Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/31/17
Area Forecast Discussion
National Weather Service Bismarck ND
905 PM CDT Thu Mar 30 2017
.UPDATE...
Issued at 855 PM CDT Thu Mar 30 2017
The biggest change with this update was to increase QPF for
tonight through Friday morning across eastern Divide and across
most of Burke county, potentially impacting Long Creek and the
upper portions of the Des Lacs River. The 22-00 UTC RAP and HRRR
iterations have consistently placed a maxima of QPF across these
areas. The RAP seems most reasonable, potentially as high as 0.50
to 0.75 inches, while the HRRR has run after run depicted QPF well
in excess of an inch by Friday morning. This locally higher area
of QPF is plausible with precipitable water near the 90th
percentile, around 0.60 inches, and a near stationary surface low
across northeast Montana.
UPDATE Issued at 453 PM CDT Thu Mar 30 2017
Quick update to add PoPs late this afternoon and early evening
across far southwest North Dakota per trends on the Bowman ARB
radar and webcam observations through 2145 UTC.
&&
.SHORT TERM...(This evening through Friday)
Issued at 223 PM CDT Thu Mar 30 2017
Rain chances north and west highlight the short term forecast.
Currently, low pressure is situated over eastern Montana with a
moderate southerly flow over western and central ND. Considerable
clouds across western and central ND, but there are some thin
spots and cloud free areas. And temperatures have responded well
in these areas, while struggling in portions of the north central,
southwest and southern James River Valley where clouds have held
on.
Late this afternoon and tonight, low pressure will move only
slightly east to along the ND/MT border. The west central and
northwest are areas that have been cloud free this afternoon. Thus
daytime heating, combined with low level convergence will lead to
late afternoon and evening showers. Have used a blend of short
term guidance as a start for late afternoon and evening pops. Late
tonight and Friday frontogenetical forcing increases over
southern Canada and sags south into northern North Dakota. Weak
synoptic scale forcing also remains over this area as a northern
stream shortwave trough moves slowly east along the International
border. Diurnal precipitation this evening will likely taper but
may not completely die off due to the aforementioned factors. The
combination of these two forces will then keep chance pops across
along and north of the Highway 200 corridor Friday into Friday
evening, with some likely pops possible along and north of the
Highway 2 corridor. In addition to the precipitation, convergence
along a weak cold front boundary along the International border
drops south during the day Friday, bringing a chance of fog with
the showers, mainly across the northern half of the CWA.
.LONG TERM...(Friday night through Thursday)
Issued at 223 PM CDT Thu Mar 30 2017
A storm system early next week, followed by a warm-up highlight
the extended forecast.
Friday night as colder air sinks south the precipitation type may
change to some mixed precip, before ending across the north, but
thinking now that with forcing diminishing quickly Friday evening,
QPF amounts associated with any mixed precipitation will be
minimal.
Friday night through Saturday a weak surface trough and weak
upper level shortwave trough track slowly east across the forecast
area. This will keep minimal precipitation chances in the
forecast, mainly across the west and north. Upper level flow
becomes more zonal on Sunday and a quick moving shortwave trough
tracking along the International border will bring another chance
of showers along the northern portions of North Dakota. With each
of these waves, there will be a minimal threat of mixed
precipitation during the late night and early morning hours across
extreme northern North Dakota. QPF amounts are also minimal with
these two systems.
Weak ridging on Saturday followed by another quick moving
shortwave tracking along the International border Sunday bringing
light qpf amounts to the northern tier counties. Early next week,
a stronger upper trough will track into the plains. Again, the
majority of the energy within this split trough tracks well to our
south. There is still quite a bit of uncertainty with respect to
precipitation placement and amounts, but the trend continues to
push the strongest forcing south of the state. After this system
moves through, there is better model consensus in building a
strong upper ridge over the western and central U.S. bringing a
warm-up to the forecast area by mid to late in the work week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 855 PM CDT Thu Mar 30 2017
Late tonight into Friday morning the threat of fog increases
across northern ND including KISN and KMOT. Scattered rain showers
are expected across western into north central North Dakota
tonight continuing into Friday.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...AYD
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...AYD
Area Forecast Discussion
National Weather Service Taunton MA
1003 PM EDT Thu Mar 30 2017
.SYNOPSIS...
A late season winter storm will bring rain, ice and snow to the
region Friday into Saturday, with the primary impacts expected
north of the Massachusetts turnpike where significant amounts of
wet snow and/or sleet are possible. High pressure brings dry
weather Sunday and Monday, followed by another approaching storm
on Tuesday.
&&
.NEAR TERM /UNTIL MIDNIGHT TONIGHT/...
10 pm update...
Although overruning persists in upstate NY and N PA this evening
the nose of it, moving into portions of W New England continue
to be lost to dry air thanks to sfc dwpt depressions holding
near 20F or more in spots. This will take some time to overcome,
but would not be surprised to see some if it begin to filter
into portions of extreme W MA/CT by about midnight or so and
continue east from there slowly. HRRR will be used as an update
for overnight POPs as it continues to delay timing each run as
it adjusts to ongoing conditions.
Other concern will be P-type, temps already running much warmer
than most guidance and although there is plenty of room for
radiational cooling dwpts are only in the 20s so they too will
be increasing as wet-bulb process occurs. Most of the precip
measured to the W continues as RA. Therefore, even if it begins
as SN or at least adjusts to SN toward the early morning hours,
am not confident on accumulation on area roadways unless
precipitation rates are high enough, something that has always
been in question.
Previous Discussion...
Dry weather will persist this evening, but clouds will be on
the increase from the west ahead of an approaching low pressure
system.
&&
.SHORT TERM /MIDNIGHT TONIGHT THROUGH SATURDAY/...
Highlights...
* Friday morning rush hour may be impacted by snow/sleet across the
interior but the primary impact will likely be in the higher
terrain
* Low confidence forecast Friday afternoon into Saturday with main
focus north of the MA Turnpike with main concern snow vs. sleet
Details...
Forecast confidence is quite low for a short term forecast, but will
go over the main issues into Saturday.
Part 1: Friday morning:
First things first, a burst of warm advection precipitation will
affect interior MA and northern CT early Fri am. A mixture of snow
and sleet will overspread this region roughly between midnight and 6
am. Precipitation may be mixed with rain in the lower elevations,
so probably not a big impact in that region although some slippery
spots are possible. However, across the higher terrain of northeast
CT and into portions of interior MA roads may be slippery for the
morning commute. Therefore, opted to post a winter weather advisory.
Meanwhile, across eastern MA and most of RI a mixture of light snow,
sleet and rain may develop Friday morning. However, core of low
level jet/forcing remains to the west so precipitation will be
light. Plus with temps above freezing very little impacts are
expected with just wet roads.
Part 2: Friday afternoon and night:
We may see a lull in the activity sometime later Friday morning into
the early afternoon. However, approaching vigorous closed upper
level low will be moving east from the mid Atlantic states. This
will increase the forcing for ascent and expect precipitation
intensity to increase Friday afternoon and especially by Fri
evening. At the same time, an area of mid level warmth in the 800 to
850 mb layer will be moving northward. The models are in
disagreement though in how far north this warmth will get. The NAM
is the warmest suggesting very little snow even near the NH border
with mainly sleet and some freezing rain. On the other side of the
coin is the GFS, which produces isothermal soundings and heavy wet
snow even south of the MA turnpike. Based on the considerable model
uncertainty, we blended the ECMWF/RGEM which seemed to be a
compromise.
Therefore, we think the threat for heavy snow will mainly be north
of the MA turnpike and especially across far north central and
northeast MA. There may be some marginal marine influence across
the immediate coast, but its quite cold in the 925 to 950 mb layer
so it is more of a question of how warm the 800 to 850 mb layer
gets. This will determine whether we see 6 to 12 inches of wet snow
or mainly a few inches of heavy sleet. There also may be some
freezing rain across the higher terrain, but that low level cold air
is pretty impressive so if the warm layer invades the region
probably more in the way of sleet. Ptype may change to all rain
along the northeast MA coast if marine influence eventually
wins out, but probably sleet or snow just inland.
