Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/29/17
Area Forecast Discussion
National Weather Service Wakefield VA
933 PM EDT Fri Jul 28 2017
.SYNOPSIS...
A low pressure system and associated cold front will slide
into the area tonight, then push offshore Saturday into
Saturday night. High pressure builds in early to mid next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Update...
The current forecast is generally on track. Looks like the
heaviest rainfall has set up across the northern tier of our
forecast area including the MD eastern shore where SBY has seen
over 3 inches of rain. Some very impressive rainfall estimates
over the Northern Neck as well with radar showing 5+ inches with
flooding reported. In addition, in NE NC there has been a
pocket of heavy rain which produced flooding in Northhampton and
Hertford Counties. Unfortunatly, much of the very dry area in
the Piedmont still has not seen much rain this evening.
The latest runs of the HRRR have greatly backed off
precipitation west of I-95 tonight as the dry air over WV wraps
into the area as the low moves east. As such, have started to
trend PoPs back in those areas tonight especially after 06z as
the low moves east. Should see continued moderate to locally
heavy rainfall across the eastern shore of MD and see no reason
to modify PoPs there, or to change the flood watch. The flood
watch across the northern tier of our VA counties is a little
tricky as this area will see a lull in pcpn for awhile. However,
the latest HRRR suggests that another area of heavy rain will
develop overnight in the same general location. It is possible
that the heaviest rain will stay north but given that the
boundary is currently over that area, do not want to trim any of
the watch away for now. Since there continues to be moderate
rainfall and flood advisories in NC, will continue the flood
watch there as well, but it possible this will be cancelled
early.
Previous Discussion...
A new flash flood watch has been issued for Northeast North
Carolina...where up to 3-4 inches have already fallen, and
another 2-4 inches is possible. Other inherited flash flood
watch also remains in place for NE portions of the area for
heavy rain expected later on tonight. Overall, previous thinking
remains on track with a cold front dropping into the area this
evening as a mesolow forms along it, with forcing for ascent
also provided by an approaching potent mid-level shortwave
trough. Expect moderate to heavy rain to overspread the area
this eveng, and will last through tonight as the front will be
slow to slide through the area alongside strong DCVA. Low temps
tonight in the upr 60s to mid 70s.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY/...
The front stalls over SE VA/NE NC on Saturday before shifting
southeast of the area late Saturday night. Overall, sfc high
pressure builds across the Midwest as the upper low/opening
trough sits over the Mid Atlantic Coast through early next week
before shifting ewd and away from the coast. Showers/storms will
be focused along the coast with more widely scattered storms
possible farther inland due to elevated lift present with the
upper low. Precip chances expected to wane late Saturday night
into Sunday as the front gets shunted farther SE. Once again,
primary threats from any thunderstorms Sat/Sat night will be
moderate to heavy rainfall, locally strong wind gusts, and
frequent lightning.
Widespread precipitation, cloud cover, and cooler Canadian air
with the upper trough will keep temperatures 5-10 degrees below
normal Saturday. Highs Sat in the mid 70s NW to lower 80s SE.
Low temperatures cool off nicely with lows each night near 60
NW to mid-upper 60s SE.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Trough axis slides offshore Monday as a pleasant and dry air
mass (for early August) spreads over the local area. High
pressure builds into the region Monday, locating over the Mid-
Atlantic Tuesday. Highs Monday generally in the low to mid 80`s,
warming into the mid to upper 80`s Tuesday. Morning temperatures
Monday morning may drop into the 50`s inland. High pressure
slides offshore Tuesday night as a cold front drops over the
Great Lakes. Temperatures and dewpoints moderate Wednesday
thanks to return flow. More seasonable highs expected Wednesday,
generally in the upper 80`s to low 90`s. The cold front progged
to reach the Ohio Valley, sharpening the lee/thermal trough over
the Piedmont. Moisture return results in slight chance PoPs
northwest Thursday for diurnally driven showers/thunderstorms.
Highs Thursday again in the upper 80`s to low 90`s. Medium range
guidance begins to lift the coastal front northward Thursday
night and Friday as an upper level trough digs over the Ohio
Valley. The cold front approaches from the northwest. Have
slight chance to low end chance PoPs for Friday based on the
latest model consensus. Seasonable highs again, generally in the
upper 80`s to low 90`s.
&&
.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
Showers and thunderstorms moving across the region this evening
ahead of the low pressure/cold front. Any site this evening
could drop to MVFR or even IFR with any heavier shower or storm.
The low will move off the coast later tonight, which should
allow all sites to drop to MVFR, with SBY and ORF dropping to
IFR with moist N-NE flow off the ocean. Ceilings will stay in
the MVFR or IFR range on Saturday for all locations with N-NW
flow.
Impoving condtions expected for Sunday into next week as high
pressure builds across the area leading to VFR conditions.
&&
.MARINE...
S-SW winds aob 15 kts continue ahead of the approaching cold front
tonight. Fropa Sat morning with a wind shift to the N. Decent surge
noted in the data behind it but may lag a few hours as the low will
be slow to move off the coast.
SCA`s will go up starting Sat afternoon/eve and continue thru Sun
(end of the 4th period). After coord with PHL, will upgrade gale
watch to a warning for the coastal waters north of Cape Charles with
gusts to 35 kts Sat night. Otw, will cap gusts at 30 kts for now.
Seas will rapidly increase in response to the increased winds. Given
the strong onshore flow, nearshore waves may approach high surf
criteria of 8 ft in the gale warning area. 5-8 ft across the south.
Winds slowly subside Mon as the low pulls farther away and the
gradient relaxes. However, the persistent NE flow and
developing long period swell will likely keep rough surf
conditions going through mid week with seas not falling below 5
ft until late Tue.
