Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/31/20

Area Forecast Discussion

National Weather Service La Crosse WI

 1030 PM CDT Thu Jul 30 2020

.SHORT TERM...(This evening through Friday)
Issued at 242 PM CDT Thu Jul 30 2020

Main forecast concerns are on valley fog potential late tonight
into Friday morning.

High pressure will continue to build into the region tonight
providing dry and quiet weather, outside of the potential for valley
fog.  Mostly clear skies tonight, light winds from the surface
through 5 kft, and favorable temperature/dew point spreads late in
the night will set the stage for some valley fog. The RAP forecast
soundings show a persistent northeast wind of 10-14 kts from
around 700 ft through 2 kft, which may promote too much mixing for
valley fog in the main Mississippi River channel. We may see more
of a tributary and cranberry bog area, shallow fog event. Will
continue to monitor the wind field closely late this afternoon
into this evening. High pressure will once again dominate the
weather on Friday with dry and quiet weather expected.

.LONG TERM...(Friday night through Thursday)
Issued at 242 PM CDT Thu Jul 30 2020

As the surface high pressure system begins to depart the region,
light winds above the surface and clear skies may lead to some fog
development early Saturday morning. With uncertainty in the dewpoint
depression at this time, it is too early to determine the severity
and exact spatial coverage of this potential fog. Over the weekend,
a cold front sweeps through the region introducing shower and storm
chances from Saturday afternoon through Sunday night. A few showers
may linger into Monday morning. Currently, storms are not expected
to become well organized as low and deep layer shear are not that
impressive with up to 15 knots from 0-1 km and only around 25 knots
from 0-6 km.

Starting off the work week, a long wave trough settles in over a
large portion of the region stretching north to south from Canada
towards the Gulf of Mexico coast. Under this highly amplified
meridional flow pattern, northerly winds will advect in cooler and
dryer air into the area with afternoon high temperatures expected in
the 70s. Overnight lows look to be in the 40s to 50s. Dry conditions
are expected to last through the first half of the week. Weak
ridging builds in mid-week as the long wave trough slides off to the
east. Small shower and storm chances return Thursday as a possible
shortwave moves through the area dampening the meridional flow
pattern.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1030 PM CDT Thu Jul 30 2020

Setup overnight and into Friday looks very similar to last night.
Outside of some passing high clouds, light northerly surface flow in
place with surface ridge to the north. VFR conditions expected to
prevail but again, have to discern any valley fog potential given
such light flow and time of year.

Some valleys and bogs already at saturation late this evening so
there likely will be some fog around come daybreak Friday. Dewpoint
depression still relatively high though at KLSE and subtle hints in
model guidance that boundary layer winds may stay just strong enough
to keep fog from getting too widespread. Winds may get into the
magic light zone closer to sunrise so question is will there be
enough time for fog to impact TAF site. At this point will leave
BCFG with some channel fog but wind flow may likely keep any fog on
west end of channel, away from KLSE runways.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...Wetenkamp
LONG TERM...MP
AVIATION...Shea



Area Forecast Discussion

National Weather Service Bismarck ND

 931 PM CDT Thu Jul 30 2020

.UPDATE...
Issued at 928 PM CDT Thu Jul 30 2020

Adjusting PoPs and sky cover to better match current conditions
and trends were the most notable changes for this update. Showers
and thunderstorms have been steadily decreasing over southwest
North Dakota. To the north and east, an isolated shower or weak
thunderstorm pops up every once in awhile, but does not last for
long.

UPDATE Issued at 726 PM CDT Thu Jul 30 2020

A cluster of thunderstorms continues over west central and
southwest North Dakota early this evening, but has shown signs of
weakening over the past hour. Recent runs of the HRRR seem to have
a decent handle on these storms, and suggest continued weakening
as they drift south-southeast through the evening.

Farther north, a few isolated showers/storms have been observed.
A stronger storm near Portal and a weaker shower in McHenry County
have both since dissipated, but a new cell is now strengthening
southeast of Minot. Some model guidance has suggested a chance of
thunderstorms in north central North Dakota through the night in
association with 850 mb warm air advection, but guidance has been
trending toward a drier solution and this activity was simulated
to be more robust at this hour. So because of these trends, shower
and thunderstorm chances were removed from the forecast after
midnight.

UPDATE Issued at 452 PM CDT Thu Jul 30 2020

This update is to better align the near term forecast with current
observations and trends. Thunderstorms continue to grow in
coverage and intensity along the Highway 85 corridor from near
Watford City to the South Dakota border. Despite little to no
shear, one cell was able to briefly intensify enough to prompt a
warning. We still do not expect much, if any further severe
convection, but several storms could be strong with small hail
and gusty winds.

UPDATE Issued at 344 PM CDT Thu Jul 30 2020

Update for some widely scattered late afternoon thunderstorms
west.