Part 3: Saturday
Much of the guidance has slowed the departure of the system with
closed well developed mid level low parked south of southern New
England and strong easterly inflow. This is particularly true across
eastern MA where trowel/comma head may result in heavy precipitation
into Sat afternoon. Any rain/sleet will probably change back to
snow Sat morning across some of the region especially in northeast
MA, which may continue moderate to heavy at times into the
afternoon.
Headlines and Impacts...
Overall confidence is quite low in any particular outcome.
Therefore, we continued the winter storm watch north of the MA Pike
but expanded it into northeast MA including Boston Fri afternoon
into Sat afternoon. Snow vs. sleet will be the main story on
amounts which remain uncertain. If higher snow amounts are realized
down tree limbs and scattered power outages are possible given it
will be a wet snow. Highest risk for this will be near the NH
border.
While we did not bite on the GFS with the high snow amounts south of
the MA Pike, we opted to issue a Winter Weather Advisory for
northern CT/northwest RI and just south of Boston. The Fri am rush
hour may be slippery across the higher terrain of the interior with
burst of warm advection precip. In addition, an extended period of
sleet is possible for a time later Friday into Friday evening before
a change to rain. May also be freezing rain across the highest
terrain, depending on specific thermal profiles but enough sleet
mixed in will probably keep ice accretion below one quarter of an
inch.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Highlights...
* Mainly dry but cool conditions Sat night through Sun night
* Low pressure may bring periods of mixed precipitation across
portions of the interior Mon night into early Tue
* As the low passes during Tue, may see periods of heavy rain
along the S coast
* Another period of unsettled conditions possible Wed night-Thu
Overview...
Overall progressive pattern continues through most of the long
term period, though may briefly amplify early next week with a
period of dry but cool conditions. Beyond this, looks like there
will be two more weather systems bringing cool and unsettled
conditions.
12Z model suite in general agreement with continued fast flow
aloft. May see upper level ridging slowing the progression down
a bit late Sunday and Monday, but this tends to break down as it
pushes slowly E early next week. Another notable feature during
this period will be the unseasonably cool temps, especially
during the daytime hours, though may be close to normal around
the middle of next week.
Confidence lowers with progression of two possible systems from
about the Mon night-Tue and Thu timeframes, especially with the
fast steering flow aloft.
Details...
Saturday night...Moderate to high confidence.
Low pressure shifts E to the western Atlc, so expect precip to
taper off by about midnight or so. H85 temps will gradually fall
back to -3C to -6C by daybreak Sunday.
There will be some leftover N-NE winds early Sat night across
coastal areas. Gusts will range from 25-30 kt, highest across
the outer Cape and Nantucket, then should diminish as gradient
lessens after midnight. Clouds will begin to clear across the
interior after midnight.
Expect overnight lows to bottom out in the mid 20s across the
higher inland terrain to the lower-mid 30s along the coast.
Sunday-Monday...Moderate to high confidence.
Upper level pattern becomes briefly amplified with long wave
ridging building from Hudson Bay to the SE U.S. coast by Sunday
evening. Large N-S oriented surface high in tandem with the
upper system, so expect dry conditions during most if not all of
this timeframe.
Expect clouds to clear quickly on Sunday. NW winds will
continue, though will be light. This will keep cooler temps in
place, with highs mainly in the mid-upper 40s which is 5 to 10
degrees below seasonal normals.
With mostly clear skies and light/variable or calm winds,
should see good radiational cooling Sunday night. Lows will
range from the mid 20s to mid 30s, except some upper 30 readings
along the immediate S coast.
As the ridge works offshore during Monday, winds shift to E-SE.
Clouds will increase, mainly across western areas during the
afternoon. Expect temps to top off in the mid 40s to lower 50s.
Monday night and Tuesday...Moderate confidence.
High pres ridge moves off the New England coast Mon night, with
precip pushing NE with developing southern stream low pressure.
As this low pushes NE out of the southern Appalachians,
associated H5 short wave slides E off the mid Atlantic coast
around 00Z Wed, though some spread of timing and track amongst
the model and ensembles suite noted.
Will carry high end chance POPs for now, with best shot along
the S coast. Looks like good tropical moisture plume moves N as
PWATs increase to 0.9 to 1.2 inches by 12Z Tuesday (highest
values along the S coast, Cape Cod and the Islands). The 1.2
inch value is close to highest PWAT value for the date on SPC
Sounding Climo page. Along with E-SE winds, QPF amounts for this
timeframe from 0.35 to 0.9 inches, highest across the higher
terrain with the upslope wind.
Have forecasted temps running 5 to 10 degrees below seasonal
normals for early April due to thermal pattern and cooler
onshore flow.
Tuesday night through Thursday...Low confidence.
Overall general trends continue to be about average as
progressive upper pattern continues. Cutoff H5 low pressure
pushes out of the mid Mississippi valley by mid week, with
developing surface low pushing across the Great Lakes late
Wed/Wed night. For now, leftover precip from first exiting
system should shift offshore Tue night, then will be mainly dry
on Wed as weak ridging builds across.
Models and ensembles signaling digging H5 long wave
trough/cutoff low across upper Mississippi valley into the
Great Lakes during Wed as associated surface low develops by
Wed evening. Widening model solutions on timing and track of
this low. Overall trend is to shift the low east in the W-SW
flow aloft. Have brought chance POPs into western areas after
midnight Wed night, shifting eastward by Thu morning.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Saturday/...
Tonight...Moderate to high confidence. VFR though 05Z-06Z.
Should see spotty MVFR conditions in mixed -SN/-PL/-FZRA moving
into CT valley by around 05Z, spreading E through the remainder
of the night. Local MVFR-IFR CIGS may reach the CT valley from
06Z-09Z, reaching central areas by around 12Z.
Friday into Saturday...Moderate confidence. MVFR to IFR
conditions will dominate in periods of rain/ice and snow.
Primary focus for the snow/sleet will be north of the MA pike,
but some sleet and freezing rain is possible south especially in
the high terrain. Northeast wind gusts of 25 to 35 knots
develop very late Fri night into Sat on the coastal plain and
perhaps a bit stronger for Nantucket.
KBOS TAF...High confidence in VFR through 10z with lower
confidence thereafter depending on arrival time of
precipitation.
KBDL TAF...High confidence in TAF through 04Z tonight. A
mixture of snow, sleet and rain should arrive after 6z.
Outlook /Saturday Night through Tuesday/...
Saturday night...High confidence.
MVFR-IFR CIGS mainly across central and eastern areas Sat
night, though should improve to VFR from W-E mainly around or
after midnight as precip pushes further offshore. N-NE winds
gusting to 25- 35 kt along the coast, highest across outer Cape
Cod and the islands through midnight, then should diminish as
they back to NW.
Sunday-Sunday night...High confidence.
Expect VFR conditions Sunday-Sunday night. A few spots across
the higher inland terrain may see MVFR CIGS at times Sun
afternoon/evening.
Monday-Tuesday...Low to moderate confidence.
MVFR CIGS/VSBYS likely in -RA. May see periods of -SN/-PL/-FZRA
across central and N Mass, mainly N of the Mass Pike after 06Z
Mon through mid morning Monday. Periods of RA/+RA during Tue.
Precip should taper off Tue night.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Saturday/...High confidence.
Winds and seas will generally remain below small craft thresholds
tonight into Friday morning.
Approaching low pressure will result in increasing winds/seas
late Friday and especially late Friday night into Saturday. Gale
force E-NE wind gusts are expected over the open waters. Warnings
have already been issued beginning later Friday night. Seas may
build to over 15 feet on Saturday with persistent northeast
winds.
Outlook /Saturday Night through Tuesday/...
Saturday night...Moderate to confidence.
Expect N-NE winds gusting to 30-40 kt early, then will diminish
as they back to N-NW after midnight. Seas ranging up to 10-11
ft on the southern waters and 15-16 ft on the eastern waters
will subside overnight, but remain well above 5 ft. Gale
warnings continue through about midnight, then should lower to
small crafts. Local visibility restrictions in areas of rain
and snow, which will improve on portions of the southern waters
after midnight.