&&
.TIDES/COASTAL FLOODING...
Rip current wise, will allow Sat to be the transition day with a
moderate risk all areas (may start off low across the south then
increase as the winds shift behind the front). At this point, expect
Sun to be high risk all areas along with a possible high surf advsry
north.
Some minor flooding issues are possible Sunday/Mon along the coast
and in the lower Bay with the strong N/NE flow behind the departing
sfc low and associated cold front.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Flash Flood Watch through Saturday evening for MDZ021>025.
NC...Flash Flood Watch until 8 AM EDT Saturday for NCZ012>017-
030>032-102.
VA...Flash Flood Watch through Saturday evening for VAZ064-075>078-
084>086-099-517>522.
MARINE...Gale Warning from 4 PM Saturday to 6 AM EDT Sunday for ANZ650-
652-654.
Small Craft Advisory from 7 PM Saturday to 4 PM EDT Sunday for
ANZ633-634-656-658.
Small Craft Advisory from 2 PM Saturday to 4 PM EDT Sunday for
ANZ630-635-636.
Small Craft Advisory from 5 PM Saturday to 4 PM EDT Sunday for
ANZ631-632-637-638.
&&
$$
SYNOPSIS...MAS
NEAR TERM...MAS/MRD
SHORT TERM...MAS
LONG TERM...SAM
AVIATION...MRD
MARINE...MPR
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Albany NY
1027 PM EDT Fri Jul 28 2017
.SYNOPSIS...
Dry weather is expected through the weekend into early next
week as high pressure dominates. The only exception is for the
chance for some very light rain across a portion of the mid
Hudson Valley and northwestern Connecticut on Saturday morning.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
As of 1027 PM EDT...A stalled out frontal boundary is draped
across the mid-Atlantic States and northeast towards eastern New
England. An area of low pressure is located along this
boundary, with widespread showers/thunderstorms for areas south
of the region. The 3km HRRR suggests all this activity should
slide eastward through the night, but remain to the south of the
area.
However, plenty of mid and high level clouds are streaming
northward across our area from the south. While it looks to
remain dry, most of the region will see a good deal of high
level clouds tonight. The exception may be across far northern
areas, where there may be a few more breaks between the thin
cirrus clouds in place.
Surface high pressure is building into the area from the Great
Lakes and southern Canada. With a low- level breeze out of the
north, drier air is advecting into the region, with dewpoints
falling into the 50s. The combination of the breeze, drier low
level air and cloud cover should prevent widespread radiational
fog from forming tonight over most of the area. The exception
may be some river valleys and lakes across the Adirondacks and
southern Vermont, where some patchy fog could develop right
around daybreak. Otherwise, skies will be partly to mostly
cloudy overnight.
Lows will range from the upper 40s across some of the western
Adirondacks into the lower 60s in the mid Hudson Valley.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
Any chances for rain associated with low passing to our south
should be limited to Saturday morning across the southern most
portion of the forecast area; then increasing sunshine as
ridging builds in from the Great Lakes region. The surface high
will dominate with some ridging building in aloft on Sunday and
Monday. Below normal temperatures Saturday by about 10 degrees
will moderate with seasonable warm readings in the mid 70s to
lower 80s for Monday with lots of sunshine. Dew points will be
at comfortable levels in the 40s and 50s Saturday/Sunday and in
the 50s Monday.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
This will be a period of slightly above normal temperatures with the
exception of Friday. Weak, slowly progressing systems will keep
humidities high, and showers and thunderstorms a good possibility
anywhere frontal boundaries abound. High pressure at the outset
will gradually succumb to the effects of a cold front by Wednesday,
though with the first widespread round of showers and storms. PoPs
will be only around 30 percent.
Thursday will represent a better chance for this activity as the
front enters New York from southeastern Ontario province. This
front will continue to sink slowly southeast through the forecast
area Thursday and Thursday night, but the front will become quasi-
stationary, and showers and storms will continue through Friday.
Tuesday will be the mildest day...with high temperatures ranging
from the lower 70s in the high peaks of the Adirondacks...to the
upper 80s down the Mid-Hudson Valley. Each day will become
successively cooler, though, as clouds and cooling rains increase.
Friday will be even cooler with the frontal passage...and highs
that day will range from the mid and upper 60s in the
mountains...to around 80 degrees in the lower Mid-Hudson Valley.
Upper 50s to mid 60s will be the typical range for overnight
lows through the period.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions are expected through the entire TAF period ending
at 00z Sunday.
A wave of low pressure will be moving along a stalled frontal
boundary across the mid-Atlantic states. Any of the rainfall
associated with this feature looks to stay south of the area.
As seen on the latest visible satellite imagery, SCT-BKN cirrus
clouds will continue to stream across the area tonight. Some
lower clouds are possible this evening as well, but these should
mainly dissipate over the next few hours. The exception may be
at KPOU, where some lower clouds are possible due to being
closer to the passing low pressure area. Light N-NE winds
overnight will be around 5 kts for all sites.
With drier air working into the region from the north (dewpoints
falling through 50s into the upper 40s), widespread radiational
fog doesn`t appear to be an issue tonight. However, some patchy
fog may develop over river valleys and lakes thanks to the
mainly clear skies, especially for northern areas. It`s
possible that a brief period of fog could occur at KGFL around
sunrise, but confidence in this is too low to include in the TAF
at this time.
During the day on Saturday, the amount of cirrus clouds should
gradually decrease throughout the day and any lower clouds near
KPOU should decrease as well. Most sites will just see FEW-SCT
cirrus by the afternoon and evening hours. Northerly winds will
be around 5-10 kts, with the highest winds at KPSF.
Outlook...
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: No Operational Impact. NO SIG WX.
Sunday Night: No Operational Impact. NO SIG WX.
