Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/20/18
Area Forecast Discussion
National Weather Service La Crosse WI
1100 PM CDT Wed Sep 19 2018
.SHORT TERM...(This evening through Thursday night)
Issued at 246 PM CDT Wed Sep 19 2018
This will be a very active period across the region. Surface
analysis this afternoon shows a warm front across northern
Missouri with an area of low pressure over eastern Colorado.
Surface dew points have climbed into the lower 70s along and south
of the warm front. This warm front will be a major player for
tonight as a short wave trough coming out of the Rockies this
afternoon moves over the region and interacts with the front. The
low level moisture transport will rapidly increase this evening
ahead of the approaching short wave trough with several runs of
the RAP suggesting this will be focused over northeast Iowa into
southwest Wisconsin. With the forcing from the short wave trough,
expecting to see convection develop late this afternoon over
southwest Minnesota and rapidly develop east/southeast and become
focused on the nose of the low level moisture transport. These
features do not look to change much until late tonight when the
moisture transport looks to weaken and move off to the east.
Unfortunately, this set up looks to have a east/west line of
showers and storms over the southern portions of the area for a
good share of the night with a heavy rain/flash flood threat. More
information on this in the hydrology section below.
Once the short wave trough and moisture transport move off to the
east Thursday morning, the focus will quickly shift back to the
west with the next incoming short wave trough. This wave looks to
be much stronger and bring in a round of moderate pv advection in
the 500-300 mb layer late Thursday afternoon and evening. As this
wave approaches the region, the moisture transport will rapidly
refocus west of the area ahead of the approaching cold front. This
should then spread north/northeast ahead of the front and short
wave trough into eastern Minnesota and northern Wisconsin. This
will help to push the warm front into the area and the concern
becomes how far north this will progress. The atmosphere south of
the warm front looks like it will become capped off with only some
scattered storms possible. A surface low will translate north
along the cold front and create a triple point as it drags the
warm front north with. Right along the warm front, the 19.12Z NAM
shows up to 2000 J/Kg of ML CAPE in place from southeast Minnesota
into western Wisconsin during the late afternoon and evening. In
this area, there will be lots of shear to work with. 0-3 km values
should be on the order of 40 to 45 knots with almost all of this
residing in the lowest 0-1 km layer. The shear does continue to
increase with height with 50 to 55 knots along and north of the
warm front. As the convection develops in the afternoon, there is
the possibility of some discrete cells that will pose a tornado
threat before the activity forms into a more linear structure.
Once this happens, the main threat will transition to damaging
winds, but due to the large amounts of low level shear, there will
continue to be a threat for embedded tornadoes. SPC has already
upgraded the outlook for Thursday to enhanced north of the cap.
All this activity will then come to an end Thursday night as the
cold front sweeps across the region with the short wave trough.
While there could be some periods of heavy rain with the storms
Thursday afternoon/night, these look to be progressive enough to
not pose much of a flooding threat. However, that could and will
need to be revisited after the rain tonight.
.LONG TERM...(Friday through Wednesday)
Issued at 246 PM CDT Wed Sep 19 2018
Once the system moves by the area Thursday night, the upper level
flow looks to go zonal through the weekend until another trough
moves across the Upper Midwest to start next week. This system
looks to push a cold front across the region with a chance for
some showers and a few storms Monday and Tuesday. Temperatures
will be cooler for this entire period with highs generally in the
60s to lower 70s with overnight lows mainly in the 45 to 55 range.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1100 PM CDT Wed Sep 19 2018
Wet, stormy period with cold/warm front interaction with upper level
shortwaves and a summery airmass to fire periods of showers and
storms through Thu evening. Heavy rain with the stronger storms with
potential for strong/severe storms late Thu afternoon/evening.
Cigs: expect generally around and sub 1kft through Thu morning, with
some improvement to potentially VFR later THU afternoon as a warm
front lifts north of the TAF sites. IFR/MVFR (LIFR?) could return
post the passage of the cold front for Thu night - GFS/NAM/RAP all
suggest a saturated 0.5-1 km layer would sink southward post the
front. Something to watch. Won`t add to forecast for the moment.
WX/vsby: radar trends continue to hold most of the heavy rain/ts
threat south of I-90 and south of the TAF sites. Matches well with
NSSL WRF and HRRR starting to pick up on it. Could leave KRST/KLSE
mostly with shra and isold T. May trend forecast this way, shra with
vcts. Expect reductions mostly 2-4SM.
Pcpn will lighten up later Thu morning, with a break in the
afternoon before a line of strong (severe?) storms roll in with a
cold front Thu evening. Expect more reductions - although more brief
- with these storms.
Winds: generally southeast into Thu afternoon, swinging southwest
then northwest overnight THU with the passage of a cold front. Winds
will pick up quite a bit by Thu afternoon (some higher gusts) with
likely some enhanced gusts around any thunderstorm.
&&
.HYDROLOGY...
Issued at 246 PM CDT Wed Sep 19 2018
No additional changes were made to the flash flood watch. As the
storms get going this evening and overnight, they will be working
in excellent conditions to produce repeated rounds of heavy rain.
The band is expected to lay out east/west on the nose of the low
moisture transport with the models continuing to show a strong
band of low moisture convergence across northeast Iowa into
southwest Wisconsin. An axis of 2+ inches of precipitable water
should reside from southern Minnesota across northeast Iowa into
southwest Wisconsin where warm cloud depths will be in the 4 to
4.5 km range. Conservatively forecasting a axis of 2 to 3 inches
of rain from about the Austin area east/southeast toward the
Viroqua and Richland Center areas. Fully expect that there will be
much higher local rainfall totals that could be near or exceed 6
inches. Expecting flash flood warnings to be issued tonight and
the severity of the flooding will depend on the rainfall amounts.
This flash flooding will then transition into areal and river
flooding that will likely impact the Upper Iowa, Turkey, Kickapoo
and Pine River basins. Forecasts for some of these sites based on
early qpf forecasts were already suggesting a high likelihood of
flooding and river flood warnings also look to be needed from this
event.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Flash Flood Watch from 7 PM CDT this evening through Thursday
afternoon for WIZ032>034-041>044-053>055-061.
MN...Flash Flood Watch from 7 PM CDT this evening through Thursday
afternoon for MNZ079-086>088-094>096.
IA...Flash Flood Watch from 7 PM CDT this evening through Thursday
afternoon for IAZ008>011-018-019-029-030.