Sunday-Sunday night...High confidence.
Will see leftover NW gusts up to around 25 kt on the outer
waters early Sunday, then will diminish. Seas will continue to
subside, but will remain at or above 5 ft on the eastern outer
waters through Sunday night. Any visibility restrictions on the
eastern outer waters will improve by mid morning Sunday.
Monday-Tuesday...Low to moderate confidence.
Light NW winds on Mon will shift to E-SE Mon night. Seas should
subside below 5 ft Mon morning. Good visibilities early Monday,
then will lower in developing light rain.
By Tuesday, E-NE winds increase, gusting to around 25 kt on the
southern outer waters. Seas build up to 6-8 ft, highest on the
southern outer waters Tue afternoon. Local reduced visibilities in
areas of light rain through the day.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory from 2 AM Friday to 8 AM EDT Saturday
for CTZ002>004.
MA...Winter Storm Watch from Friday afternoon through Saturday
afternoon for MAZ007-014-015.
Winter Weather Advisory from 8 AM Friday to 8 AM EDT Saturday
for MAZ013-016.
Winter Weather Advisory from 2 AM Friday to 8 AM EDT Saturday
for MAZ009-011-012.
Winter Storm Watch from 8 AM EDT Friday through Saturday
afternoon for MAZ002>006-008-010-026.
RI...Winter Weather Advisory from 8 AM Friday to 8 AM EDT Saturday
for RIZ001.
MARINE...Gale Warning from 7 PM Friday to 9 PM EDT Saturday for
ANZ232>235-237.
Gale Warning from 4 AM to 9 PM EDT Saturday for ANZ231.
Gale Warning from 4 AM Saturday to midnight EDT Saturday night
for ANZ250-251-254.
Gale Warning from 7 PM Friday to midnight EDT Saturday night
for ANZ255-256.
&&
$$
SYNOPSIS...Frank/EVT
NEAR TERM...Frank/Doody
SHORT TERM...Frank
LONG TERM...EVT
AVIATION...Frank/EVT
MARINE...Frank/EVT
Area Forecast Discussion
National Weather Service Columbia SC
1114 PM EDT Thu Mar 30 2017
.SYNOPSIS...
A warm front will lift north of the forecast area tonight ahead
of an approaching cold front. The cold front will pass through
the area during midday Friday. These features will support a
continued shower and thunderstorm chance followed by drier air
behind the departing system Friday afternoon. High pressure
will dominate over the weekend. The next system to affect us
will be Monday with another chance of showers and thunderstorms.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
An upper low will lift northeast into the Ohio River Valley
overnight. An associated shortwave trough will be over the
forecast area during the early morning hours.
Showers and thunderstorms will likely return to the area
overnight associated with the upper system and ahead of the
cold front. Instability should be limited by previous
convection and nocturnal cooling. However, there still may be
sufficient instability combined with strong shear for severe
thunderstorms. The RAP indicated h85 wind increasing to near 50
knots during the early morning hours. The main threat should be
damaging wind and hail. Cannot rule out tornadoes because of the
added shear associated with a lingering warm front. Followed
the HRRR for the timing of more likely pops. Clouds and boundary
layer mixing will help hold up temperatures. Expect lows mainly
in the middle 60s.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/...
There is uncertainty as to how fast the cold front will move
through the area Friday morning. The 12Z GFS has it almost out
by 11 AM, while the NAM holds it back across the midlands, and
doesn`t move it through until around 2 PM. The timing will have
a significant impact on how strong the storms are. The NAM is much
more unstable because partial daytime heating can be taken into
account. Forecast is a compromise between the models on timing,
with strong storms expected to be moving through the area from
southwest to northeast during the morning, and then diminishing
after noon. Some of the storms could become severe with large
hail, damaging winds, and isolated tornadoes cannot be ruled out
given good vertical wind shear. The cold front will move out by
5 PM, with drier air filtering into the region. Breezy conditions
are expected behind the front.
A high pressure ridge will shift over the region on Saturday,
and it will be mild and dry with high temperatures in the mid
70s to lower 80s. Similar conditions are likely Sunday.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
Another low pressure system will move through the region Monday
and Monday night with the next chance for showers and thunderstorms.
Showers will taper off on Tuesday, and high pressure will return
briefly. There is uncertainty with the arrival of the next low.
The 12Z GFS is much faster and stronger than the 00Z ECMWF and
12Z Canadian, bringing a quick shot of rain on Wednesday, while
the other models do not bring showers in until Thursday. Leaning
towards the slower solution and introduce the chance of showers
and thunderstorms Wednesday night. Temperatures will remain above
normal through the period.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Restrictions expected through much of the period.
Showers and an isolated thunderstorm continue moving across the
area with showers currently around AGS/DNL/OGB. Expect much of
the activity over the next couple hours to remain scattered then
increase in coverage as convection ahead of the cold front
enters the area. Expect MVFR to IFR conditions due to convection
to begin during the early morning hours and continue through
mid morning...with the front crossing the area around midday.
Main concern with the convection will be potential for strong
gusty winds and lower potential for hail. Current southeasterly
winds between 8 and 10 knots will slowly veer overnight to
southerly during the early morning hours...then turn westerly
and become strong and gusty from 17z onward as the front moves
east of the terminals. With the gusty winds drier air will enter
the region returning all sites to VFR.
EXTENDED AVIATION OUTLOOK...Restrictions possible in showers
and thunderstorms Monday and Monday night as a cold front
crosses the region.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Charleston SC
1008 PM EDT Thu Mar 30 2017
...ISOLATED SEVERE THUNDERSTORMS POSSIBLE OVERNIGHT...
.SYNOPSIS...
A warm front will move northward through the region tonight followed
by a cold front crossing through Friday night. High pressure is
expected to bring dry conditions this weekend. Unsettled weather
returns on Monday, possibly lasting into Tuesday. Dry weather should
then return during the middle of next week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
KCLX reflectivity and NLDN data indicate convection is starting
to increase across interior Southeast Georgia. This recent uptick
suggests the leading edge of a corridor of deep layered forcing
ahead of an approaching southern stream shortwave is beginning
overspread the area from the west and southwest. This region of
stronger forcing will continue intensify overnight as a broad
area of difluence builds between the upper low spinning over
eastern Missouri and a 125 kt jet stream moving across the
northeast Gulf of Mexico.
Both the RAP, H3R and a number of the various CAMs continue to
show convection blossoming over the next few hours as forcing
increases and a strengthening low-level jet forces the warm
front near the Altamaha River northward. Mid-level lapse rate
are forecast to cool slightly as a tongue of mid-upper 60s
dewpoints advects inland across southern South Carolina from off
the Atlantic. Noted KNBC reported a dewpoint of 67 at 31/01z.
The combination of higher dewpoints and cooler temperature aloft
will support modest nocturnal instability featuring SI`s as low
as -1 to -2C, LI`s -2 to -4C and SBCAPE 700-1000 J/kg. With
deep layered shear on the order of 45-50 kt coupled with
favorable hodographs for supercells, think there is a potential
for a few severe thunderstorms and possibly a tornado or two to
develop along the northward moving warm front later tonight,
mainly along/east of a Walterboro-Beaufort line coincident with
the axis of higher low-level moisture. The RAP has been
consistent for several runs now showing a corridor of SigTor
values of >1 units developing across the northern 1/3rd of the
forecast area. Indeed, the last few runs of the H3R show a
potentially scary scenario with layered reflectivity data
depicting a several supercells moving northeast across the
Charleston Tri-County area. SPC Day 1 WFO guidance recently
upgraded areas north of Walterboro from a marginal to slight
risk which seems well placed.
For the late evening update:
* Increased pops to 80% for the Charleston Tri-County area and
made other minor pop adjustments elsewhere.
* Inserted damaging winds, tornadoes and large hail attributes
in the slight risk area.
