Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/13/17
Area Forecast Discussion
National Weather Service Albany NY
1037 PM EDT Wed Jul 12 2017
.SYNOPSIS...
A frontal boundary will remain nearly stationary, wavering
southward tonight into Thursday, then slightly northward by
Friday. This boundary will provide the focus for several rounds
of showers and thunderstorms through the end of the work week.
Warm and humid conditions through Thursday, will give way to
cooler conditions on Friday.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 1030 PM EDT...Mid level jet max and short wave trough was
moving across eastern NY. This has resulted in an area of
convection along a diffuse frontal zone north of I90. Mesoscale
models not much help either as these zonal flows are always a
challenge from a numerical standpoint. So through the overnight
the best chance for additional convection will be across the
northern half of the region. As PWATs are over 1.5" per the 00Z
soundings from here at BUF, still the threat for localized heavy
rainfall. Otherwise a muggy night for most of the region as
dewpoints were well into the 60s to near 70F. Of note, dewpoints
across northern NY were into the 50s with some 40s with a very
light northerly wind (more like light and variable).
Prev Disc...
We will have to watch for how the convection across
central/western NY evolves as it moves eastward into our area
later this evening and overnight. Hi-res CAMs showing a variety
of solutions in the zonal flow aloft, with the HRRR most
aggressive with an area of widespread convection moving through,
and the 3km NAM much less so with very little activity across
the southern half to two-thirds of the area. Will opt somewhere
in between, since there is an area of scattered convection
across the I-81 corridor, with a larger cluster of showers and
storm over central Lake Ontario. Will mention likely pops for
areas west of the Hudson Valley before 2 AM, the spreading south
and east from from the Capital District into western New
England from 2 AM to 6 AM.
High freezing levels and warm rain processes contributing to
torrential rain within the convection. Main threats continue to
be heavy rainfall and lightning, with PWATs over 1.50 inches and
surface dewpoints in the upper 60s to lower 70s.
Much of the rainfall overnight may set up to the north of areas
that received rainfall earlier. However, if these areas of
rainfall overlap, an additional flash flood watch may be needed
later on, mainly near the Mohawk Valley. It will remain warm and
muggy tonight, as the main cold front will still be positioned
generally north of the area, although the front should settle
south into the Adirondacks and Lake George area tonight.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
More showers and thunderstorms are expected for Thursday, as
the aforementioned cold front pushes southeastward across
central/southern part of the region. The front will impinge on
the warm/moist air mass in place with PWATs continuing to be
anomalously high around +1 to +2 STDEV. Once again, SBCAPE
values will be around 1000-2000 J/Kg across areas mainly south
of Albany. 0-6 km shear forecast to be around 25-30 kt, so
multicell clusters will likely be the main convective mode.
Similar to today, the main threats should be locally heavy
rainfall and lightning, although isolated strong gusty winds
will also be possible across southern areas. There continue to
be Marginal Risk for severe storms there. Local flooding of
urban/poor drainage locations may occur again, with isolated
flash flooding. Areas that receive heavy rainfall today/tonight
will be most susceptible for flash flooding on Thursday. It will
continue to be very warm and muggy ahead of the front with
lower to mid 80s for highs from Albany south, but cooler 70s
north and west.
The front is expected to actually move through the entire area
Thursday evening, but will then stall just to our south late
Thursday night, with waves of low pressure rippling along the
boundary. So will continue to mention high chance to likely pops
for additional showers and thunderstorms. Highest pops across
the southern half of the area, closest to the boundary.
Despite being on the cool side of the front on Friday, the
boundary will start to slowly lift northward with continued
waves of low pressure along the front. This will result in yet
more showers for Friday. Will continue to mention chance of
thunderstorms as well, due to forecast elevated instability
despite stable low levels. Depending on where convective
elements develop, the threat for locally heavy rainfall may
persist on Friday. There is uncertainty with QPF for Friday,
which will depend on the eventual movement/position of the
front. Highs will only be in the 60s to lower 70s with plenty of
clouds around. Showers and storms could persist well into
Friday evening, before decreasing overnight as low pressure
finally moves east of the area.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
The long term period continues to look rather unsettled.
Saturday and Saturday night...Lingering showers Saturday
morning and early afternoon will give to a brief drying trend
late Saturday afternoon and Saturday night as a ridge of high
pressure briefly builds into the region.
Sunday through Tuesday...More unsettled weather is expected as
a cold front drops southeast out of eastern Canada and moves
through our region with a wave of low pressure on the leading
edge of the frontal boundary. This boundary may stall just to
our south keeping chances of showers in the forecast through
Tuesday. There will also be a chance of thunderstorms Sunday
through Tuesday mainly during the afternoon and early evening
hours.
Wednesday...GFS and ECMWF both suggesting a brief surface high
pressure and dry conditions on Wednesday but with precipitation
surrounding us to the north and South, it is tough to say if
there will be some lingering showers or not, so going with
slight chance as of now.
Temperatures throughout the period will be seasonable with
highs in the upper 60s to mid 80s Saturday and Sunday and mid
70s to upper 80s Monday through Wednesday, overnight lows are
expected to be in the mid 50s to upper 60s. Precipitation for
the period looks to be well above normal with an inch or more of
rain possible in many areas for the period of Saturday through
Wednesday.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Quasi-stationary frontal zone with waves of convection will
continue to move across the region. Timing remains quite a
challenge as vicinity showers along with vicinity of
thunderstorms were used in the TAFs. Flight categories will also
be quite as challenging as we will retain VFR into early evening
then trend toward MVFR tonight. Due to high low level moisture
in place, potential for IFR conditions with respect to CIGS
could be realized, as the best potential will be for KPSF.
Winds will generally be light and variable less than 10kts
outside of any convection. A light westerly wind evolves through
Thursday.
Outlook...
Thursday Night: Moderate Operational Impact. Likely SHRA...TSRA.
Friday: High Operational Impact. Likely SHRA...TSRA.
Friday Night: Moderate Operational Impact. Likely SHRA...TSRA.
Saturday: Moderate Operational Impact. Chance of SHRA.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Low Operational Impact. Chance of SHRA...TSRA.
Sunday Night: Low Operational Impact. Chance of SHRA...TSRA.
Monday: Moderate Operational Impact. Chance of SHRA...TSRA.
&&
.FIRE WEATHER...
A frontal boundary will remain nearly stationary wavering
across the region through Friday. This boundary will provide the
focus for several rounds of showers and thunderstorms through
the end of the work week. Warm and humid conditions through
Thursday, will give way to cooler conditions on Friday. Most
areas will see at least a few rounds of rainfall through Friday.
&&
.HYDROLOGY...
Tonight into Friday, periods of showers and thunderstorms will
continue along a frontal boundary oscillating through the area
in a very moist air mass. Repeated rounds of rainfall are
possible, leading to significant runoff in some locations. The
threat of convection with embedded heavy rainfall will remain
mainly north of I-90 tonight, expanding throughout the forecast
area by Thursday, as the front gradually pushes southward. Exact
locations of heaviest rainfall is still uncertain, especially
due to convective nature of the rainfall. The front will slowly
lift back northward on Friday, with additional showers and
thunderstorms.
