Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/21/18
Area Forecast Discussion
National Weather Service Binghamton NY
935 PM EDT Mon Aug 20 2018
.SYNOPSIS...
Low pressure will move west of the area Tuesday into Wednesday
bringing showers and isolated thunderstorms to the area late
Tuesday and early Wednesday. High pressure with drier air will
move in for the end of the week.
&&
.NEAR TERM /THROUGH TUESDAY/...
With the late evening update we made some adjustments to the
sky cover based on ongoing conditions. Also temperatures have
fallen off fairly quickly as well the last couple of hours and
were adjusted slightly with both evening updates. However, the
forecast in large part remains on track with the previous
discussion below.
Low over NE Indiana Tuesday morning races northeast as it
deepens, to southern Quebec by Wednesday morning. Ahead of the
system, Atlantic moisture with marine layer is drawn north into
the area bringing low level moisture and low clouds later
tonight into Tuesday.
Upper level warm front pushes through late Tuesday and should
generate some light showers. Models have backed off on the
heavier rains forecast as they weaken the convection as it runs
east. Part is due to the lack of any low level instability, and
mid level dry air. Behind that, a cold front races east in the
early morning hours Wednesday. Again the models have backed off
on the QPF amounts with only marginal instability and the upper
jet support passing well to the north and west. With the late
evening update, we also delayed the onset of precipitation into
the morning given the latest HRRR, RAP and RGEM now hold off any
rain chances getting into the Finger Lakes till late morning.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/...
3 am update...
A cold front will be racing east of our region with a broad mid-
level trough over the region on Wednesday. Modeled soundings do show
some steeping of the low-level lapse rates with the northwest flow
pattern also contributing a little bit of moisture as well. These
factors may lead to a few additional spotty showers throughout the
day. The main story will be the northwest winds behind the front
with the potential for a few northwest wind gusts around 20 mph in
the afternoon hours. With a mostly cloudy and northwest flow, highs
will struggle to get well into the 70`s.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Wednesday night through Friday night: High pressure from Canada will
build into the region Wednesday night and Thursday resulting in a
period of much needed dry and refreshing weather across the region.
Northwest winds will gradually decrease as the high builds in.
Highs should be in the 70`s with lows in the 50`s. With
favorable conditions for radiational cooling with the high
overhead Friday morning a few spots may actually fall into the
upper 40`s for morning lows. Some patchy fog is possible Friday
morning as well.
High pressure slowly starts to move out Saturday, with one last dry
day expected. Morning lows are expected to fall into the upper
50s/low 60s and highs generally reach in the mid to upper 70s and
low 80s.
Saturday night, our area starts to get into the return flow behind a
surface high, and a surface low and associated mid-level trough move
through Ontario and Quebec. This results in increasing clouds and
chances for showers Saturday night. The Euro continues to be the
outlier, bringing this feature through more quickly with showers
beginning as early as Saturday afternoon. For Sunday and Monday,
warmer and more moist air works in with S/SW flow near the surface.
Weak waves continue to pass through, with mainly westerly flow
aloft, and lingering chances for showers both days. Thunder will be
possible during the afternoon and evening hours owing to better
instability. With PWATs in the 1-1.5in. range, a heavy downpour is
not out of the question - and with little shear to speak of, slow-
moving cells could be a concern. However, there is little forcing
apart from any weak shortwaves, so this isn`t looking like a
widespread heavy rain event. Lows generally will be in the
low/mid 60s Sunday morning, with highs likely in the upper 70s
and low 80s. Continued warming Monday should bring in lows in
the mid/upper 60s and highs in the low/mid 80s as dewpoints
increase into the 60s and low 70s.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
A southeast flow overnight will bring low level moisture into
most of the terminals. For all terminals but KSYR, ceilings
will lower into the MVFR/Alternate Required category between
03Z-09Z. The restricted ceilings will remain through the
morning hours then a warm front during the afternoon will
produce MVFR/Alternate Required showers at all terminals.
E/SE winds overnight at 5-8 knots. S/SE winds developing by late
morning Tuesday at 8-12 knots with gusts around 18 knots.
Outlook...
Tuesday night into Wednesday...Restrictions probable in showers
and thunderstorms.
Wednesday afternoon through Saturday...VFR. Early morning fog
possible, especially KELM.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.
&&
$$
SYNOPSIS...DGM
NEAR TERM...DGM/MWG
SHORT TERM...MWG
LONG TERM...HLC/MWG
AVIATION...RRM
Area Forecast Discussion
National Weather Service Bismarck ND
957 PM CDT Mon Aug 20 2018
.UPDATE...
Issued at 952 PM CDT Mon Aug 20 2018
Decreased lows into the lower 40s north of US Highway 2 where
skies will clear late tonight. Also increased PoPs across the
southwest and south central for the overnight per the 00 UTC CAM
suite and upstream radar trends across Montana.
UPDATE Issued at 637 PM CDT Mon Aug 20 2018
Little change with this forecast update. Expect rain showers to
spread into southwest North Dakota between 02-04 UTC from
southeast Montana with a series of impulses that will phase
overnight with a northern stream shortwave.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 222 PM CDT Mon Aug 20 2018
The return of smoky skies and continued cool conditions highlights
the short term forecast.
Regarding the smoke: The vertically integrated smoke product, from
the latest iterations of the RAP and ESRL HRRR Smoke models, suggest
that smoke will continue to be on the increase from the west today,
and spread east through tonight, likely lasting until at least
daybreak Tuesday when the model forecasts some clearing of smoke
from north to south.
Today North Dakota was between 3 upper level low pressure systems:
the first an upper level low over Hudson Bay, keeping broad cyclonic
flow across south central Canada and Northern North Dakota; the
second a closed low over the mid-Mississippi Valley; and the third
upper level trough over the western/central US Rockies. Upper level
impulses emerging from the western/central US Rockies trough were
moving east across Montana and Wyoming today. This was associated
with the shower activity seen on regional radars over MT/WY.
Tonight a shortwave in the northwest flow aloft over south central
Canada will track southeast across North Dakota. As this occurs,
upper level impulses emerging from the western/central US Rockies
trough continue moving east across Wyoming and South Dakota,
clipping far southern North Dakota. The short term high res and
global models agree putting scattered showers and thunderstorms
across southwestern North Dakota tonight, moving southeast out of
our area during the morning hours on Tuesday.
Meanwhile at the surface: A large cool and dry high pressure system
was centered over Alberta and Saskatchewan, with a narrow axis
extending south across the western Dakotas and eastern MT/WY. Clear
skies, light winds, and dry air combined to bring low temperatures
ranging from 35F to the mid 40s across most of western and central
North Dakota.
Tonight the high pressure system is forecast to move southeast into
eastern Montana and the Dakotas. Increasing clouds are forecast from
west to east tonight, especially across the southern counties,
associated with the upper level impulses and aforementioned chances
of showers. Thus expecting widespread lows in the 40s again across
western and central North Dakota, with some upper 30s possible
across portions of the north under clearing skies. Slightly warmer
Tuesday, with highs mainly in the 70s.
.LONG TERM...(Tuesday night through Monday)
Issued at 222 PM CDT Mon Aug 20 2018
The west coast trough begins to close off and meander slowly east
Tuesday night and Wednesday, keeping a weak upper level ridge over
our area. The large surface high pressure drifts southeastward, with
return southerly flow becoming established over our area on
Wednesday. This will allow a gradual warmup through the week, with
high temperatures as high as 80 by Thursday.
Thursday: The upper level Rockies closed low will finally make its
way to the northern plains by Thursday, bringing chances for showers
and thunderstorms across the area by the afternoon hours. Decent
instability will likely be available, with moderate 0-6km shear up
to 30 knots possible. At this time the Storm Prediction Center is
targeting eastern SD/NE for possible severe storms, but some strong
storms over the eastern half of North Dakota cannot be ruled out
Thursday afternoon and evening.
After the upper low kicks out of the region on Friday, the pattern
looks to become a bit more progressive, with models in agreement
of a fast zonal flow transition, leading to a deepening trough
across the western US by the end of the weekend. Periodic chances
of showers and thunderstorms will be possible across the region
over the weekend, but the global models do not seem to have a
solid handle of the fine scale details at the moment.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 952 PM CDT Mon Aug 20 2018
Rain will continue to spread across southwest and south central
North Dakota through the night, decreasing after 09 UTC. A few
embedded MVFR visibilities are possible within the heavier rain
showers. KDIK is the most likely terminal to be impacted. KBIS
will be on the northern fringe of the rain showers. Otherwise, VFR
conditions are forecast for the 00 UTC TAF cycle across western
and central North Dakota with surface high pressure.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...PA
SHORT TERM...JV
LONG TERM...JV
AVIATION...PA
Area Forecast Discussion
National Weather Service Denver/Boulder CO
811 PM MDT Mon Aug 20 2018
.UPDATE...
Issued at 757 PM MDT Mon Aug 20 2018
Smoke continues along the front range and actually
has gotten somewhat worse this evening. latest HRRR
Smoke Model continues to show this smoke lingering
overnight but should see improvement by Tue morning.
As far as pcpn there is quite a bit of activity over Utah
this evening which appears to be associated with an upper level
jet. This activity will affect nrn areas of the higher terrain
after midnight and across lower elevations mainly near the
CO-WY towards sunrise.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 252 PM MDT Mon Aug 20 2018
Smoke remained across most of the plains this afternoon, with the
most concentrated smoke along the I-25 Corridor where the light
easterly flow has banked it up against the Front Range. There has
been some improvement late this afternoon with daytime heating and
mixing. Higher up, including the foothills above about 7500 feet
and across the mountains, the smoke has mixed sufficiently and is
relatively thin as a more westerly component takes hold. We`ll
still see some smoke/haze around through the night in the lower
elevations, but we do expect some improvement by Tuesday morning
and especially Tuesday afternoon when more mixing occurs and we
get a few showers/storms pushing east across the forecast area.
With regard to the precipitation threat, we do expect that to
increase across the mountains by midnight and the northern border
area thereafter tonight. Those showers will be driven by a passing
speed max to our north and mid level moisture advection as noted
in the specific humidity progs. There may be an isolated storm or
two, and can`t rule out a couple showers/sprinkles on the plains
stretching as far south as Denver before daybreak Tuesday. Overall
chances for any measurable precipitation appear best over the
high country.
