Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/21/19
Area Forecast Discussion
National Weather Service Bismarck ND
1020 PM CDT Thu Jun 20 2019
.UPDATE...
Issued at 1018 PM CDT Thu Jun 20 2019
Storms had trouble keeping going over eastern Montana due to lack
of instability, so have cancelled the severe thunderstorm watch.
Still may be some storms later tonight, but expect these to remain
on the weaker side.
UPDATE Issued at 642 PM CDT Thu Jun 20 2019
Concern at this time focuses primarily over far southwest North
Dakota where models continue to show impressive shear, though the
fly in the ointment continues to be marginal instability. With
that said, the potential for a storm quickly increasing in
strength will be possible later this evening over far southwest
North Dakota as the storms move in from Montana. Therefore, a
severe thunderstorm watch has been issued for the aforementioned
area.
&&
.SHORT TERM...(This evening through Friday)
Issued at 335 PM CDT Thu Jun 20 2019
Skies will continue to clear across much of western and central
North Dakota this afternoon as showers and a few embedded
thunderstorms slowly move off into eastern North Dakota. The mean
long wave trough located over the western CONUS will amplify as
an embedded shortwave rotates around the base and ejects across
eastern Montana and eventually into western North Dakota. Showers
and thunderstorms will develop over eastern Montana in an
environment characterized by strong deep layer shear ranging from
50 to 70 knots, strong forcing, and MUCAPE ranging from 200 to
1000 J/kg. Further east, the gradient of MUCAPE drops sharply over
southwestern North Dakota, but the latest RAP forecast soundings
suggest 100 to 300 J/kg of MUCAPE will be possible over the far
southwest. Simulated reflectivity from HRRR iterations has been
consistent since early this morning that one or two strong to
severe storms will nudge into our southwest near the ND/SD border
before weakening in the 00z to 03z Friday time frame which seems
reasonable. This solution is reflected in the Storm Prediction
Center day 1 outlook.
Overnight, a 500 mb low will close off as the upper trough flicks
into western North Dakota. This mid-level cold core low will
bring the potential for a few strong to severe storms across the
northwest and potions of the the central. At the surface a
relatively strong low will deepen as the system starts to become
stacked. Widespread cloud cover and ongoing shower/thunderstorm
activity may begin to break up south of a northward advancing warm
front as steep mid-level lapse rates and a dry slot settles into
the west. The steep lapse rates will promote a narrow axis of
strong MLCAPE in the lowest 3 km along and south of the advancing
warm front and east of an eastward advancing cold front.
Afternoon thunderstorms will redevelop along this triple point and
the strong low level CAPE will be co-located with 0-1 km bulk
shear ranging from 15 to 25 knots. This synoptic pattern suggests
a potential threat for some low-topped supercells along the arcing
warm front extending east and southeast from the surface low. If
low topped supercells do develop and if they can remain discrete,
a cold core tornado threat could present itself along with the
threat of large hail given the cold temperatures aloft. However,
plenty of uncertainty remains regarding cloud cover and
destabilization which is a usual caveat for these setups and why
the threat is conditional. Another potential fly in the ointment
continues to be a northward trend of the system, which may push
the main threat into the southern Canadian Prairies of
Saskatchewan.
Finally, the Storm Prediction Center has placed much of the
northwest and central part of the state in a Marginal Risk of
severe weather for Friday, which seems reasonable given the
uncertainty that remains regarding the more fine scale details and
surface low track.
.LONG TERM...(Friday night through Thursday)
Issued at 335 PM CDT Thu Jun 20 2019
Saturday looks to be breezy south of the upper level low across
southern Canada. Diurnally driven rain showers and thunderstorms
are possible given the cool temperatures aloft. However, the
impact of the dry slot favors the best chances for precipitation across
the northwest and north central in the wrap around moisture.
Thereafter, the 12z GEFS 850mb temperature plumes clearly paint
the picture of a slow warm up, eventually pushing high
temperatures back into the 80s by late in the week. 00z Thursday
NAEFS percentiles suggest an anomalous meridional wind component
across North Dakota as well as anomalous ridging towards the end
of the period. Additionally, these percentiles suggest anomalous
moisture and moisture depth for this time of year. These factors
continue to illustrate a potential transition to southwest flow
aloft late next week, which may also increase the risk for severe
thunderstorms. Finally, this potential is also signaled by the
CIPS analogs for severe reports, and the GEFS CAPE plumes.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 642 PM CDT Thu Jun 20 2019
Showers with scattered thunderstorms will move west to east into
the area tonight and remain through much of Friday. This will
bring many areas of MVFR ceiling and visibility, with localized
IFR conditions.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...JJS
SHORT TERM...ZH
LONG TERM...ZH
AVIATION...JJS
Area Forecast Discussion
National Weather Service State College PA
1047 PM EDT Thu Jun 20 2019
.SYNOPSIS...
A slow moving storm system will push across the state overnight
Friday will be cooler and drier, and the pleasant conditions
will continue through the weekend.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Meso anal shows a nearly stationary East-West front over my
northern counties. Convection is increasing over western Pa in
response to the approaching North-South cold front which is
just nearing the PA/OH border.
The HRRR shows the showers and storms becoming widespread as
they move east and into the CWA over the next several hours.
Latest RAP shows a bubble of PWATS exceeding 1.5" pooling right
along the front. With dewpoints in the mid to upper 60s the
airmass is primed to take advantage of the modest instability
supporting localized torrential downpours with rates of 1-2
inches per hour.
The flash flood watch remains in effect through 05Z Friday.
The front is slated to move very slowly with the upper trough
supporting additional showers well into the overnight and even
into early Friday morning.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/...
Breezy and drier/less humid conditions will arrive Friday as
showers retreat in the wake of the departing system. Some patchy
fog in the valleys is possible during the predawn and early
morning Saturday-Sunday. Expect a welcomed break from the rain
for 2-3 days with pleasant conditions through the weekend.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
A more summerlike pattern arrives for Monday and lasts through
next week. A warm front pushing through early Monday will bring
clouds and showers, lingering into the afternoon in the north.
Humidity will rise again with dewpoints increasing to the mid
60s for much of the week. The GFS model is suggesting modest
instability each afternoon next week, with afternoon
thunderstorms possible. Whether or not there will be organized
convection will depend on if any disturbances in the mid or
upper atmosphere align with the peak of the diurnal instability.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Adjusted the TAFS some just after 1030 PM.
Looks like a circulation point is northeast of State College,
so showers and isolated storms with heavy rain to the northeast
of the office may slow some, but overall no big changes to
earlier fcst.
Earlier discussion below.
00Z TAFS sent.
Still 2 bands of showers and isolated thunderstorms to the west.
Thus expect some more poor weather conditions this evening.
