Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/06/17
Area Forecast Discussion
National Weather Service Albany NY
942 PM EDT Tue Sep 5 2017
.SYNOPSIS...
A cold front will slowly move across the region overnight,
bringing showers and thunderstorms, some of which may contain
locally heavy rain and gusty winds, especially areas south and
east of Albany. The front will stall just south and east of the
region as waves of low pressure track along the boundary
through Wednesday night, bringing occasional rain and cool
temperatures. Cool and somewhat unsettled conditions may linger
into Friday before high pressure builds into the region.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
For now, just SHRA activity across the southern 2/3rds of the
CWA. The 00Z ALY sounding showed only about 300 j/kg of MUCAPE.
For this update have kept mention of isolated TRW across the
southeast half of the CWA...mainly east and south of the Capital
District...in for the remainder of the night with SHRA elsewhere.
With the RAP showing atmosphere becoming stable by about 06Z or
so across entire CWA...isolated T threat may be overdone.
Per radar trends and HRRR forecasts have removed heavy rain from
the forecast. No reports received from ongoing flash flood
warning in Litchfield. Will allow the warning to expire at
1030pm.
Updated temperatures to bring in line with current observations.
Temperatures will gradually fall as the front settles south and
east. Lows by daybreak should mainly be in the 50s.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
Wednesday-Wednesday night, consensus of models suggest a
stronger wave of low pressure tracks northward along the frontal
boundary, which should stall across New England. Models also
suggest mid level boundary stalling in a N/S orientation across
the region, with some tightening of the H7-H5 thermal gradient.
So, expect lots of clouds, with periods of rain through this
time, with the best chance of steadiest rain appearing to be
Wednesday afternoon and night. Some locally heavy rain may occur
once again given nearby proximity of deep moisture and also
strengthening mid level forcing. Additional rainfall amts of
over one inch could occur, especially somewhere between the
Hudson River and western New England, including southern VT. It
will remain cool, with highs generally in the 50s and 60s, with
lows mainly in the 50s.
Thursday-Friday, the aforementioned low pressure wave should
slowly move northeast of the region Thursday morning, while the
main upper level trough slowly approaches from the Great Lakes
region. Steadier rain should end Thursday morning, with more
diurnally focused and Lake enhanced showers expected Thursday
afternoon into Friday. With such cool air aloft, can not rule
out some embedded low topped convection with small hail/graupel
with any taller showers. It will be breezy/cool, with highs
mainly in the 60s for valleys, 50s across higher terrain; and
lows ranging from the 40s across the higher terrain, to
lower/mid 50s elsewhere.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
After a low pressure trof from the Great Lakes to southern
Quebec retreats across the Canadian Maritimes Friday night, we
will be entering a period of tranquility all the while as
Hurricane Irma is expected to be wreaking havoc along the
southeast coast. Strong high pressure and subsidence developing
on the north side of the encroaching hurricane will result in
low humidities and seasonably cool conditions Saturday and
Sunday, with slightly warmer temperatures for the balance of the
period.
Will be keeping the entire period dry as it is not expected that
even if Irma tracks close enough to affect our weather, that it will
do so by mid-week. However, indications are that clouds will
probably be on the increase by Tuesday. Otherwise, expect bright
and sunny conditions, especially Sunday and Monday.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Area of rain and embedded thunderstorms will affect KPOU through
03Z/Wed, and may also expand into KPSF. Farther N and W, lighter
rain is expected to impact KALB and possibly KGFL between
01-04Z/Wed. Areas of MVFR/IFR could occur in the areas of
heaviest rainfall, with mainly VFR conditions elsewhere.
A brief break from the steadier rain may occur between 04Z-
06Z/Wed, however later tonight into Wednesday, areas of MVFR
Cigs/Vsbys are expected to develop as periods of rain overspread
the region. There will also be pockets of IFR, especially for
Cigs at KPSF.
Winds will be shifting into the NW to N at generally less than 8
KT overnight. On Wednesday, expect N to NE winds at 5-10 KT.
Outlook...
Wednesday Night: High Operational Impact. Likely SHRA.
Thursday: Moderate Operational Impact. Chance of SHRA.
Thursday Night: Isolated SHRA.
Friday: Moderate Operational Impact. Scattered SHRA.
Friday Night: Low Operational Impact. Slight Chance of SHRA.
Saturday: Moderate Operational Impact. Chance of SHRA.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: No Operational Impact. NO SIG WX.
&&
.FIRE WEATHER...
Periods of rain, along with unseasonably cool temperatures, are
expected through Thursday.
&&
.HYDROLOGY...
The weather will be wet and unsettled today into Thursday.
Showers and thunderstorms will occur ahead of the cold front
through tonight. Some locally heavy downpours and ponding of
water on roadways and poor drainage flooding in low lying areas
is possible through around midnight. Rainfall amounts may range
greatly from a few tenths to over an inch. Isolated flash
flooding is possible in any training thunderstorms repeatedly
moving over an area. If the potential becomes more widespread,
then a short-fused flash flood watch may be needed.
Additional rainfall is likely Wednesday through Thursday with
several weak waves of low pressure moving along the cold front
stalled just east of the Hydro Service area. Additional rainfall
amounts of a half an inch to two inches are possible bringing
total rainfall amounts from today to Wednesday night in the 1 to
2.5 inch range for areas from Albany and points south and east,
with the higher amounts possible over western New England. Some
within bank rises are expected on the main stem rivers, but the
potential for widespread flooding is not anticipated at this
time. The latest MMEFS guidance, particularly the SREFs,
suggests that the Hoosic River in Williamstown, MA could
approach or surpass action stage, especially if 2 inches or
more of rainfall occurs, so trends will need to be watched.
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...KL/Wasula
NEAR TERM...KL/OKeefe
SHORT TERM...KL
LONG TERM...ELH
AVIATION...KL/NAS
FIRE WEATHER...KL/Wasula
HYDROLOGY...KL/Wasula
Area Forecast Discussion
National Weather Service Binghamton NY
918 PM EDT Tue Sep 5 2017
.SYNOPSIS...
Showers and thunderstorms will continue today as a cold front
slowly moves across the region. Some of these storms may become
severe today with damaging winds and large hail as the main
threats. The chance for rain will prevail across the region
through Saturday along with cool temperatures.
&&
.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
Updated at 915 pm... Most of the showers have moved east of the
area as of the middle of this evening with just scattered
showers over northwest Pa trying to move northeast into Steuben
county. Latest high resolution guidance continues to show
another batch of showers expanding north to cover much of
central NY and northeast Pa after midnight tonight. Forecast
pop trends continue to show this idea, with low pops late this
evening gradually increasing to 40 to 50 percent across much of
the area overnight, with highest pops ove northeast Pa. Previous
discussion is below.
Updated at 645 pm... Active convection has shifted east of
northeast Pa with a broken line currently organized over NJ and
the lower Hudson valley. A large area of showers is located
behind the line over northeast Pa and this is moving steadily
east. Isolated light showers were located across western NY but
these are not expected to reach central NY for the next few
hours. Main uncertainty with the next 6 to 12 hours of the
forecast will be timing of the next wave of rain that is
expected to move northeast along the stalling front from Pa back
across central NY. Another question will be how far west this
area of rain can get. Our area will be on the cool side of the
front so we are expecting just some showers when this next wave
arrives late tonight or Wednesday morning. Current pop forecasts
are indicating increasing shower chances spreading north from Pa
to central NY after midnight and continuing through much of
Wednesday. The latest HRRR and NAM nest both show showers
expanding to the north to cover areas as far west as the eastern
Finger Lakes by 12z Wednesday and our current forecasts bring
chance pops that far west by 12z. Previous discussion is below.
240 PM EDT Update...
A slow moving cold front continues to slowly ease it`s way east
across portions of central NY and northeast PA this afternoon. Ahead
of the fropa this afternoon, SB CAPE have risen to 1000-1500 J/KG,
effective bulk shear is around the magnitude of 40-45 knots, low-lvl
lapse rates have risen to around 7 deg C/KM, however mid-lvl are
weak around 6. Deep moisture convergence is lacking over the
region, and the dynamic forcing is not expected to move into the
area till later this afternoon which is explaining to why
thunderstorm activity is on the weaker side attm. Thus, if
severe weather is to get going, expect it to get going after
19/20Z and primarily over NEPA.
