Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/14/17
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
536 PM MDT Thu Jul 13 2017
.AVIATION...
00Z TAF CYCLE
Thunderstorms are scattered along an axis from the southwest corner
to the northeast corner of New Mexico early this evening where the
best instability resides. Storms have already moved off of the
higher terrain and filled into lower elevations and portions of
central valleys with localized outflow boundaries leading to new
storm development. This trend will continue through the early to mid
evening, and while the bulk of the storm activity is expected to
diminish by midnight, a few straggling storms will likely linger into
the early morning hours. Brief downpours and very gusty and erratic
outflow winds will be the primary aviation hazards. Storms are
expected to re-focus over northern and western New Mexico on Friday
with drier and more stable air working farther into eastern and
central parts of the state.
52
&&
.PREV DISCUSSION...300 PM MDT Thu Jul 13 2017...
.SYNOPSIS...
Showers and thunderstorms will continue to be active over northern
and central New Mexico through next week, but with some day to day
variations in number, areal coverage and storm motion. A few strong
storms with penny size hail and wind gusts to around 55 mph are
possible through this evening over northeast New Mexico. Locally
heavy rain due to the slow movement of storms could produce arroyo
and street flooding as well. High temperatures will be within a few
degrees of normal through this weekend.
&&
.DISCUSSION...
Convection stretched across the area from southwest to northeast
this afternoon, along the theta-e axis. Earlier short term model
runs didn`t seem to generate much in the way of convection for this
afternoon/evening but now the HRRR is latching onto the Southwest
mts, Northeast Highlands into the Northeast Plains for the rest of
the afternoon/early evening as drying/subsidence associated with the
easterly wave impacts the east central/south central and southeast.
NAM12 which was so bullish in recent days on the northeast this
afternoon/evening is now ho-hum with the precipitation bullseye
remaining over se Colorado. SPC still has a marginal risk outlooked
for the northeast.
The upper high centers consolidate over the Great Basin/Colorado
during Friday/Saturday with a weak upper low circulation embedded
and wobbling around ern Colorado. The GFS no longer takes the weak
low through the upper high circulation into NM but drifts it into
the Plains states while the upper high center(s) waver back to the
east and over Colorado and the Plains states. The ECMWF takes the
weak low into northeast NM before it loses definition. Overall the
GFS doesn`t seem to be as wet as it was 24 hrs ago for the upcoming
weekend. At 240 hrs, the ECMWF puts the upper ridge to our west with
nw flow aloft, while the GFS holds the upper high center over
Colorado which isn`t as promising for a monsoon moisture burst.
Either way, there will continue to be at least a few showers and
storms each day.
&&
.FIRE WEATHER...
The upper level high looks to be re-developing just south of the
Four Corners today. The upper high will strengthen into Friday as it
shifts over northwest AZ. The upper high will continue to meander
around northern AZ and southern UT through the weekend. Meanwhile,
an easterly wave currently just west of the Big Bend area of Texas
will continue to shift westward under the upper high. Subsidence
ahead of the wave is currently over the far east central plains of
NM, which should largely limit convection through the evening there,
though NE NM will remain active thanks to a boundary moving in from
Colorado. This area of subsidence will shift westward on Friday
which is expected to decrease storm coverage across portions of
central NM. Northern and western areas will remain active.
On Saturday, there still may be some dry/subsident air lingering
over the south central and east central plains areas. But overall,
storm coverage will likely be similar to that of today. On Sunday,
storm coverage may increase as bit as moisture trends upward. PWATs
on Friday and Saturday will be in the 0.70-1" range, but these will
trend up near 1" areawide on Sunday.
Early next week, the ECMWF continues to shift the upper level high
to the east of NM, but the latest run of the GFS shifts the high
only over the NM/CO border. Since the GFS seems to be waffling back
and forth, have higher confidence in the ECMWF. So, while it might
be more of the same for Monday, by Tuesday and Wednesday, a more
robust monsoonal plume may take shape over western NM. This would
certainly mean greater storm coverage and also more wetting rain.
High temperatures will only vary a degree or two day to day for the
next several. Areas of poor ventilation will become a bit more
widespread over the weekend across northern and western NM. This
may continue into early next week as storms become more widespread.
34
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Columbia SC
1049 PM EDT Thu Jul 13 2017
.SYNOPSIS...
High pressure ridging into the forecast 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 FRIDAY MORNING/...
Convection across the western Midlands has dissipated with some
cloudiness remaining. Expect the clouds to dissipate over the
next couple of hours with mostly clear skies for the forecast
area overnight. After a hot day temperatures have fallen into
the low 80s and with light winds and mostly clear skies
temperatures will continue falling. Overnight lows will
generally be in the lower 70s for most locations.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Upper-level ridge remains over the area through the day...then
shifting to the south Friday night. H85 temperatures a little
warmer because of weak warm advection and downslope component
so expect upper 90s for afternoon temperatures. Weak Piedmont
trough may result in enhanced low-level convergence in the
north Midlands. Steep low-level lapse rates but high LFC and
shallow moisture should result in isolated afternoon
thunderstorms at best given lack of forcing. High DCAPE does
suggest a wind threat from any convection. Any convection should
diminish quickly after sunset. Heat index values will peak 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 /SATURDAY THROUGH THURSDAY/...
