Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/29/17
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
848 PM CDT Mon Aug 28 2017
Issued at 847 PM CDT Mon Aug 28 2017
Skies will remain clear through the night with light winds.
Current forecast looks good.
UPDATE Issued at 659 PM CDT Mon Aug 28 2017
00z aviation discussion updated below.
.SHORT TERM...(This Evening through Tuesday Afternoon)
Issued at 317 PM CDT Mon Aug 28 2017
Winds today ended up being stronger than forecast across central SD,
so have been adjusting wind grids towards the latest HRRR runs which
have been doing a good job capturing the higher winds. These winds
will subside after sunset as we head towards continued clear skies
overnight with a light southerly breeze. Once again lowered ABR
cooler than guidance as winds will likely drop to around 5 knots or
less towards sunrise.
Very similar air mass over the region on Tuesday, so will likely see
temperatures much like today as we continue to see mostly sunny
skies. Expect highs to rise into the 80s once again, with parts of
central SD flirting with 90 degrees.
.LONG TERM...(Tuesday Evening through Monday)
Issued at 317 PM CDT Mon Aug 28 2017
The upper flow will be dominated by a 4 corners high, with an
eastern CONUS trough and thus mainly northwest flow aloft. There is
a subtle ridge axis overhead so subsidence can be expected for most
of the extended. There is a brief period where an upper trough
passes across the northern tier of the CONUS that will briefly
suppress the ridge, resulting in a short period with a chance for
precipitation. Wind flow aloft is weak, but the GFS supports a 30-
40kt low level jet with the mid level trough passage mainly
overnight into early Friday - so mainly overnight convection. The
stronger low level flow will also be responsible for windy
conditions Thursday into Friday. A second, northwest flow wave will
follow, but at this time it appears to move overhead Friday night,
effectively dislodging some cooler air with stronger northerly winds
for Saturday. Another wave, this one in central Canada, will be too
far away to bring moisture to the area, but it will result in an area
of warm advection that looks to move in Sunday - too far out to
significantly deviate from extended blended guidance but something
to watch as it comes closer to fruition.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 659 PM CDT Mon Aug 28 2017
VFR conditions are expected through tonight and Tuesday at all
Area Forecast Discussion
National Weather Service Cleveland OH
1014 PM EDT Mon Aug 28 2017
Low pressure over the Midwest will slowly move east across the Ohio
Valley through Wednesday. A second trough will pull a cold front
south across the area as it moves across the Eastern Great Lakes on
Thursday. High pressure will move south out of Canada behind the
front on Friday, shifting to the east coast on Saturday.
.NEAR TERM /THROUGH TUESDAY NIGHT/...
Minor updates to pops/sky cover, but no major changes to the
forecast with the late evening update. Shower activity continues
across the western part of the forecast area. HRRR has done a
fairly good job with this setup, and continues to indicate
isolated/scattered showers translating eastward into NE OH
overnight as upper jet streak across the Ohio valley moves
east/northeast. Expanded some slight chance pops eastward
through the night. Otherwise, thunder potential is quickly
coming to an end with the atmosphere stabilizing across the
There is little change to the forecast through Tuesday night.
Upper closed low moves little, fills and opens Tuesday into
Wednesday. The pattern is essentially on hold with no upstream
kick and waiting for low pressure/potential tropical storm to
move up the east coast over the next couple of days. So scenario
will be similar tonight and Tuesday with the bulk of the
shower/scattered thunderstorm activity taking place west of a
Cleveland to Wooster line and never really progressing east.
Will keep 20 PoPs in for Tuesday night for any lingering shower
with trough axis overhead. Will go with similar temperatures for
tomorrow, lower and mid 70s. Upper 50s/lower 60s both nights.
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
The area is between systems on Wednesday but increasing warm
advection ahead of a cold front may produce a few
showers/thunderstorms. The chances of thunder will increase
ahead of the front, especially across the eastern half of the
County Warning Area. The amount of moisture available to lift is
in question so the coverage is uncertain. By Friday high
pressure will build across the region with dry conditions
Wednesday should be the warm day of the short term with highs in the
middle to upper 70s. Cooler thursday into Friday with highs mid 60s
to mid 70s.
