Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/11/17
Area Forecast Discussion
National Weather Service Albany NY
1044 PM EDT Mon Apr 10 2017
.SYNOPSIS...
A southwest flow will allow for temperatures to warm to much above
normal through Tuesday. A cold front will cross the region late
Tuesday into Tuesday night, bringing a chance for showers and
thunderstorms. Drier weather will return for later Wednesday into
Thursday with high pressure building into the region.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 1030 pm, patches of cirrus continue to stream across the
region along the periphery of the upper ridge. Convection was
moving northeastward across lakes Erie and Ontario along the
eastern edge of height falls and reservoir of weak instability.
Some of this activity could scrape far northern
Herkimer/Hamilton counties later tonight, but expect the
majority of the activity to remain north and west of our area.
Temperatures across parts of the snow-covered portion of the
Adirondacks have already plummeted into the 40s, while elsewhere
60s are predominate. Have lowered low temps for the Adirondacks;
otherwise, little changes.
Previous discussion...As of 400 PM EDT...A narrow but strong
upper level ridge extends northeast from the Southeastern US
towards the Canadian Maritimes. At the same time, an upper level
trough over the Midwest is starting to head eastward towards
the Great Lakes. Despite the ridge nearby, sky cover has been
partly to mostly cloudy with some passing high level clouds
throughout the day. Based on upstream satellite imagery, periods
of cirrus clouds should continue into the evening hours.
Some showers and thunderstorms ahead of the surface frontal boundary
have been impacting Michigan and Ontario. Although these should
weaken as these head eastward, some showers may start to approach
upstate New York during the overnight hours. The latest 3km HRRR
suggest that these showers and possible thunderstorms should mainly
avoid our area to the west and north. However, will allow a slight
chance of showers for the far western Adirondacks for late tonight.
Otherwise, it will remain dry over our area.
Temperatures will be very mild for mid April. After a warm day
today, the lingering southerly breeze and passing higher clouds will
prevent temps from dropping too much tonight. Lows will be in the
low to mid 50s for most spots (perhaps a few upper 40s over the
higher elevations).
During the day on Tuesday, the cold frontal boundary to the west
will start to approach. The low to mid level flow will continue to
be out of the southwest. With temps still rather warm aloft (850
hpa temps of 10 to 12 degrees C) ahead of the front, another mild
day is expected once again, as mixing should reach up close to. 850
hpa in most areas. The southwest flow will also aid in downsloping
off the higher elevations as well. High temps look to reach the 70s
to low 80s for most areas.
Clouds will be increase by the afternoon hours as the frontal
boundary starts to reach western New York. Ahead of the boundary,
some showers and thunderstorms will develop and head eastward. These
showers and thunderstorms look to reach our western areas after 3
PM, by the Capital Region around 5 PM and into western New England
by the early evening.
SPC has placed much of the region in a marginal risk for severe
thunderstorms. Although 0-6 km bulk shear values may reach around 40
knots, instability will be very limited, especially due to the fact
that dewpoints values will only be in the upper 40s to mid 50s. In
many times during the pre-greenup stage, mixing is deeper than
models suggest, which would allow for an even drier boundary layer.
Still, a few isolated strong wind gusts are possible within any
thunderstorm, so we will continue to highlight this threat in the
HWO. Precip will be highly variable over the region, as some areas
may see little to none tomorrow and areas that get a thunderstorm
may see a localized dump of a half inch of rainfall.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
The cold front will sweep across our region Tuesday night into
early Wednesday. So scattered showers will linger with a few
thunderstorms possible during the evening hours. There will be
decreasing coverage from northwest to southeast with time. Some
of the showers may linger across southern areas into early
afternoon on Wednesday before clearing takes place.
Lows Tuesday night will be in the 40s to mid 50s with highs on
Wednesday in the upper 40s to upper 60s.
A dry stretch of weather is expected Wednesday night through
Thursday night as a large ridge of high pressure builds east
from the Great Lakes and settles across our region.
Lows Wednesday night are expected to be in the upper 20s to
around 40 with highs on Thursday in the upper 40s to around 60
and lows Thursday night generally in the 30s.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
Models in pretty good agreement on the pattern Friday into next
weekend. Northwesterly upper-level flow will start the period off,
with subsidence reflected in a large area of surface high pressure.
Dry and relatively seasonable weather is expected to continue
through at least Friday night. The pattern turns more zonal for the
weekend ahead of an upper trough tracking through the Northern
Plains and Upper Midwest. Return flow around the high will usher in
a warmer and more moist airmass. Isentropic lift could result in
some showers as early as Saturday, but the more likely timeframe for
showers and perhaps some thunderstorms is Saturday night into Sunday
night as lift is increased ahead of the approaching height falls.
Temperatures are expected to trend warmer than normal over the
weekend.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Patches of high/midlevel cirrus/altostratus expected to be the
only cloud cover into Tuesday morning. On Tuesday, the upper
ridge responsible for good aviation conditions will give way to
an approaching frontal system. With a very dry airmass in place
initially, VFR conditions are expected to continue into the
afternoon hours, although some cumulus around 5 kft could
develop. The front is not expected to pass through until after
the TAF period, but showers and a few thunderstorms may develop
along a prefrontal trough during the afternoon hours. KGFL/KALB
stand the best chance of seeing showers or a thunderstorm, so
have included a PROB30 there. Instability is expected to be
limited, so thunderstorm potential is still rather uncertain.
Winds tonight will be out of the south at around 10 kt or less.
Winds will become south-southwesterly by late Tuesday morning at
around 10 kt with some gusts to 15-20 kt possible.
Outlook...
Tuesday Night: Moderate Operational Impact. Breezy Scattered SHRA...TSRA.
