Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/26/19
Area Forecast Discussion
National Weather Service Boston/Norton MA
1032 PM EDT Fri Oct 25 2019
A weak low pressure traveling along a front crosses through our
area late tonight, bringing a few showers mainly to areas north
of the MA Turnpike. High pressure brings dry and seasonable
weather Saturday.Low pressure will bring a widespread soaking
rain to the region on Sunday. Scattered showers and an abundance
of clouds will linger Monday, Tuesday and possibly into
Wednesday but a washout is not expected. Onshore flow and high
astronomical tides will likely result in pockets of minor
coastal flooding along the eastern Massachusetts coast early
next week. A cold front may bring a steadier/heavier period of
rain sometime later Thursday and/or Friday.
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Made some tweaks to the forecast this evening. Last several runs
of the HRRR have been matching up with the observations rather
well. These runs have been suggesting measurable rainfall
remains confined a little farther north, so tightened up the
gradient for rainfall chances towards the MA Turnpike overnight.
Minor tweaks to temperatures to reflect observed trends.
Still expecting rainfall to move offshore after midnight, with
clearing arriving from west to east late tonight.
A weak low pressure system travels along a cold front will cross
the region overnight. The best lift and moisture should remain
to our north into NH/VT, however some light showers are expected
mainly north of the MA Turnpike later this evening.
Precip chances end from W to E after midnight as the low moves
offshore and high pressure brings a dry NW flow. Decreasing
cloud cover is expected after midnight from W to east.
Overnight lows will generally be in the low to mid 40s across
the interior, and mid 40s to low 50s along the coastal Plain.
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
High pressure brings a reprieve, with mostly sunny skies. NW breeze
prevails through midday. Then as high passes overhead low level
winds become light. This may enable local sea breezes to develop by
mid afternoon. Highs in the mid 50s to low 60s, though a few
typically warmer locales may see mid 60s.
Transition period as the surface high pressure pushes to the NNE
into ME and eastern Quebec, and moisture-rich low pressure system
emerging out of the Gulf Coast region Fri night/Sat tracks into the
Great Lakes Region. While surface and mid level ridging keeps our
area dry to start the night, the low approaching from the west,
accompanied by a negatively titled trough, will send an increase in
moisture our way. For Sat night across southern New England, this
will mean increasing cloudiness, with showers/rain moving into at
least western portions of our area before daybreak Sunday. In that
area, have likely to categorical pops for late Sat night, and a
chance/slight chance before daybreak across eastern MA and RI.
An easterly breeze should allow surface dew points to rise by a few
degrees, then as we wet bulb as the rain moves in. Expecting
overnight lows mainly in the 40s.
.LONG TERM /SUNDAY THROUGH FRIDAY/...
* Widespread/soaking rainfall Sun with chilly temperatures
* Considerable cloudiness along with scattered showers Mon & Tue
* Unsettled weather at times Wed into Fri, but the best chance for a
period of widespread/heavier rain will be late Thu and/or Fri
* Above normal temps much of the next work week, especially at night
A widespread/soaking rainfall will impact the region Sun. Strong
shortwave energy across the eastern Great Lakes early Sun morning
will lift northeast into northern New England and Quebec by
afternoon. This will induce a modest southerly LLJ/Pwat plume that
is to 2 to 3 standard deviations above normal. There are still some
timing differences, but the widespread rain probably overspreads
most of the region Sun morning. If some of the slower solutions
verify, its possible that dry weather could persist into the mid
afternoon along the southeast New England coast. Either way, the
heaviest rain looks to occur Sunday afternoon. A secondary low will
develop near the south coast, which may result in heavier amounts in
that region. We also can not rule out a rumble or two of thunder
near the south coast, but probably not worth inserting into the
forecast at this point.
Rainfall amounts Sunday should range from 0.50 to 1.50 inches across
the region. Bands of heavier rain may result in the typical
ponding of water on some roadways, but no significant flooding issues
are expected. The modest southeast LLJ will allow for some gusty
winds along the coast to develop, but at this time do not expect the
need for any wind headlines.
Temperatures will be quite cool most of Sunday, mainly in the upper
40s to lower 50s with even middle 40s in the higher terrain. A
secondary low pressure system developing on the south coast may
allow the warm sector to flirt with the south coast Sun evening. If
that happens, some of those locations might spike into the lower
60s but probably not until the evening hours.
Steady rain will continue into part of Sunday evening, especially
across eastern New England. Otherwise, scattered light showers and
patches of drizzle may linger overnight at least along the coast
with onshore flow. Low temps will mainly be in the middle 40s to
the lower 50s.
Monday and Tuesday...
High pressure across the eastern Canadian Maritimes with weak low
pressure offshore will result in moist onshore flow. The result
will be an abundance of clouds and scattered showers at times
with drizzle possible too. While the entire period will not be
a washout, rather gloomy conditions expected. Overall, mild
temperatures will persist. Highs mainly between 55 and 65 with
the coolest readings likely along the coast. Low temps will be
significantly above normal given the clouds and onshore flow,
generally in the middle 40s to the lower 50s.
