Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/30/19
Area Forecast Discussion
National Weather Service Quad Cities IA IL
539 PM CDT Thu Aug 29 2019
...00z AVIATION UPDATE...
.SYNOPSIS...
Issued at 236 PM CDT Thu Aug 29 2019
As of 230 PM, a few showers and isolated storms, leftover from
the morning convection, were located between Fort Madison and
Macomb. This activity will continue to weaken through the mid
afternoon.
Synoptically, a cold front stretched from NE Wisconsin toward
Dubuque and then into south-central Iowa. This wind shift was
apparent on visible satellite imagery as a narrow band of
stratocumulus with embedded gravity wave features and was moving to
the southeast. Also of note, there was a lack of agitated cumulus
across Iowa and Illinois. Further south, into northern Missouri,
a remnant outflow boundary from the morning round of storms was
serving as a focus for deeper convection early this afternoon
(south of the CWA).
Low-level moisture return has been significant today on southwest
winds with dewpoints reaching into the mid 60s to around 70 F.
Temps have been held down across the south where the earlier
complex of storms brought heavy downpours and widespread cloud
cover. In this area, early afternoon temps were still in the mid
70s.
&&
.SHORT TERM...(This Evening through Friday)
ISSUED AT 236 PM CDT Thu Aug 29 2019
Late This Afternoon into Tonight
SPC has maintained the Slight risk for severe storms over the SE
two-thirds of the forecast area. Trends in surface and satellite
observations and the latest hi-res models suggest relatively low
storm coverage across our CWA into tonight. The stronger than
expected morning storm complex may have had an effect on the
magnitude of low-level convergence that was anticipated across
central sections of the area this afternoon/evening. It also led
to slow temp recovery and lower surface-based instability in the
south. For these reasons, and based on consensus of the 12Z HREF
members, it seems the most likely scenario for redevelopment
would be across the south (along and south of highway 34). Yet
this is even a low confidence outcome because the remnant outflow
boundary has pushed to our south and southwest into north-central
Missouri.
The HRRR is the furthest south of the hi-res models with the
convective redevelopment holding off until this evening near our
southern border. But with the environmental setup of 2000-3000 J/kg
surface-based CAPE and 40+ kts of effective shear, a few severe
storms remain possible into early tonight. The main threats are
localized damaging winds and large hail. The tornado risk remains
very low at 2% per SPC`s outlook.
Friday
The northern fringes of a complex of rain and thunderstorms could
clip the far south from the mid morning into the afternoon, with
the brunt of this activity remaining into central Missouri. Have
slight chances for rain and thunder along and south of highway 34
(west of Galesburg). Otherwise, for most of eastern Iowa and
northwest Illinois, it will be a nice day with highs in the 70s.
Uttech
.LONG TERM...(Friday Night through Thursday)
ISSUED AT 236 PM CDT Thu Aug 29 2019
Initial concern is the potential for rain and much below normal
temperatures over the first half of Labor Day weekend. A warming
trend is then likely going into next week with periodic systems
bringing low chances for rain.
The front making its way through the forecast area in the short term
is expected to stall out in a west to east orientation from the
Central Plains through the mid Mississippi Valley region Friday
night. A series of mid level shortwaves are expected to interact
with this baroclinic axis to spread rain along and north of the
boundary, possibly affecting the forecast area Friday night into
Saturday.
12Z models remain in poor agreement with just how far north any rain
reaches, with the WRF/NAM now virtually dry over the forecast area
through the weekend, while the ECMWF has nearly 1 inch of rain
across our south through Saturday night. The GFS and Canadian are in
between, with mostly light amounts, focused across the south. For
now, the forecast maintains at last low chances for showers
overspreading the south and southwest late Friday night with
isolated thunderstorms. Rain chances Saturday are still higher in
the south, but limited to moderate pops with QPF likely well below a
quarter inch. Of possibly greater consequence for the start of the
holiday weekend will be the cool temperatures due to extensive cloud
cover and low level easterly flow out of the Great Lakes high. Lower
dewpoints will lead to overnight lows in the 50s to lower 60s, while
Saturday`s highs may only range from around 70 north to lower 70s
south. The passage of an inverted trough Saturday night will be
followed by rebounding high pressure, favoring a dry Sunday with at
least partial sunshine. This should drive highs back into the mid to
upper 70s.
Rising 500 mb heights and the northward returning warm front will
produce a warming trend for Monday going into Tuesday, driving highs
back into the 80s. Low pops are kept for late Tuesday into Tuesday
night, when the boundary may drift back southward across the area.
This is followed by highs returning back to the 70s for Wednesday and
Thursday, where there is another potential for showers and
thunderstorms with the next cold frontal passage.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
ISSUED AT 538 PM CDT Thu Aug 29 2019
VFR conditions to persist at the terminals through the period in
the wake of a cold frontal passage, and as high pressure builds
in. Gusty westerly winds 10-20+ kts will diminish below 10 kts
tonight while becoming northerly.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SYNOPSIS...Uttech
SHORT TERM...Uttech
LONG TERM...Sheets
AVIATION...McClure
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
634 PM CDT Thu Aug 29 2019
.AVIATION...
All terminals are VFR and will remain that way through the evening.
MVFR ceilings will develop in Austin and San Antonio overnight, but
will only last for a few hours. They should rebound to VFR by around
sunrise. DRT will be VFR through the entire period. Winds will be 10
kts or less from the southeast.
&&
.PREV DISCUSSION... /ISSUED 247 PM CDT Thu Aug 29 2019/
SHORT TERM (Tonight through Friday Night)...
The weather remains fairly quiet across South-Central Texas at the
present hour. Skies are mostly clear across much of the area with a
cumulus field across the eastern CWA. The vertical extent of the cu
remains poor but latest runs of the HRRR continue to show some
initiation of some showers and perhaps a thunderstorm around 3 pm and
the current forecast handles this well. Most if not all of the
activity should be diminished by 7 pm and did not mention any PoPs
in the tonight period. Otherwise, lows tonight will be in the lower
to middle 70s for most areas.
