Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/18/17
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
847 PM CDT Mon Apr 17 2017
.UPDATE...
Issued at 844 PM CDT Mon Apr 17 2017
Thunderstorms have taken off now that energy is starting to lift
out across the high plains this evening. With freezing levels
being quite low will likely see a few hailers overnight, but
severe chances still look relatively low. Showers/storms will
migrate east with the llj overnight before mostly moving out by
early morning Tuesday.
&&
.SHORT TERM...(This Evening through Tuesday)
Issued at 251 PM CDT Mon Apr 17 2017
The forecast challenges are how much areal coverage of thunderstorms
will there be and how strong could they become tonight?
Currently, under an increasingly cloudy sky, temperatures are
warming through the 40s and 50s on generally east-southeast winds of
5 to 15 mph. Surface high pressure is exiting stage "east" this
afternoon and return flow breezy/windy southeasterly boundary layer
winds are starting to pick up some gust character as well. The
latest 850hpa dewpoint analysis shows +1C to +5C moisture advecting
northward on these stronger winds over western NE and western SoDak.
Fast forward to later this evening: Latest Rap Refresh model
guidance shows strong low level moisture advection in the low level
jet overnight, while strong mid/upper level jet streak winds
overspread the region. A strong mid level shortwave of low pressure
(still digging over the northern Rockies) will move across the
northern plains tonight. The latest Rap Refresh suggests lee-side
troffing will consolidate into a surface low between Rapid City and
Philip this evening before it moves northeast to near Aberdeen by
09Z Tuesday and Wheaton MN by 12Z Tuesday. Between the lift
associated with this low and the interaction of low level and upper
level jets and available low level moisture (for April), model progs
of instability and shear appear to be enough to support thunderstorm
activity tonight. Not much in the way of precipitation is expected
over this cwa prior to 00Z (7 PM CDT), but the 12Z/18Z suite of CAM
solutions today are now all generating thunderstorms that appear to
be routed in the boundary layer over UNR`s cwa (between 21Z and 03Z)
which they then lift northeastward into this cwa (becoming elevated)
mainly at or after 02Z (9 PM CDT) on the nose of the best low level
jet forcing and 850hpa moisture advection. In fact, several
solutions also hint at a separate secondary cluster of thunderstorms
developing in/north of the surface low further north and west near
the border of the Dakotas and Montana closer to the core of the
upper circulation/dynamic lift later after 04Z and sweep those
storms east-northeast through north central South Dakota before
lifting up into North Dakota. If convection does indeed develop, it
will need to be monitored mainly for potentially large hail later
this evening mainly west of a line from Mound City to Miller. East
of that line, sub-severe small hail could occur in the strongest of
any ongoing convective activity later in the night, along with brief
heavy downpours. Precipitation from this potential convective
activity should be clearing the far eastern forecast zones early
Tuesday morning. Presently, still looks like guidance is generating
between a quarter inch and a little over a half inch of
precipitation with this precip scenario. Breezy north-northwest
winds will be in play Tuesday morning mainly over northeast South
Dakota in the wake of this low pressure system until the pressure
gradient between the departing low and an approaching area of high
pressure relaxes. Tuesday should be a dry day, with high
temperatures running generally near to perhaps a degree or two above
normal.
.LONG TERM...(Tuesday Night through Monday)
Issued at 251 PM CDT Mon Apr 17 2017
West to southwesterly flow continues at 500mb at the start of the
period as the low off the Pacific Coast continues to eject waves
around and into the central U.S. The sfc low will be over the Upper
Great Lakes, with a sfc ridge extending from central Canada down
through the eastern Dakotas. This ridge will shift into MN by
Wednesday morning while the next sfc low moves along the western
NE/KS. While the main boundary with all the warm air and better
chance of convection stays in NE/KS, expect more of a steady rain to
move across our area. A widespread 0.25 to over 0.5 inches is
anticipated, although the location of highest potential will likely
shift as the time nears and forecast solutions become a little more
consistent. The initial 500mb wave differs in intensity/timing. A
secondary wave and sfc low across eastern MT late Wednesday
afternoon will likely be associated with some precipitation. There
is a small potential of for light precipitation extending from ND
across our northern counties at through the day Thursday and into
Thursday evening as a ridge builds in at 500mb. In our southern
counties, high pressure will be the rule, as a sfc high crosses NE
and extends a ridge up trough our area. The 500mb ridge will shift
to our east Friday, as the remnants of the Pacific low move into the
western half of the nation and organizes into a progressive low
across KS Friday night. A little more uncertainly comes into play
for the end of the week and into the weekend. We look to be in
between organizing sfc low pressure near OK and large high pressure
across much of western and central Canada on Saturday. The 500mb low
should eject northeast across the mid MS valley Saturday night, with
a more amplified ridge building across the Northern Plains. Yet
another system, this time in the form of an elongated sfc trough
looks to stretch from southern Saskatchewan through the western
Dakotas and western OK late Sunday night. With a more amplified
northern stream, will need to wait and see how much moisture is
available to get widespread showers across our area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 620 PM CDT Mon Apr 17 2017
VFR conditions are expected for much of the taf period, except for
perhaps at KABR and KATY late tnt when some mvfr cigs may form.
Showers and thunderstorms will march across the state overnight,
brief ifr conditions can be expected with any storms. The wind
will be gusty out of the southeast through much of the night.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...TDK
SHORT TERM...Dorn
LONG TERM...KF
AVIATION...TDK
Area Forecast Discussion
National Weather Service Bismarck ND
942 PM CDT Mon Apr 17 2017
.UPDATE...
Issued at 928 PM CDT Mon Apr 17 2017
Little change with this update other than to blend to observed
trends and the 00 and 01 UTC hi-resolution rapidly updating
iterations. As of 0230 UTC, a dry slot was clearly evident ahead
of the potent shortwave that was located on the North Dakota and
Montana border. Strong moisture transport and low level warm air
advection ahead this potent shortwave into southwest and south
central North Dakota will continue through 08-09 UTC with
significant frontogenesis in the 925-700mb layer along the I-94
corridor. Thus, rainfall amounts in excess of 1 inch are possible,
especially across the James River Valley. Will also have to
monitor convection across the southwest and south central as the
HRRR through the evening has suggested the potential for isolated
organized storms within its updraft helicity forecasts in a high
shear/low CAPE/strongly forced environment.
UPDATE Issued at 537 PM CDT Mon Apr 17 2017
Given the presence of low level dry air, characterized by 20 to
30 degree temperature-dewpoint spreads, lowered PoPs through 03
UTC with the initial shortwave. Thereafter, greater forcing and
moisture arrives post 03 UTC as the surface low strengthens
across central North Dakota. Maintained the mention of
thunderstorms southwest and south central tonight highlighted by
SREF thunderstorm probabilities in the 20-45 percent range
associated with a strengthening low level jet and weak
instability.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 222 PM CDT Mon Apr 17 2017
This period will encompass a shortwave h500 trough and deepening
surface low forecast to track across the North and South Dakota
borders tonight. This low will bring widespread showers and
isolated thunderstorms to much of the region with some wet snow
mixing in late tonight north.
The fairly short wavelength of this h500 wave will bring some
sharp thermal profiles and a strong response in the h850 winds.
The North American Ensemble Forecast System (NAEFS) has a
V component of the wind near a climatological maximum tonight.
Supporting this model earlier runs of the NAM depicted 75kts of
h850 wind across NE South Dakota tonight. While the latest 12Z run
not quite as robust it still is quite strong. Although this wind
will not mix to the surface since it moves through around midnight
it will act to pull available moisture into the region. The NAEFS
precipitable water profile is also impressive near 90 percent of
the climatological max. So there should be plenty of moisture for
a decent precipitation event. With the ground now fairly dry the
soils should soak up the moisture.
Storm total rainfall is forecast between a quarter and three
quarters of an inch from southwest through northeast North Dakota
by Tuesday morning. A narrow band of CAPE supported by strong
0-6 km wind shear will support isolated to scattered thunderstorms
along a triple point in the frontal system as it moves across the
southern third of the region tonight.
.LONG TERM...(Tuesday night through Monday)
Issued at 222 PM CDT Mon Apr 17 2017
The extended period will see several h500 troughs move through but
in fairly weak mid level flow. The best chance for rain will be
Wednesday followed by generally below normal precipitation
chances. Highs will be in the 50s Wednesday and mostly in the 60s
Thursday through the weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 928 PM CDT Mon Apr 17 2017
Widespread rain showers with embedded thunderstorms will continue
to develop across southwest and south central North Dakota
tonight. IFR conditions are possible as ceilings lower through the
night. While rain showers will be less prevalent across northern
North Dakota, IFR ceilings will also develop through the night.
Some snow may mix with rain late tonight north.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...AYD
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...AYD
Area Forecast Discussion
National Weather Service Denver/Boulder CO
927 PM MDT Mon Apr 17 2017
.UPDATE...