Wednesday through Friday...
There remains some uncertainty in the timing of a highly anomalous
trough that will develop over the western and central U.S. and how
quickly that moves east. Given the upper level ridging off the
southeast coast and a general agreement between the ECMWF/UKMET and
GGEM going with the slower solution. The GFS seems to be lost the
last few days and way too progressive given the above factors. With
that said, relatively mild temps may continue into Friday
(especially at night). The best chance for a period of widespread
showers may be sometime late Thu or even Fri, but the exact timing
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Saturday Night/...High Confidence.
Mainly VFR with a few showers likely through early morning
Saturday north of the MA Turnpike. May also see some patchy fog
develop toward daybreak. So while VFR conditions dominate, may
see some localized MVFR to perhaps even localized/brief IFR
Any lingering lower CIGS along the coast should improve to VFR
during the morning. NW winds 5-15 kts becoming light from a NNE
direction during the afternoon. Local sea breezes probable
during mid to late afternoon.
Thru midnight Sat night, VFR with increasing/lowering clouds. Then
for late Sat night MVFR/IFR conditions possible across interior MA
and northern CT with low ceilings and rain developing. E/SE winds 5-
KBOS Terminal...High confidence in TAF. Potential for renewed sea
breeze development during Sat afternoon.
KBDL Terminal...High confidence in TAF.
Outlook /Sunday through Wednesday/...
Sunday: Mainly IFR, with local MVFR possible. Windy with gusts
up to 30 kt. RA, patchy FG.
Sunday Night: Mainly IFR, with local MVFR possible. Windy with
gusts up to 35 kt. RA likely, slight chance SHRA, patchy FG.
Monday: MVFR/IFR conditions possible. Breezy. Chance SHRA.
Monday Night through Tuesday: Mainly MVFR, with areas IFR
possible. Breezy. Chance SHRA.
Tuesday Night: Mainly MVFR, with local IFR possible. Chance
Wednesday: Mainly VFR, with areas MVFR possible. Chance SHRA.
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Saturday Night/...High confidence.
Tonight and Saturday...
Relatively light winds and seas across the coastal waters
through Saturday. As a result, local sea breeze development is
possible once again during Saturday afternoon.
A weak low pressure crosses the water tonight. Showers will be most
likely across the waters east of MA, while the waters near and south
of the Cape/Islands may remain dry. Could see briefly reduced
visibility if any heavier showers develop. A few lingering showers
possible around daybreak Sat, otherwise dry weather expected.
E/SE winds developing, with gusts around 20 kts
possible along the southern waters. Slight chance of rain.
Outlook /Sunday through Wednesday/...Moderate to high
Sunday: Small Craft Advisory to marginal Gale Force wind
developing. Rough seas. Rain, patchy fog. Areas of visibility 1
to 3 nm.
Sunday Night: Moderate risk for gale force winds with gusts up
to 35 kt. Rough seas up to 10 ft. Rain, chance of rain showers,
patchy fog. Areas of visibility 1 to 3 nm.
Monday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Rough seas up to 10 ft. Chance of rain showers.
Monday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Rough seas up to 10 ft. Chance of rain
Tuesday: Winds less than 25 kt. Rough seas up to 9 ft. Chance
of rain showers.
Tuesday Night: Winds less than 25 kt. Areas of rough seas.
Chance of rain showers.
Wednesday: Winds less than 25 kt. Seas up to 5 ft. Chance of
* Pockets of Minor Coastal Flooding Likely Mon & Tue along the
eastern MA coast
High astronomical tides may result in some splash over or perhaps
very minor coastal flooding on Sunday with onshore flow associated
with our rain event. However, the potential for more widespread
minor coastal flooding will be around lunch time on Mon, Tue and
perhaps even Wed along the eastern MA coast. Boston has an 11.9
foot astro tide Mon and a 12.0 on Tue. This coupled with
onshore flow and 5 to 10 foot seas just offshore will likely
result in pockets of minor coastal flooding during these astro
tides. Coastal Flood Advisories will likely be needed.
MARINE...Gale Watch from Sunday afternoon through Sunday evening for
Gale Watch from Sunday afternoon through late Sunday night for
Area Forecast Discussion
National Weather Service Caribou ME
1026 PM EDT Fri Oct 25 2019
Low pressure will track eastward across the Gulf of Maine
overnight. High pressure will return Saturday into early
Sunday. Another area of low pressure from the Great Lakes will
approach Sunday afternoon and track well south of the Gulf of
Maine Sunday night. High pressure builds westward into the area
Monday into Tuesday. A cold front will approach Wednesday.
.NEAR TERM /THROUGH SATURDAY/...
1030 PM Update...
Only significant adjustment was to the temps to adjust them
downward a degree or two across the wnw areas where clearing has
allowed temps to drop in the upper 20s. Clouds are filling back
in per the IR satl imagery. Daycrew had this handled quite well.