The region will remain in a weakness aloft and additional isolated
showers and storms will be possible tomorrow mainly across the the
eastern half of the area in the afternoon. Highs tomorrow will be
similar to that of today with highs in the middle to upper 90s. Some
locations will likely flirt with the century mark once again.
Tomorrow night is expected to be quiet with lows once again in the
lower to middle 70s.
LONG TERM (Saturday through Thursday)...
Low rain chances will linger across portions of the area Saturday but
things should dry out for Sunday as upper heights rise as the ridge
slightly builds back in. The ridge is then expected to break down
again by Tuesday and this will allow for low chances of rain to
return to the forecast. Temperatures in the extended will remain
above normal with highs in the middle 90s to 103 degree range. Lows
will remain in the lower to upper 70s.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 76 97 75 97 74 / 10 20 - 20 -
Austin Bergstrom Intl Airport 75 96 74 96 74 / 10 20 - 20 -
New Braunfels Muni Airport 74 96 73 95 72 / 10 20 - 20 -
Burnet Muni Airport 74 95 72 94 72 / 10 20 - 20 -
Del Rio Intl Airport 76 102 76 99 75 / - 10 - 10 10
Georgetown Muni Airport 75 97 74 96 74 / 10 10 - 20 -
Hondo Muni Airport 74 100 73 99 72 / 10 - - - 20
San Marcos Muni Airport 74 97 73 96 72 / 10 20 - 20 -
La Grange - Fayette Regional 76 98 75 97 74 / 10 30 - 20 -
San Antonio Intl Airport 76 97 76 96 74 / 10 20 - 10 10
Stinson Muni Airport 76 97 76 96 74 / 10 10 - 10 10
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Aviation...05
Short-Term/Long-Term...BMW
Public Service/Data Collection...EWilliams
Area Forecast Discussion
National Weather Service Goodland KS
842 PM MDT Thu Aug 29 2019
.UPDATE...
Issued at 841 PM MDT Thu Aug 29 2019
Cancelled the remainder of the severe thunderstorm watch for our
forecast area as storms have moved out of the area.
UPDATE Issued at 751 PM MDT Thu Aug 29 2019
Updated the forecast to remove the severe thunderstorms watch as
storms continue to move out of NW KS into north central Kansas.
&&
.SHORT TERM...(This afternoon through Friday night)
Issued at 1230 PM MDT Thu Aug 29 2019
Overview: WNW-NW flow aloft will prevail over the region, on the
NE periphery of an upper level ridge over the Desert Southwest.
Today-Tonight: A weak SFC-H85 cyclone centered in extreme
northeast CO at 17Z will track ESE into northwest KS this evening
as a small amplitude shortwave in southeast Wyoming (per 17Z WV
imagery and SPC Mesoanalysis) progresses ESE through southwest NE
into north-central KS. Surface observations and radar data show a
thermal/moisture boundary associated with the aforementioned
cyclone stretching SW-NE from Burlington->Saint Francis->Trenton,
extending N-NW from Trenton to Ogallala NE. HRRR simulated
reflectivity forecasts suggest that isolated convection will
develop along the SW-NE oriented TMB in northwest KS (perhaps just
S or E of Goodland) ~21-22Z this afternoon, progressing east into
central KS this evening (by ~03-04Z). Though convection may be
somewhat disorganized in nature at onset -- very steep mid-level
lapse rates (~9 C/km), 30-40 knots effective deep layer shear,
moderate to strong instability (1500-3000 J/kg MLCAPE) and extreme
DCAPE (1500-1800 J/kg) suggest a potential for isolated high-
based supercells capable of producing very large hail and
significant damaging wind, primarily in E|NE portions of the area
late this aft/eve (23-03Z) -- when flow aloft /deep-layer shear/
strengthen in advance of the approaching shortwave. Thereafter,
activity is anticipated to rapidly grow upscale and track E-ESE
across central/eastern KS.
Friday-Friday night: The convective forecast in this period will
highly depend on mesoscale features emanating from convection
developing over the region this evening/tonight (and the impact
thereof on the thermodynamic environment over), the evolution of
upstream convection over the northern Rockies (and it`s impact on
downstream height/wind fields), and small amplitude tropopause
disturbances (~250 mb level) progressing from the northern Rockies
into the Central/Northern Plains via WNW/NW flow aloft. With this
in mind -- significant uncertainty persists with regard to
when/where convection may develop, let alone convective
mode/evolution/hazards.
.LONG TERM...(Saturday through Thursday)
Issued at 200 PM MDT Thu Aug 29 2019
The main story with the extended forecast will be dry conditions and
temperatures near to above normal.
Saturday morning, the Tri-State area will be under northwest flow as an
upper ridge over the Western U.S. slowly progresses eastward
through the day. Temperatures may be hampered early in the day due
to lingering clouds and showers, particularly in the northeastern
part of the forecast area. Chances for precipitation are not
great, but cannot be entirely ruled out as a shortwave trough
exits the area. Highs are expected to be in the mid-70s to low 80s
across the region.
High pressure will become centered over the Four Corners region Sunday.
The ridge will remain over the western half of the U.S. and the
Central High Plains. Am anticipating a return to the 80s and 90s
both Sunday and Monday as southerly winds help our temperatures.
Models are showing an upper level trough coming ashore over the
Pacific Northwest Monday morning. Both the GFS and ECMWF show a
closed low developing and progressing eastward through the day. Do
not anticipate an impact in the Tri-State region to start out the
week.
May have a weak low trying to form east of the Rockies on Tuesday.
Weak convergence may be enough to kick off a stray shower or storm
Tuesday evening, but at this point in time, confidence in this is
very low. Shortwave trough may move through the region Thursday.
