Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/23/20
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
845 PM EDT Tue Sep 22 2020
.SYNOPSIS...
High pressure remains over the area tonight and Wednesday before
pushing offshore Thursday. Leftover moisture from Beta will
affect the region late in the week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 845 PM EDT Tuesday...
Other than SCT CI arriving from the WSW...another SKC/near calm
and cool night over the local area. Lows 45-50F...except l-50s
at the coast.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY NIGHT/...
As of 330 PM EDT Tuesday...
HRRR smoke fields depicts some smoke arriving in light NW flow
aloft later tonight into Wednesday which could lead to a "hazy"
look and some dimming of the sun at times. Otw, high pressure
dominates with highs 75-80.
Fair Wed eve, then pt cldy after midnite as high/mid lvl moisture
increases from the sw. Lows in the 50s to near 60 se.
Models then diverge Thurs with respect to the leftover moisture from
Beta. NAM faster and most aggressive in bringing shwrs into the fa
Thurs thru Fri while the GFS/SREF/ECMWF hold off until Thurs nite
thru Fri nite as the remnant low washes out across the southern
Applach mts and the leftover moisture becomes entrained along a
coastal/sfc trof.
Given the strength of the offshore high, will lean toward the slower
solution wrt pcpn, but indicated more in the way of cloud coverage
Thurs. Highs Thurs mid-upr 70s. Sct shwrs dvlp across the sw after
midnite Thurs nite. Lows 55-60. Sct shwrs Fri. Highest PoPs 40%-50%
south, with 20%-30% north. Highs in the mid 70s. Shwrs cont Fri nite
(chc PoPs) with lows upr 50s-lwr 60s.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 330 PM EDT Monday...
GFS/Canadian show moisture lingering along a sfc trof thru the
weekend ahead of a series of cold fronts not progged to cross the
region until early next week. Meanwhile, the ECMWF indicates a
mainly dry weekend. Thus, while it will not rain the entire time,
will have to keep at least chc PoPs in the grids thru the period.
Highs generally in the mid-upr 70s each day. Lows mainly in the 60s.
&&
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
As of 705 PM EDT Tuesday...
VFR conditions expected through the 00Z/23 TAF forecast period as
hi pres dominates. WNW winds aob tonight/Wed morning then WSW. Hi
pres moves offshore Thu. SCT SHRAs develop late Thu night
through Sat. Highest PoPs across the S.
&&
.MARINE...
As of 330 PM EDT Tuesday...
Current surface analysis shows a weakening high pressure system
centered to the west of the area, and Hurricane Teddy tracking
towards the Canadian Maritimes. Winds have decreased across the area
and are NW 10-15 kt. Winds are expected to increase and turn west
Tuesday night. Winds will be W 13-18 kt across areas waters. There
may be brief gusts up to 20 kts in the middle bay, but decided to
not issue a SCA due to the short duration and uncertainty that
gusts will reach criteria.
Seas will begin to come down this evening from 10-13 ft to 6-10 ft
by Wednesday morning. Seas will likely remain above SCA level into
Wednesday afternoon off the coast of the VA and MD Eastern Shore,
and by Thursday south of Cape Henry. Therefore, a SCA will remain in
effect for Atlantic coastal waters. SCAs will continue for the
southern Chesapeake Bay zone and mouth of the bay due to the swell
to entering the bay.
Northwest winds 5-10 kt are expected Wednesday into Thursday morning
as high pressure remains to the west of the area and Hurricane Teddy
tracks farther away from the area into the North Atlantic Ocean.
High pressure will then slide off the coast by Thursday and winds
will become southern 5-15 kt into the weekend as the remnants of
Tropical Storm Beta approaches the coast from the west. From Thursday
afternoon to Saturday, seas will be 2-3 ft and waves in the bay will
be around 1 ft.
&&
.HYDROLOGY...
As of 330 PM EDT Tuesday...
Flood Warnings remain in effect for the Nottoway River near
Sebrell and the Blackwater River near Franklin. Flood Warnings
will likely will remain in effect for at least the next day or
two at these sites.
See FLWAKQ/FLSAKQ and weather.gov/AKQ for more site-specific
information.
&&
.TIDES/COASTAL FLOODING...
As of 350 AM EDT Tuesday...
Tidal anomalies are running about 1-2 ft MLLW this morning.
Meanwhile, the last flood/ebb cycle was around 1 kt. The coastal
flood advisory for Currituck/Va Beach/Norfolk/Chesapeake was
cancelled as levels did not reach minor flood stage during this
high tide cycle. This afternoon`s high tide is expected to be a
bit higher which will likely push a portion of this area into
minor flood, so another flood advisory will be hoisted later
this morning. Coastal flood advisory remains in effect for the
northern neck through 8 AM for minor flooding expected at
Lewisetta.
Tidal departures are expected to eventually diminish by
Wednesday as the flow becomes a bit stronger offshore, and swell
from Teddy subsides/moves North of the region.