Issued at 925 PM MDT Mon Apr 17 2017
There was a bit of weak convection over Washington County early
this evening, but it died out. There has been no convection for
last two hours anywhere in the CWA. The new satellite mid level water
vapor pictures marginally show a weak upper trough pushing
eastward out the CWA right now. The flow aloft right now is due
northwesterly. The easterly 3/5ths of the plains are holding on to
lower 50s F dew points right now, but to the west the dew points
are in the 20s F. There is nothing upstream as far as convection
goes. Will get ride of any pops this update.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 131 PM MDT Mon Apr 17 2017
Upper low over northern rockies with tail end of upper trof will
move across Colorado tonight. There is some weak qg ascent with
this system but still a batch of high clouds which are moving
across the plains this afternoon and may be cutting down the
heating a bit. Main concern still centers on thunderstorms
developing over the plains later this afternoon and evening with
the potential for an isolated severe storm. Surface dewpoints
maintaining in the mid 40s to lower 50s over the far plains ahead
of the dry line. With temperatures in the low/mid 70s expect
surface based CAPES in the 1000-2000j/kg. Sufficient shear for a
few severe storms with mainly large hail and damaging winds.
Despite lingering low level inversions feel large scale lift and
additional heating will allow a few storms to develop. Latest HRRR
showing strongest storm mov ing across Washington county later
this afternoon/evening.
For later tonight and Tuesday, some drier air will move in behind
tonight`s trof but still could be some patchy fog and low clouds
over far eastern Colorado. Drier on Tuesday but could see a few
showers developing in the mountains late in the day in advance of
next trof.
.LONG TERM...(Tuesday night through Monday)
Issued at 131 PM MDT Mon Apr 17 2017
Flow aloft will be southwesterly Tuesday evening with the jet
moving from the SW to NE over portions of western CO. At the
surface, a low centered east of I-25 will help to bring increased
SW winds over the southern plains. This will help to increase fire
danger into the evening hours for areas on the plains south of
I-70. By midnight on Tuesday the surface low will move east over
the plains with a cold front dropping south bringing flow on the
plains more northerly by early Wednesday morning. A trough
embedded in the SW flow will increase moisture in the high
country and bring a chance of rain and snow to the mountains
through Wednesday. Colder air will move in by the late morning
dropping the freezing level to 8500 ft. A lee side surface low
will build on the plains increasing downsloping off the
foothills. The upper jet will set itself up over Central CO
increasing westerly winds into the mountains with gusts to 55 mph
possible at mountain top by the afternoon. This will help to
increasing downsloping and keep conditions over the lower
foothills out to Denver Metro dry. Further east wrap around
moisture will bring a slight chance of rain to the far eastern
plains by the afternoon. Winds will also increase on the plains
behind the frontal push with sustained winds of 15 to 20 mph with
gusts to 30 mph. By Wednesday evening increased subsidence from
the west and high pressure building on the plains will help to end
any showers over the east. Temperatures for Wednesday will be in
the lower 70s.
By Thursday upper ridging between systems will build in clearing
out any precipitation. The cold push from the North will have
settled in bringing temperatures down into the mid 60s. The next
system to affect CO will be over the West Coast Thursday afternoon
with models bringing it into CO by Thursday night. At this time
both the EC and GFS keep the system as an open wave as it makes
its way over the state. Upon exiting into KS is when the GFS cuts
it off. At the surface, a building surface low to the SW will help
to keep SE flow over the plains and into the base of the
foothills Thursday evening. This will help to create orographic
convection over the foothills Thursday afternoon. Precipitation
will become widespread through Friday as the trough pushes
through the state. Continue with likely pops for both Thursday
and Friday with some changes still possible as models refine the
path of the system. Temperatures for Thursday and Friday will
continue to decrease with 60s on Thursday and 50s by Friday. Do
not believe that freezing levels on the plains will get low enough
for snow, however decent rain will be possible with snow still
expected for the higher foothills and mountains.
Precipitation will slowly come to an end Saturday with cooler NNW
flow aloft. Upper ridging will increase by Saturday night with
mild conditions expected for Sunday.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 925 PM MDT Mon Apr 17 2017
The DIA LLWAS winds on the IDS4 are showing weak drainage winds in
place at many of the sensors. Some have weak westerly winds.
The numerous models show weak wind speeds all night at DIA but
few of them show south-southwesterlies. There is not much of a low
level pressure gradient in place overnight so it seems normal
drainage pattern winds should be the rule. I will go that route.
&&
.FIRE WEATHER...
Issued at 131 PM MDT Mon Apr 17 2017
Some elevated fire weather concerns for Tuesday afternoon with
some southwest wind gusts in the 10-20 mph for a brief time
Tuesday afternoon over the Palmer Divide region. Humidities will
drop to around 15 percent. Overall conditions for red flag are
marginal and there is some green up underway so will not issue any
fire hilites.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...RJK
SHORT TERM...Entrekin
LONG TERM...Bowen
AVIATION...RJK
FIRE WEATHER...Entrekin
Area Forecast Discussion
National Weather Service Billings MT
746 PM MDT Mon Apr 17 2017
.UPDATE...
Showers continue to move east, and as of 730 pm MDT were along and
east of a Miles City to Sheridan line. There is some lightning in
Carter County, and in fact, one storm intensified a little north
of Boyes earlier and probably produced some small hail before
weakening. Low level shear definitely stronger in our southeast
courtesy of southeasterly boundary layer winds in this area.
Latest HRRR continues to show showers exiting our east by 05z and
this is consistent with current radar trends. Have adjusted
evening pops to account for all of this. The remainder of the
night will be quiet with decreasing winds from west to east.
We did see a few high wind gusts earlier this evening, not
associated with thunderstorms, including a 64 mph gust at the
Sheridan airport.
JKL
&&
.SHORT TERM...valid for Tue and Wed...
Pacific cold front is currently moving across the forecast area
this afternoon. Surface obs showed the front moved through
Livingston around noon as pressure rises were noted along with
some light rain along with a thunderstorm in the vicinity. Clouds
will be increasing from the west today so these clearing skies
should fill in once again. The front is currently moving through
the central counties and will be moving through the far eastern
areas by early evening. Water Vapor and Visible satellite showing
clearing and subsidence right behind the front so expect some
gusty west/northwest winds behind the front for a short period.
Shower chances will spread from west to east this afternoon into
this evening along with the possibility of an isolated
thunderstorm. As is normal this time of year, with freezing levels
so low, pea size hail will be likely with any thunderstorm.
An upper low and trough off the Pacific Northwest coast Tuesday
and Wednesday will provide for a southwest flow aloft across the
forecast area both days. Unsettled weather will continue both days
with shower chances continuing west of Billings Tuesday as
another disturbance approaches the forecast area. By Tuesday night
into Wednesday, a stronger upper level disturbance moves across
north central Wyoming and across northeast Wyoming/southeast
Montana Wednesday morning. At the same time, a surface low will
move across the Nebraska Panhandle while a 700mb low tracks across
northeast Wyoming. As a result of this placement, models place a
good area of qpf across areas from Yellowstone County southeast to
Carter Counties. As a result, I increased precip chances to
likely for these areas late Tuesday night through most of the day
Wednesday. Temperatures will be a bit above normal Tuesday with
readings in the 60s. Areas of rain Wednesday will allow
temperatures to cool back to the middle 50s to around 60, which is
pretty much normal for this time of year. Hooley
.LONG TERM...valid for Thu...Fri...Sat...Sun...Mon...
Thursday should be a nice day across the forecast area as a ridge
of high pressure passes overhead. To our west, an upper level
trough will begin to push into the region by early Friday
morning. Models diverge with rain chances across the region as
some models want to deepen the upper level low further west
(better rain chances for is) while others quickly move it through
to the south (drier solution). For now left a chance for rain and
mountain snow across much of the area on Friday afternoon.
Good agreement that another ridge of high pressure moves in for
the weekend, keeping conditions mostly dry and warm (in the mid
60s). Another weak disturbance is possible last Sunday afternoon
into Monday so left a mention of rain chances in those periods.
Overall, temperatures will remain at or above normal through the
extended period. Dobbs
&&
.AVIATION...
Showers and thunderstorms over southeast MT this evening should
exit MT by 04z Tuesday. These showers/storms could produce MVFR
conditions and wind gusts up to 45 kt. Otherwise, VFR will prevail
across southern MT and north central WY tonight. RMS/JKL
&&
.PRELIMINARY POINT TEMP/POPS...