Radar showing the highest returns along the coast attm ahead of
that weak low. KBHB(Bar Harbor) reported light rain in the last
hr. The HREF and RAP handling things quite attm. Minor tweaks
were done to the precip chances to account for the latest radar
and HREF/RAP blend. The rain is expected to shift quickly to the
ese overnight and remain light.
An upper level trough in the northern stream is approaching
from the Great Lakes region tonight. This trough will induce
weak cyclogenesis along a stalled frontal boundary tonight. The
baroclinic zone and resultant weak low will pass to the south of
the forecast area tonight. The low will generate rain in
southern zones late this evening through the night. The most
precipitation will occur along the Hancock County coast where
total amounts may exceed a quarter inch. Further north, the
passage of the upper trough could generate a few snow showers
towards daybreak in northern Aroostook County. While upper
levels are cold, boundary layer temps are marginal and deeper
moisture will only last an hour or two. As such, it`s difficult
to foresee any widespread measurable accumulation. As the upper
trough exits, gusty northwest winds will commence. Gusts may
briefly reach 25 mph in the morning, but will quickly subside as
high pressure builds through Saturday. The high and associated
subsidence is expected to produce clearing during
Saturday...especially in southern zones. There is good cold air
advection tonight into Saturday with H850 temps dipping towards
minus 6C on Saturday. Even with less cloud cover than today,
highs will several degrees cooler than today`s readings.
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
A high pressure ridge will be in place over our area at the
start of the period. A low in central Illinois with a warm front
extending east to the coast of New York and a cold front
extending south to the Gulf of Mexico will be the next system to
affect our area. By late Sunday morning the high will build
east as the low and associated front move east. The low moves
northeast to Eastern Lake Huron. The warm front into SW Maine,
and the cold front south along the East Coast. Sunday evening
the low continues to move Northeast into Southwestern Quebec. A
new low forms on the front over Eastern New York. The warm front
extend into Eastern Maine. Early Monday morning, the energy
from the parent low transfers to the new stronger low now over
Cape Cod. This low is forecasted to move SE well away from our
area. Higher pressure will ridge back across the area for the
end of the period.
Loaded a blend of the GFS/NAM/ECMWF/GEM to smooth out the minor
differences in the models.
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
A high pressure ridge will be in place across the area at the
start of the period. A trough across Quebec north of the ridge
will be the next system to affect our area. A low will develop
along the trough and move east across Quebec pulling the trough
into NW Maine Wednesday morning. The trough will interact with a
low moving north along the Atlantic Seaboard. The trough will
become a warm front and remain across Maine, as the low
continues to track north along the coast. The low will track
across Maine Thursday evening, then on into the Maritimes Friday
morning. Higher pressure will ridge into the area through the
end of the period.
Loaded a blend of models to smooth out the minor differences.
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
NEAR TERM: VFR conditions will continue until later tonight when
MVFR will become the predominant condition into Saturday
morning. Can`t rule out a brief snow shower with IFR vis at
sites such as FVE, Clayton Lake and CAR towards daybreak
Saturday. By late Saturday morning through the remainder of the
day, VFR is expected at all terminals.
Saturday evening through Sunday afternoon...VFR with increasing
clouds and decreasing ceiling beginning Sunday morning.
Sunday afternoon through Monday morning...MVFR falling to Low
MVFR to IFR conditions in rain Sunday evening.
Monday morning through Monday evening...MVFR with scattered
showers, becoming VFR Monday evening.
Monday evening through Tuesday morning VFR becoming MVFR in
showers Tuesday morning.
Tuesday morning through Wednesday...MVFR to Low MVFR with
NEAR TERM: Light winds and seas decreasing towards 1 to 2 feet
will be the story into tonight. Rain will develop later this
evening and continue into late tonight. The end of the rains
will correspond with a sharp wind shift to the northwest and a
few gusts could reach 25 kt, but will not be issuing an advisory
at this time as the duration of 25 kt gust potential is very
brief. The northwest winds will keep gusting to 20 kt into
SHORT TERM: Winds and seas below SCA Saturday evening through
Sunday afternoon. Winds and seas building to Small Craft
Advisory levels Sunday evening. Winds and or seas will remain
above SCA criteria through Tuesday evening.
Area Forecast Discussion
National Weather Service Goodland KS
511 PM MDT Fri Oct 25 2019
.SHORT TERM...(This evening through Saturday)
Issued at 109 PM MDT Fri Oct 25 2019
Water vapor imagery and 500mb height RAP analysis showed a closed
low slowly tracking east-southeast today along the Oklahoma/Texas
border. Sunny skies and light winds prevailed across the tri-state
region on the backside of the system. At 1 PM MT, temperatures
ranged in the upper 50s to low 60s.
Weak ridging extends across the area overnight while the OK/TX low
moves slightly east. Clear skies and light winds are expected to
continue across the region as temperatures fall into the upper 20s
to low 30s.