.LONG TERM /FRIDAY THROUGH MONDAY/...
The long term begins Friday night with both the ECMWF and the GFS
showing high pressure over the central and eastern Great Lakes while
remnants of Harvey move slowly northeast through the Mississippi
valley. Dry air will be in place across the region however deep
moisture will be approaching from the ssw. By Saturday morning the
GFS has the surface low over northern AR/srn MO while the ECMWF low
is in western KY. Manual progs split the difference with the low on
the AR/TN border. Both models agree however that moisture moves
north in the area during the day Saturday as the surface high drifts
to New England. Deep moisture remains into early Sunday before weak
high pressure and drier air move in for the afternoon. Will have
chance pops moving into the area from the south Friday night with
chance to likely pops most areas Saturday. Highest pops again south
of a Marion to Canton line. Will continue with chance pops Saturday
night, highest southeast. Sunday will continue with chance pops
southeast as moisture begins to pull east out of the area. Monday
models show a cold front moving through the area from the northwest
so will need a chance pop in for the day. High temps mainly mid
and upper 70s.
.AVIATION /00Z Tuesday THROUGH Saturday/...
Scattered showers and storms possible at the terminals through
the period as an upper low slowly moves east across the Great
Lakes region. The best chances for TSRA early in the period will
be at KFDY and KTOL, with lesser chances at KCLE and KMFD, and
primarily dry conditions elsewhere. A brief lull in convective
activity possible overnight before redevelopment around
daybreak Tuesday and again Tuesday afternoon. Some MVFR/IFR
stratus may impact KTOL toward daybreak, but will keep ceilings
MVFR at until confidence increases. Surface winds will remain
out of the southeast through the period, becoming fairly light
at most sites overnight.
OUTLOOK...Non-VFR conditions possible through Thursday in
scattered showers and tsra. Patchy morning fog for inland sites
Low pressure over SE Wisconsin will decrease as it moves toward
Ohio. This will allow the pressure gradient to relax and decrease
the winds Tuesday night into Wednesday. A cold front will sag
southward into the area on Thursday with increasing southwesterly
winds ahead of it. A large area of high pressure will build across
the lake Thursday night into Friday. The strongest winds will likely
be late Thursday into Thursday night with a small craft advisory
Area Forecast Discussion
National Weather Service Midland/Odessa TX
627 PM CDT Mon Aug 28 2017
See 00Z aviation discussion below.
Isolated TS will dissipate shortly and will not affect any TAF
sites. VFR conditions are expected through the period with
.PREV DISCUSSION... /issued 304 PM CDT Mon Aug 28 2017/
Current radar is showing a few isolated showers moving southwest
into the Permian Basin this afternoon. The HRRR indicates this
activity will persist through peak heating then quickly dissipate.
They are moving quickly and there is little shear so no flooding
or severe weather is expected. Models do not show any additional
rainfall this week though their course resolution may not pick up
some of these afternoon showers well. Have kept the forecast dry
until the weekend but do not be surprised to see some afternoon
showers this week.
Dewpoints dropping into the 50s will let overnight lows stay below
normal for the next few days. Model guidance appears to be
handling highs better and have stayed at or slightly above MEX/ECE
guidance this forecast period.
.PRELIMINARY POINT TEMPS/POPS...