Current forecast calls for basin average rainfall of 1 to 2
inches, but locally higher amounts are likely within any
persistent/repeated thunderstorms over the next few days. Main
stem river flooding is currently not expected, but we will
continue to monitor trends. Localized urban and poor drainage
flooding is possible, with isolated flash flooding as well.
Mainly drier weather is expected over the weekend, although
isolated to scattered showers and thunderstorms cannot be ruled
out.
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...Thompson/JPV
NEAR TERM...BGM/JPV
SHORT TERM...JPV
LONG TERM...Cebulko
AVIATION...SND/BGM
FIRE WEATHER...Thompson/JPV
HYDROLOGY...Thompson/JPV
Area Forecast Discussion
National Weather Service Bismarck ND
953 PM CDT Wed Jul 12 2017
.UPDATE...
Issued at 948 PM CDT Wed Jul 12 2017
Little change with this update other than for observed trends
through 0230 UTC. Did increase cloud cover central as stratus
appears to be expanding westward towards US Highway 83 with
sunset. Fog potential central remains on the western fringe of the
stratus tonight into Thursday morning per the RAP/HRRR through
their 01 UTC iterations.
UPDATE Issued at 634 PM CDT Wed Jul 12 2017
Added a mention of patchy fog to central North Dakota for late
tonight into Thursday morning as the RAP and HRRR through their 22
UTC iterations has consistently shown within their visibility
forecasts the potential for fog along the western edge of the
stratus across central North Dakota late tonight into Thursday
morning. Also, per webcam observations, added a slight chance
mention of rain showers to the James River Valley through sunset.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 205 PM CDT Wed Jul 12 2017
Cool and quiet and tonight. Warm-up begins in the west Thursday.
Cloud shield over western and central North dakota continues ti
erode this afternoon from the north and south. High pressure
building south from Canada tonight should help to dissipate clouds
across all but eastern portions of central ND. It will be cool
tonight with lows mainly in the 50s but a few 40s are certainly
possible over normally cool areas.
On Thursday, a deepening upper trough over northern Minnesota
appears to be delaying the building upper heights from the west.
This will keep clouds across eastern portions of central ND
through at least a portion of the morning and will limit daytime
heating. we lowered forecast highs from the previous forecast,
but not quite as low as guidance. It will warm nicely in the far
west with highs approaching the 90 degree mark.
.LONG TERM...(Thursday night through Wednesday)
Issued at 205 PM CDT Wed Jul 12 2017
Upper level ridging and thermal ridging begin in earnest as we
start the long term period. Highs mainly in the 90s are expected
Friday through Monday, with a few readings in the 100 to 105
degree range, especially on Friday. Will need to monitor for
potential heat advisory on Friday. Weak shortwave energy
progressing through upper ridge will induce surface low pressure
over eastern Montana Friday. The upper disturbance and associated
cold front will drop southeast through the forecast area Friday
night bringing a chance of thunderstorms, followed by slightly
cooler temperatures (especially north and east) Saturday.
Upper ridge flattens from the northwest U.S into central Canada,
flopping the ridge eas across the forecast area. Surface low
pressure will also become established over eastern Montana. Hot
temperatures and increasing southerly winds ahead of the Montana
low, may bring near critical fire weather conditions to the
southwest corner of the state, where Sunday afternoon relative
humidities may drop into the 10 to 15 percent range. Will need to
monitor for possible Fire Weather Watch.
Upper ridge continues to flatten into early next week. Still
pretty warm on Monday, but trend more to near normal temperatures
by mid week. With a more of a quasi-zonal flow in store next week
we could should enter a little more active pattern as far as
precipitation chance.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 948 PM CDT Wed Jul 12 2017
MVFR stratus is expected to remain across much of central North
Dakota tonight, impacting KJMS, and potentially KMOT and KBIS as
it slowly expands west. A few pockets of IFR are possible Fog is
also possible central late tonight into Thursday morning. KBIS and
KMOT are the most likely terminals to be impacted. VFR conditions
are expected across all of western and central North Dakota by
late Thursday morning and into the afternoon.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...PA
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...PA
Area Forecast Discussion
National Weather Service Columbia SC
1055 PM EDT Wed Jul 12 2017
.SYNOPSIS...
High pressure ridging into the area from the western Atlantic
will bring warm and humid conditions through the end of the
work week. A cold front will stall over the area this weekend,
bringing increasing chances for showers and thunderstorms which
may linger into early next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Convection has diminished over the past couple of hours with a
few cells persisting over Aiken County and the Augusta area.
Satellite imagery shows the cloud tops slowly warming and with
increasing stability over the next couple of hours expect
remaining convection to dissipate by 1am. Remainder of the
forecast area remains mostly clear and will expect some stratus
clouds to develop during the early morning hours. Overnight lows
remain on track for low 70s at most locations.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Hot and relatively dry conditions are expected to close out the
work week as a strong upper ridge remains over the Carolinas
into the eastern Gulf coast states.
An upper trough digging into the Ohio Valley and northeastern
states on Friday will weaken the upper ridge a bit. Surface
high pressure centered well offshore will provide a continual
light south to southwesterly flow over the forecast area. There
will be little if any triggers for convection with no upper
disturbances or surface boundaries in place despite forecast
moderate instability. Wind shear is extremely weak with storm
motions generally less than 10 knots. Forecast soundings
indicate a subsidence capping inversion around 700-800mb with
700mb temps very warm around +10C to +11C with precipitable
water values generally around 1.5-1.6 inches, all factors
limiting convection. Therefore will hold on to only slight
chance pops northwestern Midlands area on Thursday and dry
elsewhere, with slightly higher pops on Friday with a slight
weakening of the upper ridge but overall coverage expected to
remain isolated.
Temperatures Thu/Fri will be in the mid to upper 90s for highs
and mid to upper 70s for overnight lows. Heat index values both
days will peak out in the 100-105 range which remains below
advisory criteria but those who will be spending time outdoors
would be wise to take frequent breaks and stay hydrated.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
The extended forecast period features a more active weather
pattern as a positively tilted upper trough dives southeastward
across VA/NC Saturday and crosses the forecast area on Sunday. A
frontal boundary will push into the region late Saturday and
stall near our area Sunday and remain in place into early next
week providing a focus for convection. Precipitable water values
rise back to at or above 2 inches Sat/Sun as moisture transport
over the area increases. This moisture combined with moderate
instability and the upper energy along with the surface boundary
should provide enhanced chances of showers and thunderstorms,
especially across the northern and eastern Midlands into Monday.
A second shortwave trough will dive south across the Mid-
Atlantic Mon/Tue which will keep a mention of diurnal convection
in the forecast through the end of the period.
Temperatures will be above normal on Saturday with highs in the
mid 90s then slightly cooler max temperatures Sunday through
next week back near normal. Low temperatures will be near normal
through the period.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Expect mainly VFR conditions during the TAF period except for
possible afternoon thunderstorms and early morning stratus and
fog.
