Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/30/17
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1158 PM EDT Sat Apr 29 2017
.AVIATION...
Late evening observations are helping answer the thunderstorm
question for the early morning hours. The mature convective complex
moving out of Indiana will move through most of the terminals by 08-
09Z with brief MVFR/IFR visibility restriction in heavy rainfall, and
then leave an unorganized pattern of weaker showers around through
sunrise.
Low pressure over Oklahoma will be moving northward and bring the
warm front closer to the Ohio border during the morning resulting in
MVFR ceiling with IFR becoming more likely along the DTW corridor.
Northward progress of the warm front will be disrupted by easterly
flow over the colder Great Lakes, especially while the primary
surface low is to the southwest. It may take until the occluded
frontal passage Sunday night before MVFR/IFR is swept out of SE
Michigan. In the meantime, low ceiling and reduced visibility in
showers/storms will be widespread over the region through Sunday.
For DTW... Thunderstorm timing and coverage is now pinned to the 05-
08Z period considering the storms nearby over Ohio and the line with
greater organization over Indiana. Visibility restriction with this
activity will be replaced by ceiling reduction during the morning.
Light to moderate northeast to east wind will persist through the
forecast.
//DTW THRESHOLD PROBABILITIES...
* High for ceiling 5000 ft or less tonight through Sunday.
* Moderate for thunderstorms tonight. Low Sunday afternoon.
&&
.PREV DISCUSSION...
Issued at 925 PM EDT Sat Apr 29 2017
UPDATE...
An increasing trend looks solid in both coverage and intensity of
showers and scattered storms during the evening and overnight hours,
matching up nicely with the flood watch valid time. Model analysis
fields indicate a strong warm front over southern Lower Michigan in
the 850-700 mb layer by measures of theta-e and thickness, supported
by the 00Z DTX sounding that shows the top of a sharp inversion
around 750 mb. Deep and strong southwest flow under the broad
160 kt anticyclonic upper jet is driving strong moisture
transport/theta-e advection and frontogenesis through the elevated
frontal zone. Recent radar composite also indicates an MCV organizing
within the mature convection over Illinois. This will only enhance
the low level jet that is already projected to be in the 40-50 kt
range at 850 mb through the night. Coverage in SE Michigan will be
more widespread toward the Tri Cities and a bit less in the Detroit
area. The widespread/categorical POPs in the north to likely/numerous
toward the Ohio border in the going forecast look good with no
adjustments needed. Plan to just add a few short term forecast
products to advertise coverage and strength trends during the night
that will likely include heavy downpours and possibly some small
hail.
PREV DISCUSSION...
Issued at 300 PM EDT Sat Apr 29 2017
DISCUSSION...
Cool/dry low level northeast flow mostly in control today as high
pressure translates through the northern Great Lakes, with a more
dominate center (1032-1033 MB) taking over Tonight over just south
of James Bay.
Deep surface based convection fired up along the Ohio River this
morning and was the focus of heavy rainfall during the morning
hours, cutting off moisture transport into the southern Great Lakes.
However, transport vectors quickly ramping up this afternoon/evening,
as wave ejects out of northern Missouri this afternoon, and and
still looking at ribbon of up to 5 C dew pts at 700 MB lifting
through southern Lower Michigan Tonight. Depending on the strength of
this wave/ripple, with have to watch locations close to the southern
Michigan border as showalter index reaches between -2 to -5 C,
depending on your model of choice, with HRRR showing stronger
convective reflectivity tracking along the border as well.
Fortunately, no concerns for surface based instability, and would
expect a sufficient stable surface-925 mb layer to prevent any
stronger wind gusts. Small hail will be possible however.
Rapid development/quicker spin up of the upper level low/circulation
over the Four Corners region earlier Today. Thus with the deeper
system and low level jet displaced a bit farther to the west, likely
assuring the better/prolonged 850-700 MB FGEN will be farther
northwest Tonight into Sunday, but still likely clipping Tri-Cities
region, where we have elected to issue a long duration flood watch
(added a few surrounding counties as a buffer as well). Local
Probabilistic SREF weighted guidance still projecting around 2
inches of total rainfall up that way by Monday Morning, with
potential for 3+ inches. Good chance of Flooding along Saginaw River
based on those amounts. PW values of 1.5 to 1.75 inches in place
Tomorrow will allow promote localized heavy rainfall farther south
with any vigorous convection/thunderstorms, but confidence is lower
in coverage/duration/locations. Still thinking the surface warm front
will not get much past the Michigan border, but could clear Lenawee
county, setting up very tight temp gradient along I-94 corridor and
points south, with high degree of 0-1 km bulk shear to work with if
any thunderstorm is able to latch onto this boundary. Outside of this
area, MUcapes of 500-1000 J/kg would just support small hail.
For high temperatures on Sunday, looks like a 30-35 degree
temperature difference from north to south, with highs in the upper
40s across northern Bay/Midland counties, to around 80 degrees late
in the day along the southern Michigan border.
The highest confidence in the most widespread rain showers is late
Sunday Night with the main upper level forcing/moisture axis and
cold front finally moving through, still looking to clear southeast
Michigan by Noon Monday. A very wet Monday morning commute, and
normally flood prone roads in Detroit Metro area could experience
problems with the high rainfall rates. Mid level dry slot taking
hold, with good low level cold advection from the southwest, as 850
mb temps tumble toward zero by day`s end.
Steep low level lapse rates and increased mixing depths, as well as
local probabilistic guidance suggest wind gusts of 40+ MPH by Sunset
Monday into Monday evening. Wind potential will obviously hinder on
how fast the low fills/weakens Monday afternoon-night as it lifts
through the Western Great Lakes.
Lingering isolated light rain showers will be possible throughout
Tuesday morning and afternoon as low pressure pushes northeast from
the Upper Peninsula into southern Quebec. As the low moves out of
the Great Lakes, a surface high pressure system is expected to build
in from the west, bringing relief from the rain late Tuesday into
Wednesday, as temperature daytime highs cap in the mid-50s for both
Tuesday and Wednesday.
Low to moderate confidence regarding rain potential starting
Thursday morning and continuing into the weekend. The latest 12Z
ECMWF model suite shows a low pressure system strengthening over
Kentucky/Indiana early Thursday, and pushes the low northeast over
Ohio by Friday morning, bringing the chance for rain showers across
Southeast Michigan as it moves northeast. The GEM model tries to
derive a similar low, however, the low pressure system remains weak
and keeps all precipitation just south of Michigan, similar to what
the GFS is resolving, albeit some slight timing and track
differences. As a result, PoP values will remain sub-30 until
convergences is seen exhibited future runs.
For the weekend, the GFS solution shows a nice omega blocking
pattern in the mid-levels which would be mild and dry conditions,
however, if the GEM and ECMWF solutions pan out, the potential for
dry conditions could be spoiled with isolated showers as both models
keep the 500 mb low over PA/NY, well northeast of the GFS run.
MARINE...
Unsettled conditions through early next week as a strong low
pressure system slowly tracks through the area. The approach of
this system will establish a long duration of moderate northeasterly
winds lasting through the latter half of the weekend. The
combination of gusty conditions and corresponding increase in wave
heights across the western lake Huron basin will lead to extended
small craft advisory conditions. Winds turn southerly and
strengthen throughout Monday in advance of a cold front. Potential
for gusts up to 30 knots from western Lake Erie to southern Lake
Huron during this time. Winds then become westerly with the frontal
passage on Tuesday. A wet and active pattern tonight through early
Monday, with periods of heavy rain and thunderstorms possible.
HYDROLOGY...
Several rounds of rain and possible thunderstorms are forecast to
lift across southeast Michigan between tonight and early Monday.
This rainfall could become heavy at times. Total rainfall through
Monday afternoon is expected to range between 1 and 3 inches, with
the highest amounts focused across the Saginaw Valley. Locally
higher totals will be possible for areas that experience
thunderstorms Sunday into Monday, as storms will bring brief periods
of torrential rainfall. Rivers and streams will see significant
rises through the middle of the week, and ponding of water may
develop in low-lying areas and roadways. Flooding could become a
concern by Sunday and Monday, particularly over the Saginaw Valley.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Flood Watch through Monday morning for MIZ047>049-053-054-060-061.
Lake Huron...Small Craft Advisory until 4 PM EDT Sunday for LHZ443.
Small Craft Advisory until 6 AM EDT Monday for LHZ421-422-441.
Small Craft Advisory from 4 AM to 4 PM EDT Sunday for LHZ442.
Lake St Clair...NONE.
Michigan waters of Lake Erie...Small Craft Advisory until 4 PM EDT Sunday for LEZ444.
&&
$$
AVIATION.....BT
UPDATE.......BT
DISCUSSION...SF/AM
MARINE.......MR
HYDROLOGY....MR
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Rapids MI
941 PM EDT Sat Apr 29 2017
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 329 PM EDT Sat Apr 29 2017
Showers and a few thunderstorms are expected over the course of
the weekend into early next week, well ahead an upper low that
will track to our west late Sunday into Monday. Chances for rain
will exist until the system rotates north through the midweek
period. Some of the rain could be heavy at times, especially in
and around thunderstorms late tonight into Sunday. Overall
rainfall amounts may lead to flooding along area rivers and in
flood prone areas into next week.
There is likely to be a wide spread in temperatures Sunday with
highs south of the front pushing toward 70 degrees. Otherwise,
below normal temperatures are expected until late next week, when
we moderate back into the 60s area wide.
&&
.UPDATE...
Issued at 935 PM EDT Sat Apr 29 2017
Seeing some 40 knot winds in the southern end of Lake MI. Latest
HRRR Ruc builds the stronger winds into parts of the NSH region
tonight for a few hours. Thus I upgraded the advisory to a warning
for these locations.
Will continue the Areal Flood Watch. Based on radar trends...I
wonder if we may not get as much rain with the first batch of
precipitation tonight. Still plenty of ingredients through the
remainder of the watch period to keep it going.
Latest HRRR Ruc is bringing the warm front up to the MI/IN border
tomorrow afternoon. Warm sector mixing winds are impressive.