&&

.SHORT TERM...(This evening through Friday)
Issued at 231 PM CDT Thu Jul 30 2020

Features in the short term include a trough of low pressure and
associated cold front across northeast Montana into Saskatchewan.
A warm front extended from this low through central North Dakota.

For tonight, the cold front will slowly move into northwest North
Dakota this evening, then into central ND on Friday. The front
will be the focus for scattered thunderstorms.

However, there is uncertainty in the timing and extent of the
convection this afternoon and tonight. Shear continues to be very
weak, so thunderstorms are not expected to be organized or
sustained for very long.

We expect convection initially across southwest North Dakota this
afternoon, then possible forming into the central and east
central as the front moves into the picture. However CAM models
are of little help here as they are not consistent, so we Kept
POPs pretty low through tonight.

On Friday, we expect some convection across teh south and east
along the front as it moves east.

.LONG TERM...(Friday night through Thursday)
Issued at 231 PM CDT Thu Jul 30 2020

Scattered showers and thunderstorms will linger along the front
as it continues to move east out of the region. Then the weekend
will be pleasantly cool and dry across the region in the wake of
the cold front.

Dry weather is expected through Tuesday. Then Wednesday and
Thursday will be active again as a shortwave trough moves through
the region. However widespread precipitation is still not
expected.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 726 PM CDT Thu Jul 30 2020

Scattered thunderstorms will continue near KDIK until around
02/03z. A brief period of MVFR visibility and gusty winds may
occur. An isolated storm has recently developed southeast of KMOT,
but is not expected to track toward the airport. Otherwise, VFR
conditions are expected through the forecast period. Scattered
thunderstorms may redevelop by Friday afternoon as a cold front
moves from northwest to southeast across the area. The greatest
coverage of storms is expected near KJMS, so have introduced a
VCTS mention there for late Friday afternoon. There is too much
uncertainty elsewhere for VCTS at this time. Behind the front,
winds will turn northerly around 10-15 kts.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Hollan
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...Hollan




Area Forecast Discussion

National Weather Service Caribou ME

 953 PM EDT Thu Jul 30 2020

.SYNOPSIS...
A trough of low pressure will slowly move across the north through
Friday. High pressure will build in from the west on Saturday, crest
over the area Saturday night then move east on Sunday. Low pressure
will approach Sunday night and lift north of the area Monday. A cold
front will cross the region early Tuesday.

&&

.NEAR TERM /THROUGH FRIDAY/...
955 pm update...
Showers contg acrs the region tonight as s/wvs rotate arnd base
of upr low spinning north of the St. Lawrence. Plenty of low-
lvl moisture exists acrs most of the region with showers off and
on thru the ovrngt. Quick update to add patchy/areas of fog to
the region where showers occurred this evng. No other chgs
needed with this update.

Prev discussion blo...
Convection will rapidly diminish later this evening, with a
stray lingering shower possible across far northern Maine
overnight as the center of the upper level low clips the area.
The upper low will move into the Gulf of Saint Lawrence by
Friday, shifting flow out of the northwest. There is
considerable uncertainty regarding convection chances for
Friday, with the 12z NAM and HRRR showing a weaker to non-
existent capping inversion and the GFS showing a stronger cap
that significantly limits convective coverage. PoPs were reduced
and lightning was capped at isolated. Temperatures will be
similar or slightly cooler than today, with highs in the mid to
upper 70s across the north and low to mid 80s across the south.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
A trough of low pressure north of the area will slowly slide off to
the northeast Friday night as weak ridging and high pressure begin
to move in from the west. A stray thundershower may be around early
Friday evening. Otherwise, Friday night should turn out partly
cloudy. Weak surface high pressure will build over the area Saturday
as upper level ridging pushes in from the west. However, there are
some indications that a subtle shortwave dropping down the back side
of the old departing trough may slide across northeastern parts of
our area Saturday. This may be enough to spawn a thundershower or
two, mainly over the north and northeast. Otherwise, Saturday will
be sunny to partly cloudy and warm. High pressure will crest over
the area Saturday night bringing a mostly clear and calm night which
may allow some patchy valley fog to form. Our focus on Sunday then
turns to a trough lifting out of the Ohio Valley and approaching on
Sunday. Clouds will increase and some showers are possible late
Sunday, especially in the west, as the trough and low pressure
approach.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
An upper trough will lift up to our northwest Sunday night as a
surface occlusion pushes into our region. Some difluence aloft
between the approaching trough and a subtropical high supported in
part by tropical system Isaias may enhance lift and shower activity.
The showers and isolated thunderstorms will continue into Monday and
possibly Monday night as the front slowly presses across our area. A
cold front will press south of the area Tuesday followed by some
cooler air being pulled in from beneath an upper trough in Quebec.
Subsidence behind this trough as it slides east combined with
surface high pressure should then bring a couple dry days Wednesday
into Thursday with some cumulus clouds Wednesday as the upper trough
pivots across. Thursday should turn out mostly sunny with the high
building over. Meanwhile, some of the long range forecast models
are bringing tropical storm Isaias near Maine during the mid-
week period next week. Forecast tracks range from just south of
the Gulf of Maine on the GFS to across southern Maine on the
ECMWF. The most inland tracks seem to be favored by guidance
solutions that show a deepening trough digging well to the west
and pulling the storm north. Track and intensity forecasts will
likely take a few days to refine but interests along the coast
should closely monitor forecast updates through the weekend and
into early next week.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
NEAR TERM: VFR this evening will give way to MVFR twd daybreak.
May see IFR clds at FVE twd 08z but only confident enuf to
include SCT at this time. VFR for HUL and BGR with IFR
restrictions at BHB btwn 08z-11z Fri. All terminals likely to be
VFR in the afternoon.