Monday: No Operational Impact. NO SIG WX.
Monday Night: Low Operational Impact. NO SIG WX.
Tuesday: Low Operational Impact. Slight Chance of SHRA...TSRA.
Tuesday Night: No Operational Impact. NO SIG WX.
Wednesday: Moderate Operational Impact. Chance of SHRA...TSRA.
&&
.FIRE WEATHER...
Dry weather is expected through the weekend into early next
week as high pressure dominates. Minimum relative humidity
values are forecast to be mainly in the 40s Saturday afternoon
with 30s across the western Adirondacks with values in the
35 to 45 percent range Sunday afternoon. Relative humidity
values will recover to 80 to 90 percent at night.
&&
.HYDROLOGY...
Dry weather is expected through the weekend into early next
week. The only exception is for the chance for some very light
rain across the far southern most portion of the forecast area
overnight into Saturday.
For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.
&&
$$
SYNOPSIS...IAA/Frugis
NEAR TERM...IAA/Frugis
SHORT TERM...IAA
LONG TERM...ELH
AVIATION...Frugis
FIRE WEATHER...IAA
HYDROLOGY...IAA
Area Forecast Discussion
National Weather Service Dodge City KS
544 PM CDT Fri Jul 28 2017
...Updated aviation section...
.SHORT TERM...(This evening through Saturday)
Issued at 340 PM CDT Fri Jul 28 2017
Upper level high pressure was centered over the southern Plains
today. Water vapor loops show numerous disturbances rotating
around the high located over the Great Basin, New Mexico and east
Texas. A very moist airmass is in place over the central High
Plains this afternoon. Dewpoints are in the mid 60s to around 70
over the western half of the forecast area. Plenty of instability
in that area with mixed layer CAPE values around 2000-2500 j/kg.
Surface convergence in this area is lacking so in spite of an
expansive cumulus field, no convection is apparent. Short term
CAM`s like the HRRR and RAP have been trending to keep any storms
out of southwest Kansas this evening with the better chances for
something rolling out of the Front Range later tonight. Have
reconfigured pops for tonight...backing off until later in the
night or closer to sunrise on Saturday and keeping pops confined
to the western sections of the cwa.
Models are showing different solutions on how long precipitation
will linger into the day on Saturday as well as the location and
coverage which is typical in this type of weakly forced
environment. Based on what little model consensus there is, and
collaboration with neighboring offices, have maintained some
chance pops on Saturday morning generally along and north of
Highway 156 with smaller chances farther south. Better chances for
thunderstorms are expected to develop out near the Colorado border
late Saturday afternoon and evening.
.LONG TERM...(Saturday night through Friday)
Issued at 340 PM CDT Fri Jul 28 2017
The medium range models (GFS/ECMWF/GEM) have been a little more
consistent with the possibility of a heavy rain event developing
somewhere over northeast Colorado into northwest and west central
Kansas Saturday evening into Sunday. The models have been hinting
at this for the past few days with run to run and model to model
variability as to where the greatest heavy rain impacts will be.
It appears that the disturbance moving up through New Mexico will
rotate out into eastern Colorado by tomorrow afternoon and
evening, helping focus thunderstorms into a complex that will move
out into western Kansas Saturday night and Sunday. What model
consensus there is seems to put the axis of heaviest rain along
the Highway 96 corridor. After a conference call with WPC and
collaboration with neighbors to the north, have increased pops and
qpf values across that area into Sunday morning. Given the very
moist airmass and high precipitable water values, there will
likely be a heightened threat for flash flooding but will hold
off on any headlines for now.
The models continue to show a trend toward the upper level high
pressure area retrograding westward over the Great Basin through
the mid to latter part of the upcoming week. This will keep
temperatures at more seasonal, if not cooler, levels through the
week along with nearly daily chances for showers and thunderstorms
especially over western parts of the forecast area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 543 PM CDT Fri Jul 28 2017
VFR conditions are expected through the period with a small
probability for some MVFR across parts of southwest Kansas for a
few hours around 12z Saturday. Winds will generally be from the
southeast at less than 10 knots.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 67 88 64 80 / 20 20 50 70
GCK 67 86 64 78 / 30 40 80 60
EHA 66 88 64 84 / 30 50 50 40
LBL 69 89 66 84 / 20 30 40 30
HYS 67 86 65 77 / 20 30 50 60
P28 68 90 67 82 / 10 10 10 30
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Gerard
LONG TERM...Gerard
AVIATION...Hovorka_42
Area Forecast Discussion
National Weather Service Hastings NE
956 PM CDT Fri Jul 28 2017
.UPDATE...
Issued at 955 PM CDT Fri Jul 28 2017
Just completed an update, mainly to slightly increase the chances
of measurable rainfall (PoPs) overnight for especially the
western 1/3 of our coverage area (CWA).
The latest consensus of various models including the HRRR and the
new 00Z NAM (including the higher-res Nest) suggest that the
combination of a weak mid level wave embedded in northwest flow
aloft, along with modest instability/CAPE but halfway decent
forcing mainly in the 850-700 millibar layer will promote
increasing rain chances especially post-midnight and especially
for areas near/west of Highway 183. Still did not have the
confidence to go "likely" 60+ percent chances, but did bump up to
50 percent in the far west, tapering down to only 20 percent along
the Highway 281 corridor and not reaching there until very late in
the night/toward sunrise. Our eastern couple columns of counties
along/east of Highway 14 will most likely stay dry through the
night. With CAPE averaging only 200-500 J/kg at most, am not
expecting severe storms, but probably cannot rule out some gusty
winds and small hail, and even locally heavy rainfall in excess of
1" in a FEW spots given slow storm motions and precipitable water
values up around 1.5". Have refreshed the Hazardous Weather
Outlook to refine this thinking a little.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 309 PM CDT Fri Jul 28 2017
A broad ridge of high pressure extends across the local area with
multiple weak disturbances caught in its circulation potentially
sparking some convection across portions of the local area
beginning late tonight. With very limited instability to work
with locally...the odds of this convection resulting in widespread
or strong convection is very low...and only anticipate isolated
to widely scattered storms during the overnight hours...limited
to areas primarily west of highway 281 where the best forcing and
instability will reside.