Increased risk for severe weather here in MI if the front nudges
further north. Will need to monitor closely.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 329 PM EDT Sat Apr 29 2017
A good soaking rain is still on track to affect much of Lower
Michigan over the weekend. The heaviest rainfall is likely to fall
tonight into early Sunday and again Sunday night into Monday.
A warm front will continue to push north out of the Ohio Valley
tonight into Sunday. A mid-level wave will travel northeast along
the front in the overnight period. This feature will combine with
isentropic ascent and will be the focal point for ongoing
convection to track through the area. A few embedded thunderstorms
are possible with the high likelihood for thunder along and south
of I-96. Expect the first good wave of heavier rain to pass
through late this evening into early Sunday morning.
The upper level low continues to intensity through the day
Sunday. Plenty of support remains out ahead of the low thanks in
part to a coupled upper jet that will be in place over western
Lake Superior. Moisture transport remains strong out of the gulf
with PWATs persistently in the 1.2-1.8 inch range. A broad
surface low continues to be guided just west of Lake Michigan.
This will be our second good wave of moisture with the core of
the lift moving through Sunday evening into the early morning
hours Monday.
While the low continues to rotate northward through the day
Monday, a few rain showers will linger with a couple of weak
upper wave rotating around the out edge of the main circulation.
Precipitation will be light and scattered in the nature. Expect a
pretty damp, cool start to the work week.
.LONG TERM...(Tuesday through Saturday)
Issued at 329 PM EDT Sat Apr 29 2017
A well needed drying out period should be seen through much of the
long term. Temps will be cool, but we should see a slow moderation
during the latter half of the week.
The upper low is expected to be moving northeast across the Superior
region and toward Quebec on Tuesday. As it departs, the showers
will continue to become more scattered. Most areas probably won`t
begin to dry out until Tuesday afternoon or into the evening. It
does appear we will partially clear Tuesday night, and with
diminishing winds, some areas of frost will be possible with temps
dropping into the 30s. I have added this to the forecast, however
impacts are still expected to be low given the time of year.
The core of the coldest air behind the system slowly moves east,
leading to a slow but gradual warming trend by Wednesday night and
continuing into next weekend. After highs only around 50; 10 to 15
degrees below normal on Tuesday, we will warm to closer to normal
temps by Saturday, in the 60s.
A well needed dry spell should be in the offering starting Tuesday
night. A short wave is shown to come through Thursday night, while
low pressure is expected to be over the Gulf Coast states. The upper
wave should act to pull the surface low northeast into the OH/TN
valley. So there could be some isolated light showers over the SE
CWA late Wednesday night through Thursday night. Otherwise much of
the Tuesday night through Saturday period appears dry.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 741 PM EDT Sat Apr 29 2017
Aviation conditions are forecasted to lower through the evening as
the warm front approaches from the south. Showers and
thunderstorms will be spreading in. The heavier downpours will be
capable of lowering visibilities to under 2 miles...mainly after
04z. Ceilings will be lowering as well...with IFR conditions
likely...especially after midnight and through much of Sunday.
The rain will come in several waves. One tonight...then perhaps a
break during part of Sunday. Additional rounds of showers and
thunderstorms will arrive as the day progresses. Aviators will
need to monitor the latest forecasts as impacts are expected.
&&
.MARINE...
Issued at 329 PM EDT Sat Apr 29 2017
The small craft advisory will continue as planned. Waves will
generally range from 2-4 feet in most instances with offshore flow
up to around 25 knots. Periodic episodes of waves in the 3-5 feet
range will occur, specially near the points (Ludington/Manistee).
The bigger concern will be in the later half of Monday when winds
shift out of the south and southwest. Higher waves are likely with
an onshore flow. Waves of 3-5+ will become more persistent through
Monday night. The advisory may need to be extended or reissued for
late Monday in later updates.
&&
.HYDROLOGY...
Issued at 122 PM EDT Sat Apr 29 2017
Flood advisories continue for the Grand River at Ionia and on the
Maple River at Maple Rapids. A flood watch continues for the same
four points. River statements have been issued for numerous
locations that might experience flooding towards the middle of the
coming week. However, forecast certainty for these sites remains
very low at due to high dependence on the character of precipitation
that occurs over the next 48 hours and how well the models handle
the subsequent river crests.
It is quite certain, however, that widespread rainfall affecting all
area river basins will fall between now and Monday morning. The
latest round of river forecasts were based on 48 hour WPC QPF, which
is slightly greater and shifted farther north than WFO QPF. SREF
guidance shows mean values around 2", although there are a couple
outliers with 4+", making the median QPF a little bit below 2".
Interestingly, downscaled calibrated GEFS output shows only a 40-50%
chance of exceeding 2 inches in most spots. However, we favor the
ECE, whose ensemble members show strong consensus squarely in the 2-
3" total QPF range, in line with previous thinking. As noted
already, local maxima in precipitation are likely but there is
little predictability with exactly where they will occur. This of
course has potentially significant implications with what river
basins are most affected.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Flood Watch through Monday morning for MIZ043>046-050>052-
056>059-064>066-071-072.
LM...Small Craft Advisory until 11 AM EDT Monday for LMZ848-849.
Small Craft Advisory from 8 AM Sunday to 11 AM EDT Monday for
LMZ844>847.
Gale Warning until 8 AM EDT Sunday for LMZ844>847.
&&
$$
UPDATE...MJS
SYNOPSIS...JAM
SHORT TERM...JAM
LONG TERM...JK
AVIATION...MJS
HYDROLOGY...TJT
MARINE...JAM
Area Forecast Discussion
National Weather Service Houston/Galveston TX
950 PM CDT Sat Apr 29 2017
.UPDATE...
The rapid southeasterly advance of the cold front is certainly
doing a number on the (potential) convection this evening as it
undercuts the line. The boundary has passed across College Station
at the bottom of the 8 PM hour with 9 PM pressure rises and a
stout NW 20 mph wind gusting to over 30 mph. Will give it another
20 minutes or so and then...if activity doesn`t blossom up...will
be paring back/canceling the Severe Watch at 10 PM (an hour early).
Per a recent UH sounding...the downstream is pretty capped between
7-850 mb so am not anticipating much more than the passage of
light showers between 10 and Midnight over metro...the front
should be clearing the coast between 8 to 9Z per recent 01Z HRRR
run. Breezy northwesterlies under early Sunday clearing skies...
becoming mainly clear by early afternoon. Afternoon temperatures
will slowly warm into the average middle 70s as lower level cold
advection continues through sunset. Surface high moves over
tomorrow night...weakens Sunday night/Monday morning variable
winds to near calm. Overnight resident dry air mass with dew
points in the 40s equates to Monday morning interior minTs in the
upper 40s to lower 50s...low to mid 60s along coast. 31
&&
PREV DISCUSSION... /ISSUED 706 PM CDT Sat Apr 29 2017/
.Severe Thunderstorm Watch is in effect for the northwestern
CWA through 11 PM tonight...
A Severe Thunderstorm Watch is in effect for the northwestern
forecast area through 11 PM. The main threats in association with
the approaching cold front will be damaging thunderstorm winds
and hail. The strongest convection is expected to begin moving (or
developing) across the extreme northwestern counties from around
9 PM and be across the majority of the northern counties...possibly
moving into the east-southeast CWA...before midnight. 31
&&
PREV DISCUSSION... /ISSUED 636 PM CDT Sat Apr 29 2017/
AVIATION...
Really not many changes to the ongoing TAFS other than to slightly
tweak timing of, what`s expected to be, a thin line of shra/tstms
that`ll be moving thru SE Tx later this evening and overnight
ahead of a cold front. Southerly winds should remain gusty into
the evening hours then gradually taper off ahead of the front.
Improving aviation conditions in its wake on Sunday. 47
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 58 74 50 84 60 / 90 10 0 0 0
Houston (IAH) 63 77 54 84 63 / 80 10 0 0 0
Galveston (GLS) 66 75 65 79 71 / 80 20 0 0 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Coastal Flood Advisory until 7 AM CDT Sunday for the following
zones: Brazoria...Chambers...Galveston...Matagorda.
GM...Small Craft Advisory until 2 PM CDT Sunday 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...Galveston Bay...Matagorda Bay...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...31
Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
728 PM CDT Sat Apr 29 2017
.NEAR TERM...(Tonight)
Issued at 722 PM CDT Sat Apr 29 2017
Regional radar imagery shows isolated convection still ongoing across
portions of northern Georgia and middle/eastern Tennessee early this
evening. Across our area, the earlier shower/thunderstorms
development has either dissipated or lifted to the north leaving
mostly clear skies in its wake. Looking at the soundings from the RAP
indicates a fairly unstable airmass, though with the loss of daytime
heating and no discernible trigger expect a fairly quiet remainder
of the evening.
We are monitoring a couple of small convective clusters/complexes
that have not been handled that well by the high res models today.
One was located across the MS Delta Region with another across
southern Louisiana. The mean flow should keep this activity west of
our region tonight but it may have some impact on the evolution and
timing of the line moving across on Sunday.
For the overnight, have not made too many changes overall. Have made
some minor tweak to the cloud cover based on the IR/VIS trends and
also adjusted the temps based on current trends and the shortblend
guidance. No other changes planned.
.SHORT TERM...(Sunday through Monday)
Issued at 300 PM CDT Sat Apr 29 2017
Current satellite imagery shows a mesoscale convective complex
developing over northern Louisiana. This is south of the main frontal
boundary over Oklahoma northeast into Missouri and northern Indiana.
As this front develops and pushes slowly east toward the Tennessee
Valley, this may affect the evolution of the pre-frontal trough axis
on Sunday and how far east it initially develops. Most synoptic
operational models do not show this feature, including the NAM12.
These operational models hold off shower and thunderstorm activity
with the prefrontal trough axis until between 4 PM and 8 PM in
northwestern Alabama and continue this activity through the overnight
hours. However, after midnight with lessening instability the severe
storms do not look as likely east of I-65. Either way the timing
works out, the threats remain similar to previous forecasts. The main
threat will be damaging winds. A tornado or two cannot be ruled out
(mainly west of I-65). Heavy rainfall between 1 and 2 inches with
locally higher amount up to 3 inches look possible given strong
forcing and high instability. A few showers could linger into Monday
as drier and cooler air moves into the region.