High pressure ridging into the region from the Atlantic will
dominate during the TAF period. Nocturnal cooling and low-level
moisture in an onshore flow may help support stratus and fog.
The HRRR suggests greater low-level moisture in the southeast
section affecting mainly the OGB and AGS terminals. A period of
MVFR or IFR conditions may occur during the 09z to 14z time
frame. A little mixing associated with a weak low-level jet
plus weak instability indicates it may be more of a stratus
than fog restriction. Heating and mixing should help dissipate
any stratus or fog by 15z. Strong heating may help support
afternoon thunderstorms but upper ridging should limit coverage.
The thunderstorm chance was too low to include in the terminal
forecasts at this time.
EXTENDED AVIATION OUTLOOK...Restrictions possible each day in
late night/early morning stratus/fog, along with scattered
to numerous mainly afternoon and evening thunderstorms.
Thunderstorm coverage will likely be greatest Saturday and
Sunday associated with a slow moving cold front.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Dodge City KS
1102 PM CDT Wed Jul 12 2017
...UPDATE TO SYNOPSIS...
.SYNOPSIS...
Issued at 1100 PM CDT Wed Jul 12 2017
WV imagery indicates a weak upper level ridge of high pressure
stretching across the Deep South with a west-southwest flow aloft
prevailing across the Western High Plains. Near the surface, a
near slow moving cold front extends from southeast Colorado
northeastward across western Kansas.
&&
.SHORT TERM...(This afternoon through Thursday)
Issued at 1230 PM CDT Wed Jul 12 2017
Heating up rapidly once again this afternoon, with all locations
climbing quickly through the 90s. SW winds with downslope
components and prefrontal compressional effects will allow most
locales to eclipse 100 once again this afternoon. Weak stationary
frontal boundary is expected to straddle the DDC/GLD CWA border
this evening, where surface convergence will lead to scattered
thunderstorm development during the 5-7 pm timeframe. Latest
HRRR solutions trending toward 12z NAM, depicting an impressive
thunderstorm complex over east central Colorado, pushing NE into
NW Kansas 7-10 pm. Much of this complex will likely bypass the
DDC CWA, but outflow from it is expected to assist the frontal
boundary to sag southward tonight. Along the frontal boundary,
will need to monitor storms early this evening for marginal wind
and hail potential (up to quarters, 50-60 mph) per 5% wind/hail
probabilities from SPC Day 1 outlook. Given the hot boundary layer
and well-mixed subcloud layers, feel outflow winds will be primary
threat across the northern zones this evening.
Weak cold front will spread southward tonight, ushering in N/NW
winds of 10-20 mph. Feel NW Kansas convection will give the front
a good push, but despite the surface convergence, 593 dm heights
and subsidence from ridging aloft are expected to squash
thunderstorms roughly south of K-96 tonight.
Thursday...Cooler, but exactly how much cooler is up for debate. A
much more difficult temperature forecast than is typical of
summer. NAM-based solutions are MUCH cooler for Thursday,
suggesting many locations will struggle to climb out of the 70s
north of US 50. While likely overdone, this cooldown may be
correct if the NAM`s depiction of post-frontal stratus comes to
fruition. But it is July, and any breaks of sunshine will send
temperatures soaring, so compromised between the coolest and
warmest guidance. This gives mid 80s NW, to near 90 at Dodge City,
to near 100 near Medicine Lodge. Surface boundary and its
associated convergence will be meandering over SW KS during peak
heating, as such expect another crop of scattered showers and
thunderstorms by late afternoon. High pressure aloft with
592-594 dm heights will limit wind shear and instability, with
warm 500 mb temperatures and weak flow aloft. Regardless, boundary
layer moisture will be plentiful (dewpoints in the 60s), so SPC`s
marginal 5% wind/hail probabilities are warranted along the
frontal zone.
.LONG TERM...(Thursday night through Wednesday)
Issued at 200 PM CDT Wed Jul 12 2017
The break from the heat will continue on Friday, as the stationary
frontal boundary meanders over the central plains. Models prog a
NE surface wind, plenty of clouds, and at least isolated showers
and thunderstorms, which together should be enough for most
locations to hold in the 80s Friday afternoon. Max temp grids for
Friday are close to the 12z MAV/MEX guidance, with a high of 86 at
Dodge City. Not cool and refreshing, but not 100 either. You take
what you can get in July. Upper high will be centered in Colorado
on Friday, which will allow for the cooler N/NE flow, and isolated
pops were retained for all zones.
Still expecting the upper anticyclone to recenter over Nevada,
Utah and the Great Basin over the weekend. This will hold
temperatures near mid-July normals (lower 90s). Isolated to
scattered late day storm coverage looks to favor Saturday, as
12z ECMWF shows a subtle weak shortwave flirting with SW KS on the
eastern periphery of the ridge aloft.
All medium range models including 12z GFS/ECMWF show the hot upper
high establishing over the central plains early next week.
Forecast becomes dry starting Monday, with an upward trend in
afternoon temperatures next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 655 PM CDT Wed Jul 12 2017
Extremely slow moving cold front straddled across west central
into north central Kansas is the focus for a few strong to severe
thunderstorms going forward this evening. Best chances for a
thunderstorm in vicinity of a terminal will be at HYS and GCK
though midnight. Additionally nam/wrf indicated a return LLJ
development well after 3z with wind shear in the lowest 2000 ft.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 70 88 67 86 / 0 30 30 20
GCK 70 85 66 88 / 20 30 40 20
EHA 66 88 64 88 / 0 30 30 30
LBL 70 90 66 88 / 0 30 30 20
HYS 70 88 66 86 / 80 50 60 20
P28 73 99 72 93 / 0 10 30 20
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...JJohnson
SHORT TERM...Turner
LONG TERM...Turner
AVIATION...Russell
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
706 PM EDT Wed Jul 12 2017
.AVIATION...
Aside from a stray shra/tsra this evening, expect area terminals
will have to wait for convection firing over Wisconsin to evolve
into MCS and move into lower Michigan. Adjusted timing to closer
reflect recent HRRR runs (really the only model that has even made
an attempt to simulate regional convection over the past 6 hours).
Assuming the storms over Wisconsin do continue to organize, the
resultant activity will track through the regional between 04z-06z
and 10z-12z (with some potential of lingering shras/tsras I-94 south
into mid morning). Additional convection may occur mid/late in the
afternoon, but confidence in timing/location is very low.
For DTW...While an isolated shra/tsra may pop up in vicinity of the
terminal this evening, expect the best chance of thunderstorms will
occur roughly 07z-09z through 11z-13z. Additional activity may also
occur 20z-22z and beyond, but confidence is much lower.
//DTW THRESHOLD PROBABILITIES...
* Moderate in thunderstorms late tonight through early Thursday
morning...low Thursday afternoon.
* Moderate in ceilings below 5000 ft tonight and Thursday morning.
&&
.PREV DISCUSSION...
Issued at 325 PM EDT Wed Jul 12 2017
DISCUSSION...