SHORT TERM:
Friday night: MVFR to VFR north, VFR Downeast. N wind

Saturday: VFR. Light NW wind.

Saturday night: VFR, except locally IFR in patchy fog late. Calm
air.

Sunday: Chance of fog early. Otherwise, VFR. Light SW wind.

Sunday night: Sunday night. MVFR, becoming IFR. S wind.

Monday: IFR to MVFR. S wind becoming W.

Monday night: IFR to MVFR then becoming VFR late. W wind

Tuesday: VFR. Gusty W wind.

&&

.MARINE...
NEAR TERM: Winds and seas will remain below SCA levels through
Friday.

SHORT TERM:
Winds and seas are expected to remain below SCA through the
middle of next week with the possible exception of a few gusts
to 25 kt over the offshore waters early Monday and swell from
tropical storm Isaias early next week. Humid air over the waters
will result in some fog through Monday. A cold front pushing
offshore Tuesday will then bring improved visibility Tuesday
through mid and late week as drier air follows the front. The
future track of tropical storm Isaias remains uncertain but
marine interests should follow tropical forecasts given the
possibility that it may affect our weather or raise seas next
week if the system tracks nearby.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.

&&

$$

Near Term...Farrar/MStrauser
Short Term...Bloomer
Long Term...Bloomer
Aviation...Farrar/MStrauser/Bloomer
Marine...Farrar/MStrauser/Bloomer




Area Forecast Discussion

National Weather Service Louisville KY

 926 PM EDT Thu Jul 30 2020

.Forecast Update...
Issued at 926 PM EDT Thu Jul 30 2020

Showers and a few thunderstorms continue to move through the
forecast area this evening.  First area of convection stretches from
near Louisville eastward to Lexington.  This activity has been
showing signs of weakening, but is still producing pockets of
torrential rainfall.  This activity is forecast to drop east-
southeast and should continue to weaken as instability is decreasing
with the loss of heating.

Second area of stronger convection continues to move eastward
through south-central Kentucky.  This activity will move through
portions of Casey/Lincoln counties over the next hour.  SPC
mesoanalysis has a bit higher MLCAPE down this way as this area
hadn`t seen much convection today.  The storms are sub-severe and
will produce torrential rainfall, gusty winds to 40 MPH, and
frequent lightning.  Some localized flooding is possible, but the
threat appears to be muted given the progressive movement of the
storms.

Finally, a third area of convection developed earlier over SW IN.
This activity is pushing through Henderson/Owensboro and should
continue east-southeast.  This activity looks to affect area from
Beaver Dam over to areas just south of E-town over the next 1-2
hours.  Main threats here will be heavy rainfall and some gusty
winds here and there, along with some lightning.

For the overnight period, latest HRRR runs suggest that convection
will continue to diminish overnight with the loss of heating.
Outflow from ongoing convection may spark some additional showers
and storms across southern KY overnight.  For now, have kept likely
PoPs going through about 31/06Z and then will taper them down to
around 30% by dawn.  Given the high moisture content and potential
for some localized flooding, will go ahead and let Flash Flood Watch
continue into the overnight period.

Issued at 757 PM EDT Thu Jul 30 2020

An interesting evening thus far here in the Ohio Valley.  Persistent
band of convection has been steadily working eastward across
southern Indiana with some more isolated convection firing off to
the south of it.  Shear profiles on model proximity soundings are not
all that exciting, but we do have enough speed and directional shear
in the environment to produce some pockets of rotation with the cells
moving through.  Several, including one that passed right over the
office have exhibited supercellular characteristics in terms of radar
presentation.  Lightning hasn`t been all that common with the
storms, more likely due to the deep, moist adiabatic profiles seen
in the model proximity soundings.  Overall the soundings are very
tropical in nature, indicative of heavy rainfall.

