Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/20/17
Area Forecast Discussion
National Weather Service Denver/Boulder CO
738 PM MDT Fri May 19 2017
.UPDATE...
Issued at 738 PM MDT Fri May 19 2017
Upper level low over far eastern Colorado will continue to lift
north-northeast overnight. Wrap around showers will slowly shift
eastward tonight. By morning, expect the showers to be east of the
state. Some snow may mix in over the higher locations of Lincoln
and Washington counties. Adjusted the forecast for higher pops in
this area. Scattered snow showers over the mountains will end this
evening as the airmass stabilizes. Low temperatures are expected
to drop into the lower 30s tonight. Cloud cover and a moist
airmass will make it tough to drop into the 20s along the Front
Range and across the eastern plains.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 215 PM MDT Fri May 19 2017
The upper trough anchored to a 500 mb low over south central CO
remains elongated along a north-south axis along the spine of the
Rockies. On GOES-16 one can see a stark contract in cloud
coverage from west-to-east across the state with generally clear
skies west of the Divide and mostly to overcast skies east of the
Divide. Under these clouds, area NWS radars continue to detect
north-south bands of mostly light precip crossing the eastern
half of the CWA. Only a few showers were still being detected in
the local high country. However, that should change as
temperatures warm with increasing sunshine. On the plains, have
witnessed a slow westward expansion in shower coverage with
transport winds becoming more oriented southeasterly in direction.
HRRR and RAP show this showery precipitation advancing as far
west as the eastern edge of the I-25 urban corridor by 22z today.
More aggressive is the ARW which shows this precip/QPF against
the northern foothills by 21z and and in the Denver metro area
about an hour later. These models also indicate an area of heavier
QPF forming across the northeast corner of the state late this
afternoon and lingering through early this evening. They indicate
up to 0.30-0.40 inch of QPF and 1-2 inches of snow out there.
Elsewhere on the plains, the showery precip this afternoon should
mainly fall as rain, although the heavier showers east of the
urban corridor and up near the Wyoming border may be a mix of rain
and snow. Additional snow accumulation at higher elevations
generally under 3 inches.
Tonight...the 700-500mb low is progged to trek northeast across
sern CO early and nwrn KS late, the mid-level flow over nern CO
become northerly again. This will advect drier air down from WY,
but not necessarily cooler air as temps up there are slightly
warmer than they were down here today. The boundary layer air
filtering down will also be drier, and with an end to the QG lift
and orographic forcing, should see an end to nearly all shower
activity by midnight or so. The question remains, how fast will
low and mid-level clouds clear over the plains. That would mean
the difference between a night of sub- freezing temperatures or
not. At present, a freeze warning is out for the plains which go
into effect at 2 AM MDT. As I see it now...do not expect clouds to
clear sufficiently over the eastern half of the plains zones
before 12Z to allow temperatures to fall below 0C. However, closer
to the foothills, I guess temps could fall to just below freezing
for a long enough time to warrant holding onto the warning.
Therefore, will keep the freeze warning for zones
038..039..040..041..042 and 043 up along the foothills.
On Saturday...As the upper low will continue its northeastward
track across Nebraska, causing the flow aloft to become
northwesterly. This will warm and further dry out the plains
airmass. Latest guidance indicates highs tomorrow in the mid to
upper 50s on the plains, 40s/lower 50s in the high country. That`s
about 10-12 deg f below average for the plains. In the high
country, models show a weak disturbance embedded in this
northwest flow moving down over the nrn mtns during the morning
hours and generating scattered snow showers. Snow amounts should
be light. Expect to see this batch of high country precip winding
down around midday. Then during the afternoon, isolated heat
generated showers forming over the high ridges. High temps in the
high country Friday will be about average for the date.
.LONG TERM...(Saturday night through Friday)
Issued at 215 PM MDT Fri May 19 2017
Zonal flow will prevail over the CWA Saturday night into Sunday
evening. Then an upper trough will push across Colorado on Monday.
Northwesterly flow aloft is progged Monday night. Downward
synoptic scale energy is progged Saturday night into Sunday
evening, then weak upward motion is over the CWA into Monday
evening. Normal diurnal wind patterns appear to dominate the low
level winds Saturday night into Monday. A decent cold front with
upslope behind is progged into and across the plains late Monday.
The upslope continues Monday night. For moisture, there is quite a
bit progged Saturday night well into Sunday night...with some
clearing into midday Monday. Moisture increases Monday afternoon
and night. This is a tiny bit of CAPE over the high mountains
early evening. There is better CAPE around late day Sunday, with
the highest values over the mountains and foothills. There is less
CAPE late day Monday, and only over the mountains. There is a bit
of measurable precipitation over the mountains Saturday evening.
There is more for late day Sunday and it covers most of the of the
forecast area. Same for Monday. Will go with a few alpine showers
Saturday evening. Will need higher pops Sunday and Monday, even
some "likely"s in the high country. For temperatures, Sunday`s
highs are 0-1.5 C warmer than Saturday`s. Monday`s highs are 1-3 C
cooler than Sunday`s. For the later days, Tuesday through Friday,
north-northeasterly winds aloft prevail Tuesday into Wednesday as
an upper ridge moves into the CWA Thursday and Friday. Tuesday
night into Friday morning look to be dry. Temperatures will get
back to seasonal normals from Wednesday onward.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 738 PM MDT Fri May 19 2017
Ceilings in the Denver area are 1000 feet MSL and are expected to
slowly rise through the overnight hours. Around 09Z, lower clouds
are expected to be east of the area. Good chance that mid and
high clouds will linger into Saturday morning. If there is
clearing, there will be a chance for fog around 12Z. Scattered mid
and high clouds are expected for Saturday with light winds.
&&
.HYDROLOGY...
Issued at 215 PM MDT Fri May 19 2017
A flood advisory will remain in effect through at least tomorrow
afternoon for the South Platte River near Kersey in Weld County,
along the South Platte River near Weldona in Morgan County, and
along the South Platte River near Balzac in Logan, Morgan and
Washington Counties.
Runoff from the recent heavy rainfall and the heavy snow cover in
and near the Front Range will continue to make its way down the
South Platte River. This will cause flooding of lying areas along
the river from west central Weld County through Morgan County.
Only light precipitation is anticipated in these areas during the
next 24 hours.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Freeze Warning from 3 AM to 8 AM MDT Saturday for COZ038>043.
&&
$$
UPDATE...Meier
SHORT TERM...Baker
LONG TERM...RJK
AVIATION...Meier
HYDROLOGY...Baker
Area Forecast Discussion
National Weather Service Caribou ME
1027 PM EDT Fri May 19 2017
.SYNOPSIS...