Tue Wed Thu Fri Sat Sun Mon
-----------------------------------------------------------
BIL 040/065 041/061 038/065 042/059 040/064 043/066 044/063
02/W 26/R 11/U 12/W 21/B 02/W 30/B
LVM 036/060 037/060 031/062 037/056 033/063 038/065 038/061
13/W 33/R 11/B 33/W 21/B 13/W 31/B
HDN 037/066 042/061 038/068 041/062 039/065 040/068 042/064
11/B 26/R 11/U 12/W 21/B 01/B 30/B
MLS 039/065 042/057 036/067 042/066 042/066 043/069 045/064
41/B 26/R 21/U 01/B 11/B 01/B 20/B
4BQ 039/066 044/058 038/066 040/061 040/063 041/068 044/063
51/B 67/R 31/U 12/W 21/B 01/B 31/B
BHK 036/062 039/058 034/064 037/062 038/063 038/066 040/060
50/B 26/R 31/U 01/B 11/B 01/B 31/B
SHR 036/063 041/056 033/062 039/055 037/060 038/065 040/061
32/W 67/R 21/B 34/W 21/B 01/B 31/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service Caribou ME
1204 AM EDT Tue Apr 18 2017
.SYNOPSIS...
A frontal boundary will remain across the region through tonight
with some snow possible. High pressure is expected to ridge
down across the region on Tuesday into Tuesday night.
&&
.NEAR TERM /THROUGH TODAY/...
Update 12:00 AM: Have adjusted winds, temperature, and dew point
based on latest observations. No other changes.
Previous discussion...
An inverted trof will be the focus for precipitation tonight
and then drier wx in the offing for this term.
The 18Z sfc analysis showed the inverted trof setting up across
the region w/the best convergence residing across northern and
eastern areas. Radar showed precip affecting basically northern
and the eastern section in the form of some snow across the
St. John Valley w/some accumulation occurring(around an inch so
far). Further s, rain and drizzle w/patchy fog. Temps across the
northern 1/2 of the CWA were in the 30s while further s down
into the central and downeast region, temps were in the 50s and
60s thanks to some clearing.
For tonight into Tuesday, the inverted trof will shift westward
per the latest runs of the NAM and RAP which were matching up
nicely w/the radar. 12Z UA showed an 700mb trof sitting back
across Ontario set to swing across the region. This feature in
conjunction w/ the inverted trof at the sfc will allow for an
area of precip to set up say from northern Maine down into
Washington County. Temps will be falling back as colder air
filters down from Canada. It will be cold enough even into
Washington County for some snow. The best chances for
accumulations will be in the higher elevations. This cooldown
w/cooling temps will lead to some icing possible on area roads.
Things are expected to drier on on Tuesday as high pres to the
n ridges down across the region. It will be a chilly day
w/clouds hanging on across the region especially to the north
and west. Daytime temps are forecast to be 5 to 10 degrees below
normal for mid April
Tuesday night will be a rather chilly night w/partial clearing
late at night. Overnight temps look like they drop back into the
mid/upper 20s for the northern 1/2 of the CWA w/downeast around
30 or so.
&&
.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
Return flow from the south expected by Wednesday as the surface
high pressure pulls off into the Canadian Maritimes. Clouds will
be on the increase during the day as a 500m shortwave trough
approaches the state from Quebec province. Fairly good agreement
that rain will spread from west to east during the day on
Wednesday. Could be a few snowflakes mixed in across the higher
hills at the onset. Rain showers will continue into Wednesday
night, mixing with snow across the higher terrain. Overall QPF
amounts look light with the wave, with most areas receiving
between a tenth to quarter of an inch. Not expecting to much of
a rise on any area rivers. Showers expected to end Thursday
morning, with some partial clearing during the day on Thursday
as weak ridging builds over the area. Temperatures will run near
average for this period.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
Active pattern continues Thursday night into Friday as an Ohio
Valley low pressure system quickly tracks into New England.
Still a lot of spread and run-to-run discontinuity with this
system in regards to timing and track of the surface low. The
ECMWF/GEM have trended north and more aggressive with the QPF
compared to their previous runs and are closer to the GFS
solution. We will have to watch this event in regards to how
much rain falls due to elevated rivers and how much snow may
fall across Northern Maine Friday night. The surface high due
north over Quebec province and thermal profiles will support
snow, especially after sunset on Friday night. Will watch how
this evolves over the next few days. Partial clearing is
expected by Saturday and all guidance is showing high pressure
cresting over the region on Sunday. Very little agreement in the
models by Monday next week. Overall temperatures will run near
average for this period.
&&
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: IFR/MVFR conditions tonight across the north w
locally LIFR conditions in snow. VFR dropping to MVFR and
perhaps IFR later tonight for KBHB & KBGR. IFR/MVFR for early
Tuesday for all terminals w/a gradual improvement to VFR for
KBHB & KBGR by 15z or so. VFR for all terminals for Tuesday
night.
SHORT TERM:
MVFR conditions possible later in the day on Wednesday as rain
showers and lower cigs move into the region as a weak area of
low pressure approaches. Partial clearing on Thursday before
rain and maybe some snow for the northern TAF terminals returns
Friday into Friday night. IFR conditions or lower could be
possible through the period at all TAF terminals.
&&
.MARINE...
NEAR TERM: No headlines this term. Will see winds increase
slightly tonight to 10 to 15 kts and turn more to the n and hold
this direction and speed into Tuesday. Seas will average
3-5 ft w/an ese swell component. Winds will gradually drop back
Tuesday night and turn more to the e.
SHORT TERM:
South winds off the waters on Wednesday will decrease and turn
more easterly during the day on Thursday. Seas will generally
run 3 to 5 through this period. More significant coastal low
expected by Friday with buildings seas and prolonged period of
easterly winds.
&&
.HYDROLOGY...
The mattawamkeag River at Mattawamkeag remains above flood
stage this evening, and is expected to remain above flood stage
this week with minor flooding. Other rivers across the HSA
remain elevated and are running fast and cold, but are not
expected to flood. A weather system late in the week will need
to be watched closely for the potential of rain and snow that
could cause additional rises.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...Mignone
Short Term...
Long Term...
Aviation...Mignone/
Marine...Mignone/
Hydrology...
Area Forecast Discussion
National Weather Service Goodland KS
555 PM MDT Mon Apr 17 2017
.SHORT TERM...(This evening through Tuesday)
Issued at 214 PM MDT Mon Apr 17 2017
This afternoon-Tonight: Stratus, patchy fog, and drizzle have
lingered in region of BL moisture pooling in southerly flow just
east of surface trough. HRRR shows this pocket of better moisture
slowly drifting north-northwest. This stratus should hamper severe
threat this afternoon further east, and if this lingers through the
evening as long as SREF probabilities may indicate it may. There has
been enough clearing in eastern Colorado to allow for better
instability to develop, though this is still just outside our CWA.
Short range guidance still favors enough clearing and instability to
support activity developing transitioning eastward into our CWA.
Good deep layer shear (possibly decent low layer shear where there
is clearing) may support more organized cells (primarily in CO).
Beside elevated convection further east, confidence is higher in
severe threat primarily in our far west late this afternoon/evening.
Better forcing is still expected o slide north of our CWA, though
with WAA ahead of surface low and LLJ we may see convection
maintained eastward and this is still favored by all guidance. I was
not confident enough to increase coverage beyond 30 percent despite
overlapping precip signals.
Saturday: There is a chance we may see stratus linger Saturday
morning behind the weak cold front (behind surface low), but this
should burn off as drier air is shown to finally overspread our CWA.
WAA during the day should also support warmer temperatures (assuming
clearing skies), and highs should approach 80F for most (low to mid
80s possible). At this point lack of forcing (generally subsident),
less instability, and lack of surface feature should support dry
conditions during the day Saturday once main precip chances end early
in the morning.
.LONG TERM...(Tuesday night through Monday)
Issued at 203 PM MDT Mon Apr 17 2017
Going into the extended period...the passage of a shortwave across
the region Tuesday will allow for nearly zonal flow to set up over a
good portion of the country...with H5 ridging over the southern
tier. Zonal flow lasts into the Thursday night timeframe w/ only a
quick moving shortwave passing just north of the region Tuesday
night into Wednesday morning. The track of this system will focus
any potential precip along the extreme northern border.
This shortwave will give way to a much stronger system that
initially comes out of the Pacific NW...then SE off the Rockies as a
closed low before shifting into Plains region across Kansas.
Following its ride off the Rockies the system does slow into the
Plains and will allow for potential area-wide precip lasting from
Thursday night into Saturday morning. System slowly clears region
thru the day Saturday...giving way to H5/H7 ridging for the
remainder of the weekend into next Monday. There is a weak shortwave
that follows the ridging on next Monday...but latest model runs keep
the system dry as it shifts into the western/central Plains.
For QPF purposes...the late week system has potential to bring 0.60-
1.00" of rain to the area. Some thunder potential during this time
that could enhance local amts. The northern tier system could bring
a few hundredths of an inch of rain.