Wednesday: Low Operational Impact. Breezy Isolated SHRA.
Wednesday Night: Low Operational Impact. Breezy NO SIG WX.
Thursday: No Operational Impact. NO SIG WX.
Thursday Night: Low Operational Impact. Slight Chance of SHRA.
Friday: No Operational Impact. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.
&&
.FIRE WEATHER...
A southwest flow will allow for temperatures to warm to much above
normal through Tuesday. A cold front will cross the region late
Tuesday into Tuesday night, bringing a chance for showers and
thunderstorms. Drier weather will return for later Wednesday into
Thursday with high pressure building into the region.
Relative humidity values will increase to 70 to 90 percent
tonight, drop to 35 to 65 percent on Tuesday, recover to 80 to
100 percent Wednesday night and drop to 55 to 75 percent on
Wednesday.
Winds will be south to southwest at 10 to 15 mph, southwest at
5 to 15 mph on Tuesday with a few gusts to 20 mph, west at 5 to
10 mph Tuesday night and west at 10 to 20 mph on Wednesday.
&&
.HYDROLOGY...
A warming trend will occur through Tuesday, with temperatures
well above. Warmer temperatures will result in increased runoff
due to snow melt. River levels will need to be monitored,
especially for basins with significant snow pack such as in the
southern Adirondacks, upper Mohawk, upper Hudson and into
southern Vermont.
Scattered showers and thunderstorms Tuesday through Wednesday
will result in basin average rainfall of a quarter of an inch
or less but point rainfall totals could be up to a half inch.
The following river point has a flood warning in effect:
Riverbank (Schroon River).
For details on specific area rivers and lakes, including observed
and forecast river stages and lake elevations, please visit the
Advanced Hydrologic Prediction Service /AHPS/ graphs on our
website.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.
&&
$$
SYNOPSIS...11/NAS
NEAR TERM...Frugis/NAS/Thompson
SHORT TERM...11
LONG TERM...Thompson
AVIATION...Thompson
FIRE WEATHER...11/NAS
HYDROLOGY...11/NAS
Area Forecast Discussion
National Weather Service Caribou ME
919 PM EDT Mon Apr 10 2017
.SYNOPSIS...
A cold front will push into the north on Tuesday. Weak low
pressure will track along the front Tuesday night.
&&
.NEAR TERM /THROUGH TUESDAY/...
9:19 PM Update...It remains a very mild evening for inland
areas with 9 PM temperatures more than 10 degrees above our
average highs for this time of year. It is much cooler along the
immediate shoreline and across most of the Downeast region
where temperatures are in the 40s. The KCBW 88-D and Canadian
radars show some showers in Quebec moving into far western
Aroostook County. Main update at this time is to the PoP/QPF
grids for late this evening and overnight based on the radar and
near term model trends. The HRRR looks to have a decent handle
on these showers and moves them across far northern sections of
the CWA from 01-06Z.
Previous discussion... Strong high pressure over the Atlantic
southeast of New England is currently dominating the flow across
the region. At the same time a cold front is approaching slowly
from the northwest. The cold front is expected to stall across
western areas Tuesday with showers breaking out around the
front. Some isolated thunder is also possible across the
southwestern portion of the region. Temperature will we cooler
in the north and west Tuesday due to higher cloud coverage.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
Cdfnt stalls out in vicinity of Downeast at the beginning of the pd.
Wave wl ride along bndry drg the ovrngt hrs but questions continue
to cntr arnd the potential for storms in the early evng hrs. Mid-lvl
lapse rates wl range fm 6.5-7 C/km thru 03z with possibility of some
isold elevated convection lingering mainly in far swrn zones. Sfc
low looks to cross coastal waters ovrngt with mostly lkly areas of
showers Downeast thru daybreak as convergence mvs thru the area.
Another wv wl pass thru Wed aftn with showers mvg thru the area.
Latest GFS appears to be suffering fm convective feedback with
heaviest qpf expected to fall along the coast in RRQ of jet streak
being shown by all med range guidance. This wl lkly impact rvr fcsts
for the rmndr of the week along with potential for flooding as ice
flushes out of the system. 48-hr qpf amnts look to range fm 0.25-
0.50 inches through Wed aftn outside of locally higher amnts in
tstms.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Seasonably cool and dry Thursday night through Friday with high
pressure. Low temperatures below freezing many areas Thursday
night and Friday night. High pressure moves east Saturday and
the next weather system moves in Saturday night with a good shot
at precipitation Saturday night and Sunday. At this point,
looks like a moderate strength weather system with rain being
the most likely precipitation type, although can`t rule out a
bit of snow on the tail end Sunday night before ending. Turning
cooler behind the system with below average temperatures early
next week.
Models are in decent agreement for the extended, especially
given the active weather pattern.
&&
.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: Expect VFR conditions this evening and MVFR overnight
at the northern terminals. Predominately MVFR during the day
Tuesday.
SHORT TERM: Expect MVFR/localized IFR across northern terminals
Tue afternoon with VFR at BGR and BHB. Expect IFR restrictions
to continue for northern sites through Thursday. Further south
MVFR/IFR sets in late Tue night, continuing through the day Wed
before improving.
&&
.MARINE...
NEAR TERM: Have used the NAM to initialize sustained winds,
however will reduce model winds speed by 10 percent to account
for cold sea surface temperature stabilizing the boundary
layer. For waves: Currently incoming long period southeasterly
swell 2-3 feet/8 seconds) continues to dominate but
southwesterly wind wave is expected to build this evening and
become the primary wave system as the southeasterly swell
subsides. Will initialize waves with the Nearshore Wave
Prediction System and will adjust waves lower into this evening
until 1800Z NWPS becomes available using latest wind forcing.