Strong upper level jet tracking through the Northern Great Lakes as
Upper Level Trough/Low along the southern Manitoba/Ontario border
drops southeast into Lake Superior overnight. On the southern fringe
of this feature, mainly convectively induced disturbances ejecting
East out of the Central Plains/Midwest. Clouds and
showers/thunderstorms through much of the day has limited
destabilization over Southeast Michigan, and the main moisture axis,
as seen in the 850-700 MB Theta-E ridge is oriented more in a
west-east fashion across far southern Lower Michigan this afternoon.
With the current activity around Chicago drawing in question how
much we will be able to destabilize late today/early this evening,
severe chances appear slight at best and mainly toward Ohio border
as we have very little instability with temps still mostly in the 70s
at present time (Still think we should be able to sneak into the low
to mid 80s by sunset however).
In addition, the low level jet this evening and overnight is
slowing veering/not backing, and could see bulk of activity
shower/thunderstorm activity just along and south of the Michigan
border. None-the-less, the north half of the CWA still has the
surface low and actual cold front to work with, along with the
increased forcing/height falls overnight, so was somewhat reluctant
to drop the flood watch, but with the lack of rain today across the
northern half of the CWA, felt if big complex developed over
Minnesota/Wisconsin it would be weakening and progressing east fast
enough overnight to keep any flooding minor up north. Flood watch
continues for locations along and south of I-69.
Tomorrow there will be one more opportunity for a disturbance to
come out of the Midwest generating showers and thunderstorms (mainly
southern areas) before the mature and impressive mid level dry slot
(30-40 C dew pt depressions at 700 MB) and excellent drying occurs
Thursday Evening/Night as PW values drop below 1 inch. Stronger wind
fields tomorrow, with potential of MLCAPES reaching around 2000 J/kg
will pose a marginal risk of severe storms south of M-59.
An upper-level low and a series of upper-level disturbances will
bring the slight chance to see rain and thunderstorms throughout the
day on Friday. As the low moves east, it will act to turn wind flow
from the west to northwest, which will bring relief from the warm
and humid conditions, as noted by forecasted dewpoints in the low
60s expected by the afternoon. As the low moves out of the region, a
high pressure will then move in from the North Central plains, and
will reside over Michigan late Friday into Saturday, which will act
to suppress rain chances.
Slightly higher confidence regarding rain and thunderstorms chances
throughout Sunday. An upper-level trough and a series of upper-level
disturbances are expected to dig into Michigan throughout Sunday,
which would act to bring precipitation Sunday morning into Sunday
evening. Better convergence is seen between the GFS and GEM, and to
some extent the ECMWF regarding sheared vorticity that moves through
during this time. Additionally, all models pick up on a weak cold
front that pushes through on Sunday, providing additional lift for
precipitation. As a result, PoP values are being increased to 40 -
60 percent.
For the last half of the extended forecast, a broad surface high
pressure system is expected to move in across Michigan starting
early Monday, and will stick around through the middle of the week.
This will again bring the chance to see relatively dry conditions
along with extended periods of sunshine through Wednesday.
MARINE...
Northeast winds will continue to gust to 25 knots over the northern
portion of Lake Huron through this evening as this area remains on
the north side of a frontal boundary draped over the area. The
remainder of the area will see lighter winds more from the south,
but will also have a much higher potential to feel the effects of
rounds of showers and thunderstorms that will develop and move
through the Great Lakes region. The best coverage of thunderstorms
looks to be this evening and overnight as the frontal boundary
begins to slowly slide southward, mainly impacting the Lake Erie,
Lake St Clair, and the southern portion of Lake Huron. Storms will
have the potential to become severe, with the biggest threat being
damaging wind gusts to 50 mph. The very warm and humid airmass will
also allow very heavy rainfall to occur with thunderstorms, and
could also lead to the development of fog over the lakes. Showers
and thunderstorms will again be likely on Thursday as low pressure
crosses the area, with the best potential for any stronger storms
towards Lake Erie.
High pressure will build into the area on Friday, bringing dry
weather and northwest winds between 10 and 15 knots.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Flood Watch through Thursday morning for MIZ060>063-068>070-075-076-
082-083.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....DG
DISCUSSION...SF/AM
MARINE.......HLO
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Quad Cities IA IL
644 PM CDT Wed Jul 12 2017
...AVIATION UPDATE...
.UPDATE...
Issued at 520 PM CDT Wed Jul 12 2017
A late afternoon surge of warmer temperatures has pushed heat
index values into the 95 to 100 degree range over most of the
advisory area.
Cloud cover and rain earlier today has kept temperatures in check
across Whiteside, Bureau, and Putnam counties. Thus the heat
advisory there has been cancelled.
&&
.SYNOPSIS...
Issued at 339 PM CDT Wed Jul 12 2017
18Z surface data has a weak low in northwest Wisconsin. A cold front
ran from the low into southwest Iowa and southern Nebraska. Another
boundary can be inferred from northern Indiana back into northeast
Iowa. Dew points ahead of the cold front were in the 70s. Behind the
front dew points were in the 60s.&&
.SHORT TERM...(This Evening through Thursday)
ISSUED AT 339 PM CDT Wed Jul 12 2017
First, the heat advisory will continue to expiration. Cloud cover
has suppressed temperatures today to the east and north of the Quad
Cities. However, heat index readings are close to or achieving the
advisory to the south and west of the Quad Cities.
Tonight, a flash flood watch has been issued roughly along and south
of a line from Sterling, IL back to Washington, IA and then south to
Fairfield, IA.
Moisture levels tonight will be higher than last night. Internally
the models are indicating thunderstorms will grow upscale into one
or more organized complexes. Additionally, trends with the RAP
suggest that storms may move over the same areas. Since storms will
be very efficient in producing rain, rainfall has the potential to
be excessive tonight.
Isolated showers and thunderstorms late this afternoon will become
more numerous after sunset and grow upscale into the previously
mentioned complexes. The best chances for rain look to be after
midnight across roughly the southeast two thirds of the area.
Thursday, the organized thunderstorm complex will slowly decay
during the morning as the cold front pushes through the area.
Boundaries left over from the complex will then provide the focus
for new convection during the afternoon across the southeast third
of the area.
.LONG TERM...(Thursday Night through Wednesday)
ISSUED AT 339 PM CDT Wed Jul 12 2017
Thursday Night through Saturday
Sfc high pressure sliding from north to south through the
Mississippi Valley will give us a break from the active weather.
We`ll also get some relief from the +95 F heat indices. 850mb temps
are forecast to fall below 15 C on Friday, which is in line with max
sfc temps in the upper 70s north to lower 80s southwest (and lows
around 60 F). Return flow on Saturday will cause sfc temps to rise a
few degrees into the mid 80s on avg.
Saturday Night and Sunday
Upper jet streak and mid-level shortwave forecast to dive down on
the eastern periphery of the ridge into the Western Great Lakes
region. Attendant cold front could bring scattered storms to E
Iowa/NW Illinois during this time. However, confidence is low on
coverage as reflected in the low end 20% PoPs. It is also too early
to discuss the potential for severe weather. That said, deep layer
shear is progged to increase ahead of the shortwave, so it`s
something we`ll have to monitor over the coming days.