The upper ridge will be suppressed to the south of the area,
closer to northern Florida into next week. This is in response
to a deepening east coast trough pattern that will be setting up
through the weekend as strong ridging takes hold across the
western half of the continental United States. The eastern
trough will help push a cold front closer to the area
Saturday, and this will help cause an increase in showers and
thunderstorms during the afternoon hours, especially across the
northern cwa closer to the front and upper trough. SPC has area
in marginal risk of severe weather. The front will push into the
central cwa Saturday night into Sunday before stalling out over
the area. This will continue to be the main focus for
convection into early next week. PWATs will be back at or above
2 inches through the weekend as moisture over the area increases
along the front. 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 by Tuesday into Wednesday and will keep a mention of
diurnal convection in the forecast through the end of the
period. The GFS is deeper with the upper low than the ECMWF.
Temperatures will remain hot and above normal Saturday with
highs in the mid 90s. Temperatures become slightly cooler Sunday
through next week as the upper trough remains across the area.
Low temperatures will be near normal through the period.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
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 circulating into the area associated with the offshore
ridge may help cause stratus and fog. The HRRR and SREF
guidance suggests a greater threat in the southeast section
mainly during the 09z to 14z time frame. The guidance was most
consistent with restrictions at OGB. Forecasted a period of IFR
at OGB and MVFR at AGS. Elsewhere, less moisture combined with a
little mixing associated with a weak low-level jet and
instability supports less of a chance of stratus and fog.
Heating and mixing should 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...
Scattered to numerous thunderstorms will be associated with a
slow moving cold front especially Saturday afternoon through
Sunday. There may be widespread stratus and fog during the early
morning hours during the outlook period.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Duluth MN
833 PM CDT Thu Jul 13 2017
.UPDATE...
Issued at 833 PM CDT Thu Jul 13 2017
Upper level closed low is moving farther to the east this evening.
This is allowing ridging aloft and at the surface to build into
the area. Drier air is already eroding some of the cloud cover
over the northwest corner of the forecast area. Elsewhere, the
clouds are hanging tough and it will be awhile before holes open
and additional clearing begins. The drizzle will be ending shortly
due to the drier air. Some fog is still possible after the
clearing as the wind goes light and variable. Made some minor
adjustments.
&&
.SHORT TERM...(This evening through Friday)
Issued at 315 PM CDT Thu Jul 13 2017
As of 20Z today, we continue to observe light returns on the
current radar imagery. Mainly seeing drizzle and light rain
showers falling at this time. This is all due to mid- to upper-
level shortwave trough and cyclonic flow that will eventually make
its way out of the region by this evening. There are a few lobes
of positive vorticity advection embedded within the wave,
providing the synoptic forcing. RAP and NAM model soundings
indicate a layer of low-level saturation from 950-800 mb,
providing ample moisture for these showers/drizzle. The best
chances of persistent showers and drizzle will continue to be from
the Twin Ports and locations adjacent to Lake Superior along the
North and South Shore areas. Accumulation amounts will remain on
the light side, with up to one-tenth of an inch possible. Some
clearing skies will move into our northwestern portions of the
forecast area through the afternoon and evening hours. The biggest
uncertainty for tonight will be how quickly cloud cover moves out
over the region. If clouds are able to retreat faster than
expected, then cooler temperatures will be possible for tonight. I
did reduce tonight`s lows slightly to better capture the
radiational cooling from the lack of clouds as I have cloud cover
moving out faster than what we had previously. However, some of
the model guidance did have some of these clouds lingering, which
would keep temperatures warmer tonight if this comes to fruition.
Lows tonight should be in the mid to upper 40s for most locations,
with near 50 along our south.
Mid-level ridging will amplify tonight over the Intermountain West
states as the shortwave departs to the east, which will remain in
control through the rest of the short-term period. Sfc high pressure
will build across the Northland, keeping winds light under the sfc
high pressure ridge. However, by the late afternoon, some small
chances of showers may move into Koochiching and Itasca counties as
a wing of 850-700 mb warm air advection moves in from the northwest.
Winds will become more southerly over our western counties helping
to warm temperatures up a bit. Temperatures will be their coolest
over northwest Wisconsin as this is where cloud cover will linger
over the longest. Thaler QG 850-300 mb layer omega also shows
strengthening deeper forcing as this warm air advection moves in.
There is some uncertainty if chances of precipitation would hold off
until after 00Z Saturday though. In any case, this will be the
precursor to increased chances of showers and thunderstorms that
will move in Friday night and Saturday morning. Highs will range
from the mid 70s over northwest Wisconsin to the upper 70s and near
80 over our western counties.