Will issue an SCA for tonight.
SHORT TERM: No headlines through the middle of the week. Winds
will be just aob 25kts Thur morning for the outer waters. Seas
will likely remain blo 5ft through the end of the week.
&&
.HYDROLOGY...
Persons with interests along rivers need to remain vigilant and
keep a close eye on waterways through the rest of this week.
Ice movement continues on area rivers today, particularly
across northern Maine. We have had reports of ice moving on the
St John near Grand Isle, and it looks like there`s movement
around Dickey now as well, as per the latest readings at the
USGS gage there. On the Aroostook, the USGS gages at Masardis
and Washburn are also showing signs of ice movement. The ice jam
at the Caribou/Fort Fairfield remains in place but is not
creating any known impacts.
The central and southern rivers, such as the Piscataquis and
Penobscot, will also see increasing ice movement. The ice jam
on the Pleasant River between Brownville and Milo likely has not
changed much, as no impacts have been reported. There has been
some movement on the Piscataquis River, with plenty of ice still
reported above Guilford.
Ice movement and break up will continue over the next 24-48
hours. Today`s sunshine, warm temperatures, and increasing flows
have served to weaken the ice. Temperatures will not drop below
freezing until late Thursday night, so snowmelt will continue
over the next few days. Ice will likely flush out of all rivers
by Wednesday.
Thereafter, the focus turns to the chances for open water
flooding. In addition to the snowmelt, we are anticipating a few
rounds of showers through the end of the week. At this time, max
rainfall amounts will be around half an inch. This rainfall
added to the runoff from snowmelt will cause rivers to rise and
possibly approach flood stage by late in the week.
&&
.CLIMATE...
The high temperature this afternoon at Caribou was 65F. This
was the warmest in nearly 6 months since October 12, 2016. The
high at Bangor of 67F was only one degree shy of the record high
of 68F, set in 1931.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Small Craft Advisory until 8 AM EDT Tuesday for ANZ050>052.
&&
$$
Near Term...CB/Mignone
Short Term...Farrar
Long Term...Farrar
Aviation...CB/Mignone/Farrar
Marine...CB/Mignone/Farrar
Hydrology...Hastings
Climate...CB
Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
954 PM CDT Mon Apr 10 2017
.DISCUSSION...00Z CRP sounding indicated a strong inversion just
below 750 mbs remains in place across South Texas. Convection near
the frontal boundary from northeast through central Texas back to
the southern Trans Pecos region has been slower to organize and
become outflow dominant as earlier high resolution CAMs indicated.
As noted in mesoscale precipitation discussion from WPC, the
experimental HRRR at 17Z earlier today has a better handle on
current activity than any of the other models. To add to the
uncertainty, 00Z HRRR along with the latest Texas Tech WRF keep
most of the convection to the north of the area through 12Z.
Strong storms in northeast Mexico have followed the instability
axis over the higher terrain where convective inhibition is weak.
Some of this activity could possibly move across the Rio Grande
later this evening into the early overnight period. Still possible
that convection along the boundary will become outflow dominant
with activity surging southeastward toward region overnight. But
confidence in this scenario is not high enough to warrant keeping
categorical PoPs across the northern counties. Reduced PoPs
especially for remainder of this evening with a mention of only a
slight chance of showers for the coastal plains. Lowered PoPs
10-20 percent overnight. Adjusted minimum temperatures upward
also.
&&
.PREVIOUS DISCUSSION... /Issued 654 PM CDT Mon Apr 10 2017/
DISCUSSION...See Aviation section for 00Z TAFs.
AVIATION...MVFR ceilings were prevalent over the coastal plains
late this afternoon beneath the cloud deck around 6-7 kft near the
inversion level. Isolated streamer showers were north of KHBV.
MVFR ceilings will cover the area by 02Z with showers possible
late this evening for LRD and VCT areas. Timing of convection
moving out of the Hill Country remains a bit uncertain. 20Z HRRR
and 12Z ARW models show line of convection reaching VCT area by
07Z while the latest Texas Tech WRF and NSSL WRF show later
arrival toward 12Z. Will lean toward the faster arrival time,
bringing storms into VCT/LRD around 08Z, ALI at 09Z and CRP at
10Z. Ceilings will lower to IFR in advance of the storms along
with scattered showers forming. Showed wind gusts potentially up
to 35 knots at VCT/LRD but storms could organize and produce
severe wind gusts along with marginally severe hail. Storms
should be moving out of the area during the morning hours with
conditions improving to VFR Tuesday afternoon.
&&
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 73 78 68 83 68 / 40 60 10 10 10
Victoria 69 78 65 82 65 / 70 60 10 10 10
Laredo 73 82 68 87 67 / 60 60 20 10 10
Alice 72 80 66 86 66 / 50 60 20 10 10
Rockport 73 79 70 80 71 / 40 50 10 10 10
Cotulla 70 79 65 85 66 / 70 60 10 10 10
Kingsville 73 79 67 85 67 / 40 60 20 10 10
Navy Corpus 73 77 70 80 71 / 30 50 20 10 10
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
TMT/89...SHORT TERM
Area Forecast Discussion
National Weather Service State College PA
1205 AM EDT Tue Apr 11 2017
.SYNOPSIS...
High pressure that brought sunshine and warm temperatures
Monday will move off the coast Tuesday. Temperatures will
remain warm but skies will be cloudier as the next weather
system approaches. Scattered showers or maybe a thunderstorm
are possible in the northwest after midnight gradually spreading
east during the day Tuesday. A weak cold front will cross the
region late Tuesday through early Wednesday, bringing cooler
conditions for Wednesday and Thursday.
&&
.NEAR TERM /UNTIL 8 AM TUESDAY MORNING/...