With the cold front moving through on Sunday, forecast max temps
have a greater spatial range than the previous few days - from lower
80s far north to lower 90s southwest. Otherwise, expect humid
conditions with dewpoints in the upper 60s/near 70 F until the front
passes your location.
Monday through Wednesday
Short break in the high humidity on Monday before the Western U.S.
and Plains upper ridge expands and shifts eastward. Forecast
consensus has the hot and muggy air returning by Tuesday and
Wednesday. This could potentially be another active "ring of fire
pattern" with periodic rounds of thunderstorms as disturbances aloft
ride to the SE over a nearly stationary sfc boundary and hot/humid
air mass.
&&
.SHORT TERM...(This Evening through Thursday)
ISSUED AT 339 PM CDT Wed Jul 12 2017
First, the heat advisory will continue to expiration. Cloud cover
has suppressed temperatures today to the east and north of the Quad
Cities. However, heat index readings are close to or achieving the
advisory to the south and west of the Quad Cities.
Tonight, a flash flood watch has been issued roughly along and south
of a line from Sterling, IL back to Washington, IA and then south to
Fairfield, IA.
Moisture levels tonight will be higher than last night. Internally
the models are indicating thunderstorms will grow upscale into one
or more organized complexes. Additionally, trends with the RAP
suggest that storms may move over the same areas. Since storms will
be very efficient in producing rain, rainfall has the potential to
be excessive tonight.
Isolated showers and thunderstorms late this afternoon will become
more numerous after sunset and grow upscale into the previously
mentioned complexes. The best chances for rain look to be after
midnight across roughly the southeast two thirds of the area.
Thursday, the organized thunderstorm complex will slowly decay
during the morning as the cold front pushes through the area.
Boundaries left over from the complex will then provide the focus
for new convection during the afternoon across the southeast third
of the area.
.LONG TERM...(Thursday Night through Wednesday)
ISSUED AT 339 PM CDT Wed Jul 12 2017
Thursday Night through Saturday
Sfc high pressure sliding from north to south through the
Mississippi Valley will give us a break from the active weather.
We`ll also get some relief from the +95 F heat indices. 850mb temps
are forecast to fall below 15 C on Friday, which is in line with max
sfc temps in the upper 70s north to lower 80s southwest (and lows
around 60 F). Return flow on Saturday will cause sfc temps to rise a
few degrees into the mid 80s on avg.
Saturday Night and Sunday
Upper jet streak and mid-level shortwave forecast to dive down on
the eastern periphery of the ridge into the Western Great Lakes
region. Attendant cold front could bring scattered storms to E
Iowa/NW Illinois during this time. However, confidence is low on
coverage as reflected in the low end 20% PoPs. It is also too early
to discuss the potential for severe weather. That said, deep layer
shear is progged to increase ahead of the shortwave, so it`s
something we`ll have to monitor over the coming days.
With the cold front moving through on Sunday, forecast max temps
have a greater spatial range than the previous few days - from lower
80s far north to lower 90s southwest. Otherwise, expect humid
conditions with dewpoints in the upper 60s/near 70 F until the front
passes your location.
Monday through Wednesday
Short break in the high humidity on Monday before the Western U.S.
and Plains upper ridge expands and shifts eastward. Forecast
consensus has the hot and muggy air returning by Tuesday and
Wednesday. This could potentially be another active "ring of fire
pattern" with periodic rounds of thunderstorms as disturbances aloft
ride to the SE over a nearly stationary sfc boundary and hot/humid
air mass.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
ISSUED AT 641 PM CDT Wed Jul 12 2017
An area of showers and storms will impact all the terminals this evening
with a period or two of MVFR conditions possible in heavy rain and gusty
winds and ceilings 1-3K AGL. After 13/06Z... winds will shift to the
northwest at 5 to 10 MPH with slowly clearing skies and VFR conditions
as high pressure moves in.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Heat Advisory until 8 PM CDT this evening for Benton-Buchanan-
Cedar-Clinton-Delaware-Des Moines-Dubuque-Henry IA-Iowa-
Jackson-Jefferson-Johnson-Jones-Keokuk-Lee-Linn-Louisa-
Muscatine-Scott-Van Buren-Washington.
Flash Flood Watch through Thursday morning for Des Moines-Henry
IA-Jefferson-Lee-Louisa-Muscatine-Scott-Van Buren-
Washington.
IL...Heat Advisory until 8 PM CDT this evening for Hancock-Henderson-
Henry IL-McDonough-Mercer-Rock Island-Warren.
Flash Flood Watch through Thursday morning for Bureau-Hancock-
Henderson-Henry IL-McDonough-Mercer-Putnam-Rock Island-
Warren-Whiteside.
MO...Heat Advisory until 8 PM CDT this evening for Clark-Scotland.
Flash Flood Watch through Thursday morning for Clark-Scotland.
&&
$$
UPDATE...08
SYNOPSIS...08
SHORT TERM...08
LONG TERM...Uttech
AVIATION...Nichols
Area Forecast Discussion
National Weather Service Wilmington OH
959 PM EDT Wed Jul 12 2017
.SYNOPSIS...
Warm and humid conditions will continue going into Thursday, as
a cold front slowly moves toward the region. This will lead to
increasing chances of showers and thunderstorms. After the cold
front moves through the area on Friday, drier conditions are
expected, as high pressure moves into the region on Saturday.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Continued monitoring of trends and monitoring CAMs which have
been slow or not able to pick up on existing convection, though
RAP and HRRR in most recent runs are somewhat simulating
existing convection. With the poor handling and complex
convective potential to our NW overnight, confidence is fairly
low in both timing and placement of development overnight.
Convection over northern IL ahead of the frontal boundary firing
up, but little development elsewhere, so have kept precipitation
chances overnight fairly minimal, with higher chances/potential
in the far north as the IL convection slides east.
Muggy conditions overnight with lows only in the lower 70s.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
On Thursday morning, the ILN CWA will remain within a regime of
low-level SW flow and deep-layer WSW flow, providing a continued
unimpeded feed of moisture into the region. As this occurs,
precipitable water values are forecast to rise above 2", with
very deep (>4000m) warm cloud depths. The surface cold front
will still be a bit upstream, and only slowly moving toward the
area. However, the low level flow will be generally convergent
ahead of this front, and there may be some degree of upper jet
support -- though the jet across southern Michigan is sort of
broad, the northern Ohio Valley region is in a favorable
quadrant. All of the above favor the development and maintenance
of thunderstorms across the area on Thursday, with the greatest
chances gradually shifting southward as the day progresses. What
is impossible to say right now is how episodic / MCS-driven this
activity may be, as the environment will be favorable for
upstream complexes to persist as they move into the ILN CWA,
even during the early morning hours. Certainly, there has been
some evidence of this possibility in the high-res models.
Ultimately, a more significant developmental period is expected
to occur by late morning through the afternoon hours. Model
instability forecasts are responsive to the expected 70-72
degree surface dewpoints -- with MLCAPE values forecast to reach
around 2000 J/kg, not an insignificant mixed-layer value for
this area.