High pressure in Canada will slowly build into the area through
the weekend. The next weather system will bring rain to the
area Monday.
&&
.NEAR TERM /THROUGH SATURDAY/...
1025 PM Update...
Clouds have moved out of the region for the most part w/some
scattered clouds down across the downeast region. Temps have
dropped off w/the clearing as colder air is moving into the
region from Canada. Temps across the far nw areas already down
in the upper 30s such as Clayton Lake down to 38F as winds have
dropped off below 6 mph. IR and WV satl imagery indicate an
upper trof to swing across the region overnight. This feature is
picked up well by the latest run of the RAP which shows winds
picking up again to around 10 mph overnight. This should allow
for the blyr to stay mixed which should keep most of the frost
at bay. There is a risk that some low lying areas could see some
patchy frost by early Saturday morning as temps hit lower 30s
in those areas. Therefore, kept some patchy frost in across far
n and w. Otherwise, temps in the mid/upper 30s for the rest of
northern areas w/around 40 central and downeast areas.
Previous Discussion...
1028mb sfc high sitting south of James Bay wl begin to build
into the CWA thru the end of the near term pd. Nw winds wl start
to lighten by late aftn Sat with temps rebounding into the m60s
for Downeast and u50s acrs the north.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
Strong high pressure is expected to be building in from the
northwest at the beginning of this period. The high will move
across the state and eventually to the south of New England by
Sunday Evening. Clouds will increase late Sunday with rain
moving into western areas Sunday Night. Rain will continue to
spread northeastward Monday. Have used a blend of the GFS, NAM,
and ECMWF for populating grids.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Low pressure is expected to develop over Southern New England
Monday Evening. The low will move northeast through the Gulf of
Maine Tuesday resulting in rain across the region. A cold front
will move across the State Tuesday. High pressure will build to
the east of New England Wednesday. Low pressure will then
approach from the southwest Wednesday Night and pass to the west
of New England Thursday.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
NEAR TERM: MVFR cigs expected for the next 2-4 hours at FVE,
CAR and PQI before becoming VFR. VFR at all other terminals next
24 hours. NW winds will remain gusty for most terminals through
tomorrow afternoon.
SHORT TERM: VFR conditions expected Sunday. VFR/MVFR conditions
expected Monday. MVFR/IFR conditions are expected Tuesday and
Wednesday.
&&
.MARINE...
NEAR TERM: Winds will gust to near 25kts this evening as a cold
front crosses the water. This will likely be just below SCA
levels, thus the advisory has been cancelled. Seas will remain
below 5 feet through Saturday.
SHORT TERM: Have used the NAM to populate wind grids Sunday and
Monday. Will lower model wind speed from NAM 10 percent due to
cold sea surface temperature making boundary layer Stable. Will
transition to the Super Blend winds late Monday. For Waves: For
Sunday expect northerly wind wave for primary wave group and a
secondary southerly swell system subsiding during the day. A
southerly wind wave is expected Monday into Tuesday, then a
southerly fetch will build from the Gulf of Maine southward on
Wednesday in response to deepening low pressure over the
northeastern U.S. Will use the Nearshore Wave Prediction System
for wave grids.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...Hewitt
Area Forecast Discussion
National Weather Service State College PA
946 PM EDT Fri May 19 2017
.SYNOPSIS...
Cooler and drier air will settle in for the weekend. Low
pressure will track west of Pennsylvania early next week, with
the trailing cold front coming through the region Sunday night
or Monday.
&&
.NEAR TERM /UNTIL 8 AM SATURDAY MORNING/...
Dry line now into Happy Valley. Surface dewpoints and ThetaE
dropping precipitously as the cooler and drier air moves in from
the NE. That boundary was visible on radars - curving from NC
PA over to Long Island a little earlier. Isolated showers remain
across the souther tier. The large convective complex moving
into western PA is falling apart without good dynamic support
and waning CAPE/solar energy. While most of the showers coming
in from the west will dwindle to only orphaned-anvil
rain/sprinkles, it is still worth a small POP through the next
couple of hours in the west. Clouds tonight left over from the
convection to the west may keep temps up a deg or two.
Prev...
Dry air still having trouble sliding southward. But, the dewpoints
are now below 60F over half of the CWA. Showers over the far srn
tier appear to be weaker with each scan, and the anticipation is
that this trend will continue as heating and CAPE decrease.
However, we will leave in chc POPs in the Laurels for the next
hour or two. Then a little lull, but the Laurels may again need
higher POPs later tonight as the MCS currently over OH slides
to the east. The weakening trend should also hold for that area
of convection as well, and not much may survive past PBZ`s area.
Prev...
The meso analysis shows the cold front settling into my
southern zones with the RAP indicating low level Theta-E
advection going negative over all but the far southern stripe of
the CWA. This is where the scattered convection is firing in
the moderately unstable airmass along and ahead of the front.
The best Cape of 1000-2000J extends along the MD border and the
trend shows the atmosphere becoming more stable as the
cool/negative Theta-E advection works south through the region.
Wind shear has decreased markedly since this morning so the
severe threat now seems to be mainly from an isolated pulse
storm in the still warm and humid airmass. The convective
threat will decrease as we lose heating and the front continues
its push south.
Basin average QPF will be generally 0.10 of an inch or less in
southern PA. However, localized amounts of 0.25-0.50 inch are
possible in places impacted by heavier showers and storms.
High temps today ranging from the mid/upper 60s across far NW
PA, to the upper 80s in the Lower Susq Valley will be a good
10-15 deg above normal across all but the far NW zones, where
they will be near to slightly above normal.
A lingering shower will be possible through mid evening before
drier air works into all areas by midnight. Lows will range from
the mid 40s to mid 50s north to south with lower dewpoints
making for more comfortable sleeping conditions than the last
couple of nights.
&&
.SHORT TERM /8 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
Saturday is expected to remain dry, with the exception of a
shower possibly working into the far SW before the sun goes
down. Increasing mid/high clouds could mar what otherwise would
be a nearly perfect mid spring day.
Highs generally in the 70s will be a few degrees either side of
normal for mid May.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
High pressure over New England will slowly retreat off the East
Coast on Sunday. The chance for showers will begin to increase
from west to east through the day, ahead of a cold front
approaching from the Midwest. Some thunder is possible by Sunday
aftn across the west.
The cold front should cross central Pennsylvania Sunday night
into early Monday, accompanied by scattered showers and possibly
some thunder. A weak area of high pressure will build in behind
the front, providing a pleasant Tuesday.