For tomorrow...expect variable cloud cover to stream across the
local area...with additional chances for showers or thunderstorms
once again confined to areas primarily west of highway 281. With
the weak instability and unorganized nature of any storms that do
develop...severe weather is not anticipated. Temperature
wise...expect a near repeat of today as there will be little
change in the underlying airmass...with low temperatures falling
into the lower 60s in most spots...and afternoon high temperatures
reaching the lower to middle 80s.
.LONG TERM...(Saturday night through Friday)
Issued at 309 PM CDT Fri Jul 28 2017
Near seasonal temperatures along with periodic...non-severe
chances for thunderstorms...can be expected through the extended
periods. Overall...expect the broad upper level ridge across the
intermountain west to gradually expand north and east through the
end of next week...with little change in the local airmass
resulting in continued "mild" summertime temperatures across the
region. In addition...periodic...weak disturbances will bring
multiple chances for showers and thunderstorms to the local
area...with limited instability and shear keeping the chance for
severe thunderstorms across the local area to a minimum. While
there are chances for thunderstorms nearly every day of the
extended...actual coverage will likely be fairly low and some
areas could actually remain dry throughout the period.
There is some discrepancy in long term guidance...however..with
the EC bringing a backdoor cold front across the plains towards
the middle of next week...which if true...should result in more
widespread shower/thunderstorm coverage Wednesday/Wednesday
night...along with well below normal temperatures towards the end
of the period. Given the discrepancy...did not stray from blended
guidance which continues with the aforementioned periodic chances
for shower and thunderstorm activity along with more summerlike...yet
mild...temperatures.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday)
Issued at 707 PM CDT Fri Jul 28 2017
General overview:
Will call for VFR conditions in the official TAF products, but it
could be a close call especially ceiling-wise during the latter
half of the period Saturday. Otherwise, there is a chance of
isolated-scattered thunderstorm activity mainly during the 09z-18Z
time frame, favoring KEAR a bit more than KGRI. Surface winds
should not be a big concern (apart from any convective
influences), averaging around 10kt or less from mainly a southeast
direction. Read on for more element-specific info...
Ceiling/visibility:
Although am not currently expecting visibility to drop to MVFR in
light fog again late tonight/Saturday morning, will at least
"hint" at the slight possibility with a mention of "6SM BR" from
09-14Z. Ceiling-wise, VFR should prevail especially through the
first 12 hours, but the latter half during the day Saturday could
feature quite a bit of cloud cover to at least the low-end VFR
level, and later forecasts will have to monitor closely for MVFR.
Shower/thunderstorm chances:
Confidence is fairly high that both terminals are convection-free
through roughly 09Z or so tonight, at which time will start a
"vicinity" (VCTS) mention at KEAR that runs through 18Z. At least
for now, have actually removed any VCTS mention for KGRI as it
seems just "barely" too far east to justify it, but this will need
watched closely as well. Convection also cannot be ruled out
during the final 6 hours of the period Saturday afternoon, but
will defer to later forecasts to introduce anything this far out.
The risk of severe storms seems quite low at this time.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
UPDATE...Pfannkuch
SHORT TERM...Rossi
LONG TERM...Rossi
AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1030 PM EDT Fri Jul 28 2017
.SYNOPSIS...
A strong cold front will cross the region from the west through
tonight. Cooler and drier air will arrive across the western
Carolinas and northeast Georgia through the weekend and linger
through the early part of next week. More typical summertime
conditions will return about the middle of next week.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 1015 PM: Low-level trough appears to be oriented from
southern Middle TN eastward along the southern border of TN and NC,
while the sfc front is still pushing across the Kentucky Bluegrass
region. Within the trough, some light showers are present over the
mtns. A slight increase in shower coverage has recently occurred
over north GA. Per 00z RAOBs and SPC mesoanalysis, there are still
a few hundred joules of elevated buoyancy, so it should be taken
as no surprise in light of the convergence at work. HRRR and NAM
now depict showers progressing across the CWFA overnight. This
already a bit overdone, and yet I am still wary of lowering PoP
below slight chance until early morning.
With low level moisture remaining abundant, and mid/upper level
clearing, fog formation is possible late tonight, especially in
sheltered areas, where it could become locally dense. Much of
the area was worked over with heavy rainfall and these areas are
also at particular risk. That said, temps have trended a little
warmer overnight, which suggests slightly less fog than previously
thought. Deeper moisture and wind shift associated with cold front
is expected to ooze to our southern areas, or just to our south by
sunrise Saturday. Token small pops will be maintained in these areas
through the day, as well as across the mtns (for a relatively moist
NW flow), and across the eastern zones (due to upper level thermal
trough developing in association with Mid-Atlantic upper low).
Otherwise, drier and stable air will preclude the need for pops
elsewhere, while lower thickness values will support max temps
slightly below climo.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 200 PM EDT Friday: A deep trough will extend southwest from a
closed low pressure system over the DelMarVa area through the
western Carolinas Saturday night through Sunday. Deeper moisture
will wrap southward around the back side of the system to contribute
some cloudiness to the northern tier, but any shower chances
Saturday night into early Sunday look rather low. Northerly cold
advection flow will maximize during this period with thicknesses
bottoming out across the region to produce min/max temps 1 to 2
categories below climo.