Main issue later once cold front moves across the area, lower
CIGS will prevail to just after sunrise on Friday, as a low
pressure system moves across the area, and much cooler air
works in.
The main issue for Friday will be gusty winds, as the strong
June sun works on the cooler air aloft, on the first day of
summer.
Nice weekend in store for the area with VFR conditions.
.Outlook...
Sat-Sun...No sig wx expected.
Mon...Ceiling restrictions poss in rain showers.
Tue...Still a chance of showers.
&&
.CLIMATE...
Astronomical summer (solstice) begins Friday, June 21st at
1154AM EDT (1554 UTC).
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 1 AM EDT Friday for PAZ004>006-010>012-
017>019-024>028-033>037-041-042-045-046-049>053-056>059-
063>066.
&&
$$
SYNOPSIS...Dangelo/La Corte
NEAR TERM...La Corte/Ceru
SHORT TERM...Steinbugl
LONG TERM...Steinbugl/Colbert
AVIATION...Martin
CLIMATE...Steinbugl
Area Forecast Discussion
National Weather Service Des Moines IA
634 PM CDT Thu Jun 20 2019
...Updated for Discussion on Convective Trends and 00z Aviation
Discussion...
.UPDATE...
Issued at 632 PM CDT Thu Jun 20 2019
Isolated showers and thunderstorms have been developing over
northwest Iowa since around 5pm. The storm northeast/east-
northeast of Sioux City has showed several instances of increases
in lightning over the last hour and a half, but has overall
struggled to further mature in an environment of 2000 J/kg of
MLCAPE and effective shear around 55 knots. Another storm to the
south of Sioux City has also struggled to have much for
intensification. Both of these storms have had cirrus overspread
them with recent satellite trends showing weakening bursts of new
cloud growth. Current expectation is that these will continue to
diminish as the sun sets. The strongest storm that may impact our
area is the supercell over south central Minnesota, which has been
following the Bunkers Right Moving vector. This may clip our far
northeast forecast area around 2z/9pm, though high resolution
models such as the HRRR show this dissipating as the sunset. Will
continue to monitor trends. No significant update to the forecast
at this time, but will be evaluating models for updates to PoPs
and timing for expected thunderstorms after midnight tonight.
&&
.SHORT TERM.../Tonight through Friday night/
Issued at 343 PM CDT Thu Jun 20 2019
Three time frames for potential convection were the focus this
period. Leaned toward a blend of the HRRR/NAM/HREF tonight into
Friday morning and then a blend of the NAm/GFS/ECMWF Friday night.
The first round is this afternoon into the early evening over the
southwest sections of the forecast area. The 20.18z HRRR suggests an
isolated storm to develop over west-central Iowa and track southeast
through the southwest corner of the CWA. The 20.12z HREF updraft
helicity maxes out between 22z to 03z in the same location as the
HRRR suggests. Via the latest SPC mesoanalysis, MUCAPE has grown to
over 2000 J/kg, effective shear tops out around 65 knots in the far
southwest with the gradient extending from around Crawford down to
Decatur Counties. Weak low level shear and effective helicity,
although there is decent 0-3km helicity in the far southwest, so the
tornado threat is not completely zero. More concerned about the
elevated hail threat with LCLs around 750-1000m and then also the
damaging wind threat as DCAPE ranges from 500-900 J/kg. The 18z OAX
sounding has a bit higher DCAPE and lower LCLs but looks to be a
weak cap in place around 850mb. More likely to see something
elevated with the ML CAPE near 1000 J/kg and decent shear present
within the ML.
Late tonight but more likely early Friday morning looks to be the
second round of convection as a decent shortwave in conjunction with
the LLJ develops. The timing of the convection moving across the
CWA is still questionable, but storms are more than likely to move
into the west/southwest past 09z Friday and track east throughout
the rest of the morning hours tomorrow. Not terribly concerned with
severe storms with the lack of significant instability and deep
layer shear present, but more concerned that this will be a primer
for flooding Friday night into Saturday. Warm layer cloud depths
range from 3500-4000m and PWATs are in the 1.5 to 2.0 inch range
Friday morning. However, moisture transport isn`t great into the
state as it gets cutoff from convection across the Ozarks. There is
the potential for some moderate to heavy rain Friday morning, but
the rain rates and progressive nature of the storms should limit the
flash flood threat.
Lastly is potential for widespread convection Friday night into
Saturday morning. The Friday morning convection should keep the
atmosphere stable through much of the day with cloud debris and rain
cooled air across the CWA. Thus, higher confidence in timing of
storms to redevelop past 03z Saturday and persist well into the
morning Saturday as the LLJ strengthens. The 20.18z HRRR suggests
storms to get going by around 02z Saturday voes the south and spread
northeast. Severe threat will be determined how much the atmosphere
rebounds from the convection Friday morning. The NAM and GFS has
the southern portion of the forecast area to see CAPE build to 1500-
3500 J/kg by 03z Saturday with good deep layer shear to provide
updraft sustainability. Thus if a cold pool develops, the threat for
damaging winds increases late tomorrow night. Still, heavy rain is
likely the primary concern with warm layer cloud depths as high as
13kft and PWATs near 2.0 inches which is close to the climatological
daily max. Plus, Corfidi vectors are in-line with the storm motion,
so the potential for training storms exists and efficient rain
producers. A Flash Flood Watch for tomorrow night into Saturday
morning is likely going to be needed as we get closer to the that
time frame.
.LONG TERM.../Saturday through Thursday/
Issued at 343 PM CDT Thu Jun 20 2019
Complex pattern will continue to impact central Iowa through the
weekend. Deep west coast trough will continue to push across the
Rockies and into the western Plains ejecting shortwaves across the
state through the weekend. The trough axis finally clears Iowa
early Tuesday morning. This will be followed by an upper level
ridge that will clear things out through midweek. At the surface a
low will exist over Kansas with a frontal boundary extending from
the low into Iowa. The main instability through Saturday early
afternoon will exist mainly south of the state but by late Saturday
instability will surge into southern/eastern Iowa as the low lifts
from Kansas into western Iowa. Shear isn`t particularly impressive
but there are pockets of 40+kts at times so a few severe storms will
be possible especially near the boundary. Late Sunday/Sunday night
when the upper trough finally pushes through, we will likely be
dealing with more widespread heavy rainfall across the southeast
third or so of the state in addition to the threat for hail/wind
primarily.
On Monday, most of the lingering precip will occur across the north
and east as the trough and surface low lift out of the area. After
Monday we will be dry with seasonal temps until Thursday when the
ridge flattens some with the passage of a shortwave. Models differ
on timing and strength of the shortwave and as such, confidence is
low that far out on precip location and timing. NBM keeps small
PoPs in Tue through Thu but with a large ridge over us really don`t
see much potential for precip.