Although severe and flood threats are both in play, the winds
through the troposphere is what tilts the threat tomorrow a
little heavier toward the flood side than the severe side.
Overall bulk shear values are somewhat marginal -- a little
higher in the north (30-35 knots) and lower in the south (15-20
knots). Directional shear is mostly unidirectional, which may be
a limiting factor for storm organization, but actually works to
advance the flood concern. The front, the low-level
convergence, the axis of deep moisture, and the wind flow -- all
factors line up parallel across the heart of the ILN CWA by
afternoon. Storm propagation may support training, and with
the wind flow allowing instability to replenish through the day,
multiple rounds will be possible. Thus, a flash flood watch was
not a difficult decision. Its placement focuses on areas where
NWS AHPS QPE analysis from the past 7 days indicates wet
antecedent conditions, another potentially exacerbating factor
for flooding. As for the severe threat, deep cores and forward
propagating segments will bring a risk of damaging winds (and
perhaps some large hail) but without stronger shear, a more
widespread or organized event is unlikely.
The slow motion of the front will mean that storm chances
(though diminishing) will continue into the night, mainly in the
southeastern half of the ILN CWA.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
A cold front is forecast to be draped across the region as the
period begins. Scattered convection is expected to be ongoing
along and ahead of the front. The most uncertainty is exactly
where the front will by at 12Z Friday. Feel like the best chance
of convection will be in the se counties, so carried likely
PoPs there, but errored on the side of caution and kept chance
PoPs across the all of the nrn counties as well. Front is
forecast to move south through the day as H5 s/w swings through
the Great Lakes. Highs on Friday should range from 80-85, with
the typical north to south gradient.
Most of the area should by dry by sunset Friday, except for the
southeast, but they should dry out during the first part of the
evening.
High pressure will build in for Saturday bringing dry conditions.
Highs should be in the 80-85 range again. It looks like most of
Sunday will be dry, but a cold front dropping from the Michigan may
bring some pcpn to the nw counties late in the day. GFS remain a
little more aggressive than the ECMWF with pcpn Sunday night, it is
producing some QPF. Will carry chance PoPs Sunday night.
Weak high pressure will return for the end of the period with highs
in the mid 80s.
&&
.AVIATION /01Z THURSDAY THROUGH MONDAY/...
With a day of dry conditions with some sun and high clouds
overnight, anticipating VFR conditions most locations, with the
exception of some MVFR visibility at KLUK.
While there is a small chance overnight convection may reach as
far south as KDAY/KCMH/KLCK, but confidence is low so as not to
warrant a mention in TAFs.
For Thursday, as gradient tightens a bit, winds increase a bit
from the SW to near 20kts. In the 18-00z timeframe,
greater coverage of thunderstorms expected, with the potential
for MVFR ceilings toward the very end of the period.
OUTLOOK...Thunderstorms through early Friday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Flash Flood Watch from 4 AM EDT Thursday through late Thursday
night for OHZ026-034-035-042>046-051>056-060>065-070>074-
077>082-088.
KY...Flash Flood Watch from 4 AM EDT Thursday through late Thursday
night for KYZ091>093.
IN...Flash Flood Watch from 4 AM EDT Thursday through late Thursday
night for INZ050-058-059-066-073>075.
&&
$$
SYNOPSIS...Hatzos
NEAR TERM...JDR
SHORT TERM...Hatzos
LONG TERM...Sites
AVIATION...JDR
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1039 PM EDT Wed Jul 12 2017
.UPDATE...
Issued at 1039 PM EDT WED JUL 12 2017
No significant changes were made. Latest mesoscale models still
show the possibility of overnight convective precip, but are not
convincing enough to raise the POP for a particular area, much
less area wide. Would not be surprised to see something develop,
but have only used a "silent" POP of 10%.
UPDATE Issued at 736 PM EDT WED JUL 12 2017
Very isolated showers are lingering over the southern part of the
forecast area, and a 20% POP has been placed there for a couple of
hours. Have some concerns about spotty precip during the night as
well. Forecast soundings show low level moisture increasing a
little above the surface tonight. If saturation is reached,
forecast soundings also suggest there may not be much to prevent
showers from bubbling up. Models show some light precip, and MOS
has 20-40% POPs for tonight in our southern and southeastern
counties. With a dry forecast inherited, will wait and get a
glimpse at 00z NAM and upcoming runs of the HRRR before making any
changes (unless actual conditions dictate otherwise).
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 354 PM EDT WED JUL 12 2017
High pressure is centered off to our southeast both at the
surface and aloft this afternoon. Despite the southwest flow at
the surface, dewpoints still range from the low 70s along and west
of I-75 to the low 60s over our far eastern counties. A deeper cu
field in the richer airmass over our southern and western
counties has allowed a few showers to form and a few of these may
grow tall enough to produce a lightning strike or two over the
next couple of hours. Any shower or thunderstorm activity is
expected to diminish by evening.
A muggy night is expected tonight with temps bottoming out a few
degrees warmer than last night due to the increased low level
moisture. There is also a potential for a stratocu field to
develop late in the night with NAM soundings showing some lift and
increasing moisture in the 900 to 775 mb level overnight. This
would also act to keep temps a little elevated with most locations
likely bottoming out only around 70.
The upper level ridge aloft stays firm over our area tomorrow
despite a shortwave digging into the Great Lakes. Forecast
soundings do show only a minimal cap aloft though so isolated to
widely scattered showers/storms are expected to fire over the
entire area by afternoon. Will indicate highest PoPs centered over
our higher terrain along the VA/TN border and up north, closer to
an approaching cold front dropping southward from the Great
Lakes. Will maintain a small chance of showers/storms into
Thursday night as the front draws closer and outflows from
convection associated with it drop into the area. Temperatures
Thursday will be subdued a slight amount by an uptick in clouds,
but should still approach 90. Lows Thursday night will only fall
to around 70 once again.
.LONG TERM...(Friday through Wednesday)
Issued at 409 PM EDT WED JUL 12 2017
The long wave pattern will become a bit more amplified into next
week, as troughing becomes more established across the eastern
CONUS, while ridging consolidates more west of the Mississippi
River. By the middle of next week, the ridging begins to build to
the east once again, with some model differences on the extent and
timing.
Friday will feature the overall stormiest day across the area, as
a short wave trough moves east across the Ohio Valley, allowing a
surface cold front to move southeast into eastern Kentucky by
Friday evening. PWATs peak at a little over 2 inches, but for a
fairly limited window, so would think that heavy rainfall would be
more isolated. Moisture and some weakness in the cap initially
will allow for some lingering POPs into Saturday, with the best
chances in the southeast.
Generally dry weather is expected on Sunday, before another cold
front slides southeast across our area on Monday, and then an
upper level trough lingers near or just to our east into Tuesday.
This will allow for slight to chance POPs across eastern Kentucky.
By the middle of next week, upper level ridging will then build
in from the west, with dry weather returning.
Temperatures will average close to seasonal normals through the
period, with less humidity expected for the second half of the
weekend and into early next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 756 PM EDT WED JUL 12 2017
Very isolated showers/thunderstorms were present over southeast
KY at TAF issuance. Outside of these, conditions were VFR with
mainly clear skies. Will expect most of the showers to die out
this evening. However, there could be be some isolated
redevelopment overnight. At this point, it`s not worth anything
more than VCSH in the TAFS. Fog will also affect the typical
valley locations overnight, but probably won`t have a big impact
at TAF sites. During the day Thursday, more in the way of
showers/thunderstorms should start to pop up in the afternoon, but
it`s still not worth more than VCTS in TAFS.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...HAL
SHORT TERM...ABE
LONG TERM...GEOGERIAN
AVIATION...HAL
Area Forecast Discussion
National Weather Service North Platte NE
708 PM CDT Wed Jul 12 2017
.Forecast...(This evening through Wednesday)
Issued at 308 PM CDT Wed Jul 12 2017
Models are kind of all over the place this afternoon so will
trend towards a solution with the stalled out frontal boundary
over the northwest Kansas into south central Nebraska as it drifts
to the north tonight and an upper level wave rounds the ridge to
the west. Storms as evidenced earlier today are efficient rain
producers with training along the front a possibility. HRRR
indicating stronger wave to begin moving through northern Kansas
into southwest Nebraska 3-4z and continuing through the early
morning hours of Thursday. Boundary begins to lift north after 6z
and upper closed low over KLBF around 12z with precipitation
moving east intop south central Nebraska. Have continued
precipitation along the Kansas Nebraska border though Thursday
night with question of where the boundary will end up but may have
to be modified with later forecasts. Highs reached early today
with MCV that developed cooling things down into the 60s and 70s.
Most areas will see a cool night with lows in the 50s and 60s and
with development of another MCV over the southwest over night
temperatures on Thursday may be in the 60s and 70s southwest
again. Have highs mostly in the 70s and 80s for highs on Thursday.
Friday upper ridge pushes north and east again with heat
gradually returning. Highs Friday in the 90s north and the upper
80s south. Highs around 90 over all of western Nebraska Saturday
and in the mid to upper 90s Sunday and dry. Monday and Tuesday
approaching 100f with chance for thunderstorms returning...mainly
north as a frontal boundary stalls out across southern South
Dakota.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 647 PM CDT Wed Jul 12 2017
Latest satellite imagery shows broken-overcast skies consisting
of predominately mid- and high-level clouds with ceilings 10 kft
or greater. Surface map shows a few clouds with lower bases,
still VFR, associated with showers as seen on radar over portions
of the Sandhills and the eastern NEB Panhandle. These showers are
expected to wane and/or move eastward out of the area through
early-mid evening. Attention turns more so to late evening and
overnight wherein showers and thunderstorms are expected to
increase in areal coverage in northeast CO and northwest/west
central KS along and in the vicinity of a weather front. Current
thinking is these showers/storms could then affect southwest NEB-
south central NEB overnight. VFR conditions are expected to
prevail nonetheless though low-end VFR (less than 7 kft) are
expected at times tonight into tomorrow morning. Threat for
showers and thunderstorms will then continue into the early
afternoon.
&&
.HYDROLOGY...
Issued at 231 PM CDT Wed Jul 12 2017
North Platte River at North Platte moved into action stage
today...bankfull...and I issued an RVS on the river. This is due
to additional releases from Lake McConaughy.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...MP
LONG TERM...MP
AVIATION...ET
HYDROLOGY...Power
Area Forecast Discussion
National Weather Service Louisville KY
923 PM EDT Wed Jul 12 2017
.Forecast Update...
Issued at 920 PM EDT Wed Jul 12 2017
The going forecast looks on track. The complex of storms over
central IN is dissipating quite quickly over the last hour, thus the
dry forecast for our area overnight looks good. A muggy airmass
will remain with not much overnight relief as lows will only drop
into the low to mid 70s.
&&
.Short Term...(This evening through Thursday night)
Issued at 245 PM EDT Wed Jul 12 2017
Afternoon visible satellite imagery shows scattered cumulus clouds
across much of central Kentucky and southern Indiana. A surface
analysis shows temperatures in the upper 80s to lower 90s and with
dewpoints in the lower 70s, heat index values so far are running 95
to 100, highest along and west of I-65. Regional radar shows some
pop-up showers and a recent RAP sounding shows some marginal surface-
based instability now that a weak mid-level capping inversion is
gone. Overall, a hot and humid summer day across the area.
In the near term, expect steady southwest winds and hot conditions
to persist through the evening. Isolated to very widely scattered
pop-up showers or thunderstorms are possible through early evening
then dry conditions are in store for the late evening and overnight
hours. Temperatures will be slow to fall and overall it`ll remain
hot until sunset. Plan on a mild and muggy overnight with lows in
the lower/middle 70s.
For Thursday, a surface front which is currently across Nebraska and
Iowa, will drop through Illinois and Indiana during the afternoon
hours. This front, aided by strong diurnal destabilization, should
be enough to initiate scattered thunderstorms during the afternoon,
mainly along and north of the I-64 corridor. The best shear is
further north across central Indiana where a slight risk looks
reasonable. Given the high amounts of instability and moisture in
place, heavy rainfall and gusty winds are the main threats. Hi-res
models show convection slowly working south into parts of central
Kentucky into the evening hours before dissipating. So overall,
better chances will be found along/north of I-64 with isolated to
widely scattered chances south. Highs will top out in the mid 80s to
around 90. Given the front`s placement over the area Thursday night,
isolated to scattered thunderstorms will remain possible though
overall coverage should diminish somewhat. It`ll be muggy with lows
in the 70s.
While areas across central Indiana have seen quite a bit of
rainfall, a couple days of drying locally should preclude any
widespread flooding concerns. One-hour flash flood guidance is
running 2 to 2.5 inches (outside of a small area of Jefferson Co, IN
which picked up over an inch yesterday) so no long fused flood
headlines or products are needed at this time.
.Long Term...(Friday through Wednesday)
Issued at 245 PM EDT Wed Jul 12 2017
On Friday, the surface front is likely to be across central Kentucky
and with peak heating by afternoon, scattered thunderstorms are
expected to develop primarily across the southern half of the
forecast area. Shear profiles remain very marginal and weak but with
the strong heating, pulse to loosely organized clusters of storms
may produce gusty winds and heavy rainfall. Convection should wane
toward evening as well as push south into Tennessee as the front
slips through.
Overall, better consensus in a dry forecast for the weekend with
slightly less humid airmass moving in thanks to upper level
troughing developing over the Great Lakes.
Another reinforcing upper shortwave may drop down in the flow on
Monday though there remains some differences in the placement and
strength between the global models. This should act nonetheless to
suppress the building ridge out west from moving east, holding back
the higher heat and humidity at least temporarily. Confidence drops
off mid-week as models continue to struggle with the placement and
strength of the upper ridge and its influence over the lower Ohio
Valley. For now, kept a model consensus which has dry weather and
near climatology temperatures.
