Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/24/19
Area Forecast Discussion
National Weather Service Amarillo TX
803 PM CDT Mon Sep 23 2019
Have updated graphical forecasts for the overnight period. Main
change is to lower pops across parts of the Texas Panhandle, now
keeping showers and thunderstorms confined to southeast Texas
Panhandle. Southeast zones remain in an area of enhanced
divergence aloft and downstream of a weak shortwave. Other
adjustment was to bring dewpoints better in line with existing
observations. Updated text products will be issued shortly.
.PREV DISCUSSION... /Issued 634 PM CDT Mon Sep 23 2019/
For the 00z TAFs...
Southeast and south surface winds expected to prevail through the
evening and most of the overnight hours with VFR conditions
expected through at least 09z Tuesday. Moist low-level flow
expected to lead to low cloud development before sunrise over
southeast Texas Panhandle. Some concern for MVFR ceilings to
move into terminals between 09z and 16z. For now will forecast
only a scattered layer during this time frame. Situation will be
monitored with any necessary adjustments to add ceilings being
made as needed.
Southwest surface winds expected most of the day on Tuesday as
deepening surface trof moves into the forecast area from the
northwest. Isolated to scattered thunderstorms Tuesday afternoon
expected to impact areas mainly to southeast of all terminals.
PREV DISCUSSION... /Issued 241 PM CDT Mon Sep 23 2019/
SHORT TERM...Today Through Tuesday Afternoon...
Main focus on the near term forecast is the low end potential for
thunderstorm activity as relatively weak southwest flow aloft
continues. Storm development may not happen today due to the lack
of mid/upper level forcing, modest mid level subsidence and very
dry air around 500mb noted on the 12z KAMA sounding. There is a
surface trough in the area with some moisture convergence west of
Amarillo to just west of Borger resulting in CU with moderate
vertical extent as of 1900z. It looks like the CU is struggling
with dry air entrainment, and this may keep convective initiation
at bay. However, there is a good dose of surface moisture given
dew points in the low to mid 60s on the eastern side of the
surface trough (low 50s west). This coupled with temperatures in
the mid 80s may allow enough instability to overcome dry air and
subsidence aloft. The latest RAP mesoanalysis suggest MLCAPE
approaching 1000 J/kg east of the trough, but still indicates
25-50 J/kg MLCIN as well. MUCAPE is much higher, but not realistic
given shallow moisture present. There is also some shear with
turning in the lowest 3 km and speed shear above 3km, resulting in
effective shear around 25 to 30 knots. Moreover, if a storm can
develop it could be strong with small hail and gusty winds.
Warm air advection will increase during the evening and overnight,
so storm development can`t be ruled out during this time. Mid
level moisture is also expected to return as the upper trough over
the western CONUS digs south and becomes a cutoff low over the
southern tip of CA by 12z Tuesday. The increase in moisture will
increase storm chances for some of the Panhandles Tuesday
afternoon. How quickly morning clouds clear out could impact areas
of higher CIN in the afternoon. If the near term and medium term
guidance is correct, PWATs will return to at least the 90th
percentile as MLCAPE approaches 2000 J/kg, especially in the
eastern half of the Panhandles where the best low level moisture
will reside. Deep layer shear will stay around 20 to 30 knots,
enough for support multicell or even some transient supercell
activity. Moreover, a strong to severe thunderstorm can`t be ruled
out. However, very heavy rain and localized flooding will be the
greatest concern given increased moisture and relatively slow
LONG TERM...Tuesday Night through Monday
As scattered convection leaves the area late Tuesday, the long
term forecast begins to moderate a bit, leaving generally dry
conditions on Wednesday and early Thursday. The 90s are not quite
done with us yet, as we should see much of the area in the low to
mid 90s Wednesday afternoon. Won`t exactly be much cooler on
Thursday or Friday either, as afternoon highs remain in the upper
80s. Morning lows for much of the upcoming week appear to be near
60 degrees, with the coolest temperatures remaining in the
Medium range models are in somewhat decent agreement in the upper
flow pattern, keeping much of the southern plains under a general
high pressure ridge pattern through the end of the week. While
this is occurring, the southwestern cut off low will wobble across
the desert southwest until the next system finally forces it out
of the way.
That kicker will be the next long wave trough, currently expected
to move into the pacific northwest by Friday. Ahead of the long
wave trough, it would appear that a decent amount of mid level
moisture will be surging into the south plains by next weekend.
Thunderstorm chances remain in the forecast for Saturday and
Sunday, yet have kept PoPs fairly low at least for now.
All in all, low temps are going to remain fairly comfortable, even
as the lows remain above normal for September. Afternoon highs
remain a bit warm as well. On Wednesday, we are calling for a high
of 91, which is only 3 degrees off of the record high for
Amarillo. The record for September 25th is 94, which was set in
1951 and previous years. Doubtful that this record will be
broken, yet it may be close.
Area Forecast Discussion
National Weather Service Caribou ME
934 PM EDT Mon Sep 23 2019
Low pressure will approach the area overnight and slowly cross
the state Tuesday. High pressure will build over the area later
Wednesday into Wednesday night. A cold front will cross the
area on Thursday followed by high pressure on Friday into the
.NEAR TERM /THROUGH TUESDAY/...