Extensive cloud cover will play key role in area temps in the
extended. For Wednesday ahead of main precip/cloud shield mainly 70s
for highs with a few 80s in the SE. 50s and 60s for Thursday into
Saturday. Coolest on Friday as exiting system brings in cooler air
on return flow. Upward trend going into the latter portion of the
weekend into next week with 60s giving way to low 70s. Overnight
lows will peak near 50F Tuesday night...dropping into the 30s at the
end of the week before rebounding into the 40s by end of weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 426 PM MDT Mon Apr 17 2017
The moist southerly near surface flow is keeping the low clouds
in place across much of the central high plains region this
evening. Expect the surface trough moving across the region to
change the wind direction to a north or northwest direction after
14Z with winds turning southeast again by late in the day as the
surface lee trough retrogrades back to the front range.
KGLD will start out MVFR, but will become VFR after 02Z.
MCK should remain VFR through the TAF period.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...DR
LONG TERM...JN
AVIATION...LOCKHART
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1008 PM EDT Mon Apr 17 2017
.SYNOPSIS...
A weak cold front will push into the area from the north tonight,
enhancing the possibility of showers and thunderstorms. This front
is expected to drop just south of the forecast area Tuesday and then
return north as a warm front on Wednesday. This will keep unsettled
weather in the forecast through midweek. Another storm system will
impact the region next weekend.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 1000 PM EDT: One area of showers and TSTMS continues to sag
southeastward across the Upstate, while another area of convection
approaches from the west. The upstream activity is generally
weakening, with only a few hundred J/kg of CAPE at most to work
with. The CAMs that showers will continue into the overnight, but
should decrease in coverage. PoPs were tweaked to line up with these
trends.
Otherwise, an area of high pressure ridge down the Eastern Seaboard
overnight, pushing the cold front thru the southern edge of the
CWFA. Cold air damming will develop, with easterly upslope flow and
upglide overnight allowing precip to expand again in the early
morning (either as light showers or drizzle). Isolated TSTMS remain
possible thru roughly midnight over the fcst area, but otherwise
profiles don`t look supportive of elevated convection. Overnight,
min temps should be about 10 degrees above normal with high temps
tomorrow about a category below normal where the CAD is in place.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 245 PM EDT Monday...a kind of tricky forecast through the
middle part of the week because of what should be an ongoing cold
air damming wedge in place Tuesday night and into Wednesday. The
guidance shows plenty to maintain the wedge, with low level
isentropic lift and warm advection over the cold dome, along with
easterly upslope flow to maintain precip production centered on the
Blue Ridge overnight and early Wednesday. A high precip probability
is warranted, so chances have been raised into the categorical range
on the Blue Ridge and likely in most other places. The isentropic
lift gradually weakens early in the day and the warm advection
late in the day, so precip chances go down, however it is entirely
likely that patches of light rain/drizzle will be more widespread
and persistent than indicated. It is the high temps that are really
problematic with a high bust potential. Have nudged downward a
degree or two so we range from the mid-60s in the I-40 corridor to
the mid-70s across the Lakelands. However, it is at least as likely
that temps won`t get out of the 50s in the usual damming locations.
The weakening trend of the forcing continues into Wednesday night
while the remaining wedge cool-pool drains away, so in spite of the
model guidance showing some response, I think we will see a period
of inactivity, thus the dry forecast by early Thursday morning. We
are left with a nearly zonal upper flow pattern for Thursday and
into Thursday night, with little in the way of forcing. Although,
we should retain enough low level moisture to fuel the development
of convection with some diurnal heating. This suggests accepting
the model portrayal of what looks like a typical diurnal convective
precip scenario, thus the chance over the higher terrain and slight
chance to the east. Temps will be warmer on Thursday...well above
normal. A front should approach from the west early Friday morning,
but will most likely remain to our west through sunrise.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 240 PM EDT Monday: Guidance remains in general agreement
through the period. An upper low moves from the Great Lakes on
Friday to new England on Saturday as short wave ridging builds over
our area in its wake. A cold front associated with the upper low
moves across the area Friday with high pressure building in from the
north Friday night. There will be enough moisture, forcing, and
instability for scattered diurnal convection to develop Friday.
Precip returns for Saturday as the surface high quickly translates
east allowing a moist southerly flow to develop. Temps around 10
degrees above normal Friday drop to near or slightly above normal
for Saturday with a cooler air mass and clouds.
A stronger upper low then moves into or across the area Sunday and
Monday. The GFS keeps the low more open and faster with a deep trof
developing on Sunday. The axis of this trough reaches the spine of
the Appalachians by the end of the day then quickly moves east of
the area Monday. The ECMWF keeps the low closed and slower bringing
it to the Middle TN/KY border by the end of the day Sunday then
slowly moving it across the Carolinas Monday. This, of course,
creates differences in the surface pattern. The GFS spreads precip
across the area on Sunday with a hybrid damming pattern as the
surface low takes on a Miller B type configuration. The cold front
and lows move east of the area Sunday night ending precip with a
relatively dry Monday. The ECMWF has a stronger low to our west with
a strong cold front. Precip still spreads over our area Sunday but
with some in situ damming. A triple point low forms along the front
and the developing TMB and generally moves along the I-85 corridor
Sunday and Sunday night. The complex low and frontal systems only
slowly move east of the area Monday. Of course, these differences
could have a profound effect on the amount of precip and or any
significant thunderstorm development. Therefore, have gone with a
blend for the forecast which highlights the agreements. PoP
increases to likely through Sunday then diminishes on Monday. Do
show thunderstorms for a portion of the area as well. Temps remain
nearly steady a little below normal both days.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: An area of showers with a couple of isolated
TSTMS continue to cross the NC mountains and into the Upstate.
Instability looks limited, but highest in the Upstate. Using the
HRRR as the preferred guidance with respect to convection, I will go
with -SHRA or VCSH at the NC TAF sites, and VCTS for the first 1-2
hours in the Upstate TAFs this evening. There should then be a lull
in precip late tonight thru at least mid-morning Tuesday. Meanwhile,
a backdoor cold front will push thru the area late this evening,
bringing winds around out of the NE, except switching to SE at KAVL,
with gusts expected during the day. Low clouds should begin to
develop as cold air damming (CAD) sets up. Guidance is in good
agreement on MVFR to IFR cigs by daybreak. If the wedge deepens,
cigs may improve, especially across the NC piedmont. But another
round of showers is expected to develop atop the wedge, and may help
lock in or lower cigs further during the day. Deeper convection
should stay south and west of all the TAF sites, due to the stable
air within the wedge.
Outlook: CAD should persist Tuesday night and most of Wednesday as
well. Low clouds and showers are expected to be widespread under
the CAD. The wedge should erode by early Thursday with a return to
more typical diurnal thunderstorm potential for Thursday and Friday.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 100% High 87% Low 41% Med 76%
KGSP High 100% Med 79% Low 51% Med 77%
KAVL High 100% High 91% Med 70% High 83%
KHKY High 100% High 86% Low 55% High 81%
KGMU High 100% High 86% Low 51% High 81%
KAND High 100% High 94% Med 65% High 97%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...SW
NEAR TERM...ARK/JPT
SHORT TERM...PM
LONG TERM...RWH
AVIATION...ARK
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1020 PM CDT Mon Apr 17 2017
.DISCUSSION...
The MCV appeared to be slowly drifting eastward toward Washington
County at 9:30 PM. High res models were showing the possibility
of redevelopment east and south of the MCV tonight. The caveat is
that each model has a different solution as to its location and
track through the night. The HRRR looks to be verifying best so
far this evening. The latest NAEFS climatological percentile PW
has SE Texas in the 97th to 99th percentile tonight. The PW of
1.50 inches agrees with the 00Z CRP sounding.
Given the latest HRRR model runs and the input from the other
high res models, have tweaked the POPs upward for the remainder of
tonight. Also adding locally heavy rainfall to those areas with
rain chances 60 percent or greater through mid morning Tuesday.
40
&&
.PREV DISCUSSION... /ISSUED 650 PM CDT Mon Apr 17 2017/
AVIATION.../00Z TAF/
Short term forecasting for TAFs will lean heavily on GOES 16
data, radar imagery and surface analysis due to a mesoscale
convective vortex (MCV) moving into the area spawned from last
night`s convection across south Texas. Also we have a cold pool
driven outflow boundary with a line of showers and storms moving
towards SE Texas from central Texas. Convective allowing models
provide at least some guidance but it does not take much for storm
mode and evolution to change on the mesoscale.
Trends for this evening`s convection should be downward and
expect convection to be dissipating through 02-03Z. There should
be a break in activity but with the MCV convection may start up
mid morning so trended TAFs in that direction. KCLL/KUTS may be
impacted by outflow this evening as well which is not mentioned in
TAFs. These may need to be amended depending upon convective
trends with activity to the north. MVFR ceilings are forecast for
the morning hours 09-15Z but will depend upon convection. Given
cloud cover already over much of the area I have a hard time
thinking IFR/fog will develop.
Models show the MCV getting stretched out tomorrow but there
should be plenty of lift with it along with moisture. Locally
there should be 1.5 to 1.8 inches of precipitable water so it may
not take much heating to trigger convection given available lift
and outflow boundary present. TAFs will carry VCTS for most of
tomorrow with hopes of fine tuning possible rounds of TSRA with
future TAF updates.