Big Spring 63 89 63 89 / 0 0 0 0
Carlsbad 65 88 63 90 / 0 0 0 0
Dryden 69 93 67 93 / 0 0 0 0
Fort Stockton 64 88 62 89 / 10 0 0 0
Guadalupe Pass 61 79 61 82 / 10 0 0 0
Hobbs 60 86 59 87 / 10 10 0 0
Marfa 56 82 53 83 / 10 0 0 0
Midland Intl Airport 64 89 63 89 / 0 0 0 0
Odessa 64 89 62 89 / 0 0 0 0
Wink 65 89 62 91 / 10 0 0 0
Area Forecast Discussion
National Weather Service Mount Holly NJ
917 PM EDT Mon Aug 28 2017
High pressure will remain over northern New England and southeastern
Canada through early Tuesday. Meanwhile, an area of low pressure
positioned near the Georgia coast this afternoon could develop into
a tropical cyclone as tracks slowly up Southeastern U.S. coast
tonight and Tuesday. The low is expected to reach the Outer Banks of
North Carolina and then turn northeastward out to sea Tuesday night
into Wednesday. High pressure briefly builds into the region
Wednesday afternoon and night before a cold front progresses through
Thursday afternoon and evening. High pressure returns Friday and
Saturday. The next cold front will approach from the northwest on
Sunday and eventually move through the region either late Sunday or
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
930 pm update: Made some minor adjustments to temps/dew
points/winds/sky cover to account for latest trends. Otherwise,
the forecast is in good shape. The 18Z GFS increased QPF amounts
a little bit across the area, continuing the trend seen in other
operational models today. Thus, the changes made to PoPs/Wx
grids earlier seem OK at the moment. Previous (still relevant)
The 18Z NAM depicts the developing surface low just southeast
of the SC/GA coast will progress northeast along the SC
coastline this evening to near Wilmington, NC, by 12Z Tuesday.
This is reasonably agreed upon by most of the guidance. However,
with persistent onshore flow and increasing low-level
isentropic ascent as the low makes its approach along the coast
tonight, most models develop light rain well north of the low,
easily reaching the Delmarva Peninsula by 12Z. Some guidance,
including the HRRR and 18Z NAM Nest, suggests an even earlier
onset, though I suspect the low levels will require some
moistening before steadier precipitation reaches the ground. The
18Z NAM is notably dry, but it seems to have a dry bias on the
north side of developing coastal systems (at least since the
previous winter). Given the precipitation signal in most of the
guidance at this point, feel that raising PoPs overnight
(especially south of the Mason-Dixon Line) is appropriate.
Increased the speed of increasing cloudiness tonight as well.
Other main adjustment was to dew points, which were too high
for the past couple of hours. Moistening of the low levels will
probably be slower than progged owing to this bias so far this
evening...another reason I suspect the high-resolution output is
a little too aggressive bringing precipitation into the area by
Made slight adjustments to winds as well, mainly in accordance
with recent trends, to more of an east rather than a northeast
direction through the overnight.
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
Made some adjustments to the short-term forecast this evening.
Models are clearly struggling with the phasing process of the
developing coastal low and the midlevel vortex moving through
the Great Lakes on Tuesday. Run-to-run variability remains above
average even at this close range to the event. A look at the
18Z NAM (which is mighty different than its 12Z counterpart)
suggests that the low will pivot almost northward during the
morning hours to the Outer Banks region, then rapidly progress
east-northeastward as the vortex traverses eastward during the
afternoon. This progression eastward is aided by a kicking
shortwave trough moving through the Ohio Valley during the
afternoon (aided by a developing/strong midlevel jet streak).
Interestingly, another of these north-then-east pivots occurs
after the short-term period, in association with the longer-wave
trough becoming negatively tilted.
Timing is everything here, and models notoriously struggle with
the phasing process (note the general tendency to push the
coastal low too far east the past several days). Feel the best
approach is the "trend is your friend" approach to the forecast,
which appears to be a somewhat farther northwest track and a
somewhat stronger intensification of the low. With this in mind,
main adjustments were to spread higher PoPs northwest, increase
QPF in central/southern Delaware and far southeast New Jersey
(based on a consensus of WPC/HRRR/NAM Nest/ECMWF/RGEM/GFS), and
increase winds a little bit across most of the CWA.
For storm-total QPF, areal averages are at or below a half inch
northwest of I-95, 0.25-0.75 from I-95 to northwest of a Dover
to Toms River line, and 0.75-1.75 southeast of this line.
However, confidence is very low on totals because of the
aforementioned model uncertainties.
No changes to headlines at this time.
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
The coastal storm is expected to move off the coast Tuesday evening
to our south (exit point is likely north of Cape Hatteras and south
of Virginia Beach) and then accelerate east-northeastward and
out to sea through Wednesday. A slight trend was noted in the
12Z model guidance toward a stronger coastal storm with a track
that is slower and closer to the lower Delmarva coast.
Unfortunately, these trends put coastal areas at a higher threat
for hazardous weather. Farther inland, impacts from this storm
will be limited.
Gusty E-NE winds around sunset Tuesday evening will back through the
night, eventually becoming N-NE late. The strongest winds will be
near the DE and southeast NJ coast where gusts to around 45 mph are
expected to continue into the evening. A Wind Advisory covers this
threat. Despite the potential for NE winds of 40-50 kt residing at 2-
3 kft AGL to expand well inland as the storm takes its closest
approach to the southeast of us, weak lapse rates and lack of deep
convection should inhibit these stronger winds aloft to mix down to
the surface across inland areas.
It is becoming more likely that the northwestern edge of the precip
shield will be slower to depart, resulting in a continuation of rain
Tuesday night, particularly over the coastal plain. PoPs were
updated accordingly. The 12Z NAM appears to be the worst-case
scenario in terms of rainfall and flooding risk, showing 1-2 inches
in eastern PA and NJ and 2-4" in Delmarva. We went above WPC QPF,
but not nearly as high as the NAM. Any heavy rain will likely be
On Wednesday, drier air advecting around the backside of the
departing storm will yield breaks in the dense cloud cover from NW
to SE during the morning. However, the development of stratocu will
likely ensue after a few hours of stronger heating. The extent of
the additional cloud cover in the afternoon is uncertain at this
time but it could plausibly lead to mostly cloudy skies for some
locations. No mention of rain in the forecast for Wednesday or
Wednesday night with high pressure building into the mid Atlantic.
The high quickly retreats off the Southeast coast by Thursday
morning as a cold front approaches our area from the Great Lakes.
This front is expected to arrive first in the Poconos by early
afternoon, then the I-95 corridor by early evening and finally move
off the coast before midnight. Attempted to add some timing detail
in the forecast with the primary chance for showers and storms
confined to just the few hours leading up to the fropa. Owing to a
lack of deeper moisture and modest values from various instability
indicies, thunderstorm coverage and intensity should be limited.
After a week of seasonably cool conditions, temperatures on
Thursday...the last day of meteorological summer...briefly warm up
to normal with highs in the low to mid 80s.
High pressure build back into the region late Thursday night and
Friday. The high will continue to influence the area through
Saturday. Below normal temperatures and dry weather can be expected
during this time.
The high should move offshore Saturday night-Sunday while a cold
front approaches from the Great Lakes/Midwest. There are indications
that moisture from the remnants of Harvey could be drawn downstream
ahead of the approaching cold front and mid-level trough. This would
increase our rainfall chances for Sunday and/or Monday. Kept PoPs
low for now due to considerably uncertainty in the timing and
location of these features.
.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
For the 00Z TAFs...VFR conditions across the region will
deteriorate to MVFR from south to north after midnight into the
mid-morning hours Tuesday. Sped up the timing of rain reaching
the terminals, now generally in the 12Z to 16Z time frame,
though confidence is low near/northwest of PHL. Rain is
expected to last most of the day, especially southeast of PHL.
CIGs should remain MVFR or lower through the rest of the period,
with VSBYs possibly becoming sub-VFR at times as well,
especially at MIV/ACY, where somewhat heavier rain is expected.
Winds generally between 50 and 110 degrees near 10 kts tonight
becoming 10 to 20 kts tomorrow with higher gusts, especially
near the coast.