920 PM Update: Latest radar ref imagery shows cnvctv rnfl apchg
the wrn frontier of our FA as of mid to late eve, on track to
overtake much of the rest of the FA late tngt. The best banding
appears to be taking aim on the Cntrl ME Highlands and E Cntrl
areas, so no additional chgs to fcst QPF or hrly intensities
this update. Otherwise, fcst hrly temps/dwpts into the late ngt
hrs were updated using obsvd fcst hi temps and latest sfc obs
trends, with no chgs to fcst ovrngt low temps attm.
Orgnl Disc: ...Heavy rainfall expected overnight into early
First batch of steady rain/showers was pushing off to the east
as the cold front slides slowly to the s. The front looks like
it will stall just south of Houlton and Millinocket. The latest
suite of model guidance including the HRRR and RAP show a low
pres system moving up along the front tonight. Decent llvl
convergence sets up along the front. Difluence aloft w/a llvl
jet of around 40 kts and PWS of 1.70+ will be some ingredients
to allow to possibility of heavy rainfall. Model soundings
showed warm cloud processes w/elevated CAPE. The highest
CAPE(200-500 joules) looks like it will be across the Maine
Central Highland, Penobscot region into Mt. Katahdin. This will
also add to the heavy rain threat. Using a blend of the
mesoscale guidance, decided to raise rainfall totals by Tuesday
night to 1.2-1.5 inches w/some higher totals across the
Piscatquis and Mt. Katahdin region. This will allow for sharp
rises on the rivers, especially the smaller basins. Would not be
surprised to see rainfall of 1+ inches in 6 hrs. Banding is a
threat on the north and northeast side of the low. Therefore,
rainfall could be underdone. Evening crew can assess this
further this evening.
Much cooler overnight especially across the n and nw as cooler
air filters into the area. Some sites across the nw could see
upper 40s by 7 AM Tuesday. Cooler and wet for Tuesday. Rain will
transition to showers as the low slowly moves into New
Brunswick. The upper low is shown by the model guidance such as
the NAM and GFS to migrate across the region Tuesday afternoon
w/a round of showers regenerating across the Downeast region.
Decided to follow this trend showing a band of steady shower
activity across the aforementioned region.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
The upper low finally pushes east into the Canadian Maritime
provinces later Tuesday night into early Wednesday. The threat
for showers continues Tuesday evening, with best chances across
the north where likely pops were maintained, otherwise
continued mostly cloudy skies downeast areas with scattered
showers expected. Lows Tuesday night expected to remain in the
upper 40s north to lower 50s central and downeast areas.
Mostly cloudy skies and a slight chance for showers continues
Wednesday morning for northern areas, otherwise decreasing
clouds can be expected on Wednesday as 500 MB heights rise with
weak ridging both at the surface and aloft expected. High
temperatures Wednesday afternoon are expected to range from the
upper 50s north and low to mid 60s central and downeast.
Clouds begin to increase again Wednesday night in advance of the
next cold front approaching from the west. The front is expected
to cross the region Thursday with a chance for showers.
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Decreasing clouds are expected Thursday night along with cooler
temperatures. Fair and dry weather is expected on Friday along
with seasonable temperatures as high pressure builds across to
our south. Another cold front approaches the region Friday night
and crosses the region on Saturday with the chance for showers.
Much cooler and drier weather will build back in for Sunday and
early next week.
.AVIATION /22Z MONDAY THROUGH SATURDAY/...
NEAR TERM: MVFR/VFR this afternoon will deteriorate to MVFR and
IFR as rain moves back into the terminals w/some fog. There is
potential for LIFR especially in the heavy rainfall overnight
into Tuesday morning. Light winds overnight.
IFR for the northern terminals on Tuesday w/conditions improving
to MVFR for KBGR and KBHB. Winds will continue to light from the
NNW 5 to 10 kt.
SHORT TERM: Outlook Tuesday night through Saturday
Tue Night...MVFR possible in lingering -SHRA. North wind around
Wed-Wed Night...VFR. North wind 5 to 10 kt.
Thu-Thu Night...VFR then MVFR possible Thu afternoon/evening in
Fri Night - Sat...MVFR possible in -SHRA.
NEAR TERM: Decided to hang on to the SCA for another cycle as
winds were 15-20 kts and seas at 5 ft even though winds were
dropping off. The llvl jet moving ne tonight kick winds up some
later this evening w/gusts getting into the lower 20s. The
evening crew can assess things more and if conditions
condition to improve, then the SCA can be dropped. Winds turning
to the NNW on Tuesday will be below 20 kts.
Seas attm were averaging around 5 ft. The latest run of the local
wave model matched it previous run of showing seas holding around
5 ft tonight, and then subsiding to 4 ft on Tuesday.
SHORT TERM: Wind/seas should remain below SCA levels for the
most part through the period, although a few gusts to 25 kts
are possible in the SW flow ahead of an approaching cold front on
Thursday, with 4 to 6 foot seas possible.