Did mention slight PoPs as it moves through, but confidence is low
at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 522 PM MDT Thu Aug 29 2019
The 00Z TAF at MCK will be starting out with a strong
thunderstorms moving across the site that will be moving out of
the vicinity by 02Z. Conditions will be VFR and will continue VFR
into Friday morning. After 14Z, lower clouds will spread across
the region with MVFR conditions due to lower ceilings along with
thunderstorms developing after 20Z.
GLD will be VFR through about mid day on Friday. After 17Z,
conditions will become MVFR due to lower ceilings moving in along
with thunderstorms developing after 22Z.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...LOCKHART
SHORT TERM...VINCENT
LONG TERM...AW
AVIATION...LOCKHART
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1002 PM EDT Thu Aug 29 2019
.SYNOPSIS...
Northwest flow has set up behind a frontal boundary that moved
offshore this morning. Temperatures tomorrow will actually warm
a bit over today due to abundant sunshine before another cold
front moves through tomorrow night. Temperatures will cool a bit
for the weekend behind the front before rain returns by Monday.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
10 PM Update...
Clear evening is in progress. Temperatures are dropping steadily
and made few changes to the going forecast. HRRR and NARRE-TL
show more fog possible over Augusta and Rockland areas in
addition to the Connecticut River Valleys and mountain valleys,
so have added that to the overnight forecast, generally after 3
AM.
620 PM Update...
Just a quick update to adjust temperatures. Should be a nice
night with readings in the 50s areawide and dropping dew points.
Previous discussion...
The near term tonight looks to be rather quiet. Dewpoints behind
this mornings frontal boundary haven`t really dropped too much.
This will likely result in fairly mild overnight low
temperatures in the 50s to lower 60s at the coast. Over the
mountain valleys where temperatures will drop more, expect to
see some patchy fog set up.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Valley fog over mountain valleys should burn off quickly
tomorrow morning. Weak westerly flow ahead of an approaching
cold front will allow temperatures across the region to climb
into the 70s over the mountains, to mid 80s over southern New
Hampshire. The cold front is expected to move through the region
tomorrow afternoon and evening. The front has very little
moisture associated with it and will likely pass as a dry front
through most of the area. The best chance for showers and
thunderstorms will be over the mountains, while the coastal
plain will likely stay dry. Cooler and drier air moves in behind
the front. The drier air should negate fog development Friday
night as temperatures fall into the 40s to mid 50s.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Ensemble and deterministic model solutions remain in decent agreement
on the long wave pattern through early next week. Much of the forecast
period consists of a broad low amplitude trough across the northern
third of the CONUS with the exception of the Pacific northwest. By
the end of the period...rising heights and an upper ridge over the
western two-thirds of the CONUS with an upper trough stretching
across the Great Lakes and northeast CONUS. With the mean jet
position nearby or overhead we`ll see quick day-to-day changes in
sensible weather as a series of impulses and weak surface systems
traverse the area. In the dailies...a weak trough will cross
northern and mountain sections Saturday with a few clouds and
perhaps a stray sprinkle. High pressure follows for Saturday night
into Sunday. The numericals have trended slower with the arrival
of the next system on Sunday...with that weak system arriving
with clouds and a more widespread round of convection for Sunday
night and Monday. A cold front will bring more unsettled weather
for Tuesday and Wednesday as it settles southward across the
region.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Short Term...Expect to see some IFR/LIFR cigs and vsbys over
mountain valley areas in fog tonight, while coastal locations
stay mainly VFR. VFR conditions should then dominate all
locations for the remainder of the short term.
Long Term...
Sun Night - Mon...Areas of MVFR in SHRA/TSRA.
Tue...Sct MVFR in -shra/-tsra.
&&
.MARINE...
Short Term...No flags expected.
Long Term...
Sat AM...SCAs possible outside the bays.
Mon PM - Tue AM...SCAs possible outside the bays.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR TERM...Hanes
SHORT TERM...Pohl
LONG TERM...Schwibs
Area Forecast Discussion
National Weather Service Wichita KS
633 PM CDT Thu Aug 29 2019
.SHORT TERM...(This evening through Sunday night)
Issued at 408 PM CDT Thu Aug 29 2019
Complex scenario unfolding tonight and the next couple of days. A
Flash Flood Watch has been issued.
First will be the threat of severe weather tonight across
central, south central, and southeast Kansas. Northwesterly flow
is sitting overhead and a shortwave is on its way through southern
Nebraska. Storms are expected to develop along an east-west
oriented cold front this evening along the Kansas/Nebraska border.
This cold front feeds into a weak sfc low currently near the
KS/NE/CO border. Additionally, storms have initiated along the
dryline extending south out of the sfc low and satellite imagery
shows aggravated cumulus bubbling along the front.
Very moist low levels and adequate heating today has contributed
to a very unstable environment area wide. RAP sounds show
impressive CAPE values (MU 5000, ML 4000) with very steep lapse
rates nearing 8C/km in central KS and effective bulk shear of
30-35kts. DCAPE is equally as impressive with values near 1400
J/kg and with drier midlevels and increasing PWs of 1.5 to 2
inches. Storms that come through central Kansas before being a
more linear complex will have the potential for significant hail
of 2 inches and damaging winds 60-70 mph possible.
As storms continue to grow upscale tonight expect the hail threat
to dampen some and transition to a largely wind threat for the
remainder of the night. While the threat of any tornados are low,
there is decent storm relative helicity available (130 0-1 km
SRH, 175 0-3km SRH) that could favor an isolated mesovortice in a
bowing line. These storms are expected to quickly grow upscale
into an organized MCS. Corfidi vectors would suggest this MCS
initially move toward the southeast and then take more of a
southward plunge. Meanwhile moisture transport is progged to
increase considerably overnight with a strengthening southerly
LLJ. The LLJ and better moisture transport are progged to veer
slightly with time. This may create a secondary area of
convergence along any potential outflow boundary and perhaps bring
storm coverage farther west as the MCS backbuilds. Given forecast
PWs of near 2 inches overnight expect torrential rainfall with
these storms. Due to significant rainfall potential, combined with
recent rainfall over the area, opted for a Flash Flood Watch
across the warning area (less Russell and Barton Counties). Flash
flooding and river flooding are likely and will need to be
monitored overnight.
