Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/13/17
Area Forecast Discussion
National Weather Service Grand Forks ND
854 PM CDT Tue Sep 12 2017
.UPDATE...
Issued at 854 PM CDT Tue Sep 12 2017
Most of the high resolution models are keeping the FA dry tonight.
The latest runs show the echoes moving into central SD and drying
up as they move toward our southern FA. For that reason will
remove the low pcpn chances we had going across the far south for
late tonight.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 235 PM CDT Tue Sep 12 2017
Wind shift moving into the northwestern portion of the FA this
afternoon will stall out in a few hours across the northern third
of the area. Will continue a slight shower mention in the southern
valley overnight as SFC trough in SD with convection ongoing near
the Blackhills lifts NE this evening into the overnight. RAP and
latest runs of HRRR do show some activity reaching the southern
valley near 10 to 12z. Also of some concern will be fog potential
overnight with stalled boundary and light winds along this
feature. Airmass dewpoints are in the 50s and 60s and with clear
skies and light winds patchy fog does appear possible. Will
continue to monitor the potential with lows expected to fall into
the mid 50s and low 60s, near dewpoint values.
Aforementioned boundary will help create a tight baroclinic zone
tomorrow afternoon with max temps in the north along the Intl
border in the upper 70s compared to across the central valley and
areas to the south temps will be pushing near 90 again. The
boundary will slowly work southward in the afternoon.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 235 PM CDT Tue Sep 12 2017
Models are in general agreement for this forecast period. By
Wednesday night and Thursday, the weather pattern changes and
becomes more unsettled as southwest flow aloft begins to dominate,
and an upper level trof digs in the intermountain west. Surface
features indicate a relative open Gulf so expect some decent
moisture transport ahead of the slow progressing surface system.
As the surface system progresses slowly across the northern
Plains, more beneficial rain amounts are anticipated, mainly in
the one to two inch range. Otherwise, expect much cooler and
cloudy conditions to be in place through Monday, with highs mainly
in the 60s to near 70. By the end of the period, a slow warming
trend will take place, with scattered showers expected.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 618 PM CDT Tue Sep 12 2017
Pretty quiet set of TAFS again. Wind speeds will remain on the
lighter side, with just some high level smoke drifting in.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Godon
SHORT TERM...JK
LONG TERM...Hopkins
AVIATION...Godon
Area Forecast Discussion
National Weather Service Sioux Falls SD
1052 PM CDT Tue Sep 12 2017
.UPDATE...
Issued at 704 PM CDT Tue Sep 12 2017
Just launched an update for our far western zones in central SD
for isolated to low end scattered chance pops for TSRA this
evening. There is convection moving slowly eastward in western SD,
and some of this may ooze into our far west later this evening.
However the NMM and ARW, and HRRR for the most part do not bring
it in the James River valley. Not a lot of dynamics are associated
with this convection.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 232 PM CDT Tue Sep 12 2017
Quiet weather continues this afternoon as we remain stuck under weak
flow aloft. This has resulted in clear skies and temperatures in the
80s at most locations. By this evening, a weak piece of energy
sneaks off of the wave currently evident on WV imagery over WY, and
slides along the NE/SD border. This could be enough to utilize some
very subtle elevated instability originating from the 850-700 mb
level. Current thinking is that dry air in the low and mid levels
will limit this activity to just sprinkles however.
Wednesday looks to be another warm but quiet day across the region
as we remain between systems. High temperatures look to be a touch
higher than this afternoon with 850mb temps in the low to mid 20s C,
resulting in widespread mid 80s to mid 90s. Otherwise, looks for
plenty of sunshine and southerly winds to continue.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 232 PM CDT Tue Sep 12 2017
Strong southerly surface pressure gradient in place on Wednesday
night, especially east of the James River, as low pressure deepens a
bit over central SD. This should keep temperatures very mild through
the night and will lean much closer to the CONSRaw output for
morning lows which usually handles the windier nights much better.
Will have to watch the Buffalo Ridge area as well with winds
possibly turning a bit south southwest and a fairly shallow
inversion in place. This pattern is occasionally supportive of
stronger winds on the ridge so will go a little higher, but not too
high as the wind direction is not quite normal to the Buffalo Ridge.