&&
.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 632 PM CDT Thu Jun 20 2019
Isolated showers or thunderstorms have developed over northern
Iowa with another isolated storm over southern Minnesota. Primary
concern is storm over southern Minnesota that is diving
southeastward and could impact MCW toward 3z, though high
resolution models show this dissipating. At this time, do not have
any mention of these showers/storms in the official TAFs. Next
concern is line of showers and storms that are expected to arrive
several hours after midnight. Have confined VCTS to a short window
where confidence is highest in rain/thunder with VCSH before
and/or after as needed. Refinement of timing and inclusion of some
impacts will be included in the 6z issuance. Additional showers
and storms are possible later Friday, but low confidence to
include anything at this time with MVFR to perhaps IFR ceilings
expected.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Ansorge
SHORT TERM...Podrazik
LONG TERM...FAB
AVIATION...Ansorge
Area Forecast Discussion
National Weather Service Grand Forks ND
851 PM CDT Thu Jun 20 2019
.UPDATE...
Issued at 851 PM CDT Thu Jun 20 2019
The coverage of the showers continues to shrink, with most of the
activity now east of Detroit Lakes across west central Minnesota.
Quite a bit of cloud cover still lingers over the area, especially
along and east the Red River Valley. Made some more adjustments to
continue to decrease the coverage area of showers through the rest
of the evening.
&&
.SHORT TERM...(This evening through Friday)
Issued at 334 PM CDT Thu Jun 20 2019
A 500 mb short wave trough extending from the main 500 mb low over
the northern Rockies causing the band of rain over eastern ND.
This area is moving more north but only slowly as moisture feed is
more from the southeast to northwest and the precipitation band is
oriented in that direction. The short wave trough will weaken
tonight and the band of light rain will diminish this evening. But
pockets of light rain may remain into the night, esp over WC MN
and into parts of the mid RRV. There is a sfc low in far NE SD
moving into far SE ND this evening and will be the focus for a bit
heavier rainfall this evening.
Low level moisture increases overnight into Friday morning with
925 mb flow increasing form the south-southeast. Dew points likely
to climb into the lower to mid 60s over parts of SE ND Friday.
With the low level moisture transport overnight there is likely to
be lower level cloud developing and spreading north.
Friday itself likely to be rather cloudy so surface heating ahead
of the next stronger short wave trough/sfc trough will be
affected. The short wave trough/sfc trough will be near a Devils
Lake to Aberdeen area by 00z Friday. The focus for storms will be
near this boundary. High shear but low cape environment in place
for these storms...but enough cape, esp in SE ND, to likely
generate scattered severe storms. SPC HREF Updraft helicity
forecast tracks not too impressive however from the 12z HREF. So
not a given severe weather will occur...but given strength of
0-6 km shear and 0-1 km SRH a few severe storms seem more likely
than not over esp SE ND. Severe threat will move into the RRV and
then diminish late evening over NW MN. Right now being
conservative with dew points indicate 62-63 in far SE ND but if
get higher and any sun breaks in the clouds ahead of the trough
instability values of 2500-3000 j/kg may occur as highlighted by
HRRR in a few areas in our southern fcst area. But otherwise
looking at general 1000-1500 j/kg in SE ND.
.LONG TERM...(Friday night through Thursday)
Issued at 334 PM CDT Thu Jun 20 2019
Following the surface low moving east, expect to see precipitation
chances decrease throughout the day on Saturday from west to east.
As upper level flow becomes southwesterly, see the rain chances
remain scattered throughout the weekend. Temperatures are expected
to be seasonable with the warmest temps being in the Red River
Valley, where some areas could reach into the upper 70`s. Expect the
pattern to continue into Monday with precipitation chances remaining
scattered due to the presence of the longwave trough.
Tuesday through Thursday...
The trough will continue to progress further east, followed by an
upper level ridging pattern over the northern Plains with some small
embedded shortwaves in the upper levels. The large-scale ridging
pattern will allow for a steady warm-up with nearly all areas
reaching well into the 80`s by the middle of the week. Scattered
showers and thunderstorms are also possible with guidance suggesting
northern areas near the Canadian border being favored for Tuesday
before chances spread over the eastern ND/northwest MN later in the
week. Uncertainty still exists for this time frame, but a summer-
like pattern is indicated at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 651 PM CDT Thu Jun 20 2019
Other than a few light showers early this evening, most of the
rest of the evening should be fairly quiet. Model guidance
continues to show a MVFR cloud deck developing over the FA later
tonight and holding into Friday morning. If that happens, the
Friday afternoon and evening predicted storms may fire over
central ND and move east into eastern ND during the late afternoon
and evening. Therefore, only mentioned thunder for now at KDVL.
Winds look to become pretty gusty by late Friday morning into the
afternoon, especially in the Red River Valley.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Godon
SHORT TERM...Riddle
LONG TERM...AM/BSW
AVIATION...Godon
Area Forecast Discussion
National Weather Service Hastings NE
848 PM CDT Thu Jun 20 2019
...Short Term Update...
.UPDATE...
Issued at 847 PM CDT Thu Jun 20 2019
Some commentary about the next 12-24 hours:
1) Overnight severe storm potential still on track:
Per the latest Mesoscale Discussion from SPC, we are still very
much anticipating at least one or more clusters/rounds of strong-
to-severe storms overnight (mainly after 11 PM), and a Severe
Thunderstorm Watch for most/all of the CWA is anticipated to be
issued sometime in the next few hours. From our local perspective,
things are still very much on track from the main afternoon
discussion below. We have apparently "dodged" the slim possibility
of any early-evening storm development in our southern zones
(although a severe storm did develop slightly east of our CWA in
northeast KS a few hours ago). Thus, nearly our full attention is
focused westward, where isolated severe convection is well-
underway in the NE/KS/CO border region. With time, this convection
will roll east into our CWA, and likely grow upscale into one or
more lines/clusters, with more isolated activity probably
developing behind these larger-scale complexes in response to lift
along the residual elevated cold pool/along axis of southerly low
level jet evident at 850 millibars. Even late in the night,
elevated instability/CAPE in the 850-700 millibar layer is progged
to remain quite stout (2000-4000 J/kg) per the latest RAP13, so
it`s a semi-volatile environment around here (at least by late-
night standards). Did tweak our Hazardous Weather Outlook (HWOGID)
to increase severe wind potential to 70 MPH, especially if storms
form into bowing segments. Hail up to around golf ball size
remains on track, but this will probably be the larger exception.
Not expecting widespread flooding issues, but some areas could
pick up a quick 1-2" of rain, with localized/short-term flooding
certainly a possibility.
IN SUMMARY: Several strong to severe storms are likely overnight,
starting around roughly 11 PM in our far west and spreading
eastward overnight. At least an isolated severe storm threat could
even last past sunrise (perhaps to around 7 AM).