With the front moving through slower max temps will still have a
steep gradient, with max temps over central NY ranging from mid
60s/low 70s and over NEPA ranging in the mid 70s/low 80s. Temps will
fall into the 50s overnight.
The front is expected to make it to the far SE portion of the CWA
tonight and stall over the region. Late tonight, expect a wave
embedded within the flow aloft to ride along the front and generate
additional showers and thunderstorms along this boundary. It looks
like the timing of this is now slower than previously thought
(near sunrise).
Wed additional showers will continue along this front and behind the
front as diurnal convective showers are expected to develop
across the area as height fall will prevail as the upper trough
is slow to move through. Temps Wed afternoon will rise into the
low/mid 60s and fall into the low 50s/upper 40s Wed night.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
2 PM update...
Cool and unsettled pattern persists this period as a deep upper
level trough over the Great Lakes moves slowly east. Thursday
morning more widespread showers continue with a weak surface
boundary and upper level short wave. By evening, showers will be
mostly in NY and isolated. Thursday overnight the showers reach
a minimum before the core of the trough moves in Friday with
scattered showers in all of central NY and northeast PA.
Rainfall amounts for this entire period will be less than half
an inch with the greatest amounts in the far north. Temperatures
will be cooler than normal with highs in the low and mid 60s
and lows 45 to 52.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
1230 PM update...
Better agreement now on the upper level trough at the beginning.
Improving weather as an upper level trough over NY/PA Friday
moves east on Saturday. Some lingering light showers and cooler
temperatures.
The rest of the forecast should be dry with a large area of high
pressure at the surface and high heights aloft. The airmass will
gradually warm.
Temperatures for the long term start out below normal with lows
in the 40s and highs in the 60s then warm to lows in the 50s
and highs in the 70s.
Finally, there continues to be much uncertainty regarding what
Irma will do next week. The 5 day NHC forecast brings Irma to
southern Florida Sunday morning. The models then turn the storm
to the north and increase the speed some. However at this point
if the storm has any impacts on the area this doesn`t look to
occur until at least Tuesday so it`s still a week or more away.
&&
.AVIATION /23Z TUESDAY THROUGH SUNDAY/...
Showers and thunderstorms will move across the region today as a
slow moving cold front moves from west to east. As the front
approaches, overall cigs will consist of fuel alternate through
00Z with embedded IFR cigs. Ahead of the fropa cigs will
continue to be VFR until -shra and TSRA arrive. Confidence is
low at which sites will receive TSRA, thus will leave out and
AMD when necessary. The TAF site that has the highest
probability to see a TSRA is KAVP (with hail and gusty winds and
a severe threat).
Behind the front expect a brief period of VFR then conditons
may become fuel alternate or IFR near sunrise, then become MVFR
Wed afternoon.
Winds will be light and variable through the forecast period
(except ahead of the fropa, southerly at 6 to 10 knots).
Outlook...
Wednesday - Friday...Restrictions possible from -SHRA.
Saturday - Sunday...VFR expected the majority of the time.
Early morning fog possible, especially at KELM.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.
&&
$$
SYNOPSIS...KAH
NEAR TERM...KAH/MSE
SHORT TERM...TAC
LONG TERM...TAC
AVIATION...KAH
Area Forecast Discussion
National Weather Service Denver/Boulder CO
904 PM MDT Tue Sep 5 2017
.UPDATE...
Issued at 904 PM MDT Tue Sep 5 2017
Temperature dropping quickly at DIA after sunset, but this should
slow as the drainage wind develops over the next few hours. Cool
forecast lows still look good. No changes needed.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 314 PM MDT Tue Sep 5 2017
GOES 16 imagery shows the upper level smoke plume resides over
the area, while low level airmass is cleaner (but still some
smoke) than we observed yesterday. The latest HRRR vertically
integrated smoke product shows the upper level plume shifting
slightly south/west as flow aloft turns more northerly tonight.
However, mountain areas will still be under the plume for the
majority of the night and possibly into Wednesday so will keep
some haze in the forecast for those locations.
Strong radiational cooling is expected tonight with light winds
and a dry airmass, so look for a bit of chill in the air. On
Wednesday, warm advection will kick in. 700 mb temps warm about
3-4C from today so look for highs to approach 80F on most of the
plains. No precipitation through Wednesday with a dry and stable
airmass in place.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 314 PM MDT Tue Sep 5 2017
Persistent upper level ridging over the western U.S. is going to
keep a warm airmass in place over Colorado through the forecast
period. Initially the airmass will be quite dry, but smoke from
forest fires over the Pacific Northwest may drift over the region
at times, due to the northwesterly flow aloft. By the end of the
week, the upper ridge will weaken slightly as mid-level moisture
is forecast to increase over the desert Southwest. By Thursday
night and Friday we will begin seeing an increase in shower
activity over the mountains. This pattern should continue through
the weekend. The temperatures will peak in the upper 80s across
the plains, which is getting to be about 10 degrees warmer than
normal. Strong storms are not expected at this point, as we wait
to see how much moisture is actually drawn over the state by the
weakening upper level ridge.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 904 PM MDT Tue Sep 5 2017
VFR through Wednesday. Main area of smoke is snow south of Denver,
with some remaining to the west, but there should be much less in
the Denver area Wednesday. No changes needed.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Gimmestad
SHORT TERM...Barjenbruch
LONG TERM...Dankers
AVIATION...Gimmestad
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
734 PM CDT Tue Sep 5 2017
.DISCUSSION...Increased pops across the west through 9 pm with
light rain persisting and slow to decrease in coverage. Kept rain
chances at 30 percent in the lower Valley and offshore overnight
but this could increase since there is plenty of tropical moisture
in place with tropical Depression sitting just 80 miles east of
Tampico, Mexico. Would expect a nocturnal increase in convection
overnight as has been the cast the last few night. HRRR is showing
showers increasing around sunrise with the RAP13 showing isolated
to scattered showers lingering all night along the coast and in
the Lower Valley. Temperatures look on track and cloud cover and
wind also look ok at this time. New zone forecast is out.
See earlier Marine discussion update on possible small craft
advisory issuance Wednesday.
&&
.PREV DISCUSSION... /issued 643 PM CDT Tue Sep 5 2017/
DISCUSSION...Updated for latest aviation discussion below.
AVIATION...The combination of the moisture of newly formed Tropical
Depression 13 (soon to be TS Katia), located 80 miles east of
Tampico, Mexico and the approach of a cold front Wednesday will
keep the chance of showers and isolated thunderstorms in the
vicinity of the Rio Grande Valley airports and most of Deep South
Texas the next 24 hours. Overall, VFR conditions will prevail
outside of the convection but brief IFR to MVFR cigs and lower
visibility restrictions are possible in and near the convection.
Would expected an increase in nocturnal convection over the Gulf
waters overnight moving inland after midnight or before sunrise
which might impact KBRO and possibly KHRL. Rain chances increase
for all areas during the day Wednesday as the cold front bears
down on the region in the afternoon. Winds will be light form the
northeast backing northwest Wednesday in wake of the late
afternoon front but could be slightly higher and remain northeast
along the lower coastal regions. Some gusts to 20 knots are
possible later Wednesday.
PREV DISCUSSION... /issued 454 PM CDT Tue Sep 5 2017/
DISCUSSION...Updated for latest marine discussion below.
MARINE...Tropical Depression 13 has formed about 80 miles east of
Tampico Mexico and is expected to become Tropical Storm Katia late
tonight or Wednesday. The depression is expected to remain nearly
stationary through Wednesday then begin a slow south to southwest
motion, away from the Lower Texas Coastal waters, as high
pressure builds into the northwest Gulf of Mexico behind a cold
front. With the current National Hurricane Center forecast keeping
the tropical cyclone well south of the coastal waters no direct
impact is expected however, the combination of the cyclone and
the high pressure building over the NW gulf will increase
northeast winds and allow for swells to build to small craft
advisory levels. This could occur as early as Wednesday afternoon
but more likely Wednesday night and continue through at least
Friday. Marine interest along the Lower Texas coast should check
the latest NWS forecast before venturing out from port the next
several days.