&&
$$
SHORT TERM...04
LONG TERM...04
AVIATION....Rieck
HYDROLOGY...04
Area Forecast Discussion
National Weather Service Bismarck ND
917 PM CDT Wed Sep 19 2018
.UPDATE...
Issued at 917 PM CDT Wed Sep 19 2018
The short-term forecast remains on track. Future updates may need
to slow down the arrival times of likely PoPs across southern ND,
but left as is for now.
Made a few minor adjustments to the Thursday afternoon into Friday
morning timeframe. The first concern is the potential for snow
mixing in with rain Thursday evening as both diabatic and
advective processes cool the boundary layer into the 30s. Think
that for any given location, by the time thermal profiles would
cool enough for snow to reach the surface, much of the
precipitation will have concluded. However, there does appear to
be some potential for dynamic cooling. Do have a bit of rain mixed
with snow mentioned in the forecast for parts of western North
Dakota, but do not expect this to be a widespread occurrence.
The second concern involves the potential for frost Thursday night
into Friday morning. It will greatly depend on how quickly clouds
dissipate and where the center of the surface high winds up.
Recent guidance suggests that cloud cover will hold on across much
of western and central ND until at least 06-09Z, which would
allow only a few hours at most for strong radiational cooling.
Raised low temperatures Thursday night by a degree or two and
trended somewhat away from widespread/areas of frost mention. Will
let the next shift evaluate 00Z guidance before making further
adjustments.
UPDATE Issued at 652 PM CDT Wed Sep 19 2018
No major changes for this update. Blended in current obs and
short-term forecast guidance.
Over the last hour, a weakening trend has been observed in the
showers streaming across northeast MT into far northwest ND.
These showers appear to be tied to weak mid-level frontogenesis,
which latest runs of the RAP indicate will continue to weaken this
evening.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 330 PM CDT Wed Sep 19 2018
Chances of showers and amounts of expected rainfall are the main
concern in this short term period...followed by possible frost
Thursday night into Friday morning.
Cool high pressure was center over the Saskatchewan/Montana/ND
border this afternoon, with a large and deepening low pressure
system over the central Plains - centered over eastern Colorado. At
upper levels, a West Coast trough continued to deepen, with
southwest flow aloft set up over the US Rockies and fairly zonal
flow aloft over the Northern Plains. Some light rain showers
continued over northeastern Montana into northwestern North Dakota,
associated with some upper level impulses moving east in the zonal
flow aloft.
Tonight:
The upper level West Coast trough continues to dig as it moves east
across the Rockies, with the leading edge of its stronger upper
level impulses reaching far southwestern North Dakota by around
midnight tonight, then continuing north and east. Meanwhile at the
surface, a warm front develops northeastward tonight from the
Colorado low as a low level jet develops over the southern Plains
into the central US Plains. The surface low and warm front move
northward, the low center reaching into central Nebraska and the
warm front reaching into southern Minnesota by daybreak Thursday
morning.
Thursday:
The base of the upper level trough lifts northeastward into the
Dakotas through the day. The surface low develops northeastward
along the warm front, crossing southern Minnesota into Lake
Superior. Thus North Dakota remains on the cooler side of the
system, with increasing easterly winds becoming northeasterly, and
finally northerly by Thursday evening. Plenty of upward motion with
this system over our area, with h500-300 Q vector divergence and
h700-500 lapse rates of 4-6 C/km and plenty of low level isentropic
lift.
Thursday night:
The upper level trough moves east across the Dakotas into Minnesota
by daybreak Friday morning, with a cold surface Canadian high
pressure system following the exiting system. Low temperatures are
forecast to drop into the 30s for much of western and central North
Dakota. Areas where precipitation is lingering as cold air moves in
may see a rain/snow mix develop briefly. Radiational cooling where
cloud cover clears with the post-frontal surface high will become an
issue for frost/freeze conditions Thursday night as well.
Regarding rainfall:
Expecting best chances of rain showers beginning in southwestern ND
after midnight tonight, spreading north and east across western and
southern North Dakota. Daytime Thursday appears to be the time of
highest precip chances and the time when the highest amounts of
rainfall will occur. By Thursday evening, the better precip amounts
lift northward across northern and eastern ND, before tapering off
from west to east after midnight. Storm totals tonight through
Thursday night appear to be in the 1/2 inch to 1 inch range for most
of western and central North Dakota. There may be some locales that
receive more than an inch, and some areas that receive less than 1/2
inch...but for the most part this should be a widespread rain event
with nearly all areas receiving some decent amounts of rainfall.
.LONG TERM...(Friday through Wednesday)
Issued at 330 PM CDT Wed Sep 19 2018
Cooler and dry conditions on Friday with high temperatures in the
50s.
Zonal flow aloft Saturday, with some upper level impulses moving
east across northern ND. This will bring small chances of rain
showers across the north with cooler conditions - highs Saturday in
the 50s north, while 60s and lower 70s are forecast for southern ND.
On Sunday another longwave trough digs across the northern Rockies
into the Northern Plains, bringing off and on chances of showers to
most of North Dakota Sunday through Wednesday. Highs mainly in the
50s to lower 60s this time period, with lows mainly 35 to 45.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 652 PM CDT Wed Sep 19 2018
Widespread rain will develop from southwest to northeast across ND
late tonight into Thursday morning, lasting through the afternoon.
Expect ceilings to lower to MVFR levels mid to late morning, with
further lowering to IFR at KDIK, KJMS, and perhaps KBIS. Periods
of MVFR and possibly IFR visibility may occur in heavier rain
showers. Northeast winds around 5-10 kts tonight will increase to
10-15 kts by Thursday afternoon.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Hollan
SHORT TERM...JV
LONG TERM...JV
AVIATION...Hollan
Area Forecast Discussion
National Weather Service Columbia SC
1028 PM EDT Wed Sep 19 2018
.SYNOPSIS...
High pressure will build in from the west through Friday
bringing dry and warm conditions. Moisture will return early
next week as an onshore flow develops.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
High pressure centered over the TN Valley will build into the
region through tonight. Dewpoint temperatures have dropped into
the 60s in most locations across the area. Low temperatures
tonight will fall into the mid and upper 60s under mainly clear
skies.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
High pressure at the surface and aloft will control our weather
for the end of the work week. Increasing H5 heights and overall
atmospheric subsidence will lead to mostly clear skies and
continued above normal temperatures.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
High pressure aloft moves off the Southeast U.S. coast this
weekend which allows for an onshore flow into the Carolinas and
Georgia. The region may see diurnal showers and thunderstorms
early next week. Above normal temperatures will continue through
Tuesday.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
We have high confidence in VFR conditions through the 24-hour
TAF period outside of possible early morning fog at AGS and OGB.