2) Friday trending somewhat cloudier/cooler:
Not as pressing as number 1 above, but latest model data has been
trending cloudier and thus at least slightly cooler for Friday. In
an earlier update, increased sky cover and lowered high temps
generally 2-3 degrees from initial afternoon forecast package, and
could easily see our overnight forecast shaving a few more degrees
off. If these cloudier trends do in fact verify, it may be tough
for much of the northwest 2/3 of our CWA to exceed 80 degrees, and
with low 90s less likely over our far south in KS.
&&
.SHORT TERM...(This evening through Friday)
Issued at 226 PM CDT Thu Jun 20 2019
This main focus for this forecast is multiple rounds of
potentially severe thunderstorms.
Currently, a surface cold front is dropping south across the
area, shifting winds from the south to the northwest and north.
This feature is forecast to stall out across the area this
evening. A few CAMs still show isolated storms near the late this
afternoon and evening, but these chances remain low.
The stronger signal in the near-term models has been for one or
more clusters of thunderstorms to develop over western Nebraska
and Kansas and track through the local area late tonight. Activity
will likely then persist into Friday morning as we will be on the
nose of a 30-35kt low-level jet. These storms should be elevated
in nature so I believe the main threat will be large hail. RAP
soundings show 2500-3000J of elevated CAPE above 850mb along with
ample shear, therefore the strongest storms could easily have hail
to the size of golf balls...or larger. The strongest organized
cold pools may allow for isolated severe wind gusts as well. The
HRRR shows the initial line of storms to be pretty progressive,
but shows additional scattered showers and storms developing
behind it. As a result some isolated locations could also pick up
some heavy rainfall totals as well.
Storms may linger into Friday morning, but we should mostly dry
conditions return by mid to morning into the early afternoon.
Areas near and south of the the surface boundary will have plenty
of instability to work with as temperatures surge into the 80s and
low 90s. Convective development remain somewhat uncertain,
though. For the most part, models show our area remaining free of
surface-based convection during the afternoon and evening with
developing southeast of the local area. Then additional convection
may move in from the west again overnight.
.LONG TERM...(Friday night through Thursday)
Issued at 226 PM CDT Thu Jun 20 2019
Convective details continue to get more uncertain into Saturday.
That being said, it appears that at least southeastern portions of
the area still have a shot to see severe storms with the front
stalled nearby and the upper trough over the Rockies slowly
pushing eastward.
On Sunday, the upper trough finally pushes through the area. This
will bring us another day with shower and storm chances. The area
should then finally see a couple dry days Monday and Tuesday as
the system departs and we see rising heights aloft. As we return
to westerly flow aloft and southwesterly flow at the surface,
temperatures should be able to return to the upper 80s and 90s.
A few subtle disturbances move through the area Tuesday night
through Thursday bringing low-end chances for rain. Better chances
will likely hold off until the next trough moves over the Rockies
the following weekend.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 719 PM CDT Thu Jun 20 2019
General overview:
There are clearly two main issues during the period: 1) A good
chance of thunderstorms (potentially severe) overnight, especially
during the 05-10Z time frame...2) What appears to be increasing
chances for sub-VFR ceiling through much of the latter half of the
period (Friday daytime). Otherwise, OUTSIDE of thunderstorm
outflow/influences, surface winds should not be a big issue, with
speeds generally at-or-below 10KT and direction generally some
variation of easterly through much of the period, but more
northerly by late Friday afternoon. Read on for more details
regarding thunderstorm/ceiling issues...
Thunderstorms:
Confidence is high in storm-free conditions through at least these
first 4-5 hours, but after that expect a somewhat "bumpy ride"
overnight, as there is a decent chance that one or more
clusters/lines of storms will pass through. Decided to introduce
TEMPO groups covering the 05-10Z period to highlight the overall
best window of opportunity for convection, with a "vicinity"
(VCTS) mention covering hours slightly before and after. Severe
storms are possible with damaging winds/hail, and for now have
gone with a basic "VRB30KT" wind mention during the TEMPO
timeframe, along with an MVFR visibility mention (although it
could certainly be well-below this for brief times). Although the
chance of at least isolated showers could linger past sunrise, the
majority of the latter 12 hours should be dry, and have refrained
from introducing any additional thunderstorm mention into Friday
afternoon for now.
Ceiling trends/uncertainty:
High confidence in VFR through at least the first 4-6 hours, and
moderately-high confidence in predominantly VFR through the first
12 hours. However, there are increasing signals that much of the
latter half of the period (Friday daytime) will feature MVFR
ceiling, with even some potential for periodic IFR. For now, have
not bought fully into the most pessimistic solutions, but have
introduced MVFR to most of Friday daytime.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
UPDATE...Pfannkuch
SHORT TERM...Mangels
LONG TERM...Mangels
AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Louisville KY
1000 PM EDT Thu Jun 20 2019
.Forecast Update...
Issued at 958 PM EDT Thu Jun 20 2019
Added some small measurable pops across the Bluegrass region where
some light returns are persisting. These will just be light showers,
if at all. Otherwise, the forecast is on track tonight.
Did want to make note of the 21/00z HRRR which does develop a wind
producing complex to our NW tomorrow, rounds the base of the ridge,
and then dives SE along the instability gradient into our CWA Friday
evening. If data continues to support this scenario, we will have to
ramp up the damaging wind threat for later Friday. Stay tuned.
&&
.Short Term...(This evening through Friday)
Issued at 255 PM EDT Thu Jun 20 2019
Cold front continues to push through the region this afternoon.
We`ve seen a scattered line of convection develop along the cold
front over the past hour or two, and these storms should gradually
move eastward along the front. By early evening, expect most of the
precipitation to be east of the I-75 corridor.
Skies should gradually clear from west to east overnight, and the
gusty winds we had during the afternoon should taper down. High
pressure will nudge in from the west after midnight, and we could
see a period of light to calm winds with clear skies during the
early morning hours. Given the wet ground conditions from recent
rains, patchy fog looks like a good bet for most of southern Indiana
and central Kentucky in the vicinity of the high, some of which may
be dense.
Any fog that develops should gradually burn off by sunrise Friday
morning. Much uncertainty remains in the forecast going beyond the
morning hours, as models take an MCS that develops over the Plains
and swing it somewhere between eastern MO and eastern KY during the
afternoon and evening hours. Have included chance PoPs in the
forecast for the afternoon hours for all but the eastern 1/3 of the
CWA where the best model precipitation consensus is. Should our
region be in the path of this MCS, strong to severe storms would be
possible.
.Long Term...(Friday night through Thursday)
Issued at 325 PM EDT Thu Jun 20 2019
Friday Night - Sunday Night...