MARINE...Small Craft Advisory until 5 AM EDT Tuesday for ANZ050-051.
Area Forecast Discussion
National Weather Service Fort Worth TX
917 PM CDT Mon Sep 23 2019
Have updated to lower PoPs this evening, but later tonight I do
expect the convection to our west to make slow progress east and
northeast into the northwestern part of the CWA. So PoPs will
increase again after midnight in this area. By sunrise expect
scattered convection across the northwest and northern zones
along an old decaying 500 mb shear axis that has been draped
across this area for a couple days now. Convection will be
elevated and thus no severe weather potential, but still some
brief heavy rainfall, lightning and wind gusts to 40 mph will be
.AVIATION... /Issued 653 PM CDT Mon Sep 23 2019/
Scattered convection developed across North Texas this afternoon,
and is on a downward trend as of 2330z. While most airports have
not experienced storms immediately at the terminals, convection
with occasional lightning strikes still remains within VCTS
range, thus will maintain this mention through 01z. In addition,
an outflow boundary is moving into the DFW area from the north,
which will result in a temporary wind shift over the next hour or
two, necessitating flow configuration changes at some airports.
Winds should come back to the east/southeast fairly quickly this
evening. Afterwards, VFR rain-free conditions will prevail
overnight. At Waco, there is a low potential for a stratus
intrusion just after daybreak Tuesday, and will maintain a Tempo
mention of some cigs below 2 kft.
Additional scattered thunderstorms are possible Tuesday
afternoon, and coverage/timing should be rather similar to today`s
activity. Will introduce VCTS at all Metroplex airports for a few
hours tomorrow afternoon. Otherwise, south/southeast winds at 10
kts and VFR conditions will prevail through Tuesday.
.LONG TERM... /Issued 235 PM CDT Mon Sep 23 2019/
/Tuesday Night onward/
Hot with daily chances for isolated to widely scattered showers
and thunderstorms will be the name of the game through the
extended portion of the forecast. It looks to be at least another
10 days or so before we could see our first fall cold front.
Upper-level ridging looks to remain in place through the next 7+
days, but with the center of the ridge displaced to our east, and
with deep southerly flow, we will see some rain chances. The
highest chances for showers and thunderstorms will likely come
Friday and through the weekend. An upper-level trough over the
West Coast will cut off from the jet stream during the next couple
of days. The resultant upper-level low will remain over the Gulf
of California for a couple days, but will eject east-northeast
across the Southwest and across Oklahoma into the weekend.
Differential cyclonic vorticity advection associated with this
upper-level low will act to enhance lift and therefore rain
chances over the weekend. Given the lack of any well-defined
surface boundaries and weak wind shear, thunderstorms will remain
disorganized. A few lucky individuals may see some rain with these
thunderstorms, but for many of us, we will stare longly at
distant thunderstorm updrafts wondering why we have missed out on
the rain once again.
Heading into next week, the upper-level ridge over the Southeast
will reestablish itself. Deep southerly flow will continue to
provide enough moisture and heating that we will maintain daily
chances for isolated to widely scattered showers and
thunderstorms. The highest shower/thunderstorm chances next week
will be in Central Texas where the deepest moisture, and perhaps
some seabreeze enhancement, will exist.
The deterministic runs of the GFS and ECMWF, as well as some of
the European ensemble members seem to hint at a cold front towards
the end of the first week of October (around October 3-5). There
has not been much run to run consistency however, and the folks at
CPC don`t really seem to be buying into it yet in their extended
range outlooks. As anyone who follows North Texas weather knows,
there have been quite a few "false alarm" model cold fronts
through September, and this could be another. Having said that, it
is noteworthy that the ECMWF and GFS are both fairly aggressive.
I`m not getting my hopes up yet, but we shall see...
.SHORT TERM... /Issued 118 PM CDT Mon Sep 23 2019/
/Now through Tuesday/
Early afternoon surface analysis features weak southerly flow with
temperatures ranging from the upper 80s and lower 90s across much
of the region to the lower 80s along the Red River. There is some
weak surface convergence noted to the northwest of the Metroplex
and to the northeast, but flow is generally weak. We remain under
the influence of a fairly stout subtropical ridge with weak flow
through 300 mb, but the stronger subsidence associated with the
ridge remains to our east and southeast. With ample low level
moisture in place, there will continue to be chances for showers
and thunderstorms through Tuesday.
Water vapor and visible satellite imagery shows a band of mid
level moisture and clouds streaming in across West Texas. This is
associated with an upper trough which is digging across the
southwest U.S. this afternoon. There appears to be some ascent
spreading across West Texas with this feature given an increase in
vertical cloud growth and some convection firing across that part
of the state. While any appreciable forcing should stay off to
our northwest through this evening, we`ll still have a chance for
showers and thunderstorms across parts of the region over the next
24 hours. Latest HRRR soundings indicate that subtle capping is
almost gone as far south as the Metroplex. With weak low level
convergence ongoing north of I-20 to the Red River and continued
heating, we should see an uptick in scattered thunderstorm
coverage through the evening hours, mainly north and northwest of
the Metroplex. This is reflected in the visible satellite imagery
which shows a more robust cumulus field across the northwest half
of the CWA. For the remainder of the afternoon and evening, we`ll
have 30-50% PoPs generally along and north of the I-20 corridor.