High pressure has directed dry air into the region. Expect
mostly clear skies. There may be enough low-level moisture
combined with nocturnal cooling for a period of fog mainly at
the river valley terminals of AGS and OGB around sunrise.
However, we maintained VFR conditions based on the dry air mass
and much of the NAM and GFS MOS, SREF, and HRRR guidance. The
MOS supports winds north to east less than 10 knots.
EXTENDED AVIATION OUTLOOK...An onshore flow should bring
increased low-level moisture with an increased chance of late
night and early morning stratus and fog.
&&
.HYDROLOGY...
Record rainfall fell across the Pee Dee basin, with over 20
inches in parts of Chesterfield County. Flooding is occurring
along the Great Pee Dee River at Cheraw and will continue
through Thursday night.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
SYNOPSIS...99
NEAR TERM...99
SHORT TERM...99
LONG TERM...99
AVIATION...99
HYDROLOGY...
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
834 PM CDT Wed Sep 19 2018
.UPDATE...
Showers and thunderstorms have left the CWA "cooler" than surrounding
CWAs at mid-evening. Radar estimates from convection just west of
Langtry indicate 5+ inches of rain may have fallen this afternoon and
evening. The West Gulf River Forecast Center believes the runoff may
bring the Rio Grande at Langtry to minor flood stage by daybreak.
This is a harbinger of things to come over the next 4-5 days, as a
series of troughs, along with moist air from the Pacific and Gulf,
combine to bring rain to all of South Central Texas. Recent HREF and
HRRR ensembles, and the latest Texas Tech WRF, all show convection
slowly waning overnight, although the primary axis of convection is a
little further east in reality that the model forecasts. We updated
the forecast to nudge PoPs a little further east, but keep them on
the Rio Grande Plains and Edwards Plateau. Otherwise, we re-trended
hourly values through 12Z Thursday to match observed and expected
trends.
&&
.PREV DISCUSSION... /ISSUED 642 PM CDT Wed Sep 19 2018/
AVIATION...
VFR conditions will prevail at all area airports through the evening.
There is a small cluster of thunderstorms to the west of San Antonio
moving toward the northwest. These storms should stay out of SAT and
SSF, but we`ve included VCSH since they are inside 10NM. There are
also thunderstorms in Mexico west of DRT and these should stay west.
Ceilings will lower to MVFR overnight at all terminals and recover to
VFR by around noon Thursday. There will be chances for showers and
thunderstorms during the day Thursday, but chances remain low.
Chances will increase after 00Z Friday.
PREV DISCUSSION... /ISSUED 303 PM CDT Wed Sep 19 2018/
SHORT TERM (Tonight through Thursday Night)...
The current mid to upper level pattern is characterized by broad
troughing across the western CONUS with a smaller shortwave trough in
the vicinity of Baja California with strong ridging across the
central CONUS. Today`s forecast is on track, with highs expected to
top out in the upper 80s to low 90s this afternoon. Moisture is on
the increase across the region, with source locations being both the
eastern Pacific as well as the Gulf of Mexico. Moistening across the
Rio Grande region tonight will yield a slight chance for showers and
thunderstorms. Otherwise, tonight will be mild with clouds on the
increase, moderating overnight lows.
PoPs will be on the increase for tomorrow as precipitable water
values increase further and weak upper level forcing from the
approaching troughs generates scattered showers and thunderstorms.
Models suggest the most favorable location for the possibility of
locally heavy rainfall will be along the Rio Grande and into the
southern Edwards Plateau region tomorrow afternoon and continuing
into the evening and overnight hours. High temperatures tomorrow
likely wont get out of the 80s with the cloud cover, increased
moisture, and the residual wet soils from the past two weeks of heavy
rain.
LONG TERM (Friday through Wednesday)...
Scattered to widespread showers and thunderstorms will continue for
Friday and Saturday, and these chances will spread north and eastward
to include all of South Central Texas. Given the very high
precipitable water values, tall and skinny CAPE profiles, and high
wet bulb zero values, locally heavy rainfall will be possible as
these showers/storms could be very efficient rain producers. With
the heavy rainfall that has impacted the region in the month of
September, there could be a localized flash flooding threat.
Rain chances will still exist for Sunday through Tuesday, but chances
will be lower than Friday and Saturday and the focus will shift more
toward the eastern half of the region. The locally heavy rainfall
threat will also diminish during this time period.
Models diverge a bit as we head into the end of the forecast period.
The GFS brings a strong cold front completely through the region
late Wednesday night into Thursday morning while the ECMWF shows the
front not coming through the region until late Thursday into Friday
morning. However, both models depict showers and thunderstorms along
and ahead of the frontal passage.
High temperatures for Friday through next Wednesday will be below
seasonal normals with not much diurnal range due to warmer overnight
temperatures due to persistent cloud cover and rain chances.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 74 88 74 86 74 / - 30 40 60 60
Austin Bergstrom Intl Airport 74 88 75 86 74 / - 30 40 60 60
New Braunfels Muni Airport 74 88 75 86 74 / - 40 40 60 60
Burnet Muni Airport 72 86 73 84 71 / 0 30 40 60 60
Del Rio Intl Airport 74 85 75 86 72 / 20 40 50 60 60
Georgetown Muni Airport 74 88 74 86 72 / 0 30 40 60 60
Hondo Muni Airport 74 88 74 85 73 / 10 40 60 60 60
San Marcos Muni Airport 74 88 74 86 73 / - 40 40 60 60
La Grange - Fayette Regional 75 90 76 88 75 / - 40 40 60 50
San Antonio Intl Airport 75 88 75 86 74 / - 40 50 60 60
Stinson Muni Airport 76 89 76 87 75 / 10 40 50 60 60
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale/Aviation...05
Synoptic/Grids...26
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
115 PM PDT Wed Sep 19 2018
.SYNOPSIS...An upper level trough will slowly move east of the
area tonight, but keep breezy to locally windy conditions through
this evening across portions of the Kern County Mountains and
Deserts. High pressure will push inland into the state on
Thursday and bring a warming trend to the area on Thursday and
Friday. Temperatures will then remain above seasonal normals
through the weekend and well into next week while dry weather
continues.