On Tuesday, a weak cold front will back across the area by early
morning with a light upslope component developing. The airmass
will become more moist and will destabilize during the course of
the afternoon. CAPES are limited to less than a couple hundred
J/kg in all but the mountains and Palmer Divide, but there should
be enough lift and destabilization to support at least scattered
storm development across the high country by early afternoon, with
these storms also spreading east across the plains through the
mid/late afternoon hours. Have dropped temps a couple degrees for
the expected upslope easterly flow behind the front and more
clouds than sun tomorrow.
.LONG TERM...(Tuesday night through Monday)
Issued at 252 PM MDT Mon Aug 20 2018
For Tuesday night into Wednesday the upper ridge will be over NM and
TX with SW flow over the state. Models show a disturbance moving
through the flow that will bring showers and thunderstorms Tuesday
evening into early Wednesday. With the high pressure to the SW and
the trough extending into northern CA this will help funnel
additional moisture into the Great Basin and Colorado. PW values
will be upwards of 1.3 inches by late Tuesday. There will be enough
forcing to allow showers to continue into the early morning hours on
Wednesday. Best convection, even in the later hours will continue to
be closer to the mountains and foothills with more stable atm over
the East. Showers will still be able to move over in the evening
hours dropping moderate to heavy rain. Conditions will be cloudy
Wednesday with cooler temperatures. At this time highs are only
projected to get into the mid 70s. Another shortwave is projected to
move through late Wednesday with once again having the best
instability closer to the mountains and Palmer divide but still not
impressive. Conditions over the far eastern plains look to be more
stable Wednesday afternoon and evening. Convection will be more over
the higher terrain with some storms possible over the Palmer Divide.
these storms will be capable of heavy rain, gusty winds and small
hail. Temperatures will rebound Thursday into the 80s with 60s in
the mountains. The upper level trough will push in Wyoming and just
brushing portions of Northern CO. Storms will form over the higher
terrain Thursday afternoon with isolated chances over the plains.
For Friday and into the weekend the ridge will push North bringing
clearing skies and stable conditions Friday with highs reaching into
the lower 90s. Saturday, another shortwave will push through with a
surface low over the plains. This will bring scattered storms to the
higher terrain and help to keep storms at bay until later in the day
Saturday over the plains when the atm is able to destabilize. Vort
maxes will continue to push through the SW flow as the upper ridge
lingers over the southern CONUS bringing increased chances of
showers and thunderstorms in the extended.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 757 PM MDT Mon Aug 20 2018
Smoke will continue this evening with visibilities in the 3 to 5
mile range thru midnight at least. It could even linger much of
the night but should see gradual improvement towards sunrise.
Winds were easterly early this evening but should gradually become
more southerly by midnight. Late tonight winds will become light
northwest.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...RPK
SHORT TERM...Barjenbruch
LONG TERM...Bowen
AVIATION...RPK
Area Forecast Discussion
National Weather Service Quad Cities IA IL
659 PM CDT Mon Aug 20 2018
...00z AVIATION UPDATE...
.SYNOPSIS...
Issued at 215 PM CDT Mon Aug 20 2018
As of 200 PM: A seasonably strong upper level low was located along
the Iowa and Missouri border to the south of Des Moines. Bands of
scattered showers and isolated thunderstorms were spiraling around
the low and affecting parts of eastern Iowa and northwestern
Illinois. Instability per the SPC Mesoanalysis has increased to
1000-1500 J/kg of MLCAPE, and with high PWATs near 1.7 inches,
the atmosphere is supportive of localized heavy downpours. Across
the forecast area, temperatures were in the mid 70s on average,
and it was very humid with dewpoints near 70 F.
&&
.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 215 PM CDT Mon Aug 20 2018
This Afternoon through Tonight
Scattered showers and thunderstorms will continue through this
evening. The main impact will be the brief heavy downpours.
Monitoring satellite trends through the day, a brief window of
clearing is most probably over the eastern and northeast sections
of the CWA. Due to moderate low-level shear with 0-1 km values
between 15-20 kts, and low LCLs and LFCs, isolated severe storms
are possible. The Storm Prediction Center has outlined areas
mainly along and north of I-80 for a marginal severe weather
threat. If we were to get a few severe storms, the primary risks
would be strong wind gusts and brief spin-up tornadoes.
Latest HRRR model runs develop the strongest storms over the far
east and in the northeast CWA, where there are more significant
breaks in the cloud cover. We`ll have to continue to monitor
conditions and radar trends through the evening.
Additional rainfall will vary considerably across the forecast area,
but because of the slow storm motion and high PWATs, isolated
locations north of I-80 could pick up another 1-2 inches before
it winds down early tonight.
Tuesday
After residual showers in the morning, dry weather and high
pressure return for the afternoon along with seasonable
temperatures. Uttech
.LONG TERM...(Tuesday Night through Monday)
ISSUED AT 215 PM CDT Mon Aug 20 2018
Wednesday and Thursday
The high pressure system that begins to move in Tuesday will
linger over the Midwest through Thursday. Expect highs in the 70s
to near 80F and lows in the 50s. The cool overnight temperatures
may lead to shallow fog formation in favored low-lying areas, but
did not include fog in the forecast yet. Uttech
Friday On
Models bring a shortwave through Iowa and Illinois late in the
week. The model blend has increased rain chances into the 50-70%
range, which would come in the form of scattered showers and
isolated thunderstorms. This is not a strong system, so the threat
for widespread significant rainfall is low.
Hot and humid conditions are likely by next weekend as the mid-
level flow becomes southwesterly and forecast 850mb temperatures
eclipse 20 C. The model blend has our area in the mid 80s to near
90 F with dewpoints near 70 F -- summer will be in full force
heading into the final week of August. There is also a chance for
thunderstorms Sunday and Sunday night with a potential shortwave
tracking along an instability gradient. Confidence on the details
is low this far out. Uttech
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
ISSUED AT 647 PM CDT Mon Aug 20 2018
Showers and a few storms will continue this evening with greatest
coverage over northeast Iowa into northwest Illinois possibly
impacting CID and DBQ, with more spotty coverage elsewhere.
Overnight expect some spotty showers to linger with passage of
upper level trough. Cooler and moist ground will aid in lower
clouds with MVFR to pockets of IFR CIGs tonight into Tuesday.
Winds will turn gusty from north at 10-20+ kts on Tuesday
advecting in drier air, which should eventually lift any CIGs into
VFR by afternoon.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SYNOPSIS...Uttech
SHORT TERM...Uttech
LONG TERM...Uttech
AVIATION...McClure
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
256 PM PDT Mon Aug 20 2018
.SYNOPSIS...Hot and dry weather Monday afternoon will transition
to cooler conditions by midweek. Otherwise, smoke will persist
across most of the area through the rest of the week.
&&
.DISCUSSION...Tomorrow marks the transition to a cooler, more
seasonable pattern as an upper-level trough moves across the
area. High temperatures are expected to be in the mid 80s to mid 90s
across the interior with 60s occurring along the coast. In
addition, brisk northerly winds will continue to promote
upwelling and boundary layer stability, which will maintain
stratus along the coast.
Current visible satellite imagery shows smoke drifting south from
wildfires in British Columbia, Washington, and Oregon. Recent
HRRR guidance suggests this smoke will enter our area tonight.
Thus, have introduced smoke into the forecast across the northern
waters and most of Del Norte county. This area of smoke is
forecast to continue drifting south across the remainder of the
CWA through Tuesday.
Another upper-level trough is forecast to the western U.S. late
this weekend into early next week. Slightly cooler temperatures
are expected across the interior with this trough, and model
guidance is also hinting at a slight chance of rain.
&&
.AVIATION...An extensive field of marine stratus continued to
cover North Coast areas, adjacent river valleys and hills into
the afternoon. The layer appeared to be slightly deeper today with
bases as low as 200-300 feet. An early afternoon PIREP reported
tops 1600 feet at CEC. A 1:00 PM VIS SAT picture showed plenty of
cloud erosion. However, low CIGS remained persistent even as bases
at ACV had lifted a little bit. Therefore, mid-late afternoon
improvement to VFR conditions still on track. Stratus will most
likely redevelop by mid to late evening with IFR conditions
expected to last through the morning hours on Tuesday at both KCEC
and KACV. Smoke from nearby wild fires have somewhat impacted
KUKI since late morning as UKI`s VIS dipped down into MVFR and may
briefly lower to IFR. It is also possible that smoke obscuration
could lower CIGS down to MVFR. /TA
&&
.MARINE...The brisk northerly winds and steep seas will continue to
gradually subside across the waters as we go through the afternoon
and evening. Light to moderate southerly winds will develop along
the Mendocino coast by Tuesday morning and across the rest of the
waters by Wednesday morning as a broad low pressure center moves
offshore. North winds and steep wind waves will increase Thu through
Fri. /WCI
&&
.FIRE WEATHER...Gusty offshore flow is expected tonight across
interior Del Norte county, with gusts to 30 mph possible across
ridge tops.
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until
9 PM PDT this evening for PZZ470-475.
Small Craft Advisory until 3 PM PDT this afternoon for PZZ455.
&&
$$
Visit us at http://www.weather.gov/eureka
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http://www.facebook.com/NWSEureka
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For forecast zone information
see the forecast zone map online:
http://www.weather.gov/eureka/zonemap.png
Area Forecast Discussion...UPDATED
National Weather Service Grand Forks ND
950 PM CDT Mon Aug 20 2018
.UPDATE...
Issued at 950 PM CDT Mon Aug 20 2018
Weak radar returns over central ND into the Devils Lake basin are
mainly mid level clouds and are not expected to reach the ground
with dry lower levels and a 15 to 20 degree dew point depression.
UPDATE Issued at 713 PM CDT Mon Aug 20 2018
No significant changes needed in the ongoing short term forecast.
A mild evening with fair skies and decreasing winds is ahead.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 303 PM CDT Mon Aug 20 2018
Expect generally fair skies and a light northerly flow to persist
into the evening... with winds diminishing after nightfall. and
overnight periods. Overnight low temperatures should settle into
the upper 40s near the CanAm border and lower 50s near the South
Dakota border.
Meanwhile...upper level winds will be approaching from the west
and bringing a fresh batch of smokey air into and across the area
overnight... with the Canadian and HRRR smoke models keeping most
of that particulate suspended aloft overnight and pushing out of
the area early on Tuesday. We will monitor those conditions along
with the ND Dept. of Health and MN PCA and update Air Quality
bulletins through the day as needed.
Otherwise...the current seasonably cool, dry, and fairly clean
near surface airmass should stay with us into Tuesday... with
light northwest boundary layer winds increasing by midday. High
temperatures are expected to rise into the lower to middle 70s
across the area.