Radar mosaic suggests that we have an MCV that is pushing through
southern IL this evening.  This is forcing the ongoing convection
across the region.  The back edge of it is now entering our western
CWA.  Based on current radar trends, current thinking is that main
convective threat will be along and just south of the I-64 corridor
for the next several hours.  Showers with very heavy rainfall, with
some embedded thunderstorms are expected. Main threat looks to be
the heavy rainfall creating ponding on roads, and localized flooding
in some areas.  The flooding threat may be tempered a bit given the
progressive motion of the storms, but we`ll have to watch for areas
of training. Winds are not all that strong near the surface, but
gusts to 25-30 MPH can`t be ruled out.

A secondary batch of convection down around Munfordville south to
Glasgow is forecast to move eastward across south-central KY. Again,
nothing severe is expected with this activity, but torrential
downpours, a few pockets of gusty winds, and some lightning can be
expected.

&&

.Short Term...(This evening through Friday)
Issued at 323 PM EDT Thu Jul 30 2020

The Lower Ohio Valley sits under the western side of an upper trough
with a embedded shortwave. Ahead and to the southeast of the
shortwave, a surface low sits along a front stretched to the east
following the Ohio River. These features together are taking
advantage of precipitable water values between 2.2 and 2.3". The
result has been heavy rainfall today with rates over 4" per hour and
measured precip near 3" with 2.91" measured in Oldham County by the
KY Mesonet. Other counties in southern Indiana have also received
over 2". It`s a good thing the region has been fairly dry recently.
It has allowed the ground to soak up much of this rainfall.

Tonight, the current set-up remains mostly stationary, and the fear
is heavy rain will begin following the stationary front. That would
require asking already saturated ground to hold more rainfall from
possible training heavy rainers. Some CAMs currently show this set
up happening across southern Indiana and along the Ohio River, and
it`s with that worry that we issued a Flash Flood Watch through
tomorrow morning. WPC keeps the area in a Slight risk for Excessive
Rainfall.

Tomorrow, the low moves south, down the Mississippi River Valley.
This pushes the front and moisture southward. Rain chances drop in
the north and push south. This gives relief to the areas that
received all the rainfall today in southern Indiana and north-
central Kentucky. During the afternoon and evening hours, the area
may even see some sunshine. Highs will be in the comfortable low
80s.

.Long Term...(Friday night through Thursday)
Issued at 152 PM EDT Thu Jul 30 2020

By Saturday morning low pressure will be centered over the Pennyrile
and will head northeast up the Ohio River over the course of the
day, into Ohio by Sunday morning. Confidence is not as high as it
might normally be due to disagreements among the model data, however
this solution is close to a consensus of the most recent input. On
Saturday afternoon it appears that the best instability and deep
layer shear will be east of Interstate 65, with weak mid-level lapse
rates. DCAPE looks weak and low level lapse rates are not
impressive. Nevertheless, with there will be plenty of instability
and deep moisture for thunderstorm development as a 5H speed max
moves into the Tennessee Valley by late afternoon coincident with a
low level jet spreading from middle Tennessee into the eastern half
of Kentucky. A few strong to severe storms will still be possible
with locally gusty winds and small hail if the current forecast pans
out. Stay tuned.

Sunday the low and its trailing cold front will pull away to the
northeast. We could still see some spotty convection ahead of an
upper trough reaching from the Davis Strait to the northwestern Gulf
of Mexico, but the bottom line is that Sunday should be the drier of
the two weekend days.

Monday-Tuesday another cool front will cross the area beneath the
aforementioned upper trough. Precipitable water values will be
relatively low (compared to what we have been seeing) in fairly weak
flow. Scattered thunderstorms will still be possible in weak to
moderate shear.

Wednesday and Thursday surface high pressure will build into the
Great Lakes and Saint Lawrence Valley with a weak upper trough tying
to hang on overhead. These two days look like the driest of the 7-
day forecast period. The best chance for any isolated thunderstorms
will be in southern Kentucky, farthest away from the dry air
associated with the high to our north.

&&

.Aviation...(00Z TAF Issuance)
Issued at 743 PM EDT Thu Jul 30 2020

Expect showers and thunderstorms to continue moving west to east
along a surface boundary, roughly along the OH River through later
this evening. Once convection dissipates, CIGs will likely lower to
MVFR and then down to IFR by early Friday morning. CIGs will be slow
to improve, but expect to see MVFR by late morning to early
afternoon with another chance of afternoon showers and
thunderstorms. Outside of convection, winds will be light from the
SW before going light and variable overnight and into Friday.


&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Flash Flood Watch until 8 AM EDT /7 AM CDT/ Friday for
     INZ076>079-083-084-089>092.

KY...Flash Flood Watch until 8 AM EDT /7 AM CDT/ Friday for
     KYZ023>043-045>049-053>057-061>067-070-071.