It looks like things may turn unsettled again during the middle
to later part of next week, as upper-level low pressure drops
into the Great Lakes and surface low pressure develops over the
Mid-Atlantic region. This could bring a round of cooler, wet
weather to the region Wed into Thurs.
The upper-low should begin to lift out by Friday, allowing
conditions to slowly improve.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Generally VFR will continue across central Pennsylvania through
Saturday. Isolated MVFR cigs this evening will dissipate by 02z.
VFR conditions are expected overnight and into Saturday.
The next system will introduce a slight chance of showers into
the west Saturday evening, with more widespread showers
developing later Sunday and Sunday Night.
.OUTLOOK...
Sun...Showers and thunderstorms likely west advancing east by
late afternoon and evening.
Mon...Becoming VFR with showers ending from west to east.
Tue...VFR.
Wed...Widespread restrictions developing with showers and
thunderstorms.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...DeVoir/La Corte
NEAR TERM...Dangelo/La Corte
SHORT TERM...La Corte
LONG TERM...Evanego
AVIATION...La Corte
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
643 PM CDT Fri May 19 2017
.Discussion...
Issued at 321 PM CDT FRI MAY 19 2017
The upper level low continues to slowly make its way toward our
area, bringing us the potential for a couple rounds of storms. The
first round, currently entering the area, brings with it the
potential for severe weather. The severe weather window is now
through a couple of hours after sunset. The general set up is an
upper shortwave is heading over the area from the southwest, while
at the surface an east/west oriented stalled synoptic boundary is
in place near the MO River. The biggest area of concern is going
to be south of this boundary in central MO, along an east/west
oriented surface outflow boundary located just south of I-70. The
clouds have been able to clear some in this area which has
allowed instability to increase to about 500-1000 J/kg. 0-6 km
shear values of around 40-45 kts are also just enough to support
organized convection. Dewpoints across this area have already
reached the mid 60s, so there is also plenty of moisture. The
main threats with these storms are going to be hail up to about 1
inch, strong to damaging winds, with an isolated tornado or two
also possible. Therefore, we have issued a Tornado Watch in
central MO, which is in effect until 10 pm tonight.
There is also the potential for a second round of storms moving
through later tonight. As time has gone on today it has started to
look like we may not get quite as much QPF as originally thought.
The HRRR shows the bulk of the second round moving through
southern/eastern MO, dry slotting KC and surrounding areas early
on, while the NAMNest and RAP are showing more rain over the area
before the dry slot moves over us. Despite these differences,
PWAT values are averaging out around 1.5 across the area which is
well above the normal for this time of year, 0.99. In addition,
the ground is saturated from yesterday`s storms. Therefore, if
convection does get going behind the first round of storm, it
won`t take much to have some flash flooding and river flooding
concerns. Have gone with somewhat of a blend in the forecast and
think most of the forecast area will see about 1-2 inches of rain
from the second round of storms. The flash flood watch will
continue due to the potential and we will continue to monitor
river levels.
Things should dry out west to east by tomorrow morning as the
surface low and upper level low move off to the northeast over the
Great Lakes. A cold front will move through behind the convection,
cooling temperatures into the 60s and 70s for the rest of the
weekend. A surface high will settle in behind the cold front with
more zonal flow aloft. This will keep us dry until Monday, when a
shortwave moves over the area. Can`t rule out severe weather
given the time of year and overall pattern.
&&
.Aviation...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 643 PM CDT FRI MAY 19 2017
Combination of IFR and MVFR conditions will prevail across the
terminals this evening as more storms develop to the west in
Kansas and then sweep northeast across the Kansas-Missouri
state line. Current timing of prevailing storms and TEMPO groups
highlight the timing at this time, but confidence is low on this,
so anticipate the need for many updates this evening as storms
develop and dissipate. Have also highlighted some low level wind
shear early Saturday morning as the low level jet swings across
the state line along with the upper level weather feature driving
this activity.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
KS...Flash Flood Watch through Saturday morning for KSZ025-057-060-
102>105.
MO...Flash Flood Watch through Saturday morning for MOZ011>014-
020>023-028>031-037>039-043>045-053-054.
&&
$$
Discussion...Grana
Aviation...Cutter
Area Forecast Discussion
National Weather Service Lincoln IL
859 PM CDT Fri May 19 2017
.UPDATE...
Issued at 859 PM CDT Fri May 19 2017
An MCV and line of storms will progress east-northeast across our
forecast area over the next 3-5 hours. Instability and shear
parameters continue to point toward low potential for severe wind
and/or hail from the storms in our area. The latest HRRR indicates
a break will develop behind this line, but another wave will
arrive across our SE counties later tonight. Those storms also
should be sub-severe. The better chances for severe weather now
look to be focused later Saturday afternoon for areas along and
east of I-57, when damaging wind, large hail and even a few
tornadoes could develop.
The main updates for the rest of tonight were to the timing and
coverage of expected showers/storms. Thunder potential will be
higher south of I-72/74, but a few strikes will be possible in our
entire forecast area overnight. A blanket of low clouds will keep
our low temps closer to current readings, with little change in
airmass expected through sunrise.
Updated forecast info is already available.
&&
.SHORT TERM...(This evening through Saturday)
ISSUED AT 253 PM CDT Fri May 19 2017
Frontal boundary is currently located just north of the I-70
corridor this afternoon, with an extremely sharp temperature range
over the forecast area. 2 pm readings ranging from the mid 40s
north of Peoria, to the mid 80s from Flora to Lawrenceville. A
surface low which has moved into southwest Indiana should start
to drag this boundary a bit southward through the evening hours,
although the significantly colder conditions should stay north of
I-72.
Large convective complex over Kansas and eastern Oklahoma this
afternoon is now edging into western Missouri, and should start
moving into western Illinois after midnight. The area immediately
south of the I-72 corridor received 2 to 5 inches of rain last
night. This would be the area most subject to any flash flooding.
However, right now the system looks to be progressive enough, and
more in a north-south axis, to mitigate the threat of additional
flooding. This will be something we will watch closely over the
next several hours.