Overpeck
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 66 83 67 84 67 / 70 50 10 20 10
Houston (IAH) 67 83 68 84 68 / 60 60 10 30 10
Galveston (GLS) 72 81 72 80 73 / 40 50 20 20 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&
$$
Discussion...40
Aviation/Marine...39
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
654 PM CDT Mon Apr 17 2017
.SHORT TERM...(This evening through Tuesday)
Issued at 336 PM CDT Mon Apr 17 2017
An upper level trough will move across the Northern and Central
Plains tonight. Steep mid level lapse rates 7.5-8.0 c/km and
sbcapes 500-800 j/kg will combine with 0-3 km shear from 40 to 45
kts. This will be supportive of marginally severe hail and wind
gusts west of valentine through Ogallala. Coverage will likely be
isolated at best, with rapid refresh and RAP models showing very
little development into the northwest.
The best forcing aloft will be across South Dakota. However, with
precipitable water values around three quarter of an inch early
this evening increase to over one inch across the eastern
forecast area overnight. IF any organized areas of storms do
develop, brief heavy rain is likely. Thunderstorms chances are
from 20 percent across the southwest, and 30 to 40 percent across
north central and central Nebraska. The trailing end of any
showers or storms should exit the eastern zones by daybreak. A
weak cold front will also sweep thorugh the area overnight.
.LONG TERM...(Tuesday night through Monday)
Issued at 336 PM CDT Mon Apr 17 2017
On Tuesday, partly cloudy and mild with highs ranging in the 70s.
Southwesterly flow will be across the western conus as nearly
zonal flow exists across the Central Plains. A disturbance will
exit California and move into the Great Basin on Tuesday. By
Tuesday evening, this upper trough will approach the area,
providing another chance for showers and thunderstorms. A warm
front across northern Kansas will remain nearly stationary.
Increased instability and 0-3km shear from 30-45 kts sufficient
for strong storms across most of western Nebraska overnight. The
thunderstorms are expected to be elevated, so marginally severe
hail will be the most likely hazard. Some storms may also contain
brief heavy rain.
As the upper trough crosses the area on Wednesday, showers and a
few thunderstorms remain likely across north central Nebraska.
Chances decrease or end across southwest Nebraska. Models differ
on amount of cold air advection behind the front. Current forecast
highs remain near the previous, although the GFS model would
support warmer highs in the lower and mid 70s across southwest
Nebraska. Northwest winds to increase to 10 to 25 mph Wednesday
afternoon.
An upper trough will dig across the Pacific Northwest into the
Great Basin on Thursday, and close off over Colorado and western
Kansas on Friday afternoon. This southeastward tracking system
will provide better chances for showers to the southwestern half
of the forecast area Thursday night through Friday night, while
most of the northeast should remain dry. Aside from a slight
chance for morning showers southeast on Saturday morning, the
remainder of the weekend looks dry. A mid level disturbance Monday
for a slight chance of showers.
Forecast highs on Wednesday contrast from mid and upper 50s
north, to the mid 60s to lower 70s south. Highs in the mid 60s
Thursday, cool to the mid and upper 50s by Friday and Saturday,
influenced by the upper trough and Canadian high pressure across
the region. By Sunday, upper ridging builds back into the the
region to bring warmer highs in the mid and upper 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 649 PM CDT Mon Apr 17 2017
Mid and high clouds over most of western Nebraska tonight. Some
MVFR cigs will move into southwest Nebraska over night. Strong
southerly flow will continue through the early morning. Some
isolated showers or virga will continue to move to the east over
the Nebraska Sandhills through midnight. Winds will shift to the
west and then northwest through Tuesday morning. With uncertainty
of showers have only carried vcsh.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Roberg
LONG TERM...Roberg
AVIATION...Power
Area Forecast Discussion
National Weather Service Lake Charles LA
1042 PM CDT Mon Apr 17 2017
.UPDATE...Latest model output showing deeper moisture associated
with east Texas trof to expand eastward into the region
overnight. Have introduced pops for all but the most eastern
portion of the forecast area, with the highest over southeast
Texas. Radar showing considerable convection being maintained just
to our west with activity migrating east. Have also noted some
development over the near coastal waters.
&&
.PREV DISCUSSION... /issued 722 PM CDT Mon Apr 17 2017/
DISCUSSION...
For 00z TAF issuance.
AVIATION...
Afternoon diurnal convection has been a little more lively today
as area lies in weak troffing aloft and a very soupy
airmass...although recent radar trends show this slow-moving activity
is beginning to diminish. Have not included any additional precip
for the remainder of the night although regional 88Ds do show
precip associated with a weakening MCV approaching metro Houston
at this time...latest HRRR runs agree on this fizzling with little
to no impacts expected on the swrn terminals for now. After
another round of low clouds late tonight, we should see more
convection popping up with daytime heating tomorrow as weak low
aloft builds slowly ewd into the forecast area.
25
PREV DISCUSSION... /issued 250 PM CDT Mon Apr 17 2017/
DISCUSSION...
Wx map shows surface high pressure ridging across the Northern
Gulf, keeping area with southeast winds. Radar showing scattered
showers and thunderstorms along and north of I-10 in Southeast Texas
and Louisiana. With coverage more uniform and further west resembling
sea breeze convection, had to bump up pops across SE TX again
this afternoon. Temperatures this afternoon are in the lower/mid
80s.
Scattered afternoon showers and thunderstorms expected through
early this evening, diminishing after sunset with the loss of
daytime heating.
Abundant Gulf moisture, daytime heating, and more defined SW to
NE oriented trough aloft across E Texas to the Western Gulf is
expected on Tuesday. This should provide increased focus and
instability, leading to better than normal chances of showers and
thunderstorms by Tuesday afternoon.
For Wednesday through Friday, the weakness aloft and trough axis
is expected to move east of the area. Thus, weak ridging with
increased stability and drier air aloft should limit our shower
chances to 20% at best.
By Saturday, a significant upper level trough aloft will move across
the Central and Southern U.S. brining increased precipitation
chances by Saturday afternoon and evening across the region.
Cooler and drier air expected behind the frontal passage Saturday
night into next Sunday.
DML
MARINE...
High pressure off the east coast ridging westward across the Gulf
coast will provide a predominate southeast to south flow for most
of this week. Abundant Gulf moisture, daytime heating, and a
relative weakness in the upper levels, will combine for a daily
chance of scattered showers and a few thunderstorms through
Tuesday afternoon. Shower and thunderstorm chances will diminish
Wednesday through Friday as high pressure aloft builds back over
the region. A cold front is expected to bring an increased chance
of showers and thunderstorms Saturday, followed by offshore flow
after the frontal passage.
DML
&&
.PRELIMINARY POINT TEMPS/POPS...
AEX 64 82 64 84 / 20 50 20 20
LCH 67 81 66 83 / 20 40 20 20
LFT 66 82 64 83 / 20 40 20 20
BPT 67 82 68 83 / 30 40 20 20
&&
.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...None.
&&
$$
PUBLIC...23
Area Forecast Discussion
National Weather Service Lubbock TX
1100 PM CDT Mon Apr 17 2017
.AVIATION...
The latest guidance still indicates that IFR ceilings and
visibilities will develop in the KCDS area around 09 to 10 UTC.
There is a small chance that KCDS could see dense fog and LIFR
VSBYs from 12-15 UTC. KLBB and KPWV look to remain VFR at this
time. E-SE surface winds will come around to the south on Tuesday
and increase into the 12-16 kt range with VFR conditions through
Tuesday evening.
&&
.PREV DISCUSSION... /issued 655 PM CDT Mon Apr 17 2017/
AVIATION...
Moist upslope flow at KCDS is expected to result in a period of
MVFR to IFR ceilings early Tuesday morning. We expect KLBB and
KPVW to remain VFR, although there is a non-zero chance some
category reductions could briefly impact either terminal.
Otherwise, winds will come around to the south Tuesday morning,
with VFR conditions through the end of the forecast.
UPDATE...
Despite several boundaries seen on radar in the moist E-SE flow
across the Rolling Plains, it appears that the cap will be too
strong for any local t-storm development this evening, and we have
dropped PoPs below mention. The HRRR continues to generate a small
t-storm complex in the Panhandle night that could possibly edge
southeast toward our northeast counties after midnight. This
potential looks very small at this point.
PREV DISCUSSION... /issued 349 PM CDT Mon Apr 17 2017/
SHORT TERM...
Southward propagating MCS continues across north and northwest Texas
with most recent development along west-moving outflow boundary
along and north of I-20. Previous boundary from overnight convection
has brought deeper moisture to areas east of the Caprock where
surface dewpoints are holding in the mid-upper 50s. A more aged but
still discernible W-E surface boundary exists across the far
southern CWA where another moisture and instability axis exists.