&&

$$

Update.......MJ
Short Term...KDW
Long Term....13
Aviation.....CG



Area Forecast Discussion

National Weather Service Memphis TN

 828 PM CDT Thu Jul 30 2020

.UPDATE...Evening Update.

&&

.DISCUSSION...

Adjusted pops bases on radar trends and latest HRRR. Earlier the
HRRR proved to be way too aggressive with the late
afternoon/evening convection but seems to have a better handle on
what is happening now and what is upstream on radar. Our next
round of showers and thunderstorms should arrive 1-2 am and shift
into Middle TN/Alabama around sunrise. SPC has pulled the Slight
risk to a small portion of east Central Arkansas, with a marginal
risk for the remainder of the Midsouth. Damaging wind is the
primary threat.

30

&&

.PREV DISCUSSION... /issued 637 PM CDT Thu Jul 30 2020/

DISCUSSION...Surface analysis this afternoon places a quasi-
stationary boundary from the Ohio Valley west back along the I-70
corridor in Missouri then back through Oklahoma and into the Texas
Panhandle. Meanwhile, showers and thunderstorms occurring over
Eastern Oklahoma and Western Arkansas are associated with another
shortwave embedded within the mid-level trough axis. KNQA WSR-88D
radar trends haven`t shown much convective activity occurring
across the Mid-South due to morning cloud cover. This is likely
due to relatively weak shear aloft with the predominant forcing
mechanism this afternoon being convective temperatures being
reached this afternoon. As of 2 PM CDT, temperatures across the
Mid-South are in the middle to upper 80s across most locations.

Short term models and CAM solutions have struggled in the short
term to handle convective trends for this afternoon. Nonetheless,
models still suggest showers and thunderstorms developing tonight
as another shortwave trough rotates around the mid-level trough
and into the Lower Mississippi Valley. The aforementioned quasi-
stationary boundary is expected to drop south into the region into
Friday. This mid-level trough and associated front will slowly
move through the Lower Mississippi Valley through Saturday night.

Strong instability will exist over the next couple of days with
perhaps some marginal shear available to result in perhaps some
multicellular organization. Damaging winds will be the main threat
if any thunderstorms can reach severe limits especially during the
afternoon/evening hours each day. Precipitable water values remain
quite high at or above 2 inches for late July/early August. Latest
QPF guidance has trended lower with total rainfall amounts
through Saturday night ranging from 1.5 to 3 inches predominantly
along and north of I-40. Regardless, thunderstorms that are slow
moving will have the potential to be efficient in producing localized
heavy rainfall.

Long term models indicate a broad upper level trough axis will
remain in place across the region through much of next week with
temperatures anticipated to average slightly below normal for
early August with shower and thunderstorm chances occurring mostly
during the afternoon and early evening hours nearly every day.

CJC

&&

.AVIATION...
00Z TAF

Isolated showers and thunderstorms across the area. Models
indicate numerous showers and thunderstorms moving into the area
overnight. With that being said, MVFR conditions can be expected
in any showers and storms. VFR conditions otherwise. SSW winds
8-12kts but some gusty conditions cannot be ruled out. Gusts
typically 16-20kts.

SMW

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&

$$



Area Forecast Discussion

National Weather Service New York NY

 1038 PM EDT Thu Jul 30 2020

.SYNOPSIS...
A cold front will slowly move south of the region overnight, and
become nearly stationary on Friday. The front will eventually
push well out of the local coastal ocean waters Friday afternoon
into Friday night. Weak high pressure will build in from the
north and west for Friday night. A warm front will pass thru the
region during the second half of the weekend. Tropical impacts
from Isaias may be possible next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
With precipitation to the north and a few showers moving into
northwestern New Jersey at 0130Z, and hi res models indicating
little development then next few hours, updated probabilities
into late tonight. Also, temperatures and dew points across much
of the region were running higher than forecast, so these were
updated as well.

Two main features are the cold front and then the wave of low
pressure along the cold front. These two features will provide
the focus for convergence and lift for showers and thunderstorms
across the region. There will be more instability tonight than
there will be Friday morning. Aloft, there will be periodic
shortwaves and associated PVA that will further enhance lift.

The cold front will move across the region tngt from north to
south, moving into the ocean waters overnight.

Chances for shwrs and tstms invof the front tngt. There could be
an embedded svr due to extra helicity near the boundary.

The wave of low pressure Friday along the front south of the
region will be moving into an environment that will have
easterly shallow boundary layer flow and southwest flow in the
mid levels. High precipitable waters up to 2 inches are
forecast. This will create a situation where convection develops
and expands and backbuilds, prolonging potential heavier rain.
This will make for a chance of flooding. See hydro section.
While convection will not be as organized, it is expected to be
more widespread across Northeast NJ, Southern parts of the Lower
Hudson Valley, New York City, Southwest Connecticut and into
Long Island.