Coverage of thunderstorms may be a little farther south than the
last few days and may impact parts of the Metroplex. The strongest
storms today could produce some gusty winds, but locally heavy
rainfall and frequent lightning will be the main threats. Any
showers and storms should diminish in coverage later this evening
with loss of heating, although a moist airmass will remain in
place so any localized areas of convergence could result in
additional showers and storms.
On Tuesday, the upper trough to the west should be over southern
Arizona. While this main feature will be too far west to have
significant impacts on our weather, it will help keep stronger
ridging off to our east. A weak 500-300 mb upper trough will drift
north along the Texas coast and may provide at least some weak
ascent through the afternoon across North Texas. We`ll still keep
our focused area of surface convergence near the Red River where
PWs will remain near or slightly above 2". PoPs again will be
highest north of I-20 toward the Red River.
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 75 91 76 94 75 / 30 30 20 10 0
Waco 73 94 73 95 73 / 10 10 0 5 0
Paris 71 87 71 87 70 / 40 50 20 20 5
Denton 73 90 74 93 73 / 30 40 20 20 0
McKinney 73 90 74 93 73 / 30 40 20 20 0
Dallas 75 92 76 94 76 / 30 30 20 10 0
Terrell 73 92 74 94 73 / 20 20 10 5 0
Corsicana 73 92 72 93 72 / 10 10 0 5 0
Temple 73 94 72 93 71 / 10 10 0 5 0
Mineral Wells 71 91 72 93 71 / 40 40 20 5 0
Area Forecast Discussion
National Weather Service Green Bay WI
1042 PM CDT Mon Sep 23 2019
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Tuesday
Issued at 241 PM CDT Mon Sep 23 2019
The latest RAP analysis and satellite/radar imagery show cyclonic
flow across the central Great Lakes early this afternoon.
Instability showers popped up early this afternoon across far
northeast WI from Iron Mountain to Kewaunee after the system
showers ended by mid-morning. These should dissipate late this
afternoon. Elsewhere, cool air beneath the upper tough has
contributed to a cu field over much of north- central and
northeast WI. Looking to the west, warm advection is occurring
aloft over the northern Plains but clouds are sparse due to very
dry air. Since the next front is not expected to impact the area
until Tuesday night, forecast concerns generally revolve around
fog potential tonight and temps.
Tonight...High pressure will move east across the Ohio Valley
while a surface ridge axis slides east across Wisconsin. The
pressure gradient will remain relatively tight as a result and
will limit fog development despite all of the rainfall lately, and
the fact that low temps are projected to fall below the cross-over
temp. Still though, would not be surprised to see patchy fog
develop over the northwoods. With skies clearing across northeast
WI early this evening, low temps to range from the middle 40s over
the northwoods to the low 50s over the Fox Valley and Lakeshore.
Tuesday...Warmer air will invade the region from the west ahead of
a cold front, which will push into the northern Mississippi Valley
by late in the afternoon. Progged soundings indicate some shallow
fair weather cu could pop by late morning as this warmer/more
moist air arrives from the west. But strong capping will prevent
any chance of a shower or storm during the day. It will be warmer
with a breezy southwest wind, with highs ranging from the middle
to upper 70s at most locations away from Lake Michigan.
.LONG TERM...Tuesday Night Through Monday
Issued at 241 PM CDT Mon Sep 23 2019
A cold front will bring showers and thunderstorms to the area on
Tuesday night. The main question is if strong to severe storms
that form out to our west will hold together as they track east.
Instability early in the evening will be 1000 to 1500 J/kg with
around 40 knots of bulk shear, however we lose instability quite
quickly as the sun sets just before 00z. Therefore despite the
decent dynamics and severe weather parameters, confidence is not
high that the storms will hold together as they move through the
cwa given the late arrival of the front across our area.
Some showers may linger on Wednesday with wrap around moisture and
instability showers behind the front. However high pressure will
then bring in a drier cooler airmass Wednesday night and Thursday
with below normal temperatures during this time frame.
The dry period will be short lived as yet another low pressure
system brings a swath of showers and maybe a few thunderstorms by
the end of the work week. Next weekend starts out dry, however
another low pressure system will bring a return of unsettled
weather late next weekend and into the early part of next week.
.AVIATION...for 06Z TAF Issuance
Issued at 1042 PM CDT Mon Sep 23 2019
VFR conditions will continue through Tuesday afternoon,
with the exception of patchy ground fog late tonight and early Tuesday
A cold front will bring showers and thunderstorms Tuesday night
along with MVFR and brief IFR conditions.
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1040 PM EDT Mon Sep 23 2019
Issued at 1040 PM EDT MON SEP 23 2019
Updated PoPs based on the HRRR showing isolated showers for the
next couple of hours. A few stray showers have popped up on radar
over the last couple of hours as the cold front continues to
progress over eastern Kentucky. Current temperatures are generally
in the mid to upper 60s. Some areas further west are around 70
degrees. Forecast lows are in the lower 50s in the north and upper
50s in the southeast. This still seems reasonable, so no changes
were made. Merely ingested the latest observations and blended
them into the overnight hours. Some fog has also begun to develop
in the south in the Cumberland Basin as seen from the GOES-16
Night Fog satellite imagery. This will continue to be monitored
for the possibility of dense fog in the river valleys. An updated
ZFP was sent to reflect evening wording. Updates have also been
sent to the web and to NDFD.
UPDATE Issued at 642 PM EDT MON SEP 23 2019
The forecast remains largely on track this evening. Much of the
scattered shower activity has either diminished or moved to the
southeast of the state. However, there are some isolated showers
in central Kentucky and in West Virginia along the cold front. The
HRRR suggests at least some isolated showers through this evening
into early tonight. Will continue to monitor the activity along
the edge of the front to see if any adjustments are needed to PoPs
late this evening. At this time, only made minor adjustments.
Current temperatures are generally in the lower 70s in southeast
Kentucky and in the upper 70s in central and in northern Kentucky.
Expecting lows in the lower to upper 50s. No other changes were
needed beyond ingesting the latest observations and blending them
into the evening hours. A new ZFP was sent. Updates have also been
sent to NDFD and to the web.
.SHORT TERM...(This evening through Tuesday night)
Issued at 420 PM EDT MON SEP 23 2019
As of late afternoon, an upper level low was moving across Ontario
and near southwestern Quebec. A shortwave trough extended south
through the Great Lakes and into the lower OH Valley. Shortwave
ridging extended through the Plains and into western Ontario with
a shortwave trough moving across western Canada south into the
Rockies. A surface cold front extended south from a surface wave
of low pressure tracking through the St Lawrence Valley region.
This front appears to have moved east of KFGX to KLEX to KBWG
line. Coverage of convection along and immediately ahead of the
boundary is greater north and northeast of the area with some
isolated to scattered activity further south over central KY.
Other showers were moving through the areas near the VA border.
Further upstream of the area, sfc high pressure was centered in
the mid MS Valley region and entering the lower OH Valley.
Tonight and into Tuesday, the upper level low will track east
southeast and reach the Northeast/New England with the shortwave
trough extending to the south moving east of the area by late this
evening. The surface cold front, meanwhile, will move into VA
around or shortly after sunset. Some isolated to scattered
convection should accompany the boundary with additional lighter
showers in advance of the front. Some locations could still
receive measurable precipitation, but rainfall from this will be
very light and many cases not measurable. Sfc high pressure will
build east across the OH Valley behind the boundary with the
center of the sfc high reaching northeast KY by sunset on Tuesday.
The shortwave ridge axis will also move east and be west of the
area by Tuesday evening.
The axis of the ridge will move east of the area by the end of the
period while the sfc high settles into the central Appalachians on
Tuesday night. Meanwhile, the next trough will have dug into the
northern Plains and then the upper MS Valley by the end of the
period. An associated cold front will also have begun to
approach. This system will affect the area to start the long germ
Chances for showers will diminish from northwest to southeast with
the frontal passage through this evening. Only isolated to
scattered coverage of measureable precipitation is expected. A
drier airmass will move in with the sfc and upper ridging, with
dry weather to end the period. In fact, rh should drop into the 25
to 35 percent range in most locations on Tuesday afternoon.
As for temperatures, drier and somewhat colder air will arrive in
the western locations first which also will clear first as well.
Some low clouds are anticipated across the southeast portions of
the area and deeper valley fog is also anticipated later in the
night as the pressure gradient decreases. Thus the coldest min
temperatures will be in the northwest and west with readings
around 50 or even a 49 or two in the typically coldest spots there
such as the COOP site located north of Mt. Sterling. Mainly just
cirrus are expected on Tuesday with the airmass appearing too dry
for much in the way of cumulus development. The airmass should
warm up and with the ongoing dryness despite recent light
rainfall, the dry soils should contribute to temperatures on the
warmer end of guidance. Thus leaned toward the warmer NBM highs
With the sfc high moving east and the low level flow becoming
southeast to south on Tuesday night, deeper valleys should be much
considerably colder than the coalfield ridges with a moderate
ridge/valley split anticipated. Normally colder locations should
reach the upper 40s to around 50 degree mark while ridges bottom
out in the mid 50s.
.LONG TERM...(Wednesday through Monday)
Issued at 343 PM EDT MON SEP 23 2019
The extended portion of the forecast begins on Wednesday with a
developing longwave trough aloft as it crosses the Great Lakes. Surface
high pressure remains in place over the lee side of the
Appalachians. With the previous airmass passing through, Wednesday
will feature drier conditions. Surface winds will feature a more
southerly wind being some weak downslope. However, very dry mid
layers in place may lead to mixing into Wednesday afternoon
resulting in afternoon RH values in the low 20s. The mentioned
trough will push a boundary through the OH Valley by Thursday.
This will be a strong shortwave tracking through the base of the
trough by 12Z Thursday and into the OH Valley. Near the surface
for Thursday, model soundings do show some instability concerning
this front but moisture associated with this front will be in
question. WPC values barely give 0.10 inches of precip and PWAT
values are lower then the previous front passing through. Will
keep the slight chance pops from the NBM for Thursday but will
keep thunder in the grids. The thunder possibility is in question
because there is less moisture with this boundary on Thursday then
the previous one. This will need monitored in the coming days.
The rest of the forecast will feature a dry and above normal
temps. Despite the airmass moving through after the frontal
passage, Thursdays highs will still be above normal and Friday
through Sundays highs will be over 10 degrees above normal. The
upper level pattern will feature ridging reestablishing itself by
Friday and then into the weekend as surface high pressure remains
in place over the central Appalachian range. For now, the trend is
for continued dry and above normal temperatures.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 808 PM EDT MON SEP 23 2019
MVFR conditions were reported at most TAF sites at issuance. The
exception to this is at SYM where most clouds and shower activity
have progressed to the southeast with the passage of a cold front.
Cloud cover and isolated showers will persist late this evening
into early tonight as the front moves further southeast. Although,
expecting shower chances to decrease into tonight, as seen by
recent Hi-Res model guidance. The main concern for the overnight
will be river valley fog development as well as possible stratus
build down. At this time, have included at least MVFR VIS for the
TAF sites, but more widespread fog is expected through dawn,
particularly in the east. However, the fog will then dissipate
around 13Z tomorrow morning and VFR conditions will return. With
surface high pressure building in over the region, dry weather
will be the main story tomorrow. Winds will be light and variable
through the period as well.
Area Forecast Discussion
National Weather Service Seattle WA
854 PM PDT Mon Sep 23 2019
.UPDATE...No significant changes to the forecast this evening.
Latest RAP analysis this evening shows western Washington embedded
within a belt of strong NW flow in the mid and upper levels of
atmosphere, characterized by a 120kt+ jet streak to the north
across BC. A weak sfc frontal system was noted just offshore the
Washington as well, likely associated with a shortwave trough
across SE Alaska. Not a lot of forcing was found in the vicinity
of this frontal boundary-tho local radar imagery and MRMS radar
imagery show areas of light rain pushing across portions of
western Washington. This is likely the result of a layer of warm
air advection in the 925-850mb levels. Expect this activity to
follow in the general vicinity of this frontal system as it pushes
across western Washington. The front will likely weaken given its
displacement from the parent system and overall weak dynamics. So
expect showers to gradually fade as they push east overnight.
All of this should open western Washington up to a drier Tuesday
although the upper level pattern will hardly budge. Although a few
showers will not be impossible, not seeing much moisture in the
850-500mb layer so should just mainly result in residual cloud
cover. Previous discussion follows with a marine and aviation
.PREV DISCUSSION... /issued 414 PM PDT Mon Sep 23 2019/
.SYNOPSIS...A weakening system will move through Western
Washington this evening. An upper level ridge will build offshore
Tuesday into Wednesday. Next system arriving on Thursday. A cool
upper level trough will move through Friday into Saturday with a
drying trend beginning Sunday as northerly flow aloft develops
over the region.
.SHORT TERM /TONIGHT THROUGH THURSDAY/...Satellite imagery shows
cloudy skies over Western Washington this afternoon. Doppler radar
shows rain starting to decrease over the central portion of the
area. Temperatures at 3 pm/22z were in the mid 50s to lower 60s.
Warm front like feature will continue to drop south this evening
with the steady rain coming to an end in the early evening hours.
Showers behind the front continuing through the night. Lower
layers of the air mass remaining quite moist keeping skies cloudy
overnight. Lows will be in the 50s.
Northwesterly flow aloft continuing Tuesday with the upper level
ridge offshore beginning to rebuild. Shower activity becoming
confined to the Cascades by midday. Weak low level onshore flow
continuing with light flow in the lower levels as well keeping
skies mostly cloudy throughout the day. Highs on Tuesday remaining
below normal, in the lower to mid 60s.
Upper level ridge building into Western Washington Tuesday night
into Wednesday. By 00z Thursday 500 mb heights in the lower 580
dms. Residual low level moisture still over the area Wednesday
morning. Low level flow light and remains light throughout the
day. Tough call on when the low clouds will dissipate Wednesday.
With the warm temperatures aloft there is the potential for an
above normal day temperatures wise ( normal in Seattle Wednesday
68 ) but for now will be a little conservative and keep some low
clouds in the morning hours and highs in the 60s. Lows Tuesday
night in the mid 40s to mid 50s.
Ridge breaks down Wednesday night with the next system arriving
out of the northwest Thursday. This is a little slower than
previous forecasts. Front weakening as it moves into the ridge
plus northwesterly flow aloft will help rain shadow the central
Puget Sound. Will word the forecast chance of rain. Highs back
down into the lower to mid 60s.
.LONG TERM /FRIDAY THROUGH MONDAY/...Extended models are having
trouble with the timing of the upper level low that moves down
from the north behind the front. The ECMWF has the low center
already to the Canadian border by 00z Saturday. The GFS is 12
hours slower with the low with the low center further east.
Ensembles are not much help. Will keep a chance of showers in the
forecast for Friday and Saturday. The air mass will cool with the
snow level dropping down to around 4500 feet later Friday into
Saturday. Not much moisture left by this point but it is possible
there will be a light dusting of snow on the higher passes ( the
road will be too warm for the snow to stick to the pavement ).
Better agreement in the models on Sunday with the low hanging
around but the center of the low is east of the area. Return flow
around the low keeping a chance of showers in the Cascades and and
Southwest Interior. For the remainder of the area dry and cool
with highs only near 60. Low moving south on Monday with dry
northeasterly flow aloft over the area. The cool air mass combined
with clearing skies will result in the coldest lows of the season
Monday morning with the colder locations getting down into the
mid 30s. Even in the Seattle area lows will be in the mid 40s. The
coldest morning since May 1st. Felton
.AVIATION...A weak frontal system will push across the area
overnight and gradually fade. This will bring scattered light
shower activity to some of the terminal through the early morning
hours of Tuesday before dissipating. Ceiling forecast will be
another struggle overnight as low cloud cover is guaranteed.
Mainly low end MVFR is expected but IFR will not be out of the
question. Will try and fine tune this with the 06z update based on
best available model guidance. Luckily should see improvement back
to VFR cigs Tuesday afternoon. Winds generally south 5-12kts with
westerly wind expected at CLM and HQM (later in the day).
KSEA...MVFR for much of the overnight period, though periods of
IFR will be possible. Conditions should improve to VFR by the
afternoon. Winds generally S/SW at 8-12kts.
.MARINE...A weak frontal system, located just offshore this
evening, was pushing some scattered light showers across some of
the marine waters. This will continue into the overnight hours but
gradually fade through the early morning. Left the SCA winds for
the coastal waters, Puget Sound, and Northern Inland waters as is
thru 12z Tuesday. SCA winds may materialize on occasion across the
far western portion of the western Strait, and this will be
monitored over the coming hours.
Gradients across the Strait of Juan de Fuca noticeably increase
after 12z Tuesday. Gradients look strong enough to warrant SCA
winds for the central and eastern portions, so have gone ahead and
issued this valid thru 12z Wednesday. Winds across these portions
of the Strait will likely bleed into the adjacent waters of
Admiralty Inlet and the Northern Inland Waters tomorrow afternoon.
Additional marine headlines will likely be needed Wednesday as
another weather system approaches western Washington.
.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed
PZ...Small Craft Advisory until 5 AM PDT Tuesday for Coastal Waters
From Cape Flattery To James Island 10 To 60 Nm-Coastal
Waters From Cape Flattery To James Island Out 10 Nm-Coastal
Waters From James Island To Point Grenville 10 To 60 Nm-
Coastal Waters From James Island To Point Grenville Out 10
Nm-Coastal Waters From Point Grenville To Cape Shoalwater
10 To 60 Nm-Coastal Waters From Point Grenville To Cape
Shoalwater Out 10 Nm-Northern Inland Waters Including The
San Juan Islands-Puget Sound and Hood Canal.
Small Craft Advisory for rough bar until 5 PM PDT Tuesday for
Grays Harbor Bar.
Small Craft Advisory from 8 AM Tuesday to 5 AM PDT Wednesday for
Central U.S. Waters Strait Of Juan De Fuca-East Entrance
U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory from 5 PM Tuesday to 8 AM PDT Wednesday for
Northern Inland Waters Including The San Juan Islands.
Small Craft Advisory from 5 PM Tuesday to 5 AM PDT Wednesday for
Area Forecast Discussion
National Weather Service Shreveport LA
1033 PM CDT Mon Sep 23 2019
Mostly vfr skc across area, aside from remnant leftover clouds
along boundary stretching east to west across nrn fringe of cwa.
Overnight convective redevelopment possible along and just south
of boundary, towards early morning hours with next short wave. If
so, may see aftn stabilization following period of convection at
ktxk, keld, and possibly kmlu durg peak htg, and would likely
continue thru remainder of 25/06z fcst cycle. Meanwhile, isold
convection possible at ktyr, kggg, and kshv in aftn, but not
worthy of mention in terminal fcst. Once again, aftn sea breeze
expected to develop from the south, and may again effect the
klfk area, although tstms have been limited in sea breezes lately.
Lgt winds at kmlu, keld, and klfk may allow for some fog
development later tonight. Low clouds will return early to ne TX
btwn 24/08-10z, but may delay further east and only affect kshv
and ktxk briefly after 14/12z. SW winds expected most of area Tue
aftn with scattered cumulus across remaining portions of area not
affected by convection, becmg mostly vfr skc, with clouds possibly
remaining in the ktxk and keld areas near the frontal boundary./07/.