An upper ridge axis will extend from the Gulf of Mexico up through
the mid Mississippi River Valley, with NW flow aloft over our
region. Models continue to indicate that an MCS will be ongoing
either upstream of our CWA or already impacting our CWA during this
time, however each one differs on timing/placement. Given a
moderate/strong NW/SE instability gradient, and 25-35 knot 0-6 km
deep layer shear oriented in the same manner there will be potential
for organized wind producing storms. Will have to keep it general
until models come into better agreement, and will also have to note
the inversion evident on soundings that could limit convective
potential. Nevertheless, any organized cold pool upstream would
likely at least somewhat survive into our area and could produce
some impacts.
The upper ridge axis will slowly slide east over our area through
the weekend, but will be characterized as a "dirty" ridge as chances
for showers and storms will continue under a strongly unstable
airmass. SREF probs have very high probabilities of at least 3000
J/KG of CAPE all through the weekend, with likely amounts over 4000
J/KG at times. May have to deal with some capping at times given the
upper ridge, so triggering and weaker deep layer shear will be
limiting factors. Nevertheless, and storm that does develop will
likely carry a hail and isolated wind threat, in addition to heavy
rainfall and plenty of CG lightning.
Expect a muggy stretch with lows in the low to mid 70s and highs in
the mid to upper 80s.
Monday - Monday Night...
The upper ridge axis will shift to the east by the start of the new
work week, however a strong shortwave will quickly approach. Given
better forcing and deeper moisture return in the SW flow ahead of
the shortwave, expect better coverage of showers and storms, along
with some stronger wind shear. A few organized storms may be
possible later Monday into Monday evening.
Tuesday - Thursday...
Chances for a drier stretch of weather may arrive by mid to late
week as upper ridging over the southern CONUS strengthens and seems
to push the stronger westerlies up over the NE CONUS. As a result,
of the upper ridging and overall drier forecast look for highs to
creep up toward the upper 80s by the end of the week. Will still keep
some small chances for a shower or storm in the forecast, but
overall this should be a drier stretch.
&&
.Aviation...(00Z TAF Issuance)
Updated at 750 PM EDT Thu Jun 20 2019
Gusty WNW winds should slacken off in the next hour or so behind the
cold front that passed through earlier today. Will start the TAFs
out with no gusts before winds go light and variable toward
midnight. Visible satellite imagery shows coverage of the cu field
diminishing over our region and upstream, so will continue to
message a clearing trend overnight, in addition to winds becoming
light and variable. This will create a good radiational cooling
setup to the point where some fog may be a concern. Crossover T
analysis reveals that HNB/LEX will have the best potential for fog,
with lesser fog potential at SDF/BWG. Will mention MVFR vis
restrictions at HNB with a tempo for IFR. At LEX, confidence is low
whether or not we`ll see fog or stratus so have mentioned a mixture
of both since low level winds will be a bit stronger over there.
Otherwise, fog clears around and shortly after sunrise with VFR
prevailing and a light SE wind developing. There is some potential
for afternoon/evening storm development but confidence is too low to
include mention at SDF for now.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...BJS
Short Term...DM
Long Term...BJS
Aviation...BJS/CJP
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
Issued by National Weather Service Duluth MN
657 PM CDT Thu Jun 20 2019
.SHORT TERM...(This evening through Friday night)
Issued at 231 PM CDT Thu Jun 20 2019
The 850 mb theta-e ridge will continue to work into the area this
evening, helping to drive and area of showers with embedded
thunderstorms eastward across the area. However, there should be a
diminishing trend as the activity gets into the eastern portion of
the area tonight and the forcing weakens. We`ll have a second
surge of moisture and better instability work into the area Friday
afternoon and Friday night, bringing a better chance for SHRA/TSRA
to the entire area, although the best instability and shear look
to be across the western forecast area late Friday afternoon into
Friday evening.
.LONG TERM...(Saturday through Thursday)
Issued at 231 PM CDT Thu Jun 20 2019
The southwest to northeast oriented baroclinic zone still looks
to stall out Saturday into Monday with several surface waves
moving along it and bringing windows of enhanced precipitation
changes to the area. Tried to get some of that timing into things
rather than blanket the entire time frame with chance PoPs.
However, the guidance (understandably) agrees much less on the
details as we move through the weekend given small differences in
convective development that compound over time. Stuck very close
to the consensus NBM guidance from Saturday night through the
balance of the forecast. We should finally see a break in the more
widespread precipitation by Tuesday, although there will be some
additional chances through the remainder of the week as ridging
becomes established over the central part of the country and we
get into a pattern more favorable for MCS development. It`s way
too early to say whether we`ll be in the path for repeated MCS
passages, but given the forecast position of the upper jet and
best areas of anticyclonic 250 mb flow, it certainly will be
something to keep an eye on for the middle to end of the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 647 PM CDT Thu Jun 20 2019
Showers will generally be on the decrease overnight; however, a
line of showers in south central MN is slowly pushing eastwards
and is increasing in intensity and is not captured very well by
any of the high resolution models. The HRRR is trying to capture
the feature, and dissipates it by 02Z, but this model has a
tendency to play catch up to these types of features. Mainly VFR
conditions prevail, dipping into MVFR or even IFR given the recent
shower activity for AXN & RWF overnight.
KMSP...VFR for most of the TAF period. Showers west of the
terminal are increasing in intensity and may cross the terminal
between 01 and 03Z. Winds will generally be east and increase in
intensity Friday afternoon.
KMSP...
/OUTLOOK FOR KMSP/
SAT...VFR/MVFR WITH PM SHRA/-TSRA POSSIBLE. WINDS E/SE AT
5-10KTS.
SUN...VFR/MVFR WITH -TSRA POSSIBLE. WINDS VRB AT BELOW 5KTS.
MON...VFR/MVFR WITH CHC -TSRA POSSIBLE. WINDS W AT 5-10KTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...
LONG TERM...
AVIATION...JW
Area Forecast Discussion
National Weather Service Norman OK
714 PM CDT Thu Jun 20 2019
...Update...
&&
.DISCUSSION...
There have been several attempts at deep moist convection along the
dryline in the eastern Texas Panhandle. These have mostly
concentrated near an inflection at the mouth of Palo Duro Canyon
where parcel residence time may be locally higher than further north
or south. As CI occurs and cells move east, they diminish quickly
given relatively substantial MLCIN of around 100 J per RAP
soundings. This process should decrease as diurnal heating lessons
later this evening. Without any noteworthy large scale ascent or
other lifting process, the chance of measurable precipitation into
western Oklahoma seems nil.
Latest mesonet observations show several sites with a heat index
still at or above 105 degrees, mainly across southern Oklahoma and
into north Texas. The Heat Advisory continues until 9pm.
The forecast is in good shape and other than very minor
adjustments, no changes planned through the night. Enjoy the near
80 degree dew points.