High clouds continue across PA this evening and are helping keep
temperatures a little warmer than initially forecast in the
northern zones. Lower Susq Valley seemed to cool off despite
clouds. Adjusted clouds, temps, and dew points for trends.
Adjusted timing of chance showers into NW zones based looking
at current radar and current HRRR forecast.
&&
.SHORT TERM /8 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
12z model guidance telling the a similar story for Tuesday as
weak cold front advances into northwest PA in the afternoon
and a narrow ribbon of richer deep layer moisture increases
chances for showers and isolated thunderstorms. Thermo profiles
not favorable for severe...and given the narrow plume of PW
associated with this system...expect a rope of scattered showers
with a few isold thunderstorms to result with locally strong but
sub severe gusts. Earlier MRGL outlook for the area has now been
trimmed back with only the northeast still in that category, and
the rest of my area in General thunder.
There is a surge of 12 to 13C air at 850 hPa, and this will
translate into many locations seeing high temps in the mid to
upper 70s, with a few locations likely topping 80F Tuesday
afternoon in southeast PA.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
GEFS and other models show some lingering chance to likely PoPs
before 8 AM Wednesday. Very light showers.
The anemic cold front should be east of our region by early
Wednesday. Surface high pressure is forecast to build in behind
it in all the guidance. Our superblend wants to show some low
end PoPs through about 8 AM.The GEFS and CMCE suggest a nice day
Wednesday. Our PoPs are in slight chance range mainly for
collaboration purposes.
The GEFS implies close to normal temperatures and low chance of
any rainfall from about 8 AM Wednesday until about 8 PM
Thursday. We should have two relatively dry nice days as surface
high pressure should dominate our weather. But the ridge axis
moves to our east Thursday night with a high to our north.
Return flow over the shallow boundary scenario setting up
Thursday night and Friday.
Thus the GEFS and GFS imply increased chance of light
rain/showers overnight Thursday into Friday and southern half or
so of the State on Friday. The GEFS PW field implies a stalled
boundary and the higher PW values are to our south Friday. The
GEFS members have issues of the placement of the boundary some
members generate light QPF.
POPS may lower Saturday but increase a bit again on Sunday and
lowering Monday. The GEFS does show a surge of high PW air
overnight Saturday into Sunday so a bit more confident in
rainfall in that period. PW anomalies at +1 to +2 sigma. The 850
hPa temperatures imply warm moist day Easter.
EFS imply FROPA Sunday into Monday. Slightly cooler Monday if
correct. Also implies a trigger on Sunday!
&&
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
VFR conditions should prevail over the entire region overnight
into tomorrow.
Overnight there could be areas of patchy fog/mist mainly in
isolated valleys and in southeastern areas. So mainly VFR some
patchy MVFR possible.
A front moving in from the west could trigger showers and
isolated thunderstorms in the afternoon and evening. The showers
will begin in the Western TAF sites around 18Z then work east
through the overnight period into Wednesday. The potential for
MVFR in -SHRA and isolated thunderstorms will move eastward with
MDT and LNS possible after 00Z. Some lingering isolated showers
remain possible through the southeast Tuesday night.
High pressure builds in Wednesday returning the region to VFR.
Outlook...
Mon...No sig wx expected.
Tue...Sct showers/iso tstms - mainly NW half. MVFR cigs becoming
likely NW half showers PM in east.
Wed-Fri...No sig wx expected.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Watson
NEAR TERM...Watson/DeVoir
SHORT TERM...DeVoir/Lambert
LONG TERM...Grumm
AVIATION...Ceru
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
723 PM CDT Mon Apr 10 2017
.MESOSCALE UPDATE...
Spent a good amount of time attempting to add some timing precision
to the WX/PoP/QPF grids for the next 18 hours. While some initial CI
has begun in the vicinity of San Antonio, capping continues to hold
on preventing cells from growing upscale without help from a surface
boundary...unlike the convection farther north. In regards to
activity farther north, SPC mesoanalysis and proximity RAP soundings
show the cap eroded along the boundary with surface dewpoints at or
near 70 degrees and 3000+ J/KG to tap into. Convergence along the
front is maximized from north of Kerrville and northeast whereas
farther west, weaker low level flow and less favorable moisture flux
vector orientation to the front has kept the majority of the plateau
from convecting.
CAM guidance continues to ramp up QPF values however some guidance,
especially the HRRR, appears to be overconvecting in the next 2-4
hours. While these values are not being disregarded, the TTU-WRF
model has been generally handling this convection thus far rather
well. It continues to convect more along the favorable convergent
zone along the front, becoming outflow dominant, and thus convecting
farther southeast along the line beginning around 10PM. These new
storms will be able to capitalize on the high instability and PWAT
values of over 1.5" advecting into the I-35 corridor allowing for
hourly rainfall rates of over 2 inches per hour possible. This means
that the QPF forecasts of 2-4 inches with isolated up to 7 inches is
still very much valid for all areas east of the Edwards escarpment as
well as along and east of the I-35 corridor.
Also, with the high instability and appreciable shear, quarter size
hail and damaging winds are also still possible through 11PM.
However, these threats are secondary to the flash flood threat, which
is still the more significant impact for the next 12 hours.
&&
.PREV DISCUSSION... /ISSUED 622 PM CDT Mon Apr 10 2017/
AVIATION DISCUSSION...FOR 00Z TAF PERIOD...
Expecting TSRA development northwest of the KAUS terminal in the
first 6 hours of the TAF period. Some isolated development has
already been observed in the vicinity but have been short lived with
sporadic ltng. Included TEMPO for possible iso storms for first 3
hours and then prevailing afterwards. Latest models have a line of
TSRA to begin impacting around 03Z and an hour or so later for
KSAT/KSSF. Hvy rain will be the primary impact to the terminals in
addition to lightning thus reduced VIS as a result. CIGs will be
difficult but should fluctuate around low end MVFR and IFR during
storm impact.