.LONG TERM...(Friday night through Thursday)
Issued at 315 PM CDT Thu Jul 13 2017
An upper level shortwave in northwest flow will combine with a
surface frontal boundary, as it moves southeast across the Northland
Friday night and Saturday. The front will bring a chance of showers
and thunderstorms to the Northland during the overnight hours of
Friday night and on Saturday. A few of the storms could be strong to
severe, especially over northwest Wisconsin on Saturday. High
pressure will build into the region on Saturday as well, bringing
generally dry conditions to northeast Minnesota by afternoon.
Coverage for the storms will be fairly limited, and generally along
and ahead of the frontal boundary. Upper level heights will build as
the surface high pressure builds into the area on Saturday and
Saturday night. This will result in a generally dry weekend for most
areas of the CWA. The dominant upper level ridge will flatten
considerably over the weekend and into early next week, with a
shortwave in the northern states and south central Canada
significantly flattening the upper level flow. A cold front and
upper level shortwave will bring a chance of showers and
thunderstorms to the region on Monday and Monday night, before the
front returns northward again as a warm front on Tuesday and
Wednesday. The ECMWF would support more precipitation into Wednesday
as well, but the GFS indicates a more substantial area of high
pressure across the northern Great Lakes. The ECMWF does show the
best consistency, so opted to continue POP`s on Wednesday before a
drying trend on Thursday. Highs throughout the period will range
from the 70s to middle 80s, with overnight lows ranging from the 50s
to lower 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 618 PM CDT Thu Jul 13 2017
As the closed upper low pulls off to the east tonight, this will
allow ridging to build across the region. MVFR/IFR cigs expected
through tonight with an improvement to VFR shortly after sunrise.
Some BR at DLH/HIB/HYR overnight with vsbys into the MVFR range.
This will also improve after sunrise to VFR. Dry air and a clear
sky by mid morning.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 49 76 58 82 / 20 0 30 20
INL 45 79 59 77 / 0 20 30 10
BRD 49 78 61 85 / 10 0 20 20
HYR 49 76 56 84 / 10 0 10 20
ASX 49 77 57 83 / 20 0 20 20
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
UPDATE...GSF
SHORT TERM...JTS
LONG TERM...DAP
AVIATION...GSF
Area Forecast Discussion
National Weather Service Hastings NE
829 PM CDT Thu Jul 13 2017
.UPDATE...
Issued at 827 PM CDT Thu Jul 13 2017
A few topics regarding the latest mid-evening forecast update:
1) Am getting a little more concerned about potentially
"impactful" fog in parts of the coverage area (CWA) for late
tonight into Friday morning. Typically, mid-July is not a
favorable time of year for more than patchy ground fog, but given
various factors, including very light/variable winds, mainly clear
skies (especially over Nebraska zones), high boundary layer
dewpoints/relative humidity and added moisture contribution from
recent rains (at least for some), it seems reasonable why various
short term models such as the HRRR, RAP and NAM are suggesting
potentially problematic fog development especially during the 4-9
AM time frame. While confidence is still too low to formally
advertise widespread dense fog (let alone issue an Advisory), did
"beef up" fog potential a bit in the latest Hazardous Weather
Outlook (HWOGID).
2) Thunderstorm/rain chances: While the combination of a subtle
mid level wave and at least weak elevated instability justifies
the continued mention of small rain/thunderstorm chances
overnight in most of our KS zones, have removed all formal
mention of rain overnight for our Nebraska counties. Even where
the small chances linger in KS, the odds of severe storms look
quite low, and agree with SPC in formally removing the lingering
Marginal Risk from our far southern CWA on their latest 01Z/8PM
update.
&&
.SHORT TERM...(This evening through Friday)
Issued at 319 PM CDT Thu Jul 13 2017
As of 330 PM CDT KUEX doppler radar was indicating an expanding
area of light to moderate rain showers across north central
Kansas. These showers will likely continue to expand late this
afternoon and evening as they track east across north central
Kansas and could develop into far south central Nebraska generally
south of Highway 6. There is some elevated instability with
MUCAPE values of over 1000 J/KG especially across north central
Kansas so certainly could still see a few strong to even possibly
severe thunderstorms this evening primarily across north central
Kansas, but do not believe strong thunderstorms will be very
widespread if they do develop.
Thunderstorm activity even over our more favored Kansas counties
should gradually decrease and/or move out by late evening into the
late night hours. RH values have been high all day and there is a
lot of low level moisture around the area. Consequently, with
overnight cooling, light winds, and moist conditions expect we
could see at least some patchy fog around the area. We might even
have to watch out for patchy dense fog.