Will have to keep an eye on thunderstorm chances towards central SD
late Wednesday night as a weak wave moves through SD. For now
chances will remain on the low end.
Thursday looks to be warm, breezy and a little humid as a weak
boundary drifts into central SD. A very small chance for early
morning showers and thunderstorms as the weak wave moves through. By
afternoon a boundary in central SD behind this wave does not appear
as though it will produce any convection during the day as model
soundings are strongly capped and mid and upper level heights are
rising behind the exiting wave.
Friday late afternoon into Friday night will see a threat for
thunderstorms. A surface front will be in place across central SD
into northeast SD with the warm sector in place across most of the
area. Most of the warm sector looks pretty capped into the evening
but locations a little closer to the boundary may see enough heating
to break the cap. The area near the boundary is also more in line
with the forcing from the upper level wave. Shower and storm motion
will likely be easterly so the threat will shift east Friday night.
While severe weather should not be a major issue an isolated strong
to severe storm will be possible west of Interstate 29 with about
1500 J/kg CAPE and surface to 3 km shear about 30 knots.
Saturday a tougher call with some disagreement on timing of the cold
front. Will lean towards the slightly slower solutions as the upper
level jet is progged to lift northeast which should allow the warm
sector to heat out a bit before the cold air settles in. Increased
lows a bit everywhere on Friday night with potential for clouds and
southerly winds and increase highs a bit in northwest IA and
southwest MN along and ahead of the front.
Sunday into Tuesday will see cooler air settle in. Looks like the
cool down will not be real significant and it should be fairly short
lived as a trough of low pressure aloft deepens across the Rockies
and an upper level ridge builds into the area.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1045 PM CDT Tue Sep 12 2017
VFR is expected over the 06Z TAF period. One thing to watch for is
in the near term. Isolated TSRA continues in central SD near a
surface trough axis extending southward from a short wave passing
through to the north of this area. There is a chance that some of
this skittish convection could reach the KHON TAF site from 08Z
and 10Z Wednesday. However due to the isolated nature of this
convection and not a high degree of confidence in their eastward
movement, left out of the KHON TAF site for now.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
UPDATE...MJ
SHORT TERM...Kalin
LONG TERM...08
AVIATION...MJ
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1037 PM EDT Tue Sep 12 2017
.UPDATE...
Issued at 1037 PM EDT TUE SEP 12 2017
WSR-88D radar continues to display a line of showers that
continue to push north and east across the Bluegrass. Therefore,
did update POPs to match latest radar trends and still seeing
about a quarter of an inch or less storm total precipitation for
most locations. The WSR-88D dual pol estimates seem to be doing
reasonable based on some of the area gauges. The models seemed to
continue to handle the line reasonably but still too fast.
Overall preferred leaning toward the HRRR TL for the initial POP
grid and manual adjustments there after. This will move out of the
region and we will await the post tropical system to progress
east. This could bring showers into the Lake Cumberland region
toward dawn, but will likely be slow to advance east given the
continued downslope flow across the Smokies to the south. Also
updated with the latest obs and trends.
UPDATE Issued at 750 PM EDT TUE SEP 12 2017
The afternoon surface analysis does show that post tropical system
Irma is centered in Middle Tennessee and a area of surface high
pressure remains to our north and east. There has been some weak
upper level frontogenetical forcing moving northward across
portions of central and eastern Kentucky this evening. WSR-88D
does show showers developing near this forcing and moving
northward. Did adjust the grids to match up with radar trends and
short term model data. The one caveat is the models have been a
bit too fast moving this north, and therefore made some
adjustments to deal with this idea. It does appear that in
general these showers will produce a quarter of an inch or less in
QPE. Otherwise adjusted SKY, temps, winds, and dews to match
latest obs a trends.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 300 PM EDT TUE SEP 12 2017
The remnants of Irma will continue to bring scattered rain showers
to eastern Kentucky the rest of this afternoon through late this
evening as they meander about southern Mississippi and lower
Tennessee valley regions. The remnants will begin a slow but
steady northeastward track late tonight through early Thursday
morning. Rain chances will steadily increase on Wednesday, as the
center of the circulation moves over the area. The highest chances
of showers will be from late Wednesday through early Thursday
morning. Rainfall amounts should be low enough as to not cause any
issues across eastern Kentucky. Temperatures will continue to run
well below normal, with lows the next two nights in the upper 50s
expected and highs on Wednesday in the mid to upper 60s expected
for most locations. A few spots in our far eastern counties may
max out in the low to mid 70s due to slightly less cloud cover
there.