.LONG TERM...(Saturday night through Friday)
ISSUED AT 253 PM CDT Fri May 19 2017
Large upper low currently over Colorado will shift into the
central Plains by early Saturday, then lift northeast to near the
Iowa/Minnesota border by mid evening. The frontal boundary will
surge northward and place all of the forecast area in the warm
sector by around midday. Have not changed forecast high
temperatures much, mainly low-mid 80s except for some 70s
northwest of I-55. The GFS brings CAPE values over 1200 J/kg over
all of the forecast area by early afternoon, while the NAM limits
the higher values mainly across eastern Illinois. Main threat for
any severe weather would mainly be over the eastern CWA, where
0-6km bulk shear values reach 40-45 knots during the afternoon. By
early evening, the trailing cold front will be pushing into the
western CWA, and should largely be out of the forecast area by
sunrise Sunday.
The upper low will not be breaking any speed records early next
week, mainly loitering just northwest of Lake Superior through
Monday. By Monday night, a secondary lobe of energy will break
free, and swing southeast into the Midwest, where it will slowly
edge eastward through Thursday. In this particular pattern,
temperatures will be relatively cool during mid week, with highs
down into the 60s Tuesday and Wednesday, before starting to
recover on Thursday. Rain chances will increase quite a bit Monday
night into Tuesday as this low starts to move through, with some
wraparound showers lingering into Wednesday. May be enough
instability for a few thunderstorms on Tuesday, mainly over the
eastern CWA.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 642 PM CDT Fri May 19 2017
Central Illinois will see a continued break in the showers/storms
before the next complex reaches near SPI between 02z-03z, then
lift northeast toward PIA and BMI. Mesoanalysis tools show a much
more stable airmass across central Illinois, so the storms should
begin to weaken once they reach Illinois from eastern Missouri.
We still expect IFR to low MVFR clouds to persist ahead of the
rain, then drop to IFR across the board for late tonight into
Saturday morning. Cloud heights should improve to MVFR toward mid
morning, with VFR conditions at all TAF sites Saturday afternoon.
Storm chances will be mainly confined to this evening for western
TAF sites, then Saturday afternoon for eastern TAF sites.
Winds will be generally E-NE this eve, then shift to E-SE late
tonight and Sat morning, with southerly winds becoming established
Sat afternoon. Wind speeds should remain 10-15kt for much of this
TAF period.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Shimon
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Shimon
Area Forecast Discussion
National Weather Service Lake Charles LA
1047 PM CDT Fri May 19 2017
.DISCUSSION...
Wx map shows continued modest SE flow over the coastal waters at
15-20 kts, with SCEC continuing overnight. Inland, SE winds ~ 5
mph north of I-10, 5-10 mph along the I-10 corridor, and 10-15 mph
coastal parishes/counties expected to continue. This will keep
temps in the mid/upper 70s overnight, with only a minimal chance
of showers possible.
DML
&&
.AVIATION...
MVFR ceilings across SE TX/SW LA affecting BPT this evening, and
likely to affect LCH shortly, and continue through the overnight
hours. For AEX/LFT/ARA, intermittent MVFR ceilings mainly due to
SCT/BKN layer during the 10-14z time frame. Continued VCTS by 20z
Saturday for all sites, with a Prob30 group for TSRA at AEX from
00-06z Sunday as the frontal boundary sags further south.
DML
&&
.PREV DISCUSSION... /issued 629 PM CDT Fri May 19 2017/
DISCUSSION...
Update for 00z TAFs. Ceilings will be VFR to MVFR this evening
through the overnight hours. Expect the winds to decrease after
sunset. Will carry VCTS starting around 17-18z on Saturday area-
wide.
PREV DISCUSSION... /issued 438 PM CDT Fri May 19 2017/
DISCUSSION...
Despite both LAPS and SPC RAP meso-analysis indicating little to
no CINH remains over the area amid more than ample CAPE/instability,
overall lack of forcing for ascent has thus far kept convection
in check with radar data still showing mainly isolated showers.
This activity should mostly wane during the evening hours, with
attention then shifting west to upper low emerging east of the
Rockies and its associated SFC low and trailing CDFNT.
Global model guidance is in fair agreement through the weekend,
depicting the upper low lifting through the Plains and into the
northern Great Lakes with a building ridge off the West Coast
helping to maintain a broad trof across much of the Central CONUS.
The SFC low is progged to track NE in tandem with the upper low,
with the trailing CDFNT slipping lazily through the area tomorrow
night and into the Gulf waters by Sun night. Divergent flow aloft
between the upper low lifting out to the NE and a subtropical jet
nosing across northern MX and into the NW Gulf will provide
additional lift amid what will continue to be a very moist and
unstable airmass. Scattered to perhaps numerous showers and
thunderstorms are expected during the afternoon. 0-6km shear is
progged to be borderline, but given the available instability,
isolated severe storms (mostly of the pulse-type variety) are
possible. Could be a short break in activity for a time tomorrow
evening, but convection should increase after midnight as the
front begins to progress into the area.
An active westerly jet aloft coupled with the weak initial frontal
passage and subsequent stalling over the northern Gulf will
result in elevated rain chances continuing over the area SUN and
MON, with a southward push of jet energy from Canada driving a
stronger front through the area TUE night into WED. Much drier and
cooler air to filter in behind this second frontal passage, with a
very nice (and unseasonably cool) mid to late week period
expected.
13
MARINE...
Moderate southerly winds will persist through tonight as the
region remains between strong high pressure ridging across the
southeast US and low pressure over the Southern Plains. Expanded
the Exercise Caution headline to include all Gulf waters through
Saturday morning. Winds will decrease Saturday as a cold front
approaches the area and the pressure gradient loosens. This front
is forecast to stall over the coastal waters Sunday, and remain
nearly stationary until a second and stronger front pushes through
the area Tuesday night into Wednesday. Good chances of showers
and thunderstorms are forecast Saturday through Tuesday, with much
drier and cooler air behind the second front bringing an end to
precipitation.
13
&&
.PRELIMINARY POINT TEMPS/POPS...
AEX 73 87 70 82 / 10 70 60 60
LCH 74 86 71 85 / 10 50 40 60
LFT 76 87 74 86 / 10 60 40 70
BPT 76 87 72 87 / 20 40 40 60
&&
.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...Small Craft Exercise Caution until 7 AM CDT Saturday for GMZ450-
452-455-470-472-475.
&&
$$
AVIATION...08
Area Forecast Discussion
National Weather Service Memphis TN
905 PM CDT Fri May 19 2017
.DISCUSSION...Showers and thunderstorms associated with a mid
level shortwave trough have diminished in coverage across the
Mid-South this evening. However, upstream WSR-88D radars have
shown an increase in activity across central Arkansas, and the
ongoing convective complex over the Southern Plains. Short term
models this evening thus far are having some difficulty resolving
the overall evolution of upstream convection. Latest HRRR
indicates the showers and thunderstorms will gradually move
across southern Missouri and Arkansas overnight reaching areas
near the Mississippi River towards daybreak. Will only make slight
adjustments to account for short term trends. Forecast overall
remains in good shape for the time being.