Wherever the outflow ends up will likely be a focus for renewed
showers and convection through the day tomorrow. Several models
show lingering showers and storms across the area thus left a
decent amount of pops in the forecast for this. Confidence then
decreases somewhat for tomorrow night into early Sunday morning.
Whether or not we recover from the MCS, and again where the
outflow sets up, will impact where any convection sets up. Models
are still not in agreement and may change drastically depending
on the outcome of convection tonight. Will let the next shift
take a look at tomorrow nights-sunday convection potential. Left
QPF a shave on the drier side given uncertainty.
Ridging will try to build back in during the day on Sunday and
start to dry us out. Expect temps in the mid 80s and set up a
decent week in the extended.
.LONG TERM...(Monday through Thursday)
Issued at 408 PM CDT Thu Aug 29 2019
Expect quieter conditions Labor Dy and throughout the the
extended period. An upper ridge will be building overhead next
week leaving the area dry and under general high pressure. Expect
temperatures to remain around seasonable normal in the upper 80s
and low 90s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 627 PM CDT Thu Aug 29 2019
Main aviation concern will be overnight storms.
Cold front currently extends from southeast Nebraska into far
NW KS with a dryline extending south of KGLD. Storms have
developed over SW Nebraska and far western KS along the front and
dryline with this activity expected to continuing tracking south
with some expansion expected as the low level jet cranks up this
evening. Storms will be a good bet for most TAF sites overnight,
affecting KICT and KCNU after midnight. Damaging straight-line
winds and hail will be the main threats, along with very heavy
rainfall. By sunrise, far southern and southeast KS should be the
only areas still being affected by storms.
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 69 83 67 83 / 60 50 60 60
Hutchinson 68 82 65 83 / 60 50 70 60
Newton 68 81 66 82 / 60 60 70 60
ElDorado 69 82 67 83 / 80 70 60 60
Winfield-KWLD 68 83 67 83 / 70 60 50 60
Russell 66 79 64 83 / 50 50 70 40
Great Bend 67 81 64 83 / 50 50 70 40
Salina 68 81 66 82 / 70 50 70 50
McPherson 68 81 64 81 / 60 50 70 60
Coffeyville 70 82 69 83 / 70 70 40 60
Chanute 69 80 68 82 / 70 70 50 60
Iola 69 80 68 82 / 80 70 50 60
Parsons-KPPF 69 80 68 82 / 70 70 40 60
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from 10 PM CDT this evening through Friday
afternoon for KSZ033-048>053-067>072-082-083-091>096-098>100.
&&
$$
SHORT TERM...KMB
LONG TERM...KMB
AVIATION...RBL
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
949 PM EDT Thu Aug 29 2019
.SYNOPSIS...
High pressure over the Tennessee Valley will give way to a
weakening cold front dropping south into the Ohio Valley later
tonight and Friday. A few showers and storms may accompany the
front into portions of northern Indiana and Ohio tonight, and
again on Friday afternoon and evening in southern Ohio and
Indiana. Humidity will be more noticeable on Friday along and
ahead of the front, with cooler and drier air spreading into
northern Ohio behind the front. The front will stall and wash
out near the Ohio River Friday night with weak disturbances
shifting through the Great Lakes over the weekend keeping small
chances of showers and storms in the forecast.
&&
.NEAR TERM /THROUGH FRIDAY/...
As the daytime hours have come to an end, FEW/SCT cumulus clouds
have largely dissipated, with generally clear skies setting in
over much of the ILN CWA. As the next few hours progress,
however, this inactive pattern will begin to change. At the
surface, a front is moving south through Michigan. Aloft,
westerly winds are beginning to increase in magnitude. The first
change this is leading to is an increase in mid level clouds
across northern Indiana and western Ohio. As the night
progresses, dissipating showers (leftover from the convection
over Michigan) may reach the northern sections of the ILN CWA,
prompting the continuation of the 20-PoP. Eventually, some low
level clouds may also thicken up in this area going into
tomorrow morning.
Temperatures will be dependent on the wind and cloud situation,
but this is clearly favoring warmer temperatures in the
northwestern CWA, and better radiational cooling in the
southeastern CWA. With KPMH already down to 61 degrees, min
temps had to be lowered by a bit in the far east and southeast,
accounting for current observational trends.
Previous discussion >
Afternoon visible satellite imagery shows just a few fair
weather cumulus over the forecast area with light-moderate
southwesterly flow as low level warm advection has commenced on
the backside of Tennessee Valley high pressure. A plume of dense
cirrus /convective debris/ was over Illinois drifting southeast,
and a broken line of storms along a sharp cold front continued
to be maintained across eastern Wisconsin. GOES-East water vapor
loops clearly showed the parent shortwave trough crossing Lake
Superior, accelerating ahead and away from the cold front which
was sagging southeast toward lower Michigan.
Thinking has cleared /somewhat/ on upstream convective evolution
and rain chances for tonight. Earlier /29.00Z/ CAMS and longer
lead HRRR runs had hinted that convection in eastern WI would
intensify this afternoon/evening into lower Michigan and build
quickly south into northern Indiana, before weakening as it
spilled into the ILN CWA later this evening in west-central
Ohio. The 29.12Z runs have shifted away from this thinking /and
more in line with what the mass fields had suggested all along/
that the convection now in eastern WI would continue
east/southeast into western lower Michigan where it will
gradually weaken as it builds southeast toward Detroit/Toledo.