* Made minor changes to hourly temperatures and dewpoints per
going trends.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
A cold front will approach the region Friday and then push through
Friday night. Lift along with a shortwave moving through will
generate showers and thunderstorms Friday morning, especially
inland. Overall instability is meager, especially since it`s before
peak heating, so the severe weather threat is low. Remnant showers
will quickly diminish Friday afternoon as the approaching cold front
pushes the moisture offshore. The daytime hours should be breezy
with gusts up to around 25-30 mph. Following frontal passage Friday
night, a broad area of high pressure will spread across the East
Coast, bringing dry weather this weekend.
Temperatures should remain above normal Friday due to compressional
heating ahead of the front. Despite the slight cool down behind the
front this weekend, temperatures should remain above normal due to
downslope flow.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Dry high pressure to prevail through Sunday night although moisture
will be increasing Monday morning as low-level jetting ramps up
ahead of approaching low pressure from the west. Looks like a good
shot of showers and storms Monday and Monday night as low pressure
passes by to the northwest of the area. Could be another high
shear/low CAPE situation and a few severe storms might be possible.
Things should clear out by Tuesday but the ECMWF still indicates a
few showers possible, mainly across SC. High pressure will then move
in through Wednesday before another storm system likely moves across
the Deep South and brings rain back to the area Wednesday night into
Thursday. Temperatures should remain above normal through the
period.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
The risk for tstms is the primary concern overnight. Greatest
chances look to occur at KCHS where high resolution models show
a few lines of convection moving through roughly 06-10z. Will
show tempo groups for MVFR conditions during this time, but
lower conditions could for brief periods. Convection looks to
pass just north of KSAV so will keep any mention out of that
terminal for now. Models are trending quicker with the ending of
precipitation early Friday with gusty winds developing.
Extended Aviation Outlook: Restrictions likely Monday and
Monday night.
&&
.MARINE...
Tonight: increasing southeast winds tonight will bring higher
seas to the marine area, primarily the Charleston nearshore
waters and GA offshore waters. We posted a Small Craft Advisory
for these two waters beginning at 11 pm.
Friday through Tuesday: A cold front will move through Friday
night/early Saturday. Advisories due to winds and seas should be in
place for all coastal marine zones Friday morning, except for
zone AMZ354. The worst conditions are expected across AMZ374 and
the northeastern portion of AMZ350. These advisories are
expected to drop off Friday night as high pressure moves towards
the area, allowing winds and seas to trend downward. Conditions
will go downhill again Monday as a storm system approaches from
the west and Advisories will be possible Monday into Tuesday,
at least for the offshore GA waters and SC waters.
&&
.TIDES/COASTAL FLOODING...
Given a 0.7-0.9 ft anomaly with the last two high tides, shallow
coastal flooding looks all but certain along the SC coast late
this evening. Therefore we issued a Coastal Flood Advisory with
expected levels of 7.3-7.6 ft MLLW. Chances are lower that the
Ft Pulaski gage will reach 9.2 ft MLLW though it will definitely
be close. We will hold off on issuing an advisory there until
trends can be monitored further.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Coastal Flood Advisory until midnight EDT tonight for
SCZ048>050.
MARINE...Small Craft Advisory from 9 AM Friday to midnight EDT Friday
night for AMZ352.
Small Craft Advisory until midnight EDT Friday night for
AMZ350-374.
&&
$$
Area Forecast Discussion
National Weather Service Quad Cities IA IL
649 PM CDT Thu Mar 30 2017
...AVIATION UPDATE...
.SYNOPSIS...
Issued at 250 PM CDT Thu Mar 30 2017
18Z surface data has low pressure near KSTL. A warm front extended
from the low into central Indiana. Dew points were in the 30s from
the Great Lakes into the central and northern Plains. Dew points in
the 40s and higher ran from the Ohio Valley into the southern Plains
on south to the Gulf Coast.
&&
.SHORT TERM...(This Evening through Friday)
ISSUED AT 250 PM CDT Thu Mar 30 2017
An upper level disturbance from the overnight convection is moving
northeast across southern Illinois. This disturbance has developed
an arc of thunderstorms from east of Quincy into southern Illinois.
Based on radar and RAP trends, the best chances for rain late this
afternoon is south of I-80. The more stable air across the area
should cause any thunderstorms to dissipate as they move north.
However, some isolated thunderstorms are possible south of a KVYS to
KFFL line through sunset.
Across the northern half of the area spotty light rain and drizzle
can be expected through sunset.
After sunset, the better forcing associated with the storm system
will move into eastern Illinois and Indiana. Rain will end from west
to east overnight with areas west of the Mississippi dry by sunrise
Friday.
On Friday, any lingering light rain will end east of the Mississippi
during the morning leaving dry conditions for the afternoon.
Clouds are expected to remain in place overnight and Friday morning
before clearing occurs from west to east during the afternoon.
.LONG TERM...(Friday Night through Thursday)
ISSUED AT 250 PM CDT Thu Mar 30 2017
Active weather pattern is expected to continue in the extended with
not much change to the going forecast. Friday night and Saturday,
dry conditions are expected as a ridge of high pressure builds over
the Mississippi River Valley region. The next chance for
precipitation comes late Saturday night through early Monday with
the passage of a low pressure system to our south. A brief break in
the precipitation chances is expected Monday through midday Tuesday,
before the next; and more potent; system takes a more direct path
over the area for Tuesday afternoon through Thursday morning.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
ISSUED AT 645 PM CDT Thu Mar 30 2017
Generally IFR conditions tonight with patchy light rain/drizzle ending
by late evening as a low pressure system in Iowa moves slowly east.
The low clouds will rise to MVFR by mid/late morning as the low continues
to move east. Northeast winds 5 to 15+ MPH will shift to the north
tonight through Friday.
&&
.HYDROLOGY...
Issued at 250 PM CDT Thu Mar 30 2017
Recent heavy rainfall has resulted in some rises on area tributary
rivers. In particular, the Wapsipinicon River near De Witt and the
Rock River at Joslin and Moline; where they are expected to reach
within a foot of their respective flood stage levels within the next
1 to 3 days.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SYNOPSIS...08
SHORT TERM...08
LONG TERM...14
AVIATION...Nichols
HYDROLOGY...14
Area Forecast Discussion
National Weather Service Lincoln IL
907 PM CDT Thu Mar 30 2017
.UPDATE...
Issued at 905 PM CDT Thu Mar 30 2017
Will update the forecast to remove chances of thunderstorms in far
eastern IL this evening and some adjustments to winds. Otherwise
forecast generally on track tonight as scattered showers occur
with mostly cloudy to overcast skies. Lows to range from around
40F over the IL river valley, to the upper 40s in southeast IL.
Mid evening surface map shows 1000 mb low pressure over central IL
nw of Decatur. Aloft a 550 dm 500 mb low was over east central MO.
Scattered thunderstorms passed east of IL early this evening,
while scattered showers were more numerous west of I-55 and just
isolated showers east of I-55. Some patches of fog from I-55 west
where IFR clouds present.
Latest models lift surface low pressure into nw Ohio by 12Z/7 am
Fri while still trofing back into east central IL. The upper level
low tracks from east central MO into sw Indiana by sunrise Friday.
Most models keep qpf around central IL into Fri morning as IFR
clouds spread into eastern IL during overnight. Winds to become
North to NW 10-15 mph during rest of the night and into Fri
morning and few higher gusts on back side of storm system.
&&
.SHORT TERM...(This evening through Friday)
ISSUED AT 250 PM CDT Thu Mar 30 2017
Strong to severe convection currently ongoing along a Rushville...to
Springfield...to just west of Effingham line will continue to track
northeastward across the area late this afternoon into the early
evening. Based on radar timing tools and the latest HRRR output, it
appears the storms will exit the KILX CWA into west-central Indiana
by 01z/8pm. Have therefore held on to categorical PoPs for thunder
across the far E/NE around Champaign and Paris into the early
evening. Once these storms exit, additional showers will develop
within the deformation zone of a departing low. Models have been
consistently showing this precipitation breaking out across the
Illinois River Valley this evening...then slowly shifting eastward
overnight. With the primary instability axis shifting well to the
east into the Ohio River Valley, do not think any widespread thunder
will occur with the precip on the back side of the low. Have
therefore gone with likely PoPs for showers across the west this
evening...then everywhere except locations near the Indiana border
overnight. Temperatures will cool on the back side of the
low...with overnight lows ranging from the upper 30s far north
around Galesburg...to the upper 40s south of I-70. Deformation zone
showers will persist across the area into Friday morning before
gradually dissipating and coming to an end by midday. Despite the
end of the precip, skies will remain overcast through the entire
day. Clouds and brisk northwesterly winds will keep high
temperatures below normal for this time of year in the upper 40s and
lower 50s.