&&
.DISCUSSION...An upper trough is slowly pushing eastward across
CA today. This trough is moisture deficient as satellite imagery
is indicating clear skies prevailing across our CWFA. High
pressure is nudging into CA behind the departing trough and a
warming trend is already taking place across our area as
temperatures are generally running 2-4 DEG F above yday at this
time.
HRRR indicating locally strong wind gusts are possible through
this evening in the Kern County Mountains and Deserts as onshore
p-grads strengthen. With the trough moving into the Great Basin by
Thursday and high pressure building into central CA, p-grads will
relax and winds will diminish. With ridging in store for Thursday
and Friday, temperatures will continue their upward trend across
the area with heights and thicknesses rising.
The medium range models are in good agreement with retrograding
the ridge offshore slightly this weekend while and upper low
slides underneath it and forms a rex block between 130W and 140W.
This will result in mainly clear skies and continued dry
conditions prevailing across our area along with above normal
temperatures from this weekend through at least the middle of
next week.
&&
.AVIATION...VFR conditions can be expected throughout the Central
California Interior for at least the next 24 hours.
&&
.AIR QUALITY ISSUES...None.
&&
.CERTAINTY...
The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is medium.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.php for additional information
an/or to provide feedback.
&&
.HNX Watches/Warnings/Advisories...NONE.
&&
$$
public...DS
avn/fw...BSO
synopsis...DS
weather.gov/hanford
Area Forecast Discussion
National Weather Service Wilmington NC
Issued by National Weather Service Charleston SC
1029 PM EDT Wed Sep 19 2018
.SYNOPSIS...
High pressure will persist through tonight. A weak front will
drop through the area Thursday afternoon, followed by high
pressure through Saturday. The high will shift offshore over the
weekend, bringing increasing moisture and rain chances by
Sunday.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 1025 PM: I will update the forecast to add patchy fog
across the inland counties. Otherwise, the current forecast
appears in good shape.
As of 720 PM: Guidance indicates that lower sfc condensation
pressure deficits will slide from the near shore waters across
the Coastal Plain of SC, HRRR expands the low values across the
inland NC zones as well. Lower dewpoints across the terminals
may keep dewpoint depression at least 1 to 2 degrees through the
night. The latest run of the LAV guidance keeps conditions
clear of vis restrictions overnight. However, given the overall
wet conditions across the terminals, clear sky, and light to
calm winds the potential for fog certainly exist. I will watch
trends in latest MOS and observations this evening, At this
time, I will keep the forecast free of fog.
As of 6 PM: Satellite indicated very shallow Cu across the CWA,
with slight enhancement along a weak sea breeze. The Cu should
dissipate within an hour or two following sunset. I will update
the forecast to adjust sky cover and align near term
temperatures with observations.
Previous Discussion:
Tonight: The large upper ridge aloft centered over the lower
Mississippi Valley will continue to build eastward, encompassing
the Southeast by Thursday morning. Dry high pressure will
continue to build in from the north at the surface, producing
quiet conditions across the forecast area. Lows are forecast to
fall into the upper 60s in most areas, with a few mid 60s
possible well inland. Some model guidance hints at fog
potential, but dewpoint depressions should be sufficiently large
to preclude much fog development. If patchy fog develops
anywhere it should be down south near the Santee River.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
A relatively quiet period is in store as a broad upper level
ridge expands over the eastern United States. A weak backdoor
cold front is expected to drop through the area Thursday
afternoon. Despite a relatively dry airmass in place ahead of
the front, most of the models show a slug of moisture along and
ahead of the front with a few hundredths of QPF possible. There
should be enough surface-based instability to support a couple
showers/tstms. We included a slight chance PoP late Thursday
afternoon over central and southern inland areas where the
greatest instability will be present. Otherwise, dry weather
will prevail Thursday through Saturday with highs in the
mid/upper 80s.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
The deep layered ridge will shift east and setup over the
western Atlantic Saturday night through Wednesday. A deep
onshore flow will result, bringing greater moisture into the
area. Though most of the shortwave energy will be deflected
around the ridge to our west, robust daily sea breeze activity
should spur at least scattered showers and tstms each day.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Guidance indicates that lower sfc condensation pressure deficits
will slide from the near shore waters across the Coastal Plain
of SC, HRRR expands the low values across the inland NC zones as
well. Lower dewpoints across the terminals may keep dewpoint
depression at least 1 to 2 degrees through the night. The latest
run of the LAV guidance keeps conditions VFR. However, given the
overall wet conditions across the terminals, clear sky, and
light to calm winds the potential for fog certainly exist. I
will keep the 0Z TAF VFR and will watch observations and latest
MOS trends closely. Otherwise, expecting a weak ridged high
will supply light NE winds through Thursday morning, veering to
SE during the afternoon.
Extended Outlook...MVFR or lower ceilings/vsby possible at all
terminals during nighttime hours due to low clouds and/or fog.
Low chances for convection through Saturday, then scattered
showers/tstms mainly during the daytime hours starting Sunday
which could cause brief flight restrictions.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
Tonight: As dry high pressure prevails, quiet conditions are
expected through the night. Light northerly flow is expected
through most of the night, with winds increasing to around 10
knots late. Seas are forecast to range 1-2 feet.
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Northeast flow expected Thursday through Friday night as high
pressure builds south. Conditions expected to remain below
advisory thresholds.
LONG TERM /SATURDAY THROUGH SUNDAY/...
Northeast winds will become southeast by Saturday night as the
surface high over the Mid-Atlantic region shifts east. No flags
anticipated.
&&
.TIDES/COASTAL FLOODING...
A Coastal Flood Advisory has been issued for the downtown
Wilmington tide gage for the evening high tide. Extratropical
forecast guidance indicates that there is a chance the tide
could approach 6.7 feet MLLW (Moderate Flood Stage), and there
is a low end chance the advisory will need to be upgraded to a
warning. For now, we expect the tide to peak between 6.2-6.6
feet MLLW around 645 pm EDT.
Minor flooding will be possible around the times of high tide
through the end of the week due to elevated tides and an
increasing flow of inland freshwater through the Cape Fear
River. Coastal flooding will be the most likely along the Lower
Cape Fear River near downtown Wilmington.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
837 PM CDT Wed Sep 19 2018
.UPDATE...