Friday...A sfc high will slide off to our east into Iowa and our
winds will gradually transition from light and variable or light
easterly, to more southeasterly or even southerly winds as we
head through the day. We also expect much more in the way of
sunshine and thus a warmer day with highs back into the mid and
upper 80s. Can not rule out an isolated shower or thunderstorm
primarily in the morning across our north central Kansas counties,
but overall most areas should remain dry.
.LONG TERM...(Friday night through Thursday)
Issued at 319 PM CDT Thu Jul 13 2017
Saturday through Wednesday...We will be under the influence of a
large upper level area of high pressure that will slide east out
of the western United States and into the plains. This will likely
result in several days of hot and dry conditions. Highs should be
at least in the 90s most of this period and could even see some
100 plus days.
Wednesday night into Thursday...There is some indication that we
could see a weak upper level wave dampen the upper ridge bringing
with it a cool front and some chances for rain. However,
confidence this far out is low and the forecast model signals are
weak, but if you are hoping for rain this would be the period to
watch.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 712 PM CDT Thu Jul 13 2017
General overview:
For the first time in a few days, confidence is rather high in
rain/thunderstorm-free weather at both sites. Instead, the
attention turns to increasing signals for fog development late
tonight/early Friday.
Visibility/ceiling:
As for visibility/fog potential, confidence is quite high in
continued VFR through these first 6 hours and then again during
the final 9 hours during the day Friday. However, those middle 9
hours or so from late tonight into mid-morning Friday appear to
setting up increasingly-ripe for some relatively "rare"
appreciable fog formation by July standards. Several factors play
into this, including light winds and high boundary layer moisture,
enhanced by the fact that both KGRI/KEAR received roughly 1.50" of
"fresh" rainfall in the past 24 hours. Would normally be a bit
hesitant to introduce a TEMPO for IFR visibility beyond the first
9 hours this time of year, but will go ahead and do so at this
time, especially considering that some guidance is suggesting
outright-dense fog with VLIFR potential. As for ceiling,
obviously if dense fog develops that will become a major morning
issue as well, and it`s possible that even a scattered to broken
IFR/MVFR deck could hold on well into the morning while/after fog
dissipates. With confidence lower in ceiling trends, will leave
this VFR at least for now.
Surface winds:
Even by mid-summer standards, the period will feature rather light
winds, with speeds largely at-or-below 7kt and direction ranging
from variable/near-calm overnight to east-southeasterly during the
day Friday.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
UPDATE...Pfannkuch
SHORT TERM...Wesely
LONG TERM...Wesely
AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1039 PM EDT Thu Jul 13 2017
.SYNOPSIS...
Hot and humid conditions will persist into the weekend, with
scattered to numerous afternoon and evening thunderstorms each
day. A cold front will move into the region from the northwest
on Saturday and stall in or near the area through Sunday.
Another cold front will approach on Monday and move southeast
of the area on Tuesday, with drier conditions arriving by the
middle of next week.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 1030 PM EDT: So far this evening, the HRRR had the right idea,
but was overdone. Only one storm left in the CWFA, persisting over
the SC mountains. I expect activity to wane. However, during the
overnight, a slight increase in WSWLY 850 mb flow and lingering
elevated CAPE warrants at least a slight chc PoP thru the night in
the western and southern NC mountains. Otherwise, expect gradual
dissipation of debris cloudiness across the CWFA with fog developing
in the NC Mountain valleys and perhaps the northern NC Foothills.
Temps look on track to bottom out near to slightly above normal.
As we move through the near-term, the western cutoff and upper
trough will work east toward Quebec, pushing the front through the
OH Valley. The Southeast upper ridge will break down somewhat and by
the end of the period the front will be working its way across the
area, weak though it may be. Should see increased convective chances
by Friday afternoon (though still with the max over the mountains)
and with the elongated area of upper vorticity approaching as well,
the Day2 Marginal Risk for the northern tier seems warranted as mid-
level lapse rates should improve leading to a low-end wind threat.
Besides the convective activity, above-normal temperatures remain
the concern. Really we`re only talking a couple of degrees above
seasonal normals, though with dewpoints hovering around 70 across
the Piedmont, but pooling into the mid 70s toward the foothills,
heat indices will continue to flirt with the century mark, with a
few locations sneaking above it. Still a few degrees below heat
advisory criteria but worth taking standard heat safety precautions
nonetheless.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 210 PM EDT Thursday: Heights fall slowly but steadily through
the weekend as a trough builds over the eastern CONUS. A weak short
wave drops into the trough and crosses the area Saturday while a
stronger, but still relatively weak, short wave does the same on
Sunday. A weak cold front moves in from the NW Friday night and
stalls across the area on Sunday. The front weakens Sunday as it
slowly moves into the southern portions of the CWFA. Upper level
divergence increases as the right entrance region of the an upper
jet slides south into the area. These features will provide more
forcing for convection than the previous few days. Instability
remains moderate to very high both days but will be on the downward
trend. Shear increases with the short waves but remains below 30
kts. There will be less mid level dry air as well with an increase
in deep layer moisture and PW values near 2 inches. Although, DCAPE
values remain relatively high. Therefore, expect better coverage of
convection CWFA wide Saturday with a focus across the southern CWFA
for Sunday. Severe storm chances will be similar with a marginal
threat CWFA wide Saturday and the threat shifting to the southern
CWFA on Sunday. The heat begins to abate with falling thicknesses
for the weekend. The highs Saturday will be closer to normal but
high humidity will put heat index values near 100 along and south of
the I-85 corridor. Temps fall below normal for Sunday but heat index
values linger in the 90s. Lows remain above normal but with a
cooling trend.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 205 PM EDT Thursday: the extended fcst picks up at 00z on Monday
with a positively tilted upper trof digging down across the Great
Lakes and broad upper ridging persisting across the western 2/3 of
the CONUS. Over the next couple of days, the upper trof axis will
move over the fcst area as the ridge gradually expands eastward.