PREV DISCUSSION... /issued 240 PM CDT Tue Sep 5 2017/
SHORT TERM (Tonight through Wednesday Night):
Isolated to scattered convection will continue through the
evening especially across the Northern Gulf waters and Northern
Ranchlands. Meanwhile, an outflow boundary from convection earlier
this morning over the Gulf waters south of here has worked to
stabilize portion of Deep South Texas this afternoon given the
overall lack of activity over the Lower and Mid Valley areas. As
such, have cut back on POPs through the remainder of today and
this evening. However, have not generally made any significant
changes to the short term forecast. Moisture remains abundant as a
tropical waves sits over the southwestern Gulf. The NHC has this
system strengthening over the next few days, but it should remain
well south of the RGV given the combination of a cold front moving
south early Wednesday morning with a strong surface high pressure
system building in behind it. As of now, the only concerns with
this system will be continued chances for showers/storms and
increased swells. Temperatures will continue to be in the 90s for
highs, with lows by Wednesday night more noticeably cooler across
the northern areas.
LONG TERM (Thursday through Tuesday): Thursday will see a brief
break in the rainfall as drier air surges into Deep South Texas
behind the cold front. The front itself will stall just south of
the region, and meander through Friday. Moisture return from
easterly flow off the gulf will bring a return of rain chances for
the lower valley Friday into Friday through Saturday, while most
of the upper valley and ranchlands remain dry. The next surge of
drier air still expected Saturday evening will envelop the entire
region, ending rain chances and bringing near to just below normal
temperatures for the region, especially at night.
MARINE:
Now through Wednesday Night: Relatively benign marine conditions
will continue through this evening as winds remain light with high
pressure generally in control. By late this evening into the
overnight hours, a early season cold front will move through the
Lower Texas Coastal waters with northwesterly winds expected.
Strong high pressure will settle over north-central Texas by
Wednesday night and will interact with the low pressure system
across the southwestern Gulf. This will strengthen the surface
pressure gradient, with increasing moderate winds and seas
expected.
Thursday through Sunday: The next wind surge should arrive
Thursday morning, with northeast flow increasing to around 20
knots, pushing seas up to 5 to 7 feet offshore. The breezy and
agitated conditions will continue into Friday before the gradient
relaxes over the weekend. onshore flow will fall to 10 to 15 knots
Saturday, allowing seas to drop to 4 to 5 feet.
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
This product is also available on the web at:
HTTP://WEATHER.GOV/RGV
59...Short term
Area Forecast Discussion
National Weather Service Burlington VT
1024 PM EDT Tue Sep 5 2017
.SYNOPSIS...
Showers will taper off overnight from west to east...but
return again on Wednesday...especially across Vermont. Very slow
moving upper level trough will keep mention of showers for the
North country all the way through Friday night.
&&
.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
As of 1024 PM EDT Tuesday...Little change to the forecast with
this update. Cold front slowing to a crawl now near KVSF with
some scattered lingering showers still around in se VT.
Lots of clouds and moisture remain in place overnight as
precipitation comes to an end. Have patchy fog mentioned in the
forecast, and this will especially be expected in areas that had
plenty of rainfall today. Lows tonight mainly in the 50s.
Model solutions vary as to additional shower development toward
morning as a baroclinic wave develops on the front with the
HRRR and now the 00Z NAM most aggressive redeveloping light
rain/showers by 12z as the upper level trough approaches our
forecast area Wednesday and Wednesday night.
The region will remain under it`s influence through much of the
week. Departing cold front will also remain draped just to our
East and will remain focus for shower activity. Looks like a
cool wet unsettled period.
&&
.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
As of 330 PM EDT Tuesday...Cold front looks to be shifted to
east of the CWA Thursday morning. Though, the upper trough over
the Great Lakes will still send waves of energy into the area
throughout the day, enhancing the chance of scattered showers
throughout the daylight hours. Right now, the QPF doesn`t look
to be very significant, only 0.10" or less for the southern
counties to 0.25" across the northern counties. Thursday highs
will be in the upper 60s with overnight lows in the upper 40s to
lower 50s.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 345 PM EDT Tuesday...The upper trough remains over the
region Friday, to start the long term. Showers continue to
remain diurnally driven, with isolated showers mainly during the
late morning to afternoon hours. As the previous shift has
noted, the cold nature of the upper trough with 500mb temps
falling below -20C and modeled soundings showing some weak
elevated instability even support the possibility of some
graupel on Friday as well. Things become drier and much quieter
over the weekend as the trough shift east and is replaced by
upper level ridging and surface high pressure. Temperatures look
to warm into next week back towards seasonal normals.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Through 00Z Thursday...A wide variety of flight categories
expected overnight with IFR at KMPV. Scattered showers will be
coming to end, mainly over the south, but over the area with
MVFR/VFR ceilings continue through 03z. With all the rain today
leaving a moist boundary layer behind with dew point
depressions already only a couple degrees and light boundary
layer winds will have some IFR ceilings and possible LIFR
visibilities after about 05z. Mesoscale models show another
wave of showers move across our forecast area after about 12z,
and have mentioned VCSH at this time due to uncertainty with
where these showers will develop. Expect more showers across the
area tomorrow, especially our Vermont terminals.
Outlook...
Wednesday Night: VFR. Likely SHRA.
Thursday: VFR/MVFR. Likely SHRA...Slight Chance TSRA.
Thursday Night: VFR. Slight Chance SHRA.
Friday: VFR. Chance SHRA.
Friday Night: VFR. Chance SHRA.
Saturday: VFR. Slight Chance SHRA.
Saturday Night: VFR. Slight Chance SHRA.
Sunday: VFR. NO SIG WX.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Neiles
NEAR TERM...Neiles/Sisson
SHORT TERM...Verasamy
LONG TERM...Verasamy
AVIATION...Neiles/Sisson
Area Forecast Discussion
National Weather Service Buffalo NY
1037 PM EDT Tue Sep 5 2017
.SYNOPSIS...
An upper level low will bring several rounds of showers across the
region through Friday night...with air temperatures averaging just
below normal. It will then become dry for the weekend and heading
into the start of next week...with temperatures moderating back to
normal...and above normal on Monday.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
An upper level trough will remain across the Upper Great Lakes
overnight which will maintain a cyclonic flow across our
region. Instability showers across land have largely ended by
late evening, with scattered showers starting to develop along
the land breeze convergence on Lake Erie. This will result in a
brief period of showers in the Buffalo metro area, but should
largely shift to the open waters as low level winds diminish
further overnight.
High clouds will gradually slide to the east, along with
diminishing cumulus will result in partly to mostly clear skies
tonight. Any clearing will result in radiational cooling and
fog, with the best chance for fog across the Western Southern
Tier and Eastern Lake Ontario region. Lows will range from the
upper 40s to lower 50s.
Tomorrow, under cold air advection we should see the sky again
become mostly to completely cloudy by late morning. As we warm
in the lower levels...we`ll increase the lapse rates such that
scattered showers will be likely by afternoon across the region.
Highs tomorrow will generally remain in the 60s.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
An upper level low will slowly move east across Central Ontario and
Quebec during the 2nd half of the week. This will result in cool
weather with scattered showers, locally enhanced downwind of Lake
Erie and Lake Ontario (on a W or WSW flow).
The best chances for deeper (lake initiated) convection will be late
Thursday and Friday with the coolest air aloft. The vertical depth
of instability will be enough for a few thunderstorms. From a
marine point of view, there will be a chance for waterspouts as
well.
Flow aloft becomes NW and starts to dry out Friday Night with a
large surface ridge beginning to build into the region.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
A trough will move off the New England coast on Saturday while a
sprawling Canadian high pressure will build across the Great Lakes
Sunday and Monday before finally weakening and shifting off New
England coast Tuesday. This will result in below normal temperatures
through the weekend, with cool crisp fall-like mornings. The coolest
850 mb temperatures will move across the region Saturday in the wake
of the departing upper-level trough, down to around +2/+4C. This
will bring highs in the low to mid 60s Saturday. Airmass
modification, combined with the coldest portion of the airmass
moving east of the area will bring a daily warming trend Sunday
through the beginning of next week. High temperatures will return to
the 70s by Monday and Tuesday. Mornings will remain cool with high
pressure, little cloud cover and light winds promoting radiational
cooling. Lows will be in the mid 40s in the lake plains down to the
mid to upper 30s in interior valleys, where some patchy frost is
possible.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Expect mainly VFR conditions into the early morning hours with
widely scattered showers. Patchy fog will develop late tonight,
with the best chance for vsby restrictions at JHW where several
hours of IFR conditions are likely late tonight and into
Wednesday morning. Based on a narrow temp/dew point spread and
latest HRRR guidance have added fog to the ART TAF as well.