836 PM CDT
The main change to the forecast was removing precip chances for
most of the night. Radar trends indicate convection over Iowa will
continue to shift northeast, and the latest RAP analysis
indicates a stable layer over northern IL. Near term models also
suggest that most of the night should be dry. Some models continue
to suggest showers and storms may reach the Rockford area and
other areas along the IL/WI state line late tonight into Thursday
morning. I left chance or lower precip chances over these regions,
but my overall confidence is low in timing and coverage.
Only other concern is wind gusts may be stronger Thursday. Raised
wind gusts to 25-30 MPH.
JEE
&&
.SHORT TERM...
313 PM CDT
Through This Evening...
Main forecast concerns/challenges are with shower/thunderstorm
trends this afternoon into this evening, and once again later
tonight into Thursday morning.
Latest radar trends showing the precip shield which has been
approaching the CWA today now in place across north central IL,
along and west of I-39. This area of precip will likely continue
to push further east over the next several hours, but likely
staying similar with coverage and intensity. Thunder has remained
limited with this precip, though isolated thunder will still
likely remain possible as it moves into remaining areas in
northern IL, along/north of I-88, this afternoon.
A boundary situated across the southern portions of the CWA in
east central IL/IN is providing widely varying conditions over the
area, with conditions south of the boundary now quite unstable.
Will need to keep an eye on this location for possible isolated
thunderstorm development this afternoon into the evening for a
couple of reasons. First, satellite trends have shown expanding CU
development along/south of the Kankakee river valley. Steep low
level lapse rates now in place, with latest RAP analysis showing
SB instability and limited CIN. Current precip trends just to the
south could easily affect the southern CWA, and have kept slight
chance pops for this afternoon. Not overly confident with how
intense any storms could get, but can`t rule out an isolated
stronger storm. Second, additional storm development over east and
southeast IA is slowly diminishing while moving east southeast.
However, it will be reaching this more unstable area here in the
near term, and it`s quite possible for it to continue following
the instability southeast. If this were to occur, once again,
locations south of the Kankakee river valley would have the
highest chances. The threat for an isolated stronger storm would
also be possible with this area of precip. Precip chances are then
expected to lower by evening, with dry conditions generally
expected this evening before chances increase once again late
tonight.
Rodriguez
&&
.LONG TERM...
344 PM CDT
Late tonight through Wednesday...
Most guidance in general agreement with returning precip chances
across the region late tonight into Thursday morning, though there
still is some lower confidence with exact placement of this
development. Have maintained similar trends/thoughts in the
forecast for this period, with scattered thunderstorm development
expected mainly along and north of I-88, with the highest chances
still remaining just to the north. This will be in response to the
now lifting boundary, while the LLJ increases across the region.
As this occurs late tonight, should see initial isolated
development become more scattered into early Thursday morning.
With increasing instability, a strong to severe threat will be in
place. Instability will likely be elevated during this time, with
mainly a hail threat expected. Any development should lift further
north with time during late morning and midday, but will continue
to monitor additional isolated development area wide during this
time. With the expected trend north with this development, have
left high temps alone for tomorrow with low 90s expected. If
additional development occurs through midday, then temps could be
lower than forecast. On the opposite side, if precip does not
develop late tonight into Thursday, then will monitor for highs
more in the mid 90s.
Although isolated storms are possible Thursday afternoon, expect
mainly dry conditions into Thursday evening. Surface low expected
to lift northeast through the Great Lakes region, with associated
boundary pushing east through the CWA Thursday night into Friday
morning. Guidance varying to the extent of any precip along this
front as it moves through the area. Do think scattered development
will be in place along this front, but intensity should be
limited as the stronger large scale ascent will be to the north.
As front pushes east on Friday, precip chances quickly lower.
Cooler and dry conditions then expected this weekend into early
next week.
Rodriguez
&&
.CLIMATE...
Record high temps could be jeopardy Thursday. Here are the
current records:
Chicago 92 (2017)
Rockford 92 (1920)
&&
.AVIATION...
For the 00Z TAFs...
Main concern is for potential TS late tonight into Thursday morning.
A stalled front across northern Illinois will begin to shift
northward as a warm front tonight. Numerous TS are expected to
develop over northern IA this evening and spread eastward through
the night. While most of this activity should remain north of the
IL/WI state line, a cluster or two of isolated to scattered TS could
develop across northern IL late tonight. Confidence remains low on
this occurring.
After any potential TS Thursday morning, gusty SSW winds are
expected to develop ahead of an approaching cold front. Frequent
gusts to 25 knots through the afternoon and a few gusts to 30 knots
late in the afternoon are expected. Once the low-levels decouple in
the evening, LLWS will occur as a low-level jet develops.
Kluber
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1105 PM CDT Wed Sep 19 2018
.UPDATE...
Issued at 1045 PM CDT Wed Sep 19 2018
Updated to include 06z aviation discussion below.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 339 PM CDT Wed Sep 19 2018
Two significant weather events could be unfolding over the next
24 to 36 hours. The first is related to very heavy rainfall and
the likelihood of flooding overnight across far southern
Minnesota. The second is related to an enhanced area of severe
weather across south central/southeast Minnesota, and west central
Wisconsin Thursday afternoon.
Thunderstorms are developing this afternoon along an elevated
frontal boundary in southeast South Dakota. Elevated instability
in this area is forecast to move across southern Minnesota
during the evening, and overnight hours. The low level jet will be
enhanced across Iowa tonight, which will lead to strong
convergence along this elevated frontal boundary in far southern
Minnesota. Thus, several rounds of very heavy rainfall are likely
where a flash flood watch has been issued earlier today.
Precipitable water values remain extremely high for this time of
year and with a boundary to enhance the focus of convection,
excessive rainfall amounts are likely. I wouldn`t be surprised to
see a wide area of 2-4 inches, with locally 4-8 inches in far
southern Minnesota by Thursday morning. WPC has already
highlighted far southern Minnesota with a moderate risk of
flooding overnight. People need to exercise the need to stay
abreast of this developing situation and be aware of possible
warnings.