Activity is expected to be clear of all terminals by 10-12Z. However
cloud cover is expected to prevail through much of the morning hours.
Only marginal improvement to CIGs is expected by the afternoon hours
tomorrow.
PREV DISCUSSION... /ISSUED 332 PM CDT Mon Apr 10 2017/
SHORT TERM (Tonight through Tuesday Night)...
.Dangerous Flash Flooding Event Possible Late This Afternoon
through Tonight across South Central Texas...
Complex weather scenario taking shape late this afternoon through
tonight. The cold front was located just south of a Stephenville to
San Angelo line at 3 PM with showers and storms developing along and
just behind it in West Central Texas. Additional isolated to
scattered showers have developed through the afternoon beneath a
mid level cap across Central Texas. Aircraft sounding data from AUS
indicates the mid level cap still in place, but this is forecast to
erode late this afternoon and evening as the front approaches the
region. Initially discrete storms could pose a hail threat across the
northern Hill Country and Central Texas through the early evening.
Signals in hi resolution models then transition into an organized
complex of storms, but there are some difference in timing on how
fast this happens. Should this happen this could support a threat of
damaging straight line winds through the CWA.
However, the main concern we are messaging will be the heavy rainfall
potential that could lead to flash flooding. Precipitable water
values of 1.6-1.8 inches are pooling over the region south of the
front. This is nearly 2 standard deviations above average. Initial
slow motions of the storms and complex will yield pockets of intense
rainfall rates this evening through portions of the overnight, as
indicated by runs of the HRRR. Models the past three runs have
trended farther south and with higher QPF amounts into much of the
southern and eastern Hill Country as well as I-35 corridor. GEFS
plumes for both Austin and San Antonio have trended up, with the
lowest member at Austin around 2", highest at 4.3", and mean 2.87".
Some of the high resolution guidance suggests the highest amounts
farther south toward the San Antonio metro area. It is difficult at
this time frame to determine where the heavier pockets may occur as
there is uncertainty with the mesoscale evolution of the system.
But generally 2-4" is expected across the Flash Flood Watch area
with isolated amounts up to 7".
It is important to stress the flash flooding potential with this
system, especially since this will be occurring at night when it is
harder to recognize the dangers of flash flooding.
Tomorrow`s chances for rainfall will depend entirely on how
organized the system evolves tonight. With hi resolution guidance
trended towards and MCS, the atmosphere may become worked over and
stabilized for Tuesday.
LONG TERM (Wednesday through Monday)...
Chances for showers and thunderstorms will remain in the forecast
through the rest of the week with slightly greater chances Thursday
as a trough shifts through the region. No concentrated signals appear
to warrant hazard mention at this time during the long-term period.
Diurnal showers and thunderstorms look to be likely each afternoon
through the week as a unsettled and active southern jetstream branch
helps promote lift with the continued moist airmass in place.
Thursday and Friday appears to be a slightly better concentrated day
with the passage of stronger trough axis. Weak ridging over the
weekend may help to keep the area dry.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 65 76 63 79 64 / 100 40 10 20 10
Austin Bergstrom Intl Airport 65 76 62 79 63 / 100 50 10 20 10
New Braunfels Muni Airport 66 77 63 79 64 / 100 60 10 20 10
Burnet Muni Airport 62 74 61 76 63 / 90 40 10 20 10
Del Rio Intl Airport 67 79 65 80 64 / 50 40 20 20 30
Georgetown Muni Airport 63 75 62 78 63 / 100 40 10 20 10
Hondo Muni Airport 68 79 63 81 64 / 100 50 10 20 10
San Marcos Muni Airport 66 76 63 79 64 / 100 60 10 20 10
La Grange - Fayette Regional 67 77 64 80 63 / 100 60 10 20 10
San Antonio Intl Airport 67 78 64 80 65 / 100 60 10 20 10
Stinson Muni Airport 69 78 65 80 65 / 100 60 10 20 10
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Tuesday morning for the following
counties: Atascosa...Bandera...Bastrop...Bexar...Blanco...Burnet...
Caldwell...Comal...Fayette...Frio...Gillespie...Gonzales...
Guadalupe...Hays...Kendall...Kerr...Lee...Llano...Medina...Real...
Travis...Uvalde...Williamson...Wilson...Zavala.
&&
$$
Mesoscale/Aviation...TB3
Synoptic/Grids...TB3
Public Service/Data Collection...33
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1022 PM CDT Mon Apr 10 2017
.UPDATE...
A challenging forecast continues to unfold for Southeast Texas
this evening with surface analysis showing a nearly stationary
cold front draped north and west of the region (roughly along a
Dryden- Lampasas- Mount Pleasant line). Regional radar mosaic
shows thunderstorms continuing to develop and intensify along this
line, possibly aided by upper level lift from a disturbance
lifting into West Texas from New Mexico. With these aforementioned
features remaining well removed from the region and aircraft
soundings out of Houston showing a persistent capping inversion
around 700 mb, shower and thunderstorm activity near the region
diminished with loss of heating earlier this evening and has
remained minimal. Have lowered rain chances and rain totals
through the remainder of the evening as a result. Other changes to
the forecast include updating temperatures and dew points based on
hourly trends with overnight lows in the 60s to near 70 under
mostly cloudy skies.