Farther back to the southwest in western Illinois and northern
MO, a robust MCS will develop and sag southward. As the parent
shortwave trough pulls more northeast with time into southern
Canada, the front will begin to slow as it approaches the ILN
CWA toward sunrise. A rather decent low level jet /40kts at
2kft/ out of the west-southwest will cross the area overnight as
the front approaches. There may be just enough isentropic ascent
for parcels to reach an elevated LFC over our northern counties
after midnight, but the low level jet isn`t overly convergent in
our forecast area, and moisture transport magnitudes will be
decreasing in time. Thus, maintained low overnight rain chances
in the far northwest/north part of the ILN forecast area for any
showers which can develop in this regime. A much milder night is
expected with lows only falling back to the lower and middle 60s
owing to continued low level theta-e advection on the inbound
low level jet and slightly disturbed nocturnal boundary layer.
&&
.SHORT TERM /FRIDAY NIGHT/...
Friday is a little complex. Out of the large MO MCS overnight
will evolve a rather defined MCV/vort max that will begin to
drift only very slowly east with time given it will be well
displaced south of the faster westerlies well to the north. The
cold front entering the I-70 corridor in the morning will
continue to slow as heights begin to rise both in response to
large scale ridging building over the southeast CONUS, and
downstream of the MCV over MO. The front will still represent a
rather marked moisture gradient despite it really starting to
decay /frontolysis/ as it sags underneath larger scale height
rises.
After a morning/early afternoon of scattered mid/high clouds
from overnight convection to our west/north, the front will sag
into southern Indiana and Ohio with a modest low level
instability plume along/ahead of it as upper 60s dewpoints
spread in along its length. Forecast soundings are largely in
agreement of about 1000 j/kg of MLCAPE, with steep low level
lapse rates but rather meager lapse rates aloft owing to the
larger scale height rises. While low level flow will be very
weak only slightly confluent/convergent in vicinity of the
boundary, there should be enough push to the boundary and
instability at peak heating to spark scattered showers and
storms between 4P and 8P in a rather narrow corridor along the
front.
Where this occurs is in question - many of the 29.12Z CAMS/HREF
members suggest this corridor will be on a
Hamilton/Wilmington/Chillicothe corridor and then sagging slowly
south. The 29.12Z NAM/ECMWF/ARW WRF are - and have been -
consistent in being very limited on convective development in
comparison through the evening with only the ECMWF showing some
scattered storms mainly over southern Indiana into extreme
northern Kentucky /the furthest south solution/. From purely a
consensus/ensemble of a large number of models approach - the
further north solution has the most support /and also from a
standpoint of a slowing front into height rises/. So have
focused the best rain chances near the GFS/CMC/HREF/CAMs mean
frontal position which is little further north than NAM/ECMWF
consensus. This is the same axis as previous shifts. But - to
account for uncertainty - the forecast rain chances are much
broader than what would otherwise be forecast if there were
higher confidence on frontal location. Kept chances around
30-35%.
Hazard assessment - the instability axis /regardless of its
exact latitude/ will lie on the southern fringe of stronger
westerlies over central/northern Ohio. Forecast soundings at
CVG/ILN on Friday at 21Z-00Z suggest effective shears around
25-30kts, meager mid-level lapse rates, modest DCAPE and delta-
theta-e values. Given an overall marginal
thermodynamic/kinematic profile - think storms will largely be
sub-severe, especially considering low level shear values are so
weak and thus outflows will tend to undercut the updrafts rather
quickly. If there were a damaging wind report or two, would
think southeast Indiana would be most primed owing to a little
better instability the further west you go.
Once the threat for diurnally enhanced/frontally forced
convection wanes by mid-evening, attention then turns to the
approaching MCV later in the night. Upcoming forecasts may need
to increase rain chances again later in the night in eastern
Indiana/western Ohio as this features slowly moves close and
increases flow to the point that some elevated showers develop
toward daybreak near the Indiana/Ohio border, but not enough
confidence in the forecast to insert these given quite a muted
forcing signal.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
High pressure north of the forecast area will keep an east/northeast
wind over the region Saturday. Upper level energy oriented sw-ne
will combine with some lower level convergence to produce a chance
of showers or thunderstorms through the weekend. The mean upper
trough becomes quite flattened Sunday and shifts east. However,
increased lower moisture and some potential differential heating
during the day has a typical diurnal increase in thunderstorm threat
lingering into Monday.
Southwest flow will keep mid 60s dewpoints in the region early next
week, and a weak cold front will pass by Tuesday night or Wednesday.
Initial indications for this fropa are that it will be battling a
dry airmass and be relatively rain-free.
Temperatures will generally top out between 80 and 85 with little
variability expected. Overnight lows will similarly be tied to
between 60 and 65, a little warmer Tuesday night and cooler
Wednesday night behind the dry fropa.
Any shower or thunderstorm activity that develops this holiday
weekend will likely be isolated to scattered in nature and sub-
severe as Dorian puts the brakes on any upper level flow over the
region, or at least removes the probability of a deeper trough from
affecting us.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
VFR conditions should generally continue through the period.
Cumulus clouds will dissipate this evening, and there may be a
slight decrease in the speed of the SW / SSW winds, though they
should remain in the 5-10 knot range overnight.
There is a very small chance of some showers making it into
KDAY/KCMH/KLCK late tonight, but it is more likely that there
will just be an increase in low and mid level clouds. It is also
not out of the question for a brief period of MVFR ceilings in
the 09Z-15Z time frame at these TAF sites (less likely further
south). At KLUK, some MVFR (to possibly IFR) fog is expected
early tomorrow morning.
Tomorrow, there does appear to be a chance of thunderstorm
development during the afternoon. This appears most likely at
KCVG/KLUK/KILN, where a VCSH has been included in the TAFs.