Meanwhile, at the surface sprawling high pressure will build from
the upper Midwest to the east coast and nose southward through the
western Carolinas and northeast Georgia through Monday. Modest
surface dewpoint recovery will begin in southwest sections by Monday
afternoon, but the potential for any southwest mountain ridge
diurnal convection looks quite limited.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 210 PM EDT Friday: The eastern trough will broaden in the
Tuesday to Friday timeframe as it gets reinforced by rounds of
digging shortwave energy arriving from Manitoba and Ontario. Under
the developing broad ridge, the airmass over the southeast will
continue to modify through the week with temperatures gradually
returning to normal. Diurnal convective coverage from terrain
forcing will increase each afternoon Tuesday through Thursday.
Deeper moisture will pool ahead of a cold front approaching from the
northwest on Friday to generate above climo PoPs.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: A second round of showers or even a stray TS
is possible over the more northern parts of the area, as remnant
of semi-organized convective line moves out of TN this evening,
as a result of a southward moving cold front. However, the main
impact wx tonight will be fog and low stratus forming ahead of
that front given the abundant moisture. Guidance is surprisingly
sparse in depicting restrictions, but LAMP and HRRR seem to have
taken into account some effect from the earlier storms, and depict
IFR vsby in mtn valleys and MVFR cigs/vsby developing over parts
of the Piedmont in the wee hrs of the morning. This is the most
plausible solution available at TAF time. Dewpoint depressions
being small, I will not be surprised if there are at least brief
periods of MVFR to IFR conditions this evening. The good news is
that the front looks to provide enough drying that restrictions
should dissipate quickly around sunrise. A NW-ly wind shift will
occur around that time as well.
Outlook: Still drier air will filter in from the north behind
a passing cold front over the weekend. Chances for morning
fog and stratus will also be possible mainly in the mountain
valleys. Diurnal convection will remain suppressed through early
next week, but a typical summertime pattern is expected to return
by the middle of the week.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 98% High 81% High 100% High 100%
KGSP High 90% High 91% High 100% High 100%
KAVL High 84% Med 65% High 96% High 100%
KHKY Med 78% Med 78% High 100% High 100%
KGMU Med 78% High 87% High 100% High 100%
KAND High 95% Med 74% High 100% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...HG
NEAR TERM...JDL/Wimberley
SHORT TERM...HG
LONG TERM...HG
AVIATION...Wimberley
Area Forecast Discussion
National Weather Service Key West FL
906 PM EDT Fri Jul 28 2017
.DISCUSSION...In the mid to upper levels(700-200 mb) latest
available satelitte imagery overlaid with model streamline
analysis as of 800 pm, depicts the west northwest to east
southeast tilted center of a massive typical middle and upper
level oriented anticyclone centered over the Red River Valley of
Oklahoma/Texas, with the eastern end of the ridge positioned
across Central Florida. To the south of that feature, a regional
scale upper level low pressure system is located over Central
Cuba.
At the surface and in the lower to middle levels (Surface to 700
mb), latest ir satelitte imagery overlaid with marine and land
surface observations and analysis as of 8 pm, details a cold front
presently extending from Southern New England southwest to the
Mid-Tennessee Valley. A weak trough extends from the front down
into Georgia/North Florida. Locally, the western periphery of an
anticyclonic ridge reaches to just east of the Northern Bahamas. A
weak pressure pattern is in place across South Florida, the
Florida Keys, the SE Gulf of Mexico, Florida Straits, and Central
and Western Cuba. As such the 00Z sounding illustrated light to
gentle and southwest just off the surface all the way up to 300
mb, with a moist lower to mid troposphere and columnar PWAT at
2.07 inches.
.CURRENTLY...As of 800 am, skies have become mostly clear, as all
remnant debris clouds from earlier cumulus/towering cumulus cloud
lines have almost all but dissolved. Hence, radar is devoid of
any echoes attm. Temperatures across the islands remain in the
middle 80s with dewpoints in the upper 70s. C-man stations across
the islands are recording variable winds at 5 knots or less, and
island sensors are variable at 5 mph or less.
.SHORT TERM...Overnight, middle level heights remains steady with
about 588 dm at 500 mb. The surface cold front over the SE will
only make some progress southwards. As a result, the Keys will
remain in and near a surface col. Latest HRRR suggests some
reinvigoration of a several dormant boundaries near the Upper and
Lower Keys, but any overall coverage of short lived showers and
thunderstorms will remain isolated, given a very small 0-6 km
storm motion of 5 knots or less indicated in both the GFS and
ECMWF forecast soundings. The 0-6 km wind profile is progged to
be southwest by morning (12Z), as a meso-ridge develops just
south of the Florida Keys across the Florida Straits. This could
set up a favorable environment rather early, for a morning cloud
line episode.
&&
.MARINE...Light and variable winds overnight will become light to
gentle southwest breezes during Saturday. On Saturday, Look out
for waterspouts beginning in the morning, as waterspouts tend to
form along the end of long dark flat cloud bases.
&&
.AVIATION...VFR conditions will prevail at both the Key West and Marathon
terminals overnight. Surface winds will be light mainly out of the
southwest, becoming variable at times. Isolated showers are possible
overnight.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine...Futterman
Aviation/Nowcasts....Devanas
Upper Air/Data Collection......Chesser
Visit us on the web at weather.gov/key
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www.facebook.com/nwskeywest
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Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1046 PM EDT Fri Jul 28 2017
.SYNOPSIS...