.LONG TERM...(Thursday through Tuesday)
Issued at 414 PM EDT TUE SEP 12 2017
The extratropical remnant of Hurricane Irma, in the form of a
mid/upper level low, is expected to be centered over southern OH at
the start of the period, with a pool of moisture rotating around it.
The moisture will be primarily below the 600 mb level, but still
sufficiently deep for light precip. Although amounts will be light,
there probably will be enough rain to measure in most locations on
Thursday morning. GFS MAV POPs are in the likely category for
Thursday, and seem to be a reasonable fit.
As the low continues to weaken and slowly move northeast away from
our area, the low level moisture will also fade. The last of the
precip should dry up in the afternoon or evening on Thursday, and
clouds should start to break up. With light winds and only a limited
rise in temperature during the day, it would be a good set-up for
fog in locations which clear out on Thursday night. Any fog will
dissipate on Friday morning as daytime warming kicks in. Forecast
soundings show that the warming may support a few light showers in
the eastern part of the forecast area on Friday, but convection
would be sharply capped around 750 mb. Further west the cap would be
even lower and not allow for more than fair weather cu. Mid/upper
level ridging building into the area is then expected to bring
mostly clear skies from Friday night through the weekend.
Early next week, forecast confidence declines as the models fall out
of agreement concerning a cold front moving in from the northwest.
The ECMWF is the most progressive with the front, the Canadian the
least, and the GFS falling in between. It`s initial approach would
be from the northwest on Monday. The ECMWF has it moving past us to
the southeast by Tuesday. Meanwhile, the other models stall the
front and weaken it without a clean passage. Considering the
uncertainty, have used a low POP each period Monday through Tuesday.
Frontal passage vs. no passage would also have implications for
temperatures, and a middle ground will be used.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 730 PM EDT TUE SEP 12 2017
The latest surface analysis shows post tropical system Irma
centered across Middle Tennessee and high pressure still remains
off the the north and east of the Ohio Valley. There is some upper
level frontal forcing moving north across central and eastern
Kentucky and showers are riding north along and near this
mechanism. This could move into SYM and lead to VC showers at JKL,
but otherwise not expecting any major issues related to this for
most TAF sites. Overall the downslope flow and dry slot will keep
CIGs VFR through Wednesday afternoon. The only other question
tonight will be if clearing can take place in the east and
decoupling of deeper valleys then you could see some patchy fog
overnight. The post tropical system will move back as a more
typical synoptic upper level low Wednesday. This will lead to
increasing chances of showers especially Wednesday afternoon and
this will be accompanied by lowering CIGs and VIS to MVFR. Winds
will continue to decrease tonight and should stay fairly light
through the period. However, some of the heavier showers that
develop Wednesday afternoon could mix down stronger low level jet
winds leading to isolated higher gusts.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...DJ
SHORT TERM...AR
LONG TERM...HAL
AVIATION...DJ
Area Forecast Discussion
National Weather Service Nashville TN
749 PM CDT Tue Sep 12 2017
.UPDATE...
FOR 00Z AVIATION DISCUSSION.
&&
.DISCUSSION...
Latest surface analysis places the center of the remains of "Irma"
over far northwestern AL. This feature will continue to work slowly
northward overnight. Latest model qpf and Hrrr data suggests
shower redevelopment later this evening, beginning over western
zones and eventually spreading east. Rainfall, however, will be on
the light side with amounts averaging around one to two tenths.
The slow northward movement of "Irma" will continue over the next
few days. Thus, look for clouds to persist with a good chance of
light shower activity through Wednesday nt. On Thursday, the
remains of "Irma" will begin to spread eastward. So, after a final
period of low pops, Thursday night will be partly cloudy and dry.
