfall and
localized flooding remains. Additionally, even though the
dynamic environment is weak there will be a good amount of low
level shear in the vicinity of the wedge front so expect some
degree of organization to convection later this afternoon. As
the wedge pushes down in earnest this evening this will enhance
convergence and isentropic lift and continue with a good chance
of showers overnight.
The wedge remains in place through Sunday with weaker isentropic
lift continuing showers and some drizzle through the day. There
will be some destabilization on the western/southern edge of the
wedge tomorrow but the better chances for thunder will be just
outside of our region.
Temperatures tonight will range from the mid/upper 50s from the
Alleghany Highlands to the low/mid 60s elsewhere. Highs Sunday
will be in the low to mid 60s in the heart of the wedge, rising
to the mid 70/upper 70s west of the Blue Ridge and from
Southside to the NC foothills.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 1151 AM EDT Saturday...
The weather will remain unsettled Sunday evening into Sunday night.
Southwest flow at 500 mb continues and upper diffluence increases
over the Mid-Atlantic region along with lift under the left entrance
region of an upper jet streak. A warm front will lift north across
the region. The low level southwest flow will erode wedge late
Sunday night into Monday morning. Low temperatures Sunday night will
range from the upper 50s in the mountains to around 70 degrees in
the piedmont.
The warm front continues to lift north on Monday as a cold front
approaches from the west. The warm, humid, summerlike air mass
returns to our area with high temperatures Monday from near 70
degrees to the mid 80s in the piedmont. Scattered showers and
thunderstorms mainly afternoon and evening are expected. With the
loss of solar heating, most of the convection will diminish Monday
night. Areas of low clouds and fog will develop Monday night into
Tuesday morning. Low temperatures Monday night will feature readings
from around 60 degrees in the northwest mountains to the lower 70s
in the piedmont. Frontal boundary will stall across the region
Tuesday into Tuesday night with showers and thunderstorms likely.
The backing of the low-level flow Tuesday into Wednesday could
permit some heavy showers to form in upslope areas on the east side
of the mountains as moisture deepens in the profiles and
precipitable water values. High temperatures will moderate into the
lower 70s in the west to the mid 80s in the east. Low temperatures
Tuesday night will generally be in the lower 60s to the lower 70s.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 1151 AM EDT Saturday...
All eyes on the Atlantic as Florence, likely a strong hurricane
after intensification on Sunday, appears to be posing an increasing
threat to the southeastern US coast, but there is still lots of time
for that to change. Please refer to the latest NHC advisory on
Florence for details on strength, movement and track.
Strong upper ridge dominates just off the mid-Atlantic coast with
associated surface high pressure over the East Coast, which may make
it hard for the storm to turn north for awhile. The strength and
shape of the blocking upper high will dictate where Florence will
track.
In any case, warmer conditions each day under the ridge and enough
moisture to result in diurnal and mainly mountain afternoon and
evening convection. Low level boundaries and moisture convergence
will create scattered showers and thunderstorms.
If Florence does indeed head in the direction of the Carolina coast
and even inland into Virginia, that would result in maybe a day of
sinking motion and lack of precipitation perhaps around Wednesday or
Thursday. The range of possibilities of actual track still extends
from Florida northward to at least the Mid-Atlantic which includes a
chance of it recurving just offshore. If Florence ends up
heading in our direction we could experience impacts as early as
Thursday, but more likely Friday, from increasing north to
northeast winds and then eventually heavy rain.
The major point to make at this time regarding Florence is that
while it is way too soon to have much confidence in whether or not
it will impact the RNK county warning area, everyone needs to keep a
close eye on forecasts of Florence from the National Hurricane
Center and the NWS office like ours over the weekend.
By Monday of next week we should have a much better handle on the
track of Florence and who will/will not be impacted by this major
hurricane. A track through South Carolina into western North
Carolina and then into southwest Virginia would be the worst case
scenario for us, while a further eastward track along the coast
would have considerably less impact on our region, perhaps no more
than just gusty north winds. Now is the time to begin considering
what preparations need to be made should Florence directly impact
our area.
For the medium range forecast, the consensus guidance which is
consistent with an extrapolation of the official NHC forecast
suggests the storm would move into eastern VA by late Thursday into
Friday, so the wind and PoP forecast grids reflect that idea for
now, but with wind speeds toned down considerably from what they
would be should Florence actually take a further westward track.
There still is a great deal of uncertainty in extended forecast.
Stay tuned throughout the days ahead as the forecast is likely to
change several times in the next few days.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 650 PM EDT Saturday...
Scattered showers thunderstorms will continue to affect TAF
sites into late this evening, espcly along the corridor from
KLWB to KLYH and KDAN where coverage looks to be the most
widespread. Will include a prevailing group for shra/tsra
pending locations of showers in regards to the terminals at
release. Otherwise continuing with a VCTS/VCSH mention and
including a TEMPO group as well where sub-VFR looks to be rather
brief. A wedge of cool air will push south behind a passing cold
front overnight with this boundary reaching the Blue Ridge
locations by midnight and much of the rest of the region in the
early morning hours of Sunday. This will bring more widespread
IFR/LIFR conditions behind the front with winds becoming
east/northeast and a bit gusty mainly east of the Blue Ridge.
Isentropic lift over the wedge will keep some showers around
before gradually tapering to drizzle and fog. There may be some
improvement in conditions late in the period but with a solid
wedge in place will opt to stay with mainly IFR/LIFR conditions
through much of Sunday as well.
High confidence in precipitation and developing IFR/LIFR
conditions.
Extended Discussion...
A wedge will remain in the area into Sunday night, so Sunday
night will likely again have widespread IFR/LIFR conditions.
The wedge erodes Monday with scattered MVFR showers and
thunderstorms. MVFR and IFR thunderstorms are likely on Tuesday
and Wednesday. May see overall VFR return Thursday pending the
timing of Florence with much of the region still west of this
system until late week.
Confidence average for all elements through Tuesday. Below
average confidence Wednesday into Thursday.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...JH/MBS
NEAR TERM...JH/MBS
SHORT TERM...KK
LONG TERM...KK
AVIATION...AMS/JH/MBS