Convective evolution for the overnight period and through most of
the day Tuesday still contains considerable uncertainty. High
resolution guidance has been indicating that the disturbance over
West Texas may provide enough lift to allow thunderstorms along
the front to grow upscale and generate a strong enough cold pool
to allow this complex to propagate away from the front and into
Central or Southeast Texas tonight and into tomorrow morning.
However, this guidance continues to struggle with placement and
timing of this feature... likely owing to the presence of the
strong cap in place across Southeast Texas. Were this system to
develop, anticipate it to lose much of its intensity during the
early morning hours as it approaches the Interstate 10 corridor
as a result of the cap in place.
The frontal boundary north of the region is not expected to make
much southward progress overnight, but maintaining the Flash Flood
Watch in place across the northern two tiers of counties given the
potential for activity along the stalled frontal boundary to move
off of the boundary. Environmental conditions still remain very
favorable for a flash flood threat to materialize across these
areas (SPC Mesoanalysis showing precipitable water values across
the Flash Flood Watch area 1.5-1.7 inches), but the focusing
mechanism for thunderstorms capable of heavy rain development is
still uncertain at this time with the front still north of the
region and any potential thunderstorm complexes having not yet
developed.
With the disturbance over West Texas reaching East Texas sometime
during the day tomorrow (possibly as late as tomorrow afternoon),
the stalled frontal boundary should receive enough of a push to
move into the region. This would result in another round of shower
and thunderstorm development (especially if the front were able to
move through late enough in the day to take advantage of any
destabilization from diurnal heating) but timing for this
potential round remains uncertain at best... sometime Tuesday
morning or later, depending on the speed of the disturbance.
Huffman
&&
.PREV DISCUSSION... /ISSUED 612 PM CDT Mon Apr 10 2017/
AVIATION...
Confidence remains low with regard to convective potential
tonight. Will maintain the tempo for thunder at both KCLL and KUTS
but confidence wanes quickly for TAF sites south of these
airports. Prefer to take a cautious approach and just mention
VCSH/VCTS after 09z for the Houston terminals southward. The
latest HRRR and RAP want to take the precip west of the region and
fcst soundings show the best potential for precip to be early
Tuesday morning between 10-16z. AMDAR soundings currently show a
very stout cap in place over Houston. Fcst soundings keeps skies
generally cloudy with MVFR cigs. Think there will be enough mixing
to of dry air above 800 mb to create VFR conds by late aftn. 43
PREV DISCUSSION... /ISSUED 340 PM CDT Mon Apr 10 2017/
DISCUSSION...
Obs at 20Z show cold front now from San Angelo to the DFW
Metroplex. Convection is forming along the front but not very
strong. A strong/severe storm has formed over Milam County in
central Texas so we getting some indication that the capping
inversion from the elevated mixed layer may be eroding. AMDAR and
CRP/DRT/LCH soundings this morning all had a strong cap around
850-700mb. AMDAR soundings do show that capping inversion still in
place but weaker north of Houston. Weak ascent from ageostrophic
circulation with the cold front may indeed be enough to locally
weaken the cap allowing for surface based storms in the warm
sector. Aloft water vapor imagery really does not show much in the
way of a jet streak for shortwave for lift so overall neutral
vorticity advection. There is a shortwave back over Arizona which
could impact the area Tuesday morning.
Severe Threat Tonight...With at least some heating, cap slowly
eroding, dewpoints in the low 70s and the front pushing south,
there is a window for severe weather this evening and tonight
mainly north of a Wharton/Cleveland line. The main threat will be
more closer to Brenham/Livingston northward, but should the line
of storms evolve like the HRRR suggests with its many recent runs,
a line of storms could push south. With capping stronger to the
south, the line of storms would likely decrease in intensity but
still pose a threat for hail/wind. Instability at least for the
next 4-6 hours with day time heating will support CAPE of
2000-3000 J/kg over much of the threat area. Lapse rates are steep
on area soundings so large hail will be a threat. Deep layer shear
should be strong enough to support rotating cells like the one in
Milam County which will help with hail threat. Look for any
supercell to eventually gust out and possibly form into a line or
bowing segment. Basic timing for the storms will be mainly from
now through midnight. After midnight HRRR keeps most of the
convection over central Texas with a line of storms driving south.
Heavy rainfall threat...main threat for heavy rainfall and flash
flooding exists again over the same area for severe weather. This
area is mainly from Brenham to Livingston. Storm motions will be
around 20 knots so storms with rain rates of 1-2 inches an hour
could produce locally heavy rainfall. If rain rates are higher,
flood threat will only increase. There should be plenty of
moisture with 1.6-1.8 inches of precipitable water. Of particular
interest is the increase winds on KHGX VAD wind profile at
1000-4000FT AGL with now 35 knots at 2000-3000FT. This will
certainly help with heavy rainfall threat if this LLJ can be
maintained through the night and provide inflow to storms moving
along the cold front. Since the environment supports the potential
for flash flooding, a flash flood watch has been issued for the
northern 1/3 of counties in SE Texas and matches up with the watch
for central Texas. Rainfall amounts in the watch area will likely
be 2-3 inches but a few HRRR runs shows isolated amounts of 4-6
inches. Given the environment this may be the upper end of
rainfall amounts but enough for a flood threat.
Tuesday is a challenging forecast since it largely depends on what
happens tonight. There is a shortwave trough coming across Texas
from Arizona. Seems to reason that there will be another round of
storms for the area so will keep some rain chances going for the
forecast. But the mesoscale could really mess up the forecast.
Overnight convection with a squall line could very well stabilize
the boundary layer for much of the day Tuesday and lead to a rain
cool but dry day with no rain. For now rather count on the
shortwave trough acting as a trigger for more convection assuming
there may be enough recovery of moisture/instability from previous
convection.
Overpeck
MARINE...