.LONG TERM...(Tuesday night through Monday)
Issued at 303 PM CDT Mon Aug 20 2018
Tuesday night into Wednesday night mid-level ridging will continue
to build into the Northern Plains while northwest flow shifts east
towards northern Minnesota and the Great Lakes Region. Quiet weather
is expected through this period as temperatures gradually warm into
the lower 80s alongside mostly dry conditions.
By Thursday, an upper-level trough and corresponding mid-level
closed circulation will approach from the west bringing out next
chance for precipitation in the area. In general, model guidance
continues to favor a stronger precipitation signal in the southern
Red River Valley while more forecast uncertainty persists for areas
further north. As far as the severe potential, deep layer shear
still appears to be on the weak end, however modest instability may
have the potential to support a few stronger updrafts. The more
pressing focus will be on higher precipitable water values on the
order of 1 to 1.5 inches that may bring concerns for localized heavy
rain.
By Saturday into late Sunday, a secondary frontal passage will bring
additional potential for rain for the area, however model
consistency continues to place the bulk of the precipitation north
of the international border.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 713 PM CDT Mon Aug 20 2018
VFR conditions are expected throughout the TAF period. North winds
will weaken diurnally this evening, turning to the northwest and
increasing again Tuesday morning. Mid level clouds will build in
from western ND this evening, developing ceilings but remaining
VFR. Smoke from Canadian wildfires streaming overhead may cause
impacts through tonight and early Tuesday but is expected to have
little to no impact at the surface for eastern ND and northwest
MN.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...BP
SHORT TERM...Gust
LONG TERM...Lee/Honor
AVIATION...BP
Area Forecast Discussion
National Weather Service Grand Junction CO
549 PM MDT Mon Aug 20 2018
.SHORT TERM...(Tonight through Tuesday night)
Issued at 302 PM MDT Mon Aug 20 2018
As mentioned in the previous discussion, a shift in the pattern
will bring a surge of subtropical moisture to the area.
Specifically, a mid-level low over the Pacific Northwest will
cause the quasi-permanent mid-level high to shift eastward tonight
allowing moisture to move northeastward from the Mexican Plateau.
Some of this moisture arrives later in the day, and when combined
with a disturbance moving along the northern UT&CO/WY border will
generate and sustain showers and embedded thunderstorms through
the night, mainly north of the I-70 corridor. In addition,
experimental HRRR smoke model suggests that smoke over the area
will decrease later tonight.
Moisture levels will continue to rise on Tuesday as the mid-level
high retreats farther east, recentering over the southern Plains
by midday. In response, precipitable water (PW) levels are
expected to rise to near 1.25 inches in the Four Corners region to
0.85 to 1 inch elsewhere. Divergence associated with the jet just
north of the forecast area and possibly a weak disturbance in the
southwesterly flow is projected to generate numerous showers and
thunderstorms over the higher terrain. That said, clouds should
fill in early in the day limiting warming thereby inhibiting storm
strength, and the area could see more quasi-stratiform rain. With
moisture levels near an inch PW, cannot rule out localized heavy
rain, but don`t believe threat rises to the level warranting a
Flash Flood Watch.
Shower/thunderstorm activity is expected to linger Tuesday night
as weak upper level lift works on deep, lingering subtropical
moisture. Temperatures will be relatively mild Tuesday night as
moisture and clouds limit the escape of long wave radiation.
.LONG TERM...(Wednesday through Monday)
Issued at 302 PM MDT Mon Aug 20 2018
Monsoon moisture will continue to feed scattered to numerous
showers and thunderstorms Wednesday. However, the mid-level low
over the Pacific Northwest pushes eastward Wednesday night into
Thursday ushering drier air into the area in its wake Thursday
afternoon. Concurrently, the high over the southern Plains spreads
back to the west disrupting the influx of subtropical moisture
from the Mexican Plateau. As a result, the region will revert back
diurnally driven showers and thunderstorms over the mountains
each afternoon and evening with the southern mountains favored.
Temperatures during the latter part of the week into this weekend
will be close to seasonal norms.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 548 PM MDT Mon Aug 20 2018
Scattered showers are producing gusty winds at the KCNY, KVEL, and
northern Colorado TAF sites this evening, and will continue to
linger over the next few hours. A surge of moisture from the
southwest tomorrow afternoon will lower CIGs and bring the threat
of showers and thunderstorms back to the region. The hazy, smoky
conditions will begin to lift as southwesterly flow takes over.
VFR conditions will last through the period at all TAF sites.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...NL
LONG TERM...NL
AVIATION...MMS/JPF
Area Forecast Discussion
National Weather Service Grand Rapids MI
958 PM EDT Mon Aug 20 2018
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 237 PM EDT Mon Aug 20 2018
Showers and a few thunderstorms will move over the area this evening
as a system approaches the area. Severe weather is not likely,
however some localized gusty winds or a brief isolated weak tornado
is possible south of a line from South Haven to Kalamazoo.
Showers and a few storms will gradually taper off on Tuesday into
Tuesday night. Drier and cooler weather will be found behind the
system on Wednesday.
Temperatures will warm back up again this weekend and could approach
90 degrees. There will be a chance of rain, although most of the
time it will be dry.
&&
.UPDATE...
Issued at 958 PM EDT Mon Aug 20 2018
Although we have remained mostly rain free this evening due to dry
air fending off incoming showers, the latest short term guidance
continues to produce widespread 0.5 to 1 inch of rain later
tonight and Tuesday.
PWATs are progged to rise to around 1.75 inches from south to
north as the system lifts northeast, so look for showers and sct`d
tstms to fill in after midnight once the upper low/trough gets
closer. Will have only low chance pops through midnight, then rising
to 70 pct or more after midnight.
Latest RAP guidance has MLCapes near 1000 J/KG making it up to
the I-94 corridor after midnight, along with 0-3KM shear around
25 kts. That still points to a very low chance of a brief/weak
spin-up, but the loss of any diurnal updraft contribution will
make it difficult. SPC has removed our area from the MRGL risk.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 237 PM EDT Mon Aug 20 2018
Our main concern in the short term is on convection trends through
Tuesday, and any severe weather chances. Most of the area should not
see severe weather, although the chance is not zero across the far
SW corner of the area.
Initial line of showers and storms trying to make their way into the
area this afternoon are having a tough time advancing too far north
and east initially. This is due to the dry air in place below about
20k ft. We do expect the better support and moisture with the front
to bring pcpn in through mid-evening.
As mentioned above, most of the area should not see severe weather
tonight with the warm sector staying just south of the area and
instability being of the elevated variety. The only concern, which
is a small one, is down toward the far SW corner of the CWFA which
will be close to the triple point and warm sector. There seems to be
a small window of opportunity where some left over diurnal sfc based
instability could coincide with some turning of the wind in the
vertical near the front, to possibly allow for a wind gust or a spin
up along the front. This would be possible until mid-evening.
Locally heavy downpours will remain a threat with pwats approaching
2 inches tonight and Tue.
The front will bring the initial wave of rain, and then the
occluding low will bring additional rain overnight tonight and
Tuesday morning. Some elevated instability will keep thunder chances
possible. Showers and storms should become more scattered as the sfc
low moves out, but the upper wave still has yet to move through. The
favored area for additional showers and storms will be across the
east, with a stabilizing flow off of Lake Michigan. A lingering
shower will possible off of Lake Michigan Tue evening as another
short wave moves through.
We should see drier conditions move in for Wed and Wed night. Even
though another short wave moves through from the NW, moisture will
be quite limited by that time.
.LONG TERM...(Thursday through Monday)
Issued at 237 PM EDT Mon Aug 20 2018
Fair weather under sfc ridging and rising heights expected through
the latter half of the week, with some warm advection showers
arriving Friday evening and continuing into Saturday as short wave
trough axis moves through. Showers should be tapering off Sunday in
flat upper ridging.
Temperatures will warm over the weekend as a sharp western CONUS
trough results in heights building across the Great Lakes. A weak
shortwave trough shears out as it tops the ridge on Monday and
brings a low chance of showers.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 757 PM EDT Mon Aug 20 2018
VFR conditions this evening will trend down to predominantly MVFR
overnight as showers and tstms increase in coverage with the
approach of a low pressure system. Ocnl IFR conditions are also
possible overnight where heavier showers occur.
MVFR conditions are expected for much of Tuesday, with some
morning IFR possible as the sfc low tracks through. Improvement
toward VFR should occur late in the day as the low pulls away and
showers end, but winds will be increasing from the north-
northwest.
&&
.MARINE...
Issued at 350 PM EDT Mon Aug 20 2018
Kept continuity with the previous forecast and surrounding offices
with the idea of having a Small Craft Advisory for this event,
although there certainly could be gusts to gale force at times.
The main messaging will be the dangers not only to boaters and
swimmers but those walking on piers. The current high lake levels
mean that waves over 5 feet, which are expected Tuesday afternoon
into Wednesday morning, are capable of washing over piers and
taking any sightseers out there with them. We will continue to
message this via social media.
Waves and winds decrease Wednesday and the expiration time of the
SCA was unchanged.
&&
.HYDROLOGY...
Issued at 237 PM EDT Mon Aug 20 2018
Locally heavy rainfall will be possible with showers and storms
through Tuesday. Precipitable water values will be approaching 2.00
inches through then. We expect that the higher values will not be
widespread. This leads us to believe that widespread flooding will
not be a problem. Localized areas could see some issues if some
training of showers/storms occurs. The limited coverage of recent
rainfall, and ongoing drought conditions will help to mitigate
flooding potential a bit. Once we get to Tuesday afternoon, we
should at least a brief break before the next batch of rain comes in
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from Tuesday afternoon through Wednesday
evening for MIZ056-064-071.
Beach Hazards Statement from Tuesday morning through Wednesday
afternoon for MIZ037-043-050.
LM...Small Craft Advisory from 11 AM Tuesday to 2 PM EDT Wednesday
for LMZ847>849.
Small Craft Advisory from 2 PM Tuesday to 8 PM EDT Wednesday for
LMZ844>846.
&&
$$
UPDATE...Meade
SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...Ostuno
AVIATION...Meade
HYDROLOGY...NJJ
MARINE...Ostuno
Area Forecast Discussion
National Weather Service Huntsville AL
754 PM CDT Mon Aug 20 2018
.NEAR TERM...(Tonight)
Issued at 754 PM CDT Mon Aug 20 2018
The airmass over north AL has greatly stabilized after earlier
thunderstorms and rain-cooled air over central AL has begun to advect
northward. This can be seen in the CAPE/theta-e fields. A larger
scale outflow boundary from the central AL convection was noted on
KGWX moving northwest into Lawrence and southeast Franklin County.