OUTLOOK...No significant weather expected.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...Binau
NEAR TERM...Binau/Hatzos
SHORT TERM...Binau
LONG TERM...Franks
AVIATION...Hatzos
Area Forecast Discussion
National Weather Service Northern Indiana
800 PM EDT Thu Aug 29 2019
.SYNOPSIS...
Issued at 757 PM EDT Thu Aug 29 2019
An upper level system tracking across the Great Lakes will drag
a cold front across the region tonight. This system will be
accompanied by a low chance of showers and thunderstorms this
evening into the early overnight hours. Low temperatures tonight
will range from the upper 50s to middle 60s. Mainly dry
conditions are then expected for Friday. Below normal temperatures
for late August will be in store for Friday, with highs only
reaching the mid and upper 70s.
&&
.UPDATE...
Issued at 757 PM EDT Thu Aug 29 2019
Low level moisture axis preceding sfc cool front has resulted in
shower and thunderstorm development across west central Lower
Michigan. Latest RAP analyses indicate some weak capping
persisting for surface based parcels, and this inhibition for
surface based parcels will continue to creep up early this
evening. Southeast sagging of low level moisture axis will allow
1000-2000 MLCAPE axis to drop into northern Indiana closer to the
03Z timeframe. Strongest upper forcing is just grazing the
southern Great Lakes this evening, but with narrow zone of
increasing elevated instability and lesser inhibition for elevated
parcels, suspect could still see some isolated-scattered
shower/storm development particularly along and north of Route 6
between 03Z and 06Z. Have noted a few reports from central Lower
Michigan this evening of very large hail/wind damage, but severe
threat should remain quite isolated, and even moreso as far south
as local area. Still cannot rule out a very low probability of a
strong storm across the far north late evening/early overnight,
but confidence continues to lower. Have made some adjustments to
PoPs to slow timing a bit to late evening/early overnight, but
otherwise no major changes to previous forecast.
&&
.SHORT TERM...(This Evening through Friday)
Issued at 216 PM EDT Thu Aug 29 2019
An upper trough is evident on water vapor imagery sweeping across
northern WI and the UP of MI. At the surface a cold front is
dropping southeastwards through this same region. Low level
theta-e advection is slowly moving into the far western counties
this afternoon with dew points just now reaching 60 at
Monticello. Mid to upper 60s dewpoints are being slowed by a
cluster of storms over SE IA/NE MO. While this will not prevent
additional theta-e advection, it could be delayed by a few hours.
This will have implications on the ability to destabilize prior
to the passage of the cold front. CAMs continue to struggle to
resolve the evolution of convection over the next 8 to 12 hours,
but they do seem to have a broad agreement on convection losing
its strength and areal coverage as it moves across the Lake. The
timing of the frontal passage has also slowed slightly which
should keep the CWA primarily precip free until after 00Z. There
will still be strong shear along and ahead of the front, but
available instability may be less than originally anticipated.
Can`t rule out a strong storm this evening, but the risk should be
fairly isolated. Front pushes south of the CWA around 06Z to
clear the area of rain chances.
Front stalls just south of the area for Friday to provide a pleasant
late summer day. Further west, a MCS is forecast develop along
the stalled front over northern MO before dropping southwards.
The residual MCV from this MCS could allow the front to sneak
slightly northwards into the area Friday night. The result may be
an isolated shower during the late night hours, but confidence is
low.
&&
.LONG TERM...(Friday Night through Thursday)
Issued at 216 PM EDT Thu Aug 29 2019
The stalled front returns slowly northwards Saturday through
Sunday night. During that timeframe a series of perturbations are
expected to progress east within broad height falls over the
area. This will result in off and on rain chances throughout the
weekend. Dry conditions are expected for the start of next week as
a ridge builds over the Plains. A brief window for rain exits
around mid-week as a fast moving closed low moves across the
northern Great Lakes.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 753 PM EDT Thu Aug 29 2019
Low level moisture axis across the western Great Lakes will sag
southeast in advance of a cool front. This moisture axis should
provide a narrow zone of elevated instability that could support
a potential of isolated/scattered showers/storms across extreme
northern Indiana/southern Lower Michigan in the 03Z-06Z timeframe.
Forcing is somewhat limited however, with stronger upper short
wave working across the northern Great Lakes. With low confidence
in any showers affecting terminals, will maintain VCSH mention at
KSBN through the early overnight. Gusty southwest winds to 25 to
30 knots to begin the period will rapidly diminish with boundary
layer decoupling into the 10 to 15 knot range after 01Z. VFR
conditions are expected to persist this period, with dry
conditions Friday and a potential of some sct-bkn mid level
cloudiness. Did maintain LLWS mention at KFWA this evening/early
overnight, but conditions should improve in this respect after
06Z.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...Beach Hazards Statement until 2 AM EDT Friday for MIZ077.
OH...NONE.
LM...Small Craft Advisory until 2 AM EDT Friday for LMZ043.
Small Craft Advisory until 11 PM EDT this evening for LMZ046.
&&
$$
UPDATE...Marsili
SYNOPSIS...Marsili
SHORT TERM...CM
LONG TERM...CM
AVIATION...Marsili
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Area Forecast Discussion
National Weather Service Key West FL
1124 PM EDT Thu Aug 29 2019
.SHORT TERM...
What kind of weather will the Florida Keys have during
preparations for Hurricane Dorian? The next few days will be
characterized by above normal chances of showers and thunderstorms
here at a time that is normally the peak of the wet season.