Conditons will improve by late Wednesday morning, with mainly
VFR conditions Wednesday afternoon. There is a small chance of
showers, but coverage will be sparse with a minimal and/or brief
impact on aviation flight conditions.
Outlook...
Wednesday night through Friday...VFR/MVFR. A chance of showers.
Saturday and Sunday...Mainly VFR.
&&
.MARINE...
An upper level low will slowly pass across the Great Lakes region. A
weak pressure gradient over the lakes will maintain light to
moderate winds...even though we`ll be under CAA through the end of
the work week. Westerly to southwesterly winds will increase
some Thursday...with waves building to around 3 feet on the
eastern shoreline...before the upper level trough axis
passes...and waves return to 2 feet or less.
There will be a risk of waterspouts with rising equilibrium
levels and lake induced instability.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.
&&
$$
SYNOPSIS...THOMAS
NEAR TERM...APFFEL/THOMAS
SHORT TERM...ZAFF
LONG TERM...CHURCH
AVIATION...APFFEL
MARINE...APFFEL/THOMAS
Area Forecast Discussion
National Weather Service Columbia SC
723 PM EDT Tue Sep 5 2017
.SYNOPSIS...
Moisture will continue to increase across the forecast area
tonight as a frontal boundary moves into the Upstate. The front
will move through late Wednesday, increasing the chance of
showers and thunderstorms, ushering in cooler and drier air into
our FA Thursday into Saturday. Hurricane Irma will continue to
be monitored for possible significant impacts to this area early
next week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Convection this evening remains confined to the eastern Midlands
where moisture is deeper and instability is higher. Models
suggest diminishing convection in the eastern Midlands this
evening with loss of heating and additional development in the
west associated with a shortwave ahead of the front. Current
radar imagery shows a line of convection along the Appalachians
with trailing rainfall in its wake. Models show this line
weakening as it progresses eastward, but still bring some
activity into the area. Continued with mainly chance/slight
chance pops overnight. Mild overnight lows in the low 70s given
expected cloudiness and mixing.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
A cold front is expected to move through the area Wednesday.
Moisture will pool along and ahead of the front, while upper
divergence in the right rear portion of the upper jet will
provide enhanced vertical motions, supporting a considerable
amount of convection. Low level winds are not particularly
impressive, but a pretty robust mid level jet for this time of
year should allow for some convective organization during the
afternoon and evening hours moving through the area from
northwest to southeast, so the marginal severe risk currently
painted by SPC across the area looks prudent. Instability will
be lower, especially in the northwestern portion of the CWA
where the front will pass through earlier in the day, keeping
the severe threat from becoming too significant.
The front will be moving to the east of the area and into the
Atlantic Wednesday night, so POPs will diminish accordingly.
Cooler, drier air will be moving in quickly behind the front,
with min temps running as much as 15 degrees cooler than Tuesday
night.
On Thursday and Thursday night, surface high pressure with
a modified polar air mass will dominate the southeastern states.
Max temps will range from the upper 70s north to the lower 80s
south, with dew points down into the upper 40s to lower 50s.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
High pressure at the surface will remain in control through
Saturday with only a very modest warming trend. Winds will pick
up a little by Saturday afternoon as a stronger high moves into
the Great Lakes and increases the pressure gradient across the
area between it and Hurricane Irma.
For Sunday into early next week, it`s all about Irma. The
eventual path and intensity are still uncertain, so don`t put
too much weight on any one specific forecast. Conditions will
deteriorate with time as wind and chances of rain increase.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Expect mainly VFR conditions during the TAF period but
thunderstorms may occur.
Convergence associated with a pre-frontal trough may support
thunderstorms tonight. Coverage should be limited by the loss of
heating. The HRRR suggested the band of thunderstorms
approaching from the west would diminish. The thunderstorm
chance was too low to include in the terminal forecasts at this
time. Mixing ahead of the front and shallow moisture should
limit low stratus and fog overnight and most of the NAM and GFS
MOS maintain VFR conditions. Convergence along the front should
help cause thunderstorms during the day Wednesday but cloudiness
may limit instability and coverage. We did not include
thunderstorms at this time because of timing uncertainty.
EXTENDED AVIATION OUTLOOK...No significant impacts are expected
through Saturday. It may become breezy Sunday associated with
the pressure gradient between high pressure centered in the
Great Lakes Region and Irma south of the area.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
SYNOPSIS...99
NEAR TERM...99
SHORT TERM...99
LONG TERM...99
AVIATION...99
Area Forecast Discussion
National Weather Service Charleston SC
1022 PM EDT Tue Sep 5 2017
.SYNOPSIS...
High pressure offshore tonight will give way to a cold front
that moves through Wednesday night. High pressure will then
prevail through late week. Powerful Hurricane Irma will likely
be near Florida and the Bahamas this weekend. Refer to the
latest advisory on Irma issued by the National Hurricane
Center.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 1020 PM: Showers and embedded thunderstorms were located
across the foothills and western Piedmont of SC and GA. Storm
motions were generally toward the ENE. Latest HRRR suggests that
the convection will approach the Midlands late tonight, then
generally dissipate. A few cells may reach the inland portion of
the forecast area during the overnight to pre dawn period.
Otherwise, convection is expected to develop over the coastal
waters late tonight, with some activity tracking onshore around
dawn. I will indicate PoPs slowly rising late tonight,
especially across the marine zones. Otherwise, steady SW winds
will continue through the night, remaining gusty over the marine
areas.
As of 735 PM: Convection has dissipated further since the last
forecast update. I will update the forecast to adjust PoP and
sky trends. Overall, the current forecast appears in good shape.
As of 635 PM: Scattered showers and thunderstorms continued to
develop along and ahead of a sea breeze pushing inland. The
environment ahead of the sea breeze remains unstable and should
support convection through mid evening. High resolution guidance
suggests that convection will decrease after sunset. Coverage
may increase toward sunrise as marine convection slides over the
coastal area. In addition, isolated to scattered remnant storms
from the southern Appalachians may reach the forecast area by
sunrise Wed.
Previous Discussion:
Through this evening: Isolated to scattered
convection will continue, mainly inland, before coverage
dwindles with sunset. Instability and lapse rates are
unimpressive, and the depth to most activity will remain
limited. But given DCAPE up near 1000 J/kg, a few sub-severe
wind gusts can still occur in isolated storms. We have also
altered the diurnal temp curve somewhat to account for the best
coverage of convection from inland Berkeley County to inland
Colleton County.
Tonight: The large scale pattern will undergo further
amplification as a large and deep trough encompasses the bulk of
the central and eastern U.S., while a strong ridge is in the
west. Vigorous short wave energy diving SE through the trough
the OH valley to the mid MS valley will send a cold front ever
so slowly SE from the Appalachians. The front though is still
off to the NW of the local vicinity by morning. Warm advection
in advance of the front will transpire as a deep SW flow occurs,
allowing for sufficient instability and moisture transport.
Although the mean steering flow should keep the majority of
convection offshore, isentropic ascent and upper difluence due
to the southern branch of the sub-tropical jet, we will maintain
slight chance/chance PoP, with highest coverage over the
coastal corridor after midnight. Given 25 or 30 kt of 0-6km
Bulk Shear there can be a few clusters of storms that develop,
and with elevated moisture content some hard downpours are
possible. But the progressive nature of convection should limit
any significant flooding concerns.
The warm advection, plus various layers of 40-70% clouds cover
will hold temps to no lower than the lower and middle 70s.