CJC
&&
.PREV DISCUSSION... /issued 609 PM CDT Fri May 19 2017/
UPDATE...
Updated to add 00Z Aviation Discussion.
PREV DISCUSSION... /issued 156 PM CDT Fri May 19 2017/
DISCUSSION...
Showers and thunderstorms continue to develop across much of the
Mid-South this afternoon thanks to a warm and humid airmass.
This activity should begin to die out around sunset.
Next chance for convection will then come overnight as a squall
line is expected to push into Northeast Arkansas after midnight.
The line should die as it approaches the Mississippi River due to
the strength of the upper level ridge. Otherwise, expect a muggy
night across the Mid-South with lows ranging from the upper 60s to
lower 70s.
Leftover boundaries from the overnight convection will likely be the
initiation points for shower and thunderstorm development by mid-day
Saturday. Additional development will occur ahead of an
approaching cold front that will move into Northeast Arkansas
during the afternoon hours. Chances for showers and thunderstorms
will continue through Saturday Night as the front pushes through
the CWA.
Damaging winds may be possible with the squall line that
is expected to move into Northeast Arkansas late tonight.
Otherwise, any storm that develops Saturday afternoon into
Saturday Night will have the potential to become severe due to the
warm and unstable airmass that will be over the Mid-South. Highs
on Saturday will range from lower 80s across Northeast Arkansas to
the upper 80s across Northeast Mississippi.
Some lingering convection may continue on Sunday across Northeast
Mississippi. Otherwise, expect cooler and drier air to filter
into the Mid-South behind the departing cold front.
High pressure will then build into the region Sunday Night into
Monday providing the area with pleasant conditions. Lows will be
in the 50s with highs will be in the mid 70s to around 80 degrees.
Another cold front will move through the Mid-South on Tuesday
which will bring chances for showers and thunderstorms back to
the area.
Wednesday will be a cool day across the area with chances for
light showers due to an upper trof moving through the region.
Highs will only be in the mid 60s to lower 70s.
High pressure will build into the area for the remainder of the
week. Temperatures will gradually warm back into the lower 80s for
highs by Friday.
KRM
&&
.AVIATION...
00Z TAFs
Scattered showers and thunderstorms should continue through
02-03Z and gradually diminish. A complex of showers and
thunderstorms may develop and affect JBR and perhaps MEM overnight
towards daybreak Saturday. Additional showers and thunderstorms
expected Saturday afternoon as a cold front begins to move across
the Lower Mississippi Valley. S winds between 4-8 kts will
increase to 9-12 kts on Saturday. MVFR conditions possible
Saturday morning. Otherwise, VFR conditions expected elsewhere
outside of thunderstorms.
CJC
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1049 PM CDT Fri May 19 2017
.UPDATE...
Issued at 902 PM CDT Fri May 19 2017
Just some minor changes made to both PoPs and QPF for impending
rain tonight/Saturday.
First, HRRR/HopWRF/NAM/RAP all show a slowing trend with northward
push of precip tonight, which makes sense given our persistent dry
east flow. The slowing wasn`t much and amounts to about a 2 hour
delay in precip arrival at any one location.
For QPF, trended it tonight/tomorrow closer to what we are seeing
from the RAP and other short term hi-res models. They show a
heavier area of QPF coming into SW up into central MN tomorrow.
This is associated with the precip currently down around Omaha.
This region of precip will find itself at the nose of the LLJ in a
zone of good isentropic upglide, moisture convergence, and fgen as
it lifts north through the day Saturday. Current run total QPF
looks very similar what the 21z SREF has with storm total rainfall
amounts a little over an inch out toward Willmar and Redwood
Falls.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 259 PM CDT Fri May 19 2017
Showers continue to fall apart across far southern Minnesota this
afternoon as they encounter dry air. The next round is beginning
to take shape across northern Kansas into western Missouri. Models
have slowed down its northward progress a bit, reaching southern
Minnesota after 3-4 am and expanding into central MN/western WI
between 7-9 am. Rain will persist all day Saturday into Saturday
night, although the most intense rain should last for maybe 3-4
hours beginning shortly after its onset. Widespread rainfall
amounts of a half to one inch appear likely.
Temperatures will be about 5 degrees cooler than normal tonight,
but 20 degrees colder than normal Saturday with highs only in the
mid 40s to lower 50s.
.LONG TERM...(Saturday night through Friday)
Issued at 259 PM CDT Fri May 19 2017
The extended looks cool, cloudy, and wet through the first half of
next week. Things will dry out by the middle of the week, but at
this point not putting much faith in the drier solutions.
Temperatures will be near or below the seasonal average for late
May, which should help make the case that this month could be below
normal in the Twin Cities for the first time since August of 2015.
Increased chances for pops on Saturday night and Sunday as the upper
level system brings cool air, low clouds, and a few rain showers.
Forecast models show a brief reprieve on Monday, but forecast
soundings show quite a bit of moisture in the H900-700mb layer so
increased the cloud cover and lowered the temperatures for Monday.
On Tuesday another area of vorticity will sweep across the region
which will lead to forcing for ascent, clouds, and another round or
seasonably cool rain showers. Decreased Tuesdays temperatures as
well with a cool, cloudy forecast in mind.
Looking ahead, models are generally in good agreement that northwest
flow and subsidence should bring drier conditions across the region
for the middle of the week, but another shortwave will follow for
the end of the week. There are still timing differences between the
models, but overall not optimistic that a prolonged period of warm
and dry weather will set up across the Midwest between now and the
end of the month.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1049 PM CDT Fri May 19 2017
Edge of rain lifting into the Sioux City area at 11pm. Delays made
to 00z TAFs still look good, so made no changes to rain and
mvfr/ifr cig timing with the 06z TAFs. We`ll have a dry slot
working into ern MN/wrn WI after 00z, with steady rain expected to
end pretty quick once it moves in and is also why we have
transitioned TAFs from STC on east over to DZ to end the TAF. The
end of the TAF will also feature a sfc low centered somewhere
between MSP and EAU at 6z Sun. Given discrepancies in the
placement of the low, confidence is low in wind direction at the
end of the TAF and they`ll be dependent on where the low tracks.
Finally, NAM soundings continue to show AXN cooling enough to
where they are awfully close to supporting snow at AXN Saturday
night. Have not introduced snow at this point, but it will have to
be watched for AXN.