A broad inverted surface trough (separate and not directly related
to Dorian) has been slowly moving west across the Keys this
evening. This feature seems to have enhanced our shower and
thunderstorm activity today. Through Saturday, the trough will
continue to move west and reach the Central Gulf. In its wake,
southeast flow will develop, deepen, and strengthen a bit through
early Saturday. The air mass will continue to be richly moist,
with Precipitable Water values of 2" or more. The experimental 00z
Caribbean HRRR model shows abundant shower and thunderstorm
development late tonight and Friday morning near the Keys and
upwind to the southeast. Recent days have already featured a
plethora of shower and thunderstorm activity, and this will
continue to be the case through Saturday. In fact, coverage may
even pick up a little by Saturday as the moderate and somewhat
deep southeast winds across the area increase moisture flux and
transport.
A narrow ridge will pass across the Keys around Saturday night or
early Sunday. This ridge is simply a de facto dead zone between
the trough exiting to our west and the western edge of Dorian`s
circulation to our east. This could come with a period of drier
weather, but lack of confidence in timing leads to a broad-brushed
50 percent chance of rain throughout the preparation period for
Dorian. This is an above normal chance of rain for this time of
year.
&&
.MARINE...
A broad inverted trough axis is currently located near or just
west of Key West. It will continue to move west to the Central
Gulf by Saturday. This will bring a gradual turn of our winds out
of the southeast overnight, with speeds increasing on Friday and
Friday night. By early Saturday morning, mainly moderate and
possibly fresh southeast breezes will prevail.
Winds will then ease over the course of Saturday and Saturday
night, with a weak de facto ridge separating the trough and
Hurricane Dorian`s circulation passes across the Keys.
Then the future track, size, strength and timing of Hurricane
Dorian will drive the marine forecast from Sunday through early
next week. Relative to the Keys waters, the official NHC forecast
still moves Dorian north of the area during the first half of
next week. This means we should experience westerly winds as
Dorian makes its closest approach to the Keys. Of course, wind
speeds will depend on how close Dorian tracks to the Keys, but our
more northern and eastern waters have the highest probabilities
for experiencing higher winds, and sooner than our more southern
and western waters. Wind speed probabilities from NHC have
triggered Tropical Expressions of Uncertainty wording in the
Coastal Waters Forecast, i.e. wording such as Tropical Storm
Conditions Possible or Hurricane Conditions Possible, for various
marine zones at various times from Sunday through Monday night.
&&
.AVIATION...
Overnight and early Friday, although VFR cigs and VIS will
prevail at both the KEYW and KMTH island terminals, a trough will
allow for widely scattered to scattered showers and thunderstorms
to impact either/both terminals at times. Have included VCTS for
KEYW after 06Z to 12Z given the threat of new boundaries upstream,
with VCSH at MTH. Surface winds will be variable at 6 kts or
less, except may be gusty in and near showers, storms and
boundaries that impact the terminals. VFR conditions will prevail
at both the terminals.
&&
.TROPICAL...
At 11 pm, the center of Hurricane Dorian was located near
latitude 23.3N, longitude 68.4W, or approximately 760 miles east
to east-southeast of Ocean Reef. By the time Dorian reaches the
east coast of Florida during the first half of next week, it is
forecast to be a major hurricane. The 11 pm NHC advisory shifted
the forecast track about 30 miles south with its eventual
landfall point along the east-central or southeast coast of
Florida. More importantly for the Keys, the forecast cone now
encompasses the entire island chain, indicating it is within the
range of potential tracks. Of course, impacts extend well out and
away from the track. Given the range of possibilities and recent
forecast trends, all of the Florida Keys are on the hook in
needing to prepare and be ready for Hurricane Dorian. NHC
currently forecasts the earliest most reasonable arrival time of
tropical force winds to be Sunday morning and Sunday afternoon
over the Upper Keys and Lower Keys respectively, with the most
likely onset time about 18 hours later. The importance of the
earliest arrival time is this: it is the time by which you should
have preparations complete.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...Haner
Aviation/Nowcasts....Futterman
Data Collection......DR
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Area Forecast Discussion
National Weather Service North Platte NE
655 PM CDT Thu Aug 29 2019
.SHORT TERM...(This evening through Friday night)
Issued at 322 PM CDT Thu Aug 29 2019
An upper level disturbance across nrn Colorado moves through swrn
Nebraska this evening. The rapid refresh models are generally
keeping thunderstorm development across KS and scntl Nebraska while
the NAMnest and model blend develop storms farther north and west
along and south of Interstate 80. The southward trend in the RR
models is the result of a strong h700mb cap holding down high
instability and the progress of a sfc cold front dropping into swrn
Nebraska. MLCAPE is projected to be around 4000 J/KG early this
evening and winds aloft at 500mb are forecast to be around 30kts.
This would certainly be sufficient for severe thunderstorms and the
forecast this evening uses a blend of RR and other models for a
chance of storms mostly south of the Interstate.
Another rain chance develops Friday and Friday night as a result of
a disturbance across WA/OR dropping through Nebraska. The moisture,
at least aloft, is very good with h700mb-h300mb RH around 70
percent, but the lower levels are very dry. The forecast is for a
chance of showers and POPs are capped at 50 percent as a result of
the dry air at the lower levels. Thunderstorms are in place across
the Panhandle and south of Interstate 80.
The temperature forecast tonight, Friday and Friday night uses the
guidance blend plus bias correction. This forecast is warmer than
the straight guidance blend. Temperatures Friday could be on the
warm side of the forecast envelop if the rain does not
materialize.
.LONG TERM...(Saturday through Thursday)
Issued at 322 PM CDT Thu Aug 29 2019
The upper level ridge of high pressure which has governed temperatures
across the wrn U.S. this summer migrates north Monday and then
retreats back south Tuesday and beyond. A dry forecast is in place
after Saturday morning. The model blend produces highs in the
upper 80s across wrn and ncntl Nebraska Monday. H700mb
temperatures in the mid teens Celsius and h850mb temperatures
above 30C would support highs 5F to 10F warmer but the heating
cycle is weak in September.