Swells enhanced by Hurricane Teddy (well offshore), with
periods of ~15 seconds, and very large waves of 10-12 feet+ will
make for very dangerous conditions at the Atlantic Beaches
through Tuesday. In addition, there is dune/beach erosion
potential, especially for more vulnerable locations with the
high tide cycles today before conditions improve beginning on
Wednesday. Beach Hazards Statements/High Rip Current Risk
continue today and is forecast to remain high on Wednesday. A
High Surf Advisory remains in effect for the Atlantic coast as
waves in the surf zone range from 8-10ft North to 10-12ft South.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Coastal Flood Advisory until 11 PM EDT this evening for
MDZ021>023.
NC...High Surf Advisory until 11 PM EDT this evening for NCZ102.
VA...High Surf Advisory until 11 PM EDT this evening for VAZ098.
Coastal Flood Advisory until 10 PM EDT this evening for VAZ075-
077-078-085.
MARINE...Small Craft Advisory until 7 AM EDT Wednesday for ANZ634.
Small Craft Advisory until 11 PM EDT Wednesday for ANZ650-652-
654-656-658.
&&
$$
SYNOPSIS...MPR
NEAR TERM...ALB
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...ALB/MPR
MARINE...CP
HYDROLOGY...
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Boise ID
823 PM MDT Tue Sep 22 2020
.DISCUSSION...Smoke from California wildfires increased in our
CWA today but latest HRRR model suggests it will thin overnight
as westerly flow aloft directs it across northern Nevada. Flow
will become southwesterly again Wednesday and more smoke will
come in. Surface cold front Thursday will turn low-level winds
to the northwest and should push low-level smoke back south
again. Warmer Wednesday ahead of the approaching front, then
cooler and breezy Thursday with a chance of showers in northern
areas. Current forecast looks good on that. No updates for now.
&&
.AVIATION...Mainly VFR with local MVFR in areas of smoke.
Surface winds, southwest 5 to 10kt. Winds aloft to 10k feet MSL,
southwest 25 to 30kt.
&&
.PREV DISCUSSION...
SHORT TERM...Tonight through Thursday night...Westerly flow
behind an exiting shortwave trough today will shift to the
southwest on Wednesday. Windy conditions will develop across
southeast Oregon and higher terrain of southwest Idaho as the flow
aloft strengthens. Temperatures will warm tomorrow reaching about
10 degrees above normal with the southwest flow funneling smoke
up from CA. A trough will push into the interior NW Thursday
lowering temperatures, increasing clouds, and bringing a chance
of showers to east-central Oregon and west-central Idaho. The
increased westerly flow will also blow smoke out of the area.
Temperatures on Thursday will be near normal.
LONG TERM...Friday through Tuesday...An upper trough will move
through the northern Rockies on Friday, bringing a chance of
showers to the northern half of the CWA and temperatures 5-10
degrees below normal. Temperatures will be cold enough for snow
or a rain/snow on the highest peaks, generally above 8000-9000 ft
MSL. Breezy west to northwest surface winds will occur as the
trough passes overhead. Most of the moisture will shift north on
Saturday as northwest flow aloft develops, but a slight chance of
showers will remain across the far northern mountains.
Temperatures will warm to closer to normal. Dry conditions will
develop for the remainder of the forecast period as an upper
ridge builds near California on Sunday and amplifies over the
Pacific Northwest early next week. Temperatures will warm to
well-above normal with breezy winds each afternoon.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.
&&
$$
www.weather.gov/Boise
www.facebook.com/NWSBoise
www.twitter.com/NWSBoise
DISCUSSION...LC
AVIATION.....JC
PREV SHORT TERM...DG
PREV LONG TERM....ST
Area Forecast Discussion
National Weather Service Wichita KS
633 PM CDT Tue Sep 22 2020
.SHORT TERM...(This evening through Friday night)
Issued at 252 PM CDT Tue Sep 22 2020
Tropical moisture associated with the remnants of TD Beta (currently
located along the TX coast), continue to feed north-northwest into
portions of ern OK and SE KS at this time, with widespread rain
across most of ern OK and scattered rain over SE KS. Tropical
connection and high precipitable water (PW) values of 150-160
percent of normal, has led to the rain showers over performing, with
some areas along the KS/OK border picking 0.50 to a little over an
inch of rainfall, from slow moving rain showers. This high
PW/tropical connection has led to widespread stratus and even some
patchy drizzle over most areas east of the Kansas Turnpike, with the
northwestern edge of this stratus flirting with a Kingman to Newton
to Hillsboro line.
For the late afternoon hours into this evening, latest RAP and other
hi-rez models suggest that a combo of rain showers and drizzle will
continue for areas east of the Turnpike into the evening and most of
the overnight hours. Latest RAP shows weak moisture transport, will
continue tonight into SE KS, which seems to support a continued
light shower/drizzle chance. Expect some pockets of heavier rainfall
amounts closer to the KS/OK border, where the more steady rain
showers will persist the longest. Most locations will see rainfall
amounts under a tenth of an inch, but some areas along the border
could see pockets of 1 to 2 inches. Given the dry conditions over SE
KS, and high flash flood guidance values, not expecting any flooding
concerns, given the slow rainfall rates.
The weak moisture transport will also lead to the stratus deck over
southern KS, pushing further north-northwest into most of central KS
late this evening and tonight. Latest model guidance seems to so
support this. So expect the cloudy skies to increase in most
locations overnight. Could even some patchy drizzle as the low
layers remain fairly saturated from the tropical type airmass, so
may push the drizzle mention further to the NW as well.