KMSP...High confidence in the forecast until the dry slot arrives.
Expect us to be stuck with IFR cigs when the dry slot gets here,
but precip may cut off completely, with vis not being as bad as we
currently have. Our wind forecast for Saturday night sticks close
to what our gridded forecast has, which is a blend of the models,
but with the low passing close to MSP Saturday night, changes in
the wind direction forecast for Saturday night as we work
through the day Saturday and get more confidence for where the low
is heading.
/OUTLOOK FOR KMSP/
Sun...MVFR. Chc -shra. Wind WNW at 15G25kt.
Mon...VFR. Chc MVFR/-shra. Wind NW at 5-10kt.
Tue...VFR. Chc MVFR/-shra. Wind N 5-10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
UPDATE...MPG
SHORT TERM...BORGHOFF
LONG TERM...JRB
AVIATION...MPG
Area Forecast Discussion
National Weather Service Paducah KY
648 PM CDT Fri May 19 2017
.UPDATE...
Issued at 639 PM CDT Fri May 19 2017
The AVIATION section has been updated for the 00Z TAF issuance.
&&
.SHORT TERM...(Tonight through Sunday night)
Issued at 323 PM CDT Fri May 19 2017
Scattered showers and storms have built northward into west
Kentucky in the last few hours, but all indications are that this
activity will move east and dissipate by sunset, leaving the
entire area dry for most of the evening. In the meantime, we
cannot rule out a stray strong to severe storm, but given the
number of updrafts competing for the available instability and
relatively weak wind fields over the region, organized severe
weather is not expected.
The most recent HRRR output still tries to bring an MCS into at
least southeast Missouri and southern Illinois after 09Z and into
Saturday morning. It appears that the severe potential with this
system will be to our north. With south southwesterly flow through
the column, any significant winds would be associated with
northwest to southeast oriented portions of the line. However,
heavy rainfall will be a concern, especially where the leading line
orients itself parallel to the upper flow.
The models are in reasonably good agreement in dragging the cold
front through our region late Saturday night into Sunday morning.
The convective potential should drop off quickly with the frontal
passage, but we maintain small PoPs through the day Sunday. After
the MCS tonight into Saturday morning, the convective evolution is
unclear. The primary upper-level system will be well north of the
area and we will not have the synoptic cold front in play yet.
Best bet is that we will see scattered development through the
day, especially near any outflow boundaries that remain in play.
Not terribly concerned with severe weather, but given the
potential surface airmass that may develop, especially south of
any outflows, a stray strong to severe storm cannot be ruled out.
Once again, with anomalously high moisture content, locally heavy
rainfall will be the biggest concern. At this time, it is not
obvious which areas may be hardest hit with multiple rounds of
heavy rain tonight through Saturday night so will not be issuing a
Flash Flood Watch.
Still looking much more pleasant behind the front Sunday and
Sunday night with temperatures a bit below normal on Sunday.
.LONG TERM...(Monday through Friday)
Issued at 323 PM CDT Fri May 19 2017
We will have sfc high pressure in our vicinity on Monday but that
system will shift east through the day. Another frontal boundary
will be incoming from the west. Various models as well as the GFS
ensembles seem to have a pretty decent handle on the timing, and
this was the case yesterday as well. We should see dry weather
through the evening hours on Monday, but after midnight Monday night
and into Tuesday, precipitation chances increase. How quickly the
front makes it through Tuesday into Tuesday evening is still a bit
in question.
However, there will be a break in the action after the frontal
passage Tuesday evening or late Tuesday night. The upper level
trough/low will move across the area on Wednesday. This will mean
more clouds, more chances for showers and a downright cool day with
highs only in the 60s. Models have their differences on how quickly
this upper system departs on Wednesday night. May have to linger
some POPs in that period...higher POPs east. We could have a chance
to see lows in the upper 40s in some areas Wednesday night.
We will see improving conditions on Thursday, as well as an increase
in our temperatures and more sunshine as sfc high pressure builds
back into the region. The upper flow transitions to a more
flat/zonal flow by Friday with no large signals for any major
chances for rain.
&&
.AVIATION...
Issued at 639 PM CDT Fri May 19 2017
Medium confidence in the forecast with much of dependent on
convection movement and/or development. The rest of the evening
should be dry for most of the area. Scattered storms moving north
out of AR will stay far west of KCGI toward the Ozark foothills
and eventually dissipate through the evening. TS chances increase
overnight into Saturday morning. It appears that we will most
likely see an MCS move northeast through all or a portion of the
area 09Z-15Z, but there could be development ahead of it as well,
beginning as early as 03Z. Emphasized the early morning MCS
potential with a wind shift and VCTS at all sites except KOWB.
Kept it VFR for now, but IFR or lower conditions will be possible
if the MCS develops. The forecast beyond 18Z is greatly dependent
on morning convection. Morning convection could work over the
atmosphere precluding the development of afternoon storms. Have
included PROB30 groups at all sites for the development of
convection during the afternoon given the uncertainty of the MCS.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
SHORT TERM...DRS
LONG TERM...CW
AVIATION...ML
Area Forecast Discussion
National Weather Service Pueblo CO
917 PM MDT Fri May 19 2017
.UPDATE...
Issued at 914 PM MDT Fri May 19 2017
Updated forecast to allow WSW to expire across the southern
mountains. Also adjusted POPs as precip is decreasing rather
rapidly across most of the region. /Hodanish
UPDATE Issued at 519 PM MDT Fri May 19 2017
Given current satellite and radar trends, decided to extend the
ongoing Winter Weather Advisory for the Southern Sangres until 9
pm this evening. An additional 2 to 4 inches of new snow expected.
Incorporated latest obs data. Moore
&&
.SHORT TERM...(This evening through Saturday)
Issued at 300 PM MDT Fri May 19 2017
An upper level low will continue tracking slowly east-northeast acrs
CO this evening and is forecast to move into south central NE by 12Z
Sat. There have been areas of persistent light rain acrs the
southeast plains today, with showers increasing over the eastern and
central CO mtns. Web cams on La Veta Pass show snow falling and it
looks like it is accumulating a little.
The NAM, GFS and HRRR show good pcpn coverage along the Sangre de
Cristo and Wet mtns and the central mtns and far sern plains thru
the evening hours, with isolated to scattered showers elsewhere.