.LONG TERM...(Monday night through Friday)
Issued at 300 PM CDT Sat Apr 29 2017
The cold front responsible for much of the active wx ending
the weekend period should be well e of the TN Valley into
the Atlantic Basin going into Tue, as high pressure out of the
srn Plains quickly works its way into the SE region. Other than
perhaps a brief shot of cooler/drier air during the first half
of the new work week, little relief in overall temps is xpcted with
this frontal passage thru mid week, as the low level wind field veers
back to the se/s and the flow pattern aloft turns more toward the
wsw. Afternoon temps both Tue/Wed look to return close to 80F, as
another upper trough pattern drops well into the srn Plains states.
Unfortunately, there is a large disconnect with the progression of
this upper trough axis and its associated sfc wave between the latest
12Z guidance and the previous 00Z model runs. The latest model suites
are now hinting at a more vigorous upper low/trough system gradually
traversing enewd into the wrn/cntrl Gulf states for the second half
of the work week, compared to the faster 00z solutions. This scenario
does at least maintain showers/tstms developing Wed/Thu, as the
initial sfc wave and its associated cold front translate ewd across
the cntrl TN Valley. However, the prob may now exists for secondary
sfc waves to develop along the upper low/trough axis lingering back
to the w. This now results in iso/sct showers into Fri as the upper
low/trough gradually moves ewd across the cntrl Gulf region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 635 PM CDT Sat Apr 29 2017
VFR conditions should continue through the evening and much of the
overnight hours as the area remains sandwiched between a high off the
southeast US coast and a strengthening system across the Southern
Plains. The pressure gradient between the two systems will keep
rather stout southerly winds through the TAF period, and have made
only minor changes to the previous issuance.
Conditions will be marginal for LLWS at both sites late tonight into
early Sunday but did not include at this time. Will monitor trends
before next TAF issuance. Expect a fairly quick influx of low clouds
due to isentropic upglide and warm advection toward morning with a
period of MVFR ceilings likely. For the time being, we capped the
maximum gusts at each site at 30 knots though a few higher gusts are
likely given the tightening gradient. Model guidance has some notable
discrepancies with the timing of the approaching line/convection
Sunday afternoon so only included Prob40 for the time being.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Wind Advisory from 10 AM to 10 PM CDT Sunday for ALZ001>010-016.
TN...Wind Advisory from 10 AM to 10 PM CDT Sunday for TNZ076-096-097.
&&
$$
NEAR TERM...15
SHORT TERM...KTW
LONG TERM...99
AVIATION...15
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Wilmington NC
959 PM EDT Sat Apr 29 2017
.SYNOPSIS...
High pressure will extend across the area from offshore through
early Monday with warm and humid conditions continuing. A cold
front will bring a likelihood of showers and thunderstorms late
Monday into early Tuesday. High pressure will follow for the
mid-week period. A Low pressure system will impact the region
Thursday into Friday amd may bring widespread showers and
thunderstorms and heavy rain.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 1000 PM Saturday...Short-term guidance is converging on
the idea of fewer low clouds developing overnight. This may be
due to dewpoints, while still running exceptionally high for
this time of year, are just not high enough relative to the
warmth of the airmass to ensure a good saturated layer develops.
Latest HRRR and GFS-LAMP guidance still shows 1000-2000 foot
stratus inland, but only for a few hours late tonight. I have
trimmed back this potential in the latest sky cover forecast and
tweaked a few temperatures with somewhat more clear skies
anticipated. Discussion from 730 PM follows...
Very few changes were needed to the previous forecast. An
exceptionally humid and warm airmass for this early in the
season will continue to spread onshore tonight. Temperatures
should run a solid 15 degrees above normal with low temps around
70 degrees. Dewpoints will remain in the 60s and lower 70s.
Much like we saw last night, low stratocumulus clouds should
develop and persist through daybreak Sunday. We`re already
seeing some cloudiness develop now in the Cape Fear area,
probably an early sign of what will come. Between 10 PM and 1 AM
expect skies to become cloudy to mostly cloudy area-wide except
perhaps right on the beaches as these clouds will be the result
of humid air lifted up over the shallow nocturnal inversion
near the coast.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 315 PM Saturday...Strong mid level ridging which has been
responsible for the summer like conditions of the past few days
will give way to a dampening cyclone moving from the Central
U.S. to the Great Lakes region through the period. At the
surface, Bermuda High pressure will be displaced by a cold front
moving across the area late Monday into early Tuesday. The
timing of the front is becoming more consistent within the
guidance suite and there should be a broken to almost solid line
of showers and thunderstorms moving west to east across the
area from about 0 to 6z Tuesday. Severe potential doesn`t look
overly impressive with 850mb winds only 45-50 knots with the
higher values to the north. Still, the timing could make things
a bit interesting over the western zones early in the evening.
Warm temperatures continue with highs in the 80s monday
following another night with lows in the 60s Monday morning.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 315 PM Saturday...Broad high pressure behind Monday night`s
cold front will expand across the Southeast Tuesday creating dry and
seasonable weather with highs and lows right around climo.
This high will remain in place Wednesday with slightly warmer
temperatures but continued dry weather before it shifts offshore
Thursday. This occurs in response to a deep mid-level trough digging
into the middle of the country and then evolving across the eastern
CONUS into the weekend.
There exist two distinct camps in the guidance: the GFS has this low
cutting off and dropping southeast through the end of the period.
The CMC/ECM have a similar pattern initially to the GFS, but the
upper low drifts north before cutting off overhead the Northeast.
The biggest difference between the guidance appears to be the
evolution of the ridge across the middle of the country. The CMC/ECM
keep the ridge axis aligned N/S, while the GFS produces a more
tilted NE/SW ridge which suppresses the upper low. The agreement
between the ECM/CMC tends to favor that solution a bit more, despite
the fact that the GFS has been consistent and we had a similar setup
just last week so there is precedent. The evolution of this upper
pattern is critical because, while all scenarios support showers and
thunderstorms late Thursday and Friday, the CMC/ECM would dry things
out for the weekend, while the GFS would maintain unsettled and
possibly very wet weather for several days. Without a clear solution
at this time range, will hedge with a WPC favored blend of guidance
but with a bit more weight on the drier ECM by the weekend. This
would also bring much cooler temperatures to the region Fri/Sat with
highs and lows falling below climo.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
An unseasonably humid airmass will probably produce widespread
stratus overnight with cloud ceilings in the 1000-2000 foot AGL
range. Although IFR ceilings cannot be ruled out, surface
dewpoints are 1-2 degrees lower than at this same time yesterday
both on land and at the offshore buoys where our air is blowing
in from. Confidence is moderate that we will see stratus
develop overnight, however the time given in the TAFs for the
development for the clouds has only low confidence. Model
consensus of low cloud development has actually diverged in the
past couple hours, trending later in the night. Any stratus
lingering after sunrise Sunday should lift above 2000 feet AGL
around 14Z.
Extended outlook...Periods of IFR/MVFR conditions are possible
in showers and thunderstorms late Monday into early Tuesday.
&&
.MARINE...
NEAR TERM /THROUGH SUNDAY/...
As of 1000 PM Saturday...High pressure well offshore will
maintain a southerly wind tonight around 10 knots. Stronger
winds this afternoon along the coast were the result of the
seabreeze, which produced gusts over 20 knots at times. Seas
around 3 feet should continue overnight in a mix of 5-second
wind waves and 8 second SE swell.
SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 315 PM Saturday...A southerly flow will be in place most of the
period with wind speeds increasing Monday as a cold front approaches
from the west. Initial speeds of 10-15 knots will increase to a
respectable 20-25 knots late Monday and persist into the evening
hours. The front will move across with a modest westerly flow
setting up by early Tuesday. Small craft conditions are likely
for Monday. Significant seas will ramp up as well increasing
from 2-4 feet early to 5-8 feet late.
LONG TERM /TUESDAY THROUGH THURSDAY/...
As of 315 PM Saturday...Broad high pressure builds across the waters
behind a cold front Tuesday. Residual gusty W/NW winds of 15 kts and
4-6 ft seas will fall quickly during Tuesday as winds back to the SW
at 10-15 kts late Tuesday before a secondary surge flips winds
around to the NW by Wednesday at less than 10 kts. As the high
shifts offshore into Thursday, southerly winds will ramp up quickly
becoming 15-25 kts, driving seas back to 4-7 ft after being just 2-3
ft much of Wednesday. An SCA will likely be needed beginning late in
the extended.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...Coastal Flood Advisory until 3 AM EDT Sunday for NCZ107.
MARINE...None.
&&
$$
SYNOPSIS...SHK
NEAR TERM...TRA
SHORT TERM...SHK
LONG TERM...JDW
AVIATION...TRA
Area Forecast Discussion
National Weather Service Indianapolis IN
1025 PM EDT Sat Apr 29 2017
.UPDATE...
The NEAR TERM and AVIATION Sections have been updated below.
&&
.SYNOPSIS...
Issued at 320 PM EDT Sat Apr 29 2017
A stationary front will lift north across central Indiana tonight.
Then, a strong cold front will sweep east across the area Sunday
night. Copious amounts of moisture, along with strong lift and
instability, will result in numerous thunderstorms over central
Indiana through Sunday night. Heavy rain and flooding will continue
to be a threat. Severe weather is also possible.
A few showers will linger into Monday in the wake of the cold front.
Then, high pressure will bring dry and cool weather to the area
Tuesday. Showers will return midweek courtesy of a southern system.
Finally, next weekend looks dry and continued cool under high
pressure.
&&
.NEAR TERM /Tonight/...
Issued at 1025 PM EDT Sat Apr 29 2017
...Evening Update...
Long lived squall line that tracked out of the mid Mississippi
Valley has moved into west central indiana this evening...gradually
weakening in intensity. However the return of a nocturnal low level
jet from the southwest this evening has generated rapid convective
development in the vicinity of the warm front laid out from near
KHUF E/SE to just south of the Indy metro.
While a localized severe threat may linger for the next hour or
two...the focus is already rapidly transitioning to heavy rain and
flooding as the big impacts going forward into the overnight. The
new convection is developing and aligning in tandem to the direction
of the low level jet from southwest to northeast...and becoming
increasingly suggestive of the potential for cells to train. Already
seeing that occur with cells west of the Indy metro where doppler
estimates approaching 2 inches in under an hour are already being
detected in Putnam and Owen Counties. With all the rain that has
already fallen since Friday...flash flooding is a major concern into
the overnight...especially across the western half of the forecast
area.