Shoreline communities of SC will be breezy through mid or late
evening, with S-SW winds as high as 15 or 20 mph and gusty.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
Wednesday: Aloft, a large mid/upper trough of low pressure will
continue to dig over the Great Lakes region, expanding south and
southeast over much of the Eastern Conus by the evening. The trough
will help push a cold front across the Midlands early, then over
much of Southeast South Carolina and Southeast Georgia during late
evening into early overnight hours. A persistent southwest flow
ahead of the front will help advect deep-layered moisture into the
region, characterized by PWATs between 1.5 to 2.0 inches. The setup
should support chances of showers/thunderstorms over most areas by
late morning, followed by numerous showers/thunderstorms during
afternoon into early overnight hours along/near the advancing cold
front. Upper lvl divergence associated with a passing h25 aloft
along with modest shear should help convection thrive upstream
initially, before the sfc cold front helps shift activity into the
area late. Given the timing of the front, increasing cloud cover and
marginal instability overnight, the overall threat of severe weather
is somewhat low. However, a few stronger thunderstorms are not of
the question, particularly over the Tri-County area where the
combination of forcing and instability are most favorable for
stronger updrafts. High temps will peak in the mid 80s, warmest in
Southeast Georgia. Overnight lows will range in the low 60s inland
to upper 60s closer to the coast.
Thursday and Friday: Most moisture lingering over the area will
quickly shift offshore with a cold front by daybreak Thursday. Sfc
high pressure will then build across the region Thursday into Friday
while a large mid/upper lvl trough of low pressure quickly lifts to
the northeast with an south/southwest axis that begins to shift
offshore late Friday. The setup will favor dry and slightly cooler
conditions while cold air advection occurs post fropa. In general,
temps will peak in the lower 80s Thursday, then slowly modify into
the low/mid 80s Friday. Overnight lows will range in upper 50s
inland to low/mid 60s closer to the coast.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
The trough to our north will continue moving eastward and offshore
as surface high pressure prevails into the first part of the
weekend. Focus then turns to powerful Hurricane Irma, which will
likely be near the Bahamas and southern Florida this weekend. There
remains an elevated risk for impacts from Hurricane Irma over the
weekend into early next week. However, it is still too early to pin
down exactly how Irma will impact the region as there remains
uncertainty with the track Irma will take and how strong it will be
as it approaches the Southeast United States.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Steady SSW winds and VFR conditions should remain across the
terminals tonight. KSAV may see some pre dawn ground fog in the
vicinity, but no restrictions are expected at this time. A cold
front is forecast to remain west of the terminals through the 0Z
TAF package. SW winds should increase through the daylight
hours, with gusts around 20 kts during the afternoon into the
early evening. A band of showers and thunderstorms should
develop ahead of the cold front Wednesday afternoon. I will
highlight the thunderstorm potential with a PROB30 from 17Z
through 23Z.
Extended Aviation Outlook: Flight restrictions are possible
Wednesday night due to showers/thunderstorms along or near a
passing cold front. VFR conditions are then expected Thursday
into Saturday.
&&
.MARINE...
Tonight: Winds will remain elevated within a decent gradient
between high pressure to the SE and a cold front to the NW. Once
sea breeze circulations dwindle this evening, mixing of 20 or 25
kt of geostrophic winds will occur through the night. This keeps
winds as high as 15 or 20 kt, with some higher gusts as winds
veer from S to SW. Seas will start around 2 or 3 ft, but will
quickly build another 1-2 ft through the next 12-15 hours.
Conditions overall should stay just below any SCA thresholds.
While we haven`t seen much of the initial long period swell from
very distant Hurricane Irma, the NWPS guidance suggests that
some 14-16 second period swell could still yet arrive tonight.
Even so, height of these swells would be no more than 1 or 2 ft.
Mariners are also advised of widely scattered to scattered
convection developing, with the greatest coverage out near the
western wall off the Gulf Stream, and mainly during the late
evening or post-midnight hours. A few storms will produce
frequent lightning, gusty winds and very heavy rains.
Wednesday through Sunday: A cold front will approach from the
northwest late Wednesday, passing through the area and to the
southeast by early Thursday. Dry high pressure will then build
over the waters from the north/northwest and persist into late
week. There will likely be stronger winds late in the week due
to an enhanced pressure difference between continental high
pressure to the northwest and Hurricane Irma far to the south-
southeast. It`s still too early to determine what type of marine
headlines we`ll need as the weekend begins, but mariners should
expect at least Small Craft Advisory level winds/seas that
deteriorate this weekend. Additionally, long period swell from
distant Hurricane Irma will continue to impact the waters, with
an average period of 13-17 seconds.
Rip Currents: Distant swell associated with Hurricane Irma should
slowly increase this week as Irma tracks west-northwest. Although
swell height over the coastal waters will initially be small, on the
order of 2 ft, waves will be quite powerful with most of it likely
reaching the surf zone. This will be enough to support a moderate
risk for rip currents at area beaches this evening through much of
Wednesday.
Long period swells will continue to impact the surf zone into the
upcoming weekend and possibly into early next week depending on the
track Irma takes. This will result in an enhanced risk for powerful
and dangerous rip currents.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...NED
SHORT TERM...
LONG TERM...
AVIATION...NED
MARINE...
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1018 PM CDT Tue Sep 5 2017
.UPDATE...
Quick update to retrend hourly grids after the precipitation along
the Rio Grande Plains earlier this evening and the ongoing showers
and storms across the Hill Country out ahead of the front. The front
is currently situated from Langtry/Juno to Llano to Temple. It will
continue to push slowly south and east through the overnight hours.
No change to the ongoing forecast with isolated showers and
thunderstorms expected to continue ahead of the front as it moves
through South Central Texas. Drier air is filtering in behind the
front with dew points in the DFW area in the low to mid 50s, as
opposed to the upper 60s ahead of the front in Central Texas.
&&
.PREV DISCUSSION... /ISSUED 657 PM CDT Tue Sep 5 2017/
AVIATION...
Pre-frontal trough this evening is producing strong TSRAs near DRT.
Wind gusts in excess of 40kts have been reported. The storms should
move off to the south into Mexico between 01Z-02Z. Actual cold front
will move through the region from N to S between 03Z-09Z, reaching
AUS roughly around 05Z and SAT to DRT roughly around 07Z. A few
SHRAs will be possible along the front near AUS and possibly SAT.
In addition, a broken 3-4k foot cloud deck is indicated by NAM12 and
HRRR soundings behind the front. Winds from the north are forecast
to become gusty along the I-35 corridor after 15Z, with gusts 20-25
kts possible.
PREV DISCUSSION... /ISSUED 502 PM CDT Tue Sep 5 2017/
UPDATE...
Isolated showers and thunderstorms have formed ahead of the cold
front. Additional showers and storms have developed along a pre-
frontal trough in Kinney and Uvalde counties. Have expanded slight
chance and chance PoPs through the evening hours due to this
increase in activity. Lightning and some quick gusts to 40mph are
possible with these storms. Rainfall amounts will generally be a few
hundredths of an inch to a tenth of an inch. The strongest storms
could produce up to a quarter of an inch of rainfall.
The front is currently through Sonora, Junction, Burnet, and Belton
and is continuing to push southward. Once the front moves through an
area winds will shift out of the north and chances for rain will
end.
The rest of the forecast is on track with slight chance and chances
for showers and thunderstorms continuing into the overnight as the
front progresses southward across South Central Texas.
PREV DISCUSSION... /ISSUED 247 PM CDT Tue Sep 5 2017/
SHORT TERM (Tonight through Wednesday Night)...
Partly to mostly cloudy skies are in place across the region with
temperatures in the lower 90s. The cold front associated with a large
trough east of the plains is located to our north but a pre-frontal
wind shift is already knocking on the door of the northern Hill
Country. Could see some isolated shower or storm activity in this
area later this afternoon and evening. Additional chances for showers
and storms will be possible overnight as the main cold front moves
through the area. Overall, chances of precip will remain low due to
lack of forcing as the main trough remains well to the east. Average
rainfall accumulations for locations that actually pick up rainfall
will remain around 1/4 of an inch.