.PREV DISCUSSION... /issued 935 PM CDT Mon Sep 23 2019/
Have only made minor adjustments for overnight pops after taking
close look at HRRR model trends. Expecting most redevelopment to
occur closer to daybreak, but simply increased pops after midnight
with current radar quiet. Overnight lows in lower 70s still on
track as current 9 pm readings have mostly fallen to 80 degrees or
PREV DISCUSSION... /issued 428 PM CDT Mon Sep 23 2019/
SHORT TERM.../Tonight through Tuesday Night/
The convection across the far Nrn zones have diminished as of
mid-afternoon, but not before dumping widespread 3-7+ inches of
rain across Nrn and Cntrl McCurtain County OK, and 2-4" of rain
across Sevier and Nrn Howard Counties in SW AR. The residual
H850-700 theta-e axis lingers across this area, although a weak
convectively induced outflow bndry has drifted S to near a SLR, to
OSA, to TXK, to S of a Prescott AR line, which has focused
isolated to widely sct convection this afternoon. Meanwhile,
widely sct convection associated with a weak seabreeze has begun
to push into portions of Deep E TX, although much of this
convection remains diurnally driven and should diminish
by/shortly after sunset. Have inserted slight chance pops mention
this evening across much of E TX/far Srn AR, and kept low to mid
chance pops going across the far Nrn zones closer to the mid level
theta-e axis. However, the short term progs are in general
agreement with a mid level impulse traversing ENE along the Red
River of Srn OK late tonight, re-igniting sct convection across
the waterlogged areas of SE OK/adjacent sections of SW AR. Have
beefed up pops to likely/high chance for these areas late tonight,
tapering to low chance closer to the I-30 corridor. Did consider
a small Flash Flood Watch area for this area, but given the very
small area, will allow this area to be covered with advisories or
warnings if needed. Fortunately, even the hi-res models suggest
that additional QPF totals will be considerably lower than what
was observed this morning, but still can`t rule out additional
amounts of up to 1-2 inches.
The short term progs remain in general agreement with the weak sfc
bndry over Srn AR/extreme NE TX/SE OK will remain stationary
Tuesday, which could focus additional sct convection throughout
the day as the weak shortwave impulse traverses the Nrn portions
of the region. Have increased pops to mid/high chance Tuesday over
this area, with more isolated convection expected especially by
afternoon over portions of E TX/extreme Nrn LA. Did trend max
temps just above the Blended guidance/MOS given that the morning
low clouds should again scatter out, allowing for strong
insolation. While the sfc bndry should gradually wash out Tuesday
night, the progs are in generally agreement with another weak mid
level impulse traversing Srn and Ern OK near the mid level theat-e
axis, which may allow for additional sct convection development
late. Thus, have bumped pops up to low chance for SE OK/adjacent
sections of SW AR, which looks to persist into Wednesday.
LONG TERM.../Wednesday through Monday/
On Wednesday, an upper ridge will be over the Northeast Gulf of
Mexico and a broad upper trough will be moving across Southern
Canada resulting in a nearly zonal flow aloft over the region.
Isolated to scattered showers and thunderstorms may still be ongoing
across Southeast Oklahoma and adjacent portions of Southwest
Arkansas as a weak shortwave trough embedded in the zonal flow moves
across Arkansas. Rain chances will be much higher farther north into
Oklahoma and Arkansas as a cold front slowly moves south. It is
possible that a remnant outflow boundary could move into portions of
our area north of Interstate 30, which could help to focus the
convective development. However, the departure of the shortwave
trough should lead to decreasing rain chances as what little in the
way of upper forcing diminishes.
The GFS remains the far more aggressive model regarding the
southward extent of this next cold front and the resulting QPF.
Almost all of the other models keep the front well north along with
the vast majority of the precip. PoPs were maintained for Thursday
across Southeast Oklahoma and Southwest Arkansas, but I sided with
the majority of the model guidance and only mentioned slight chance
By Friday and into Saturday, a cutoff trough over the Desert
Southwest will quickly eject into the Plains. This will help push
yet another cold front southward that will stall before reaching our
area. However, increasing deep southerly flow and a surge of
moisture northward into the area should result in scattered showers
and thunderstorms Friday and Saturday, especially across East Texas.
By the end of the weekend and into early next week, a very strong
upper ridge will build over the Southeast CONUS. As the ridge
retrogrades over the area, rain chances will decrease, and the heat
will begin to build. Despite rain chances throughout much of the
long-term period, widespread wetting rains are not expected. Thus,
there will be very little to hold temperatures down. Daytime high
temperatures in the low 90s are expected through the end of the
week, but should begin to climb into the mid to possibly upper 90s
by Monday with the returning ridge.
.PRELIMINARY POINT TEMPS/POPS...
SHV 74 92 72 93 / 10 20 10 10
MLU 72 92 70 94 / 10 30 10 10
DEQ 71 83 71 90 / 40 60 30 30
TXK 73 87 72 90 / 20 40 20 10
ELD 71 88 70 91 / 20 30 20 10
TYR 75 91 74 93 / 10 20 10 10
GGG 74 92 73 92 / 10 20 10 10
LFK 72 92 70 93 / 10 20 10 10