Beyond this point, the long range models diverge wrt the trof. The
GFS tries to cutoff the trof over the CWFA on Wed and keep the ridge
from advancing into the fcst area. The ECMWF, on the other hand,
moves the trof offshore and spreads the ridge over the area on Wed
and Thurs. At the sfc, a reinforcing cold front will move over the
fcst area on Monday and stall just to our south before dissipating
on Tuesday. As we go into mid-week, high pressure strengthens to our
NW and moves over the region to end the period. As for the sensible
fcst, no significant changes were made with solid chances for
widespread diurnal convection over the CWFA on Monday and slight to
solid chances for Tues. Wed should be quieter with the center of
the sfc high just to our north. Temps are also expected to start out
right around normal and slowly climb thru the period, yet they are
not fcst to reach heat advisory criteria at this time.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
At KCLT and Elsewhere: Convection continues fire across portions of
the NC mountains and along outflows in the southern NC piedmont.
Will go with VCTS for the first couple hours of the KAVL/KHKY/KCLT
TAFs due to the activity nearby. Overall, I expect convection to
wane after sunset like last night. However, the latest HRRR shows
activity ramping back up across the western Upstate and NE GA. At
the time of TAF issuance, there were a couple of storms developing
along outflows about 20 miles north of KGSP. Perhaps these outflows
can continue to trigger new storms as they drift south and west.
Confidence is still too low despite the HRRR. So I will leave the TS
mention out of the Upstate sites for now. Otherwise, the overnight
should become mostly clear, except for valley fog developing again
in the NC mountains. I will hit LIFR conditions harder at KAVL, due
to some heavy rain that just fell (Temp and dewpt were 72 deg at
time of this writing). Fog will also be possible at KHKY due to rain
falling there. I expect VFR conditions elsewhere. For Friday, a cold
front will be approaching from the north. Guidance in decent
agreement that the NC TAF sites will see the greatest coverage
during the aftn hours. So will have PROB30 groups for those sites,
but leave out of the Upstate sites for now.
Outlook: Scattered to numerous afternoon and evening convection is
expected each day through Monday across the area, with higher
coverage in the mountains. Morning fog development can be expected
in mountain valleys and areas that receive rainfall in the previous
afternoon.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 100% Med 68% High 100% High 100%
KHKY High 100% High 100% High 100% High 100%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 100% High 100% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...JPT
NEAR TERM...ARK/TDP
SHORT TERM...RWH
LONG TERM...JPT
AVIATION...ARK
Area Forecast Discussion
National Weather Service Lincoln IL
918 PM CDT Thu Jul 13 2017
.UPDATE...
Issued at 900 PM CDT Thu Jul 13 2017
A cold front has slipped just south of the forecast area over the
past couple of hours, per surface wind shift and main instability
axis, but temperatures and humidity levels are in no hurry to
fall off to the north of the boundary. Of course, this is not
surprising considering how weakly forced the front is. Convection
continues to fire along the very slow moving frontal boundary
along the persistent instability axis, aided by weak short waves
within the westerly flow aloft. Most of forecast area should
remain dry through the rest of the night, but our counties
along/south of the I-70 corridor may still see scattered showers
or storms for several more hours.
Updated forecast for the expected overnight trends, primarily to
freshen up the latest thinking on PoP trends.
&&
.SHORT TERM...(This evening through Friday)
ISSUED AT 237 PM CDT Thu Jul 13 2017
Cold front is edging across the far northern CWA early this
afternoon, with dew points down into the upper 60s. Southeast CWA
features dew points in the upper 70s to around 80 degrees. The
earlier convective line that formed just south of Lawrenceville
resulted in briefly cooler conditions, but heat index values
mainly in the 100-105 range at this point. Will let the heat advisory
south of I-70 continue until its 6 pm expiration.