Remnants of TD Beta will continue to linger along the TX Gulf coast
for early Wed through Wed afternoon, but low level moisture will
continue to wrap to the north of Beta, into OK, SE KS and SW MO, as
some sort of meso induced vort center (MCV) develops from this
afternoons showers across OK, and drifts into SW MO. This MCV and
the higher PW axis lingering over SE KS, will probably lead to the
chance of showers lingering over SE KS for early Wed and possibly
into Wed afternoon as well.
Expect dry conditions for the rest of the forecast area for Wed, but
expect temperatures to be a little cooler, as lingering mid-high
level smoke and increasing cloud cover over SE KS will keep max
temps below seasonal averages in the middle 70s.
Weak ridging will continue for the end of the week as well, as the
MCV noted above, shifts east of the area for Wed night into Thu.
This will allow for max temps to slowly rise above normal for Thu
and Fri with SW-S breezes over the area.
Ketcham
.LONG TERM...(Saturday through Tuesday)
Issued at 252 PM CDT Tue Sep 22 2020
Medium range models suggest that the next frontal boundary will move
rapidly south across KS for Sat afternoon through Sat night, before
washing out over OK. Moisture again appears to be limited as this
front moves south, so will keep just some slight chance pops going
for areas east of the Turnpike, as both the ECMWF and GFS show an
almost dry frontal passage. So NBM pops may need to be
removed with later runs if this trend continues.
Ketcham
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 627 PM CDT Tue Sep 22 2020
Low level moisture continues to lift northward across the area
with widespread stratus across much of south central and southeast
KS. This is expected to continue spreading slowly northward into
central KS tonight. Stratus build-down is expected across much of
southern KS gradually leading to reduced visibilities while a
combination of radiational cooling and some low level moisture
advection later tonight may help drive visibilities down across
portions of central KS. This is expected to result in widespread
IFR with some LIFR also possible. VFR is expected to return to
central KS during the morning hours on Wed but may be slow to
return to far southeast KS.
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 63 76 56 83 / 10 0 0 0
Hutchinson 62 78 56 85 / 0 0 0 0
Newton 62 76 55 84 / 10 10 0 0
ElDorado 62 75 55 82 / 10 10 0 0
Winfield-KWLD 62 75 55 82 / 10 10 0 0
Russell 59 82 57 87 / 0 0 0 0
Great Bend 60 80 56 87 / 0 0 0 0
Salina 62 80 57 88 / 0 0 0 0
McPherson 62 78 55 86 / 0 0 0 0
Coffeyville 61 74 54 79 / 20 20 0 0
Chanute 61 75 54 79 / 20 20 0 0
Iola 61 75 54 81 / 20 20 0 0
Parsons-KPPF 61 74 54 79 / 20 20 0 0
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Ketcham
LONG TERM...Ketcham
AVIATION...MWM
Area Forecast Discussion
National Weather Service Indianapolis IN
1148 PM EDT Tue Sep 22 2020
.UPDATE...
The AVIATION Section has been updated below.
&&
.SYNOPSIS...
Issued at 340 PM EDT Tue Sep 22 2020
Dry conditions continue through the week due to strong surface
ridging. Rain chances and temperatures turning cooler are in store
for the long term as an upper trough moves into the area.
&&
.NEAR TERM /Tonight/...
Issued at 340 PM EDT Tue Sep 22 2020
Strong surface ridging will continue tonight, keeping conditions
dry. High clouds will persist through the night as the low
associated with tropical storm Beta. HRRR also shows that the
smoke layer will overspread across the area tonight. Temperature
wise, expecting lows in the mid to low 50s.
&&
.SHORT TERM /Tomorrow through Friday/...
Issued at 340 PM EDT Tue Sep 22 2020
Mid to high cloud coverage will be increasing from the start of
the short term period, as the low associated with tropical storm
Beta makes its way towards the region. Strong ridging at the
surface will limit Beta`s impacts to cloud coverage... keeping
things dry at the surface. The surface high will push out into the
Atlantic as the week goes on, meanwhile the remnants of Beta will
pass over the Ohio Valley Thursday and continue NE. After the low
moves east of the area, expect mostly sunny skies again and
continued dry conditions. Temperatures will be seasonable with
highs near 80 and lows in the 50s.
With the continuation of dry weather, take precautions when
dealing with any fires, including grilling. Keep a water hose or
fire extinguisher nearby.
&&
.LONG TERM (Friday Night Through Tuesday)...
Issued at 240 PM EDT Tue Sep 22 2020
The National Blend of Models initialization was accepted for most
items.
As upper ridging develops across the western USA, an upper level
trough will move in and deepen across the area throughout the long
term.
At the surface, a cold front will move through Saturday night
into Sunday. With this timing, feel that odds of rain during the
day Saturday are low. Thus removed most of the slight chance PoPs
then.
Moisture doesn`t look impressive with the front, and model QPF is
generally light. Will continue chance PoPs through Sunday with the
front.
As the upper trough deepens over the area, upper impulses will
move through the flow, and reinforcing shots of cooler air will
move through at the surface as well. These could trigger a few
showers at times. However timing is quite uncertain this far out.
Will keep the initialization`s low PoPs through the remainder of
the long term.
Rainfall amounts with these features look low. Total model QPF
from the GFS/ECMWF through next Tuesday is generally a tenth to a
third of an inch.
&&
.AVIATION /Discussion for the 23/06Z TAF Issuance/...
Issued at 1145 PM EDT Tue Sep 22 2020
Continued MVFR fog mention at outlying sites early Wednesday
morning where dew point depressions are lower. Otherwise,
conditions will mainly be at VFR levels with strong subsidence.
Meanwhile, winds will generally be south/southwesterly at 4 to 8
kts.
&&
.IND WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SYNOPSIS...KH
NEAR TERM...KH
SHORT TERM...KH
LONG TERM....50
AVIATION...TDUD
Area Forecast Discussion
National Weather Service North Platte NE
626 PM CDT Tue Sep 22 2020
.SHORT TERM...(This evening through Wednesday night)
Issued at 351 PM CDT Tue Sep 22 2020
The main forecast challenge this week continues to revolve around
the warm and dry weather leading to fire weather conditions. Smoke
from Rocky Mtn wildfires has also been spreading haze into the
forecast area, resulting in sporadic visibility reductions.
This evening and tonight... A surface low slowly treks across SoDak
overnight, which drags a weak front or trough through the Sandhills.
A couple near-term solutions hint at isolated showers in the west
tonight, but did not include a mention of precip in the forecast.
Current dew point depressions (given it is peak heating) range from
55F in the panhandle to 40F north central, let alone the sky is
cloud-free. Forecast soundings suggest increased low level lift with
the boundary, but the majority of the moisture lies above H5. Any
isentropic upglide also remains elevated. Cloud cover should
increase with a slight moisture plume off the mountains, but do not
expect any precip with this profile. Used a general model blend for
min temps in the 50s.
Wednesday... Upper level flow stays rather flat over the central
Plains and a ridge trying to build over the Four Corners.
Regardless, southwest flow at H85 advects warmer air into the region
with temps rising a broad 2-3C across Nebraska. RAP smoke plume
guidance suggests less near-sfc smoke over the area, and upper level
steering currents also take a more southeasterly direction. With
less filtering of sunshine expected tomorrow, trended toward warmer
end of guidance for max temps. Highs range from mid 80s near the
Pine Ridge to lower 90s central and southwest. Will need to monitor
fire weather conditions in the far west as RH should drop to below
20% while west/northwest winds may gust to 20mph or higher at times.
Brief downslope flow at H85 late morning and early afternoon would
support locally warmer, drier, windier conditions, especially in the
panhandle.
.LONG TERM...(Thursday through Tuesday)
Issued at 351 PM CDT Tue Sep 22 2020
Thursday through the weekend... The upper ridge progresses east with
the axis bisecting the forecast area late Thursday/early Friday, and
then is quickly shoved southeast by a digging Upper Midwest trough.
This pattern shift places Nebraska primarily in northwest flow over
the weekend, while a strong cold front moves through at the surface.
Thursday also presents a near critical fire weather day in the
panhandle as RH takes a further dip. Concerns assuage somewhat this
weekend as RH recovers behind the front, but then gusty winds become
an issue. Some guidance also suggests light precip potential with
the fropa Friday night. However, no real moisture flux occurs ahead
of the front despite the strong fgen and convergence. Capped PoP to
schc or low end chc across the north and no PoP to the south.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 615 PM CDT Tue Sep 22 2020
VFR conditions expected to prevail for the next 24 hours. Main
concern will be the passage of a cool front Wednesday afternoon.
This front should clear much of the Sandhills, including VTN by
23/21Z and will lead to a wind shift to the northwest. Southwest
Nebraska, including LBF, will likely not see frontal passage
before the end of the TAF period, or 24/0Z, and will only see a
wind shift from southwest to west Wednesday afternoon.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Snively
LONG TERM...Snively
AVIATION...Brown
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
619 PM CDT Tue Sep 22 2020
.SHORT TERM...
133 PM CDT
Through Wednesday night...
A quiet weather pattern continues as upper-level ridging remains
established across much of the United States and an expansive
surface high pressure system stays parked over the southeast. A low-
amplitude upper-level short-wavelength trough (e.g. a ripple) in the
upper-level flow will continue to propagate southeastward over the
Great Lakes with no consequence outside a few mid-level clouds along
the IL/WI state line this evening. Lows will drop into the low to
mid 50s overnight. Tomorrow, upper-level outflow cirrus from the
remnants of Tropical Storm Beta will creep northward into central
Illinois, otherwise affording another pleasant Fall day. Highs
tomorrow will top off in the upper 70s to around 80. Sunshine
will continue to be masked somewhat by mid-level smoke (centered
at around 10,000 ft). Light southwest winds will prevail.
Borchardt
&&
.LONG TERM...
259 PM CDT
Thursday through Tuesday...
The generally quiet and mild pattern with highs around 80F will
continue through Friday night. HRRR experimental smoke forecasts
suggest that the smoke/haze aloft may stick around into Thursday.
A weakening short-wave topping the western and central CONUS
ridging Thursday afternoon may bring a few isolated showers to
northwest IL, with otherwise dry conditions elsewhere. Guidance
continues to indicate that the remnants of Beta and its moisture
will get shunted off to the southeast later Thursday into Friday.
Friday will be a pleasant day, which will be followed by an
initial cold front passage on Saturday/Saturday night. Deep layer
moisture trajectories will be cut off ahead of the front and we
may top out at low 60s F dew points in surface southwesterly flow.
Uncertainty in timing of the front and associated showers on
Saturday has increased today, with the latest ECMWF speeding up,
so didn`t make big changes to NBM PoPs, which peak during Saturday
evening but will undoubtedly need refining. With meager instability
at best due to limited moisture return and weak lapse rates, kept
thunderstorm mention in the slight chance/isolated range. Exact
frontal timing will determine high temperature distribution
(earlier would keep temps cooler north), though thermally supports
low to even mid 80s.
Behind the front, the daytime hours on Sunday should be primarily
dry and comfortable with highs in the 70s. The pattern change to
cooler and unsettled weather still appears on track as we head
into next work week. A disturbance could bring some isolated
showers Sunday evening and night. Mid and upper level pattern next
week is expected to evolve to a temporary long-wave trough over
the eastern CONUS (including western Great Lakes region). Specific
details are still in flux. Recent runs of the ECMWF and several
members of the ECMWF ensemble suggest a strong and dynamic short-
wave diving southeast could spur deep surface cyclogenesis over
the Great Lakes region. The other guidance is slower and more
muted with this. If a deep surface low does indeed track to our
north, next Monday could be windy and a good deal warmer than
official forecast highs in the upper 60s to lower 70s ahead of the
front that would probably bring shower activity. However we get
there, by Tuesday, much cooler and unsettled/showery weather
should be in store with highs only in the lower to mid 60s if not
cooler in spots.
Castro
&&
.AVIATION...
For the 00Z TAFs...
There are no aviation weather concerns. West-southwesterly winds
will prevail through the period with gradually thickening cirrus
tonight and through Wednesday. Pockets of lingering smoke will
continue, but is forecast to remain most concentrated well aloft,
above FL080 or so, with no surface visibility restrictions
anticipated.
Carlaw
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
Visit us at weather.gov/chicago
Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/NWSChicago
www.twitter.com/NWSChicago
www.youtube.com/NWSChicago
Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
907 PM CDT Tue Sep 22 2020
.NEAR TERM /Now Through Thursday/...A definite moistening and
warming period of change upcoming as Beta`s remnants move towards
the region from the west during the next day or so. Will say up
front the exact path that Beta takes, and not all models are on
board as to just how far south it may track after midday
tomorrow, will largely determine our impacts.
For starters, we are now issuing a Coastal Flood Advisory. Available
extratropical storm surge guidance is showing minor coastal flooding
surrounding the time of high tide late Wednesday night and into Thursday
morning. This is due in part to a very strong pressure gradient force
between, you guessed it, the anomalously strong surface high
pressure system that is still to our northeast and the approaching remnants
of Beta. it should be a one shot deal and for that high tide cycle
only.
Secondly, we`ll have to watch closely for mesoscyclones that
may produce isolated tornadoes. By mid-morning tomorrow, the warm
sector will have surged onto our coastal zones and interior
southeast MS (shown by EC, SREF and latest GFS). By dark,it will
have progressed through the southwest half of our area, and by
sunrise Thursday, all but south central Alabama. The SBCAPE
remains scant (<500 J/kg) for tomorrow and mostly confined to
interior southeast MS and Mobile County, AL, but 0-1km vertical
wind shear vector are strengthening and will eventually phase with
thermodynamic instability. After dark tomorrow evening and
looking into Thursday, the vertical wind shear and instability
phase a little better from west to east as Beta should pass to our
northwest. If the track is further south, the warm sector will
arrive sooner and the surface winds will back more creating more
0-1 km helical area (currently forecast as 150-200 m-2 s-2)
available for updraft rotation. At this point in time, a few
mesocyclones could produce a weak tornado from late tomorrow
evening on. If it ends up being elevated, it will quickly squash
that potential - so, some uncertainty is there during the
overnight hours. Forecast CAPES spike on Thursday, but regional
hodographs become increasingly more straight-line as Beta passes
to our northwest. We have re-introduced thunder after 21Z tomorrow
afternoon over the southwestern zones and have spread it
gradually to the north and east as the surface-based warm sector
surges. By late Thursday, thunder will still be ongoing over the
central and eastern portion of our areas and beginning to diminish
in the west as Beta lifts further north and the overall system
takes a more positive tilt.
As for the heavy rainfall threat - we believe at this time the previous
forecast of 1-2" looks pretty spot on (with a local 2-4"). There is
a deep tropical tap coming into Beta`s evolving warm sector that bisects
the old frontal zone that the previous anticyclone helped to
establish - and this evolves within our area in a southwest to
northeast fashion. We really have to watch this intersection to ensure
localized flash flooding does not become centered over areas hardest
hit by Sally`s rainfall. At this point, we feel the deep layer moisture
band is moving just enough to prevent significant flooding impacts
- but again - it will have to be watched. For now, we leave the
front-facing flood graphic with limited impacts.
Highs tomorrow in the mid and upper 70s, lows tomorrow night in
the mid 60s inland to the upper 70s along the beaches and highs
on Thursday in the upper 70s and lower 80s. Cloudy to mostly cloud
through the entire period with rain chances increasing steadily
through the period. /23 JMM
&&
.PREV DISCUSSION... /issued 623 PM CDT Tue Sep 22 2020/
NEAR TERM UPDATE /Now Through Wednesday night/...A strong
surface ridge of high pressure continues to extend across the
Appalachians, Tennessee Valley, and the adjacent southeastern
U.S./northern Gulf Coast states. A plume of moisture continues to
extend across our forecast area well to the east of Beta,
resulting mainly broken to overcast low to mid level clouds,
though a few places around the CWA have seen some breaks early
this afternoon. Radar has been fairly quiet this afternoon, with
only a few sprinkles or very light rain showers developing across
parts of our area.
Beta should remain a depression and is forecast to gradually lift
northeast across southeast TX tonight through Wednesday. The
surface ridge of high pressure should gradually shift eastward and
extend eastward from the Tennessee Valley to the western Atlantic
by Wednesday afternoon. Surface winds should gradually turn more
southeasterly across our forecast area during the day Wednesday,
with low level warm advection bringing increased surface dewpoints
in the upper 60s to lower 70s across southeast MS into southwest
AL and the western FL panhandle late Wednesday morning into
Wednesday afternoon. In terms of the rainfall forecast, expect a
fairly quiet night tonight with fairly limited coverage of showers
over our region. The latest HRRR and WRF-ARW mainly hint at weak
isentropic ascent near the immediate coast through the overnight
period with mainly dry conditions inland. The deterministic
guidance show a bit more in the way of isentropic ascent inland,
particularly over southeast MS/southwest AL, so will keep a low
(20-30%) chance of light rain showers in the forecast through the
overnight period.
A more pronounced southwesterly flow aloft develops over our
region on Wednesday as the ridge axis shifts east and as an upper
trough over east Texas shunts moisture associated with Beta into
Louisiana and the MS Valley region. Weak shortwave impulses in
the flow aloft and an increase in boundary layer moisture will
support an increase in rain coverage, especially going into
Wednesday afternoon. We have kept the highest POPs (likely)
coverage over our southeast MS and adjacent southwest AL counties
going into Wednesday afternoon. QPF amounts trended slightly lower
through Wednesday afternoon over our western zones (0.25" to
0.50", maybe locally over 1"). Any limited flooding threat will
probably be quite minimal over southeast MS considering the drier
soil conditions and lower QPF, but we will still monitor given
some uncertainty in the deep moisture placement (see below for
additional comments on the flood threat Wednesday night into
Thursday). Instability remains quite weak, but there be just
enough for a slight chance of thunder in the region of highest
moisture over southeast MS and adjacent southwest AL by Wednesday
afternoon. Lows tonight range in the lower to mid 60s inland and
in the upper 60s to around 70 near the immediate coast. Highs on
Wednesday should reach into the mid 70s to around 80 degrees.
A HIGH risk of rip currents continues along area beaches through
the remainder of the week. /21 and /23 JMM
AVIATION...
00Z issuance...Period begins with widespread mid- and high clouds
and a layer of MVFR low clouds (mainly stratus but with some
billowy stratocumulus appearance at times) which is draped mainly
across interior SE MS and mainly Coastal Alabama. This will
continue to be the main impact most of this TAF period, but the
northern extent of this cloud shield will very gradually encroach
to the NE as Beta`s remnant surface low approaches and low level
warm air advection commences. Most areas should remain rain free
(except a few passing sprinkles) until after Noon tomorrow. After
that time, rain coverage will increase and we could then see some
MVFR VSBYs along with the low-end MVFR CIGs. Also isolated thunder
may be introduced after 00 UTC on the 24.00UTC TAF package.
Surface winds remain ESE to SE through the period and increase
once again in speed tomorrow afternoon (gusty along the coast).
/23 JMM
PREV DISCUSSION... /issued 401 PM CDT Tue Sep 22 2020/
NEAR TERM UPDATE /Now Through Wednesday/...Tropical Depression
Beta has moved inland and continues to drift across southeast TX
early this afternoon, while a strong surface ridge of high
pressure continues to extend across the Appalachians, Tennessee
Valley, and the adjacent southeastern U.S./northern Gulf Coast
states. A plume of moisture continues to extend across our
forecast area well to the east of Beta, resulting mainly broken to
overcast low to mid level clouds, though a few places around the
CWA have seen some breaks early this afternoon. Radar has been
fairly quiet this afternoon, with only a few sprinkles or very
light rain showers developing across parts of our area.
Beta should remain a depression and is forecast to gradually lift
northeast across southeast TX tonight through Wednesday. The
surface ridge of high pressure should gradually shift eastward and
extend eastward from the Tennessee Valley to the western Atlantic
by Wednesday afternoon. Surface winds should gradually turn more
southeasterly across our forecast area during the day Wednesday,
with low level warm advection bringing increased surface dewpoints
in the upper 60s to lower 70s across southeast MS into southwest
AL and the western FL panhandle late Wednesday morning into
Wednesday afternoon. In terms of the rainfall forecast, expect a
fairly quiet night tonight with fairly limited coverage of showers
over our region. The latest HRRR and WRF-ARW mainly hint at weak
isentropic ascent near the immediate coast through the overnight
period with mainly dry conditions inland. The deterministic
guidance show a bit more in the way of isentropic ascent inland,
particularly over southeast MS/southwest AL, so will keep a low
(20-30%) chance of light rain showers in the forecast through the
overnight period.
A more pronounced southwesterly flow aloft develops over our
region on Wednesday as the ridge axis shifts east and as an upper
trough over east Texas shunts moisture associated with Beta into
Louisiana and the MS Valley region. Weak shortwave impulses in
the flow aloft and an increase in boundary layer moisture will
support an increase in rain coverage, especially going into
Wednesday afternoon. We have kept the highest POPs (likely)
coverage over our southeast MS and adjacent southwest AL counties
going into Wednesday afternoon. QPF amounts trended slightly lower
through Wednesday afternoon over our western zones (0.25" to
0.50", maybe locally over 1"). Any limited flooding threat will
probably be quite minimal over southeast MS considering the drier
soil conditions and lower QPF, but we will still monitor given
some uncertainty in the deep moisture placement (see below for
additional comments on the flood threat Wednesday night into
Thursday). Instability remains quite weak, but there be just
enough for a slight chance of thunder in the region of highest
moisture over southeast MS and adjacent southwest AL by Wednesday
afternoon. Lows tonight range in the lower to mid 60s inland and
in the upper 60s to around 70 near the immediate coast. Highs on
Wednesday should reach into the mid 70s to around 80 degrees.
A HIGH risk of rip currents continues along area beaches through
the remainder of the week. /21
SHORT TERM /Wednesday night Through Friday night/...A warmer and
more unstable airmass will begin to move into the area Wednesday
into Thursday as what`s left of Beta move northeast into north
Alabama by Thursday afternoon. This will drag a warm front northward
during the morning and north of the area by late morning and early
afternoon. The focus of the heavier rainfall is expected to be along
and north of the warm front from central Mississippi into northern
Alabama. As a result rainfall amounts have been adjusted downward,
however total rainfall amounts of 1 to 2 inches cannot be ruled out
through Thursday night. This could still result in some minor
flooding especially in areas that remain saturated from previous
rains from Sally. Therefore a limited threat of flooding will remain
in place across the area Wednesday night into Thursday. While
instability values will increase especially near the coast on
Thursday, wind fields will be weakening with time and the threat of
any strong storms is expected to remain low.
An upper trough slides east on Friday finally sweeping the remains
of Beta well to the northeast with a lingering trough axis extending
into southern Texas. This will maintain scattered to numerous
showers and thunderstorms during the day on Friday with decreasing
chances in the afternoon as some drier air works in from the
northwest. Highs on Thursday will be in the upper 70s and low 80s
with low to mid 80s expected on Friday.
A high risk of rip currents continues along area beaches through the
period. /13
EXTENDED TERM /Saturday Through Tuesday/...The base of the upper
trough pinches off over Texas on Saturday and drifts southward as
the main part of the trough moves off the east coast. This will push
the deep layer moisture to the east of the area by late in the
weekend. Early next week a much stronger trough is forecast to dig
across the eastern states through midweek. This will send a strong
cold front southward across the area late in the period, potentially
delivering the first true taste of fall weather by the middle of
next week. /13
MARINE...A pressure gradient between a strong surface ridge of high
pressure building from the New England states to the northern Gulf
of Mexico and Tropical Storm Beta approaching the central Texas
coast will continue to result in moderate to strong easterly to
northeasterly winds over the marine area through tonight. Winds turn
more southeasterly to southerly Wednesday and Thursday. Seas remain
elevated 4-6 feet through Thursday.
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...High Rip Current Risk through late Thursday night for ALZ265-266.
Coastal Flood Advisory from 1 PM Wednesday to 10 AM CDT Thursday
for ALZ263>266.
FL...High Rip Current Risk through late Thursday night for FLZ202-204-
206.
Coastal Flood Advisory from 1 PM Wednesday to 10 AM CDT Thursday
for FLZ202-204-206.
MS...None.
GM...Small Craft Advisory until 10 PM CDT Wednesday for GMZ655-675.
Small Craft Advisory until 4 AM CDT Thursday for GMZ650-670.
&&
$$
This product is also available on the web at:
http://weather.gov/mob
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 245 PM CDT Tue Sep 22 2020
The primary forecast concern is the potential for low clouds and
some fog to develop over southeast NE and southwest IA later
tonight. These may last into mid or possibly late Wednesday
morning.
Water vapor satellite loop in combination with recent RUC model
500 mb initializations show a trough from southern British
Columbia down into northwest AZ. Considerable mid and high level
tropical moisture extended from TX northward into MO and eastern
KS. Surface analysis showed high pressure from the western parts
of KY and TN extending back west into MO. Low pressure extended
from central MT down into eastern parts of WY and CO. Temperatures
at 3 pm were mainly in the lower or mid 80s across eastern NE and
southwest IA with dewpoints in the 50s.
Low clouds will expand northward from eastern KS overnight, and
there will also be at least some patchy fog. Winds are probably
too strong for dense fog, but that will have to be monitored. All
model guidance does seem to show enough mixing to scatter out the
clouds before Noon. There could also be some very light drizzle,
but for now did not include that in the text of the forecast. Lows
tonight should be mostly 55 to 60. Highs Wednesday should vary
from the upper 70s to lower 80s most of the area, with mid and
possibly upper 80s in the northwest half of northeast NE.
Friday will probably be the warmest day of the week, with highs
mostly in the upper 80s or lower 90s. Rain chances will be low
until Friday night/Saturday, when a front will push through the
area. We will keep mention of some 20-30 percent chances for
showers and isolated thunderstorms. Any amounts would be pretty
light, probably less than a tenth of an inch. Cooler air will move
in from the northwest Saturday, with another stronger push of
colder air Monday into Tuesday. Highs Tuesday may only be in the
upper 60s/lower 70s. Rain chances Sunday into Tuesday are less
than 20 percent for now.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 615 PM CDT Tue Sep 22 2020
Southerly winds continue through the TAF period, with gusts up to
25 knots after 18Z on Wednesday. Expect VFR conditions to be
common, with some MVFR visibility expected to dip as low as 3
miles at KOMA and KLNK with ceilings as low as 500 feet. Expect
clearing mid to late morning on Wednesday.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...Miller
AVIATION...Nicolaisen
Area Forecast Discussion
National Weather Service Paducah KY
604 PM CDT Tue Sep 22 2020
.UPDATE...
Issued at 603 PM CDT Tue Sep 22 2020
Updated Aviation discussion for the 00 UTC TAF issuance.
&&
.SHORT TERM...(Tonight through Saturday)
Issued at 228 PM CDT Tue Sep 22 2020
The main issue through Thursday is how much rain will make it
this far north. As of 19z, radar indicated rain was already moving
across se Missouri. This is well ahead of any model guidance,
though the latest hrrr finally latched onto it. Granted, most of
this rain is very light. Kpof reported only a trace through 19z.
A 500 mb trough over the Plains will move slowly eastward, passing
across the lower Ohio Valley on Thursday. The models are having a
hard time determining how much moisture from the remnants of
tropical storm Beta will be picked up by this trough. Based on the
latest radar and surface obs, it appears the models may be a
little too slow bringing the moisture north. The 12z consensus
model pops have increased, with some likely pops along the
Tennessee border on Wed night. For this forecast, pops will be
raised and expanded north. Although the changes will be fairly
small, it is probably the start of a trend in the forecast.
Precip amounts will be light in any case. The models indicate
persistent 850 mb ridging over our area through Wednesday, which
should limit qpf to less than a tenth of an inch. Temps will be
confined to a narrower range by the moisture. Highs will be mainly
in the low to mid 70s, with lows in the 50s through Thurs.
After the 500 mb trough passes to our east on Thursday, mainly dry
conditions are expected Friday through Saturday. There could be a
few diurnal showers each day as south winds bring warmer and more
humid air. Dew points will be mostly in the upper 60s by Sat
afternoon. Some thunder cannot be ruled out by late Saturday.
Highs will be around 80 Friday and in the lower 80s on Saturday.
Lows will be in the 60s.
.LONG TERM...(Saturday night through Tuesday)
Issued at 228 PM CDT Tue Sep 22 2020
A rather big change in the upper air pattern will occur early next
week. The ensemble means of the gfs, ecmwf, and Canadian have all
been consistently developing a large and deep 500 mb trough over
the eastern states by Tuesday. The 12z gefs is no exception. A
strong northwest flow will bring the coolest air so far this
season. The 12z gefs brings 850 mb temps down to about 5 degrees
Celsius in the lower Ohio Valley Tuesday, with the coldest air
still to come. The forecast temps will be biased toward
climatology, with highs in the lower 70s Tuesday. Some downward
revisions may be needed.
As far as precip, the models are not in good agreement on the
timing of the cold front passage. For now, the national model
blend (nbm) will be followed. The nbm indicates a primary cold
front passage late Sat night or Sunday morning, accompanied by
some showers and maybe a few thunderstorms. However, the bulk of
the cooler air will await a secondary cold front Monday night or
early Tuesday. This front may be accompanied by a few more
showers.
&&
.AVIATION...
Issued at 603 PM CDT Tue Sep 22 2020
Mid/high level clouds, generally AOA 12kft or higher, continue to
stream north into the region. There has been some widely scattered
light shower activity near KCGI and KPAH. Since this may continue
through the night into much of Wednesday, opted to include a
mention of vicinity showers at both locations through the entire
forecast period.
Will also need to keep an eye out for MVFR (or worse) fog development
overnight into Wednesday morning. Right now, thinking the best
potential for MVFR fog will be at KMVN/KEVV/KOWB, where high
cloud cover is the thinnest, but included it at terminals for now
due to uncertainty.
Winds will be light/variable or calm overnight, then
light/variable after daybreak Wednesday.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
UPDATE...DWS
SHORT TERM...MY
LONG TERM...MY
AVIATION...DWS