Afternoon discussion follows.
The stationary front should start lifting slowly northward late this
afternoon, in part due to the decrease in coverage of convection, as
the low level jet has weakened and moved off to the east. The front
was extending northeastward along the Ohio River valley from a low
pressure center over east central Oklahoma. Meanwhile, an upper low
was pivoting southeast over central New Mexico.
Models are pretty consistent in moving the upper low to southwestern
Kansas and the surface low to east central Kansas by 12z Sunday. As
the surface low lifts northward, it should drag the warm front to
near Lafayette and Kokomo by Sunday daybreak.
All but areas northeast of Lafayette and New Castle are in a Slight
Risk for severe weather late this afternoon and tonight. This seems
reasonable as CAPES have been creeping up south of Indianapolis.
Also, 40 plus knot low level jet will migrate into our west central
counties this evening and overnight which will provide more fuel for
thunderstorm development. In addition, the High Resolution Rapid
Refresh suggests there will be a few storms around this evening with
increased coverage overnight, mainly west central within low level
jet and deep moisture transport. The HRRR has handled the shower
evolution very well this morning. So, will follow it closely and
stick with high pops there, especially overnight and taper to chance
pops southeast. With record precipitable water amounts for this time
of year, above 1.75 inches, and good dynamics and instability, heavy
rain will be a possibility once again tonight. The main severe
threats will be damaging winds and large hail. All of central
Indiana is in a Slight Risk for excessive rainfall tonight.
Blend temperatures look ok overnight with little drop expected.
&&
.SHORT TERM /Sunday through Tuesday/...
Issued at 320 PM EDT Sat Apr 29 2017
Main focus for the short term will be on timing and coverage of more
heavy rain producing thunderstorms.
Models in good agreement that a low pressure system will lift from
Kansas to northern Iowa by 12z Monday and to just north of Sault
Ste. Marie by 12z Tuesday. As the system moves northeast, it will
drag a strong cold front across central Indiana Sunday night. Ahead
of this system, record deep moisture will advect northward over the
area via a 50 plus knot low level jet. Precipitable water values
will be above 1.75 inches, which continues to exceed the max moving
line at ILX and ILN for late April. There was also be sufficient
instability with CAPES 400-800 j/kg and deep uni-directional shear.
So, there could be some damaging winds and possibly large hail per
the SPC Day2 Marginal Risk of severe weather. There will be
thunderstorm chances all day Sunday with upper impulses moving
through the fast southwest flow, but the best chance will be Sunday
late morning through Sunday night with cat pops needed. Potential
for another inch or more on top of saturated soil warrants a Flash
Flood Watch for all of central Indiana through 8 am Monday. 1 hour
Flash Flood Guidance of slightly more than half an inch supports
starting the Watch off at 00z tonight rather than later.
Could see a few instability showers Monday and Monday evening in
cyclonic flow behind the cold front, otherwise it will be much
cooler behind the cold front with sunshine returning by Tuesday. MOS
blend looks to capture this with pre-frontal highs Sunday in the
upper 70s to mid 80s and below normal post-frontal highs only in the
upper 50s to mid 60s Monday and Tuesday.
&&
.LONG TERM /Tuesday Night Through Saturday/...
Issued at 214 PM EDT Sat Apr 29 2017
Highly variable model solutions lead to low confidence, so the model
blend initialization was accepted.
Models continue to have different solutions on how an upper level
system will develop during the long term, including individual model
variability from run to run.
Thus as noted above, confidence is low. Left the initialization
alone which leads to some PoPs for several periods during the long
term.
Temperatures will remain below average. (Some models have highs
nearly 20 degrees below average at times.)
&&
.AVIATION /Discussion for 300300Z TAF Update/...
Issued at 1025 PM EDT Sat Apr 29 2017
Made adjustments to account for convection approaching KIND and KBMG
currently. This activity will cause restrictions over the next
couple of hours. Also adjusted wind direction at both KIND and KHUF
as the warm front appears to have slipped just back south of both
terminals. Still expecting the front to lift back north later in the
overnight. Otherwise...forecasts are in decent shape.
00Z discussion follows.
Poor flying conditions expected within rain and storms otherwise
VFR conditions are likely into Sunday.
The warm front has shifted north of Interstate 70 as of 23Z with
surface flow from the SE to the south of the boundary and E/NE to
the north. The boundary is expected to shift north towards the
northern part of the forecast area overnight as a robust line of
convection tracks along the front through Illinois and into parts
of central Indiana after 00Z. Main impacts along the line likely
to be felt at KHUF and KLAF by 01-0130Z with potential impacts at
KIND and even KBMG later in the evening. A brief period of strong
winds will likely accompany the convective line along with
blinding rain and sub-IFR conditions. Will hit this harder at KHUF
and KLAF where confidence is highest in impacts this evening.
As the night continues...the convective line will weaken but
overall coverage to rain and convection should expand across the
northwest half of central Indiana with a strengthening low level
jet moving into the region. Storms should once again diminish in
coverage by late morning/midday Sunday as the low level jet
weakens and the warm front lifts into northern Indiana. Renewed
storm development is expected during the afternoon and evening
Sunday as strong low pressure and a cold front approaches from the
west. Winds will veer to southerly for all but KLAF on Sunday.
There the nearby presence of the front will keep flow backed along
with lower ceilings at or below 2000ft into Sunday morning with
S/SE flow developing as the day progresses and the front lifts
north.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Monday morning for INZ021-028>031-
035>049-051>057-060>065-067>072.
&&
$$
SYNOPSIS...MK
NEAR TERM...MK
SHORT TERM...MK
LONG TERM....50
AVIATION...Ryan
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
627 PM CDT Sat Apr 29 2017
.MESOSCALE DISCUSSION...
610 PM CDT
Early this evening, regional radar composite showed a well
defined MCV over central IL enhancing a region of warm air
advection driven rain over about the NW 2/3rd of our CWA.
An area of moderate to nearly heavy rain extends from Peoria to
Lacon then northeast across LaSalle, southern DeKalb, southern
Kane, Grundy, and Kendall counties, beginning to spread into
heart of Chicago metro area. Rainfall rates of 0.2 to 0.4" per
hour have been observed in this area.
Over the next several hours anticipate this MCV to continue
tracking ENE toward our extreme southeast CWA. Intense line of
convection across central IL will continue to lift northeast and
could clip our southeastern most counties. While it would be well
north of the warm front, it is possible that some strong winds
could penetrate through the stable boundary layer with this line,
as has already been observed in central IL. Better severe threat
should remain south of our area however.
In addition, the area of moderate to heavy rain should continue
spreading northeast across the heart of the Chicago metro area.
There will probably be a maximum swath of an inch to possibly as
much as an inch and a half of rain with this first wave through
early this evening from LaSalle County ENE into Chicago. Radar and
satellite trends suggest that in the wake of this MCV we will see
a dramatic decrease in precip intensity or precip ending
altogether for a potentially extended period of time.
This MCV and associated squall line to it south will re-enforce
the synoptic front well south of our area and should focus
convective develop later this evening and overnight well south of
our CWA. Will work on re-fining pop/qpf/wx grids to reflect these
anticipated trends. Flooding threat with this first wave expected
to be low, but it will prime things if any additional heavy rain
falls Sunday.
- Izzi
&&
.SHORT TERM...
237 PM CDT
Through Tonight...
Overall, will continue the flash flood watch as heavy rain is
possible this evening. The precip doesn`t look like it will evolve
as I imagined yesterday, but we are still looking at a lot of rain
over the next 48 hours that will result in river flooding and
some areal flooding.
The surface low is forming over Texas and its warm front lies from
central Missouri through central Indiana. The front will lift over
our far southern counties by Sunday morning. Showers have blossomed
nicely across the forecast area, and it seems like the majority of
convective activity will occur south of I-80 especially where rain
has briefly ended. Still have at least a slight chance of
thunderstorms across the region though as embedded thunder is
possible.
Followed the HRRR and NAMNest guidance that feature a line of
convective showers/storms forming from Rockford south over the next
couple of hours and then marching east. This convective line should
produce the most precip tonight and raised QPF values slightly. Have
0.5 to 1.0 inches of rain between 00 and 06Z Sunday. However, we
could see a break in precip or just light showers/drizzle after the
line. Lowered precip chances to likely behind the line because I did
not have enough confidence to go with straight drizzle. Lowered QPF
using a blend of the previous forecast and GFS between 06 and 12Z
Sunday.
Temperatures are also a bit tricky. Temps will continue to fall over
the northwestern half of the CWA while temps will warm over the
southeast CWA. That temp trend should continue into this evening.
Then temps over the northwest will hold steady or warm slightly in
the low 40s. Temps over the southeast will also hold steady around
50 or in the low 50s.
JEE
&&
.LONG TERM...
302 PM CDT
Sunday through Saturday...
The challenging forecast continues through the end of the weekend,
with the closed low deepening across the central Plains Sunday and
moving northeast Sunday night. As the system matures, the warm
and moist conveyor belts will be spreading over the region, but
similar to this morning, ample ongoing storms are favored to our
south. This will be in response to constant storm development
modulating the primary effective surface warm front and keeping
it over Missouri and southern Illinois into Sunday a.m. The
effects of the robbed moisture transport may temper rainfall in
the a.m. into early p.m. hours.
Guidance continues to show spread in boundary placement and QPF
magnitudes through the rest of Sunday. The main surface low is
presently favored to be a little east of Kansas City and at around
994mb by mid-afternoon. A secondary low/triple point is favored
to be somewhere near the Mississippi River/western Illinois by
late afternoon as the system dry slot moves in. The northward
progression of this surface feature will be affected by just how
widespread convection and its cooling footprint is through the
day. In addition, there is favored to be convective development
further south along the cold front across the lower Mississippi
Valley. These will be inhibiting factors to at least some degree
of warm air and instability return north of the boundary for
convection. In the presence of 0-6km shear at or above 60 kt, a
conditional threat for quick-moving, mainly low-topped supercells
and severe weather will exist if enough low-level CAPE can track
northward. This looks to be more so over the southeast CWA though
some storms are certainly possible areawide on the nose of the dry
slot given the strong low-level convergence. Overall have been
leaning a little more toward the high-res NAM-WRF and a further
south placement of the most effective air, but will need to
monitor closely.