Still quite a bit of cloud cover across the forecast area this
afternoon, but CAPE`s still have managed to reach around 2000 J/kg
near I-72 and over 4000 J/kg south of I-70. Latest HRRR shows
thunderstorms on the increase during the mid afternoon and
tracking southeast. Shear is not especially impressive, generally
at most around 30 knots in the 0-6km level, so any stronger storms
that manage to form should be more pulse type. The boundary will
not be quick to exit, as it starts to hang up a bit with the
west-east flow aloft over Illinois tonight, so will keep rain
chances in southeast Illinois past midnight. However, high
pressure building in from the northwest on Friday will result in
dry conditions across the area.
.LONG TERM...(Friday night through Thursday)
ISSUED AT 237 PM CDT Thu Jul 13 2017
Much of the weekend will see our area in a northwest flow, as the
upper ridge across the western U.S. remains strong. With time, it
will edge eastward, with a shortwave riding southeast along the
periphery of the ridge. This will mainly impact the Great Lakes
region, though a few storms will be possible this far southwest on
Sunday as the front drops through. Have kept PoP`s limited to the
20-30% range with this boundary.
In the longer term, the heat dome will be building eastward next
week as the top of the ridge starts to flatten. High temperatures
expected to return to the 90s on Wednesday and Thursday, and went
a bit above the blended model guidance for highs during this time.
The ECMWF model keeps us dry as the strong upper high moves
overhead, while the GFS keeps us on the periphery of the ridge and
thus keeps us near the path of any potential MCS tracks mid week.
This discrepancy will shake itself out with time, but for now will
mainly limit any PoP`s to the northern CWA at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 648 PM CDT Thu Jul 13 2017
Quiet/VFR aviation weather conditions expected across the central
Illinois terminals through the 00Z TAF valid time. High pressure
and a drier air mass will start to build into the area tonight,
providing little significant cloud cover and generally light
winds.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Bak
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Bak
Area Forecast Discussion
National Weather Service Louisville KY
801 PM EDT Thu Jul 13 2017
.Mesoscale Update...
Issued at 800 PM EDT Thu Jul 13 2017
A line of strong storms is moving in slowly from the northwest,
generally toward southern Indiana counties west of I-65. These
storms will likely weaken gradually over the next 1-2 hours, but
there is a brief window with some potential for strong winds,
torrential rainfall, and lightning in southern Indiana.
23z SPC mesoanalysis shows 2500-3000 J/kg MLCAPE over the northwest
CWA, including Dubois/Orange counties in Indiana down through
Hancock County, KY. DCAPE is still around 1000 J/kg, which will
enhance downward momentum transfer in stronger cores. Mid and upper-
level winds are very weak, resulting in little vertical wind shear.
These storms are particularly reliant on diurnal heating, so
weakening trend is likely to accelerate toward sunset and after.
&&
.Forecast Update...
Issued at 520 PM EDT Thu Jul 13 2017
Radar is quiet for most of the CWA this evening, but a few scattered
showers/storms have popped up near Bowling Green and southwest of
Tompkinsville. These pulse storms could generate some brief heavy
rainfall and lightning before diminishing closer to sunset. An
outflow boundary has washed out across northern KY, draped from
Hancock County over to Franklin County. Visible satellite imagery
shows little growth along this feature, so capped PoPs at slight
chance through 00z.
Meanwhile, convection has been much more vigorous along the cold
front, currently draped across central Indiana/Illinois. An axis of
moderate instability (MLCAPE > 2500 J/kg) exists from central to
southwest Indiana. These storms are likely to be strongest north of
the CWA. A weakening trend is expected as they enter our southern
Indiana counties after 00z. Deep layer shear remains very weak, and
the storms will wane with the loss of heating. Still, could see some
lightning and gusty winds later this evening before the storms
diminish altogether.
&&
.Short Term...(This evening through Friday night)
Issued at 310 PM EDT Thu Jul 13 2017
Hot and humid conditions prevail across the lower Ohio Valley with
regional observations showing temperatures in the upper 80s to lower
90s. Moisture pooling ahead of an approaching cold front has put
dewpoints in the lower to middle 70s. This heat and high moisture
has created heat indices in the upper 90s to lower 100s this
afternoon.
Earlier storms initiated across southwest into south central Indiana
in a high instability zone characterized by SBCAPE of nearly 3000
J/kg. A recent RAP mesoanalysis also shows very high values of DCAPE
of 1200-1400 J/kg which has allowed just marginal looking storms to
put down isolated 40 to 50 mph wind gusts as storms collapse. Storm
organization is very weak as there is little deep layer wind shear
to work with, especially south of the Ohio River. This will keep
storms very pulse in nature. The strong storm threat will continue
for a few more hours before dissipating with loss of peak heating.
Heavy rainfall will remain a concern given the high PWATs (1.7 to
1.9 inches), slow storm motion, and high freezing levels/warm cloud
depths.