Westerly downslope flow helps temperatures climb into the 70s on
Saturday. Enjoy the warmth while you can. A cold front is set to
move through during the evening hours and it will be the start of
much cooler weather for the area. This looks to be a dry frontal
passage; however, breezy north winds are expected behind the front
overnight. Meanwhile, an upper trough digs towards the Central
Rockies from the Pacific Northwest. This disturbance generates some
light snow chances that start to enter the forecast area from the
northwest late Saturday night as temperatures fall into the 20s and
.LONG TERM...(Saturday night through Friday)
Issued at 200 PM MDT Fri Oct 25 2019
Focus for this period will be the two rounds of snow that will move
across the forecast area before the middle of next week. For the
first round, latest guidance continues to show a deepening trough
over the western CONUS through early next week. As this trough
deepens then swings across the Plains, it will bring heavy snow to
the Central Rockies. The higher snowfall amounts continue to be
over the mountains in CO where the lift will persist longer, with
much lower amounts on the Plains. Am not very impressed/concerned
about the potential for no more than a few inches of snow occurring,
with the highest amounts occurring in western parts of Yuma, Kit
Carson, and Cheyenne counties. Due to orographic effects, there may
be a localized area of higher snowfall amounts in western Kit Carson
County. The rather broad, fairly quick moving trough from the west
is not supportive of warning snow amounts. Looking at the CIPS
Analogs the probability of receiving 2"+ is less than 30% for the
forecast area. The 90th percentile (10% chance of occurring) is
low end warning criteria. The majority of the snow is not forecast
to occur until Monday, as the trough swings across the Plains and
continues east. Bottom line, there will be low snow amounts in
East Central Colorado as early as Sunday, spreading across the
rest of the forecast area Monday, ending Monday night.
The second round of snow will move through Tuesday into Wednesday as
another broad trough moves across the Plains along a similar path to
the previous one. There is disagreement as to how quickly this
second trough will move across the Plains. The GFS has the trough
moving quickly across the Plains, similar to the speed of the prior
trough, and keeps the trough as an open wave. The ECMWF lingers the
trough over the Four Corners region and deepens the trough into a
closed low. As the closed low tracks east, it moves across KS. By
the time the ECMWF moves the closed low east, the GFS has its open
wave over the Ohio River Valley. The last three runs of the ECMWF
favor the trough tracking across KS, and the last 6 runs of the GFS
(which all have an open wave) show a similar trend. Even though
there is still a question about how quickly the second trough will
move across the forecast area, model trends point toward a more
favorable path for precipitation than with the first round of snow
to move through.
Aside from snow, the big change for upcoming weather is the drastic
drop in temperatures behind the cold front Saturday night. Once
that front moves through highs may not even approach normal for a
week. The current temperature forecast for the first part of next
week is more likely to trend cooler over the coming days. Wind
chills by mid week will fall to the single digits above and below
zero during the night/early morning hours.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 511 PM MDT Fri Oct 25 2019
High pressure expected to dominate the region`s weather thru the
forecast period. A cold front is expected to traverse the area
near the end of the forecast period...affecting KMCK before 00z
Sunday. VFR conditions until then.
Winds for KGLD, light/variable thru 03z Saturday, then SW around
10kts. By 14z, SW 10-20kts becoming SE around 10kts by 22z just
ahead of the frontal passage.
Winds for KMCK, light/variable thru 07z Saturday, then SW around
10kts. By 21z, N 10-20kts due to front pushing thru the area.
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
850 PM CDT Fri Oct 25 2019
Updated for evening discussion.
Shortwave ridge in advance of TS Olga has diminished the
precipitation considerably over southern portions this evening.
This will not last long, though, as Olga makes landfall around
midnight and quickly pushes northward overnight. So, an increase
in showers will be seen after midnight with some thunderstorms, as
well. Enhanced wind fields around the center of circulation will
lead to strong convergence, strong shear and possible severe
convection with wind and tornadoes being the primary threats.
Latest HRRR data showing some interesting convective structures
around and to the east of the circulation center./GG/
Prior discussion below:
A rather wet pattern will continue through much of the short term.
Warm front still remains close to the coast with lower to mid 70s
dewpoints remaining in this part of the state. Dewpoints have been
slowly increasing across portions of our forecast area with readings
in the mid 60s. As the low pressure system in the Gulf continues to
move north through the remainder of the afternoon and evening, this
warm front is expected to also move north, bringing a bit more
moisture and instability further inland. Models tend to agree that
this low will move north in the vicinity of the I-55 corridor this
evening and overnight. As it does, the best parameters for strong to
severe storms, including better shear profiles, will be across the
east and southeast parts of Mississippi, potentially reaching as far
west of the I-55 corridor. It is in this region where we previously
expanded both the slight and marginal risks for severe weather. The
main concern will be from damaging winds and tornadoes, coming
roughly from 3am through daybreak. A fly in the ointment may come in
how far north this more unstable air is able to go.