Overall clusters of showers and some storms in the afternoon
into the early evening are expected, and continued moderate to
briefly heavy rainfall rates are likely. Progression of
showers/storms will be fairly quick Sunday afternoon and evening,
so that may ease the true flash flooding threat with more of an
areal flooding concern due to the overall wet 30-36 hour period
from this afternoon through Sunday evening. While the dry slot
should bring much of the rain threat to an end by late Sunday
evening, have continued the watch end time as is given that any
flooding would persist after the rain.
Sunday temperatures are tricky. The northern CWA is likely to
remain within northeast/east winds the longest amount of time,
and should not climb out of the 40s most of the day if at all.
Temperatures will be on the climb south, but how quickly and how
far north the warm air reaches will again depend on the primary
warm front. Have highs in the lower 70s forecast in the far
southeast but these could extend further north, even up to the
southern Chicago metro especially based on global guidance
solutions. Behind the cold front Sunday evening winds will turn
southwest and breezy.
The surface low is expected to only slowly occlude into Monday,
with fairly stout cold advection pegged into the CWA on southwest
to west winds gusting to 35 mph or so wrapping around the system.
With low-level clouds favored, especially north and west CWA,
temperatures may not go anywhere on Monday. Have collaborated and
undercut some on guidance, but could be too warm in northern
locations. How far rain showers extend south and east on the
commahead of the system will depend on how quickly it moves
northeast, but do have likely mention in northwest locations.
Beyond, high pressure will generally prevail much of the rest of
the workweek on global guidance solutions. There could be a frost
threat Tuesday night in outlying areas.
MTF
&&
.AVIATION...
For the 00Z TAFs...
Primary aviation concerns are with thunder especially across
southern parts of Chicago metro area early this evening, IFR
ceilings through the period, and gusty northeast-east winds to
30 kts this evening.
Well-defined MCV and surface low pressure reflection was across
central IL early this evening, with an area of enhanced rainfall
and embedded thunderstorms across much of northern IL. This will
continue to affect the terminals through the early-mid evening
hours before this feature tracks east of the area and allows
precip to diminish to drizzle/light rain overnight. Ceilings have
steadily lowered from VFR to IFR as rain has moistened our cool
low-level air mass, and guidance strongly suggests IFR ceilings
will linger through much of the TAF period. High-res convective
allowing models depict another batch of showery precip develops
across the area early Sunday morning, with deeper convection and
thunderstorms developing in the afternoon and evening hours ahead
of an approaching strengthening low pressure center.
Gusty northeast winds to 30 kts expected this evening, likely
veering from 020-040 to more 040-060 with time overnight. East to
northeast winds persist Sunday north of the system warm front,
though will likely see some veering to more SE late in the day as
the low approaches and the front lifts across the region.
Ratzer
&&
.MARINE...
237 PM CDT
Headlines...Will go with a gale warning for the south half and
nearshore waters this afternoon through most of tonight. While gales
will subside, small craft conditions will likely continue through
Sunday. Gales are then expected over the northern half of the lake
Sunday afternoon and night, and upgraded the previous gale watch to
a warning.
A weak high is over western Ontario and the western Great Lakes
while a low is forming over Texas. The tightened pressure gradient
will keep northeast winds at 30 kt and they will increase to 35 kt
gales over the south half late this afternoon. Both the low over
Texas and the high over Ontario will lift north through Monday and
gales will form over the northern half of the lake Sunday afternoon.
The low will pass over the western Great Lakes Monday night and
reach Quebec Tuesday. The low`s cold front swings through late
Monday night/early Tuesday morning. Southwest to west winds may
increase to gales over the southern half Monday night into Tuesday.
High pressure moves over the lake Wednesday and then shifts
southeast of the lake late in the week.
JEE
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Flash Flood Watch...ILZ014-ILZ021-ILZ022-ILZ023-ILZ032-ILZ033-
ILZ039 until 7 AM Monday.
IN...Flash Flood Watch...INZ001-INZ002-INZ010-INZ011-INZ019 until 7
AM Monday.
LM...Gale Warning...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
LMZ779 until 4 AM Sunday.
Small Craft Advisory...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...4 AM Sunday to 4 PM Sunday.
&&
$$
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Area Forecast Discussion
National Weather Service Melbourne FL
846 PM EDT Sat Apr 29 2017
...A FEW SPOTTY COASTAL SHOWERS THIS EVENING...
.UPDATE...
Main update tonight is for modest upward nudging of POPs for
isolated showers (15-20 percent) from Melbourne to Fort Pierce as
a consequence of onshore moving convection. Looks to be wake
convergence WNW of Grand Bahama and Great Abaco. HRRR hinted at
this but also suggests a bit more of a traditional rash breaking
into the overnight hours and retreating back primarily to the
adjacent coastal waters of the Space and Treasure Coasts. Yet, an
isolated shower moving ashore cannot be ruled out so will oblige.
Winds should begin to decrease post-sunset to E-SE at 5 to 10 mph
inland and 10 mph along the coast except 10-15 mph for Treasure
Coast. These less than fully relaxed maritime winds will keep min
temperatures in the L/M70s along the immediate coast while
limiting fog development and overnight pooling of smoke from
wildfires. Inland min tempeatures will generally be in the
U60s/L70s.
Sun...(from previous) Surface high pressure remains stationed
over the western Atlc with associated east-west oriented ridge
axis north of central FL. In fact, fairly deep high pressure
ridging across the region will keep a deep SERLY flow across ECFL.
Expect another breezy/gusty day with ESE-SE surface flow. PWAT
values are forecast to increase during the day to nearly 1.40-1.50
inches areawide. Have opted to keep a SCHC for light rain over
the Treasure Coast/interior early in the day with perhaps an
isolated rumble of thunder late in the day across Lake County.
This due to the increase in moisture, slight cooling aloft, and
late day boundary collisions, though it remains entirely possible
that this scenario may occur west of Lake County. Just want fellow
bike- fester`s here to stay observant. QPF amounts are very low
and suspect most of the area will remain dry, but we will see an
uptick in cloud cover areawide.
The deep/strong SERLY flow with the added moisture/clouds may keep
our afternoon temperatures a few degrees below what we have
witnessed the past few days, though the additional moisture will
still make it feel sultry and people outside will need to stay
hydrated. Generally M80s along the coast and near 90 degrees/L90s
into the interior.
&&
.AVIATION...Mostly VFR thru remainder of this evening except for
tempo BKN025 KMLB-KVRB-KFPR due to VCSH thru at least 03Z. Then,
spotty MVFR ceilings overnight BKN015-025 especially toward
09-12Z.
&&
.MARINE...
Tonight-Sun...East-west surface high pressure ridging remains
north of the local coastal waters thru the period. Necessary to
hoist SCA for offshore waters south of the Volusia-Brevard County
line and near shore from Sebastian Inlet thru at least early Sun
evening. The pgrad sufficient to support near 20kt ESE-SE winds
here. Seas will also build to 6 FT across the proposed advisory
area. Cautionary statements necessary elsewhere except for
nearshore waters north of Volusia-Brevard County line, yet may
still include near shore Volusia by Sunday morning or early
afternoon. Dominant wave periods will be generally choppy between
5-7 seconds.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 72 84 72 87 / 10 10 10 30
MCO 71 89 71 90 / 10 20 10 40
MLB 76 85 75 87 / 10 10 10 30
VRB 74 86 74 87 / 20 10 10 20
LEE 73 90 73 90 / 10 20 10 40
SFB 71 89 71 90 / 10 20 10 40
ORL 72 88 71 89 / 10 20 10 40
FPR 73 86 73 87 / 20 20 20 20
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory until 8 PM EDT Sunday for Sebastian Inlet
to Jupiter Inlet 0-20 nm-Sebastian Inlet to Jupiter Inlet
20-60 nm-Volusia-Brevard County Line to Sebastian Inlet 20-
60 nm.
&&
$$
SHORT TERM...DS
LONG TERM....FJ
Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1037 PM CDT Sat Apr 29 2017
.DISCUSSION...See updated information for land areas below.
&&
.UPDATE...Tidal gauges in northern Mobile Bay are showing tide
levels approaching near 2 feet above normal. Given this, felt it
was prudent to expand the Coastal Flood Advisory to cover central
Mobile and Baldwin Counties as minor coastal flooding will be
possible along the shores of northern Mobile Bay, particularly
tomorrow afternoon. 34/JFB
&&
.PREV DISCUSSION... /issued 954 PM CDT Sat Apr 29 2017/
DISCUSSION...See updated information for land areas below.
UPDATE...No additional updates are needed for the rest of the
evening. Gusty southeast winds will persist along coastal areas
overnight with gusts of 30 to 35 mph. This southeast wind will
result in little drop in temperatures with lows in the 70s across
the area.
There is still uncertainty with the timing of storms and severe
weather threat for tomorrow. The last several runs of the HRRR
organizes the convection over east TX and develops a squall line
that approaches the MS river by 7am and southeast MS by noon. The
HRRR maintains this squall line as it approaches the MS/AL line
and indicates the development of an organized cold pool which
would allow this complex to continue east through the rest of the
area during the afternoon. This seems plausible given the amount
of instability present (2000-2500 J/kg MLCAPE and significant mid
level dry air to support the cold pool.) However, deep layer shear
quickly decreases with eastward extent which would suggest some
weakening is possible. If this more organized earlier line comes
to fruition, then the severe threat for the evening/overnight
becomes less certain due to the atmosphere being substantially
worked over.
Other guidance shows this first convective line weakening as it
nears us (likely due to the quick decrease of deep layer shear) with
the main thunderstorm activity/severe threat developing along the
cold front and impacting our region late afternoon through the
early morning hours.
We will have to watch things very closely overnight. Given the
strong elevated mix layer present over the area, we can see a
strong cold pool becoming organized and supporting the earlier and
more vigorous convective line, but confidence is not high.