Rainfall chances will end from north to south by the mid-morning
hours tomorrow. Highs tomorrow behind the front will top out in the
upper 80s to middle 90s in the southwest who should not see much of
the effects of the front by the afternoon hours. Lows Wednesday night
will bottom our in the 50s and 60s giving us our first taste of
Fall. Dewpoints in the 40s and 50s will allow for this cooler night
time temperatures.
LONG TERM (Thursday through Tuesday)...
The long-term forecast will remain dry without any appreciable
forcing mechanisms. Surface winds will remain light behind the front
for several days which will equate to a slow warm up with low
temperatures through Monday in the upper 50s to 60s. We will be
between two systems by the end of the forecast period with high
pressure to our west and Irma well to our east. This will keep light
northeasterly winds at the surface through Tuesday. Highs in the
long-term will remain in the upper 80s to the lower 90s across the
area.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 94 69 88 61 88 / 20 30 10 0 0
Austin Bergstrom Intl Airport 94 69 87 60 87 / 20 30 10 0 0
New Braunfels Muni Airport 93 69 89 59 90 / 10 20 10 0 0
Burnet Muni Airport 94 65 86 59 86 / 30 30 10 0 0
Del Rio Intl Airport 98 71 95 65 96 / 20 20 10 0 0
Georgetown Muni Airport 94 66 86 59 87 / 20 30 10 0 0
Hondo Muni Airport 96 69 94 60 93 / 10 20 10 0 0
San Marcos Muni Airport 93 69 88 59 88 / 10 20 10 0 0
La Grange - Fayette Regional 92 70 87 59 87 / 20 30 10 0 0
San Antonio Intl Airport 91 70 90 61 90 / 10 20 10 0 0
Stinson Muni Airport 93 71 90 62 90 / 10 20 10 0 0
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale/Aviation...Runyen
Synoptic/Grids...Treadway
Public Service/Data Collection...30
Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
836 PM MDT Tue Sep 5 2017
.UPDATE...
Issued at 836 PM MDT Tue Sep 5 2017
The 18Z HRRR Vertically Integrated Smoke model shows the current
smoke from wildfires over the Pacific Northwest to remain over
much of eastern Utah and western Colorado through Wednesday night
as high pressure rebuilds over the west and keeps smoke trapped
with no features to help move it out. Based on the overall upper
level pattern, not much change exists until late Thursday
afternoon/evening when the ridge of high pressure will shift
slightly eastward and change the flow from a northerly direction
to a southerly direction, helping to draw a little more moisture
into the region. This change to a southerly flow will also
hopefully help to push the smoke out of the region but no
guarantees. However, felt confident enough to keep smoke in the
forecast through Thursday morning with haze Thursday afternoon.
&&
.SHORT TERM...(Tonight through Wednesday night)
Issued at 251 PM MDT Tue Sep 5 2017
Light northwesterly flow continues over the western slope this
Tuesday afternoon. High pressure is centered to the west of the
forecast area, and will be the primary weather story in the short
term forecast. Flow around this high pressure has directed smoke
from numerous wildfires in the Pacific Northwest south and
eastward, affecting portions of northeast Utah and western
Colorado. Several reporting sites have reported either smoke or
haze in their observations today, including Rifle, Eagle, and in the
Steamboat area. Convection has been limited to the San Juan
mountains as well as southeastern Utah. Most CAM guidance suggests
that any already limited shower or storm activity will quickly
diminish around sunset.
Wednesday will turn out very similar to Tuesday as high pressure
remains just west of the area. Forecast guidance suggests another
hazy morning as a result of smoke from wildfires in the northwest.
Another round of afternoon showers and perhaps some thunder in the
San Juans, however coverage will be limited to the highest
terrain.
.LONG TERM...(Thursday through Tuesday)
Issued at 251 PM MDT Tue Sep 5 2017
The overall weather pattern across the western CONUS for the end
of the week will focus around a longwave trough in the west, which
will cut off and dive southward through the weekend. The ridge of
high pressure in place over the central Rockies will break down
and shift slowly eastward. The net result for eastern Utah and
western Colorado will be an increase in moisture and thunderstorm
chances. Southerly flow to the east of the cutoff low and west of
the high pressure will act to draw the monsoonal plume northward.
While no significant frontal systems will pass through the
Rockies, this plume of moisture will result in an increase in
precipitation chances each day, peaking on Saturday afternoon. As
is always the case, the higher terrain will be favored for initial
convective development, however valley locations may also see
showers moving out of the mountains on Friday and Saturday. By
Sunday, medium- range global models indicate the cutoff upper-
level low drifting slightly westward away from the California
coast. PoP chances begin to decrease on Sunday and especially on
Monday and Tuesday of next week as high pressure builds back in
from the east. Confidence is high in the end of week forecast, but
drops by early next week due to differences in deterministic and
ensemble guidance.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 540 PM MDT Tue Sep 5 2017
Smoke will continue to be trapped under the ridge of high pressure
through at least Wednesday, potentially longer, which may reduce
visibility to MVFR levels at KVEL, KRIL, KEGE and KASE with hazy
conditions elsewhere. Some showers and storms down south will
diminish after sunset and gusty outflow winds to 40 mph remain the
primary threat. Another round of scattered convection will
redevelop after 15Z Wednesday with the San Juans favored for
activity.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
UPDATE...MDA
SHORT TERM...MAC
LONG TERM...MAC
AVIATION...TGJT
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
957 PM EDT Tue Sep 5 2017
.SYNOPSIS...
A cold front will approach from the northwest tonight and bring
widespread showers and thunderstorms to the area through Wednesday.
Dry, cool high pressure will spread back over the region in the wake
of the front on Thursday and linger into the weekend. Moisture will
increase again early next week.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 10:00 PM EDT Tuesday: Based on latest radar data, CAMS data,
and short range model guide we continue to raise the POPS across our
southern forecast area (FA) at mid evening. QPF values were adjusted
upward as well. A messy prefrontal surface axis, and lingering
instability and jet support continue to fire off convection. After a
review of the latest HRRR we might be starting to see the beginning
of new convection in northeast GA and the southwest part of NC. As a
result we have tempered the overnight break earlier expected, with
the idea that, although the atmosphere has been worked over, MUCAPE
was still in play. Additionally, a strong upper trough remains
poised just to our west. Temperature adjustments were only minor.
On Wednesday, the front should push thru the Piedmont during the
morning hours with ongoing showers crossing the area. By early AFTN,
guidance is in decent agreement that the front should be exiting
east of the area, with the better instability to our east. So the
severe threat looks to be east as well. Blending the CONSSHORT PoPs,
I have the hourly PoP trends actually decrease during the AFTN.
Temps will start out somewhat mild, but only rise about 10-15
degrees (resulting in below normal highs) as cool air filters in
behind the front.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 145 PM EDT Tuesday: After we eliminate lingering shower
activity over the eastern zones on Wednesday evening, we enter the
great lull for the rest of the week, until our anxiety starts to
build through the weekend as to the eventual fate of Irma over the
southeastern United States. The western Carolinas will spend most
of that time under a deep upper long wave trof that deamplifies
Thursday and Friday, but generally supports weak surface high
pressure with an air mass featuring temps around ten degrees below
normal. It should feel like early autumn owing to the dry air
mass. The main upper trof pulls out Friday night and Saturday while
pushing a weak front down from the north. Present indication is that
this boundary will be dry as it drifts into the area from the north
on Saturday. Slow modification of the air mass will allow temps
to creep upward through the weekend. It is at this point that the
forecast of features across the central and southeastern U.S. become
critical to the eventual path of Irma. Both the operational GFS
and ECMWF leave behind a piece of the old upper trof in the form
of a weak cutoff low Saturday night over MS/AL/GA, and it is this
contribution to upper troffing over the central US that erodes
the western portion of the upper ridge that has been keeping Irma
on its generally westward forecast track. Interaction with this
upper feature could turn Irma toward the north. At this point, it
appears that after any turn to the north, the storm would probably
remain far enough away to keep the outer edge of the circulation
from bringing any precip into the fcst area before sunset on Sunday.