Obviously, supercell convection over northern MS is being monitored
closely feeding off very high ML-CAPE of 2000-3000 j/kg and effective
deep layer shear of 30-35kt. It will be interesting to see how the
outflow boundary interacts positively or negatively on the strength
of the supercells in northeast MS. This activity will likely reach
far northwest AL between 02-04Z in some form, and has been
consistently forecast by the HRRR in doing so. However, the HRRR
trends are also consistently weakening the convection rapidly between
04-08Z, likely not reaching most of our southeast forecast area,
roughly southeast of BGF-HSV- Bankhead NF. The severity of the
thunderstorms may give our western 3 counties a threat of damaging
wind. Have adjusted overnight PoP to lower values in our southeast
counties based on these trends.
.SHORT TERM...(Tuesday through Wednesday night)
Issued at 334 PM CDT Mon Aug 20 2018
Short term guidance suggests that the mid-level trough axis will
cross the TN Valley region tomorrow morning, with flow aloft veering
to north-northwest and increasing throughout the day. At the surface,
a Pacific cold front should spread rapidly eastward through all but
perhaps the southeastern counties by 18Z, with gusty west-
southwesterly low-level flow developing in its wake. Any lingering
deeper convection is expected to end rather quickly around or shortly
after sunrise over northeast AL, although isolated light showers
will be possible region-wide throughout the morning prior to the
arrival of the Pacific front. Strengthening subsidence aloft will
promote rapid drying of the column in the wake of the front, but
lower clouds could potentially be slow to erode and for this reason
we have forecasted max temps close to values from today.
A northwest flow aloft will persist across the region for the
remainder of the short term period, as latest NWP guidance indicates
that the region will remain along the northeastern periphery of a
strong subtropical ridge centered across eastern NM/western TX.
Although a few weak mid-level disturbances will travel southeastward
across the region in this regime, lift will be too weak to support
development of precipitation based on the anticipated vertical
moisture profile. A modified Canadian surface ridge will migrate
eastward from the central High Plains into the OH Valley, with low-
level flow gradually veering from northwest to northeast by Wednesday
night. Although dewpoints will drop considerably, lows Thursday
morning may not reach their full potential due to an increase in high
clouds and elevated surface flow.
.LONG TERM...(Thursday through Sunday)
Issued at 334 PM CDT Mon Aug 20 2018
The center of the subtropical ridge is expected to build eastward
across TX and into the lower MS Valley from Thursday through Friday,
with northwest flow aloft diminishing with time. In the lower-levels
east-southeasterly winds will begin to increase Friday morning as a
strengthening surface ridge builds southward in the lee of the
southern Appalachians. However, before this occurs, we anticipate
strong radiational cooling on Thursday night, with lows predicted to
range from the upper 50s in the northeast to the lower 60s elsewhere.
Limited northward return of boundary layer moisture may promote a
few showers and thunderstorms in the southeast on Friday afternoon,
with a slight to low chance of afternoon convection expected on both
Saturday and Sunday. However, as a result of strengthening subsidence
beneath the building anticyclone aloft, we expect the coverage to be
rather limited. Both max/min temperatures should warm steadily over
the course of the weekend, with highs ranging from the upper 80s in
the east to the lower 90s elsewhere. Unfortunately, as dewpoints
slowly rise back into the lower 70s, Heat Index values will once
again be in the 95-100 degree range for much of the region Saturday
and Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 625 PM CDT Mon Aug 20 2018
Currently VFR conditions are prevailing across most of north
AL/southern middle TN. Expect this to continue until showers and
thunderstorms over N MS/W TN move east over next several hours. These
storms could be strong to marginally severe mainly over NW AL (close
to KMSL) with wind gusts up to 50 kts possible around the 03Z-05Z
time frame. Have included a TEMPO group at KMSL for this potential
but have not included the wind gusts yet due to coverage uncertainty.
These storms should weaken as they approach north central AL/Southern
middle TN. Then, anticipate IFR to MFR cigs to rapidly follow the
storms until 15Z with wind gusts up to 20kts possible with prevailing
westerly winds.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...17
SHORT TERM...70/DD
LONG TERM...70/DD
AVIATION...SL.77
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Wilmington NC
950 PM EDT Mon Aug 20 2018
.SYNOPSIS...
Bermuda High will continue spreading warm and moist air over the
region into Wednesday. Shower and thunderstorm chances will
increase Tuesday and Wednesday, prior to a cold front crossing
the region Wednesday night. Canadian high pressure will build
in behind the front, bringing a drier and slightly cooler
airmass for the end of the week and start of next week.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 900 PM Monday...Mid to upper trough extending down from
the Upper Great Lakes down almost the full length of the
Mississippi River will traverse slowly eastward overnight. At
the same time, upper level ridging still holding on right up
along the Southeast coast. This has helped to limit convection
so far today over local area, with best convective activity in
convergence along and ahead of front draped near the VA/NC
border and near trough inland. Basically, aside from some fading
sea breeze convection, area was only left with an isolated
storm or two with more widespread activity mainly north of
forecast area. Some debris clouds from convection just to our
north will continue to stream across the area overnight.
Models continue to show some shortwave energy rotating around
longer wave trough, so can not completely rule out an isolated
shwr/tstms overnight, but with loss of heating will leave
coverage isolated at best. Continued hot and humid air mass with
temps once again in the mid 70s for overnight lows most places.
Previous discussion: Despite deep layer saturation seen in
today`s 12Z RAOBs convection continues to be hard to come by.
Granted there is little to no deep layer ascent but the fact
that even surface forcing is not generating meaningful rainfall
indicates that the the shortwave ridge currently crossing the
area and the weak lapse rates in place are dominating. There is
however some decent agreement with major guidance that this
changes overnight at least for the coast as the WRF in
particular shows a strong convective signal. Area- wide low
chance POPs warranted tomorrow with some higher values over far
interior zones where some southwesterly flow may start to
impinge upon the area.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 3 PM Monday...A pair of shortwaves will move through the
Great Lakes and across New England this week. A thin axis of
vorticity trailing well south of the first shortwave will move
across the eastern Carolinas Tuesday night. Enough moisture and
instability should be present that scattered showers and
thunderstorms will persist along and ahead of the vort lobe.
Confidence that we`ll see storms is increased seeing that that
we`ll have the right-entrance region of a south-to-north 250 mb
jet max overhead Tuesday night. 0-6 km shear around 20 kt should
support weakly organized multicells, with overall cell motion
toward the northeast at 25 mph.
Behind the departing vorticity aloft, much drier mid-level air will
overspread the eastern Carolinas Wednesday. While lapse rates will
continue to be steep enough to support convection, all that dry air
and unfavorable jet structure aloft has led me to trim PoPs back to
20-30 percent inland and only 40 percent in the seabreeze-enhanced
area near the coast. It`s worth noting the GFS and ECMWF are
considerably drier than the NAM with moisture through the 800-600 mb
layer Wednesday, but all models show 0-6 km bulk shear values
remaining good for this time of year. If we do get storms, the dry
air aloft will get entrained into downdrafts enhancing the potential
of strong, gusty winds. SPC has a small "marginal" risk area for the
eastern Carolinas for this potential.
As the second shortwave moves across New England Wednesday night, a
cold front extending southward through the Mid-Atlantic will move
into, and likely through, the eastern Carolinas late. Yes, this
appears to be a true frontal passage with a wind shift and advection
of modestly drier air beginning before sunrise Thursday.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 3 PM Monday...Cold front will be off the coast as the period
begins. High pressure building in from the northwest is quickly
moved east by progressive flow aloft. Lingering moisture along the
coast Thu might support some isolated diurnal convection Thu
afternoon/evening. Mid-level pattern transitions to flattened 5h
ridge for the end of the week and start of next week. Weak coastal
trough develops Fri night into Sat as the surface high drifts off
the New England coast. The trough tries to move onshore but the
combination of building mid-level ridge coupled with consolidation
of the surface high over western NC and eastern TN keeps the trough
at bay until it washes out, later in the weekend. Remnants of the
trough combined with the sea breeze could lead to an increase in
diurnal convection Sat through Mon. Following the passage of the
cold front temperatures will run below climo through the weekend,
rising to around climo as the period ends.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 00Z...Convection hanging in there, mainly over North Carolina
and a couple of counties in South Carolina. The HRRR has convection
continuing through around 04-05Z. A secondary batch of showers is
possible at the coastal terminals toward morning. Light southwest
flow overnight. Tuesday, time height showers a reasonable amount of
moisture and we should see convection breaking out once again around
midday. Winds will become gusty by mid to late morning.
Extended Outlook...TSTMS becoming more numerous, possibly strong to
severe from Tuesday evening through Wednesday morning, as storm
motion increases. Frontal passage occurs early Thursday with a
drying trend and VFR conditions Thursday and Friday, and low level
winds NNE-NE.
&&
.MARINE...
NEAR TERM /THROUGH TUESDAY/...
As of 900 PM Monday...Southwesterly flow to continue through
the period. The sea breeze has been making the coastal winds
stronger than those further offshore according to buoy data. The
gradient will tighten slightly heading into tomorrow but mostly
over land. Wind and seas over the water will more or less stay
steady state/unchanged.
SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 3 PM Monday...The Bermuda high will retreat farther off
the coast this week. Low pressure moving through New England
will drag a cold front southward and actually through the
coastal Carolinas late Wednesday night. It appears this will be
a true frontal passage with an actual wind shift expected before
daybreak Thursday.
Before the front arrives, breezy southwest winds 15 to occasionally
20 knots are expected, maintaining seas of 3-4 feet. The best chance
of thunderstorms appears to be Tuesday night as an upper level
disturbance moves across the area, then perhaps again Wednesday
afternoon is storms can form within a rather dry airmass aloft.
LONG TERM /THURSDAY THROUGH SATURDAY/...
As of 3 PM Monday...High pressure building in behind the cold
front will maintain northerly flow over the waters Thu.
Northeast surge arrives Thu night with winds increasing to a
solid 15 kt. Northeast flow remains on the high end of the 10 to
15 range Fri as gradient remains pinched. Gradient starts to
relax Fri night as the center of the high shifts northeast and
flow becomes more onshore for Sat. Seas 2 to 3 ft at the start
of the period build to a solid 3 ft Thu night and Fri before
dropping closer to 2 ft late Fri night and Sat as wind speeds
decrease.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
NEAR TERM...MBB/RGZ
SHORT TERM...TRA
LONG TERM...III
AVIATION...DL
Area Forecast Discussion
National Weather Service Lincoln IL
901 PM CDT Mon Aug 20 2018
.UPDATE...