Winds will become very gusty across the entire area tomorrow after
sunrise with gusts up to 40 mph outside of thunderstorm activity.
There will also be a chance of minor coastal flooding tomorrow
afternoon during high tide, especially for the typical flood prone
areas in and around Mobile Bay. 34/JFB
PREV DISCUSSION... /issued 646 PM CDT Sat Apr 29 2017/
DISCUSSION...See updated information for land areas and aviation
discussion below.
UPDATE...Isolated warm air advection showers have developed over
parts of inland SE MS and across the state line into far western
AL. Updated the forecast to maintain a slight chance of showers
through the next few hours. While we will let the inland portion
of the Wind Advisory expire at 7pm, we are issuing another Wind
Advisory for Sunday/Sunday evening as winds are expected to
quickly strengthen after sunrise. Frequent gusts of 30 to 40 mph
are expected given forecast soundings showing 35 to 45 knots in
the mixed layer. Will maintain the wind advisory for the coastal
counties tonight. While there will may be a lull in gusts this
evening, expect gusts around 30 mph, especially along the coast
overnight as the low level jet begins to strengthen, increasing
further after sunrise. 34/JFB
AVIATION...
00Z issuance...MVFR ceilings inland and IFR ceilings near the coast
expected to continue through the 24 hour period. Strong southeast
winds will persist as well, with wind speeds of 15 to 20 knots
gusting to 25 knots overnight strengthening to a sustained 25 knots
gusting to 35 knots by Sunday afternoon. A cold front with showers
and thunderstorms will approach from the west Sunday night, with
additional storms possible ahead of this line during the afternoon
hours. Some storms could become strong to severe, with gusty winds,
large hail, and frequent lightning possible. Heavy downpours will
lower vis/cigs in and around storms as well. /49
PREV DISCUSSION... /issued 305 PM CDT Sat Apr 29 2017/
Coastal Hazards Persist Through the Weekend...
Slight Risk of Severe Storms and Locally Heavy Rains Approach
from the West Late in the Day Sunday...
NEAR TERM /Now Through Sunday/...A strong 1027mb surface high
pressure area will remain centered over the western Atlantic with
a ridge extending west across the eastern Gulf of Mexico and
southeast states through Sunday afternoon. A band of showers and a
few thunderstorms are currently ongoing across the lower Great
Lakes region along an associated warm front lifting northward
through that region. Additional convection is also occurring
across central and eastern Oklahoma, southeast Kansas, and much of
Missouri associated with an area of low pressure over eastern
Oklahoma, while a cold front advances southeast through the central
and southern Great Plains. Also noted is a cluster of showers and
thunderstorms lifting northward over northern Louisiana. A deep
strong southerly wind flow will persist through Sunday afternoon
across our region between these two systems, and a Wind Advisory
will remain in effect across our coastal zones through the
overnight hours and the advisory will likley be expanded northward
across the remainder of the forecast area on Sunday.
A quasi-linear convective system (QLCS) will advance east across
the lower Mississippi River ahead of the cold front as the surface
low and upper low lifts north-northeast across the central
plains. This line of showers and thunderstorms will approach the
forecast area late Sunday morning, and advance eastward to the
Alabama River through late Sunday afternoon. Additional showers
and few thunderstorms are expected to develop ahead of the main
line across much of the forecast area through Sunday afternoon. A
deeply moist airmass with precipitable water values locally
enhanced over 2" along the line will bring potential for heavy
rainfall west of the Alabama River. Locations generally along and
west of the Alabama River remain most favored for severe weather
potential Sunday afternoon where a 40-50 knot low level jet will
be aligned with up to 1500 J/KG of available MLCAPE. Damaging
winds and possibly a few tornadoes embedded within the line will
be the primary severe weather hazards, though marginally severe
hail will also be possible.
The persistent strong southerly flow, high period swell, and high
tidal ranges will bring a high risk of deadly rip currents to the
local beaches through late Sunday. Surf heights will also continue
to build through the weekend, with breakers forecast to range as
high as 5-8 feet by Sunday. Minor coastal flooding may also occur
through the weekend as the persistent southerly fetch continues,
particularly in low lying areas as tides average around 1 foot above
predicted levels (which may equate to the 2 to 3 foot MSL range near
times of high tide).
Low temperatures tonight will range from 70 to 75 degrees. High
temperatures Sunday will range from 82 to 87 degrees inland areas,
with lower 80s across the coastal section. /22
SHORT TERM /Sunday night Through Tuesday night/...Heavy rainfall
and potential of severe weather still looks on track to impact
much of our forecast Sunday night. A vigorous upper level storm
system with a large area of significant mid level height falls of
some 15 to 25 decameters exits the central High Plains and is
progged to lift up across the Upper Mid-West thru the night.
Attendant cold front positioned over the Mississippi Valley at the
start of the short term period crosses the forecast area Sunday
night. Synoptic scale lift/deep layer forcing along and ahead of
the frontal zone will result in an ongoing and organized QLCS that
advances eastward through our forecast area overnight Sunday
night/early Monday morning. Storms moving within an anomalously
high, deeply moist airmass, with precipitable water values locally
enhanced over 2" supports potential for heavy rainfall. Amounts
between 2-4" with locally higher totals possible. Locations
generally along and west of the I-65 corridor remain most favored
for severe weather potential Sunday evening where a 40-50 knot low
level jet will be aligned with up to 1500 J/KG of available
MLCAPE. Damaging winds and possibly a few tornadoes embedded
within the line will be the primary severe weather hazards, though
marginally severe hail cannot be ruled out. The severe weather
risk may decrease with time late Sunday night as instability wanes
and 850 mb flow gradually veers and decreases, but will monitor
for a few embedded strong to marginally severe storms in addition
to locally heavy rainfall as convection spreads east overnight.
Front makes passage Monday morning with potential of lingering
showers/storms over the eastern zones before chances quickly drop
off. Quiet weather conditions are expected Tuesday, after the
passage of Monday`s cold front. Highs Monday 75 to 80 much of the
area and mid 80s interior to near 80 coast for Tuesday. Tuesday
morning lows coolest over the interior, dipping into the lower to
mid 50s while the coast will be more mild, in the upper 50s/lower
60s. /10
LONG TERM /Wednesday Through Saturday/...Overall, continuity will
be maintained in the longer term. Another storm system deepens as
it heads from the Rockies into the Plains. Downstream amplification
of the upper flow should aid in bringing the weakening front
(over the Gulf) back northward into our area along with return
of deepening layer moisture profiles. In addition, we also expect
the development of another frontal system to our north and west.
All-in-all, it looks like wet weather conditions are again
expected for mid to late week. Showers/thunderstorms will likely
begin during the day Wednesday. It looks like most of the rain
should fall over the region Thursday and Thursday night as the
synoptic scale system traverses the region. At this stage, we
can`t rule out the possibility of heavy rainfall with this storm
system, although integrated water vapor transport anomalies are
not nearly as great as they are with tomorrow`s storm system.
The cold front should move through the region Thursday/Thursday
night, with drier air advecting into the region in wake of the
front. Even with the drier airmass moving into the area, enough
synoptic scale forcing should remain from the upper system to allow
for a small possibility of lingering showers Friday over the
zones before ending. Daytime highs in the lower to mid 70s trend
much below seasonal normals Thursday thru Saturday. Overnight lows
could possibly settle into the upper 40s by Saturday morning over
the interior. /10
MARINE...A strong onshore flow will continue ahead of an
approaching storm system through Sunday night, and Small Craft
Advisories remain in effect through the weekend. Adverse conditions
are expected Sunday through early Monday morning as a strong storm
system brings the possibility of strong to severe thunderstorms
ahead of a cold front. The front should move east of the region
Monday, allowing conditions to gradually improve. Expect diminishing
offshore winds and subsiding seas for Monday and Tuesday. An onshore
flow should return by Tuesday night as another storm system
approaches from the west for mid to late week. /22
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Wind Advisory from 7 AM Sunday to midnight CDT Sunday night for
ALZ051>060-261-262.
Wind Advisory until midnight CDT Sunday night for ALZ263>266.
Coastal Flood Advisory until 4 AM CDT Monday for ALZ263>266.
High Rip Current Risk through late Sunday night for ALZ265-266.
High Surf Advisory until 4 AM CDT Monday for ALZ265-266.
FL...Wind Advisory until midnight CDT Sunday night for FLZ201>206.
Coastal Flood Advisory until 4 AM CDT Monday for FLZ202-204-206.
High Rip Current Risk through late Sunday night for FLZ202-204-
206.
High Surf Advisory until 4 AM CDT Monday for FLZ202-204-206.
MS...Wind Advisory from 7 AM Sunday to midnight CDT Sunday night for
MSZ067-075-076-078-079.
GM...Small Craft Advisory until 10 AM CDT Monday for GMZ650-655-670-
675.
Small Craft Advisory until 4 AM CDT Monday for GMZ630>632.
Small Craft Advisory from 6 AM Sunday to 4 AM CDT Monday for
GMZ633>635.
&&
$$
This product is also available on the web at:
http://weather.gov/mob
Area Forecast Discussion
National Weather Service Pocatello ID
206 PM MDT Sat Apr 29 2017
.SHORT TERM...Tonight through Sunday.
After a cool but tranquil day, expect the pattern to turn somewhat
more active for the next couple of days. The light showers that
developed this afternoon across the eastern high country should
quickly dissipate this evening. A weak front will approach the
region tonight producing an increase in cloud cover. Showers will be
possible on Sunday, with the best chances in the high country,
especially across the eastern highlands during the afternoon. Snow
levels will climb through the day, reaching to around 6500 feet by
afternoon. Expect breezy conditions to develop late in the afternoon
and early evening across portions of the Magic Valley into the Snake
Plain. However, think winds will remain below advisory levels. This
system will depart the area Sunday night leaving relatively quiet
conditions for Monday. A second system will arrive Monday night.
This looks like a weak system as well, possibly producing some light
showers for the high country. Snow levels expected to remain
relatively high, above 6000 feet.
Valle
.LONG TERM...Tuesday through Saturday night. Overall models are
remarkably consistent with the synoptic pattern next week. Both
indicate building of upper ridging into the Northwest US through
Thursday. This should result in dry and stable conditions along with
warmer than normal temperatures Thursday through Saturday.