&&
.LONG TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 230 PM EDT Tuesday: The abbreviated medium range forecast
picks up at 00Z Monday and focuses almost exclusively on potential
impacts from Irma. The TC location reflected in our grids reflects
the points that have been collaborated by the National Hurricane
Center and the Weather Prediction Center. The current track and
thinking do bring Irma`s track very close to our CWA through day 7,
so the forecast reflects some possible impacts. Sky cover increases
Sunday night, and pops increase from southeast to northwest Monday
morning, with much of the area likely seeing rainfall by Monday
night. Tropical rainfall would likely continue through much of
Tuesday as well. It is too early to accurately assess potential
rainfall totals...and there are some factors in our favor versus
not. The storm motion is fast, which could limit the time our area
sees the tropical rainfall. On the other hand...this is a tropical
system, which have historically been able to be quite prolific rain
producers in this area, even as tropical depressions and remnant
lows. The potential for heavy rainfall is there, and we`ll have to
sort out specific totals in the coming days. Current forecasts do
not portray wind as a significant issue, and the winds in the
current forecast are well below tropical storm force. From past
storms, however, we know that saturated soils mean that strong winds
are not necessary to topple a few trees. Tropical cyclone tornadoes
are a potential threat with any tropical system that makes landfall,
but the likelihood of those is too tied to small track details to
make an accurate assessment for our area at this time.
This is going to sound like a broken record, but please stay aware
of the forecast and realize that this is absolutely not set in stone
yet. Any impacts that could be realized would be at least 6 days out
at this point, and there is plenty of time for things to change and
for specific thinking on rainfall totals and tropical threats to be
refined. The track is still incredibly uncertain, and based upon the
intensity and motion of many synoptic features, including the
Bermuda high over the Atlantic Ocean and a couple of upper troughs
that move through the northern/eastern CONUS. The placement of an
upper low over the southeast next weekend continues to be vital to
the track of Irma...as unpredictable Fujiwhara interaction with that
feature will likely determine details of the final track.
Our best advice at this point is to have a plan and an emergency
preparedness kit in case of storm impacts, stay aware of the
forecast, and only turn to trusted sources of guidance.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and Elsewhere: Convection along and ahead of an approaching
cold front continues to move and expand in coverage, per latest CAM
guide. Therefore we have reconstructed the ceilings and vsbys ahead
of the convection for a round through about midnight. This fits the
locations with the best instability yet to be tapped. Points north
may have a lull or some light rain.
The cold front won`t cross the area until late tonight thru midday
Wednesday. There is expected to be a lull in convection overnight,
then another band of mainly showers, but perhaps with embedded TS
along the actual front Wednesday morning. So VCSH or prevailing SHRA
will be carried for the second round. The combination of evening
precip and ongoing SWLY moist flow overnight may support some
stratus development. Guidance generally shows MVFR cigs, especially
across the Piedmont Wednesday morning. Winds will be out of the SW
with some low-end gusts the rest of the AFTN, then become light this
evening. The winds will then switch out of the NW with the front
during the pre-dawn hours at KAVL, and right around daybreak or just
after across the Piedmont, but should remain light.
Outlook: A cold front will exit to the east late Wednesday. In the
wake of the front, dry high pressure will return on Thursday
resulting in generally VFR conditions through Saturday.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 97% High 91% High 82% High 89%
KGSP High 96% High 83% High 87% High 100%
KAVL Med 77% Med 62% Med 63% High 100%
KHKY High 93% High 92% High 80% High 98%
KGMU High 97% High 80% High 88% High 100%
KAND High 85% High 80% High 87% High 98%
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...Carroll
NEAR TERM...ARK/TS
SHORT TERM...PM
LONG TERM...Carroll
AVIATION...ARK/TS
Area Forecast Discussion
National Weather Service Pocatello ID
147 PM MDT Tue Sep 5 2017
.DISCUSSION...A ridge of high pressure was positioned across the
west early this afternoon as a deep low pressure trough shifted
slowly east through the Gulf of Alaska and a sub-tropical low lifted
north off the California coast. Also evident in visible imagery was
an abundance of smoke across SRN Idaho. Numerical models maintain
the ridge of high pressure across the region through Wednesday
allowing the ridge to break down under the weight of the advancing
Gulf trough and incoming sub-tropical disturbance (at least a
portion of each) Thursday and Friday. With the break down of the
upper ridge, we should expect to see at least isolated mainly
afternoon thunderstorm activity across the region Thursday and
Friday. A fairly well defined disturbance ejects from the Gulf
trough Saturday racing east along the Canadian border which may
result in ongoing isolated convection Saturday afternoon along with
locally breezy conditions (at least temporarily) which may help
alleviate some of the smoke. By Sunday the ridge begins to rebound
across the region albeit a bit weaker with dry conditions continuing
into mid-week. Daytime temperatures will remain well above normal
through the end of the week before cooling some with the passage of
the Canadian disturbance Saturday. Even with the cooling, temps
remain well above normal for this time of year. Huston
&&
.AVIATION...Winds expected to remain below 12 kts through tonight,
and we will be hard pressed to find a cloud anywhere. Big aviation
challenge continues to be smoke that has blanketed Idaho. The usual
suite of models do not really pick up on/forecast smoke, but there
are a few tools at our disposal. The HRRR smoke model is showing a
general trend of the smoke blanket slowly thinning/retreating SW
across NE ID, possibly offering very gradual improvement for
KIDA/KDIJ. Vis satellite confirms this trend, and this makes sense
on a generally NE flow. Across our remaining terminals, the HRRR
offers no clear trend toward improvement or deterioration through
Wed AM, and obs have been pretty stagnant today. So, I blended
trends in both the HRRR and surface obs for vsbys in the TAFs. This
yields a reasonable, moderate confidence forecast, although a few
adjustments are possible as we monitor. Expecting ocnl IFR
conditions to 2SM to continue at KSUN with perhaps some gradual
improvement to MVFR. VFR to MVFR conditions expected elsewhere at 4-
7SM.
Wed will again be mostly clear/dry with light winds, but with a
stagnant air mass in place, smoke will remain. Continued FU through
the end of the TAF period at all terminals, with perhaps slightly
improved vsbys Wed. - KSmith/Hinsberger
&&
.FIRE WEATHER...Hot and very dry conditions are expected through
tomorrow while smoke continues to reduce visibility. Smoke is
particularly dense in the Central Mountains with visibility in
Challis as low as 1 3/4 miles. Haines indices of 6 are expected
across the Central Mountains and South Central Highlands today and
tomorrow afternoon. Ridging will stay in place through the period,
keeping convection at bay. However, we will see the ridge shift
eastward Thursday afternoon, allowing some moisture to drift in from
the south. Thunderstorm activity should stay to the west on
Thursday, but we could see some isolated thunderstorms Friday
afternoon. Hinsberger
&&
.AIR STAGNATION...Very little movement in our atmosphere, which
will not aid in moving the smoke out anytime soon. Smoke really
increased yesterday as the flow turned out of the north and smoke
from Montana, northern Idaho and Canada pushed in. Air quality is
really decreasing, especially across the Big and Little Wood
River and Pashimeroi Valleys. Those with respiratory sensitivities
should limit exposure to these particulants. A fairly stationary
high pressure ridge will remain in place through the middle to end
of the week when the ridge shifts east and a storm moves onshore.
The flow becomes west to southwest, which may serve to THIN out
the smoke a bit but not push it out. With the trend toward less
rainfall late in the week, the notion of getting rid of smoke
(even temporarily) may be going away as well. Keyes/AD
&&
.PIH WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Area Forecast Discussion
National Weather Service Blacksburg VA
1121 PM EDT Tue Sep 5 2017
.SYNOPSIS...
A cold front will move slowly through central Mid Atlantic
region tonight. High pressure will start to build in from the
upper Mississippi valley behind the front, with some improving
conditions later on Wednesday. The high will become established
over the region, bring fair conditions through the end of the
workweek and into the weekend.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 1115 PM EDT Tuesday...
Cold front had advanced to the Blue Ridge this evening and will
be slow to cross the region tonight. Overall synoptic lift will
remain robust thanks to diffluence from upper level jet, good
mid level deformation, and vigorous short wave energy associated
with as a large upper trof digs into the eastern US. This will
keep some showers around through the overnight period in an
environment of lingering deep moisture with some patchy fog
around. Have adjusted and lowered the probability of
precipitation through early Wednesday morning, similar to last
few runs of the HRRR and RAP guidance which looks reasonable
compared to latest radar trends.