Meanwhile hi-res satellite imagery shows a shortwave trough working
across the High Plains of West Texas with overall forcing and
enhanced shear relatively absent from this feature. Expect moderate
instability to exist across much of the eastern half of the area by
early evening coincident with deeper moisture with potential storm
development along previously mentioned boundaries and within upslope
regime immediately along the Caprock escarpment. Lack of shear and
deficient quantity of CAPE will limit overall health and vigor of
any updrafts that do form. Expected easterly flow will maintain
higher low level moisture across the Rolling Plains so have added
mention of patchy fog there toward daybreak. Mid level heights will
increase overnight as shortwave ridging builds across the region. A
surface trough will strengthen during the day Tuesday with increased
moisture gradient and an uptick in winds. The lack of any upper
level support, warmer and drier temps aloft should effectively keep
a lid on convective development.
LONG TERM...
Do not anticipate major changes to medium range forecast this
period. Weak shortwave ridging Tuesday night with southerly boundary
flow will give way to mid/upper flow becoming more zonal by
Wednesday. W/SW surface winds will allow for a warm day Wed with
dryline pushing east into the eastern Rolling Plains or perhaps east
of the entire region. In any event, temps warm into the upper 80s or
even lower 90s Wed with a mostly dry and capped atmosphere. Some
changes coming by Wednesday night as upper low and trailing trof
moving eastward across the central/northern Plains will push
associated cold front into our region by Thursday morning. NAM
hinting at some post frontal convection Thursday afternoon.
Definitely cooler then with NE surface flow. Ensemble MOS has high
temps back in the 70s on the Caprock.
Thursday night into Friday...attention shifts to SE moving
negatively tilted upper trof which is progged by models to approach
W TX Thursday night or early Friday. With likely moist easterly
upslope flow combining with forcing...could see a few showers and
thunderstorms in this time frame and will likely leave pops as is
with chance category across the northern South Plains and SE
Panhandle and slight chance elsewhere except over the SW where pops
unlikely. This second upper low is progged by GFS to be located
across southern KS early Saturday with more substantial
front/cooling into the weekend. Rain chances by Saturday look slim
with system quickly racing to the NE of the region. Sunday and
beyond...upper ridging looks to build in early next week with a dry
northwesterly flow thereafter.
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
33
Area Forecast Discussion
National Weather Service Melbourne FL
945 PM EDT Mon Apr 17 2017
.UPDATE...
East-west axis of expansive Atlantic pressure ridge lies near the
Florida-Georgia border and continues to sag south. Weakening/veering
onshore ESE-SE flow has dropped to about 10KT in the surface-1KM
layer. 3.9UM IR satellite imagery shows large swath of higher-based
stratocu/lower based altocu (6-8KFT), which formed over the southern
third CWA in weak upglide and pancaked up against the 770-750MB cap,
beginning to break up. Local radars show a few piddling light rain
showers over the interior SW peninsula dying off, with nothing of
note upstream over the Atlantic, even offshore SE Florida. Current
temps in the U60s-L70s north/inland and M-U70s central-south coast.
Remainder of tonight...flow should be light enough to allow boundary
layer to decouple over all areas, resulting in min temps across most
areas to drop into the L60s, with a few U50s north/inland and some
M60s along the immediate Treasure Coast. threat for localized dense
smoke/fog mixture will exist near any of the many smoldering fires
across the CWA. Commuters are urged to check for road conditions and
potential road closures near the problematic spots over the past
week or so. Current forecast, which also shows a small chance for
coastal showers for the southeastern 3 counties, looks fine.
&&
.AVIATION...VFR. Localized dense mix of smoke/mist should be
confined to areas away from local forecast aerodromes.
&&
.MARINE...Current buoy and C-MAN reports indicate winds AOB 10KT
with seas 3-4FT in an 8-9sec period swell. CWF looks spot on.
&&
UPDATE/AVIATION...Cristaldi
DSS/IMPACT WX...Weitlich
&&
...Only Meager Rain Chances Through Late Week...
Tuesday...
RAP analysis shows mid lvl troffing over the GOMex has eroded the
wrn flank of the ridge aloft, mean H85-H50 flow has shifted to S/SW
AOB 5KTS. This weakness in the ridge will allow a pocket of enhanced
moisture over south FL to works its way north into the Treasure
Coast/Lake-O region by daybreak Tue. However, while the strength of
the H100-H70 ridge has weakened, the definition of its anticyclonic
curvature remains distinct clear back to the TX coast.
Position of the ridge axis will limit the ability for low lvl
moisture to work its way much farther north than the Lake-O region.
At the same time, indications of any meaningful mid lvl short wave
energy or upr lvl jet development overhead thru Tue evng are weak at
best. As a result, the 17/12Z GFS MOS PoPs appear way overdone acrs
the Treasure Coast/Lake-O region. Will undercut by a good 20-30pct,
limiting PoPS to areas south of Cape Canaveral and the Orlando
Metroplex...capping at 30pct. No change in airmass...max temps
should be near climo avg...L80s along the coast and M80s inland.
Wed-Thu...
More of the same continues. High pressure over the western
Atlantic is forecast to keep low-level flow east to southeasterly.
Air mass continues to be too dry for any sort of decent
precipitation chances with MOS guidance advertising generally
10-15 percent PoPs in most areas. Have only included a slight
chance of showers for Brevard county southward over toward
southern Okeechobee on Wednesday afternoon and evening. Overnight
Wednesday into Thursday only have a slight chance of showers for
the immediate Treasure Coast. Amounts will be very light. High
temperatures will be low 80s near the coast and mid 80s inland.
Lows will be mid 60s near the coast and lower 60s inland.
Fri-Mon...
Axis of Atlantic surface ridge axis will extend over central
Florida through Sat, then the GFS and ECMWF show the western end
of the ridge breaking down on Sunday as a frontal trough
approaches. Subsidence and very dry air are forecast over the area
on Friday then the GFS indicates a narrow ribbon of moisture
working in from the east/southeast on Saturday. This moistening
looks iffy as the ECMWF remains quite dry, but will retain the
small POP from the previous forecast for the Treasure Coast.
On Sunday, there looks to be a chance for sea breeze convection
ahead of approaching frontal trough, though northward transport of
moisture is still somewhat questionable. On Mon, the GFS shows a
band of slightly higher frontal band moisture moving across the
area. Though frontal convergence is forecast to be weak, a bit
cooler temps aloft associated with an approaching shortwave trough
may lead to a chance of storms. It`s way too far out in the
forecast to put a lot of faith in exact model solutions and will
keep POPs Sun-Mon around 30 percent and not include thunder yet.
Temps will continue above normal with highs mostly in the upper 80s
inland and reaching the mid 80s along the coast by Saturday.
&&
.AVIATION...Thru 18/18Z.
Sfc winds: Thru 18/00Z...E/SE 8-12KTS...ocnl G18-22KTS S of KVRB.
Btwn 18/00Z-18/03Z...bcmg E/SE 4-7KTS. Btwn 17/03Z-17/06Z...bcmg
vrbl E/SE AOB 3KTS. Btwn 18/12Z-18/15Z...bcmg E/SE 8-12KTS.
Vsbys/WX/Cigs: Thru 18/12Z...E of KMLB-KOBE areas CIGS btwn FL030-
040 slgt chc MVFR shras. Aft 18/12Z...S of KISM-KMLB slgt chc MVFR
shras...S of KGIF-KVRB chc MVFR shras.
&&
.MARINE...
Tonight-Tuesday...High pressure ridge centered south of Bermuda and
extending west acrs the FL Panhandle will maintain a light to gentle
E/SE breeze acrs the area...locally moderate along the Treasure
Coast Tue aftn as the onshore flow promotes the formation of an Atlc
sea breeze. Seas 3-4FT nearshore and 4-5 feet offshore early this
evng...subsiding to 2-3FT nearshore and 3-4FT offshore and in the
Gulf Stream by daybreak Tue. Slgt chc of shras south of Cape
Canaveral and in the Gulf Stream.
Wed-Thu...High pressure over the western Atlantic will remain
north of the waters and maintain a east/southeast wind flow.
Speeds look close to 10 knots in the north and 10-15 knots in the
south. Seas mainly 3-4 feet.
Fri-Sat...Surface ridge axis is forecast to settle across central
Florida. This will keep the gradient flow around 10 knots. The
daily sea breeze and nocturnal marine wind increases will produce
speeds 10-15 knots. Overall, conditions look good with seas 2-3
feet.
&&
.FIRE WEATHER...Ridge axis over the FL panhandle will maintain an
E/SE sfc/transport flow acrs central FL thru midweek. This should
keep aftn min RH values AOA 40pct over the interior and AOA 50pct
along the coast. However, the prospect for any significant
rainfall is low through late week. Dry soil and associated
drought indices will continue their slow, steady climb.