For the remainder of the afternoon and evening, leaned heavily on
the HRRR which seems to be capturing the latest radar trends the
best. As outflow from earlier storms moves in central Kentucky,
isolated to perhaps scattered storms may initiate along this
boundary. Additional storms may develop along the cold front across
central Illinois and central Indiana and drop south/southeast.
Meanwhile, current pop-up showers and storms across the Lake
Cumberland region will remain across portions of south-central and
eastern Kentucky through late afternoon but with loss of heating,
should subside. As such, went with a mainly dry evening and
overnight across south-central Kentucky while maintaining 20-30
percent chances along and north of the KY Parkways.
Plan on very muggy and mild conditions tonight with lows staying in
the 70s.
The front will slip down into central Kentucky tomorrow and another
round of scattered showers and storms are likely to develop across
south-central Kentucky and parts of the Bluegrass. A similar setup
with high instability, low shear in an environment supportive of
pulse, quick downburst of strong wind gusts possible. The marginal
risk looks good across Kentucky. Plan on highs in the 80s. Storms
will continue into parts of the evening hours near the TN border
before slowly ending overnight into Saturday morning.
.Long Term...(Saturday through Thursday)
Issued at 310 PM EDT Thu Jul 13 2017
High pressure originating out of the Upper Midwest will begin to
work down into the lower Ohio Valley Saturday and Sunday. This will
bring a couple of days of lower humidity and some relief from the
hot and humid weather this week. Plan on highs in the 80s with lows
in the 60s to around 70. Dewpoints will stay in the more comfortable
range.
Another weak front will approach the area late Sunday night and
Monday. There remains some timing differences between the global
models, so for now will just mention a slight chance mainly across
southern Indiana and north central Kentucky.
The remainder of the long term /Tuesday to Thursday/ at this time
looks dry as upper level ridging builds in. Overall, near to
slightly above climo temperatures are expected.
&&
.Aviation...(00Z TAF Issuance)
Issued at 735 PM EDT Thu Jul 13 2017
VFR TAFs are forecast however the timing of t-storms near or at the
TAF sites for this forecast period will be a challenge. Current
thinking is that SDF/BWG/LEX are pretty much done with convection or
have a very minimal chance for this evening. The bigger complex of
storms over central IN should dissipate as it slowly moves south
late this evening. Looks like then next chance for showers/storms
will be a small one as a cold front pushes southeast through the
region late tonight into tomorrow morning. The front may linger
over south central KY and may curve back NE toward the Bluegrass
tomorrow afternoon resulting in better chances for showers/storms at
BWG tomorrow afternoon and to a lesser extent LEX. Winds should
remain SW until tomorrow afternoon behind the front where they`ll
veer WNW.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Mesoscale...EBW
Update...EBW
Short Term...ZT
Long Term...ZT
Aviation...AMS
Area Forecast Discussion
National Weather Service Memphis TN
809 PM CDT Thu Jul 13 2017
.UPDATE...Evening Update.
Forecast is in good shape. Showers have largely dissipated across
the Midsouth with the exception of a few in North Mississippi.
Adjusted pops accordingly. We may see additional development as a
cold front approaches...although the HRRR is not particularly
bullish with this development. Tomorrow...as temperatures warm and
the atmosphere destabilizes most if not all of the Midsouth
should see some rainfall. For many any places it will be the first
rain in over a week.
30
&&
.DISCUSSION...
&&
.PREV DISCUSSION... /issued 626 PM CDT Thu Jul 13 2017/
Showers and thunderstorms are ongoing across southeast portions
of the FA this afternoon. Temperatures have climbed into the lower
90s at most locales, with winds calm to light from the south.
Latest surface analysis depicts a surface front just to the north
of the region, currently stretched across central Illinois, with
surface high pressure behind this feature extending over the
northern Plains.
Showers and thunderstorm activity across NE Mississippi and parts
of W Tennessee will gradually diminish this evening after sunset.
The front will push south toward the region, becoming a focal
point for convection over the next couple of days. A few strong to
severe thunderstorms will be possible late tonight through
Saturday as a result. Gusty winds and heavy rainfall will be the
primary threats with these storms. The greatest likelihood on
Friday for storms will be areas along and north of Interstate 40
over W Tennessee and E Arkansas. Highs on Friday will be in the
lower 90s.
The front pushes further south by Saturday, with POPs greatest
across N Mississippi during the day. Under the influence of the
front, highs will be a couple of degrees cooler on Saturday
afternoon. Surface high pressure begins to build into the region
from the north by Sunday, with the front washing out over southern
portions of the FA by the end of the weekend keeping chances for
showers and thunderstorms the greatest there.
An upper ridge of high pressure begins to build into the region
early next week, allowing for drier conditions through midweek,
with POPs secluded to portions of N Mississippi. Temperatures
will also be on a gradual warming trend, returning to the mid 90s
by midweek.
ZDM
&&
.AVIATION...
00Z TAFs
VFR this period with decaying showers early...than redevelopment
of convection late. Better chances for storms on station may
arrive at the very end and just beyond this period. Light
southwest through west winds are expected.