The second event will be determined by where the surface low
tracks Thursday and the amount of instability if more sunshine
develops. First, the latest RAP continues to indicate that the
surface low will track from southwest Minnesota, northeast into
northwest Wisconsin by Thursday evening. This will put south
central and southeast Minnesota, as well as portions of east
central Minnesota in the warm sector Thursday afternoon. This also
includes west central Wisconsin. SPC has already highlighted day
two with an enhanced risk of severe weather in portions of the
southern Minnesota and west central Wisconsin. Please see the
latest SPC Day two outlook for more information. Any deviation to
the surface low track or more/less sunshine expected, will reflect
the amount of instability and severe potential. I wouldn`t be
surprised to see mid to upper 80s in south central Minnesota if
more sunshine develops than forecast. On the cool side of the
frontal boundary, and surface low track, highs on Thursday will be
in the 50s/60s with a cool northeasterly wind.
.LONG TERM...(Thursday night through Wednesday)
Issued at 339 PM CDT Wed Sep 19 2018
The surface low is expected to deepen as it progresses
northeastward Thursday evening. As mentioned in the short term
discussion, any discrepancies in the track will affect the
forecast. There are differences between the 19.12 GFS, 19.12
ECMWF, and 19.12 NAM in the placement of this system. The NAM has
the surface low located along the WI/MN border just east of the
Twin Cities at 00Z. The ECMWF lifts the low to West Central WI by
00Z, and the GFS lifts it to northwestern WI by 00Z. There are
also discrepancies amongst the hi-res models. The HRRR and HREF
Mean both have the main area of convection at the triple point and
along the cold front developing along the MN/WI border just east
of the Twin Cities through South Central WI.
At this time, the areas at highest risk for severe weather
Thursday evening will be Southeastern MN and West Central WI, but
there is still the potential for severe weather across South
Central MN and Central MN, including the Twin Cities. Winds aloft
will be conducive to severe weather with 50-60 kts southwesterly
winds at 850 mb expected over Southeastern MN and West Central WI.
Convection is expected to be of linear mode by 00Z. Given the low
LCL values near 500 m, effective bulk wind difference of near 50
kts, and near 30 kts of 0-1 km shear, the risk for embedded
supercells and tornadoes will likely continue through the early
evening hours. The 19.12 HRRRE 4 hour neighborhood probability of
a tornado shows 15-21% probability East and South of the Twin
Cities at 00Z Friday. Otherwise, the greatest risk will be wind,
and hail cannot be ruled out. Convection is expected to exit to
the east of the forecast area by 06Z Friday.
Cooler and drier air will usher in over the Northern Great Plains
behind the front Friday morning with high pressure and troughing
aloft. High temperatures on Friday look to only reach the mid to
upper 50s and lows on Saturday will range from mid 30s in Western
WI to low 40s in Western MN. With mostly clear skies, there is
potential for patchy frost in Western WI. Southerly low-level flow
looks to begin by late morning on Saturday with weak ridging
aloft, so that will allow for the warmer temperatures in the
western forecast area. A warm front will lift through Northern MN
on Sunday, and the precipitation associated with it is expected to
remain over Northern MN. Precipitation chances return by early
Monday ahead of the next cold front and upper level trough. The
weather pattern remains progressive with a deep upper-level trough
developing over the Great Plains on Thursday with unseasonably
cool temperatures for the end of September.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1045 PM CDT Wed Sep 19 2018
Difficult forecast over the next 18-24 hours across the area. Low
stratus, likely no higher than IFR and potentially as low as
VLIFR, to persist overnight through daybreak tomorrow morning.
There may be some rise into lower-range MVFR tomorrow morning
followed by higher-range MVFR tomorrow afternoon-evening. As for
SHRA/TSRA, there looks to be two main periods of precipitation.
One will come late this evening through the early morning hours
then a secondary surge tomorrow afternoon and evening. Each looks
to contain scattered to numerous thunderstorms, with the second
surge potentially developing as a strong-severe organized line of
storms over south-central MN pushing through west-central WI. The
timing and placement of storms will be tricky to pin down, and in
turn so will visibilities, so frequent amendments may be
necessary. Winds will generally remain out of the northeast
tonight through the first half of Thursday then steadily kick
around to the SE and SW late tomorrow afternoon and evening.
KMSP...Best chances for thunderstorms look to come late tonight
through the pre-dawn hours and again late tomorrow afternoon near
the evening push time. Ceilings look to remain below 1700ft
through at least midday tomorrow and potentially throughout the
entire duration of this TAF set, including near minimums overnight
tonight.
/OUTLOOK FOR KMSP/
Fri...MVFR ceilings early, clearing late to VFR. Wind NW 15G25 kts.
Sat...VFR. Wind SW 5-10 kts.
Sun...VFR. Wind SE 5-10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Flash Flood Watch through Thursday afternoon for MNZ073>078-
082>085-091>093.
&&
$$
UPDATE...JPC
SHORT TERM...JLT
LONG TERM...AMK
AVIATION...JPC
Area Forecast Discussion
National Weather Service Omaha/Valley NE
541 PM CDT Wed Sep 19 2018
.SHORT TERM...(Tonight through Saturday)
Issued at 318 PM CDT Wed Sep 19 2018
Mid-afternoon observational data clearly define the synoptic
front which is quasi-stationary from far southwest IA to between
Omaha and Lincoln into central NE near or north of Broken Bow. To
the south of the boundary, the air mass is hot and moist with
estimated MLCAPE values of 2000-2500 J/kg per latest SPC
mesoanalysis. The primary concern late this afternoon into this
evening is whether convergence along the boundary will be
sufficient to initiate and sustain thunderstorms. Several runs of
the HRRR have indicated isolated storm development between 6 and 7
PM immediately north of the front between O`Neill and Norfolk.
Should that scenario unfold, forecast soundings indicate an
environment supportive of supercell storm modes with a risk for
large hail, damaging winds, and perhaps a brief tornado.
Thunderstorm chances will continue overnight across northeast NE
within a strengthening low-level warm-advection pattern occurring
ahead of a vigorous mid-level trough moving into the northern High
Plains.
Tomorrow into tomorrow night (Thu/Thu night), the short-wave
trough will translate through the northern Plains into upper MS
Valley in tandem with a 60-70 kt mid-level jet streak. An
associated surface low initially over central NE tomorrow morning
will deepen while developing into east-central MN by tomorrow
evening. Meanwhile, a trailing cold front will advance southeast
through our area during the afternoon and evening hours. Low-level
uplift along the front coupled with the influence of height falls
attendant to the mid-level trough will foster a broken band of
thunderstorms by afternoon along the front. Given a modestly
sheared and unstable environment, the setup will favor a few
strong to severe storms capable of damaging winds and hail. Some
heavy rainfall potential exists, but the progressive nature of the
front should preclude a more substantial flash flood threat.