&&
.Aviation...(00Z TAF Issuance)
Issued at 752 PM EDT Wed Jul 12 2017
VFR weather will continue overnight at all three TAF sites with a
light southwest breeze. Winds will diminish slightly after sunset.
Much of the diurnal cumulus field has scattered out this evening,
leaving mostly clear skies. A lone shower northeast of BWG will
continue slowly to the NE as it weakens over the next 30-60 minutes.
Currently, regional radar shows stronger organized thunderstorm
activity pushing slowly toward SW Indiana along the Illinois state
line. These storms will make it a bit further south over the next
couple of hours before weakening, but they are not expected to
impact SDF.
Southwest winds will increase to 8-11 kts from mid to late morning
on Thursday. As a surface boundary sinks into Illinois and Indiana
on Thursday, scattered thunderstorms will likely move into the I-64
corridor during the afternoon and evening hours. Some more isolated
to widely scattered activity will be possible by mid-afternoon
across southern KY as well, possibly impacting BWG. The storms over
southern Indiana and northern KY tomorrow are more likely to be
stronger, with localized heavy rainfall and gusty winds. Any
stronger shower or storm could result in brief IFR/MVFR conditions.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...AMS
Short Term...ZT
Long Term...ZT
Aviation...EBW
Area Forecast Discussion
National Weather Service Blacksburg VA
1010 PM EDT Wed Jul 12 2017
.SYNOPSIS...
A large Bermuda high will remain in control of our weather through the
latter portion of the week as it pumps hot and humid air into the
region, with an increasing chance for showers and thunderstorms. A cold
front will then move slowly through the region Friday and Saturday with
a good chance of thunderstorms, followed by improving conditions on
Sunday. As another front approaches from the northwest, unsettled
weather with a chance for showers and thunderstorms will return to the
Appalachians and central mid Atlantic region for the first part of next
week.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 1009 PM EDT Wednesday...Earlier widely scattered strong
thunderstorms that affected the Blue Ridge from Floyd County
south have since dissipated with instability quickly waning.
Much of the overnight looks to be dry based on the past couple
runs of the HRRR and the incoming 00z/13th NAM output. Still
looks like high clouds intrude into western counties toward
early morning, so did adjust sky cover up slightly.
What`s left is a humid, warm mid-evening. As of 10 pm
observations, middle 70s were common but sites in the Piedmont
were still in the low 80s and Roanoke at 84 degrees. Dewpoints
ranged from the mid-60s even along the Blue Ridge to the middle
70s in Southside. No doubt, it`s quite muggy outside. Little
relief anticipated to the humidity, and have unfortunately
opted to raise dewpoints up a couple degrees after midnight
using GFS LAMP guidance, as they appeared to be too low.
Mid/upper 60s to mid 70s for lows still appear on track. Good
night to have the fans or A/C units running.
Previous near-term discussion issued at 245 PM Wednesday follows...
No significant change in the synoptic pattern as a Bermuda high off the
coast remains in control of our weather and zonal flow aloft keeps the
active track of convective complexes well off to our north. Expect any
isolated cells that manage to develop from the southern Blue Ridge into
the mountains of NC to dissipate early this evening with dry conditions
overnight. Expect any late night fog formation to be primarily along
the river valleys west of the Blue Ridge. Expect an increase in chances
for showers/thunderstorms tomorrow as a weak influx of short wave
energy approaches from the south and increasing moisture generates a
bit more instability.
Temperatures tonight will remain quite warm with low/mid 70s east of
the Blue Ridge and low/mid 60s to the west. The heat stays on for
Thursday with low/mid 90s east to mid 80s/around 90 west. Heat
index values will once again top 100 east of the Ridge so stay
hydrated and take frequent breaks when outdoors.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 245 PM EDT Wednesday...
A cold front will gradually approach and then cross the area during
this portion of the forecast. Moisture will continue to pool in
advance of the front Thursday night through Friday. This and
increased dynamics aloft with the approach of the front should allow
for generous coverage of showers and storms by the afternoon on
Friday, especially across the mountains. The front is expected to
crosses the region Friday night into early Saturday morning. Its
proximity to the area on Saturday will help maintain isolated to
scattered showers and storms across primarily the southern half the
area during the day Saturday.
The latest Day 3 Convective Outlook from the Storm Prediction Center
place a Marginal risk of severe weather over the forecast area
Friday and Friday night. The greatest severe weather threat is
isolated damaging winds.
High temperatures will continue average about five degrees above
normal during this portion of the forecast with low temperatures
close to ten degrees above normal. Readings will be slightly cooler
on Saturday as compared to Friday.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 245 PM EDT Wednesday...
During this period of the forecast an upper ridge will remain parked
across Rockies and Plains States, keeping a general northwest flow
pattern across our region. Within this flow regime, a series of
upper level troughs will cross our area, each with the potential for
accompanying daily showers and storms.
By Wednesday, uncertainty grows in regards to whether or not the
upper ridge makes enough progress eastward and squelch convection
over our region, or we remain in the troughy regime. Our forecast
will lean toward the "not" side.
Temperatures during this portion of the forecast will still average
above normal, but be a couple of degrees cooler on average than the
days leading into the weekend.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
As of 724 PM EDT Wednesday...
Isolated to widely scattered thunderstorms will continue to be
observed through 01z/9pm along the central and southern Blue
Ridge mountains southwest of Roanoke into NC. While these will
not pose any threat to a TAF site, it may affect flight routes
for aircraft traveling near/along these areas. Otherwise,
looking at VFR conditions for the TAF sites through overnight
tonight. May see patchy fog develop in the Greenbrier River
affecting Lewisburg (MVFR prevailing vis but with TEMPO to LIFR
visibility), as well as in the Blue Ridge of NC and the
foothills. May see increase in VFR clouds toward overnight west
of I-77. South winds 4-6 kts becoming light (calm at times).
For Thursday, increased VFR cloudiness anticipated with
subtle upper level disturbance moving in from the west.
Sufficient enough instability for thunderstorms, and the extent
of thunderstorms should be somewhat greater - probably closer
to scattered - with storms starting as early as noon west of
Bluefield. Specific timing and impact to any particular TAF
remains unclear, so will maintain continuity with the 18z TAF
issuance and keep VCTS going for Lewisburg, Bluefield and
Blacksburg. Threat may extend slightly further east off the Blue
Ridge by mid to late afternoon, though confidence on timing
again is quite low to preclude mention attm. Potential for
erratic outflow winds, brief IFR to LIFR visibility and frequent
lightning in thunderstorms. Outside of thunderstorms, initial
light winds become west 4-6 kts.
Aviation Extended Discussion...
Any late afternoon to early evening thunderstorms diminish
and/or move eastward before midnight Thursday night. Late
night/early morning fog/low clouds are again expected Thursday
night.
Scattered to numerous MVFR showers and thunderstorms are
possible for Friday and Saturday with the passage of a cold
front. Sunday will be drier with overall VFR conditions.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...MBS
NEAR TERM...AL/MBS
SHORT TERM...DS
LONG TERM...DS
AVIATION...AL/DS