Tuesday night...MVFR conditions expected to affect all TAF
sites with the potential for IFR closer to the coast where a
period of heavier rain is possible. E-NE winds veer to the N-NE
late. Winds will be strongest toward the coast where gusts to 35
kt are possible at ACY.
Wednesday and Wednesday night...Lingering MVFR ceilings in the
morning should improve to VFR from NW to SE.
Thursday and Thursday evening...Predominately VFR. A chance of
showers and slight chance of thunderstorms. A wind shift from SW
to NW is expected late in the day with a cold fropa.
Thursday overnight through Saturday...VFR expected.
Made several adjustments to the marine forecast, including
increasing seas through tomorrow night, based on this evening`s
observations, and increasing the swells based on a combination
of obs and recent model data. The next 24-36 hours will be rough
on the coastal waters. Current seas forecast to be generally 6-9
feet through early morning, 7-12 feet through around midday,
8-15 feet tomorrow afternoon and evening, before a slow decline
late Tuesday night. Wind forecast looks good and may only minor
adjustments (mainly to timing of the peak winds).
No changes to the headlines at this time.
Tuesday night...Gale Warning continues for the southern New
Jersey and Delaware coastal waters and lower Delaware Bay.
The warning may ultimately need to be expanded northward to
include ANZ450-451 if the storm continues to trend farther
north. Elsewhere, a SCA is in effect. Raised seas by 3 to 4 ft
above WaveWatch guidance after accounting for a low bias in the
model in NE flow. Seas may reach 14-16 ft at 44009 by evening.
Wednesday...SCA was extended into Wednesday for ANZ450-451.
Winds may still be near 25 kt early in the day before quickly
decreasing. Seas will take much longer to subside with long-
period easterly swells continuing to impact the area even after
the low departs.
Wednesday night and Thursday...Winds expected to be below SCA
threshold, but seas may remain above 5 ft.
Thursday night through Saturday...Winds and seas below SCA
No-brainer forecast here. With seas forecast to increase
through tomorrow evening and onshore winds increasing to gale
force in the southern NJ and DE coastal waters (and not far from
gale force to the north), the risk of dangerous rip currents is
high through tomorrow night. Combined with rough surf, entering
the waters may be dangerous. Heed beach restrictions and
closures from local officials.
An onshore flow is expected through Tuesday night. While water
levels will be on the increase, we are at the first quarter moon so
astronomical tides are relatively low. It would take a surge of
nearly 2 feet to cause widespread minor flooding along the coasts of
Delaware and New Jersey. At this time, latest surge guidance does
not show this, although met model trends over the last 2 days show a
northward jog with the surface low.
Because of this northward jog in the forecast storm track, in
combination with onshore winds around 45 mph and building seas
with wave runup expected, we feel mentioning spotty minor
flooding is the prudent thing to do south of Little Egg Inlet.
In addition, any rain falling at the times of high tide could be
slow to drain right along the coast and backbays.
Along with the high surf, beach erosion is expected on Tuesday and
could persist into Wednesday with the continuation of long period
swells. Across southern NJ and DE, where the beach erosion will
be more significant, a High Surf Advisory was issued for Tuesday
and Tuesday night. Refer to PHLCFWPHI for more information.
NJ...High Rip Current Risk through late Tuesday night for NJZ014-
High Surf Advisory from 6 AM Tuesday to 6 AM EDT Wednesday for
Wind Advisory from noon Tuesday to midnight EDT Tuesday night
DE...High Rip Current Risk through late Tuesday night for DEZ004.
High Surf Advisory from 6 AM Tuesday to 6 AM EDT Wednesday for
Wind Advisory from noon Tuesday to midnight EDT Tuesday night
MARINE...Gale Warning from 6 AM Tuesday to 4 AM EDT Wednesday for
Small Craft Advisory until 6 PM EDT Wednesday for ANZ450-451.
Small Craft Advisory until 4 AM EDT Wednesday for ANZ430.
Gale Warning from 6 AM Tuesday to midnight EDT Tuesday night