This could lead to a few additional inches of snow accumulations in
these mtn areas. Will leave the Winter Wx Advisory for the southern
Sangres in effect. As temps cool this evening, some of the lower
elevation showers may change over to snow, but little if any
accumulation is expected. By late night, as the low moves east of
the area, pcpn will end in most if not all locations, and clouds
will decrease from west to east. With the cloud cover decreasing the
temps will quickly cool and areas near the I-25 corridor are
expected to see temps drop into the upper 20s to lower 30s, thus a
Freeze Warning is in effect from the Monument Hill area to the NM
border.
On Saturday, drier northwest flow aloft will be over the area and
most locations will be dry. However, there is expected to be enough
instability and moisture over the area for a few afternoon showers
over and near the mtns. Temps will be warmer on Sat but will still
generally be about 10 degrees below average.
.LONG TERM...(Saturday night through Friday)
Issued at 300 PM MDT Fri May 19 2017
Saturday night through Tuesday...Models continue to indicate an
active pattern across the region through the first half of the week,
as northwest flow aloft with multiple shortwaves stretches across
Colorado. This will allow for scattered convection across the higher
terrain, and isolated activity for much of the lower elevations,
each day, though the highest potential for showers and thunderstorms
will occur Sunday through Tuesday morning. A couple of northerly
surges will drop cooler air south into the forecast area, one late
Sunday and another late Monday. Expect max temps in the 60s and 70s
on Sun, 60s to around 70F on Mon, then 50s and 60s for Tue.
Wednesday through Friday...an upper ridge builds into the desert
southwest for Wed, providing for dry conditions and warming temps.
The ridge edges to the east for Thu, allowing isolated mt convection
during the aftn. On Fri the ridge moves east and westerly flow aloft
pushes into the state, allowing for continued warming and isolated
mt convection during the aftn and eve. Temps are expected to warm
back into the 60s and 70s for Wed, then 70s to lower 80s for Thu and
Fri. Moore
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 300 PM MDT Fri May 19 2017
There will be the potential for showers in the vicinity of KCOS and
KPUB thru the evening hours. It`s possible KALS could also see a
shower but chances are fairly low. Showers could at times bring a
lower cloud deck that could be in the MVFR category. After about 05Z
the clouds are expected to decrease. VFR conditions conditions are
expected on Sat. There could be some afternoon showers near the
mtns west of KCOS Sat afternoon.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Freeze Warning until 9 AM MDT Saturday for COZ084>088.
&&
$$
UPDATE...Hodanish
SHORT TERM...28
LONG TERM...MOORE
AVIATION...28
Area Forecast Discussion
National Weather Service Blacksburg VA
1122 PM EDT Fri May 19 2017
.SYNOPSIS...
High pressure off the southeast Atlantic Coast will continue to
produce an unseasonably warm and humid southwest flow of air
across the forecast area into tonight. This will combine with an
approaching weak cold front to produce additional showers and
storms especially over the mountains on Saturday. Unsettled
weather will then continue through into early next week with
shower chances again increasing ahead of another cold front
arriving from the west by Monday.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 1115 PM EDT Friday...
Upped pops over the west based on latest trends. High-res
models/radar showing more agreement on nudging convection
further southeast toward the SW Va mountains into the NC
mountains overnight. Still should weaken with airmass
stabilizingbut some decent instabilities remain south of line
of convection in eastern KY toward the Cumberland Gap into the
NC mountains. Expecting less thunder north of a Bluefield to
Lexington VA line.
Previous discussion from 1012 pm...
A line of showers/thunderstorms shifting toward the
Greenbrier/Summers County area. High-res models having a hard
time keeping up with speed but have the general idea right of
best threat of showers through the overnight to stay across the
WV mountains into the Alleghanys and Mountain Empire.
00z RNK sounding showing SBCAPE of just under 1000 j/kg. RAP
mesoanalysis indicating best CAPE across eastern KY south into
NE TN. Storms over KY will have to be watched as they move into
this unstable air through the next few hours, though with
nighttime expect instability to weaken with time.
Previous discussion from late afternoon...
Overall shower/thunderstorm threat has ended, with lingering
showers east of Staunton River SP and over the NC/TN border near
Beech Mountain, NC.
High-res models are keen on keeping most of the forecast area
dry this evening, until convection upstream over northern
KY/southern Ohio shifts east-southeast toward our WV mountains
by midnight. Have updated pops to account for the little to no
coverage, and may have to dry it even more per latest radar
trends. Otherwise, forecast on track.
Previous discussion from mid afternoon...
Clusters of deeper convection continue to evolve mainly over
southern/southwest sections in an area of convergence just south
of a weak mid level wave passing to the north and on bottom of a
weak residual surface trough. Latest short term models drive a
loosely organized area of convection into eastern/southeast
sections through late afternoon so upping pops for a few hours
of likelys across the southern third into early evening.
Otherwise still expecting coverage to fade after sunset if not
sooner as best lift shifts back north closer to the surface cold
front in the southern Ohio Valley. Some of this coverage may
sneak back southeast into espcly northern portions of the area
overnight but should be quite widely scattered at this point.
However will leave in some low pops to cover this as well as for
the potential to see another complex clip the northeast sections
late. Should also see more patchy fog around espcly given
coverage of convection from earlier. Lows in the muggy 60s
overall.
Front will gradually backdoor in from the northeast on Saturday
but slower than earlier as models indicate building heights over
top the low level cool pool that will attempt to slip back
toward the Blue Ridge. This slower scenario would mean more
instability developing ahead of the boundary espcly from just
east of the Blue Ridge westward during the afternoon. Guidance
shows a lobe of high 850 mb theta-e over the western half
beneath good upper diffluence that could mean another round of
more widespread showers and storms outside of the far northeast
sections. Thus upped pops to higher chance/low likelys west and
kept chance to low chance eastern sections. Expect low level
northeast flow including lower dewpoints and stability to
gradually shift west by late in the day but all dependent upon
convective coverage and how much more it slows the boundary up.
High temps quite tricky with potential for southern and
southwest sections to zoom back into the 80s while the northeast
remains stuck in the cooler 70s per latest warmer Mos.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/...
As of 300 PM EDT Friday...
Surface front should finally spill westward into far western
sections Saturday night in the wake of earlier convection before
being bumped back slowly east on Sunday as the main upper
trough to the west heads northeast. May see a lull in overall
rain coverage Saturday night with mainly low clouds possibly
persisting Blue Ridge and some drying across the northeast. Kept
in some chance pops mainly mountains for now with only spotty
showers out east. Expect any significant cooling to stay just to
the north although some dewpoint drying could occur southwest to
the eastern slopes per latest Nam. Otherwise lows still
muggy...mainly low to mid 60s.