The other concern will be from flash flooding potential. Most
locations have seen steady moderate rain for most of the day with
around 1 to 2 inches common but some locations in the east have seen
amounts upwards of 3 inches. Another 1 to 3 inches will occur
through tonight into tomorrow before all is said and done. Some
rates will be higher/heavier rainfall in convective bands later
tonight into tomorrow and going Flash Flood Watch seems good for
As the surface low deepens and moves inland, given the tightened
pressure gradient, there may be some gusty winds not associated with
more robust convection. Winds will be out of the south/southeast
during the night but will hold off adding anything to the HWO this
afternoon for this threat.
Models continue to quickly push convection out of the region by
early afternoon or perhaps even by noon. Clearly should come
gradually from west to east through the afternoon and evening.
Temperatures have been and will continue to be tricky given rain and
cloud cover. Of course with a northward advancing cold front,
temperatures will remain steady to increase overnight tonight. Highs
tomorrow will roughly be in the 60s and lower 70s. /28/
Saturday night through next week...
A cooler airmass will filter into the region Saturday night
as the surface front pushes east of the region and the upper low
ejects to the north. Some moisture will remain in the lower levels
as surface high pressure increases. Some fog will be possible
throughout the region on Sunday morning. Temperatures will be
slightly below average on Sunday as dry conditions prevail.
Monday will remain dry with temperatures closer to average as the
surface high remains parked over the area.
As with the last several forecast packages, there is still little
agreement amongst guidance moving into midweek. As a trough over
the Rockies deepens on Monday, SW upper flow will begin to
increase over the lower MS River Valley in response. As the
trough begins to migrate eastward on Tuesday, a weak disturbance
embedded in the pattern will help to push a weak front towards the
region. This is where the agreements end.
The GFS still holds on to the drier solution with only light PoPs
in the region on Wednesday into Thursday with cooler air
filtering into the region behind the front. The Euro`s solution
continues to be the wetter of the two through the period as a deep
upper closed low crosses the Rockies and approaches the MS River,
keeping rain, storms, and warmer temperatures in the region
through early Friday.
We will continue to lean towards the warmer, wetter midweek
solution due to the performance of the Euro so far in this
transitional season but the forecast remains low confidence until
there is more consensus amongst guidance.
00Z TAF discussion: Mostly IFR/LIFR conditions will continue
through the night with widespread rain and isolated thunderstorms.
After sunrise Saturday, conditions will slowly improve to MVFR as
the widespread rain tapers off to showers. East and southeast
winds will prevail at 10 to 20 knots with gusts around 25 knots
tonight eventually becoming more south to southwest after
.PRELIMINARY POINT TEMPS/POPS...
Jackson 64 68 50 71 / 90 72 12 4
Meridian 62 75 50 70 / 95 96 18 5
Vicksburg 60 65 50 71 / 93 57 12 3
Hattiesburg 66 72 50 71 / 92 82 12 4
Natchez 59 63 50 71 / 88 49 12 2
Greenville 58 64 50 68 / 96 60 12 3
Greenwood 60 68 50 69 / 95 76 12 3
MS...Flash Flood Watch through Saturday afternoon for MSZ018-019-
LA...Flash Flood Watch through Saturday afternoon for LAZ007>009-015-
AR...Flash Flood Watch through Saturday afternoon for ARZ074-075.
Area Forecast Discussion
National Weather Service Paducah KY
1011 PM CDT Fri Oct 25 2019
Issued at 1011 PM CDT Fri Oct 25 2019
Forecast remains largely on track. However, some concern remains
with regard to exactly how much rain will fall and where. The
models have largely been off with respect to convection over the
Deep South this evening, with the NAM and GFS depicting a bullseye
of higher QPF much further west than reality. Meanwhile, the ECMWF
and RAP seem to have a better handle on current conditions. What
impact this will have on conditions going forward remains unknown.
However, even the ECMWF and RAP both develop a swath of heavy
rain across the region late tonight into Saturday morning, with
the heaviest rain still within the Flash Flood Watch area. As a
result, will keep the watch and QPF forecast as is for now.
Another concern remains strong winds on Saturday in response to
the tightening gradient in the vicinity of a low pressure system
forecast to track northeast into the lower Ohio Valley. Increased
the strongest wind gusts into the 35 to 40 mph range across much
of western Kentucky, southwest Indiana, and southeast Illinois
during the late morning and afternoon. These estimates may be a
bit conservative, depending on the amount of low level mixing that
occurs. A broken line of showers and isolated storms may bring
even stronger wind gusts to that region during the late morning
through mid afternoon, with some gusts of 50 to 55 mph or greater
possible. The issuance of a Wind Advisory may eventually become
necessary on Saturday, but will ultimately leave that up to the
midnight shift to make the final call.