Gradual improvement will become established from west
to east later on Wednesday as upper dynamics start to pull out
and allow high pressure over the mid Mississippi valley to start
building in.
With clouds and showers around, overnight temperatures will be
slow to fall. Expect lows in the low/middle 60s east of the
Ridge with mid/upper 50s west. Lingering clouds/showers on the
cool side of the front will keep temperatures in check tomorrow
with highs around 70 east to mid 60s west.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 250 PM EDT Tuesday...
Strong upper trough will pivot east across the area Wednesday night
finally helping push the surface cold front to the east of the
region during the evening. Given slowness of these features
along with ripples of energy aloft riding up the boundary, will
leave in some chance pops Wednesday evening before drying things
out overnight. Drier and cooler weather will follow the front
for Thursday into Friday night as high pressure slides in from
the southwest and the upper trough slowly lifts back to the
north. Given the cool pool aloft Thursday along with upslope
flow, cant totally rule out more clouds and perhaps a
sprinkle/shower northwest slopes. Otherwise running with more
sun and without pops for now. Temps to drop to below normal with
highs 60s mountains and low/mid 70s east given the strong cool
advection regime. Will be quite cool but comfortable during the
overnights as well with lows in the 40s and 50s with the coolest
likely Friday morning with the high about overhead.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 130 PM EDT Tuesday...
Initial upper trough will lift out on Saturday leaving a rather
complicated 5h pattern between ridging across the Great Lakes over
top developing weak troffiness to the south. This latter piece of
upper troffiness likely a factor in just where Irma to the south
will end up toward Days 6 and 7. Otherwise will start with a very
strong surface ridge/wedge of high pressure extending south down
along the Appalachians, keeping dry/comfortable weather in place
Saturday/Sunday and perhaps Sunday night. A secondary weak mid level
wave will cross the region later Saturday but appears too dry for
any showers at this point. Highs mostly 60s mountains to mid 70s
southeast.
Model consensus suggests that tropical moisture will be on the
increase by at later Monday into Tuesday as Irma heads farther
north. However confidence remains low in exactly where the
system will go with varying solutions from west to east by the
end of the period. Still appears enough though for increasing
rain/wind espcly Monday night into Tuesday at this point, so
running with high pops pending further evolution in later model
runs. This should make for a rather chilly period given rain
into the wedge with highs mostly 60s to low/mid 70s with even
some 50s possible if heavy rain does pan out. Otherwise for the
latest update on the track, and intensity information on Irma,
visit the NHC website.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
As of 745 PM EDT Tuesday...
Line of thunderstorms was the leading edge of a band of
precipitation from near KROA into South Carolina. A cold front
was just crossing through KBLF and KLWB at 00Z.
The cold front will be slow to cross the region tonight. Overall
synoptic lift will remain robust thanks to diffluence from
upper level jet, good mid level deformation, and vigorous short
wave energy associated with as a large upper trof digs into the
eastern US. This will keep some showers around through the
overnight period. High confidence that ceilings will lower to
MVFR then IFR behind the front and showers overnight. Expect
slow improvement in ceilings after 15Z/11AM on Wednesday.
Confidence low on timing but overall KBLF, KBCB and KLWB will
become VFR during the afternoon as drier air works into the
area.
Extended Aviation Discussion...
A deep meridional upper trough will continue to develop through
Thursday.The front should be near the coast Thursday but since
the upper trough axis will still be west of our region, expect
periods of sub-VFR conditions with showers in the mountains
Thursday, becoming VFR east of the Blue Ridge. VFR conditions
should return to all areas Friday and continue Saturday and
Sunday.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...AMS/MBS
NEAR TERM...AMS/MBS
SHORT TERM...JH
LONG TERM...JH
AVIATION...AMS/MBS
Area Forecast Discussion
National Weather Service Tallahassee FL
931 PM EDT Tue Sep 5 2017
.NEAR TERM [Through Tonight]...
This evening`s surface analysis showed a cold front across
central GA and AL, though it was difficult to distinguish between
the composite of convective outflow bounaries from the synoptic
cold front. The front was moving slowly southeast and will move
into the northern portions of our forecast area later tonight.
Most of the CAMs, including the most recent HRRR runs, forecast
the bands of thunderstorms currently accompanying this front to
dissipate before reaching the northern portions of our forecast
area later tonight. However, the thermodynamics still appear
supportive of deep moist convection, and Q-G forcing is likely to
increase overnight as a strong upper trough develops over the
eastern CONUS. Thus we expect scattered storms to reach southeast
AL and south GA between 04 UTC and 08 UTC. Additionally,
scattered storms will develop across the Gulf coastal waters
toward dawn, possibly moving ashore the FL Big Bend coast at
times.
&&
.PREV DISCUSSION [726 PM EDT]...
.SHORT TERM [Wednesday Through Thursday Night]...
An anomalous northern stream trough will deepen into the Southeast
tomorrow, with its core of +PV lifting back into the Great Lakes
and Northeast by Friday night. At the surface, an associated cold
front will move through the Tri-State region tomorrow morning
through the evening. Drier and cooler air will filter in behind
the front, with lows Wednesday and Thursday night ranging from the
upper 50s across southeast Alabama, to the mid 60s from Valdosta
through Panama City, and up to the low 70s in the southeast Big
Bend. On Thursday, high temperatures will only reach the low 80s
for most locations.
.LONG TERM [Friday Through Tuesday]...
The weekend will feature gradually warming high and low
temperatures, with only slight rain chances across the southeast
Big Bend where the front will remain stalled. The main concern in
the extended range is the future location of Hurricane Irma.
Global models remain split between Irma moving up the east coast
of Florida or the west coast. A far eastern track would have very
little impact on the region, while a western track (depending on
how far west) could pose a larger rain, surge, and wind threat.
For now the best course of action is for folks across the region
to continue preparing their disaster kits and coming up with
action plans should Irma`s track narrow in on the region. Stay up
to date with the latest forecasts for Irma via the NHC at
www.hurricanes.gov or through your local NWS site at
www.weather.gov.
.AVIATION [Through 00Z Thursday]...
Scattered TSRA were occurring along a cold front moving slowly
southeastward across central AL and GA. Some of these storms may
reach the KDHN area later this evening before dissipating in the
cooling hours of night. Additional SHRA/TSRA will develop along
or behind the cold front Wednesday, mainly in the afternoon,
temporarily affecting all terminals at times during the
afternoon. Winds will veer from SW to NW 5 to 10 knots during the
day Wednesday. Outside of TSRA conditions will be VFR.
.MARINE...
Relatively light winds and lows seas will increase to near
Advisory levels in the wake of a cold front beginning Wednesday
night. By Thursday evening conditions are expected to subside
below headline levels once again. By this weekend, wind and seas
are expected to gradually increase as Irma nears Florida. The
exact path of Irma is uncertain once it reaches Florida and thus
the impacts are uncertain at this time.
.FIRE WEATHER...
Hazardous fire weather conditions are not expected.
.HYDROLOGY...
A cold front passing through the region tomorrow will bring, on
average, less than an inch of rain across the Tri-State area.
Amounts between 2-3" will be possible, but should be extremely
isolated. Dry conditions will prevail though most of the weekend,
but next week`s rain forecast remains highly dependent on the
actual track of Irma. Stay tuned.
.SPOTTER INFORMATION STATEMENT...
Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur by calling the office or tweeting us @NWSTallahassee.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 73 86 65 83 65 / 20 60 20 0 0
Panama City 76 84 68 82 67 / 30 50 10 0 0
Dothan 71 81 58 80 59 / 40 60 0 0 0
Albany 72 83 60 82 59 / 40 60 10 0 0
Valdosta 72 87 64 83 64 / 30 60 30 0 0
Cross City 74 84 70 86 70 / 30 50 20 10 10
Apalachicola 75 84 69 84 70 / 30 40 20 0 0
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...None.
&&
$$
NEAR TERM...Fournier
SHORT TERM...Harrigan
LONG TERM...Harrigan
AVIATION...Fournier
MARINE...Harrigan
FIRE WEATHER...Fournier
HYDROLOGY...Harrigan