BRB
&&
.PREV DISCUSSION... /issued 640 PM CDT Thu Jun 20 2019/
DISCUSSION...
00Z TAFs.
AVIATION...
VFR conditions will prevail. An isolated thunderstorm is not
completely out of the question as there is at least some
convection developing in the Texas panhandle, although the chances
are pretty low of affecting the TAF sites. Also added some low-
level wind shear as south-southwest winds is expected to increase
to 45-50 knots above the surface overnight.
PREV DISCUSSION... /issued 357 PM CDT Thu Jun 20 2019/
DISCUSSION...
.Severe Weather/Heavy Rainfall Returns This Weekend...
Welcome to summer (technically a day early)! Summer weather has
arrived across Oklahoma and western north Texas today. Oklahoma
City has officially reached at least 90 F for the first time this
year. Temperatures in the 90s F combined with very high dewpoints
(~75-78 F) has resulted in heat index values >105 F for many
locations.
There is a low chance that thunderstorm(s) may affect western
Oklahoma this afternoon; however, the probability is low with a
cap/convective inhibition in place. Trends will have to monitored
this evening because if any storms can become sustained,
significant hail will be possible.
Another hot and humid day is expected tomorrow with temperatures
in the 90s F and dew points in the 70s F. As a dryline mixes into
western Oklahoma/western north Texas, temperatures may warm into
the 100s F across the west. A Heat Advisory may be needed for
parts of the area tomorrow. Isolated thunderstorms may develop
across southwest Oklahoma/western north Texas as well.
For Saturday, a lead shortwave trough is expected to approach
from the west. Severe thunderstorms are expected to develop across
the panhandles/western Oklahoma along a dryline Saturday
afternoon. Extreme instability (>4500 J/kg) and moderate effective
bulk shear (~30 knots) would be favorable for supercells with the
potential for significant (2") to giant (4") hailstones along
with damaging wind gusts. Low-level/0-1 km shear at ~20 knots will
result in an attendant tornado risk as well.
These thunderstorms are expected to consolidate and grow upscale
into an MCS that would move through at least the northern half to
two-thirds of Oklahoma Saturday evening into the overnight hours.
The potential for giant hail should decrease with the loss
supercellular structures/mesocyclones; however, there will be a
continued threat for damaging wind gusts (perhaps widespread) and
large hail. A moderate low-level jet (40-50 knots) will increase
the low-level shear for embedded circulations/a QLCS tornado
threat with the MCS. Heavy rainfall/flooding will also be hazard.
By Sunday, the primary trough is forecast to eject into the
Plains. Additional thunderstorms are expected to develop Sunday
afternoon, especially near any remnant boundary. There is some
uncertainty where convective initiation may occur, but it may be
somewhere near the I-44 corridor. Severe weather will be likely
with any thunderstorms once again with extreme instability and
moderate effective bulk shear.
Beyond Monday, mid-level heights are forecast to rise as a ridge
develops across the southwest U.S; however, there will be at least
a low chance for showers/storms as the Southern Plains will be on
the eastern periphery of the ridge.
Mahale
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 75 93 74 89 / 0 0 10 20
Hobart OK 74 99 74 93 / 0 10 20 30
Wichita Falls TX 77 97 76 93 / 0 20 20 20
Gage OK 69 101 71 92 / 0 0 10 40
Ponca City OK 76 94 75 91 / 0 0 10 20
Durant OK 76 92 76 89 / 0 0 10 20
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Heat Advisory until 9 PM CDT this evening for OKZ023>032-038>048-
050>052.
TX...Heat Advisory until 9 PM CDT this evening for TXZ086-089-090.
&&
$$
12/26
Area Forecast Discussion
National Weather Service Paducah KY
651 PM CDT Thu Jun 20 2019
.SHORT TERM...(Tonight through Saturday night)
Issued at 305 PM CDT Thu Jun 20 2019
After a brief lull in precip chances most of tonight, the chances
will ramp back up on Friday as a short wave trof tops the rather
flat H50 ridge and heads southeast toward the region. However,
there remains quite a bit of uncertainty concerning both the
timing and the placement of the convective complex that is likely
to get going overnight nw of the region. The 12Z HRRR was a bit of
an outlier from the other HREF CAMS, holding of the complex until
afternoon/evening and tracking it farther to the east of the MS
River. Most of the other CAMS bring the the thunderstorm complex
in farther west along/west of the MS river during the morning
hours. Either way, it is looking as tough we will be dealing with
a fairly healthy system crossing a good portion of the region
sometime during the day.
Looking at the severe aspect of the storms, models do forecast
favorable veering winds with height and a decent amount of bulk
shear to support organized convection. The amount of instability
may be a bit more unclear, given the uncertainty regarding timing.
of course, it seems the earlier the convection comes in, the less
time we will have to destabilize, and visa versa. There is concern
enough though that SPC Day 2 has outlooked the entire forecast
area in a slight risk for the period.
Confidence is increasing that we will see another round of strong
thunderstorms develop Friday night into early Saturday along a
nearly stationary surface boundary that should be draped from nw
to se across srn IL into western KY. Another short wave is
expected to round the top of the H50 ridge and interact with the
boundary overnight Friday. It is looking as though the highest
chances for thunderstorms will be along and east of the sfc
boundary. With PWATS in the 1.75 to 1.90" range, expect any storms
to contain torrential downpours also. Depending on antecedent
soil conditions from Friday`s activity, a flash flood watch may
need to be considered in later forecast packages. Farther to the
west, along and west of the MS River, conditions are likely to
remain too capped for storm development Friday night/Saturday time
frame. Current thinking is that the sfc front will lift back to
the northeast during the day Saturday. Hopefully, the highest
shower/thunderstorm chances will lift northeast with it by
Saturday night.
It will also be uncomfortably humid Friday and Saturday, with sfc
dew points running in the mid 70s. Depending of the amount of
sunshine we can manage each day, some locations could be dealing
with their first 100 degree heat indices of the season. The
highest chance to see this lies along and west of the MS River
Saturday, in the more capped region southwest of the frontal
boundary.
.LONG TERM...(Sunday through Thursday)
Issued at 305 PM CDT Thu Jun 20 2019
The models are in slightly better agreement with the synoptic scale
features this weekend. They differ in their solutions as we head
through next week. However they both agree with the most rainfall
Sunday night into Monday.
The models agree that the upper level ridging over the area will
shifting to the east. This will be in response to a sharpening upper
level trough moving into the plains. The main difference is that
ECMWF has closed low which is likely the reason for its slower
progress while the GFS is open and a bit faster. The Canadian is a
little closer to the ECMWF solution. They all do agree the low
closes off and lifts into the great lakes region Monday. The trough
however remains over the area providing additional chances for rain.