Winds at night will be light and the low level inversion will
promote trapping of smoke near the surface and continue to
exacerbate visibility problems on some roadways near smoldering
fires.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 61 80 65 80 / 0 10 10 10
MCO 62 85 65 85 / 10 10 10 10
MLB 63 79 68 80 / 10 20 10 20
VRB 63 79 67 80 / 20 20 10 20
LEE 62 86 65 86 / 10 10 0 10
SFB 61 84 64 84 / 10 10 10 10
ORL 62 85 65 85 / 10 10 10 10
FPR 63 79 66 81 / 20 20 10 20
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Area Forecast Discussion
National Weather Service Raleigh NC
1002 PM EDT Mon Apr 17 2017
.SYNOPSIS...
A cold front will drop southward into central NC overnight. This
front will stall in vicinity of the SC border through late Tuesday,
then head back to the north as a warm front Tuesday night and
Wednesday.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 1002 PM Monday...
Surface cold front and H8 trough will drop slowly south,in back-door
fashion, settling near the SC state line by daybreak.
Broken band of pre-frontal showers and storms will continue to move
east-southeast through the Sandhills and coastal plain over the next
couple of hours. Loss of daytime heating and cooling from convective
outflow has worked in tandem to stabilize the boundary layer. Thus,
once the aforementioned convective band exits the forecast area in
the next 2 to 3 hours, any re-development along the southward
sinking cold front should primarily be in the form of showers
overnight.
Low level nely flow will gradually advect a cooler air mass into
central NC overnight. Thus should see minimum temps vary from the
mid 50s far north to 60/lower 60s south.
&&
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 355 PM Monday...
A hybrid cold air damming scenario unfolds Tuesday as northeast flow
near the surface advects a cooler more stable air mass into our
region during the morning. A few thousand feet above the surface, a
swly flow will maintain enough lift to produce overcast skies. This
set-up will be more pronounced across our western areas as low level
easterly flow will bank up against the higher terrain. This should
result in overcast skies and much cooler conditions. Forcing does
not appear strong enough for widespread precipitation, though expect
a few showers to occur in vicinity of the stalled sfc boundary.
Enough dry air may work its way ne into our northern coastal plain
counties to result in partial sunshine in the afternoon. Thus,
should see the warmest high temps Tuesday across the northeast third
of the forecast area with temps 65-70. Overcast skies across the
west-southwest will hold max temps in the low-mid 60s.
A mid level s/w approaching from the west will enhance the sly flow
above the stable surface layer Tuesday night. This overrunning set-
up should cause scattered showers to blossom over the sw half of
central NC, especially overnight Tuesday night. Expect a diurnal
change in the temperatures of no more than 4-6 degrees Tuesday night
across the sw half while temperatures across the ne will cool after
sunset under variably cloud skies.
&&
.LONG TERM /Wednesday through Monday/...
As of 310 PM Monday...
Wed/Wed night: Models depict the gradual erosion of the low level
stable pool during the day, although given that the NAM/GFS/ECMWF
all show a subtle mid level perturbation shifting into the area from
the west, initiating precip over western/central/southern NC,
history tells us that the models may be too fast to erode this
cooler surface air mass, even in the south. Will trend temps a shade
under statistical guidance, with highs ranging from the mid 60s NW
to the lower 70s SE. Dynamic forcing for ascent will overall be
small given the weak mid level flow resulting in minor DPVA, and
upper divergence will also dwindle as it heads east across NC during
the day. But PW is projected to exceed 1.3", highest SE, with weak
steering flow potentially leading to slow-moving cells generating
elevated localized rainfall, along and ahead of a weak 850 mb trough
moving NE across the region. Expect good chance to likely shower
coverage areawide, highest in the western CWA, during the first part
of the day, shifting into SE sections and slowly decreasing during
the afternoon as lift mechanisms decrease, followed by largely dry
conditions overnight as the mid-upper levels dry a bit and an in
situ mesohigh forms over the western Carolinas. Areas of stratus are
likely Thu night with strengthening 925 mb moisture transport within
and just above the stable depth. Lows in the upper 50s to near 60,
resulting in a diurnal temp range of less than 10F across much of
the Piedmont.
Thu/Thu night: We should finally see erosion of the stable pool Thu,
as 850 mb winds become northwesterly as the 850 mb ridge becomes
more W-E oriented and settles over southern GA. Very warm temps will
return within SW low level flow, ahead of the cold front moving
through the OH Valley, and weak flat mid level flow combined with
downslope warming at 850 mb should allow for fair skies and some
decent insolation. With a general lack of lift mechanisms, low deep-
layer shear, and unimpressive mid level lapse rates, a dry forecast
is favored, with only isolated chances in the SE due to a possible
inland-moving sea breeze, and in the NW with terrain-affiliated
convection shifting off the mountains. Continued dry Thu night ahead
of the incoming front. Highs in the mid 80s and lows in the lower to
mid 60s.
Fri through Mon: Looking like a trend to stormier conditions in this
period. The cold front to our NW early Fri will be tied to a
northern stream trough crossing the Great Lakes and Northeast Thu
night through Sat, leaving a weak longwave ridge over the Southeast
states and Carolinas early in the period, which should somewhat
limit the southward progression of the cold front through the
Carolinas, despite a strong surface low associated with the mid
level low and a cool high pressure building in behind it. I tend to
favor the ECMWF, which stalls the front near the NC/SC border, over
the faster and farther-south frontal passage of the GFS. Expect good
shower/storm chances with frontal approach Fri afternoon/evening,
followed by a short relative lull in precip late Fri night into Sat.
The next potent mid level wave, moving onto the West Coast Wed
night, is projected to deepen over the central CONUS on Sat, then
amplify over the Ohio Valley/Mid South/Gulf States Sat night/Sun and
over the Eastern Seaboard Sun night/Mon (although its strength
depends greatly on how much phasing takes place with the northern
stream, a factor that is difficult to determine with any confidence
this far out). Storm coverage and strength should both be on the
increase Sat night/Sun into at least early Mon, with the retreating
stable pool/wedge air mass complicating matters with its enhanced
low level vorticity field, yielding a potential strong to severe
storm risk, if enough instability can be achieved. We should see a
decreasing trend in showers/storms west to east during Mon as the
trough axis shifts to our east, with cooler high pressure building
in behind the surface low and frontal complex. Expect above normal
temps and good shower/storm chances Fri, especially east of Highway
1. Near normal temps Sat (cooler N than S) with low to no pops. Warm
SE and cool NW Sun with the approaching occluded strong storm
system, with a trend to likely pops for much of the area Sun into
Sun night, tapering west to east Mon with below normal highs. -GIH
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 840 PM Monday...
24 Hour TAF Period: The main area/broken line of showers and storms
is currently pushing eastward through the southern and eastern
portions of the area, currently affecting KRWI and soon to affect
KFAY. Brief gusty winds to 25 kts or so are possible with the main
outflow. Otherwise, MVFR/IFR cigs and/or visbys are expected with
the main band/line. Additional isolated to scattered showers will be
possible as the low level frontal zone moves through the area very
late this evening into early Tuesday morning. A period of at least 2-
4 hours of IFR cigs will be possible behind the main front. The
surface cold front is expected to push through SC into southern GA
on Tuesday. The latest NAM and GFS soundings, along with the HRRR
show drier air in the low levels now pushing into the area on Tuesday
morning with a return to VFR conditions at all sites by late
morning/early afternoon at the latest, with locations across the
north possibly VFR in the 08-12Z range. The latest hi-res models now
show dry weather expected for Tuesday as well.
Outlook: Aviation conditions are expected to deteriorate Tuesday
night as the low level boundary begins to lift northward, leading to
an increase in shower activity and lowering of ceilings back into
the MVFR/IFR range.
An unsettled weather pattern is expected Wednesday through Saturday.
This will lead to periods of sub VFR ceilings and visibility, along
with chances for showers and isolated thunderstorms. At this time,
the highest threat for adverse aviation conditions appear to be
Wednesday and Friday.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...WSS
NEAR TERM...CBL
SHORT TERM...WSS
LONG TERM...Hartfield
AVIATION...BSD/WSS
Area Forecast Discussion...UPDATED
National Weather Service Reno NV
600 PM PDT Mon Apr 17 2017
.UPDATE...
Deep moisture continues to stream into the Sierra, but the overall
pattern remains somewhat disorganized. That said, rain rates are
approaching 1/4" per hour and have increased amounts in the Tahoe
Basin and have also increased the precip threat there this
evening.
Further east, there is a bit of shadowing along the 395 corridor,
but lift increases along and east of a line from the Pah Rahs to
the Wassuks in Western Nevada. Rain is falling in Fallon and
Lovelock already. Radar trends show it increasing there and the
HRRR also keeps the rain going there through the evening. Updated
the rain chances there to near 100% this evening although amounts
will be light, around a tenth of an inch.