Temperatures will remain mild tonight with lows only in the upper
60s to lower 70s.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Second round of convection expected to be ongoing and continue
until around 9-10 AM Friday morning. Mainly HRRR and NAM Nest
used for convective POPs. The cold front will be moving slowly
south of Long Island. Aloft, another shortwave with associated PVA
ahead of it will be moving through.

The instability will be more across the ocean for Friday. Coastal
areas could have some elevated instability early. Widespread
convection early with flood potential. Again, see hydrology
section for more details.

During Friday afternoon, most convection will be moving out of the
ocean waters south of Long Island. Mainly dry conditions are
expected by mid to late afternoon. The low level easterly flow will
keep some moisture trapped under an inversion. Coastal areas will
see an abundance of clouds with more breaks in the clouds across the
interior. Cooler temperatures are expected with highs only
reaching the upper 70s to near 80. Any lower 80s highs are
expected for far interior locations.

For Friday night, dry conditions are forecast as well as a gradual
decrease in clouds. This will be as high pressure briefly builds
in from the north and west. There is mid level confluence
indicated in the forecast models that will help with subsidence.
Lows Friday night were from a consensus as well as national blend
of models with values in the low 60s to low 70s. Lower end of the
range is in the interior while upper end of the range is within
NYC.

A moderate risk of rip currents is forecast for Atlantic Ocean
beaches on Friday.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
High pres on Sat will give way to an approaching warm front for
the 2nd half of the weekend. Shwrs and tstms have been fcst,
with the NBM used for pops but limited to chance. Additional
chances for shwrs and tstms on Mon with sw flow aloft. Primary
threat will be across the interior. The NBM was used for pops,
but these may need to trended down along the coasts due to the
flow regime. The only reason that the higher pops were
maintained attm was due to the potential for any tropical
moisture ahead of Isaias.

Main impacts from Isaias right now appear to be in the Tue/Wed time
period. Please refer to the latest forecast from the National
Hurricane Center on the system. It`s much too early to provide any
specific details with the track and intensity uncertain, but the
storm should be closely monitored.

The tropical system or remnants should be exiting on Thu. An
approaching upr trof could produce some additional shwrs and tstms,
but there is the suggestion of some mid lvl dry air advection. As a
result, the fcst was left dry.

Temps thru the extended based on the NBM.

A moderate risk of rip currents is forecast for Atlantic Ocean
beaches on Saturday.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
At 0230Z a cold front was moving through Long Island and will
push south overnight, then stall. The front remains south of
the terminals through the remainder of the forecast.

VFR through the overnight with local MVFR possible in
thunderstorms after 06Z, especially at the NYC metro terminals
and east. MVFR ceilings likely Friday until late in the forecast
period, except remaining VFR at KSWF.

Low confidence and high uncertainty with the wind forecast
through tonight, and wind directions will depend on the movement
of the cold front. A light, less than 10 kt, north to northeast
flow develops Friday.

.OUTLOOK FOR 00Z SATURDAY THROUGH TUESDAY...
.Friday night and Saturday...VFR.
.Sunday through Tuesday...A chance of showers and thunderstorms
with local MVFR.

&&

.MARINE...
With little precipitation across the waters, and little expected
until late tonight, have updated the probabilities for showers
and thunderstorms. Otherwise no changes were made.

The short term forecast period through Friday night is expected
to remain below small craft advisory criteria with a relatively
weak pressure gradient in place.

Ocean seas will stay in the 3 to 4 ft range with wind gusts for
parts of the ocean up to 20 kt into early this evening. Otherwise,
winds will stay mainly around 5-10 kts without much of any
gusts.

Winds and seas will likely remain blw sca lvls over the
weekend, then seas will increase on the ocean to aoa 5 ft by Sun
ngt into Mon. Impacts from Isaias are possible by Tue/Wed.

&&

.HYDROLOGY...
A combination of factors will be in place late tonight into Friday
morning, low level easterly flow to enhance convergence, high
precipitable waters up to near 2 inches, and elevated instability to
allow for expansion and backbuilding convection with heavy rain. The
potential will be there for minor flooding with flash flooding for
some locations possible, especially in poor drainage and low
lying areas. Mentioned in HWO for this possibility.

Some localized minor flooding possible with any tstms on Sun. With
the influence of tropical moisture into the region next week,
localized flash flooding will become a concern. Additionally, the
track of Isaias will need to be monitored.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides will be rising during the next several days with
the forecast of a full moon on Monday, August 3. There is a low
probability of touching or exceeding minor flood thresholds along
the most vulnerable locales of the south shore bays of LI, and SW CT
during the late afternoon/early evening high tide cycles
Thursday and Friday. The higher chance of exceeding minor
benchmarks will be over the weekend.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is
undergoing its final stages of testing, and is operating at full
power.