Issued at 901 PM CDT Mon Aug 20 2018
For the most part, the current forecast looks fine. Severe weather
threat has diminished considerably across the CWA and all that is
left is isolated to scattered showers and storms. Will be
adjusting pops to account for current trend seen on the radar
across the area. Winds will remain light and variable as well
given the proximity of the sfc low. Update should be out shortly.
&&
.SHORT TERM...(This evening through Tuesday)
ISSUED AT 300 PM CDT Mon Aug 20 2018
19z/2pm surface analysis shows warm front north of the I-74
corridor, with scattered thunderstorms noted in the vicinity of
the boundary across the far northern KILX CWA from near Bradford
to Lexington. Front and its associated convection will lift into
northern Illinois over the next 1-2 hours...leaving behind a
warm/humid airmass with only isolated storms across central
Illinois through late afternoon. Meanwhile, thunderstorms are
increasing in coverage and intensity upstream across southeast
Missouri into southwest Illinois. This activity is firing ahead of
an advancing cold front within a moderately unstable/sheared
airmass characterized by SBCAPES of 2500-3500J/kg and 0-6km bulk
shear of 30kt. Based on radar trends and consistent HRRR output,
it appears the storms will spread northeastward across the E/SE
CWA mainly along/east of a Taylorville to Champaign line between
22z/5pm and 02z/9pm. Strong to potentially severe storms with
damaging wind gusts will be possible. Have therefore carried
likely PoPs across this area late this afternoon through mid-
evening. Further west, areal coverage of convection will be
considerably less, so have only gone with chance PoPs across the
central/western CWA. Main push of convection will exit into
Indiana by late evening, followed by a few lingering showers
through the overnight hours. Much cooler weather will be on tap
for Tuesday: however, with upper trough axis just east of the area
over Indiana and weakly cyclonic flow persisting, cannot rule out
a few showers. High temperatures will be in the upper 70s.
.LONG TERM...(Tuesday night through Monday)
ISSUED AT 300 PM CDT Mon Aug 20 2018
High pressure will bring cooler/drier weather into central
Illinois for Wednesday and Thursday with highs in the middle to
upper 70s and lows in the middle to upper 50s both days. As the
high departs, a short-wave trough noted on latest water vapor
imagery over Idaho will begin to approach from the northwest on
Friday. 12z Aug 20 GFS/ECMWF are in excellent agreement with one
another...with both models suggesting rain chances arriving
along/west of the Illinois River late Thursday night...then
spreading across the remainder of the area Friday/Friday night.
Once the short-wave passes, upper heights will rise in earnest
over the weekend as a pronounced upper ridge builds over the mid-
Mississippi River Valley. As a result, temperatures will climb
into the upper 80s and lower 90s Saturday through Monday. Models
are hinting at potential MCS development over Minnesota/northern
Iowa Sunday night which could possibly spill into north-central
Illinois Monday morning. It is still too early to pin down the
details with this scenario, but will feature low chance PoPs
across the north on Monday to handle this. Main story this weekend
through much of next week will be the heat...as a prolonged period
of summerlike weather will develop.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 650 PM CDT Mon Aug 20 2018
VFR conditions are expected to start the evening, except at CMI
where a storm will move through the area over the next hour. Then
broken cigs at all sites are expected this evening. Widely
scattered showers are around but will be keeping out of the sites
until it appears the precip will get to the sites...and then will
amend. Once this area of scattered precip moves out of the area
tonight, lower clouds in the MVFR to IFR category will develop
over the area overnight and into the morning hours. With cyclonic
flow still over the sites tomorrow and cooler temps with lots of
low level moisture, expecting MVFR cigs during the morning hours
at all sites, along with VCSH. Winds will be variable through the
period.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Auten
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Auten
Area Forecast Discussion
National Weather Service Indianapolis IN
1146 PM EDT Mon Aug 20 2018
.UPDATE...
The AVIATION Section has been updated below.
&&
.SYNOPSIS...
Issued at 237 PM EDT Mon Aug 20 2018
Low pressure over Iowa and Missouri is expected to push to
Michigan and Indiana by Tuesday morning. This will bring showers
and isolated thunderstorms to Indiana tonight. A cold front
associated with the low is expected to push across the state on
Tuesday. This will bring a chance for another round of
precipitation on Tuesday before dry air begins to arrive on late
Tuesday afternoon.
Cooler and dry high pressure will arrive across Central Indiana
Wednesday and provide dry weather for the rest of the work week.
Showers look to return to the area on Friday night as another
frontal system pushes into the Ohio valley. Showers chances look
to linger across Indiana through the weekend.
&&
.NEAR TERM /Tonight/...
Issued at 851 PM EDT Mon Aug 20 2018
Mid level vorticity lobe currently arcing from eastern Illinois into
far western Kentucky is expected to move into the western border
zones over the next hour or so. Convection may increase in coverage
over the next few hours as this feature moves into the area, and
interacts with some enhanced flow at 850mb.
Appears the highest threat for precipitation for the rest of the
night will be between about 210200Z-210900Z, coinciding with the
passage of the upper air feature. Deep layer shear remains
marginally favorable for strong to severe storms for the balance of
the night.
Previous discussion follows.
Surface analysis early this afternoon shows deep low pressure in
place across southern Iowa. A warm front extended eastward from the
low across Illinois to Central Indiana. Radar shows a wave of
showers ahead of the warm front. Dew point temperatures across the
area remained very moist...in the lower 70s. Water vapor showed an
upper low was found across MO/IA. A plume of tropical moisture was
streaming across the Deep south...through the Ohio valley and into
the low.
The GFS and NAM suggest this low pressure system will trek
northeast toward lower Michigan tonight...keeping cyclonic flow
across Central Indiana tonight. Forecast soundings again show good
lift arriving across the forecast area tonight with good low and
mid level moisture. HRRR suggests a wave of precipitation pushing
across Indiana after 02Z. Forecast soundings suggest deep
saturation overnight as this deep low passes to the north.
Thus will trend nearly toward categorical pops
tonight...particularly across the northwest where best forcing and
dynamics will be best. Given the expected clouds and rain will
trend low at or above the forecast builder blends.
&&
.SHORT TERM /Tuesday through Thursday/...
Issued at 237 PM EDT Mon Aug 20 2018
An Active weather morning will be expected on tuesday with a slow
transition toward quiet and drier weather on Tuesday afternoon
and Tuesday Night. Models suggest the upper trough axis and an
associated cold front will push across the area early in the
morning. Models show best forcing exiting the area prior to 12Z
and moisture slowly decreasing through the day as the flow becomes
more northwesterly. Forecast soundings show drying within the
column as the afternoon progresses. Thus will start with some
morning pops across the forecast area and trend lower as the day
progresses...eventually dry by late in the day. Given the
expected change in air mass will stick close to the forecast
builder highs.
The GFS shows strong mid level ridging over the upper midwest
diving southward toward Indiana on Tuesday Night. This strong
ridge axis and large high pressure system is expected slowly
advect eastward into the Ohio Valley through Thursday. Forecast
soundings. Forecast soundings on Tuesday night through Thursday
show a very dry column...with a good mid level inversion. Thus
only partly cloudy skies will be expected. Will stick close to the
forecast builder blends on temperatures.
&&
.LONG TERM /Thursday night through Monday/...
Issued at 210 PM EDT Mon Aug 20 2018
Models in fair agreement and will be followed. A couple shots at rain
and storms this period along with a return to quite humid and
much warmer weather by the weekend.
Surface high pressure that drops humidity across the region
midweek moves east returning southerly flow Friday onward. Current
upper trough in the Pacific NW will open up and track into our
region Friday/Saturday bringing a chance for showers and storms
late Friday, exiting late Saturday. A continuation of southerly
flow will return dewpoints to the 70s for the weekend and heat
indices well into the 90s. Diurnal heating in the renewed
tropical airmass may trigger a shower or storm during peak heating
Sunday into Monday.
Blended temperature forecasts looked reasonable and were followed
with a return from normal temperatures Friday to well above normal
for the weekend and Monday.
&&
.AVIATION /Discussion for the 210600Z TAFS/...
Issued at 1145 PM EDT Mon Aug 20 2018
Mid level vorticity lobe currently moving through the area,
combined with 25 kts of enhanced flow at 850mb, should allow for
scattered convection in the vicinity of the terminals for the
balance of the night. Convective threat should taper off after
about 210900Z as the upper feature lifts off to the northeast.
Brief IFR visibility restrictions and gusty shifting winds in and
near the heavier cells. CB bases around 020.
Otherwise, expecting low cloud development 008-012 towards sunrise
in the wake of the mid level feature as the air mass stabilizes.
These ceilings will probably linger into the mid to late morning
hours.
Surface winds 170-200 degrees at 5-9 kts overnight will gradually
veer to 24-260 degrees at 9-13 kts by midday Tuesday.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...Puma
NEAR TERM...Puma/JAS
SHORT TERM...Puma
LONG TERM....Tucek
AVIATION...JAS
Area Forecast Discussion
National Weather Service Midland/Odessa TX
552 PM CDT Mon Aug 20 2018
.DISCUSSION...
Aviation concerns are below.
&&
.AVIATION...
Aside from thunderstorms affecting KFST through 21/01Z, VFR will
prevail at all area terminals tonight and Tuesday. Winds will
veer around to the southeast or south tonight/Tuesday morning, but
generally be around 10kt.
&&
.PREV DISCUSSION... /issued 206 PM CDT Mon Aug 20 2018/
The aforementioned cold front has pushed into the Trans Pecos with
less unstable conditions noted across the PB/SE NM. Best SB
instability is focused across the Trans Pecos where insolation has
been good most all day and in Lower Trans Pecos where dewpoints are
high - U60s! Visible imagery shows an MCV tracking s from the far
wrn PB. HRRR initiates scattered storms across the Trans Pecos
which could persist until early evening, heavy rain and downburst
winds are the main concern. Visible imagery also shows TCU
bubbling from the srn PB into the Trans Pecos. We made some
changes to PoPs for remainder of afternoon and early evening to
shift higher PoPs farther s. After this evening the chance for
rain markedly decreases as the ridge to the w builds e resulting
in a gradual but noticeable hotter trend. By Fri PM 7h
temperatures across most all of the CWFA are >12C and near 30C at
85h, thus triple digit highs are likely ahead. The center of the
anticyclone will be e over the weekend and high temps may back off
a couple of degrees, but temperatures still well above normal.
Depending on how far e and how long the ridge stays e will
determine whether or not SHRA/TSRA will creep into the wrn CWFA
next week.
&&
.PRELIMINARY POINT TEMPS/POPS...
Big Spring 74 97 75 98 / 0 10 0 0
Carlsbad 71 96 71 96 / 10 10 0 0
Dryden 74 98 74 98 / 20 10 0 0
Fort Stockton 71 95 71 96 / 20 10 0 0
Guadalupe Pass 67 90 67 90 / 10 10 0 0
Hobbs 68 94 69 94 / 0 10 0 0
Marfa 61 90 62 89 / 20 10 0 0
Midland Intl Airport 74 97 74 98 / 10 10 0 0
Odessa 74 97 74 98 / 10 10 0 0
Wink 74 98 73 99 / 10 10 0 0
&&
.MAF WATCHES/WARNINGS/ADVISORIES...
NM...None.
TX...None.
&&
$$
99/99/
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1035 PM EDT Mon Aug 20 2018
.SYNOPSIS...
A weak cold front near the northern sections will lift north
tonight and Tuesday. Another cold front will move through the
area late Wednesday night and Thursday, then stall off the
coast into next weekend.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
As of 1030 PM Monday...Only minor adjustments to overnight
forecast with highest POPs over NW sections next few hours as
current activity moves NE with some mid-level warm front action.
Latest HRRR and NAM12 support scattered activity possible across
most of area 2 AM-8AM thus 40-50% POPs all areas that period.
Minor adjustments for convective debris cloud cover into
overnight. Temps on track.
/Previous discussion/
As of 240 PM Mon...Convection beginning to increase over the
region and expect good coverage into the evening given moist
unstable air over the region. Locally gusty winds and very
heavy rain a good bet with stronger storms. Instab will diminish
a bit overnight but mdls show decent coverage of shra/tsra
cont...kept good chc in most areas with again threat for
locally very heavy rain...poor drainage flooding. Lows in the
70s.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
As of 240 PM Mon...Sct to numerous shra and storms expected
again with little change in airmass. Mid lvl flow is a bit
stronger Tue as short wave crosses well to the NW. If get enough
heating and instab could have a cpl severe storms and as usual
the threat for heavy rain in spots. Cont with likely pops inland
to chc closer to coast in the aftn with highs mostly 85 to 90.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
As of 3 AM Mon...Unsettled for the first part of the week, then
a cold front will push through the area Wednesday night and
Thursday with drier air moving into the area and precip chances
becoming more isolated to widely scattered.
Tuesday Night and Wednesday...Surface low will continue to
strengthen and move through the Great Lakes as attendant cold
front approaches from the west. PWATs climb to around 2.3
inches Tuesday evening, with 0-6 km shear increasing to 20-30
kt. Isolated strong to severe storms with damaging wind gusts
and locally heavy rainfall will be possible in the evening.
Scattered showers and storms will continue Wed, though heavy
rain threat expected to wane as airmass becomes much drier
aloft. Highs in the mid to upper 80s, with lows in the 70s.
Wednesday night through Sunday...A cold front will push through
the area Wednesday night and Thursday, then likely stall off the
coast into the weekend as strong high pressure builds in from
the north. A much drier and more pleasant airmass will move into
the area. Expect precip chances to diminish as well, though will
continue sc/low chance pops along the coast near axis of better
moisture. Expect temps below normal, with highs in the low to
mid 80s and overnight lows in the 60s to low 70s. Some guidance
has lows dropping into the upper 50s to low 60s inland Fri and
Sat mornings. Upper ridge will strengthen over the area late
weekend into early next week as surface high remains centered
just to the west. Temps will gradually warm with precip chances
returning to near climo.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Short Term /through 00Z Wed/...
As of 800 PM Monday...Cluster of tstms with sub-VFR conditions
is in between TAF sites but will likely spread NE and affect
mainly KISO and KPGV next 1-3 hours. Scattered convective threat
will continue all sites through the night but will handle mainly
with VCSH. Otherwise, VFR expected into overnight hours with
some sub-VFR CIGs/VSBYs possible around sunrise. Mainly VFR
again during the day Tuesday with scattered shower threat in
morning and tstm threat in afternoon.
Long Term /Tuesday night through Friday/...
As of 3 AM Mon...Scattered to numerous showers and storms will
produce sub-VFR conditions at times Tuesday night and
Wednesday, best chances during the afternoon and evening hours.
A cold front will push through the area Wednesday night and
Thursday, with a drier airmass moving in behind it for late
week.
&&
.MARINE...
Short Term /through Tue/...
As of 1030 PM Monday...no changes with update.
/Previous discussion/
As of 240 PM Mon...Weak front near nrn tier will lift N tonight
with pred SW flow 5 to 15 kt N and 10 to 20 kt S. Gradient
begins to tighten Tue ahead of approaching cold front and SSW
winds will increase to 15 to 20 kts with gusts approaching 25
kts late. Seas will be in the 2 to 4 foot range tonight
building to 3 to 5 feet Tue.
Long Term /Tuesday night through Friday/...
As of 3 AM Mon...SCA conditions likely late Tue night into Wed.
Gradient conts to tighten Tue night and Wed, with SW winds
increasing to 15-25 kt and seas building to 3-6 ft. SCA
conditions likely to develop across the waters and Pamlico Sound
late Tue night and Wed. A cold front is likely to push through
the waters Thursday then stall off the coast into the weekend.
Winds will shift becoming NE/E 5-15 kt Thu, and then move
easterly 10-15 kt Fri with seas 2-4 ft.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...RF
NEAR TERM...RF/JBM
SHORT TERM...RF
LONG TERM...CQD
AVIATION...RF/JBM/CQD
MARINE...RF/JBM/CQD
Area Forecast Discussion...CORRECTED FORMATTING
National Weather Service Twin Cities/Chanhassen MN
722 PM CDT Mon Aug 20 2018
.SHORT TERM...(This evening through Tuesday)
Issued at 248 PM CDT Mon Aug 20 2018
Main concern is overall convective trends overnight and possible
stratus/fog development after midnight.
Latest SPC mesoanalysis showing an area of MLCAPES around 1000J/kg
moving across a small portion of east central MN. This continues to
wrap southeast in overall forecast through about 00z or so. HRRR
trends have continued to show widely scattered development in this
area through, although coverage is decreasing. Otherwise,
progression of the upper low and its attendant rain shield has been
slow to lift into southern MN and appears to be as far north as it
will be for the event. Will have to trim PoPs over a portion of
southern MN. Overall, it appears the precipitation threat will end
by 03z. Following that, clouds will linger and models continue to
trend stratus/fog development over the eastern portion of the cwa
overnight. SREF probabilities for low clouds where greater that 90%
again with lower probabilities for lower visibility. Will mention
patch fog for now. An area of smoke is rotating s-sw over the area
and with mixing this afternoon, some of the smoke has reached the
ground. THis may continue into TUesday as well. The MPCA issued an
Air Quality Alert earlier and continued through 9pm Tuesday over
much of central/southern MN.
For Tuesday, the latest models have trended another weak short wave
dropping in behind this latest upper low. This will bring in some
clouds and perhaps a small threat of isolated showers to central MN
Tuesday afternoon. At the moment we will go dry with deeper moisture
lacking and rather weak instability.
&&
.LONG TERM...(Tuesday night through Monday)
Issued at 248 PM CDT Mon Aug 20 2018
Westerly flow aloft develops for the remainder of the week and
results in dry and mild conditions through Thursday as surface
high pressure builds across the central CONUS. High temperatures
will mostly range from 75-80 degrees on Wednesday and Thursday.
Late Thursday and Friday both GFS and ECMWF models continue to
advertise the progression of a healthy mid-level shortwave across
the Upper Midwest. Temporal progs have trended slightly slower
with this feature, but still look to impact the area with showers
and thunderstorms in the Thursday night through Friday time frame.
Have retained likely (60-70 percent) POPS.
Saturday currently looks to be our break day between systems,
although we look to see warmth and humidity building back slightly
as high temps moderate into the mid 80s and dewpoints creep into
the 70s ahead of a High Plains trough. Some weak mid-level energy
and low level warm air advection are progged for Sunday into
Monday, so low precipitation chances have been included then as
well. Model solutions are still highly variable over the weekend
with regard to where synoptic features setup, so confidence is
still low at this point.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 722 PM CDT Mon Aug 20 2018
Scattered showers continue across eastern MN and WI early this
evening, but they should diminish in the next few hours. VFR
conditions expected for most of the evening, but smoke and light
fog may begin reducing visibilities to MVFR levels late this
evening. MVFR/IFR stratus will develop across areas near and
east of RWF and STC overnight, and lift by Tuesday afternoon.
KMSP...Light showers persist for the next hour or two, then dry
for the rest of the period. MVFR conditions are expected to arrive
sometime around 09Z overnight.
/OUTLOOK FOR KMSP/
Thu...VFR with TSRA possible overnight. Wind SW 10-15 kts.
Fri...Chc MVFR/TSRA. Wind SE at 10G20 kts.
Sat...Chc MVFR early. Wind S 5 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...DWE
LONG TERM...LS
AVIATION...BORGHOFF
Area Forecast Discussion
National Weather Service Phoenix AZ
218 PM MST Mon Aug 20 2018
.UPDATE...Updated Fire Weather Discussion.
&&
.SYNOPSIS...
Substantial moisture returns to the region this evening bringing
a chance of showers and thunderstorms to all areas of south-central
AZ tonight through Tuesday. The upper level flow pattern then
shifts to the southwest on Wednesday bringing some drying and
lower grade monsoon conditions Thursday and Friday. Storm chances
will remain across portions of south-central Arizona during this
period but will mostly be focused across the higher terrain north
and east of Phoenix.
&&
.DISCUSSION...
A look at the upper level pattern this afternoon reveals high
pressure is currently moving over eastern Arizona and into New
Mexico. This is acting to shift our steering flow to the southeast
which is already allowing moisture from Mexico to stream into our
area. The 12Z sounding from Phoenix today shows PWs are already
up 0.5 inches from just 12 hours ago while the upper level 700 mb
flow has shifted to the southeast.
There is excellent agreement between mesoscale models that deep
convection will begin over southern AZ/northern Sonora this
afternoon, aided by the increase in moisture, and then subsequently
send an outflow boundary to the north towards Phoenix around 8 pm
this evening. New convection could fire off on this outflow as it
moves northwest but should also weaken as it does so. The
reasoning here lies within the increasing CIN to the north with
about 100 J/kg forecast around Phoenix this evening. Several runs
from the HRRR model did show convection making it into Phoenix
this evening, however, this model remains an outlier. So while
storms are unlikely for the metro, they are certainly not out of
the question.
A secondary wave of convection will quickly follow tonight
associated with a shortwave rotating up through Mexico. Nearly all
models show some activity overnight in south-central AZ, however,
there are differences in timing and location. Some solutions
point to weak overnight convection beginning as early as midnight
to as late as 5-8 AM Tuesday morning. At this point, convection
will most likely be centered over Maricopa County Tuesday morning
but it is not out of the question for this area to shift a bit
west or east as it rotates through. One thing to note is that
moisture will be high, between 1.75 and 2.0 inches, so whatever
does develop will be very efficient at producing heavy rain.
Although, the GFS shows the steering flow around 10 to 20 kts so
flash flooding should remain isolated and not widespread.
Depending on how Tuesday morning plays out will largely influence
what will happen in the afternoon. Several models show considerable
cloudiness over our area from the morning through much of the
afternoon. This will undoubtedly put a damper on afternoon
convection with storms being confined to the higher elevations
and locations that do clear out early enough.
The aforementioned upper level high will continue shifting
eastward on Wednesday with our flow aloft turning solely out of
the southwest. This will bring drier air into the region, but we
should still have sufficient moisture for afternoon and evening
storms mostly across the high terrain north and east of Phoenix.
Similar conditions are seen for Thursday and Friday. Temperatures
will remain fairly steady through the rest of the week as 500mb
heights lower from 594dm on Wednesday to 588dm on Saturday. These
lower heights are due to a developing Pacific low well off the
California coast. Though it is around a week away, both the GFS
and European show a more significant Pacific trough digging
southeastward into the Pacific Northwest early next week. This
will definitely be something to watch for the middle part of next
week.
&&
.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:
As we transition back into a little more active storm regime,
expect a chance of showers and storms in the region beginning
tonight around 04Z and continuing on and off through Tuesday
afternoon. Expect periodic episodes of gusty southwesterly to
southeasterly outflow winds beginning tonight around 04Z with gusts
of 20-28kt. Nighttime visibilities may also be temporarily reduced
to 3-5sm in areas of blowing dust from the south, although not to
the extent of including them in the TAFs. Expect BKN-OVC decks from
8-10kft on Tuesday morning near 15Z with thunderstorms in the
vicinity. For this afternoon no impacts are expected with breezy
westerly winds at 6-12kt gusting to 15-18kt. Otherwise skies will be
partly cloudy FEW-SCT decks at 10-16kft and BKN high clouds near 20-
25kft.
Southeast California/Southwest Arizona including KIPL and KBLH:
Expect moderate to very breezy southerly winds at KBLH near 10-15kt
with gusts to 22-27kt through most of the period. The winds at KIPL
will favor the southeast to south near 7-12kt. Skies will be mostly
clear with FEW-SCT high clouds near 20kft.
Aviation Discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Thursday through Monday :
As Monsoon conditions continue expect the best chances for
thunderstorms to be focused over the high terrain areas north and
east of Phoenix along with continued slight chances of storms
over the lower deserts. Max temperatures are expected a little
below normal through the period. Min RH values across SE CA will
stay in the mid to upper teens and above or well above 20 percent
elsewhere. Overnight recover will be fair across SE CA and good to
excellent elsewhere. Expect typically breezy upslope winds each
afternoon.
$$
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Wilson/Kuhlman
AVIATION...Sawtelle
FIRE WEATHER...Sawtelle
Area Forecast Discussion
National Weather Service Pueblo CO
332 PM MDT Mon Aug 20 2018
.SHORT TERM...(This evening through Tuesday)
Issued at 332 PM MDT Mon Aug 20 2018
...Smoke then Storms...
Main weather feature today has been the smoke. It`s really hard to
tell exactly where all the smoke is coming from because there are so
many fires over the western U.S. and Canada that have all merged
into one massive smoke layer over the western U.S. In any event,
smoke modeling shows the smoke holding on through this evening and
then moving off to the east, in large part, as monsoonal moisture
and disturbances begin to move in from the west. There may still be
some smoke around late tonight and Tuesday but it should be a lot
less.
On Tuesday, we turn our attention to an influx of monsoonal moisture
and disturbances that may produce some severe weather across parts
of the plains Tuesday afternoon. Models have been pretty consistent
on this so confidence is increasing. Also increasing, is the shear
forecast off of the models. The 12z run of the 12 km NAM now has 45
to 50 kts of bulk shear across much of the plains east of the I-25
corridor, and now, also, along the Palmer Divide. The convective
allowing high-res models are sending lots of convection east across
the forecast area Tuesday. One round of convection moves across the
mountains, Pikes Peak Region and Palmer Divide during the morning
into the early afternoon hours. Then, additional, more intense
convection moves across the mountains and plains during the mid and
late afternoon hours.
Shear values are greatest across the plains east of the I-25
corridor and also along the Palmer Divide. So, these would be the
areas to watch for the greatest severe potential. In particular,
the HRRR and NAM NEST are targeting Las Animas and Baca Counties and
to some extent Bent, Prowers and Kiowa Counties for the greatest
potential for severe weather. There are even indications of a
convergence zone setting up along the Palmer Divide that could help
develop a supercell along or north of the Palmer late Tuesday
afternoon. The axis of maximum CAPE (2000-3000 J/kg) during the
afternoon will be over eastern Las Animas and Baca Counties at 21z.
By 00Z, the axis stretches northward and extends into northeast El
Paso County, where values range from 500-1000 J/kg. So, there is
certainly enough CAPE for deep, strong convection across the
southeast plains. The amount of CAPE across northern El Paso County
is not exceptional but it is still sufficient for strong to severe
convection, especially if the shear is there. All severe weather
types will be possible from storms tomorrow, including the
possibility of a tornado, particularly across Las Animas and Baca
Counties, where high-res models are showing the best updraft
helicity tracks. An additional concern Tuesday will be for flash
flooding on burn scars. While storms should be easterly moving at
15-25 mph Tuesday, a strong storm over a burn scar could still cause
flash flooding.
.LONG TERM...(Tuesday night through Monday)
Issued at 332 PM MDT Mon Aug 20 2018
...Active weather continues Tuesday night through Wednesday...
Tuesday night-Wednesday night...Lastest models in good agreement of
keeping an active weather pattern across the area through the day
Wednesday, with monsoonal moisture embedded within west to southwest
flow aloft, combines with a broad upper trough progged to translate
across the Rockies through the period. Models continue to support
widespread showers and storms ongoing over and near the higher
terrain Tuesday afternoon, with storms spreading east across the far
Southeast plains evening, where a weak surface low and boundary
moving southeast through the evening, will help spread low level
moisture westward back across the I-25 Corridor overnight. This
boundary will also support the potential for severe storms through
the evening, with large hail, damaging winds and even a tornado
possible, especially across portions of Las Animas, Bent, Prowers
and Baca Counties. With moist upslope flow expected across the
Plains overnight, along with tail end of embedded shortwave ejecting
across the Rockies, will keep isolated to scattered pops in place
across the area overnight. Could see a brief lull in activity early
Wedensday morning, before the next ejecting wave starts to move into
western Colorado, with more scattered storms expected to develop
over the higher terrain late Wednesday morning, spreading east
across the immediate adjacent plains through the afternoon hours and
across the far southeast Plains once again Wednesday evening, as
said wave translates into the High Plains. Westerly steering flow of
20 to 30 kts will limit flash flooding, however, with the ample
atmospheric moisture in place, and the possibility of training
storms, will need to watch for flash flooding on area burn scars
through this period. Temperatures through the period look to be near
to well below normal, with highs Wednesday in the mid 60s to mid 70s
across the Plains.
Thursday-Friday...Drier air progged to move across the area within
moderate westerly flow aloft across the state, as last piece of
energy translates across the Rockies Thursday, pushing the monsoonal
moisture plume well south and east of the area. Best chances of
showers and storms to be across the ContDvd Thursday afternoon, with
lesser coverage of storms expected areawide on Friday. Temperatures
look to warm back to near seasonal levels through Friday.
Saturday-Monday...West to southwest flow aloft progged across the
region through the weekend and into early next week, with upper high
pressure across the Southern High Plains starts to spread monsoonal
moisture back across the Rockies. Best available moisture looks to
be along and west of the ContDvd, keeping the best chances of
precipitation over the higher terrain into early next week.
Temperatures this weekend look to be at and above seasonal levels,
with highs in the mid 80s to mid 90s across the lower elevations,
and mainly in the 60s and 70s across the higher terrain.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 332 PM MDT Mon Aug 20 2018
Generally dry across the flight area through tonight. There could be
a spotty evening shower or storm over the higher terrain but any
such occurrence should be highly localized. Tuesday morning,
monsoon moisture will increase from the west leading to the
development of a few showers and storms along the Continental Divide.
Tuesday afternoon, monsoonal moisture and disturbances will track
from west to east across the flight area, triggering scattered
showers and thunderstorms. A few severe thunderstorms will be
possible across the plains Tuesday afternoon with primary threats of
large hail, damaging winds and possibly a tornado. Otherwise, storm
threats will include lightning, wind gusts to around 50 mph, small
hail and locally heavy rain.
The KCOS, KPUB and KALS terminals should all see VFR conditions
through 18z Tuesday. After 18z, thunderstorms will be possible at
each of the sites through the afternoon.
Generally dry across the flight area through tonight. There could be
a spotty evening shower or storm over the higher terrain but any
such occurrence should be highly localized. Tuesday morning,
monsoon moisture will increase from the west leading to the
development of a few showers and storms along the Continental Divide.
Tuesday afternoon, monsoonal moisture and disturbances will track
from west to east across the flight area, triggering scattered
showers and thunderstorms. A few severe thunderstorms will be
possible across the plains Tuesday afternoon with primary threats of
large hail, damaging winds and possibly a tornado. Otherwise, storm
threats will include lightning, wind gusts to around 50 mph, small
hail and locally heavy rain.
The KCOS, KPUB and KALS terminals should all see VFR conditions
through 18z Tuesday. After 18z, thunderstorms will be possible at
each of the sites through the afternoon.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...LW
LONG TERM...MW
AVIATION...LW
Area Forecast Discussion...CORRECTED
National Weather Service Charleston WV
918 PM EDT Mon Aug 20 2018
.SYNOPSIS...