They start to decrease chances as we head through the mid week time
frame. To add to rain chances we will have a warm front lift through
Saturday placing us in the warm sector. The trailing cold front
approaches the area but appear to make it through or even into the
area. This will push dew points into the 70+ range providing
abundant moisture for anything that does fire up. We also have
PWAT`s around 1.5 inches...so heavy rain at least with the stronger
storms. The CAPE`s will be 2k or more with LI`s greater than
negative 5. So thunder will be included at the very least. May have
to keep a slight chance in through the middle of the week for
collaboration. Temperatures should be slightly above normal for the
extended.
&&
.AVIATION...
Issued at 650 PM CDT Thu Jun 20 2019
Challenging 00z Friday WFO PAH TAF issuance. The primary concern
will be in the 15z Friday through 00z Saturday time frame.
Prior to 15z Friday, all WFO PAH TAF sites should see diurnal
cumulus thin out prior to 02z, with VFR cloud bases and
visibilities the rule during this period.
After 15z Friday, the concern comes with the evolution of a
mesoscale convective system moving from northern Missouri and
Iowa and expanding south and east into the WFO PAH forecast area.
The 00z Friday TAF issuance utilized wind, visibility, and cloud
heights primarily from a short range consensus model blend,
adjusted somewhat with the 13km RAP guidance.
The timing of convective activity (showers and thunderstorms)
through each of the WFO PAH TAF sites is the most problematic.
Given the uncertainty in timing, utilized a mention of vicinity
thunderstorms (VCTS) to reflect those time periods where the
probability is increased into the chance category. For KCGI, KMVN
and KPAH, this will start in the 15z-18z, with 18z through 00z
time frame for KEVV and KOWB.
Based on the latest available high resolution model guidance as of
5 pm CDT Thursday, the timing of the thunderstorms from west to
east into the WFO PAH forecast area is modeled closer to the RAP,
HRRR, NAM-WRF (ARW version), and HREF Convection Allowing Model
(CAM) guidance. This keeps most of the activity west of the KEVV
and KOWB sites through at least 1630z Friday. The 4km NAMnest
Ensemble guidance is the only numerical model that brings a thin
line of showers/thunderstorms west of KEVV around 15z Friday. The
NAM-WRF NMM/ARW versions are the most pessimistic with ceilings
and visibilities between 18z and 21z Friday at KEVV and KOWB, and
15z-18z for KCGI, KMVN, and KPAH.
The evolution of the thunderstorms and potential for issues into
the next 24 hour forecast period (06z Friday issuance) will be the
eventual location of the frontal boundary sprawled southwest of
KCGI and KPAH by 12z Friday, moving northeast of KEVV and KOWB by
12z Saturday.
Bottom line...temporary reductions of ceiling and visibility into
MVFR, and possibly IFR category, will likely increase at
KCGI/KPAH/KMVN between 15z-18z, and KEVV and KOWB after 18z
Friday.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
SHORT TERM...GM
LONG TERM...KH
AVIATION...Smith
Area Forecast Discussion
National Weather Service Pueblo CO
327 PM MDT Thu Jun 20 2019
.SHORT TERM...(This evening through Friday)
Issued at 327 PM MDT Thu Jun 20 2019
West to southwest flow aloft combined with a weak embedded
disturbance has kicked off some high based showers and thunderstorms
across the mountains and along a surface boundary/trof axis across
Las Animas and Pueblo counties. East of the surface trof axis...dew
points have been hanging in the upper 40s/lower 50s while west of
the lee trof surface dew points have fallen off into the 30s. As
thunderstorms move eastward this afternoon and evening, they will
encounter increasing moisture and instability. Although the main
threat will be gusty erratic winds up to around 60 mph in localized
areas...some hail up to 1 inch in diameter will be possible where
higher dew point air remains in place. Greatest hail risk will be
across Kiowa county and points northward through early evening, and
HRRR has been fairly persistent with the stronger convection in that
area through the evening. All activity will decrease or push
eastward by late evening.
Southwest flow aloft increases overnight tonight into Friday as the
northern U.S. Rockies upper low translates eastward and more energy
drops down its western periphery into the northern Great Basin on
Friday. A cold front will make a push into southeast CO late tonight
into early tomorrow morning before lifting back northward during the
afternoon. This will set the stage for the potential for severe
thunderstorms along the Palmer divide and possibly Crowley and Kiowa
counties during the afternoon and evening along/north of the front.
It will all depend on where the front stalls and some lower res
models are keeping majority of the activity just north of the area.
Could see some hail to around quarter size or larger and wind gusts
around 60 mph with the stronger storms to the north of the front. -KT
.LONG TERM...(Friday night through Thursday)
Issued at 327 PM MDT Thu Jun 20 2019
...Unsettled and Unseasonably Cool This Weekend...
Friday night-Sunday...Latest models are in better agreement with the
unseasonably strong upper trough digging into the Great Basin Friday
night, which then slowly lifts out across the Rockies Saturday night
and early Sunday before moving out across the High Plains late
Sunday afternoon and evening. Increasing moisture and lift ahead of
this system will keep isolated to scattered showers and storms
across the higher terrain, especially along and west of the ContDvd
Friday night, with the potential for showers and storms along and
behind a frontal boundary moving across the southeast Plains Friday
evening. Latest thinking is the best potential for stronger storms
will along and north of the Palmer Dvd on Friday, though if this
boundary is further south earlier in the day, there would be the
potential for stronger storms across all of the southeast Plains
late Friday afternoon and evening. At any rate, the front looks to
push south and west across the Plains Friday night, with stratus
developing and filling in behind the front into early Saturday
morning. With moist upslope flow expected behind the system on
Saturday, there is the potential for a post frontal severe storm
setup across the Plains, with strong shear and associated lift ahead
of the unseasonably strong upper trough. SPC Day 3 Outlook has much
of the Plains in a marginal risk, with the cavet there is enough
destabilization to tap the rich low level moisture in place. At this
time, most model solutions indicate it will be too cool and stable
with stratus in place across the Plains through the early afternoon.
Again will need to watch how this unfolds. At any rate, should see
scattered to numerous showers and storms spreading across the higher
terrain through the afternoon, with showers and a few storms
spreading across the I-25 Corridor through the far southeast Plains
Saturday night, the system lifts out across the area. Latest
guidance suggest snow levels falling to around 9,500 feet through
early Sunday morning, supporting some accumulating snow generally
across the higher peaks. There remain some differences on timing of
the ejecting trough, though most solutions keep the best chances of
showers on Sunday to over and near the higher terrain. With the
unseasonably cool system, overnight lows look to be in the the 30s
and 40s across the area Saturday night and Sunday night, with highs
in the 60s and 70s across the Plains and mainly 40s and 50s across
the higher terrain through the weekend.