Surface cold front associated with the upper trough to the west
will drift east Sunday with its axis of deeper moisture working
into the mountains by later in the day. Guidance shows quite an
instability gradient from stability within deeper northeast flow
across eastern sections to modest Cape values over the west
where will be in the convergence zone of the residual front and
lift ahead of the cold front. Therefore going to a gradient of
increasing likely pops from west to east over the mountains
Sunday including some thunder to mainly lower shower chances in
the east in the afternoon. Highs should be much cooler as the
wedge and clouds remain in place resulting in highs mostly lower
to mid 70s at this point.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
As of 310 PM EDT Friday...
500 MB flattens during the first half of the week. Upper ridge
remains over the southeast and southern Gulf of Mexico. A piece of
the upper low redevelops and heads into the Ohio Valley by Thursday.
ECMWF has best lift and good short wave crossing the Mid Atlantic
region on Wednesday.
A cold front passes through the area early Monday. A second front
crosses through on Wednesday leading in a colder air mass over the
area for Wednesday and Thursday. ECMWF shows the potential for some
gusty winds behind Wednesday`s front. Expecting showers and
thunderstorms along each of the front with the potential for heavy
rain. Overall troffing and periods of rain will result in below
normal temperatures for much of the week. Have trended toward cooler
daytime temperatures for Monday through Friday.
&&
.AVIATION /04Z SATURDAY THROUGH WEDNESDAY/...
As of 710 PM EDT Friday...
Quiet evening aviation wise now that convection has exited east.
Will have to watch for fog formation overnight, especially where
it rained. However, next upstream wave will bring some clouds
back into the mix overnight which may hamper fog formation, or
keeping it from getting dense. Confidence high that IFR vsbys
will occur at BCB/LWB with MVFR LYH/DAN.
Frontal driven storms over the Ohio Valley this evening may
shift to near BLF/LWB after 04z, but confidence is low, so not
adding them to the tafs.
The front is forecast to enter the forecast area Saturday,
entering the area backdoor style with a northeast push of wind
Saturday and Saturday night. Models suggest that drier air may
now be slower to push west of the Blue Ridge during the
afternoon so added convection resulting in sub-VFR could occur
after 18z, so added VCTS at LWB/BLF/BCB. May see some MVFR cigs
in ROA/LYH once backdoor front move southwest.
Extended Aviation Discussion...
The front will then stall over or just south of the region
early Sunday. With the front over the area, there will be an
opportunity for added showers and thunderstorms, especially
during the peak heating hours of the day over the western
mountains by late Sunday. However expect combo of low clouds
within the wedge and showers over the west to result in sub-VFR
for most of Sunday. More widespread showers and storms may occur
ahead of the front Sunday night with added poor flying
conditions overnight. The front will cross the forecast area
Monday, dry weather returning Monday night into Tuesday. Another
front may then bring the next round of showers and subsequent
MVFR by Wednesday.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...JH/PM/WP
NEAR TERM...JH/WP
SHORT TERM...JH
LONG TERM...AMS
AVIATION...JH/PM/WP
Area Forecast Discussion
National Weather Service Shreveport LA
1009 PM CDT Fri May 19 2017
.DISCUSSION...
The Ern/Srn OK MCS has begun to shift E this evening, but still
remains ahead of a cold front analyzed from near a PNC, to just W
of OKC, to SPS and SNK line as of 0230Z. The mesoanalysis depicts
moderate MLCapes still in place ahead of the MCS over N TX/SE
OK/Wrn AR, with MLCapes of 2000-2500 J/Kg where lower 70 dewpoints
have advected back N in wake of the retreated morning mesoscale
bndry from this morning`s MCS which diminished just N of the
forecast area. The 00Z KSHV raob depicts that the strong capping
inversion evident just 24 hrs ago has eroded, with the KFWD raob
weakly capped by more unstable under the presence of stronger low
level shear. The short term progs do suggest that a 30-40kt Srly
LLJ will develop over the next few hours ahead of the MCS over E
TX/SW AR, which is supported by the latest KSHV VAD which depicts
30-35kts having already developed in the lowest 5kft. This should
aid in convergence along/ahead of the approaching MCS, before the
LLJ begins to veer more SW by 09Z over NE TX/SE OK/SW AR as the
available CAPE continues to diminish as well. Thus, a severe
threat mainly in the form of damaging winds with locally heavy
rainfall will be possible across the NW zones after 06Z, and have
inserted mention for these areas in the forecast update this
evening. Still not quite sure how far SSE the MCS will be able to
build before it weakens late, with the HRRR again playing catchup
with the ongoing convection, and the 18Z/00Z NAM much too slow.
Have tailored the forecast closer to the GFS, which to some extent
with the HRRR, does allow the convection to backbuild SSW along
the veering LLJ once the more diffluent flow aloft ahead of the
N-S upper trough begins to pivot more ENE into NE TX/SE OK
by/before daybreak Saturday.
For the update...did scale back pops especially over Deep E TX/N
LA, but did retain likely pops for the NW zones, tapering pops
down to chance from/NW of a JSO to GGG to just E of a TXK line.
The MCS should continue its weakening trend even beyond 12Z
Saturday, with additional convection likely developing throughout
the day along the lingering mesoscale bndrys and along the
attendant cold front set to enter the region Saturday afternoon
during peak heating. However, given the lack of significant deep
lyr shear, the convection should be sct/multicellular in nature
and outflow driven, almost typical of summertime convection.
Zone update already out...grids will be available shortly.
15
&&
.PREV DISCUSSION... /issued 711 PM CDT Fri May 19 2017/
AVIATION...
For the ArkLaTex, VFR this evening with a few showers ending
soon. Overnight MVFR with IFR tempo for low cigs at daybreak, but
light BR possible where fair. S winds 5-10KT with cold front
approaching the winds will become SW then NW during afternoon from
W to E with fropa. Aloft, S/SW 20-40KT. Expect shwrs and Tstms
to build early and expand in coverage with heating, especially
along frontal boundary with the push Eastward slow into the overnight.
N/NE winds expected for Sunday with good weather at most terminals.
/24/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 74 83 65 79 / 20 70 70 50
MLU 73 85 67 79 / 10 50 70 60
DEQ 68 79 55 79 / 60 70 20 10
TXK 72 80 60 77 / 40 70 40 20
ELD 72 80 62 77 / 20 70 60 50
TYR 73 82 62 79 / 40 70 50 30
GGG 73 83 63 79 / 30 70 60 40
LFK 73 87 68 82 / 20 70 70 50
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
15