.LONG TERM...(Friday night through Thursday)
ISSUED AT 250 PM CDT Thu Mar 30 2017
An active weather pattern to hold over the Midwest for the next
week as a series of upper level waves track into the Rockies and out
into the Plains, eventually affecting our area with showers about
every 2 to 3 days. The next system to affect us will be coming along
on Sunday and Monday, followed by a rather vigorous upper wave by
late Tuesday or Wednesday of next week bringing another chance
for showers. Models seem to have latched on to Wednesday`s system as
the one that may bring down some rather chilly air for the middle
and latter portion of next week as a large trof deepens in over the
Great Lakes. Until that happens, other than a brief cool down in the
wake of these upper waves, our temperatures are expected to average
above normal as we head into the middle portion of next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 659 PM CDT Thu Mar 30 2017
999 mb surface low pressure just west of Lincoln IL early this
evening will track to the northern IN/OH border by 12Z/Fri and
into nw PA by sunset Fri. Winds will veer to the W/NW behind the
departing low pressure system tonight and Friday and be 8-14 kts
with few higher gusts especially during day Friday. Scattered rain
showers will continue tonight into Friday morning before exiting
east of area by Fri afternoon. IFR clouds poised to the northwest
of I-55 across Iowa/northwest Illinois including PIA will spread
se into central IL during this evening and early overnight,
reaching CMI between 06-07Z. IFR ceilings should gradually lift to
low end MVFR ceilings of 1-1.5k ft during Friday afternoon.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...07
SHORT TERM...Barnes
LONG TERM...Smith
AVIATION...07
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
635 PM CDT Thu Mar 30 2017
.SHORT TERM...
229 PM CDT
Through Friday..
Main concerns are threat for strong to severe
thunderstorms this afternoon through early this evening south of
I-80 and unseasonably chilly and blustery conditions on Friday,
especially near the lake shore.
Continuing to monitor for the threat for strong to severe
thunderstorms south of I-80 later this afternoon, and particularly
south of the Kankakee River. The convection that has been lifting
north-northeast across the CWA is associated with a short-wave
disturbance ahead of the closed mid-upper low over Missouri. Given
strong moist transport flowing over warm front and PWAT values
around or over 1", main threat prior to this activity exiting per
latest radar trends is heavy rainfall and localized
ponding/flooding on some roads. This is especially the case with
saturated grounds due to what already fell overnight. Large areal
Flood Advisory that was issued remains in effect through 7pm.
Otherwise, can`t rule out some small hail to pea or dime size
(especially south of I-80) for stronger cores with cold
temperatures aloft/700 mb temps near or below 0 Celsius resulting
in fairly low freezing levels and wet bulb zero heights.
The main risk for strong to severe thunderstorms looks to evolve
over or just south of our southern CWA counties in the mid to late
afternoon, particularly south of the Kankakee River. What occurs
will likely be associated with arc of thunderstorms lifting
north-northeast from STL area. Good speed shear will be in place
with strong lower and mid- level flow, but directional shear from
850-500 limited given meridional nature of closed low. As low
pressure just north of STL lifts northeast this afternoon, surface
warm front will continue to progress north and likely reach areas
south of the Kankakee River, namely portions of Ford, Iroquois,
Benton, and Japser and Newton Counties.
Temperatures in the 60s and dew points approaching or just above
60 topped by relatively steep lapse rates could yield 500-1000
j/kg of SBCAPE near and south of warm front based off obs and
latest RAP forecast. In presence of supportive bulk shear,
embedded low topped supercell structures and small scale line are
favored. With earlier mentioned parameters in favor of hail,
threat for marginally severe hail could extend northward to near
I-80 with elevated MUCAPE north of surface warm front. Where warm
sector reaches, anticipating backed (southeast/east-southeast)
surface winds to result in decent veering in lowest 1km, which
could be enough low-level shear/SRH for an isolated tornado risk.
In addition, downdrafts from strongest warm sector storms would
pose a risk for damaging winds. Overall thinking hasn`t changed
much since previous update and will continue to pay close
attention to observational trends. The threat for any severe
weather should end during the early evening hours.
Approximately 1000 mb surface low will then track east-northeast
south of I-80 tonight into Friday morning, with system
deformation rain/showers diminishing and then shifting east on
Friday morning (with lowering PoPs in grids). Tight pressure
gradient between the exiting low pressure and high pressure around
1020 mb over the northern Great Lakes will result in strong and
gusty north to north-northeast winds, with gusts of 25-30 mph near
Lake Michigan. Expansive stratus will keep skies locked in
overcast, so temperatures will struggle to climb into the mid 40s
away from the lake. Strong northerly boundary layer flow down the
length of the still cold waters of Lake Michigan will keep
high temperatures even colder near the lake, in the upper 30s to
around 40. March will go out like a lion temperature wise with a
decided brisk/wintry feel, so be sure to dress accordingly.
Castro
&&
.LONG TERM...
229 PM CDT
Friday night through Thursday...
The upper level split flow pattern will continue through the weekend
and most of next week with some model signals toward a pattern shift
late next week/next weekend toward a more amplified pattern. Such
evolution would bring larger scale mean ridging established over
western North American and mean troughing in the east.
In the meanwhile, main forecast concerns continue to be on
periodic rain with scattered thunderstorms, first later Sunday
into early Monday, with a more potent system with the potential
for more soaking rains Wednesday into Thursday.
As the surface and upper low continue to exit to our east Friday
evening, surface ridging will continue to build into the area
from the west. This combined with rising heights aloft will help
yield a relatively pleasant early spring day for the area
Saturday, albeit chilly for areas near Lake Michigan with a
prevailing synoptic north flow. With north winds moving across the
40-44 degree surface water, expect max temps to hold in the 40s
with highs into the low- mid 50s as you further inland.
The next in the parade of upper level troughs will approach the area
Sunday. Despite a weakening trend as the trough ejects out of the
mountains and into the plains, expect clouds to thicken following
by rain overspreading the area west to east Sunday afternoon.
Better low level forcing remains well south with unphased upper
low moving into the mid Mississippi valley inhibiting better
moisture flow this far north. Still a period or two of light rain
likely with upper system and associated surface inverted trough
then exiting to the east across Indiana Monday.
With rising heights Tuesday expect a milder day but max temps will
again be held back near the lake with the prevailing NE flow.
Significant model differences in the next in the series of upper
lows... this one moving across the central plains Tuesday and
Wednesday. Forecast reflects blended solution with general agreement
toward a fairly dynamic system and potential for another round of
soaking rain and scattered embedded thunderstorms Wednesday into
Thursday.
Ed F
&&
.AVIATION...
For the 00Z TAFs...
635 pm...Main forecast concern this period are cigs along with
showers/drizzle and possible fog/low vis.
Low pressure over south central IL will move northeast to northern
OH Friday morning. This track will maintain northeasterly flow off
the lake into Friday morning. Most guidance keeps cigs in the 400-
600ft range through sunrise and then begins a slow climb through
ifr into low mvfr Friday afternoon. Followed this trend with
medium confidence but its possible cigs may dip lower tonight...
especially if any widespread drizzle develops. Cigs should start
to scatter from the north Friday afternoon and this clearing may
reach the terminals sooner than indicated in the 30 hour ord
taf...but confidence is low.
Current showers south of lot/gyy have been slow to lift north and
may begin to dissipate before reaching the rest of the terminals.