Monday-Thursday...A warmer and drier pattern remains in the offing
as a large ridge of high pressure is forecast to build into the
Rockies through the beginning of the week and become entrenched
across the area by the middle and end of next week. This will bring
steady warming back to above seasonal levels through the middle of
the next week, with more isolated diurnal convective activity.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 327 PM MDT Thu Jun 20 2019
High based thunderstorms producing localized erratic gusts up to 45
mph will be possible through early evening for the KCOS and KPUB
terminals while KALS stays dry. Cigs will remain VFR. A cold front
will bring a northerly wind shift through KCOS and KPUB overnight
into early Friday morning with winds shifting around from the east
to southeast in the afternoon. The front will lift back northward
with gusty southwest winds spreading back into KPUB by late
afternoon. KALS will also see a return of gusty southwest winds to
around 30 kts shortly before noon on Friday.
Thunderstorms will be most likely to impact KCOS during the late
afternoon and evening hours with VCTS possible at KPUB. KALS will
remain dry. These storms could produce some large hail and erratic
gusty winds along with brief MVFR visibility due to heavy rain for
the KCOS area through Friday evening. -KT
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...KT
LONG TERM...MW
AVIATION...KT
Area Forecast Discussion
National Weather Service Blacksburg VA
808 PM EDT Thu Jun 20 2019
.SYNOPSIS...
A cold front will move over the Mid Atlantic to produce more
showers and thunderstorms. Drier weather will arrive for Friday
as high pressure builds overhead. A warm front brings a return
of humid air and showers and thunderstorms later this weekend
and into the beginning on next week.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 530 PM EDT Thursday...
Severe Thunderstorm Watch has been cancelled.
Still watching the storms in central North Carolina, but overall
instability of the air mass is weaker. Also tracking the storms
approaching out of the Tennessee Valley.
The environment is still warm and humid as has been the case for
the past several days. With the cold front arriving by evening
along with a decent wind jet at 850 mb noted in the model
soundings reaching 40-50 knots, shear is notably higher compared
to the previous days. There will be some gusty gradient winds
noted at the surface during this time as well.
Once the cold front passes offshore by tonight, drier air should
spill into the Mid Atlantic and allow skies to clear. The
exception will be in southeast West Virginia where upslope
showers and cloud cover will linger into Friday morning but
eventually taper by Friday afternoon. Temperatures will be a
touch lower overall due to the lower dewpoints and the cool air
advection from northwest flow. Low temperatures for Friday
morning were bumped downward a degree or two to accommodate for
these factors.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 300 PM EDT Thursday...
Any reprieve in wet weather Friday will likely come to an end
Friday night into Saturday as yet another convective complex on
the nose of the return of warm and moist air...warm front...is
expected to ride around the periphery of a developing upper
ridge over the Gulf of Mexico, finally turning east and then
southeast from out of the central plains toward the mid-
Atlantic region - resulting in an increasing threat for
showers/storms to move east to at least areas west of the Blue
Ridge late Friday night into Saturday morning - and all areas by
afternoon as warm moist advection increases coupled with
daytime heating and influence of residual outflow boundaries
from earlier upstream convection.
Slowly increasing heat and humidity as the Gulf of Mexico upper
ridge continues to build, and a continuation of ridge-running
convective complexes will then likely maintain a threat for
scattered showers/storms for the rest of the short-term forecast
period (Saturday night through Sunday night)- even during nighttime
periods when less overall activity would normally be expected.
Timing/arrival of each convective complex is still somewhat
problematic since each has yet to develop, and will be mesoscale in
nature rather (than synoptic-scale) - each of which also having a
significant potential to impact cloud cover and temperatures
(especially by day, when contamination by cool outflow boundaries
will significantly influence the normal diurnal temperature curve).
Overall, though, expect a return to higher humidity that will
linger into the beginning of next week.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 300 PM EDT Thursday...
Amplified upper ridge axis from the Gulf of Mexico north into
the TN and OH valley will gradually shift east toward the Mid-
Atlantic by Monday, along with apex of the increasing heat and
humidity. 850H temps of +20 deg C are advertised, which should
allow temperatures east of the Blue Ridge to reach the lower
90s, promoting heat indices in the mid to upper 90s.
Late Monday, a rather strong shortwave trough aloft looks to
topple the ridge and will drag a weakening cold front across the
Appalachians and mid-Atlantic region. This is expected to bring
a good chance for thunderstorms areawide, in addition to a few
strong to severe storms. A surface cold front associated with
the shortwave trough is expected to pass through the area
Tuesday, temperatures taking a step down, although still close
to, or slightly above the June climatological norm.
Lack of any significant upper support for Wednesday-Thursday
suggests any shower/storm threat will be unorganized, mainly
diurnally driven and confined mainly to the mountains.
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
As of 755 PM EDT Thursday...
Isolated to scattered showers and thunderstorms with MVFR
ceilings and visibilities were ahead of a cold front from
eastern Ohio to central Tennessee. SPC HRRR and HiRes-arw showed
a majority of the precipitation outside of the upslope areas of
the central Appalachians dissipating by 04Z/midnight.
In the upslope areas of southeast West Virginia, showers will
continue through early Friday morning. Strong west to northwest
upslope winds will lead to MVFR ceilings in the mountains
overnight. These lower ceilings may extend as far east as KBCB.
Ceilings will lift and clouds will become scattered on Friday
morning as drier air moves into the region. Expect KLWB and KBLF
to be VFR by 18Z/2PM. East of the Blue Ridge will be VFR
throughout the day.
Gusty WSW winds are expected tonight. Wind gusts will be 20 to
30 knots, with 40 knots possible above 4000ft. Strong winds will
continue out of the northwest tomorrow behind the cold front
with gusts of 25 to 35 knots.
Confidence is above average for duration and timing of
precipitation, winds, ceilings, and visibility.
.Extended Aviation Discussion...
Winds should lighten under VFR conditions as high pressure
settles overhead during Friday night, but it will depart
offshore by Saturday morning. A warm front should head north
during Saturday afternoon to bring more moisture. As a result,
showers and thunderstorms should return during late Saturday
through Tuesday with MVFR conditions possible in the strongest
storms. MVFR may also be possible due to any low clouds or fog
during the early morning hours, especially in the mountains.
&&
.HYDROLOGY...
As of 200 PM EDT Thursday...
Showers and thunderstorms will be moving at a good pace due to
good steering currents aloft, but they will still be highly
efficient in rainfall due to precipitable water values still over
1.5 inches. However, the threat for localized flash flooding
remains present if the storms train repeatedly over the same
locations during this afternoon into the evening before the cold
front crosses overhead by tonight.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...PW
NEAR TERM...AMS/PW
SHORT TERM...WERT
LONG TERM...PM
AVIATION...AMS
HYDROLOGY...PW