Riverhead NY NOAA Weather Radio Station WXM-80 (162.475 MHz) is
experiencing intermittent service.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$
SYNOPSIS...JMC/JM
NEAR TERM...MET
SHORT TERM...JM
LONG TERM...JMC
AVIATION...MET
MARINE...JMC/JM/MET
HYDROLOGY...JMC/JM
TIDES/COASTAL FLOODING...
EQUIPMENT...




Area Forecast Discussion

National Weather Service Blacksburg VA

 1028 PM EDT Thu Jul 30 2020

.SYNOPSIS...
Unsettled conditions are expected to continue into the weekend
as a front remains stalled across the region and troughing
dominates the eastern U.S. Daily chances of rain and
thunderstorms are expected.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 1015 PM EDT Thursday...

00Z Blacksburg sounding saturated from surface to 200mb, with
PWAT close to 2 inches, which explains the heavy downpours and
localized flooding we had this evening across a few areas over
the mountains.

Late this evening, a meso-low was moving across the Roanoke
Valley indicated by a swirl on radar. We are seeing a lull
behind this main batch of rain across the mountains, with
showers well upstream across KY. These are expected to reach the
mountains of WV after 1-2am, though not as concentrated as
earlier, and should be a little bit weaker in
intensity/rainfall.

The batch out east should exit by around midnight-1am.

Otherwise, not seeing many change to the forecast tonight.
Patchy fog appears likely but given extent of clouds will not
see a lot of coverage.

Previous discussion from early evening...


Forecast updated to reflect less thunderstorms but more moderate
to heavier showers mainly along/west of the Blue Ridge this
evening, as weak low moves along the front, though should start
to see transition further east toward more coverage as better
moisture convergence edges that way.

Still have not seen a consistent enough coverage of heavier
downpours to opt for a flood/flash flood watch, as it is mainly
isolate downpours, but have had some training leading to minor
or poor drainage flooding, especially in Rich Creek, VA and
portions of Tazewell County, VA.

High-res model showing a drier lull in precip overnight west,
before another wave approaches toward dawn, with another round
of showers.

Previous discussion from early this afternoon...

Already starting to see some shower and thunderstorm development
this afternoon. Most of this activity has been along the Blue Ridge
and west. Will continue to see an uptick in the coverage of this as
the afternoon evening progresses. Low-level moisture with dew points
in the upper 60s and lower 70s, plus plenty of clearing from this
morning has allowed for increased instability across the area. RAP
analysis indicating MLCAPE values in the 1000 to 1500 j/kg range
already. With this instability already in place and as the upper-
level impulse over Kentucky continues to move east, will really
begin to see an increase of storm coverage progressing into the
evening.

We have also seen an increase in deep southerly advection this
afternoon ahead of the feature over Kentucky, in response to this,
PWATs have also been surging upward. Morning sounding at
Blacksburg this morning indicated PWAT value around 1.3", but we
have since surged to 1.7" to 1.8" over a big portion of the
CWA. This will be more than enough for storms to be very
efficient rainfall producers. With this said, there is some
concern of localized flooding, especially in areas that may see
training of storms over the same location. Fortunately,
antecedent conditions are favoring against any widespread flash
flooding threat this evening. Secondary threat this afternoon
will be severe storms producing damaging winds/wet downbursts,
especially within areas of cell mergers/cell clusters. For this
risk, the entire CWA has been highlighted with a Marginal Risk.
Overall the best threat for heavy rain for this evening and
tonight should be in the western parts of the CWA, particularly
northwest NC mountains, southwest VA mountains, and southeast WV
mountains, where FFG values are lowest and convection will
arrive with favorable timing and intensity. Less is expected
further east with time.

Friday, stationary boundary still remains in place across the
northern portions of the CWA. With abundant moisture stuck over the
region (i.e., dewpoints in the mid 60s mountains to mid 70s
Piedmont) combining with strong diurnal heating, the front, and good
upper-level support, expect renewed scattered showers and
thunderstorms again by mid-day Friday.

Fairly decent spread in temperatures this afternoon, but this
is a product of ongoing rain/cloud cover in the west. So will
see highs in the upper 70s, low 80s for areas west of the Blue
Ridge. Less clouds and storms in the Piedmont will allow for
upper 80s and lower 90s. Morning lows will be muggy once again
with dewpoints as high as they are (e.g., 60s & 70s). Lows will
range from the mid 60s in the mountains to the lower and even a
few mid 70s in the lower elevations of the Piedmont. Friday,
with lingering clouds and possibility of another round of rain
and storms, keeping most areas under 90. Upper 70s/low 80s for
the mountains, mid to upper 80s in the lower elevations east of
the Blue Ridge.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 1250 PM EDT Thursday...