A cold front will approach from the northwest today and move
offshore late Saturday. High pressure will build behind the
front Sunday into the middle of next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
As of 1000 PM Friday...Main change was to increase POPs to
categorical for NW third of area through 2 AM with good coverage
of showers and scattered tstms expected. Recent HRRR runs have
trended toward activity moving into coastal plains holding
together along and west of Hwy 17 next few hours, thus enough
confidence to increase POPs. Guidance also continues to indicate
additional development near coast overnight and will keep likely
POPs in place. Cannot rule out isolated downburst overnight with
increasing bulk shear, but believe main threat will be heavy
downpours. No changes to temps.
/Previous discussion/
As of 345 PM Friday...Latest meso-analysis is showing moderate
instability across Eastern NC this afternoon. Showers and
thunderstorms have redeveloped along the Albemarle Sound where
there are lingering boundaries associated from this morning`s
thunderstorms that`s where the main focus will be for this
evening. While unstable conditions will still remain as shear
increases (30-35 knots) and helicity tonight...this can lead to
better organized thunderstorms and cannot rule out a possible
isolated tornado. Expect most of the strong to severe storms
along/north of HWY 264 with the bulk of the heavy rain to occur
after midnight. Tonight`s main threat is damaging gusty winds
and heavy rain.
Late tonight as the instability decrease a bit tonight, expect
widespread showers with embedded thunderstorms. Some heavy
downpours will be likely, but threat of severe weather
diminishes after midnight. Expect overnight lows in the low
mid 70s.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
As of 345 PM Friday...The sfc cold front will slowly drop down
southeast across the Eastern NC, maintaining the threat of
showers and thunderstorms for most of the day. Unstable
conditions will remain along the coastal half with CAPE values
reaching near 3000 J/KG with enhance shear along the
coast...leading to possible active weather. The threat of
showers and thunderstorms will decrease after the cold front
pushes through the area. Cold front is progged to push through
tomorrow afternoon.
Temperatures will be cooler under cloudy and rainy conditions,
expect highs in the low 80s.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
As of 3 pm Fri...An upper low is progged to be off the mid-
Atlantic states with associated sfc low pushing off the VA
coast with the trailing cold front moving off the NC coast.
Convection will end from the west Saturday night. On Sunday
daytime heating plus leftover boundary layer moisture and vort
energy wrapping around the backside of the departing low will be
enough to set off widely scattered to scattered convection.
High pressure builds in from the northwest beginning Sunday
night and will be the dominant feature through the rest of the
week. Models are in better agreement today on the high and the
associated upper ridge leading to better forecast confidence.
The ridge will begin to weaken by the end of the week allowing
moisture to slowly increase from the south. Temps expected to be
near normal in the upper 80s to around 90 inland to mid 80s
coast.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Short Term /through 00Z Sunday/...
As of 715 PM Friday...Current VFR conditions will persist until
02-03Z then showers and scattered tstms with mainly MVFR VSBYs
spreading across from west. Activity likely diminishing after
06Z but redeveloping for mainly KEWN-KOAJ areas 09Z-12Z and
persisting there well into Saturday with approach of cold front.
Precip diminishing after 18Z but MVFR CIGs lingering until
evening. SW winds around 10 KT into Sat morning, becoming W to
NW in afternoon.
Long Term /Sat night through Wed/...
As of 3 pm Fri...Pred VFR conditions expected Saturday night
through Wed with high pressure building into the region from the
northwest. Surface winds will be N 10-15 knots Sunday and
Monday, NE around 5 knots Tuesday and E around 5 knots
Wednesday.
&&
.MARINE...
Short Term /Through Saturday/...
As of 1000 PM Friday...Adjusted forecast to delay stronger winds
and SCA until after 2 AM. Winds have been slower to increase
than expected but latest models all indicate stronger winds by
morning, thus still SCA conditions to develop and persist
through Saturday. Also adjusted seas more in line with WW3 with
heights building to 6 feet outer southern and central waters
near morning.
/Previous discussion/
As of 1 PM Friday...Wind gradient will tighten tonight as the
cold front approaches the area from the NW and high pressure
offshore. S/SW winds will increase to 15-25 knots tonight with
seas building 4 to 6 ft late tonight and peaking tomorrow 5-8 ft
tomorrow afternoon. Small craft advisory remains in effect
south of Oregon Inlet to Surf City and added Pamlico Sound as
winds will increase to 25 knots. Cold front will start to push
through the coastal waters tomorrow afternoon with winds
becoming NW.
Long Term /Sat night through Wed/...
As of 3 pm Fri...Poor boating conditions expected this weekend
as an area of low pressure moves off the VA coast with the
trailing cold front moving off the coast Saturday night. Small
craft conditions Saturday night south of Oregon Inlet will
slowly diminish through early next week. Winds and seas will
subside as high pressure builds into the region from the
northwest. Light winds and seas forecast Tuesday and Wednesday.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...None.
MARINE...Small Craft Advisory from 2 AM to 11 AM EDT Saturday for
AMZ135.
Small Craft Advisory from 2 AM Saturday to 5 AM EDT Tuesday
for AMZ152-154-156-158.
Small Craft Advisory from 5 AM Sunday to 5 AM EDT Tuesday for
AMZ150.
&&
$$
SYNOPSIS...BM
NEAR TERM...JBM/BM
SHORT TERM...BM
LONG TERM...HSA
AVIATION...JBM/HSA/BM
MARINE...JBM/HSA/BM
Area Forecast Discussion
National Weather Service Nashville TN
638 PM CDT Fri Jul 28 2017
.UPDATE...
FOR 00Z AVIATION DISCUSSION.
&&
.DISCUSSION...
Stationary boundary now draped west to east across the mid state.
We do see pressure falls centered over AL. Thus, the front is on
the move and we should see drier air continue to work in from the
north. Latest Hrrr data shows shower and thunderstorm activity
ending from north to south by 10 pm. This looks reasonable as
models expected upward velocities to end in a few hours.