JAB
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
954 PM EDT Thu Jul 13 2017
.DISCUSSION...
A few isolated showers may linger in the area overnight with a
moist air mass in place and residual boundaries from earlier
convection. The HRRR is aggressive in developing precip after
06Z, but it seems overdone. The slight chance PoP that is
currently forecast overnight seems on track. Adjustments will be
made to hourly temperature grids to bring them in line with
current obs, otherwise no major changes are planned.
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...None.
VA...None.
&&
$$
DGS
Area Forecast Discussion
National Weather Service Paducah KY
631 PM CDT Thu Jul 13 2017
.UPDATE...
Issued at 627 PM CDT Thu Jul 13 2017
For aviation section only.
&&
.SHORT TERM...(Tonight through Saturday night)
Issued at 433 PM CDT Thu Jul 13 2017
Most of the morning shower and thunderstorm activity was forming
within southwest to northeast axes of higher theta-e air, combined
with subtle low to middle level shortwaves, aiding in overturning
of parcels. Given the low to mid level shear (<20 knots),
efficient transport of parcels for updraft/downdraft interactions
has been marginal, leading to outflow dominated storms.
Anticipate the pre-frontal convective activity over the northern
1/3 of MO and across central IL will continue to persist into the
evening hours, moving once again into the WFO PAH forecast area.
Diurnal convection, associated with differential heating from
earlier outflows from earlier storms, will continue to develop
this afternoon, especially in areas where the thermal cap is the
weakest (mainly over Southern Illinois). In the absence of the
approaching cold front and transient shortwaves traveling along
the slowly descending baroclinic zones, it will be hard to
maintain any convection across the southern 1/3 of the WFO PAH
forecast area this afternoon and early this evening. SPC`s
transition back to a Marginal Risk area (similar to their original
Day 3 outlook) may have been a prudent move.
Convection allowing models, as well as intermediate and medium
range model guidance, have had trouble resolving the effectiveness
of the thermal ridging aloft. This may be also due to variations
in model parametrization of precipitation schemes.
For now, have utilized blended guidance with an emphasis toward
the RAP and NAM-WRF model family guidance. While it is not the
most elegant solution for rain chances tonight into Friday, the
goal was to highlight the transition from north to south the
movement of rain chances through the WFO PAH forecast area
overnight into Friday. Until ridging builds in behind the
baroclinic zone Friday into Saturday, still need to leave a small
chance of precipitation in the area, mainly over southeast
Missouri.
For the rest of the sensible weather elements (temperature,
dewpoint, wind, etc...) started with a regional model
initialization, then leaned the gridded forecast output closer the
the NAM-WRF model suite.
.LONG TERM...(Sunday through Thursday)
Issued at 433 PM CDT Thu Jul 13 2017
The medium range models were in reasonable agreement in their mid
level flow pattern solutions in the extended forecast period, though
there were still smaller scale differences such as pcpn patterns and
the strength of the expanding ridge. We will start out with a
western ridge/eastern trof pattern initially.
Shortwave energy in the initially amplified pattern is progged to
swing through the Midwest, including the Great Lakes, during the
weekend and Monday. As this occurs, a weak, "backdoor" type surface
front is more or less progged to enter the PAH forecast area from
the northeast and eventually dissipate. We will continue to have a
warm, rather moist and unstable airmass in place, and this boundary
may act as enough of a trigger for a few showers or tstms to develop
north of I-64 on Sunday night, and across parts of the Evansville
Tri-State region Monday.
Further out in time, the aforementioned western ridge is progged to
expand eastward, with greater influence on the PAH forecast area.
Due to primarily the GFS pcpn fields, the initialization blend
contained "bullseyes" of PoPs, which seemed unlikely compared to the
CMC/ECMWF solutions and all that warm air aloft. In that spirit, we
collaborated with surrounding offices and WPC to go somewhat above
guidance with lows and highs next week. Heat indices of 100-105
should be common on Wed/Thu (Day 6/7) as deep moisture increases.
&&
.AVIATION...
Issued at 627 PM CDT Thu Jul 13 2017
A rather convectively complicated forecast for the WFO PAH 00z
TAF issuance. Current outflow dominated thunderstorms have
necessitated the use of vicinity thunderstorm mention in some
cases. Where the forecast signal was the strongest for the
Thursday afternoon and evening convective activity, MVFR
visibilities due to rain and low VFR ceilings were utilized.
As we head toward sunrise, MVFR ceilings/visibilities were used
with the approach of the cold front through each of the TAF
locations. Timing was a little more difficult to assess for the
onset and duration of the lower ceilings, owing to the variability
on the movement of the cold front at different TAF locations.
Thinking conditions may become low VFR as we get toward noon.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
UPDATE...GM
SHORT TERM...Smith
LONG TERM...DB
AVIATION...GM