Opted to maintained shower mention this evening with uncertainty
as to how much additional shower activity may develop but much of
this evening could end up dry northwest of mdw/gyy. Additional
showers or drizzle are expected tonight into Friday morning.
With the expectation that low cigs will remain well into Friday...
not too confidence on fog producing visibilities too low and
maintained mvfr vis with this forecast but some guidance does
suggest vis may drop as low as 1sm. Currently expect any vis
reductions this low to be combined with drizzle but trends will
need to be monitored this evening.
Northeast winds 10-15kts with some higher gusts this evening will
slowly turn more northerly overnight and then remain northerly
for much of Friday. Speeds/gusts will increase Friday morning with
gusts into the mid 20kt range expected. Winds will begin to
diminish with sunset Friday evening and begin turning more to the
north/northwest. cms
&&
.MARINE...
156 PM CDT
Surface low pressure tracking across central Illinois this
afternoon will move east into Ohio overnight, with east-northeast
winds becoming north-northeast by Friday morning. Forecast
soundings support winds generally in the 25-30 kt range, though
there may be a brief period of marginal gale force gusts just
before sunrise on the northern portion of the western (WI) shore.
The gradient will begin to weaken Friday afternoon as the low
continues to pull away and redevelop off the Atlantic coast, and
weak high pressure spreads southeast across the upper Midwest and
western Lakes into Saturday. The surface high pressure ridge will
drift east across Lake Michigan by Sunday morning, allowing winds
to veer to the southeast during the day. A trough of surface low
pressure will approach from the west Monday morning, with low
centers passing north of Lake Superior and farther south across
the lower Mississippi/Tennessee river valleys. Medium range model
guidance depicts a stronger low may impact the Midwest Wednesday,
passing near or just south of Lake Michigan. This may result in a
period of stronger easterlies Wednesday which would shift to the
north-northwest Wednesday night into Thursday.
Ratzer
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...Winthrop Harbor to Burns Harbor until
4 AM Saturday.
&&
$$
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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Area Forecast Discussion
National Weather Service Lubbock TX
627 PM CDT Thu Mar 30 2017
.AVIATION...
VFR with light winds through most of Friday, except at LBB where
SW winds of 15-20 knots are likely by midday. Moistening E winds
at CDS overnight could garner some TEMPO low vis there, but odds
are against this for now.
&&
.PREV DISCUSSION... /issued 326 PM CDT Thu Mar 30 2017/
SHORT TERM...
Quiet weather across the forecast area this afternoon and much
warmer compared to yesterday thanks to mostly clear skies and a
decent downslope wind, mainly across the southern third of the
forecast area. The back door front that the 12-18Z HRRR and RAP
runs have continued to advertise has yet to materialize as surface
winds across the rolling plains have remained light and variable.
Models continue to insist that at some point tonight into the early
morning hours, a weak front will push west across the forecast area
resulting in an easterly wind through the night. The ARW and GFS
however keep the front east of the Caprock and have a southwest wind
across the Caprock through the night. Have opted to lean towards
the latter two models which means that we should see temps lean
towards the warmer guidance for locations on the Caprock thanks to
the west wind remaining in place. Biggest question will be if low
clouds and/or fog will develop across the Rolling Plains if easterly
upslope surface flow can develop. Models have been overestimating
the dewpoints early in the day but have gotten closer to
observations this afternoon so feel that the potential for fog and
low clouds is low but still non-zero.
Wind will start to veer back to the southwest for the Caprock by
sunrise but with uncertainty if the Rolling Plains will manage to
keep an easterly wind through the day. Dry air does mix back into
the southwestern Plains to near I-27/edge of the Caprock by the
afternoon which will drop humidities and help boost high
temperatures. There still is some fire weather concerns, see
discussion below. Even with the uncertainty in how surface
conditions will evolve, temperatures will be a few degrees warmer
tomorrow than today as warmer air mixes in from the southwest. Lee
trough will also strengthen through the day as flow aloft becomes
increasingly southeast ahead of the next storm system that moves
west from the Pacific Northwest tonight into tomorrow.
Jordan
LONG TERM...
Upper low currently over NV will push southeastward by early
Saturday. Models still can`t agree on the exact path of this low.
The GFS continues to favor a more northerly path swinging
northeastward across the OK Panhandle into KS with the ECMWF still
favoring a more southerly path across the Permian Basin into the Big
Country. The ECMWF has been more consistent run to run that the GFS
with the handling of the upper low in which the ECMWF will have more
of an impact on the forecast allowing for high PoP chances as we get
into the late weekend particularly across our eastern zones. With
either solution a front is expected to push through the FA by Sunday
and will cool highs down into the 60s. We will quickly warm back up
by Monday as skies will be more clear and upper ridging will move in
overhead. Previously models have agreed upon a fast moving upper low
passing across the central plains Tuesday bringing a cold front
southward by Wednesday with windy conditions Tuesday ahead of the
front. Now models are agreeing on the upper low staying farther to
the north making Tuesday not so windy (not that I mind). Forecasted
winds have been lowered from the previous forecast for Tuesday but
still kept on the breezy side as the front approaches. While temps
on Wednesday should be slightly cooler because of the fropa we
should not see a significant cool down as the source region for the
front will be south-central Canada. This area will not have enough
time to recover from the cold air it let go during the previous
front.
FIRE WEATHER...
Will continue fire weather watch for Friday as there is some concern
how far east critical fire weather conditions can develop. Minimum
RH values at or below 10 percent will develop across the
southwestern South Plains with 10 to 15 percent west of roughly a
Tulia to Jayton line. Wind speeds across the Rolling Plains will be
below critical values so do not expect Red Flag conditions there.
Second concern for the South Plains are wind speeds which may not be
strong enough for a long enough period of time. Window for
sustained 20 to 30 MPH is pretty narrow and also limited to the
counties near the Texas/New Mexico state line.
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Friday afternoon through Friday evening
for TXZ021-027-028-033>035-039>041.
&&
$$
93
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
930 PM EDT Thu Mar 30 2017
.SYNOPSIS...
High pressure will move offshore tonight. Low pressure will
pass through the area Friday. High pressure will gradually
return Saturday and Sunday before another low pressure impacts
the area Monday and Tuesday.
&&
.NEAR TERM /THROUGH FRIDAY/...
Latest surface analysis shows high pressure southeast of Long
Island, wedging southward along the east side of the
Appalachians. A warm front snakes its way northwest from near
Savannah, Georgia to a low pressure in Illinois, with a cold
front extending southward to Louisiana and the western Gulf of
Mexico. Aloft, a ridge is located directly over our area, with
a closed low is centered over central Missouri.
Tonight, the surface high will slide east off the coast and the
surface low will also move east, reaching Indiana by dawn. The
warm front to our southwest will slowly push northward, reaching
southwestern Virginia and North Carolina by dawn.
So far, light showers in southwest VA have been falling apart as
they approach the CWA. That trend should change over the next
several hours as the atmosphere continues to saturate. However,
any activity should be light and isolated until after midnight.
HRRR/RAP also show showers breaking out across northern parts
of the area as the LLJ/isentropic lift increases. 00Z IAD
sounding indicates some minuscule elevated instability, and
lightning strikes have persisted with a cluster of showers
across central PA. Therefore can`t totally rule out thunder if
more robust/deeper showers develop, but have not included in the
overnight portion of the forecast for now due to limited
coverage. If RAP/HRRR timing is correct, the shield of
widespread moderate to perhaps heavy rain won`t move into the
CWA until after 5 AM.
Temperatures will drop into the 40s in most of the region with
a southeasterly upslope flow. Current forecast curve is on
track, although latest short term guidance indicates southern
areas may remain a bit warmer than currently forecast.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
Surface low pressure in the midwest will slide into western
Pennsylvania during the day Friday, with a secondary low
developing over western North Carolina and heading northeast
across our area. The two surface lows will consolidate near New
Jersey Friday evening. Aloft, the shortwave to the south of the
approaching closed low will develop a negative tilt as it slides
eastward towards us Friday, with the closed low itself then
crossing over the region overnight Friday. Both the surface and
upper level systems will move eastward away from the region
during the day Saturday.