.SHORT TERM...(Tonight through Saturday night)
Issued at 309 PM CDT Fri Oct 25 2019
The current weather system pushing rain northward from the
Tennessee Valley this afternoon continues to hold surprises,
especially in the spatial location of the heaviest QPF (forecast
rainfall amounts) and rainfall rates tonight and early Saturday.
In coordination with the NWS Forecast office in Memphis,
introduced a Flash Flood Watch for late this evening through
midday on Saturday. It was a toss up between going with a Flood
Watch versus a Flash Flood Watch, but it looks like there may be a
roving 3-4 hour period within a deformation zone with the upper
low that efficient rainfall rates may exceed established short
term flash flood guidance. The Flash Flood Watch falls within
WPC`s Day 1 (tonight) and Day 2 (Saturday) Slight Risk for
Excessive Rainfall. There is lower confidence in the duration and
intensity of rainfall north of Route 13 in southern Illinois, so
keep the watch generally south of that area.
Utilized WPC Rainfall as primary QPF focus, which has lowered
precipitation amounts markedly Saturday afternoon and dropped
overall storm total rainfall amounts down by at least an inch.
The mesoscale challenge will be determining the intake of drier
air into the low from the west in the 15z-18z Saturday time frame.
This will also be key as to the potential for overturning of
theta-e air in the mixed layer and the capability of downward
mixing of air and the stability of the boundary layer with its
gradient winds around the low. Do have a mention of up to 40 mph
winds over west Kentucky in the gridded forecast Saturday
afternoon. Will not rule out some damaging wind potential for any
convective line segments that develop along the eastern half of
the WFO PAH forecast area Saturday afternoon. Will be a close
call. At this time, SPC has our area only outlooked for general
Thunderstorms for Saturday.
Utilized a blend of the HREF, RAP, ESRL HRRR, and NAM high
resolution guidance, overlaid with NAM-WRF (ARW version) and
Canadian Guidance for sub-synoptic sensible weather features.
.LONG TERM...(Sunday through Friday)
Issued at 309 PM CDT Fri Oct 25 2019
There are two primary targets of opportunity for forecast adjustment
in the long term. The first is with a weak frontal/system passage
Monday night. This system is scarce of mean moisture and depth in
the atmospheric column over the PAH FA. Its best and deepest pool of
moisture stays catafrontic to our north, where the dynamical energy
associated with its passage is also better. And the thermal profile,
while cooling post frontally, remains just warm enough to preclude
mention of anything other than liquid pcpn. The Builder`s use of the
blend did output slight chance pops, mainly for our northwest-most
counties, Monday evening...which stands for this writing...pending
collaboration. If trending continues, however, removal of these pops
altogether may be warranted with this first/weak system`s passage.
The 2nd and better target of opportunity for forecast adjustment
occurs 24-48 hours later, with another frontal/system passage. This
system will introduce a little better moisture, a little better
lift/via dynamical energy, and a little better thermal profile
(favoring a potential wintry mix), to make things a little more
interesting. That said, we are not ready to go out on a limb just
yet with a Tuesday night/Wednesday morning event, other than it
would appear confidence is increasing in a pattern change that
favors the late week cooldown that the extended range outlooks have
been hitting upon. It appears the collaborative strategy for now is
to mention the brief/wintry mix chance pop late Tue night-early
Wed., with a system passage sometime Wed night-Thursday. This ending
time period is also an area that may be looked at for future
forecast adjustment, as some deterministic runs suggest ending pcpn
much earlier, like by Wed evening, versus 6-12 hours later. This
could be the blend averaging the runs, so we`ll wait til more member
agreement comes into play before changing the ending time.
As for temps, we`ll see 60s early in the week, fall into the 50s,
then thru the 50s, with even some 40s by the end of the week (in our
northwest) for highs. Lows will follow a similar course, from the
40s into/thru the 30s, with some 20s showing up (along with their
killing freeze potential) by the end of the week.
Issued at 628 PM CDT Fri Oct 25 2019
Significant impacts to aviation anticipated. Through the evening,
cigs will gradually lower across the area to MVFR to local IFR,
with MVFR vsbys as rains increase from south to north across west
KY and southeast MO, into southern IL and eventually southwest IN.
Overnight, east winds will increase with some gusts to or above
20 kts with time, and MVFR to IFR cigs and vsbys due to widespread
showers. LLWS may become an issue late tonight into Saturday
morning as strong winds just off the surface from the southeast
increase to 35 to 50 kts. Showers will continue Saturday, with
some decrease in coverage with time, as winds veer more south,
southwest, with gusts 20 to 30 kts expected, highest over west KY
into southwest IN.
IL...Flash Flood Watch through Saturday afternoon for ILZ088>090-
MO...Flash Flood Watch through Saturday afternoon for MOZ086-087-
KY...Flash Flood Watch through Saturday afternoon for KYZ001>009.