During this portion of the forecast a ridge of high pressure over
the southeastern U.S. will be encroached from the west by a slow
moving shortwave trough. While we will be concerned with the
potential for daily chances of showers and storms, the focus for the
best coverage will be along our western areas as moisture
trajectories will maximize from the southwest between the interface
between these two systems. It is this same region we will need to
monitor for potential heavy rain also. As we progress further into
the weekend, the approaching shortwave trough is expected to shift
northeast into the Great Lakes region. This will take the focus for
the better coverage north of the area. However, our region will
maintain the potential for additional showers and storms as we
continue within a typical summertime airmass.

During this portion of the forecast high temperatures will average a
couple of degrees below normal, and lows will average around five
degrees above normal.

Confidence in the above scenario is moderate to high.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 130 PM EDT Thursday...

The big story in the extended forecast looks to be widespread
tropical moisture especially Monday and Tuesday as Tropical Storm
Isaias works up coast toward the Carolinas. At the same time we have
an upper level trough and frontal boundary to the north and west
suppressing this moisture overhead. Overall timing and location of
heavy rainfall will depend on the track of Isaias and placement of
the front with the adjacent trough in the coming days ahead.

Both the GFS and Euro agree on a wet period for Monday and Tuesday
as moisture from what is now Tropical Storm Isaias is drawn in. The
GFS though is a bit faster with the tropical system but slower when
it comes to pulling the trough through. The GFS also brings in a few
more waves of energy around the base of the trough ad strengthening
high Tuesday into Wednesday. The Euro on the other hand is a bit
slower on Isaias with a draw up the coast through the Outer Banks
Tuesday into Wednesday before pushing into the Delmarva and out to
sea midweek. This would keep rain chances on the high side of things
especially during the afternoon and evening hours Monday through
Wednesday.

Both models hint at a front by the Thursday timeframe as high
pressure asserts itself over the Ohio River Valley and slides east
into West Virginia later this week. Precipitation will likely drop
off beyond this period with a hit at a drier and seasonable weekend
ahead.

Temperatures during the extended period look to remain at or
slightly below average. Highs will be in the mid to upper 80s east
of the Blue Ridge and upper 70s to low 80s out over the mountains.
This is in trend with bot the Climate Prediction Center`s 6 to 10
day and 8 to 14 day outlooks. Things look to heat up again behind
the front as precipitation chances drop with high pressure later in
the week.

Confidence in precipitation chances remains moderate to high while
temperatures remain moderate through the period.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
As of 730 PM EDT Thursday...

Showers/embedded thunder will impact most taf sites this
evening, with most concentrated from ROA/LYH west over the
mountains. Will likely see cigs/vsbys MVFR or lower through the
night, as moisture increases. Some below 1kft cigs likely
especially along/west of ROA/BCB.

Patchy fog is expected again tonight, but cloud cover will
dictate how low vsbys drop. Not confident enough to have
LIFR/VLIFR so raised vsbys at LWB.

Friday will be almost a repeat of today with showers and few
thunderstorms, though appears along and north of a BLF-LYH line
has the best coverage. For now will go with VCTS at best, with
most sites becoming VFR by midday.

Extended Aviation Discussion...

Low pressure aloft deepening across the eastern U.S. and a
stalled frontal boundary in/near the region will keep an
unsettled pattern in place through much of next week. This will
result in daily rounds of afternoon/evening showers/thunderstorms
and abundant low clouds, fog, and even some rain showers at
night. Certainly not the best period for aviation overall.
Several periods of sub-VFR conditions are likely.

&&

.CLIMATE...
As of 730 PM EDT Thursday...

The streak of 90+ degree highs for Roanoke ended today, as it
got to 89. Showers moved into the area curtailing the
temperature reaching 90.

Through the 29th, ROA still maintaining position as 2nd warmest
month on record at 81.8F after August 2007 at 82.1F. Could be a
photo finish on the last day given warm forecast but likely
falls just short of the record. Warmest July is inevitable
however, with previous record a full 1.0F lower at 80.8F in July
2012.

Lynchburg currently on track for 3rd warmest month on record at
81.2F and very close to 2nd place which was 81.3F way back in
August 1900. With a forecast high of 92 at LYH today, still time
to come closer to the 2nd place record.

Not only has it been hot but very dry in some places. Bluefield, WV
currently sitting at 3rd driest July on record with 1.68 inches
through the 29th, after picking up 0.54 Tuesday. Blacksburg NWS
office still holding at 2nd driest July at 1.29 inches, behind
only the 0.93 inches in the midst of the Great Drought of 1930.

However, unlike the temperature records, which are likely to
hold, the precipitation records may fall with substantial
rainfall predicted for many locations today and tomorrow the
31st.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.

&&

$$
SYNOPSIS...BMG
NEAR TERM...BMG/WP
SHORT TERM...DS
LONG TERM...ET
AVIATION...BMG/RAB/WP
CLIMATE...PC/RAB/WP