The long-term periods are not without their forecast challenges
though. With the upper ridge axis shifting to the east Thursday
afternoon, we are opened up to a southwesterly flow ahead of an
advancing upper trough. Both GFS and ECMWF show a significant
deepening of the trough off the Pacific coast with an initial wave
impacting the Central Mountains Friday and lingering into Saturday.
Both models also show a split flow pattern developing as a cutoff
forms off the California coast by Saturday afternoon. Hinsberger
&&
.AVIATION...As of 2:00 PM MDT...With high pres continuing to build
in...mostly sunny skies, light winds at 10 kts or less, and
beautiful VFR conditions will continue into early tonight across SE
Idaho. The HRRR and GFS try to generate a stray shower or two over
the far eastern CWA this afternoon, but this is not supported by the
rest of the guidance. Some mid/upper level cloud cover will begin to
creep in overnight and will continue thicken/lower late Sun morning
ahead of our next wave, however VFR conditions are expected through
the end of our current TAF period at 18Z Sun.
Note: Data outage continues at the KDIJ wx station which limits our
sfc observational data in that area, thus we continue to carry AMD
NOT SKED for that terminal. This is a non-NWS station, and we have
no info on when the issue will be resolved. -KSmith/Hinsberger
&&
.HYDROLOGY...Flood warning continues for the Portneuf at Pocatello
and will remain in effect for quite some time. The forecast is for
the river to remain relatively steady. Flood advisory will continue
for the the Bear River in Bear Lake county from Montpelier to the
border. Minor flooding continues along the Bear River in these
areas.
Valle
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Charleston WV
1032 PM EDT Sat Apr 29 2017
.SYNOPSIS...
Warm southerly flow through the weekend. Cold front Monday. Upper
low with unsettled weather to end the work week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 1030 PM Saturday...
HRRR and RAP have come back less aggressive with potential
overnight convection across the northern zones, so took out any
chance and capped the area at slight.
As of 750 PM Saturday...
Added slights everywhere for a few more hours with the cooling
top of the boundary layer adding to some late evening
destabilization. Convection that forms should be short lived, as
the mid and upper levels are still not all that favorable for
sustaining vertical cumulus growth with lower moisture amounts.
As of 128 PM Saturday...
Precipitation last night and earlier today most likely moistened the
atmosphere further south than the models are indicating. It also
left lots of boundaries, some of which are currently obvious on radar
and satellite. Therefore will raise pops a bit this afternoon, more
than models would indicate.
After afternoon/evening precipitation dies off, not much expected in
the way of precipitation tonight.
Soundings on Sunday indicate that storms will once again have to
battle off dry air entrainment to get started. With a bit more
moisture available over southeast Ohio and northern WV, will raise
pops a bit there.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 310 PM Saturday...
Cold front pushes through Monday with showers/storms. Front
should be progressive as to not cause much water concerns
despite wet grounds across southeast Ohio and northern WV. A Much
fresher and cooler airmass arrives behind the front for
Tuesday.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 315 PM Saturday...
Uncertainty continues regarding the evolution of the mid/late
week omega block across the country. Models continue to waffle
regarding whether a developing low pressure system across the MS
Valley remains connected to the westerlies or if it cuts off
across the southeast states. This will play a significant
determining factor to the sensible weather across our area, with
temps and amount of rainfall. As a result, did not stray much
at all from Superblend.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
As of 750 PM Saturday...
Added some overnight visibility restrictions to PKB and EKN...
with the former possibly getting into late night shower
activity. Convection also heading towards the CRW vicinity from
the south, but this could fizzle out before it arrives as
daytime heating wanes. Convection has the chance to be in the
area through 03Z, but not going to carry VCTS at any site for
now.
Otherwise, SCT250 to prevail in the warm sector airmass across
the region.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z MONDAY...
FORECAST CONFIDENCE: Medium.
ALTERNATE SCENARIOS: Decaying convection could arrive at CRW in
the next hour. PKB SHRA is in question.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE SUN 04/30/17
UTC 1HRLY 00 01 02 03 04 05 06 07 08 09 10 11
EDT 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07
CRW CONSISTENCY H H H H H H H H H H H M
HTS CONSISTENCY H H H H H H H H H H H M
BKW CONSISTENCY H H H H H H H H H H H M
EKN CONSISTENCY H H H H H H H H H H H M
PKB CONSISTENCY H H H H H H H H H H H M
CKB CONSISTENCY H H H H H H H H H H H M
AFTER 00Z MONDAY...
IFR possible in showers and storms Monday into Monday night.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...None.
OH...None.
KY...None.
VA...None.
&&
$$
SYNOPSIS...RPY/30
NEAR TERM...RPY/26
SHORT TERM...30
LONG TERM...30
AVIATION...26
Area Forecast Discussion
National Weather Service Blacksburg VA
938 PM EDT Sat Apr 29 2017
.SYNOPSIS...
High pressure offshore will maintain a warm and humid southerly
flow of air across the region through Sunday. A strong cold
front will then move through the area Monday with showers and
thunderstorms, followed by some cooler, but near seasonal
temperatures through the first part of next week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 930 PM EDT Saturday...
Showers and storms continue to fade this evening, with main area
of convection further west over the VA/KY border. As we head
into the overnight, a few high-res models showing some sfc
convergence in the mountains of NC around midnight-3am, so have
added a few showers, possibly thunder there. Otherwise, some
high clouds in the north to move out, while some lower clouds
work in from the south overnight. A summerlike night with lows
in the 60s. Fog a possibility over the river valleys.
Previous early evening discussion...
Overall seeing a decreasing trend in stronger storms, though
still enough instability per mesoanalysis and high-res models to
keep a few strong storms around til 00-01z, mainly in WV, far
SW VA. Coverage will erode by midnight with mainly high clouds
overnight, with patchy fog in the west, where it rained.
Previous discussion from the afternoon...
Satellite imagery shows a Cu field along the NC/VA border with
other diurnally forced convective clouds starting to sprout up.
With warm air aloft providing an effective cap, do not see much
potential for anything more than a stray shower/storm mainly in
the mountains where orographic forcing may boost lift, though
some cells have just managed to launch in the far southwest and
HRRR seems to have a handle on this so will lean heavily on the
latest solution for structure of POP/QPF grids though late this
afternoon. It is worth noting that in this juicy airmass
instability is AOA 2500J/KG, so any storms will have a good
amount of energy to tap and can produce heavy downpours, gusty
winds, and possibly some hail.
Expect tonight to be quite similar to last night with mainly dry
conditions after any evening precipitation dissipates, followed
by patchy fog and a bloom of low clouds spreading up from the
south. Sunday is expected to be much like today with perhaps a
slightly higher chance of a shower/storm mainly later in the
afternoon, with increasing chances for precipitation arriving
after dark.
Temperatures will remain quite warm, though with a bit more
cloud cover Sunday will be a few ticks cooler. Lows tonight will
be in the middle 60s east of the Blue Ridge with upper 50s/lower
60s to the west. Highs tomorrow will generally be 80 to 85 in
the east, middle 70s west.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 235 PM EDT Saturday...
Good consensus on the overall pattern evolution Sunday night through
Tuesday. Deepening 500 MB closed low tracks from Kansas on Sunday
evening to Lake Superior early Tuesday morning.
Using the timing of the slightly faster GFS for the frontal passage
on Monday. This puts the cold front from eastern Ohio to eastern
Tennessee 8AM Monday morning and from eastern Pennsylvania to
eastern North Carolina by 2AM Tuesday. Still expecting strong
pre frontal winds and Convective Available Potential Energy
possibly in the 1000-2000 J/kg range Monday afternoon and
evening. Clouds from showers and thunderstorms upstream or from
widespread low stratus in the foothills and piedmont Monday
morning will have a large impact on how much heating and
instability there will be later in the day. Good surge of lower
850MB temperatures on Monday night along with pressure rises
around +5MB/6hrs so will keep winds gusty. Western upslope areas
will stay in the clouds behind the front Monday night.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 235 PM EDT Saturday...
Larger differences in the synoptic pattern show up in the
different models by Wednesday. WPC leaning heavily on the
ensembles with keeps a progressive amplified eastern trough.
Surface low moves far enough northeast to relax the pressure
gradient on lighten the winds by Tuesday night.
Will have highest probability of precipitation on Wednesday night
through Thursday night. Then with lower confidence due to the large
spread in the guidance will have lower probability of precipitation
by Saturday and Sunday. Will be keeping maximum temperatures below
normal for Thursday through Saturday.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
As of 700 PM EDT Saturday...
Expect VFR through the period. Will have to watch BLF/LWB for
another 1-2 hrs for potential shower/storm activity but most of
that is moving west of BLF and northeast of LWB as of 7pm EDT.
Expect overnight to be quite similar to last night with mainly
dry conditions followed by patchy fog and a bloom of low clouds
spreading up from the south. Will keep it scattered at DAN for
now, but will have to see how far north this plume makes it. Will
indicate MVFR vsby at KLWB and KBCB. Sunday is expected to be
much like today with perhaps a slightly higher chance of a
shower/storm in the afternoon, but still scattered at best to
keep out of tafs at this time.
Extended Aviation Discussion...
As a low pressure system approaches from the west late Sunday
night, the potential for showers and thunderstorms will increase
over the western mountains by early Monday. The cold front
associated with this system should reach the Appalachians Monday
and depart offshore by Tuesday morning. As such, expect the
best chance of MVFR conditions during the frontal passage from
west to east during Monday. VFR conditions return behind the
front on gusty westerly winds Tuesday followed by continued good
flying weather under high pressure Tuesday night into much of
Wednesday. However moisture may return to the mountains by late
in the day Wednesday with local MVFR possible in isolated
showers by the end of the day.
By Thursday next system should be impacting us with showers and
a few storms, so sub-VFR is likely.
&&
.CLIMATE...
Record highs were broken at Bluefield and Blacksburg today.
Details in RERRNK product.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...JH/MBS
NEAR TERM...MBS/WP
SHORT TERM...AMS
LONG TERM...AMS
AVIATION...JH/MBS/WP
CLIMATE...JR/WP
Area Forecast Discussion
National Weather Service Tallahassee FL
819 PM EDT Sat Apr 29 2017
.UPDATE...