For the near term temps, we will see another 36 hrs of cool weather
before a warmup begins. High temps on Wednesday will again be in the
60s but as partial sunshine returns by Thu afternoon, temps will
push well into the 70s.
In the ext fcst, upper level high pressure to develop over the
northern gulf on Friday with ridge amplification into the weekend.
The ridge will weaken and drift westward next week, allowing for
more of a northerly and westerly upper wind component to emerge. A
frontal boundary will then approach. Thus, low shower and tstm
chances will return for Monday.
For the ext temps, the warming trend will continue on into the
extended and will be helped by the aforementioned weekend ridge
amplification. High temps over the weekend will reach into the mid
to upper 80s west of the Plateau. these warm temps will continue
into next week as well. Low temps will also be a few degrees above
normal with 60 to 65 degrees expected.
&&
.AVIATION...
00Z TAF DISCUSSION.
As the remnants of Irma continue to swirl overhead, expect a trend
toward IFR conditions overnight and a continuation of IFR at most
terminals during the daylight hours on Wednesday as well. The
only exception is expected to be at CSV, where IFR conditions
overnight will trend toward MVFR after 15z.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......13
AVIATION........19
Area Forecast Discussion
National Weather Service Raleigh NC
1020 PM EDT Tue Sep 12 2017
.SYNOPSIS...
An area of low pressure aloft will drift northeast from the
Tennessee Valley into the Ohio Valley through Thursday morning. This
will place central NC in a warm air mass with temperatures close to
normal for mid September.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 1020 Tuesday...
Little change to the near term forecast.
As earlier discussed, low level flow has become swly across the
southern Piedmont and dewpoints have lowered into the mid 60s at
such places as Wadesboro (64 degs at 10 PM) and Albemarle (66 degs).
The 00Z RAP appears to have a decent handle on this trend (possibly
a little too aggressive); thus, this drier air should begin to
infiltrate the Triad and the Triangle areas after midnight, and
reach the Virginia border counties by daybreak.
Beginning to see areas of fog develop in vicinity of the I-40
corridor, mostly in the Triad region. May see visibilities dip
briefly to or below a quarter of a mile prior to the arrival of the
drier air mass which should lead to improving visibilities. The same
goes for the Triangle where areas of fog may limit the visibility to
around a half mile prior to the arrival of the drier air. Currently
expect the best potential for patchy dense fog to occur in vicinity
of I-85 between the Triad and the VA border, and locations north of
the Triangle.
Isentropic upglide, as per 00Z 850mb analysis, helping to maintain a
few showers along and north of the sfc warm front, stretching from
the Triad to near Raleigh to Halifax. This flow expected to veer to
a more swly direction overnight. This should place the focus for a
few showers to develop over the far northeast Piedmont and far
northern coastal plain.
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 300 PM Tuesday...
IRMA`s remnant low will continue to weaken as it moves northeast
through the Ohio Valley on Wednesday, before crossing the central
Appalachians late Thursday. Central NC will lie along the far
eastern and then southern fringes of IRMA`S remnant cyclonic
circulation, with a glancing shot of DCVA supporting isolated to
scattered showers late Wednesday/Wednesday night that could
potentially linger into the day on Thursday, at least across the
northern/northeastern portions of the forecast area.
Instability is severely lacking, and thus no is expected.
Temperatures will return to more seasonable values with the return
of sunshine. Highs ranging from upper 70s NW to mid 80s SE. Lows in
the lower to mid 60s.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 300 PM EDT Tuesday...
Increasingly sheared remnants of IRMA`S mid/upper level vorticity
center will drift northeast and then linger across the Mid-Atlantic
region through the weekend as as an upper level ridge over the
western GOM builds slowly northeast into the region. Meanwhile,
current forecast keeps TC Jose will be over the western Atlantic,
though there is still considerably large model spread. Expect dry
conditions with near normal temperatures expected to dominate this
weekend and early next week.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 800 PM Tuesday...