On Friday, a cooler, continental air mass will overspread the
region with gusty northwest winds persisting into the afternoon.
Highs will be in the 60s. By Saturday, a lee cyclone will deepen
over the northern High Plains which in turn will draw a warmer air
mass into the mid MO Valley with highs around 70 or the lower
70s.
.LONG TERM...(Saturday night through Wednesday)
Issued at 318 PM CDT Wed Sep 19 2018
An initially zonal, mid-level flow regime across the north-central
U.S. this weekend will amplify early next week as a short-wave
trough tracks from the Pacific Northwest into the northern Plains.
That upper-air system will be attended by a cold front which is
expected to advance through the mid MO Valley on Monday. High
temperatures ahead of the front on Sunday and Monday are expected
to be in the 70s with an increasing chance of showers and
thunderstorms by Monday afternoon into Monday night with the
passage of the front.
Another vorticity lobe is forecast to move through the central
Plains on Tuesday within the base of an intensifying longer-
wavelength trough over the central CONUS. That feature will yield
continued rain chances into Tuesday. Otherwise, it appears that
the large-scale pattern will favor cooler temperatures during the
middle to latter part of the upcoming week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 540 PM CDT Wed Sep 19 2018
Frontal boundary continues to lift northward across eastern NE and
southwest Iowa late this afternoon. Best chance of TSRA will be
across northeast NE tonight and those could affect KOFK. Could see
some fog at KOFK as well. Chances for TSRA are quite a bit lower
for KOMA and KLNK but think there could be some clouds producing
ceilings from 6000 to 9000 feet overnight. TSRA chances will
increase Thursday afternoon at all 3 sites.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
SHORT TERM...Mead
LONG TERM...Mead
AVIATION...Miller
Area Forecast Discussion
National Weather Service Pocatello ID
228 PM MDT Wed Sep 19 2018
.SHORT TERM...Tonight through Friday night
A cold front tonight will bring scattered showers to central Idaho
with only isolated activity elsewhere. The driving shortwave
trough axis approaching western Idaho will push through the region
tonight dragging a relatively dry cold front with it. The dry air
is evident on the multi-layered water vapor imagery this
afternoon, pushing through central NV into southeast ID. Winds
will pick up in the cold advection behind the front tonight, but
model trends have favored a weaker trough, and thus weaker mixing
of surface winds.
A return to dry conditions is expected for Thursday, save for our
extreme northeastern zone near Island Park. A few lingering
showers and clouds are possible here through about midday. Dry
zonal flow will clear skies across the region, and moderate
temperatures heading into the early weekend.
TAX
.LONG TERM...Saturday through Wednesday
Dry weather is expected through much of the weekend, although the
next cold front is poised to move into our northwest by Sunday
afternoon. The upper-level flow amplifies Saturday allowing
heights to build through the region. For this reason, the forecast
has been trended towards the bullishly warm MEX guidance,
especially in the favored downslope areas of the Snake Plain.
Sunday temperatures and resulting RH values will be tricky,
depending ultimately on the timing of the front.
Confidence in the overall pattern next week is waning. Guidance
remains fairly consistent on digging a deep trough into the
western US after Sunday`s cold front. The problem has been the
placement of the trough and resultant weather it sets up for us.
There will be a cool down for Monday and perhaps Tuesday, but the
big pattern shift that was discussed 24-48 hrs ago appears fairly
transient with cool and dry weather giving way to another warmup
towards the middle of next week. How strong of a warmup remains to
be seen.
TAX
&&
.AVIATION...A Cold Front is forecast to cross SE Idaho this evening,
reaching a BYI-SUN line around 00Z, PIH to IDA between 00-01Z and
DIJ by 03Z. This will cause a wind shift to the SW at KSUN and DIJ,
and simply an increase in winds at BYI, IDA, PIH and DIJ, with gusts
in the 20-30KT range possible along and behind the front, before
winds begin to subside towards 06Z. Am carrying VCSH at all TAF
sites, but this should be mainly Virga or sprinkles accompanied by a
VFR mid deck. HRRR paints the potential for MVFR Stratus from 12-15Z
Thu at IDA but have disregarded this potential ATTM due to the
forecast dry nature of the boundary layer. Gusty Afternoon SW winds
in the 10-20 kt with occasional higher gusts expected at BYI, PIH,
IDA and DIJ between mainly 19-00Z tomorrow afternoon. AD/TAX
&&
.FIRE WEATHER...Combination of wind gusts and low humidity will be
near critical levels for the remainder of the afternoon and early
evening hours. A relatively dry surface cold front will push in from
the west, bringing some stronger wind gusts to Fire Weather Zones
410, 413, and 425 this evening as humidity begins to recover.
Despite the absence of fire weather headlines today, there is
potential for rapid fire spread given the near record low ERC
values. Isolated dry thunderstorms will also be a threat this
afternoon and evening, mainly along the Utah border and across the
Salmon-Challis, however the threat is low. Any activity should taper
off late tonight. Fire Weather Headlines were also considered for
Thursday Afternoon for zones 425 and 410 due to the expected
combination of critical RH and Wind Gusts in the Craters of the Moon
vicinity. Due to the combination of only a small portion of both
zones predicted to exceed critical thresholds and after coordination
with local fire dispatch centers, we opted against a fire weather
headline. The next period of impactful fire weather is expected
Saturday as another mainly dry cold front is forecast to swing
through the region. The combination of gusty winds and low relative
humidity will again combine to elevate fire weather concerns.
Otherwise, seasonable Temperatures and continued dry weather is
currently anticipated to continue into at least early next week.
AD/TAX
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Blacksburg VA
710 PM EDT Wed Sep 19 2018
.SYNOPSIS...
A weak upper-level disturbance will help spark isolated showers
across the southern Shenandoah Valley into central VA but most areas
will be dry tonight. High pressure continues to be in control with
very limited chances for rain through the rest of the workweek. A
better chance for rain is with a cold front which approaches the
area this weekend. Temperatures will trend above normal through the
rest of the workweek.
&&
.NEAR TERM /THROUGH THURSDAY/...
Update as of 710 PM EDT Wednesday...