AREA FORECAST DISCUSSION
National Weather Service Charleston WV
1021 PM EDT Fri Oct 25 2019
Light rain spreads from south to north along a warm
front Saturday. A cold front sweeps across the region Sunday
with more beneficial rain. The area gets a break until midweek.
.NEAR TERM /THROUGH SATURDAY/...
As of 1020 PM Friday...
Blended recent HRRR guidance into POPs in an effort to better
reflect current radar trends. The current band of light rain
stretching from the Tug Valley into the central WV mountains
should taper off as an upper level ripple pulls away and the
focus for precipitation transitions closer to the surface low
crossing the Gulf Coast.
As of 140 PM Friday...
Clouds will continue to thicken through the overnight hours in
response to approaching increasing mid-level moisture associated
with southern stream low currently stationed over eastern Texas.
Think a bulk of overnight activity will be limited to very light
precipitation or virga, mainly across the southern coal fields.
Increasing moisture/forcing for ascent associated with
strengthening southerly-southeasterly H850 flow around the east
side of the aforementioned low will provide a focus for rain
Saturday morning with the heaviest accumulations across eastern
Kentucky, western West Virginia, northwestern Virginia and
southeastern Ohio from late morning into early afternoon with
mostly light accumulations further east away from the nose of
the jet and closer to the influence of downsloping winds off the
H850 strengthens further through Saturday afternoon/evening
exceeding 50KTs for a bulk of the region by 00Z. With warm air
advection, do not see any large scale mechanisms to transport
enough of this momentum to the surface to support any wind
highlights for the lowlands, but will certainly be breezy
downwind of higher terrain. For the higher elevations, do look
to approach wind advisory criteria along the highest ridgetops
Saturday evening and especially early Sunday morning as H850
flow approaches 70KTs. Will highlight this risk in the HWO for
now and allow the midnight shift to evaluate.
Despite freight train of low level moisture, PoPs through the
afternoon mostly fall into the slight chance/chance category
without a strong focus for ascent. This will change
significantly as a cold front slams into moisture laden profiles
late Saturday night/early Sunday morning with continued strong
moisture advection into the frontal zone.
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
As of 235 PM Friday...
For the start of this FCST period models are picking up on the
downslope effect for the western slopes of the mountains and
lowlands. Possible lighter rain showers will exist in these
areas, however will pick up in intensity through the night into
Sun. The bulk of the rainfall from the system to the west will
drop over the Ohio River Valley. The lowlands will see more rain
as the surface low moves north and drags a cold front through
early on Sun. Generally around 1 inch in total rain is expected
although the lowlands may struggle to squeeze out even 3/4 of
Southeasterly flow along with downsloping and a tight pressure
gradient across the mountains will create strong winds
areawide and a low level jet as high as 75kt. Therefore,
expecting very gusty winds along the front picking up late Sat.
night and persisting into Sun. morning. The strongest winds
will be along the mountains and their western slopes, however
areawide will endure gusty wind which could cause downed trees,
isolated power outages and flying debris. Holding off on a wind
advisory for now since soundings are saturated with warmer air
being advected in which will prevent the majority of the
strongest winds from mixing down to most areas ahead of the cold
front through Sunday morning. Mentioned strong gusty winds in
the HWO for now.
Models are now slower with the exit of the cold front than previous
runs since a system that was suppose to help push it along quicker
did not really pan out, so the area will experience rain showers
into Sun. afternoon with possible lingering showers in the
mountains until the evening. With drought conditions still in
effect, not expecting any flood issues although any prone flood
or low lying areas are at slight risk of experiencing issues.
This cold front is fairly weak as far as temperature gradients
are concern. Temperatures will not fall that much overnight Sun.
so basically went with central guidance, however guidance is
banking on clouds hanging around which I believe will clear out
sooner. For this reason I nudged temperatures down slightly.
Temperatures will then stay seasonable for the next few days
with a nice break from unsettled weather.
.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 235 PM Friday...
A nice break from unsettled weather continues through this
period, but unfortunately a fairly active weather pattern will
set in starting around midweek. A broad and deep upper level
trough will slide east over the area and create numerous short
waves with potential to spawn a few surface lows. These features
are forecast to affect the area in one way or the other through
Friday, possibly longer, as a vort max is prog to impact the
CWA into the weekend.
The aforementioned feature will bring in cold air starting
Thurs. Since models diverge slightly around this time frame,
went with guidance and left in chances for rain since timing and
location is uncertain. Contrary to guidance, decided to bump
temps down since confidence is high in the trough sweeping over
the area and advecting Canadian air to the region. Some of the
models are in unison with my decision leaning towards a colder
bias for Thurs. and Fri. morning presenting the chance for snow
flakes in the air during these periods, especially in the higher
terrain. Central guidance added some frost into the forecast
for Fri. morning and opted to leave it in since temps should get
down to around freezing.
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
As of 720 PM Friday...