The forecast through tonight looks to be on track, only minor
updates were applied to temperature/wind based on latest
guidance.
Some adjustments were made to thunderstorm chances for tomorrow
afternoon and night. For tomorrow afternoon, instability will rise
above 2000 J/kg across some inland areas; sea breeze forcing
could spark a few showers or possibly an isolated thunderstorm
across the FL Big Bend or southern GA, so added slight chance PoPs
to these areas. During Sunday evening through the overnight
hours, slightly higher chances of thunderstorms were added across
our western zones since some hi-res models are hinting at a
stronger/faster moving squall line pushing across the Gulf Coast
region during this time. The HRRR has been one of the most
aggressive models with the forward motion of this feature,
although it only extends out through 16Z Sunday at this time.
Other models have been much slower with the front/squall line, so
there is considerable uncertainty regarding possible thunderstorm
timing. As a result, additional adjustments to thunderstorm
chances will likely be needed through tomorrow.
&&
.PREV DISCUSSION [718 PM EDT]...
.NEAR TERM [Through Tonight]...
A light shower is possible for the remainder of the afternoon into
early evening across the region. Otherwise, it will be mostly cloudy
with only patchy fog expected overnight. Lows will be in the upper
60s to around 70.
.SHORT TERM [Sunday Through Monday Night]...
The upper low centered over the Four Corners region this morning
will be centered just north of the Great Lakes Monday morning. The
attendant surface cold front will translate eastward across our
forecast area on Monday, which is 6 hours or so slower than the NWP
model runs from 24 hours ago. There is still good agreement among
the various model runs that much of our region will receive some
needed rain on Monday.
The severe weather threat for Monday still appears marginal. We
expect a rather vigorous QLCS to approach our forecast area from the
west Sunday night, but to begin weakening as it enters southeast AL
and the FL Panhandle in the pre-dawn hours of Monday, as the parent
surface cyclone begins occluding over the Great Lakes. Significant
pre-frontal cloud cover is likely to limit MLCAPE values to 1000
J/kg or less, and weakening wind fields aloft with time will lessen
the potential for significant storm organization. Still, there may
be enough surface cold pool organization, especially early Monday
while vertical wind shear is stronger, to support isolated damaging
wind gusts. The main threat area will be for the region north
and west of Tallahassee.
.LONG TERM [Tuesday Through Saturday]...
We expect generally fair and warm weather Tuesday and Wednesday.
There is a good chance of rain Thursday as an upper-level trough
develops over the central Gulf Coast states. However, the global
models diverge considerably in their handling of this system by
week`s end, with the ECMWF and CMC models taking the trough axis
(and associated surface cold front) east of our forecast area
Thursday night, and the GFS closing off an occluded low over the
Deep South and having it meander through Saturday. The GFS solution
would keep rain chances for our region into Saturday, while the
other solutions would mean clearing by Thursday night. Temperatures
will be near average during this period, but could be below average
of the CMC/ECMWF solutions verified, with cooler, drier air entering
the area sooner.
.AVIATION [Through 00Z Monday]...
Southerly winds will become light during the next couple hours
with the loss of mixing as the sun sets. Expect winds to drop
below 10 kts by 01Z and winds will become southeasterly
overnight. Low clouds with MVFR cigs could develop at all
terminals early Sunday morning, and cigs are expected to return
to VFR levels by the early afternoon on Sunday. Winds will become
south-southeasterly during the mid-late morning hours and
increase to around 15 kts, with gusts to 20-25 kts possible at
ECP, DHN and TLH.
.MARINE...
Moderate to strong SE-S winds will continue across the coastal
waters through Monday, ahead of an approaching cold front. Advisory
conditions are possible at times, mainly west of Apalachicola. This
will lead to high surf, strong rip currents, and slightly above-
normal tides. Much lower winds and seas are expected mid week.
.FIRE WEATHER...
.HYDROLOGY...
Local rivers will remain below flood stage through at least Monday
morning. QPF values will generally be in the 0.50 to 1 inch range
from Tallahassee north and westward, and not enough to cause
significant river rises. QPF values in north FL will likely be much
less. More rain is expected later next week, but model differences
make it unclear as to how much of, if any a flood threat there will
be.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 69 86 70 81 58 / 10 10 20 60 30
Panama City 73 81 72 76 62 / 0 10 60 80 10
Dothan 69 87 69 79 56 / 10 20 70 80 10
Albany 69 89 70 80 55 / 10 10 30 70 10
Valdosta 67 89 69 84 60 / 10 20 20 50 40
Cross City 67 89 69 85 65 / 10 10 10 20 50
Apalachicola 72 81 73 79 63 / 0 10 30 50 20
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through late Sunday night for Coastal Bay-
South Walton.
GA...None.
AL...None.
GM...Small Craft Advisory from 5 AM to 5 PM EDT Sunday for Apalachee
Bay or Coastal Waters From Keaton Beach to Ochlockonee
River Fl out to 20 Nm-Coastal Waters From Ochlockonee River
to Apalachicola Fl out to 20 Nm-Coastal waters from
Suwannee River to Keaton Beach out 20 NM-Coastal waters
from Apalachicola to Destin FL out 20 NM-Waters from
Suwannee River to Apalachicola FL from 20 to 60 NM-Waters
from Apalachicola to Destin FL from 20 to 60 NM.
&&
$$
UPDATE...Lahr
NEAR TERM...Barry
SHORT TERM...Fournier
LONG TERM...Fournier
AVIATION...Lahr
MARINE...Fournier
FIRE WEATHER...Lahr
HYDROLOGY...Fournier
Area Forecast Discussion
National Weather Service Topeka KS
615 PM CDT Sat Apr 29 2017
...AVIATION UPDATE...
.SHORT TERM...(This evening through Sunday)
Issued at 330 PM CDT Sat Apr 29 2017
At 2 PM Saturday, a strong short wave trough was crossing the
forecast area, kicking out from a powerful longer wave trough
centered near the Four-Corners region. This short wave will spell a
temporary break in precipitation for parts of the area although
strong mixing in its wake will lead to winds gusting 40+ mph for 1-2
hours this afternoon. Some higher res model guidance suggests
localized 50+ mph is possible but have not seen that materialize yet
so will monitor closely. Otherwise, areas generally along and
southeast of a Council Grove to Holton line will continue avoid the
brunt of the subsidence and will continue with scattered showers and
thunderstorms through the afternoon.
Numerous ingredients are in place for heavy rain but convection
farther to the southeast is eating a lot of the instability and
keeping the focus for heaviest rain out of the local area.
Regardless, with near-record precipitable water values in the area
and RAP soundings indicating the presence of up to 1000 J/kg at
times through the night, the potential does remain for some
localized flash flooding. Otherwise, it appears that several of our
river forecast points will at least approach flood stage and
possibly rise out of the banks into mainly minor flood stage. All
told though, the forecast is holding pretty well with the rain rates
not being too excessive to this point, and the substantial rain
totals being spread across many hours...thus limiting overall flood
potential.
Another short wave moves overhead around sunrise with a large area
of rain likely by that time frame as well, possibly coming to an end
before 10 AM depending on overall speed of the system. Thereafter,
the upper low moves out and re-organizes the surface low with a dry
slot likely to develop over parts of the CWA while a large area of
deformation precipitation develops on the northwest flank of the
system and impacts much of north central KS. This again will be a
long slow rain but may be sufficient to cause some generally minor
flooding. Do not expect any snow through the daytime hours (at least
in the TOP forecast area).
.LONG TERM...(Sunday night through Saturday)
Issued at 330 PM CDT Sat Apr 29 2017
The mid-level and surface lows associated with this weekend`s storm
system will be vertically stacked over the CWA by Sunday evening
before lifting northeastward into Iowa overnight into Monday
morning. Models continue to show a well-defined trowal north and
west of the low, with a dry slot moving into portions of southeast
and east central KS. As a result, the best potential for ongoing
precipitation Sunday night into Monday morning will be across north
central to northeast KS. A very tight pressure gradient will be
present on the back side of this advancing surface low. As a result,
have increased the northwesterly winds with wind gusts upwards of 20-
30mph Sunday night and increasing to 25-35mph on Monday. These
strong northwesterly winds will support strong CAA into the region
with Sunday night lows plunging into the mid 30s to near 40 degrees
from northwest to southeast across the CWA. With surface
temperatures dropping to near the freezing mark, there is a slight
chance for some snow to mix in with the lingering light rain Sunday
night into Monday morning. However, model soundings show limited
saturation in the dendritic growth zone. As a result, do not
anticipate any snow accumulation at this time. Precipitation will
finally come to an end over northeast KS Monday morning with dry
conditions and clearing skies expected by the afternoon hours. These
clearing skies should allow for Monday high temperatures to quickly
reach into the upper 50s to low 60s.
As this strong mid-level low exits northeast, models show another
embedded shortwave developing within this mid-level trough. This
shortwave will likely track over the Rockies and progress
southeastward over the KS/OK border by midweek. However, there is
still model uncertainty with the strength of this shortwave and,
thus the coverage of scattered precipitation. At this time, have a
chance for scattered rain showers during the Tuesday afternoon
through Wednesday evening time period. As this shortwave trough
progresses southeast of the CWA, models show it becoming a closed
low north of the Gulf of Mexico with an expansive mid-level ridge
developing over the western U.S. on Thursday and sliding eastward
into the Northern and High Plains on Friday and Saturday. This
strong ridge will essentially create a blocking pattern, keeping the
closed low spinning north of the Gulf and a mid-level low near the
Pacific Northwest. As a result, expect a period of dry conditions
Thursday through Saturday, with high temperatures moderating into
the 70s with lows in the 50s by Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday)
Issued at 615 PM CDT Sat Apr 29 2017
The overnight hours are expected to remain IFR or LIFR with a
northeast wind as the surface low remains to the south and east of
the area. The surface low is expected to lift north through
eastern KS on Sunday and there may be some marginal improvement in
conditions as a dry slot tries to work in with the surface low.
Otherwise main uncertainty is in the specific numbers for VSBY
and CIGS as rain moves in and out.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Barjenbruch
LONG TERM...Hennecke
AVIATION...Wolters