A moderate/strong onshore flow will persist across the marine areas
the rest of the this afternoon into this evening. We should see the
gradient relax overnight as a cold front approaches from the north.
This boundary is expected to stall just north of SE TX, but a large
area of storms developing along this system could track south
into SE TX. However, not expecting these storms to reach the
coastal waters at this time. This front should wash out/move back
to the north by Wed. Generally moderate onshore winds will
persist the remainder of the week. 41
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 65 76 63 82 64 / 70 60 20 20 10
Houston (IAH) 67 77 64 82 65 / 40 50 20 20 10
Galveston (GLS) 72 76 70 79 70 / 20 30 20 10 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flash Flood Watch until 7 AM CDT Tuesday for the following
zones: Brazos...Burleson...Grimes...Houston...Madison...
Trinity...Walker...Washington.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 1 AM CDT Tuesday for
the following zones: Galveston Bay...Matagorda Bay.
SMALL CRAFT SHOULD EXERCISE CAUTION until 5 AM CDT Tuesday for
the following zones: Coastal waters from Freeport to the
Matagorda Ship Channel out 20 NM...Coastal waters from High
Island to Freeport out 20 NM.
Small Craft Advisory until 5 AM CDT Tuesday for the following
zones: Waters from Freeport to the Matagorda Ship Channel
from 20 to 60 NM...Waters from High Island to Freeport from
20 to 60 NM.
&&
$$
Discussion...14
Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
928 PM CDT Mon Apr 10 2017
.UPDATE...
Showers and thunderstorms were slowly moving into the Midsouth
from central and and southern AR. 00Z NAM Bufr soundings and HRRR
guidance suggest this convective activity will continue to
gradually decrease in intensity and coverage through sunrise.
Depending on coverage overnight, the stabilizing effect of
overnight showers may impact coverage during the daylight morning
hours on Tuesday.
Forecast was recently updated with minor downward adjustments in
pops and thunder chances.
PWB
&&
.PREV DISCUSSION... /issued 709 PM CDT Mon Apr 10 2017/
UPDATE...
Updated to include 00Z aviation discussion below.
PREV DISCUSSION... /issued 318 PM CDT Mon Apr 10 2017/
DISCUSSION...
Gusty south winds continue across the Mid-South this afternoon,
with most areas experiencing wind speeds of 10-20 mph. Some areas
have gusted to 30 mph, but winds will continue a gradual downward
trend into the evening hours as a cold front moves slowly south
and east into the region. At 3 PM, this front was analyzed from
near St. Louis, to Ft. Leonardwood, to Harrison (AR).
Convection has been slow to develop along this front but
mesoanalysis indicates a corridor of MLCAPE of 500-1500 J/kg that
extends into northeast AR. This instability is collocated with
effective layer shear of 35-45 kts, which is sufficient to
support organized updrafts. We anticipate further development of
showers and thunderstorms across north central AR and south
central MO over the next few hours that will eventually move into
the CWA during the evening hours. A few strong (to marginally
severe) storms are possible this evening, but most convection
should be rather well behaved. Rain chances will favor the
northwest half of the CWA through 12z given the proximity to the
cold front.
This cold front will continue to move slowly south and east on
Tuesday. Showers and thunderstorms are expected to develop by
late morning along the I-40 corridor, spreading southeast into
northeast MS during the afternoon and evening hours. As the front
moves south of the area Tuesday night, rain chances will be
confined to portions of north MS with dry conditions elsewhere
late Tuesday night and Wednesday beneath shortwave ridging aloft.
The next shortwave trough is progged to approach the area on
Thursday, providing low rain chances to the Mid-South. QPF remains
muted given the lack of strong dynamics and forcing mechanism,
with warm advection being the primary trigger. These low rain
chances will continue across all or part of the CWA through
Friday. Dry conditions are anticipated on Saturday but zonal flow
aloft will open the door for additional rain chances during the
latter part of the weekend. A strong shortwave trough is progged
to move east across the northern Great Lakes over the weekend and
this may be enough to push another weak cold front into the Mid-
South on Sunday.
Temperatures will be at or above normal for much of the next week.
Likely showers and thunderstorms, combined with the weak cold
front will keep temperatures in the upper 60s to mid 70s tomorrow
afternoon, but highs will generally range from the mid 70s to
lower 80s throughout the week. Overnight lows will typically run
in the mid 50s to lower 60s.
Johnson
&&
.AVIATION...
/00Z TAFs/
VFR conditions will begin the period, with MVFR conds and possible
IFR developing late this evening. A cold front will slowly move
through the region during the period with scattered showers and
thunderstorms possible at all sites.
The highest confidence for thunderstorms on site will be at JBR
and MEM in the short term. After 11/06Z, mainly showers are
expected as instability wanes. Convective redevelopment is
expected near all sites tomorrow afternoon, predominately around
11/18Z. All rain should exit the region after this TAF set.
AC3
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
828 PM EDT Mon Apr 10 2017
.SHORT TERM...(This evening through Tuesday)
Issued at 407 PM EDT MON APR 10 2017
Water vapor imagery and RAP analysis show continued split flow
across N America. In the northern stream, a mid level low as over
northern Hudson Bay with a shortwave trof swinging across James Bay
and adjacent northern Ontario. In the southern stream, a vigorous
shortwave was along the Nebraska/IA border. Downstream of this
feature, a convectively enhanced shortwave that moved from northern
WI into eastern Upper MI earlier today spread shra across the e half
of the fcst area. To the w, lingering band of mid level fgen has
been supporting a band of pcpn from nw WI into western Upper MI.