The negatively tilted shortwave will promote significant
rainfall and perhaps a little embedded convection Friday
morning. At the very least, some periods of moderate to
occasionally heavy rain look likely given the ample moisture
flow from the south and good forcing, and soundings also suggest
some instability above the inversion. Have added slight chance
of thunder for all but northern portions of the area, although
the HRRR max lightning threat product indicates a rumble of
thunder could be possible about anywhere. While the area has
been dry, soils are significantly more moist than they were a
month ago. Thus I am a little concerned about potential for
isolated flooding, or at least significant ponding of water on
roadways. Given that right now threat seems isolated, will not
yet introduce any enhanced wording for it just yet.
Steadier rain looks likely to taper to a more showery pattern
by afternoon as the warm front tries to lift northwest into the
DC metro ahead of the approaching secondary low. Some modest
instability looks likely to develop just ahead of the cold front
which will be trailing from the secondary low, and with some
decent wind aloft, some gusty if not severe storms are certainly
possible. SPC marginal risk area looks reasonable for areas
near and south of the metro. Once again, tough to rule out
thunder just about anywhere as the upper low approaches, but the
chances will definitely increase with southeastward extent
across the area. Highs will be dependent on just how far north
the warm front gets, with 60s likely south of the front and
perhaps even 70s in the warmest spots south of the front, while
50s will hold north of it.
Showers will diminish Friday night with the surface low passing
east, but may linger as the upper low crosses the area
overnight. Temperatures will fall back into the 40s on the
northwesterly flow. The system will head off the coast and leave
a gusty but drying northwest wind for Saturday. Winds may gust
to 25-30 mph, but temperatures should be able to rebound to the
50s and low 60s. Some upslope showers will linger along the
Allgheny Front, but east of the mountains it should be dry.
All areas turn out dry for Saturday night as high pressure
pushes in from the west and the upslope flow weakens. Temps may
try to drop into the 30s in the cooler spots but the northwest
flow should stay up and prevent strong radiational cooling.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
High pressure will settle into the region Sunday through early
Monday. Dry and seasonable temperatures expected throughout the
period.
The next storm system will move into the region midday Monday
through Tuesday, bringing more rain showers to the region once
again.
Brief high pressure will build into the region Wednesday and
Wednesday night before the next storm system approaches
Thursday.
&&
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
Conditions will deteriorate through tonight as low pressure
approaches from the west. Have generally held off on the lower
cigs until after 08-09Z, leaning on model RH over MOS. Some
uncertainty with this though. Showers will be somewhat scattered
most of the night, but are expected to increase in coverage
late. Moderate to perhaps heavy rain will overspread the area
during the morning hours, with current timing suggesting it will
arrive after 12Z in the metros. IFR to LIFR likely all
terminals Friday morning before conditions relax a bit in the
afternoon as rain diminishes to showers. Increasing low level
jet could pose LLWS concerns during the morning. Some embedded
thunderstorms will be possible at just about any time, with best
odds in the afternoon. Most of the convection will be elevated,
although the CHO-DCA corridor could see some surface based
storms with gusty winds during the late afternoon.Conditions
improve slowly back to VFR Friday night into Saturday, though a
gusty NW wind will remain. Winds will diminish Saturday night.
Vfr conditions expected Sunday through early Monday. Winds
light and variable Sunday through early Monday. Mvfr to ifr
conditions midday Monday and Monday night. Winds southeast 5 to
10 knots midday Monday and Monday afternoon becoming northeast 5
to 10 knots Monday night.
&&
.MARINE...
Southeasterly flow is beginning to increase a bit, especially on
the southern waters. Main headline change was to add the middle
Potomac to the SCA through the night, as the southeasterly
channeling is causing gusts of 20 kt to reach Dahlgren. Approaching
low pressure will bring southerly winds across the waters, with
gusts increasing to SCA (20-30 knots) as we head through
tonight and Friday. Winds may especially increase Friday
afternoon, so will be expanding the SCA to include the upper
Potomac. It`s not out of the question winds could briefly
approach gale force, but mixing should be limited. A better
chance for strong winds will come with potential thunderstorms
crossing the waters later in the day. Showers diminish and
winds shift NW behind the front Friday night, with SCA gusts
remaining possible behind the system Saturday.
No marine hazards expected Sunday through Monday night. Winds
northwest 5 to 10 knots Sunday through Monday. Winds becoming
northeast 5 to 10 knots Monday night.
&&
.TIDES/COASTAL FLOODING...
An onshore flow will increase tonight into Friday as high
pressure continues to move offshore. Low pressure will pass
through the area Friday night. The onshore may increase ahead of
this system.
Elevated water levels are expected later tonight through Friday
night and minor tidal flooding is likely near times of high
tide. Coastal flood advisories are likely starting with the
morning high tide cycle. Water levels this evening have been
staying near the forecast curve, so we should stay below minor
flood at DC SW Waterfront on the upcoming cycle.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until midnight EDT Friday night for
ANZ531-532-539>541-543.
Small Craft Advisory from noon to 6 PM EDT Friday for ANZ538.
Small Craft Advisory from 6 AM Friday to midnight EDT Friday
night for ANZ530-542.
Small Craft Advisory until midnight EDT Friday night for
ANZ533-534-537.
Small Craft Advisory until 6 PM EDT Friday for ANZ536.
&&
$$
SYNOPSIS...RCM
NEAR TERM...ADS/RCM
SHORT TERM...ADS/RCM
LONG TERM...KLW
AVIATION...ADS/RCM/KLW
MARINE...ADS/RCM/KLW
TIDES/COASTAL FLOODING...LWX
Area Forecast Discussion
National Weather Service Nashville TN
914 PM CDT Thu Mar 30 2017
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Existing line of convection is still situated west of BNA.
Overall, the cells are weakening and eastward progression is
agonizingly slow. The severe threat has significantly diminished
as we head into the late evening. Will make a few adjustments to
POP`s and wx grids to take into account current position of the
convection and HRRR projections over the next few hours.
&&
.AVIATION...
00Z TAF DISCUSSION.
BNA/CKV/CSV...Line of storms has finally entered Middle Tennessee
with scattered cells popping up out ahead of the organized
convection. Surface winds remain brisk, and have even included a
LLWS remark at CSV for this evening owing to even stronger above-
surface winds. Have timed the TEMPO groups for TS according to the
HRRR. Expect MVFR ceilings on the back side of this system
tomorrow before the moisture finally pulls out.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......08
AVIATION........08
Area Forecast Discussion
National Weather Service Reno NV
818 PM PDT Thu Mar 30 2017
.UPDATE...
Light and fast moving showers will diminish through evening with
only a few areas of showers continuing into early Friday morning
across Mono and Mineral counties. Winds have also fallen below
Advisory and Warning criteria across most areas and have expired
all wind statements as a result. However, a stiff surface gradient
will remain in place tonight and widespread northwest winds gusts
of 30 to 40 mph will still be possible area wide.
&&
.PREVIOUS DISCUSSION... /Issued 252 PM PDT Thu Mar 30 2017/
SYNOPSIS...
A strong cold front brought snow showers and high winds to the
region Thursday. Weather should quiet down with warming temperatures
through the weekend. Gusty winds and light rain are possible Sunday
night with a passing storm. Potential exists for a stronger Pacific
storm late next week, but impacts and flood potential remain low
confidence this far out.
SHORT TERM (through Sunday night)...
Spring in the Great Basin can be quite variable and we definitely
saw a remnant of winter today. Strong cold front brought a classic
snow squall scenario around the morning commute but fortunately road
temperatures were warm enough to melt much of it, outside of the
mountains where more of an impact was seen. Winds gusted above 50
mph and temperatures dropped 10-15 degrees in less than 20 minutes.
Here are the key points for the coming days...
* Winds Today - Very impressive pressure gradient over Nevada.
HRRR showing pressure drops with low near Las Vegas over 1- 2
MB/hour! This will prompt a resurgence of strong sustained winds
across our region through early evening, with highest risk of
damaging winds in areas south of Hwy 50 including Hawthorne,
Mammoth, Owens Valley.