A bit more showers popped up than expected, therefore adjusted
pops slightly to account for this. Also, brought the overnight
lows down slightly for most areas but most notably, adjusted
temps down significantly at Burkes Garden. Otherwise, no other
notable adjustments appear necessary.
As of 205 PM EDT Wednesday...
High pressure still is in control of our weather, with a surface
cool front over northern WV into western PA more or less having
washed out with little change in airmass. Feels more like late
August than late September across much of the region with temps in
the 80s and dewpoints in the mid-upper 60s. Aloft, a weak shortwave
trough located southeast of Pittsburgh embedded in broader cyclonic
flow aloft is helping to encourage deeper cumulus development in the
Shenandoah Valley with isolated showers and a few rumbles of thunder
per composite radar mosaic. Short-term guidance including the HRRR
and the 12z NAM-3km continue to bring some of this activity
southeastward into our northeastern counties through the daylight
hours. Despite the higher surface dewpoints the air mass is not
substantially unstable with surface-based CAPEs around 1000 J/kg,
and convective depth is being hindered by dry air aloft. Isolated
showers and possibly a rogue thunderstorm or two are possible from
Rockbridge County east-southeast into northern Charlotte County but
many areas otherwise are dry. Weak pressure gradient expected
tonight will again help slacken winds, a little quicker than last
night. As the ground still is damp from Florence`s rainfall and
dewpoints being a little greater than yesterday, expect fog to be
rather prevalent, even in areas outside the typical western river
valleys. Though dense fog is possible in these areas, confidence of
dense fog elsewhere is too low for the need for any headlines at
this point. Lows tonight in the 60s, tending lower 60s west of the
Blue Ridge and mid-upper 60s in the Piedmont.
Areas of fog should burn off early to mid morning Thursday - around
10/11AM in the western valleys and sooner in the Piedmont. High
pressure begins to shift eastward and allows for southeast surface
winds to return against the southern Blue Ridge. A weakly unstable
air mass should help spark isolated showers or thunderstorms along
the southern Blue Ridge where terrain convergence will boost
mesoscale lift. Otherwise, area is largely dry with continued quite
mild and humid conditions. Expect mostly clear to partly cloudy
skies with highs in the 80s and dewpoints well in the 60s.
Overall forecast confidence is moderate to high.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 200 PM EDT Wednesday...
Surface high pressure extending into the area from well offshore New
England will continue to shift east and weaken through the end of the
week ahead of a weak cold front dropping in from the northwest. However
with residual upper ridging in place through Friday night, only
expecting perhaps isolated pop up mountain showers Friday as heating
combines with increasing moisture and return southwest flow to enhance
lift. Appears the upper ridge will flatten enough to allow the cold
front to fold south into northern sections Saturday before stalling
heading south across the region Saturday night. This supports better
chances for showers and storms Saturday afternoon/evening espcly along
and south of the boundary where models show at least decent instability.
Will stay warm and humid until 850 mb cool advection surges in behind
the boundary late Saturday night. Thus highs to remain mostly
in the 80s Friday into Saturday.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 230 PM EDT Wednesday...
Weak surface front to remain stalled out across the area late in the
weekend into early next week as parallel southwest flow aloft keeps the
boundary about stationary near the VA/NC border. Combine this with
strung out vort energy sliding along in conjunction with the front
within a lobe of higher PWATs, expect daily rounds of showers and
storms at least on Sunday and Monday. However exactly where the
boundary ends up will determine the south to north spatial coverage
each day, and better defined as we get closer to the weekend, espcly
given differences in the GFS/ECMWF placement of deeper moisture. This
supports overall chance pops mainly south/west Sunday afternoon and
across the region on Monday for now. Should also be cooler behind the
front starting northern half Sunday as the wedge enhances with highs
70s north to around 80 south Sunday, and 60s and 70s by Monday as
forecast 850 mb values tumble to below +10C in spots to start the week.
Front should start to wash out Tuesday into Wednesday as high pressure
aloft again strengthens across the southeast states ahead of a stronger
upstream 500 mb trough that will sharpen up and approach from the west
by midweek. This will also allow the flow to turn more southwest and in
turn bring warm advection back north ahead of the next stronger front
to the west by Day7. However model timing differences continue in just
how fast showers with the upstream front arrive including residual
focus for convection ahead of this feature given the leftover wedge in
place early on. Given the strength of the southeast ridge, appears
slower solutions best with overall isolated to chance showers Tuesday
into Wednesday. Will turn warm/humid again by midweek with highs
rebounding back up well into the 70s and lower 80s.
&&
.AVIATION /23Z WEDNESDAY THROUGH MONDAY/...
As of 710 PM EDT Wednesday...
VFR conditions to begin the TAF period under high pressure. A
couple lingering isolated showers that popped up in the late
afternoon hours will fizzle out shortly after TAF start time,
and are not expected to affect any TAF sites. Plenty of moisture
still exists in the region from Florence and should create
pretty decent fog coverage tonight. Timing could occur a bit
earlier this evening as the DPs are higher and the winds will be
more calm compared to yesterday. Most sites will go at least
MVFR with valley locations such as BCB and LWB will trend more
toward LIFR. Fog should begin to dissipate shortly after
sunrise, but may still remain for a few hours in the valleys.
High pressure becomes more established by tomorrow and
conditions should will be VFR through the end of the period.
Isolated showers and thunderstorms are expected during the
afternoon hours primarily over the NW mountains of NC and should
not be a problem to the TAF locations. Winds during the period
will be light to mostly calm overnight and become light and
easterly shifting to the south during the day tomorrow.
Confidence in fog occurrence is moderate to high, but low on
the exact timing. High confidence for winds and VFR conditions
outside of fog.
Extended Discussion...
Mainly VFR conditions are expected through Friday with high
pressure over the area. Still anticipate late night fog and
stratus Thursday night, which will favor period of IFR/LIFR
around daybreak. Less confident on fog developing Friday night
given somewhat stronger southwesterly gradient winds. A cold
front will approach the forecast area from the northwest this
weekend, increasing the potential for sub- vfr conditions
associated with scattered shra/tsra.
&&
.HYDROLOGY...
As of 123 PM Wednesday...
River flood warnings continue along the Dan River from Paces to
South Boston.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...AL
NEAR TERM...AL/JR
SHORT TERM...JH
LONG TERM...JH
AVIATION...AL/JR
HYDROLOGY...AL/PM