For the fcst, will issue an update now and go ahead and clean out
the late aft wording. Will update late this evening, as well, once
the precip terminates.
&&
.AVIATION...
00Z TAF DISCUSSION.
Chances for showers and thunderstorms will hang around for a few
hours this evening before moving out the the area. A few models
bring in MVFR and even IFR cigs, which mainly will impact KCSV.
Other terminals may see MVFR cigs as well, but left out mention
for now. May need to add in lower cigs should satellite
trends and model guidance get on board. Fog may also be possible
with the surface moisture from earlier rainfall, so for now have
mention at KCSV and KCKV. Otherwise expecting VFR conditions by
late tomorrow morning with NNE winds around 10 knots gusting from
15-20 knots by the afternoon.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......21
AVIATION........Barnwell
Area Forecast Discussion
National Weather Service New York NY
1103 PM EDT Fri Jul 28 2017
.SYNOPSIS...
Low pressure tracks across the Mid-Atlantic States overnight,
then south of Long Island on Saturday. The low moves farther off
into the Atlantic Saturday night. High pressure builds to the
northwest Sunday through Wednesday. A cold front approaches from
the northwest.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Latest HRRR and radar trends would suggest the area is mainly dry
through most of the overnight hours. 00z NAM shows weak northern
stream ridging (700-500 hPa) and a vorticity minima over the
area at 00z, with these features expected to break down/move on
by around 09z. As a result, have lowered pops further overnight,
but still have low end chance pops along far S zones towards
9z.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Updated pops during first few hours of Saturday downward. If 00z
NAM is correct, could see just Fire Island and coast of SE Long
Island getting brushed with light rain, and nothing more.
Any rain tapers off from northwest to southeast during the
afternoon with dry conditions anticipated Saturday night. From
Saturday afternoon through Saturday night, the upper level
trough axis passes further southeast of the area with negative
vorticity advection moving into place. This will increase
subsidence and help make for drier conditions during this
timeframe.
Temperatures were taken from a blend of ECS/GMOS/NAM12 for highs
Saturday and a blend of MET and GMOS for lows Saturday night.
Mid 70s to near 80 expected for highs and mid 50s to mid 60s for
lows.
There is a high risk of rip currents at Atlantic Beaches on
Saturday.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Trend with sfc low passing well to the southeast continues Sunday
into Monday. Global models in agreement on dry weather Sunday and
Monday.
Aloft, upper trough will slowly drift east Sunday through Monday,
weakening in time. Weak flow behind this trough prevails Tuesday
through Wednesday. Then upstream trough amplifies as it slowly
tracks east, extending across the Great Lakes region and the Ohio
Valley, with lowering heights the result for our area late week.
At the sfc, waves of low pressure ride along a stalled front well to
the southeast Sunday into Monday. High pressure builds to the west.
Daily sfc troughs develop mid week, then a cold front makes progress
toward the area Thursday and Friday.
As for sensible weather, dry conditions expected through Wednesday,
with perhaps an isolated afternoon/early evening shower/thunderstorm
Tuesday and Wednesday. This would be mainly across the interior.
Showers and thunderstorm chances increase just a bit Thursday and
Friday with the approach of the front/trough.
Temps will remain around seasonal norms, with perhaps readings a few
degrees above early to mid week. In general, do not foresee large
swings in temps with this expected pattern.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Low pressure develops over the Middle Atlantic tonight and then
tracks south and east of Long Island on Saturday.
Light NE winds increase less than 5 kt overnight increase and become
gusty near 25 kt by 12-15z Saturday morning at coastal
terminals.
VFR is expected through overnight hours with a few isolated
showers possible. Latest guidance shows widespread rain chances
continue to diminish but will leave -RA in the forecast for a
few hours late tonight into Saturday morning for NYC/coastal
terminals. Flight categories fall to MVFR in the after 10z.
There`s a good chance, however, that NYC terminals and north
remain VFR.
NY Metro Enhanced Aviation Weather Support...
Detailed information, including hourly TAF wind component fcsts, can
be found at http:/www.weather.gov/zny/n90
KJFK TAF Comments: Timing of MVFR conditions late tonight may
be offset +/- 1 or 2 hours. Wind gusts may be delayed a few
hours Saturday morning.
KLGA TAF Comments: Timing of MVFR conditions late tonight may
be offset +/- 1 or 2 hours. There`s a chance flight category
remains VFR. Wind gusts may be delayed a few hours Saturday
morning.
KEWR TAF Comments: Timing of MVFR conditions late tonight may
be offset +/- 1 or 2 hours. There`s a chance flight category
remains VFR. Wind gusts may be delayed a few hours Saturday
morning.
KTEB TAF Comments: Timing of MVFR conditions late tonight may
be offset +/- 1 or 2 hours. There`s a chance flight category
remains VFR. Wind gusts may be delayed a few
hours Saturday morning.
KHPN TAF Comments: Wind gusts may be delayed a few hours
Saturday morning.
KISP TAF Comments: Timing of MVFR conditions late tonight may
be offset +/- 1 or 2 hours. Wind gusts may be delayed a few
hours Saturday morning.
.OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY...
.Saturday afternoon-Night...VFR. NE winds G25-30kt in the afternoon,
diminishing at night.
.Sunday-Monday...VFR.
.Tuesday-Wednesday...VFR. Slight chance of a shower or thunderstorm
NW of NYC each afternoon.
&&
.MARINE...
Minor changes were made with this update to reflect the latest
trends in observations and guidance. The forecast appears on
track.
Conditions stay below SCA overnight. Conditions quickly go to
SCA to gales Saturday in advance of an increasing pressure
gradient with an intensifying low. Although the low is forecast
to pass farther south of Long Island, still have a high chance
of gales across the ocean and less chance of gales across non-
ocean waters. Non-ocean waters will have SCA conditions mainly
for winds, although Eastern Long Island Sound will have for
sometime Saturday afternoon into Saturday evening, some 5 ft
seas. SCA winds last across non-ocean waters through Saturday
evening; eastern non-ocean waters likely all of Saturday night.