A warm front lifts north tonight, followed by one or more cold
fronts Tuesday. Cool, moist, low level northwest flow on
Wednesday. High pressure Thursday and Friday.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 830 PM Monday...
Updated forecast to lower PoP per radar and satellite trends
upstream across eastern KY. Only expect isolated light showers
overnight. Removed thunder as well through 12Z Tuesday, except
over portions of southeast OH. Allowed for periods of clearing
despite for few mid to upper level clouds passing through. If this
clearing materializes, dense river valley fog could develop
overnight. Added some fog in weather grids.
As of 230 PM Monday...
Multiple cold fronts associated with this system approach and
cross Tuesday, with showers and thunderstorms. The early timing
of more numerous showers and thunderstorms, even during the
overnight hours over the middle Ohio Valley, will limit
instability Tuesday, even as bulk shear increases. The
associated upper level crosses late Tuesday, but the last of the
cold fronts is progged to possibly lag behind the short wave.
If we could get heating at some point Tuesday afternoon, then
associated upper level cooling may be sufficient to convert the
increased bulk shear for strong to severe thunderstorms.
A warm, muggy night is on tap tonight, as the warm front pushes
through, and then temperatures on Tuesday will be largely
dependent upon the timing of rounds of showers and thunderstorms
coming through.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 250 PM Monday...
Surface low to move across the Great Lakes with cold front at
the surface Tuesday evening. Forecast area will be located in
the warmer and moist unstable air ahead of frontal passage.
Moderate instability and low-level shear, especially in
vicinity of front will allow a few strong thunderstorms to
develop. Main impacts will be damaging winds as mid level flow
increases through the day. A mid level post frontal trough will
traverse on Wednesday, bringing another round of precipitation.
After that, surface high pressure build in with ridging taking
place by Thursday.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 250 PM Monday...
Mid level flow becomes more zonal into the weekend with 5H
trough lifting north of the Great Lakes. Followed central
guidance with some tweaks for Wednesday night as blends where a
little tardy in clearing precipitation east of the region.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 807 PM Monday...
Visible satellite imagery show mostly clear skies downstream
across northeast KY, with few mid to upper level clouds passing
by before sunset. Depending on the cloud cover, as areas of
clearing could produce enough radiational cooling, together with
weak BL winds, IFR dense fog formation could be possible,
mainly along the river valleys overnight. Otherwise, MVFR
ceilings could linger across the northeast mountains, and VFR
conditions should prevail elsewhere.
This thinking is contrary to all guidance that shows plenty of
clouds, showers and storms tonight, except for the high resolution
model HRRR which brings dry conditions. So confidence is medium
counting with my gut feelings. The probability of pcpn has been
lowered. Removed thunder from TAF tonight as can not find any
substantial forcing mechanism to sustain strong updrafts.
An approaching low pressure system will adopt the old frontal
boundary south of the area, and produce a warm front that should
lift slowly north into our northern sections by 12Z Tuesday.
Showers and thunderstorms will become more numerous Tuesday, as
a cold front approaches from the west.
The lower atmosphere could decouple to produce light to calm
winds overnight. Winds will become south to southwest on
Tuesday, becoming gusty during the afternoon along thunderstorms.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z WEDNESDAY...
FORECAST CONFIDENCE: Medium.
ALTERNATE SCENARIOS: Coverage of storms could vary on Tuesday.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE TUE 08/21/18
UTC 1HRLY 00 01 02 03 04 05 06 07 08 09 10 11
EDT 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07
CRW CONSISTENCY H H H H H H H M M L L M
HTS CONSISTENCY H H H H H H H H H H H H
BKW CONSISTENCY H H H H H M M M H H H H
EKN CONSISTENCY H H H H M M L L L L L L
PKB CONSISTENCY H H H H H H H M H H H M
CKB CONSISTENCY H H H H H H H H H H H H
AFTER 00Z WEDNESDAY...
IFR in showers and thunderstorms possible Tuesday night, and in
stratus overnight Tuesday night into Wednesday morning..
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...None.
OH...None.
KY...None.
VA...None.
&&
$$
SYNOPSIS...JSH/RPY/TRM
NEAR TERM...TRM/ARJ
SHORT TERM...KMC
LONG TERM...KMC
AVIATION...ARJ
Area Forecast Discussion
National Weather Service Blacksburg VA
943 PM EDT Mon Aug 20 2018
.SYNOPSIS...
There will be a good chance of showers and thunderstorms across the
Appalachians and central mid Atlantic region until a cold front
moves through Tuesday night. A large area of high pressure will
then build in from the midwest and bring much drier and pleasant
conditions to the region for the end of the workweek.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 940 PM EDT Monday...
Flash Flood Watch will remain in effect through 6AM.
Band of showers and thunderstorms across North Carolina
continued to move northeast this evening. Short term models
suggest this feature will continue through at least 2AM but may
be weakening after midnight. Still the potential for localized
high rainfall rates so no changes to the Flash Flood Watch at
this time. Only minor adjustments to overnight lows.
Low pressure moving up into the Great Lakes will push a cold
front into the region from the west Tuesday. Indications are
that effects of the wedge will continue to produce enough shear
for organized convection while the dynamic environment results
in enhanced lift and surface based instability increases. This
should generate robust convection with some severe thunderstorms
possible through early tomorrow evening. There will also be a
continued threat for heavy rainfall but will wait to see where
heavy rain falls tonight before determining if any additional
flash flood watches are necessary.
Conditions tonight will remain on the mild and muggy side while
highs Tuesday will be close to normal.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 320 PM EDT Monday...
In terms of highlights, strong to severe thunderstorms will in all
likelihood still be marching eastward across the Piedmont very early
in the short-term period (early Tuesday night). A more spatially
limited convective threat may exist on Wednesday afternoon,
preceding a significant air mass change toward cooler and drier
weather that settles in late Wednesday night into the rest of the
week.
Convection in association with a pre-frontal surface trough, tied to
filling surface cyclone in the St. Lawrence River Valley and parent
deamplifying shortwave trough, should be progressing east across the
foothills/Piedmont region by mid-evening Tuesday. Storms may still
be on the strong side through this period, but should be exiting
rather quickly east. The passage of this trough isn`t likely to
result in much change in terms of temps or humidity level, but it
will shift winds to the west allowing for some clearing into the
overnight. The exception is in the west slopes of the Appalachians
where some residual low clouds/stratus project to linger. Lows
mainly in the 60s, warmest further east.
We`ll then await the passage of the primary cold front/850 mb
thermal gradient. This front appears to clear the western
mountains/Blue Ridge by early afternoon with little fanfare ahead of
it. Across the VA/NC Piedmont and Southside though, heating of a
continued rather moist air mass per the NAM should result in about
1500-2000 J/kg of surface-based CAPE, along with favorable west-
southwest deep-layer shear vector magnitudes around 35 to 40 kts.
GFS on the other hand clocks in CAPE values about half as much.
Though I think storm coverage is more isolated to widely scattered
at best within an area from Yadkinville to Lynchburg east, it
wouldn`t surprise me if one or two become strong in this corridor,
particularly if the level of instability more closely follows the
NAM. Only real impact in the west is lowering dewpoints and
increasing northwest winds/gusts by afternoon due to pressure rises
and deeper mixing. May see gusts approach 30 mph at times in the
mountains late afternoon. Clearing and dry advection anticipated for
overnight. More variation in highs Wednesday with clouds/stratus
leading to cooler low 70s in the far west into southeast WV, to the
mid/upper 80s as one progresses eastward into the foothills and
Piedmont/Southside. Should see good radiational cooling Wednesday
night with lows in the 50s to low 60s.
Thursday really is a top-notch day areawide as sprawling high
pressure area builds to our north with upper-level ridge in place.
850 mb temps take a tumble into the upper single digits to low
teens, with surface dewpoints falling in lockstep into the 40s/mid
50s. This should prove to be a much more refreshing change compared
to the soupy air we`ve been stuck in the last couple days. Plentiful
sun should support highs largely in the 70s to low 80s. Clear skies
anticipated for Thursday night as well, and a better potential for
radiation fog as winds will be lighter than prior nights. Lows
Thursday night should be in the 50s, and may approach the mid/upper
40s in the sheltered mountain valleys in far southwest VA.
Overall forecast confidence is moderate, though higher confidence
for Thursday.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 320 PM EDT Monday...
Friday is pretty much a carbon copy of Thursday, as high pressure
centered over Cape Cod/southern New England will extend a ridge
along or just east of the Appalachians. Only real nuanced changes
are that surface winds become more easterly and 850 mb temperatures
are a degree warmer than Thursday.
Pattern then begins to undergo some change into the weekend and
early next week. Much of the weekend should be dry, but during the
weekend longer-range forecast guidance build a large ridge
associated with warmer temperatures which will eventually settle
across the mid-Mississippi Valley. The period of more comfortable
and cooler weather should then change to a more typical summer
regime with daily chances for showers and thunderstorms.
Temperatures should tend to be below normal initially, but by Sunday
into early next week temperatures will then trend above normal along
with an increase in humidity levels.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
As of 740 PM EDT Monday...
Band of showers and thunderstorms moving northeast out of
western and central North Carolina is expected to reach KDAN,
KROA and KBCB after 03Z/11PM. HRRR and WRFarw had similar timing
of this precipitation.
Low confidence if there will still be thunder at that time and
heavy rain producing MVFR to IFR visibilities is much more
likely. Also overnight, stratus will redevelop with IFR to LIFR
ceilings after midnight. Average confidence on timing of when
ceilings will lower.
Ceilings will remain low until well after sunrise. Similar to
Monday, it may take most of the morning for KROA and KLYH to
improve. But with a cold front approaching and southwest surface
and low level winds increasing, conditions will return to VFR in
the afternoon. Showers and thunderstorms along the front may
impact KBLF and KLWB after 18Z. Lower confidence about the
timing of the storms reaching the other area TAF sites before
00Z.
Extended Discussion...
High pressure will build in Wednesday and will be overhead by
Thursday. VFR conditions are expected with this cooler and drier
air mass through Friday. MVFR to IFR fog is possible for a few
hours each night along and near the typical river valleys,
especially west of the Blue Ridge.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Flash Flood Watch until 6 AM EDT Tuesday for VAZ014>017-022-
032-033-043-044-058.
NC...Flash Flood Watch until 6 AM EDT Tuesday for NCZ001>006-
018>020.
WV...None.
&&
$$
SYNOPSIS...MBS
NEAR TERM...AMS/MBS
SHORT TERM...AL
LONG TERM...AL
AVIATION...AMS/MBS