With cold front associated with the northern stream shortwave now
well down into southern WI and central Lower MI, incoming colder air
mass has deepened enough so that pcpn with the fgen band over
western Upper MI is mostly snow. Webcams suggest snow accumulations
on grassy surfaces may be approaching 1 inch. Models indicate the
fgen will rapidly weaken this evening, so not expecting this band of
snow to pose an issue with headlines as the snow should
diminish/fall apart into the early evening. Will be something to
monitor over the next few hrs. If the diminishing trend does not
materialize, could see a few inches of snow in a narrow band over
the w.
Otherwise, challenging fcst shaping up in the short term as the
vigorous shortwave along the Nebraska/IA border moves into the
western Great Lakes tonight and then to the ne of Lake Huron by late
Tue aftn. Models show vigorous deep layer forcing shifting from
southern MN into Upper MI tonight and then departing by Tue aftn.
Overall, there has been a se trend in all model guidance, shifting
heavier pcpn from western Upper MI in older guidance to central and
eastern Upper MI in today`s 12z guidance. With expectation of the
western fgen band of snow diminishing this evening, there may not be
much in the way of pcpn until overnight into early Tue morning when
the stronger forcing associated with shortwave arrives. While fcst
soundings suggest mixed ptypes will be an issue, believe that the
deep forcing/upward motion will likely lead to pcpn becoming just
snow with the main pcpn area. Thus, not anticipating much issue with
fzra. Some models are showing in excess of 0.5 inches of qpf
overnight/Tue morning. With water vapor imagery indicating a feed of
moisture trying to lift into the Upper Lakes ahead of the
disturbance, there is some concern that the the higher fcst qpf
could indeed occur, resulting in locally hvy snow. Will need to wait
to see how pcpn development occurs upstream this evening to
determine just how significant the pcpn may become. For now, fcst
will take a somewhat conservative route with qpf, tracking heaviest
pcpn from south central into eastern Upper MI overnight/Tue morning.
With wet snow/low snow to water ratios, will plan for 2-4 inches of
snow centered roughly on an axis from Iron Mountain to Gwinn. With
heaviest snowfall rates late tonight/Tue morning, will hoist winter
wx advy for Iron/Dickinson/Marquette/Alger/Delta counties. Expect
little or no snow over the Keweenaw. Pcpn will diminish w to e on
Tue, with the heavier snow out of the area by late morning.
.LONG TERM...(Tuesday night through Monday)
Issued at 348 PM EDT MON APR 10 2017
Spent time doing tech improvements and follow-up from overnight
storms today as blended initialization handled the low impact weather
in the long term quite well. Generally expecting some rain showers
late Wed into Thu then possibly more rain showers over the weekend
into early next week, possibly mixing with snow at times Sun into
Mon.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 756 PM EDT MON APR 10 2017
Much drier air which moved across Lake Superior has led to
conditions improving to VFR at KCMX and KIWD this evening. More
pcpn developing ne into Upper MI should stay s of KCMX thru the
remainder of fcst period, allowing VFR conditions to prevail. At
KIWD, band of incoming -sn will likely result in MVFR conditions
late tonight into Tue morning with -sn ending late tonight. At
KSAW, some influx of drier air will allow improvement to MVFR
this evening into early overnight. There may be a little very -sn
or -fzra at times. Approaching disturbance will bring steadier
snow to KSAW late tonight with conditions falling to IFR. Could
be some -fzra as well. While the snow will diminish Tue morning,
IFR cigs may persist into early aftn before improvement to MVFR.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 407 PM EDT MON APR 10 2017
As low pressure tracks ene along a cold front across Lower MI
tonight and Tue morning, n to ne winds up to 30 knots will continue
on Lake Superior. Some gale force gusts are expected over the e half
where the pres gradient btwn an approaching high pres ridge and the
low pres will be tightest. Winds will then diminish from w to e,
falling to mostly under 15kt, as the high pres ridge arrives over
Lake Superior Tue aftn and night. These lighter winds will continue
on Wed despite the high pres ridge shifting e of the area. Although
a low pressure trof is expected to move across the western Great
Lakes Wed night or Thu morning, it will be weak, and winds should
remain light, mostly under 15kts. On Fri, a cold front moving across
the northern Plains will bring increasing e to se winds, possibly up
to 20-30kt. The cold front will then cross Lake Superior on Sat.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory from 2 AM to 11 AM EDT Tuesday for
MIZ005-006-013.
Winter Weather Advisory from 10 PM this evening to 10 AM CDT
Tuesday for MIZ010>012.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...Titus
AVIATION...Voss
MARINE...Rolfson
Area Forecast Discussion
National Weather Service Nashville TN
827 PM CDT Mon Apr 10 2017
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Latest radar and satellite imagery show a few showers and
thunderstorms along and west of the Mississippi River from eastern
Arkansas to southern Illinois. HRRR model brings this activity
into western zones after midnight but greatly weakens it as it
runs into much drier air. Inherited pops may be too high based on
latest HRRR runs but will leave as is for now, with highest pops
late tonight over northwest zones. Made other tweaks to temps and
sky cover but rest of forecast is generally on track.
&&
.AVIATION...
18Z TAF DISCUSSION.
VFR. Cigs should remain VFR for the remainder of the day and
overnight before rain chances move in tomorrow. Winds will stay up
out of the south around 10-15 knots, with gusts to 20-25 knots
through the afternoon. By the early evening winds should be around
10 knots or less at all terminals. Models have backed off on wind
shear during the evening and overnight hours, but would not be
surprised to see some stronger winds just off the surface and
below 2kft. For now, left out mention of wind shear in the
forecast. Models also bring in MVFR and even IFR cigs tomorrow
morning at KCKV as the precip chances increase, so added MVFR cigs
at KCKV after 13Z. Better precip chances move in during the early
afternoon.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......Shamburger
AVIATION........11