Rain making it to the ground a bit sooner than previously
expected, so main change to TAFs was to add light rain showers
across the south this evening. Still have a dry layer of air
near the ground and an overcast sky, so not expecting much fog
to form following this rain. Rain will remain light, so VFR
expected through the night. More widespread rain expected to
move from south to north on Saturday morning. For now kept this
VFR, but some dips into MVFR will be possible. Winds will pick
up out of the southeast Saturday, with gusts of 15-30 kts. This
could also lead to LLWS Saturday afternoon/evening as a strong
southerly low level jet noses through. With gusty surface winds
expected, and fairly unidirectional flow in the low levels, did
not include LLWS in the TAFs right now.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z SUNDAY...
FORECAST CONFIDENCE: High.
ALTERNATE SCENARIOS: Patchy fog may form tonight. MVFR
visibility possible in rain showers Saturday.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE SAT 10/26/19
UTC 1HRLY 00 01 02 03 04 05 06 07 08 09 10 11
EDT 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07
CRW CONSISTENCY H H H H H H H H H H H H
HTS CONSISTENCY H H H H H H H H H H H H
BKW CONSISTENCY H H H H H H H H H H H H
EKN CONSISTENCY H H H H H H H H H H H H
PKB CONSISTENCY H H H H H H H H H H H H
CKB CONSISTENCY H H H H H H H H H H H H
AFTER 00Z SUNDAY...
IFR or worse conditions Sunday along a cold front with heavy
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
853 PM MDT Fri Oct 25 2019
Issued at 842 PM MDT Fri Oct 25 2019
02z surface analysis had low over central SK with cold front into
northwest MT with 5-8mb/3hr pressure rise bubble behind it. 00z
KUNR quite dry giving us a glorious Friday. Water vapour showed
upper trough moving across southwest Canada into the northwest US.
Two main pockets of energy, one spinning over southern AB and
another pushing into WA/OR per 90kt jet streak. This trough will
progress east/southeast through Saturday pushing the cold front
into the CWA very late tonight and out of the CWA Saturday
afternoon. Cold air advection will be fairly robust with 3-5mb/3hr
pressure rises per latest RAP forecast, but rises will weaken
throughout the day. Result will be a period of gusty winds for the
northern squeeze areas northeast/east of the Black Hills.
Attention then turns to lift with southwest jet steak as it dives
into the central Rockies. Guidance depicts a moderate band of
850-700mb frontogenesis from central WY into far southwest SD by
00z Sunday. At the same time low level dry air continues to
advect into the CWA with Td/s dropping into the teens. This will
be the battle in place for accumulating snow. HREF guidance shows
highest probabilities for 0.25-0.50" QPF near the far southwest
SD/NE state line.
Tweaked the forecast for latest thinking through 12z Sunday and
came up with near winter weather advisory amounts for Fall
River/Oglala Lakota areas and marginal wind advisory conditions
for Rapid City and the surrounding squeeze zones.
So, yeah. Lots of text to basically say will hold onto
headline-less forecast until full suite of new data arrives
.DISCUSSION...(This Evening Through Friday)
Issued at 207 PM MDT Fri Oct 25 2019
Deep NW flow upper trough will dig into the central CONUS this
weekend, supporting very cold conditions across a large portion of
the country by the end of the weekend. Warm SW flow has supported
a WAA regime and has allowed for a mild fall day across the
region, with most places on the plains in the 60s. Strong cold
front will quickly move through the region Sat, with gusty NW
winds expected by afternoon on the plains. Frontside impulse will
support increasing chances for snow over the SW third Sat
afternoon, best chance over far SW SD into NE WY where 1-3 inches
looks likely Saturday afternoon into Sunday morning. Southward
bias of best FGEN per faster frontal surge has continued to shift
the best snow chances south as drier air will work into the region
quicker. An adv may be needed for Fall River county if snow
amounts remain around forecast values. Otherwise, gusty NW winds
will likely support wind adv winds in the lee of the Black Hills
Sat afternoon. Will defer any headlines to the next shift when a
good handle on timing and hazards should be attained. Very cold
unsettled NW flow will dominate through early next week, with re-
enforcing rounds of CAA expected per clipper systems. This will
support temps 20-40 degrees below seasonal norms Sunday through
Tues (coldest over the far west), with the coldest day being Tues
where many places will struggle out of the teens and 20s in the
western half. Slow warming trend expected afterward, with mainly
dry conds and below normal temps continuing.
.AVIATION...(For the 00Z TAFS Through 00Z Saturday Evening)
Issued At 529 PM MDT Fri Oct 25 2019
VFR conditions expected through tonight. Gusty southwest winds
are expected tonight over northeast WY and the higher Black Hills.
A sharp cold front will move through the area from northwest to
southeast starting late tonight, exiting the area Saturday
afternoon. Behind it, conditions will deteriorate. Expected
widespread MVFR CIGS by afternoon with local IFR/LIFR conditions
over northeast WY into the Black Hills due to clouds and then
increasing coverage precipitation. Precipitation will start as
rain, but change to snow most areas by the end of the period.