* Ridge/Lake Winds Friday - Winds should diminish later this
evening as the low moves eastward but remain somewhat gusty into
Friday. On the Sierra ridges, NE winds will remain stronger
Friday with 700mb flow 40-50kts. Rough waters possible on Lake
Tahoe especially west shore with mixed layer up to about 700mb
by afternoon.
* Snow Showers This Evening - Airmass behind the cold front is
moderately unstable resulting in continued snow showers.
Accumulations until sundown will be sporadic and limited to
areas above 6000` due to late March solar energy. Latest HRRR
shows showers persisting over Mono-Mineral Counties this evening
with weak instability aloft, so will note that in forecast.
Could be some localized and quick snow accumulations.
* Weekend - Should be a pleasant spring weekend for the most part
with gradually warming temperatures each day Fri-Sun. Sunday has
potential to get warm as low level flow switches from cool NE on
Sat to a warmer SW flow Sun. Increased lower elevation snowmelt
will result which may yield slight increases in stream, river
flows.
* Sunday Night "Wanna Be Slider" - Simulations have been consistent
showing another front dropping in from the NW Sun night. Has the
look of a slider but the wave isn`t as sharp as today`s and scoots
off to the east. Main results for our region are typical gusty SW
winds starting late Sun afternoon, and a band of rain or snow
showers near the front Sun night. Right now, system looks warmer
than today`s with precip type mainly rain except in mountains, so
travel impacts appear low.
-Chris
LONG TERM...Monday into next weekend...
The system exits quickly on Monday, with a ridge building over
northeast California and western Nevada for Monday night into
Wednesday. Afternoon temperatures near average Monday will rise to
well above average by mid-week as the ridge axis moves overhead.
Thursday, the ridge slides east and allows a lead wave with a
large-scale North Pacific trough to move into the West. The most
recent ECMWF simulation and last two runs of the GFS indicate a
weak lead wave with only minor precipitation amounts, while
yesterday`s ECMWF shows a stronger wave and more direct hit from
an atmospheric river (AR) by Thursday night. Moisture transport
simulations from the GFS ensemble only indicate a moderate
probability of AR conditions near the northern CA coast Thursday
night. With this in mind and the fact that recent AR probabilities
have backed off on probabilities through Thursday, confidence is
wavering for substantial precipitation through Thursday night.
For next Friday and into the following weekend, it is likely that
the AR will finally move into the West Coast. Current forecasts
favor the Pacific Northwest; however, intensity and especially
latitude are still in the realm of lower predictability with the
main question revolving around how far south the moisture and jet
stream drop. Increased chances are not a guarantee, but definitely
worth keeping an eye on as a direct hit from another AR would
again increase flooding concerns in the region. Snyder/Tolby
AVIATION...
Scattered snow showers will dissipate this evening with the loss
of daytime heating and the exit of the upper low (into southern
NV). Lower clouds and widespread higher terrain obscuration should
begin to break up this evening for most of northeast CA and
western NV, although lower clouds (generally 095-120 MSL) along
with occasional light snow showers could remain banked up against
the Mono County Sierra through most of the night.
Ridging builds in Friday and persists through Saturday for VFR
conditions with light-moderate northerly flow. The flow could
bring turbulence along and west of the Sierra crest. Snyder
&&
.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory from 10 AM to 6 PM PDT Friday for Lake Tahoe
in NVZ002.
CA...Lake Wind Advisory from 10 AM to 6 PM PDT Friday for Lake Tahoe
in CAZ072.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service San Diego CA
145 PM PDT Thu Mar 30 2017
...Severe and potentially damaging winds this afternoon and evening
over the mountains and deserts...
.SYNOPSIS...
Strong to severe winds will impact the deserts this afternoon and
evening as a powerful low pressure trough moves across the Great
Basin. The winds will decrease tonight. Cooler Friday behind the
trough with winds shifting to the northeast. High pressure
rebuilding over the region Saturday will bring sunny and warm
weather this weekend. Cooler early next week as another trough moves
in from the northwest.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Strong winds are surfacing in the High Desert this afternoon where a
62 mph wind gust was recorded at Barstow-Daggett Airport at 1 pm.
Burns Canyon had a gust to 67 mph.
A dynamic 546 dm upper low over western Nevada is digging south with
an incredibly strong 300 mb 150kt jet over northern California.
Convection has formed along and ahead of the surface cold front in
Nevada. The atmosphere down here is too dry, but the winds will be
very strong. 850 mb winds of 50-60 kt over the Mojave Desert will
shift southeast through evening. The high rez HRRR and WRF models
project the peak surface winds of 25-35 mph with gusts of 70 mph to
surface between 2-7 pm in the High Deserts. Even stronger gusts are
possible where mountain waves surface on the eastern slopes of the
SBD mountains. Burns Canyon may gust to 80 mph.
Some of this wind energy will also surface in parts of the Coachella
Valley and the San Diego County Deserts where gusts of 50-60 mph are
possible. Strong cross winds and reduced vis in blowing dust and
sand will create hazardous travel conditions. A High Wind Warning is
in effect through 11 pm this evening.
Onshore flow and a coastal eddy brought low clouds to the coastal
areas this afternoon. The clouds will spread a few miles inland
inland this evening, perhaps into the San Diego Valleys, before
retreating back to the coast early Friday morning as offshore flow
fills in behind the trough passage.
The deep upper low will be over northern AZ tonight and the winds
will shift from the west to the north through Friday morning. A
period of gusty north winds Friday morning will mainly impact the
lower deserts, the Cajon Pass and the Santa Ana mountains.
The trough slowly moves east over the weekend followed by ridging
and moderating temperatures Saturday and Sunday. An inside slider
trough will bring cooling Monday and Tuesday and gusty northwest
winds in the mtns and deserts, but much weaker than today.
A more pronounced ridge builds in Wednesday and Thursday for warmer
days. Temperatures will be way above average with coastal highs in
the 70s, valley highs in the 80s, mountain highs in the 60s, high
desert highs in the 80s and lower desert high in the 90s.
Long range outlook for late next week: A zonal Pacific jet will
break down the ridge with bring rain to Norcal, but at this time it
doesn`t look like it will dig deep enough to bring rain to Southern
California.
&&
.AVIATION...
302000Z...Areas of low clouds and fog along the coast this afternoon
will spread 5-10 miles inland through 06Z Fri...mostly in San Diego
County. Expect bases 1000-1500 ft MSL and tops to 2000 ft MSL. Vis
restrictions are likely where clouds and terrain intersect. Low
clouds could spread inland to the coastal slopes by 06Z, before
northeast to east winds develop and begin to clear out the low
clouds. Otherwise, mostly clear skies through tonight.
Mountains and deserts...areas of winds 25-35 KT with gusts 40-50 KT
this afternoon through tonight near mountain crests, desert mountain
slopes and some lower elevation desert locations. Strong and
variable winds are expected at KPSP and KTRM, with peak winds likely
between 23-04Z this afternoon/eve. Strong up/downdrafts and LLWS
will occur over and east of the mtns, with isolated vis reductions
in blowing dust/sand in the deserts. Winds will diminish after 09Z
Fri.
&&
.MARINE...
Strong west to northwest winds are developing this afternoon and
will continue into early Friday, particularly in the outer coastal
waters. A small craft advisory contains the details on winds and
seas. In portions of the outer waters, winds will gust over 30 knots
at times and combined seas could exceed 10 feet. Winds and seas will
diminish Friday morning. No hazardous marine weather is expected
through Sunday, but strong winds could return Monday.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Warning until 11 PM PDT this evening for Apple and
Lucerne Valleys-Coachella Valley-Riverside County Mountains-
San Bernardino County Mountains-San Diego County Deserts-
San Diego County Mountains-San Gorgonio Pass Near Banning.
PZ...Small Craft Advisory until 8 AM PDT Friday for Waters from San
Mateo point to the Mexican Border Extending 30 to 60 nm out
including San Clemente Island.
&&
$$
PUBLIC...Moede
AVIATION/MARINE...PG