A fairly strong cold front moves through Tuesday cooling highs back
down to the 70s to around 80. Rain chances develops Tuesday night
and Wednesday night but mostly isolated POPs are in place. The
moisture looks pretty good as a slug of subtropical moisture will
lift through the Rockies and the forcing is a strong disturbance
moving through the Dakotas.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 650 PM CDT Thu Aug 29 2019
Scattered TSTMS will end this evening with skies generally partly
cloudy overnight. Ceilings will remain above MVFR and VFR will be
the rule overnight. Ceilings will lower across portions of central
into southwest Nebraska Friday morning with MVFR conditions
expected. MVFR will then persist into the afternoon hours. VFR
should rule across northern Nebraska through the day. Winds will
be from the northeast tonight becoming east to southeast Friday.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Taylor
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Friday)
Issued at 321 PM CDT Thu Aug 29 2019
Water vapor satellite early this afternoon showed an upper level
trough moving southeast across eastern WY into northeast CO. A more
amplified upper level trough was shifting east across the upper
Midwest into the western Great Lakes States. At the surface a
cold front extended from central WI, southwest into south central
NE, then extended west-northwest into southwest NE. Southerly
surface and 850mb winds were advecting richer gulf moisture
northward across the CWA. Dewpoints were in the mid 70s this
afternoon across the CWA. There may be enough surface convergence
for thunderstorms to develop along the surface front in southern
NE along the KS border late this afternoon. Therefore, I added a
slight chance for thunderstorms across the far northern counties
late this afternoon. MLCAPE values at 19Z were in the 3,000 to
4000 J/KG range, and effective 0-6 KM shear was increasing to
around 30 KTS along the border. Therefore the environment will be
favorable for a few sever thunderstorms across southern NE, which
may skim across the norther counties along the NE border late this
afternoon.
Tonight, the southern stream H5 trough across southern WY/northeast
CO will dig southeast across eastern KS during the early morning
hours of Friday. Low-level CAA across the upper Midwest will allow
the surface front to push southward into the CWA this evening. The
combination of DCVA ahead of the approaching H5 trough and
surface convergence ahead of the front will allow widespread
thunderstorms to develop across northeast KS and extending west-
northwest along the front into north central KS/south central NE.
Several CAM models show a couple complexes of thunderstorms
developing across north central and northeast KS during the mid
evening hours along the front, which may develop into an forward
propagating QLCS that will track southeast across the CWA during
the late evening and early morning hours of Friday. The
environment will be favorable, given a increasing southwesterly
low-level jet, MLCAPE/MUCAPE of around 3000-40000 J/KG and 0-6 KM
shear increasing to 30 KTS as the southern stream H5 trough
approaches from the northwest. The primary hazards from a
developing QLCS will be damaging wind gusts and heavy rainfall.
The ERSL HRRR model actually shows more convective clusters,
similar to HP supercells developing along the front by 3Z and
moving southeast across the CWA. If we get rotating updrafts
embedded within the line then there could be isolated large hail.
I cannot totally rule out short lived meso vortices within the
QLCS, which could produce a few weak isolated tornadoes. Most
numerical models move the severe thunderstorms clusters/QLCS
southeast of the CWA after 9Z. We may see showers and a few
elevated thunderstorms continuing past 12Z to the northwest of the
OFB/front through the mid morning hours of Friday.
Even though the QLCS will be fast moving it could produce 1 to 2
inch rainfall rates per hours and in a few hours there may be 1 to 3
inches of rainfall. This may lead to flash flooding as the line move
southeast across the CWA. Therefore, I have issued a flash flood
watch from 3Z FRI through 18Z FRI. I kept the northern terr of
counties out of the watch since the thunderstorms may be more
scattered before evolving into a line/QLCS.
Friday afternoon, the front will stall out across southeast KS and
extend west into southwest KS. Expect mostly cloudy skies through
the afternoon. It will probably remain dry through the afternoon
hours. Highs will be cooler north of the front, with mid 70s to
around 80 across the CWA.
.LONG TERM...(Friday night through Thursday)
Issued at 321 PM CDT Thu Aug 29 2019
Friday night through Saturday, another perturbation embedded within
the northwest flow aloft will move southeast across the Plains.
The LLJ will transport richer moisture northward across the front
and elevated thunderstorms will develop Friday evening and through
the night. At this time the better chance for severe
thunderstorms will remain across southern KS and northern OK. The
heavier rainfall should shift southeast of the CWA during the mid
morning hours of Saturday, as surface high pressure builds
southwest across the CWA.
Saturday night through Sunday, another minor perturbation will move
southeast across the Plains and may cause a chance for showers and
thunderstorms Saturday night into early Sunday morning. A broad
upper level ridge across the southwestern US will build east into
the southern Plains Sunday afternoon.
Monday through Tuesday, high temperatures may increase towards 90
degrees as the upper ridge builds east across the southern Plains.
Expect dry conditions.
Wednesday through Thursday, an upper level trough will amplify
across the Great Lakes States and cause a weak front to push
southwest across the CWA. Since the upper ridge will be across KS,
I don`t think we`ll see much in the way of upper level support
for thunderstorms as the surface front pushes southwest across the
CWA early Wednesday morning. High will cool back into the upper
70s to mid 80s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 639 PM CDT Thu Aug 29 2019
VFR prevails with focus being on a line of TSRA expected to impact
terminals between 02Z and 04Z. There is still some uncertainty
with short term guidance on arrival times, but sided towards the
slower version from the RAP/HRRR with IFR flight categories
arriving in the 04Z-05Z time frame. There may also be IFR ceilings
at this time, but it will largely depend upon where the heavier
rain bands setup. Have ended precip by 14Z, but there is some
indication from the RAP that precip could linger a bit longer into
the afternoon so will need to address again at 06Z.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from 10 PM CDT this evening through Friday
afternoon for KSZ020>024-026-034>040-054>056-058-059.
&&
$$
SHORT TERM...Gargan
LONG TERM...Gargan
AVIATION...22