Otherwise, no more updates for now. We will continue to monitor
the precip rates and coverage to make any other adjustments later
this evening if necessary. Wallmann
&&
.SYNOPSIS...
Breezy conditions continue with the next weather disturbance
producing additional valley rainfall and higher elevation snowfall
tonight through Tuesday. After a final weak system Wednesday night
and Thursday, a drier trend with a significant warm up is expected
heading into the weekend.
&&
.PREVIOUS DISCUSSION... /Issued 236 PM PDT Mon Apr 17 2017/
SYNOPSIS...
Breezy conditions continue with the next weather disturbance
producing additional valley rainfall and higher elevation snowfall
tonight through Tuesday. After a final weak system Wednesday
night and Thursday, a drier trend with a significant warm up is
expected heading into the weekend.
SHORT TERM...
An upper disturbance off the central and northern California coast
will move into northeast California and Nevada late tonight.
Ahead of the main forcing, a brief period of warm air advection
rain is shown in simulations for this evening in west-central and
central Nevada (including Pershing and Churchill Counties) near
and north of a fairly subtle low-level boundary there. The
boundary can be evidenced per wave clouds, with the boundary near
the southern edge of the clouds in visible imagery.
Moving onto late tonight, the aforementioned upper disturbance
will move into the region. This is shown in simulations to tighten
up the low-mid level thermal gradient over western NV and the
northern Sierra, with precipitation breaking out along the
boundary as the main forcing arrives late tonight. Simulations
have zeroed in on the I-80/Highway 50 corridors or slightly
farther north for the best shot at heavier precipitation amounts
tonight, with between 0.10 and 0.25 inch certainly possible for
western and west-central NV through tonight (and a touch more
possible Tuesday morning). Confidence is high in this band of
precipitation developing tonight...but still medium on the exact
location of heavier precipitation.
As far as snow levels/Sierra impacts tonight and Tuesday morning,
this will be mainly a high elevation snow event. Currently, snow
levels are running from 7500 feet to about 9000 feet from Plumas
County to Mono County, respectively. The snow level should not
come down much through the bulk of tonight, with the upper wave
pushing most of the cold air into the Pacific Northwest. There
should eventually be a slow lowering of snow levels on Tuesday
morning to around Donner Summit/Pass level so there is a small
window where some slush could accumulate on I-80 over that pass.
However, it should melt off quickly by mid-morning. Farther north
into northeast CA, it does not look like snow levels will fall
quite far enough to impact higher roads there (including Highways
36 and 44 west of Susanville).
As the upper wave moves into Nevada on Tuesday, the boundary/front
will get a push south with precipitation expected to spread into
eastern Mono and Mineral Counties. The NAM and GFS even hint at
afternoon convection in the Basin and Range (east of Fernley) on
Tuesday, which could bring very small hail pellets and an isolated
lightning strike. While a couple small storms are possible
Tuesday afternoon, the probability remains too low to mention in
the forecast.
Tuesday night and Wednesday, brief drying moves into northeast CA
and western NV with temperatures on Wednesday rebounding to
around average. Snyder
LONG TERM...Wednesday night and beyond...
The last in a series of shortwaves is forecast to move quickly
through northern CA and northern NV Wednesday night and Thursday,
with the best potential for a short period of precipitation from
the late night through early morning hours. There will be some
cooling with snow levels likely dropping to 5500-6000 feet around
the Reno-Tahoe region, and near 5000 feet for northeast CA.
Moisture will be limited with current model QPF projections around
0.25 inch along the Sierra crest from Tahoe northward, with lesser
amounts near the crest in Alpine-Mono counties. For western NV,
the best chance for measurable rainfall will be from I-80 northward
with amounts 0.10 inch or less. Snowfall associated with this
system will generally be light, mainly 1-3" around Tahoe-Truckee
and northeast CA above 5000-5500 feet. Some slick/slushy travel
conditions are possible into Thursday morning around Tahoe (mainly
near or above 6500 feet) and higher elevation roads in northeast
CA (Fredonyer/Yuba passes and CA-44 west of Susanville).
For Thursday, lingering showers will taper off during the daytime
hours with brisk west to northwest winds keeping cool conditions
over the region. Choppy conditions are possible on Pyramid Lake
Thursday afternoon-early evening.
By Friday, a ridge of high pressure will build over CA-NV, leading
to dry conditions, lighter winds and a quick warmup with highs in
the mid-upper 60s for most lower elevations and 50s near the Sierra.
For the weekend into early next week, another trough moving quickly
across the Pacific Northwest will flatten the ridge a bit with some
increase in cloud cover mainly north of I-80 by late Saturday into
Sunday. Light rain showers are possible Sunday from Susanville-
Gerlach northward, but overall impacts on outdoor activities should
be minimal. Further warming is expected as temperatures will be
10-15 degrees above average each day, except slightly cooler north
of I-80 Sunday due to the weak trough passage. Moderate afternoon
and evening breezes are expected through Monday.
Looking ahead past Monday, a weak trough passage across the Great
Basin may bring a round of showers and some cooling Monday night
into Tuesday. This pattern of weak inland trough passages could
remain in place through much of next week, preventing a significant
warmup but precipitation amounts should be light. MJD
AVIATION...
For tonight into Tuesday, a stronger and wetter shortwave will
enhance precipitation with a continuous period of terrain
obscurement along the eastern Sierra and widespread MVFR conditions
for KTRK/KTVL, eventually spreading south to KMMH. Snow levels will
remain above Sierra terminals so snow accumulations are unlikely.
Western NV airports will see periods of light to occasionally
moderate rain with showers, but conditions should remain mostly
VFR with higher mountain tops possibly becoming obscured.
Tuesday afternoon, there is a low (10%) chance for thunderstorms
over west-central Nevada (well east of KRNO). If any storms form,
small hail (less than 1/2") and a few lightning strikes will be
possible.
Surface winds will be fairly modest through Tuesday (gusts 20-25
kts) but Sierra ridges will continue to have gusts 60-70 kts.
Some light to moderate turbulence will remain possible.
Hohmann/Snyder
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
521 PM MDT Mon Apr 17 2017
.SHORT TERM...(This Evening Through Tuesday Night)
Issued at 242 PM MDT Mon Apr 17 2017
Upper ridging across the region is giving way to a strong
shortwave cross the northern Rockies into central MT. A secondary
weak shortwave is pushing across northeast WY and approaching the
Black Hills. This secondary wave is bringing clouds to the area at
this time. Deep southerly low level flow continues across the CWA
with temperatures reaching into the 50s and 60s. Instability
across the Nebraska panhandle is sliding northward into southwest
SD. Models are showing SBCape values reaching 1500 j/kg over the
panhandle which will slide northward into southwest SD over the
next couple hours. The HRRR is showing storm development
associated with the weaker wave initiating in the late afternoon
hours over parts of northeast WY...then sliding eastward over the
southern Black Hills into southwest SD. There is enough shear for
one or two supercells to develop. The toughest hinderance to
storms will be the cap in place...but could see a few storms break
through as the wave crosses the area. Storms will move E/NE into
central SD this evening while a secondary area of showers develops
just ahead of the main wave across northwest SD and a surface
cool front pushing through. Upper ridging and dry weather will
return Tuesday behind the departing wave. Highs will be in the 60s
to low 70s...with the warmest spots across south central SD. A
broad upper trough will push into the western CONUS with a strong
upper wave across the Great Basin. This system will bring
increasing clouds late Tuesday...and chances for precip late
Tuesday night.
.LONG TERM...(Wednesday Through Monday)
Issued at 242 PM MDT Mon Apr 17 2017
Rain and showers will continue on Wednesday, with decent precip
amounts expected in some areas by the time the system exits
Wednesday evening. Models continue to show QPF amounts of close to
an inch or more. The 12z GFS shows some parts north of the Black
Hills reaching close to 2 inches. Some snow accumulation is
possible across the highest elevations of the Black Hills
Wednesday morning, but this would likely be limited to the highest
elevations where up to two or three inches of accumulation are
possible. Cool conditions on Wednesday, with highs in the 40s and
lower 50s. A brief break from pcpn is expected on Thursday before
the next system digs southeast from the Northern Rockies to the
Central Plains Thursday night and Friday. Models have continued
the northward trend. This system will bring rain to the
area...though the higher Black Hills could see another inch or two
of snow. Drier weather is then expected for the weekend as an
upper ridge builds across the region.
&&
.AVIATION...(For the 00Z TAFS Through 00Z Tuesday Evening)
Issued At 518 PM MDT Mon Apr 17 2017
Gusty southerly winds will shift to the west/northwest this
evening as a cold front moves through. Winds could gust to near 50
knots over NE WY along the front. Showers and thunderstorms will
develop and move from west to east across the area this evening
along the cold front, mainly from around the Black Hills NE. Local
MVFR/IFR conditions expected with the thunderstorms, along with
possible gusty winds and small hail.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&
$$
SHORT TERM...13
LONG TERM...13
AVIATION...JC