Gales last much of Saturday night across the ocean.
Northeast flow Sunday diminishes as high pressure builds to the
west, and waves of low pressure pass well to the east. Ocean
seas remain rough Sunday, then subside as the day and night
progress.
For the early to mid week period, sub SCA conditions are anticipated
across the area waters as high pressure remains to the west.
&&
.HYDROLOGY...
Rainfall amounts tonight through Saturday are expected to range
from less than a tenth of an inch across areas north of Long
Island Sound to 1/10-1/4 of an inch across NYC, Long Island and
most of NE NJ. Little if any hydrologic impact is expected with
this system. However, if the low tracks farther N, or the qpf
shield is displaced farther to the N/W from the storms center
then currently forecast, the potential exists for higher amounts
and an increased flooding threat, especially over NYC/Long
Island and portions of NE NJ.
No significant hydrologic impacts are expected Saturday night
through Friday.
&&
.TIDES/COASTAL FLOODING...
Despite the expected strong northeast winds on Saturday, only
locally minor coastal flooding appears possible on the south
shore bays of western Long Island at this time.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Rip Current Risk from 8 AM EDT Saturday through Saturday
evening for NYZ075-080-081-178-179.
NJ...None.
MARINE...Small Craft Advisory from 6 AM Saturday to midnight EDT
Saturday night for ANZ335-338-345.
Small Craft Advisory from 6 AM Saturday to 6 AM EDT Sunday for
ANZ330-340.
Gale Warning from 6 AM Saturday to 6 AM EDT Sunday for ANZ350-
353-355.
&&
$$
SYNOPSIS...JM/PW
NEAR TERM...Maloit
SHORT TERM...JM
LONG TERM...PW
AVIATION...IRD
MARINE...Maloit/JM/PW
HYDROLOGY...JM/PW
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Shreveport LA
808 PM CDT Fri Jul 28 2017
.UPDATE...
To pops/wx and heat indices this evening.
&&
.DISCUSSION...
Patchy heat islands are still cooking under some low and mid
clouds with 104 this last hour in Shreveport and still 106 at
De Queen awaiting a cooling downpour just minutes away. A good
push of Thunderstorms is coming together over SE OK and SW AR and
just now moving into our CWA. Bumped pops North and lowered
South. We will continue to monitor this activity which may be all
we see out of this front. When it goes the outflow will continue
quickly Southward, taking the rain chances along the way.
&&
.PREV DISCUSSION... /issued 653 PM CDT Fri Jul 28 2017/
AVIATION...
Sct convection will continue to develop this evening over SE
OK/portions of SW AR, along and just ahead of a weak sfc front
that will drift S into extreme NE TX/N LA late tonight. Ahead of
this convection, considerable areas of AC have developed/spread S
into NE TX/N LA, which will result in elevated cigs this evening
from near GGG to MLU. The convection to the N may build SE across
SW AR near the front, and could affect the TXK/ELD terminals
after 03Z, with additional redevelopment possible overnight across
these same areas as they build SE into NE LA through 12Z Saturday
before diminishing. Did delay mention of VCTS for MLU until 05Z,
before the convection weakens/shifts S after daybreak. Have not
inserted mention of VCTS/VCSH elsewhere in the TAFs given the low
confidence of this forecast, although elevated areas of -SHRA will
be possible throughout the morning Saturday over portions of E
TX/N LA before diminishing S of the I-20 terminals by 18Z. Given
the rains that fall this evening over portions of SW AR, can`t
rule out MVFR/possibly IFR cigs developing after 12Z over portions
of SW AR/N LA near and behind the weak sfc front, with these cigs
returning to VFR by midday. Elsewhere, VFR cu cigs should develop
by afternoon as the elevated cigs begin to scatter out in wake of
the fropa across the region. Light S or Lt/Vrb winds tonight will
become NNE 5-10kts after 12Z. /15/
PREV DISCUSSION... /issued 246 PM CDT Fri Jul 28 2017/
DISCUSSION...
Cold front over nrn AR/OK continues to slowly drift swd this aftn.
Convection ahead of it in our region has been slow to develop, and
although relatively steady-state, as actually decreased in
intensity despite daytime heating. Latest HRRR trends seem to back
this up, and slightly better coverage will be possible as the
front dips further swwd tonight.
Drier air to begin filtering in in the wake of the front during
Saturday. However, this drying trend will come too late for
portions of E TX/W central LA, as heat index values over these
areas will likely peak between 105 and 110 degrees. Will likely
need a Heat Advisory again for these areas, unless convection
prohibits, but will defer to the midnight shift to discern
exactly where the advisory needs to be.
After another daytime heating flare up of convection along the
front across our srn areas Saturday, chances for rain will dry up
for a few days. NW flow aloft and a cooler and drier airmass will
send us back to temperatures more typical of late spring or early
summer through midweek.
As the upper ridge retreats well westward over NV, an upper level
disturbance in the nw flow aloft will bring better coverage of
convection for us in the latter half of the work week. This should
continue to give us relief from the recent oppressive heat. /12/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 79 93 71 91 / 30 30 0 0
MLU 76 91 68 89 / 50 40 0 0
DEQ 74 91 67 89 / 50 10 0 0
TXK 75 90 68 89 / 50 20 0 0
ELD 74 90 66 88 / 50 20 0 0
TYR 77 94 73 91 / 20 20 0 0
GGG 78 93 72 91 / 30 20 0 0
LFK 77 95 75 93 / 20 40 20 10
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
24/12