24 hour TAF period: The Triad terminals will continue to experience
LIFR ceilings for at least the next couple of hours. There may be a
brief period where ceilings lift and then come back down again but
in general expect these conditions through much of the overnight
time period. Even if ceilings lift, visibilities could remain low in
the form of fog until after daybreak. This pattern of low ceilings
and visbys will pan out across the northern TAF sites in some form
or another. KFAY is the only site that is expected to only
experience MVFR visibilities at worst overnight. Otherwise they will
clear out sooner as drier conditions move in from the south. Despite
a few showers around precipitation will generally end from south to
north overnight as the leftover rainbands from Irma exit the area.
Conditions will gradually return to VFR after sunrise and should
remain there through the end of the TAF period. Winds will be light
and variable overnight and increasing to 5-10 kts out of the
southwest on Wednesday.
Looking ahead: Rain chances and also the chance for fog/low stratus
during the overnight hours will remain in the forecast through
Thursday before clearing out for a VFR weekend.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...WSS
NEAR TERM...WSS
SHORT TERM...CBL
LONG TERM...CBL
AVIATION...Ellis
Area Forecast Discussion
National Weather Service Reno NV
112 PM PDT Tue Sep 12 2017
.SYNOPSIS...
Low pressure near the California coast along with above normal
moisture will produce good chances for showers and thunderstorms
through Wednesday. The first cold front of the Fall season will
bring gusty winds Thursday along with another chance for showers
or storms. The cold front will bring much cooler temperatures
Thursday and Friday, with a modest warm up for the weekend.
&&
.SHORT TERM...
Current satellite imagery shows scattered showers and thunderstorms
are developing and moving from south to north. For this afternoon
and again tomorrow afternoon the ingredients are in place for
scattered thunderstorms and localized heavy rain. Computer-modeled
vertical profiles of the atmosphere show long skinny CAPE and not
a lot of shear both afternoons, which suggests small hail and
wetting rains are likely. There is also potential for some
stronger/severe thunderstorms. Latest runs of high resolution HRRR
model is consistent with this, showing areas of showers along
with pockets of stronger cells. Any stronger cells that do develop
will have potential for flash flooding (especially in steep
terrain or on burn scars), gusty outflow winds 40 to 50 mph, and
possibly up to 3/4 inch size hail.
For tonight and again tomorrow night, areas of rain are likely to
persist overnight, with isolated embedded thunderstorms possible.
For Thursday, a cold front will bring westerly winds with peak
gusts 25-35 mph in valleys and 35-50 mph along ridges. The relative
humidity/wind gust combination doesn`t look too critical, although
a few hours of red flag conditions in Mineral County may be possible
Thursday afternoon. Showers (especially north of I-80) and a slight
chance for thunderstorms (mainly east of highway 95) are also possible
with the frontal passage Thursday. JCM
.LONG TERM...Friday into next week...
Computer guidance continues to show troughiness for Friday into
next week. If skies are clear overnight there is potential for
frost in colder valleys, so gardeners should check their forecast
overnight temperatures and be prepared. Light northerly flow
Friday/Friday night will shift to a dry southerly flow Saturday as
the next trough approaches. This should lead to a slight warming
trend for afternoon temperatures Saturday and Sunday, with highs
forecast to be 75-85 in western NV and 65-75 for most Sierra
communities. A cold front passage could bring strong gusty winds
Sunday night/Monday along with much cooler temperatures early next
week (highs could be mainly in the 60s Tuesday). The trough could
also bring a chance of showers to the Sierra and northern CA by
Monday afternoon, possibly spreading south and east across the
eastern Sierra and western NV Monday night/Tuesday. JCM
&&
.AVIATION...
There is a 40% chance of thunderstorms at all main terminals
(KRNO/KTVL/KTRK/KCXP/KMMH) this afternoon and evening, and then
an equal chance again tomorrow. The main threats from these
thunderstorms are erratic wind gusts up to 40 kts and heavy rain.
Storm coverage and intensity should decrease after 03Z this
evening and again tomorrow evening but scattered showers and a few
thunderstorms could continue overnight both nights.
A cold front passage on Thursday will bring gusty winds and
chances for showers and thunderstorms. Thunderstorms on Thursday
are not expected to be as strong but erratic wind shifts and
brief MVFR conditions will still be possible. JCM
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno