Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/28/19
Area Forecast Discussion
National Weather Service Birmingham AL
657 PM CDT Tue Aug 27 2019
.UPDATE...
For 00Z Aviation.
&&
.SHORT TERM...
/Updated at 0349 PM CDT Tue Aug 27 2019/
Thunderstorms have developed across northwest Alabama ahead of an
outflow boundary. The HRRR model has been forecasting this
development since early this morning and has the activity pushing
southeast through the I-20/59 corridor during the late afternoon
and early evening hours. The most unstable air mass was located
across west Alabama where surface dewpoints were in the middle to
upper 70s and surface based CAPE values near 4500 J/kg. The
limiting factor is an axis of minimum DCAPE (<1000) across the
same area. This will hinder downdraft potential, and so far there
have been no reports of significant wind. Since the activity is
more surface based with little upper level support, expect a
significant decrease in areal coverage by 8 pm. Any remaining
activity should be south of I-20 by 9 pm, with only isolated
showers after midnight.
58/rose
.LONG TERM...
/Updated at 0322 AM CDT Tue Aug 27 2019/
Wednesday through Tuesday.
The cold front finally pushes through Central AL on Wednesday. I
think it will be mostly south of our area by the late morning/early
afternoon, but we might see some lingering shower activity
associated with the frontal forcing along the far southern counties
tomorrow afternoon. This should diminish by the evening with drier,
northerly flow pushing in. High pressure builds in Thursday morning,
leading to mostly clear skies. Dewpoints will be in the upper 50s to
low 60s by Thursday morning, which in conjunction with mostly
clear skies, will allow temperatures to drop into the low to mid
60s for much of Central AL both Thursday morning and Friday
morning. Later Friday morning, the center of the high pressure has
shifted eastward over the Central Appalachians. This will lead
wedging with winds becoming more easterly across Central AL. A
moisture boundary will slide east to west through the day on
Friday. This likely won`t have much immediate impact to our
sensible weather, but the increased moisture could limit our
morning lows for Saturday to the upper 60s to low 70s.
The easterly flow becomes more important over the weekend and into
early next week. By Saturday evening, Tropical Storm Dorian is
forecast by NHC to be in the northern portions of the Bahamas, and
just off the southeastern coast of Florida. While we won`t see any
direct impacts from Dorian through the next 7 days in Central AL,
the tropical moisture is expected to lift northwestward due to the
easterly flow. Model guidance varies substantially on just how far
north that moisture gets this weekend, so I`ll keep PoPs on the
lower side (20-40%) through early next week due to the overall
uncertainty.
25/Owen
&&
.AVIATION...
00Z TAF Discussion.
We currently have a line of showers and thunderstorms moving
across Central Alabama stretching from southwest to northeast
across the area. Some of the storms could have gusty winds along
the start of the line. MVFR conditions are expected with the line
of storms. Behind it, a lingering large swath of cirrus extends
back to the northwest and will likely last for several hours
behind the storms. Skies should begin to clear from northwest to
southeast during the day Wednesday as drier air moves in behind
the front with northerly winds expected at the terminals. A few
gusts are possible during Wednesday afternoon.
08
&&
.FIRE WEATHER...
Rain chances remain elevated within a moist airmass, with light
rain or drizzle possible early Tuesday morning. Low clouds and fog
should be expected across the area this morning. Scattered to
numerous coverage is expected through the day ahead of an
approaching cold front. A few thunderstorms will be possible. With
the increased moisture, minimum relative humidity values will be
elevated as well through tonight.
A surface frontal boundary is expected to move into through the
area tonight. Although drier air will arrive, minimum relative
humidity values for the end of the week should still remain above
critical levels, with drier conditions for the end of the week.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 70 88 62 88 61 / 50 10 0 0 0
Anniston 71 89 63 89 63 / 50 10 0 0 0
Birmingham 72 89 64 90 65 / 40 10 0 0 0
Tuscaloosa 73 89 64 89 63 / 40 10 0 0 0
Calera 71 89 63 90 63 / 50 10 0 0 0
Auburn 72 89 67 90 68 / 30 10 0 0 0
Montgomery 74 91 67 92 68 / 40 20 0 0 0
Troy 72 90 67 92 67 / 30 20 0 0 0
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
None.
&&
$$
Area Forecast Discussion
National Weather Service Cleveland OH
943 PM EDT Tue Aug 27 2019
.SYNOPSIS...
A cold front will move east through the area this evening as
strong low pressure across western Ontario moves north to Hudson
Bay. High pressure will build east across the region Wednesday
through Thursday night. A weak cold front will settle south
through the area Thursday night into Friday before high pressure
builds east across the Great Lakes through the weekend.
&&
.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
Update...The RAP model shows a line of instability moving in
from the west this evening. Instability dampens out in the next
couple hours but radar shows a couple showers moving into OH
from Indiana. Will adjust pops east and drop from likely to
chance as activity thins but will also put a 20 pop back into
the forecast for the rest of the area through the first half of
the night to cover activity moving in. No other changes.
Original...Showers will continue to move east across the area
through this evening as a cold front moves east through the
region. Limited instability has greatly diminished thunder
chances, but held on to a slight chance mention in the forecast
over the next several hours. The front will push east of the
area late tonight into Wednesday morning, with drying conditions
expected across most of the region. Generally clearing skies
are expected as well, with lows tonight in the upper 50s west to
low 60s east. Surface high pressure will begin to build east
across the region on Wednesday, however an upper trough will
swing southeast across the Great Lakes Wednesday evening. Most
locations will be dry through Wednesday night, although some
modest lake induced instability and synoptic moisture may bring
a few showers to the snowbelt regions Wednesday night. Highs
Wednesday will be in the mid to upper 70s, with lows Wednesday
night dropping into the low to mid 50s inland, around 60s near
the lake.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
A surface high pressure system will be positioned over the
lower Ohio River Valley on Thursday with a southwesterly flow at
the surface over the area. In the mid and upper level weather
pattern, there will be a westerly to northwesterly flow with a
broad upper level trough over the north central U.S. into the
upper Great Lakes Region. Thursday afternoon will be breezy with
southwest winds 10 to 20 mph but the weather will be dry. The
broad upper level trough will expand southward across the Great
Lakes region by Thursday night into Friday. Another cold front
will move through the region on Friday with limited moisture and
cloud cover. There may be a few scattered showers with the
instability from diurnal heating and colder air aloft. There
will also be the chance for a few waterspouts near the lakeshore
with the warmer water temperatures of Lake Erie and colder air
aloft developing instability on Friday. Slightly cooler airmass
moves in Friday night into Saturday with temperatures running
about 5 to 10 degrees below average. Another shortwave will be
approaching our area late on Saturday from the west. We will see
clouds increasing from west to east Saturday afternoon.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
With a broad upper level trough north of our region and the area
will be in a fast westerly flow, another shortwave will be riding
through the flow Saturday night with limited moisture. We will see
some scattered showers Saturday night into Sunday along with mostly
cloudy skies. A weak area of high pressure moves in for Monday with
quiet weather with clearer skies and warmer weather. We will be on
the back side of a surface high pressure system with breezy south to
southwest winds on Tuesday and highs back in the lower 80s.
&&
.AVIATION /00Z Wednesday THROUGH Sunday/...
Cold front working east across the area this evening. Showers
and a few thunderstorms just ahead of the boundary will affect
KCAK, KYNG and KERI for the next few hours however expect CIG
restrictions to persist through much of the night before lifting
to VFR early Wednesday. Western terminals will remain VFR. VFR
expected on Wednesday across the area.
OUTLOOK...Non-VFR possible mainly northeast OH and nwrn PA late
Thursday night and Friday in showers associated with a passing
cold front.
&&
.MARINE...
A fast pace and sorta unsettled weather is expected to impact Lake
Erie over the next 5 to 7 days with gusty and changeable winds as
well at times higher wave action. A cold front will move across the
lake this evening with winds shifting to the west at 10 to 15 knots.
Westerly winds will increase on Wednesday as well as wave heights.
Winds will be likely 15 to 25 knots and waves increasing to 3 to 6
feet. A Small Craft Advisory will likely be needed for Wednesday
across the nearshore waters. Gusty southwesterly winds 15 to 20
knots will continue into Thursday. Another cold front moves into the
region Thursday night with winds possibly increasing ahead of the
frontal passage and close to SCA conditions again Thursday evening.
One note to add with the frontal passage late Thursday night and
Friday will be the potential for a few waterspouts on the lake with
the warmer water temperatures and the colder air aloft developing
some decent instability on Friday. The front moves through with
weaker northwesterly flow 5 to 10 knots on Friday. Weak high
pressure builds in over the lake Friday night and Saturday. Strong
gusty southwesterly winds 15 to 25 knots return over the lake by
early next week.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.
&&
$$
SYNOPSIS...Greenawalt
NEAR TERM...Greenawalt/TK
SHORT TERM...Griffin
LONG TERM...Griffin
AVIATION...TK
MARINE...Griffin
Area Forecast Discussion
National Weather Service El Paso Tx/Santa Teresa NM
320 PM MDT Tue Aug 27 2019
.SYNOPSIS...
Tuesday afternoon has likely brought us our last 100 degree day
for a while, and is also bringing an uptick in thunderstorm
activity. Wednesday will bring slightly cooler temperatures, with
lowland highs in the 90s, and one of the more active thunderstorm
days of the summer. Slow moving thunderstorms will result in
highly localized heavy rainfall during the afternoon and evening.
We will remain in a moist and unstable pattern all the way through
Saturday, with some drier and warmer air aloft expected to
diminish thunderstorm activity early next week.
&&
.DISCUSSION...
Surface analysis and visible satellite imagery suggests the
backdoor cold front has stalled out just east of the Sacramento
and Guadalupe Mountains, but a prefrontal trough or wind shift
line, with increased moisture behind it, has pushed up to the Rio
Grande. Behind this boundary, dewpoints are in the 50s, while 40s
are more common further to the west (except in the NM Bootheel).
RAP analysis shows moderate to strong instability behind the
boundary, with MLCAPE values of 1500-2500 J/Kg over parts of
Otero, El Paso, and Hudspeth Counties. However, strong capping
remains in place, as suggested by the lack of significant cu
development on satellite imagery, and supported by RAP analysis
CIN values of -20 to -60 J/Kg.
However, there has been some minor development in the past hour
over parts of southern Hudspeth County and nearby mountains south
of the border, and stronger storms over parts of Presidio County.
A few of the CAMS models which are handling on-going convection
well, notably both the 12Z NAM and GFS-initialized UofAZ WRF runs,
suggest convection will break the cap over Hudspeth County in the
next couple of hours, perhaps aided by outflow from stronger
storms over Presidio County. The models then suggest outflow from
these storms, aided by a further westward push of the backdoor
cold front early this evening, will interact with weak outflow
from sparse convection N and W of ELP and LRU, triggering more
widespread thunderstorms over south-central NM and Far West Texas
early this evening. Given that the wind shift line/prefrontal
trough is sitting over the Rio Grande Valley, this solution is not
entirely far-fetched.
Low level East to SE flow will continue to advect low level
moisture into the region overnight, and by late morning tomorrow
(Wed), PW values look to range from about 1.15 inches in the far
western reaches of the CWA, to around 1.40 inches along and east
of the Rio Grande. The GFS suggests 500mb temperatures around -6
to -7C, increasing instability with SBCAPE values over 2000 J/Kg
east of the Rio Grande, and a weak shortwave trough rounding the
eastern edge of the subtropical ridge during the afternoon. Expect
the usual diurnal trend of orographic showers and thunderstorms,
with weak to moderate capping in the lowlands limiting lowland
thunderstorm development until late afternoon and early evening as
outflow boundaries interact in the lowlands. Convection may be
further aided by the weak shortwave trough. Overall Wednesday
looks like one of the more active days of the season so far.
The overall pattern will remain unchanged on Thursday, with the
subtropical ridge focused off to our west. While the E to SE low
level flow is cut off, plenty of recycled moisture will remain in
place, with PW values ranging from 1.15 to 1.25 inches. Mid-level
temperatures look to moderate somewhat, due to widespread
convection the previous day. Overall thunderstorm chances will be
closely limited by leftover convective debris/stabilization from
the previous day`s thunderstorms, but should still be fairly
active.
Similar conditions will persist on Friday, with recycled moisture
remaining in place. As the upper ridge shifts back towards the
Four Corners, we`ll end up in E to NE flow aloft. Thunderstorm
coverage still looks to be fairly active, aided by slightly cooler
mid-level temps moving into the area.
Drier and warmer air aloft still looks like it will filter into
the area Sunday and Monday, diminishing overall thunderstorm
chances, but not eliminating them entirely (higher elevations will
still be favored).
Towards mid-week, the crucial details remain fuzzy, but there`s a
chance that a trough digging into the west coast and an eastward-
shifting ridge will try to pull up some additional moisture into
some part of the Desert Southwest, but areas west of the
Continental Divide will likely be more favored.
&&
.AVIATION...Valid 28/00Z-29/00Z...
P6SM FEW-SCT080-100 SCT-BKN150-200 through period. Isolated to
scattered VRB25G40KT 1-3SM TSRA BKN030-040 through the night, then
storm coverage increasing to scattered lowlands to numerous
mountains after 18Z. Winds generally east to southeast 5-15KTS but
variable and gusty near thunderstorms.
&&
.FIRE WEATHER...
Low and mid level moisture has started to move into the region
behind a weak boundary moving westward. Enough moisture will remain
over the area into the weekend to bring a daily chance for showers
and thunderstorms. The best chances for widespread wetting rains for
the lowlands and mountains looks to be tomorrow. Storms are not
expected to be severe but will have the potential to produce locally
heavy rain and flooding. Temperatures for the remainder of the
forecast period will be dropping to near normal with minimum
relative humidities remaining above 20 percent for the lowlands and
above 25-30 percent in the mountains. Winds will remain under 15 mph
except gusty near thunderstorms.
&&
.PRELIMINARY POINT TEMPS/POPS...
El Paso 74 95 71 93 / 40 30 50 10
Sierra Blanca 69 90 67 90 / 30 40 40 10
Las Cruces 70 93 67 92 / 40 30 60 10
Alamogordo 69 95 67 94 / 30 40 40 20
Cloudcroft 53 72 53 71 / 40 70 40 40
Truth or Consequences 71 94 67 94 / 30 50 40 30
Silver City 65 89 62 88 / 20 60 50 60
Deming 70 96 67 93 / 20 30 60 20
Lordsburg 70 96 67 94 / 20 30 50 20
West El Paso Metro 74 97 71 94 / 40 30 50 10
Dell City 70 93 68 96 / 30 30 40 10
Fort Hancock 75 98 72 96 / 30 30 50 10
Loma Linda 69 88 66 88 / 30 40 50 10
Fabens 75 96 71 93 / 30 30 50 10
Santa Teresa 71 95 68 93 / 40 20 50 10
White Sands HQ 73 94 70 94 / 40 30 60 10
Jornada Range 69 94 67 93 / 40 30 60 10
Hatch 70 95 66 94 / 40 40 60 20
Columbus 72 96 69 93 / 20 20 60 10
Orogrande 70 93 68 92 / 30 30 50 10
Mayhill 58 79 57 81 / 40 70 40 40
Mescalero 56 81 55 81 / 30 60 40 30
Timberon 57 78 55 79 / 40 60 50 30
Winston 59 87 57 86 / 20 70 50 60
Hillsboro 66 93 63 92 / 30 60 60 50
Spaceport 67 93 64 93 / 40 40 50 20
Lake Roberts 59 89 56 88 / 20 70 50 70
Hurley 64 91 62 89 / 20 50 60 40
Cliff 63 98 61 96 / 20 60 50 50
Mule Creek 66 93 65 90 / 20 50 50 50
Faywood 67 91 64 90 / 20 50 60 40
Animas 69 97 67 95 / 20 40 60 20
Hachita 68 96 66 93 / 20 30 60 10
Antelope Wells 68 95 65 92 / 30 50 70 30
Cloverdale 67 90 64 87 / 20 60 70 40
&&
.EPZ WATCHES/WARNINGS/ADVISORIES...
NM...None.
TX...None.
&&
$$
25-Hardiman / 26-Grzywacz
Area Forecast Discussion
National Weather Service Hastings NE
634 PM CDT Tue Aug 27 2019
.SHORT TERM...(This evening through Wednesday night)
Issued at 448 PM CDT Tue Aug 27 2019
Before getting into the breakdown of "short term" versus "long
term" below, wanted to make a general, one sentence description of
the 7-day forecast as a whole: We are looking at a mainly dry
first few days and a dry last few days, with decent potential for
a wet/stormy period in between (centered on Thurs night-Saturday).
Now getting specifically to "short term" and focusing on solely
these next 36 hours (three forecast periods), we are looking at a
rather high-confidence dry forecast beyond this evening`s spotty
light showers/sprinkles. Temperature-wise, tonight is slated to be
the overall-coolest night much of our coverage area (CWA) has seen
since the first half of June, but then followed by a decent warm-
up tomorrow with highs climbing roughly 10 degrees higher than
today`s rather coolish values.
Taking a look at the current/recent weather scene as of 345 PM:
Overall, no surprises to speak of today at all, as things are
largely on track from the early-AM forecast issuance. As expected,
skies over most of the CWA clouded up fairly appreciably as the
day went on, following the sunny start. Furthermore, a smattering
of high-based sprinkles and light showers have affected various
areas, with with the most concentrated coverage of this activity
currently focused within our southwest half. The cool start
followed by increasing clouds will keep most areas down in the
upper 60s-low 70s for afternoon highs, although much of our KS
zones along with Hebron area managed to reach the mid 70s due to a
bit more sunshine. At the surface, high pressure is currently
centered over western Nebraska, and breezes today locally have
generally averaged 5-15 MPH from the west-northwest, with some
higher gusts at times especially north and east. In the mid- upper
levels, water vapor satellite imagery along with short term model
data reveal west-northwest flow over our region, in between a
seasonably- strong trough centered from from Ontario into the
Great Lakes and a ridge over the southwestern CONUS. Our pesky
sprinkles and passing brief rain showers are being promoted by a
fairly subtle zone of mid level lift/saturation along the
southwestern periphery of the aforementioned large scale trough.
Somewhat odd for this time of year (and in sharp contrast to
recent weather), there is hardly any convective instability, and
while the risk of a rogue/isolated lightning strike late this
afternoon is not truly zero, it is also not worthy of a formal
"thunderstorm" mention in forecast products, and thus am only
indicating light rain showers and/or sprinkles. While most areas
don`t need ANY rain given ongoing/recent flooding, this is a VERY
MINOR rain "event", and would be very surprised to see anybody
measure more than 0.05".
Now looking ahead forecast-wise through these next 3 periods...
This evening/tonight:
See previous paragraph for more details on the continued chance of
sprinkles/light passing rain showers into the first part of the
evening. Expect the vast majority of this activity (if not all of
it) to be fade away by 10 PM or so, and have a dry forecast going
beyond that. Current expectation is for skies to gradually clear
from north-northwest to south-southeast as the evening wears on,
with the post-midnight hours clear to mostly clear all areas.
Interestingly, the latest RAP appears a bit more aggressive
keeping pesky mid cloud over our south (mainly KS zones) later
into the night, so this will need watched. Otherwise at the
surface, the stage is set for what will likely be the coolest
night since early-June for most of our CWA, as light westerly
breezes average no more than 4-8 MPH most of the night in the
presence of the passing surface ridge axis. Low temps are aimed
from upper 40s far north (Ord area) to mid 50s along/south of the
state line, with low 50s in between for places such as the Tri
Cities.
Wednesday daytime:
Confidence is high in a dry and mostly sunny day with temps
climbing 10+ degrees warmer than today in most areas. In the mid-
upper levels, west-northwest flow persists, but with no subtle
disturbances of note such as today. At the surface, high pressure
departs southeast into MO over the course of the day, allowing
return flow southerly breezes to overtake our CWA, with sustained
speeds generally 10-15 MPH with some higher gusts to around 20
MPH at times. High temps are aimed into the low 80s most areas,
with mid 80s more common far south/southwest (mainly KS zones).
Wednesday night:
Although the forecast is not necessarily "guaranteed dry" (mainly
per the GFS), chances of rain are well under 20 percent at any
given location and thus not worthy of forecast inclusion.
Following the preferred NAM solution, we will most likely see a
dry night with light-but-steady southerly breezes generally around
10 MPH with some occasional higher gusts. The warmer airmass and
southerly breezes should keep low temps a solid 7-13 degrees
warmer than tonight, with lows aimed into the low 60s most areas.
.LONG TERM...(Thursday daytime through Tuesday)
Issued at 448 PM CDT Tue Aug 27 2019
General overview of this 6-day period (preciptiation):
As mentioned at the top, we are looking at a fairly unsettled
stretch Thurs evening-Saturday, followed by what currently appears
to be a return to drier and warmer weather Sunday-Tuesday.
Unfortunately, concerns are gradually increasing that we could be
looking at some unwelcome heavy rain during the Thurs night-
Saturday time frame. Although too early to pin down details,
latest models and WPC QPF forecasts are suggestive of a fairly
widespread 1-3" over most of the CWA, with perhaps our southern
zones perhaps a bit more favored for higher amounts (although this
is very preliminary/general). There also looks to be a chance for
strong to at least marginally-severe storms, particularly
Thursday evening and perhaps again Friday afternoon-evening.
Although not in place yet, would not be surprised at all to see
one or both of these days highlighted in a Marginal Risk of severe
storms by SPC in later outlooks. This roughly 2-day stretch of
unsettled weather looks to be driven by low-amplitude disturbances
working their way around the northeast periphery of high pressure
to our southwest, interacting with moisture/instability pooling
along a somewhat stalled-out, west-to-east surface frontal
boundary. At least for now, the Sunday-Tuesday time frame is
carrying a dry forecast, as the southwestern CONUS upper ridge
looks to build northeast enough into our region to give us another
break from storms. However, cannot guarantee that every one of
these periods stays dry in later forecasts.
Temperature-wise:
Right away Thursday daytime, we are calling for the overall-
warmest day of the entire 7-day forecast, as most of the CWA warms
into the mid 80s ahead of a cold front approaching from the north,
with some low 90s likely far southwest. Then, things cool fairly
noticeably for Friday-Saturday due to a combination of cooler air
north of the stalling front, easterly winds, rainfall etc. More
specifically, highs are mainly aimed low-mid 70s. As more tranquil
weather returns Sunday-Tuesday, temps look to gradually rebound,
with highs preliminarily aimed around 80 most areas by early next
week, with mid 80s more common southwest. Overnight lows most
nights look to average between the upper 50s and mid 60s, which is
right on par with late-August/early-September norms.
In closing:
Stay tuned for more and more details regarding the strong
storm/heavy rain potential for Thurs night-Saturday as it gets
closer. It`s just a bit too soon to have much confidence in the
"exact" placement and intensity of rainfall and possible flooding
issues, but it bears watching.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 619 PM CDT Tue Aug 27 2019
VFR conditions will prevail at both terminals through the period.
Plenty of mid level clouds streaming across south central Nebraska
this evening...and expect this continue for the next few hours.
While the clearing line is not too far north of either
terminal...with steady west northwest flow continuing
aloft...expect the edge of this cloud deck to remain north of
both terminals through around 28/03Z as these clouds erode. Skies
will then become mostly clear overnight...with light westerly
surface winds helping to keep the potential for any fog
development at bay, despite temperatures falling to near dewpoint
values by daybreak. Winds will eventually shift and become
southerly by early afternoon across the region Wednesday as the
surface ridge transitions east and southerly return flow is
realized.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
SHORT TERM...Pfannkuch
LONG TERM...Pfannkuch
AVIATION...Rossi
Area Forecast Discussion
National Weather Service Green Bay WI
1049 PM CDT Tue Aug 27 2019
Updated aviation portion for 06Z TAF issuance
.SYNOPSIS...
Issued at 244 PM CDT Tue Aug 27 2019
Scattered thunderstorms continuing into this evening, then a
chance of a few more storms Thursday afternoon and evening. Quiet
weather with seasonable temperatures is expected for the Labor
Day Weekend.
The amplified large scale flow regime anchored by a deep upper
trough/closed low over western Ontario will persist for another
day or so, then a gradual deamplification will begin. Some
readjustment of the large scale features will occur as well, so
that by the upcoming holiday weekend the flow will be
characterized by a trough just off the West Coast, ridging over
the Intermountain West, and broad troughing over eastern Canada
and the northeastern United States.
The upper pattern will support a few rounds of scattered
convection, but probably not enough to produce normal amounts for
most locations. Temperatures will fluctuate between modestly
below and modestly above normal, but a prolonged/significant
departure from normal is unlikely.
&&
.SHORT TERM...Tonight and Wednesday
Issued at 244 PM CDT Tue Aug 27 2019
The latest RAP analysis and satellite/radar imagery show a potent
shortwave moving into western Wisconsin early this afternoon.
First cluster of showers and storms moved over far north-central
WI around the noon hour, with numerous reports of pea sized hail
over Vilas and Oneida counties. Other scattered showers/storms
are popping up over northeast WI, and short range models indicate
the area will see an increase of coverage of storms through the
rest of the afternoon. This aligns well with the growing most
unstable cape values of 800-1200 j/kg over the northwest half of
the area. Given the cold temps aloft and a well mixed boundary
layer, any storms will be capable of producing up to dime sized
hail and gusty winds to 40 mph. An isolated severe storm cannot be
ruled out either. As upper troughing settles over the area, precip
and cloud trends will be the main forecast concern through
Wednesday.
Tonight...The relatively beefy shortwave will be exiting
Wisconsin into Lake Michigan during the first half of the evening.
With subsidence behind this wave and loss of daytime heating, will
see shower and storm coverage diminish in the 7 pm to 10 pm time
range. Storm intensity should have already peaked prior this, but
an isolated strong storm (gusty winds and small hail) could
persist into early this evening. Then after a brief period of
clearing, low clouds currently over the northern Plains will
spread southeast across the region overnight. A few light showers
or sprinkles will be possible across the northwoods with these
clouds. The tight pressure gradient and cloud cover will prevent
temps from falling somewhat, and will go with lows ranging from
the low to mid 50s.
Wednesday...The upper trough axis will be overhead during the
morning, then shift east of the area in the afternoon. Should
therefore see plenty of clouds around in the morning, with light
showers at times over far northern WI. Clouds should then
generally erode from west to east during the afternoon. It will be
a cool and blustery day with highs ranging through the 60s.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 244 PM CDT Tue Aug 27 2019
A significant shortwave will swing around the southern flank of
the Ontario upper low as deamplification begins. That will drive
a cool front into the area Thursday. Strengthening low-level
southwest flow ahead of the front will result in a modest return
of moisture. Suspect the mid to upper 60F surface dew points
depicted on the NAM and GFS are overdone, with upper 50s or lower
60s more likely. That will make it a little difficult to get
surface-based convection to fire given the warm temperatures in
the 850-800 mb layer on model soundings, and may result in limited
storm coverage. It still seemed worthy of carrying low chance
PoPs as in previous forecasts.
Gradually rising upper heights are expected once the shortwave
passes through. An anticyclone from southern Canada will build
toward the region Friday, then remain sprawled across the region
for most of the holiday weekend. A wave on the frontal system
south of the area will push east from the Plains Saturday and
Saturday night, but precipitation with that feature should stay
south of the area.
The default forecast initialization grids based on a broad-based
blend of guidance products seemed reasonable for temperatures so
no significant adjustments were necessary.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1049 PM CDT Tue Aug 27 2019
Mostly clear skies will give way to mostly cloudy skies as an area
of clouds across Minnesota advects east through the TAF sites
overnight and into Wednesday morning. Conditions are expected to
fall to MVFR across central and north-central Wisconsin, but
remain VFR across east-central Wisconsin. These clouds will hang
around for much of the day on Wednesday, with clearing skies
during the late afternoon and early evening hours as drier air
works its way in from the west.
Some LLWS is expected this evening over parts of north central,
central and far northeast WI, then diminish overnight. West winds
will pick up again on Wednesday, with gusts again around 25 knots
at most locations throughout the daytime hours.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS.......Skowronski
SHORT TERM.....MPC
LONG TERM......Skowronski
AVIATION.......Kurimski
Area Forecast Discussion
National Weather Service Nashville TN
755 PM CDT Tue Aug 27 2019
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Radar imagery this hour shows showers and thunderstorms generally
concentrated across our northern and northeast counties. Have
tweaked pops for the next few hours to show likely precip chances
in these areas, with just slight or low chance pops elsewhere due
to the lack of coverage. Latest HRRR model indicates most of the
precip will be east of our forecast area by midnight and have
removed pops after 06Z. Only minor other changes were made based
on latest obs, which still show a warm and humid airmass
entrenched across Middle Tennessee with temps in the 70s to low
80s and dewpoints in the yucky 70s. A much drier airmass with
dewpoints the 60s and even the 50 is currently about halfway
between STL and PAH and will move across our region overnight,
bringing a very comfortable and unhumid end to August 2019.
&&
.AVIATION...
00Z TAF DISCUSSION.
Latest radar shows scattered showers will be near airports for a
few more hours this evening with CSV most likely to be impacted
between 01-04Z. VFR conditions will prevail at BNA/MQY/CKV
tonight but CSV will see falling cigs through the night with LIFR
cigs/visibility by sunrise. Light west winds will become
northwest/north overnight as a weak fropa moves through the area.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......Shamburger
AVIATION........Shamburger
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
800 PM EDT Tue Aug 27 2019
.UPDATE...
Latest RAP model shows mid level ridging dominating the Gulf of
Mexico. At the surface a bubble high in the Gulf and troughing
east of FL will maintain light west and northwest lower level
flow overnight. The rather robust mid-afternoon showers and
thunderstorms have pushed east and are dissipating over the
Atlantic coastal counties. Anticipate late night convection
forming on the Gulf and traversing coastal location around
sunrise then inland areas in the late morning and afternoon...
similar to today. Forecasts for tonight are on track with little
changes needed.
&&
.AVIATION...
28/00Z TAF cycle. Afternoon convection has wound down and moved
east of the terminals with VFR clouds for much of the night. Late
night Gulf convection begins to impact the coastal sites...with
VCSH AFT 09Z and VCTS AFT 14Z that exit to the east AFT 20Z.
Prevailing winds W or NW at no more than 10KT.
&&
.MARINE...
High pressure resides over the waters for the next few days with
westerly or northwesterly winds gradually becoming easterly.
Tropical Storm Dorian begins to approach during the weekend...
please monitor the latest forecasts and information from the
National Hurricane Center.
&&
.Preliminary Point Temps/PoPs...
TPA 78 90 78 93 / 20 40 20 60
FMY 77 91 76 91 / 20 30 20 60
GIF 76 92 76 93 / 10 40 20 60
SRQ 77 90 77 92 / 20 30 20 60
BKV 76 91 75 94 / 20 30 20 50
SPG 78 88 78 92 / 20 30 20 60
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...None.
&&
$$
UPDATE/AVIATION/MARINE...09/Rude
UPPER AIR...42/Norman
DECISION SUPPORT...69/Close
Area Forecast Discussion
National Weather Service Las Vegas NV
826 PM PDT Tue Aug 27 2019
.SYNOPSIS...Warm overnight lows will occur under mostly clear
skies. Isolated thunderstorm activity will return Wednesday across
portions of the southern Great Basin and northwest Arizona. High
pressure will remain over the Southwest through the rest of the week
resulting in mostly clear skies and a continuation of hot
temperatures. Some relief from the heat could be in store for the
region as we transition into September.
&&
.UPDATE...The afternoon Las Vegas sounding showed a decent increase
in moisture below 500 mb from this morning. Precipitable water value
this morning of 0.82" rose to 1.31" this afternoon. That increase in
moisture generated greater instability aiding in the development of
isolated thunderstorms over Mohave, Clark and the southern Sierra
Nevada. All the action has dissipated with satellite showing the
cirrus associated with the anvils dissipating. The rest of the night
will be warm and clear.
For Wednesday: HRRR and other convective allowing models showing
greatest convective potential will exist across northern Mohave
County, as well as northern Inyo and Esmeralda Counties. This is
covered well in the current forecast.
&&
.DISCUSSION...Temperatures, as advertised, have reached near-record
temperatures despite dewpoints in the 50s. Dangerous temperatures
are forecast to continue through at least Wednesday, possibly
longer. Confidence is growing that southwest flow following behind
mid-level moisture on Wednesday will allow overnight lows to cool
more efficiently limiting warm overnight lows and heat impacts.
Highs may not fluctuate much through the weekend, with afternoons
reaching 5-8 degrees above normal each afternoon. There is
increasing confidence that heat impacts will continue through the
weekend, which may warrant a continuation of heat headlines. That
said, the Excessive Heat Warning remains unchanged.
A few isolated showers and thunderstorms have developed across parts
of the Mojave Desert, mainly Mohave County, this afternoon amid
increasing mid-level moisture. High-based thunderstorms should stay
anchored to the terrain through the evening with very little
steering flow available. The main threat with any storms that
develop will be gusty outflows; current downdraft CAPE of 1500-2000
J/kg along with very steep low-level lapse rates suggest outflow of
30-45 MPH are possible. Further northwest over the southern Sierra,
convective initiation has yet to occur but isolated to scattered
storms are expected to develop late this afternoon and may linger
through the evening. Elsewhere, flat or limited cumulus is expected
to continue. Generally, most activity is expected to wane this
evening with the loss of daytime heating.
Dry southwesterly flow will push most of the mid-level moisture to
the northeast on Wednesday. As it does, afternoon storm chances will
be limited to the northern periphery of the CWA. By Thursday,
chances for convection will be nil across the area as dry
southwesterly flow continues over the areas. Model signals are
indicating that the next potential push of moisture will be early
next week as the ridge shifts east over the Four Corners. Confidence
is low but the signal has been fairly consistent over the past few
runs, so confidence is increasing.
&&
.FIRE WEATHER...A mix of dry and wet thunderstorms is possible
Wednesday, primarily affecting the northern tier of Mohave County.
A Red Flag Warning has been issued for AZ-102 with the main
concern being dry lightning and gusty outflow. Isolated storms may
also be possible across portions of the southern Great Basin and
the southern Sierra; however, confidence in sufficient storm
coverage is low. Elsewhere, dry and hot conditions will continue
with afternoon breezes increasing. By Thursday and through the
weekend, dry and hot conditions along with afternoon breezes from
the south are expected.
&&
.CLIMATE...Forecast highs will be within 1 to 3 degrees of
record values for Las Vegas and Death Valley today through
Wednesday. The following are the official daily record high
temperatures for August 26-28:
TUE 8/27 WED 8/28
Las Vegas 110 (2017) 110 (2017)
Death Valley 124 (1924) 124 (2011)
&&
.AVIATION...For McCarran...Light, easterly winds will slowly veer
around to the southwest late this afternoon into this evening with
wind speeds generally staying 10 knots or less. There is the
possibility of some isolated virga developing over the higher
elevations south and west of the terminal which could push out some
briefly gusty winds between 23z-03z. Confidence is low in this
occurring. Wednesday will see an earlier onset of southerly winds
between 21z-00z with speeds of 10-13 knots and gusts of 15-20 knots
possible.
For the rest of southern Nevada, northwest Arizona and southeast
California...In general, winds will remain less than 15 knots
favoring the southerly direction mid to late this afternoon through
early evening. Isolated showers and virga will be possible later
today aross Inyo, central Mohave, and the higher elevations of Clark
counties. Briefly stronger, gusty winds will be possible in the
vicinity of this activity. Similar activity will be possible
Wednesday afternoon across central Nevada and northern Mohave
County. Slightly stronger south to southwesterly winds are expected
to develop on Wednesday afternoon with speeds of 10 to 15 knots
gusting 15 to 25 knots.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
UPDATE...Pierce
DISCUSSION...Boothe
AVIATION...Guillet
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