Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/23/17
Area Forecast Discussion
National Weather Service Albany NY
1033 PM EDT Tue Aug 22 2017
Showers and thunderstorms will be ending overnight from west to east
as a cold front passes through the region. Behind this front,
cooler and less humid air will move into the region for Wednesday
with a partly to mostly sunny sky. Mainly dry and comfortable
weather is expected for the rest of the week.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 1033 PM EDT...Surface cold front is now located over
western New York and it continues to track eastward towards our
area. Ahead of the boundary, MRMS imagery continues to show two
bands of convection, with the heaviest activity now stretching
from western New England back towards the Hudson Valley. The
threat for the strongest and damaging winds along this line are
now mainly located east of area from southwestern NH towards the
CT River Valley of western Massachusetts, although pockets of
gusty winds and locally heavy rainfall are still ongoing across
our parts of extreme eastern NY and western New England. The
Severe Thunderstorm Watch is still in effect until Midnight,
although it may be able to be cancelled early if radar trends
MRMS is showing 1 hour rainfall totals in excess of one inch
across parts of central Berkshire County, so the threat for
localized urban/small stream flooding is still in place for the
next few hours. Some heavier rainfall of 0.50 to 0.75 inches per
hour is also occurring across parts of the eastern Catskills and
mid Hudson Valley as well. Heavy rainfall should be progressive
enough to avoid widespread flash flooding, but will need to
watch MRMS trends closely over the next few hours.
3km HRRR shows the main band of convection should continue to
slide eastward and the secondary band of lighter activity just
ahead of the front should weaken and dissipate by 1 or 2 AM. The
front should cross the area by late tonight, but any notable
cooling or drier air moving into the area probably won`t occur
until during the day Wednesday. Skies should start to clear out
by late tonight with the passage of the front. With the frontal
passage not occurring until very late, it will still feel
rather sticky and mild overnight, with lows in the 60s for most
locations. Some patches of fog will likely develop late in the
overnight, especially in areas that saw heavier rainfall.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Behind the front, cooler and less humid air will work into the
region. Mainly dry weather is expected through Wednesday,
although cannot totally rule out a lingering rain shower across
the Adirondacks or Mohawk Valley for later Wednesday into
Wednesday night, as the passing upper level trough picks up
some moisture off Lake Ontario and allows for a lake-enhanced
shower or two. Highs on Wednesday will reach the mid 70s to low
80s. Overnight lows will mainly be in the 50s, with some 40s
across the higher elevations. Sky cover will generally be partly
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Extended period of fair weather with slightly below normal
Canadian high pressure at the surface will build in and shift
southward as it expands across the Great Lakes region and the
Northeast over the weekend into early next week. An upper level
trough will remain over region.
Short waves are expected to rotate through the trough on Thursday
and Friday. Some afternoon showers possible each day from sun`s
heating and cold air/troughiness aloft, mainly over higher terrain.
Looking at temperatures around 5 degrees below normal with highs
generally in the mid 60s to upper 70s and lows in mid 40s to mid
50s. Cooler readings are expected across the higher terrain of the
western Adirondacks, eastern Catskills and southern Green Mountains
In addition to the cooler temperatures, we will have low humidity
levels with dew points in the 40s and lower/mid 50s.
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Line of showers and some strong thunderstorms currently extends from
the Lake George area to KGFL southwest to the Catskills. We expect
this line to continue to move southeast this evening and bring
thunderstorms to all the TAF sites between 23/00Z and 23/05Z.
Some fog may develop after midnight with the moist ground and
rain cooled atmosphere. At this time, expecting only MVFR fog
as winds and drying behind the cold front should be strong
enough to keep dense fog from forming.
Frontal passage is expected between 06Z and 12Z Wednesday with
the winds shifting from southwest to the northwest behind the
front. Winds Wednesday will be mainly from the northwest at 5 to
Wednesday-Saturday: No Operational Impact. NO SIG WX.
Most areas should see a wetting rainfall this afternoon and
evening due to the passage of a pre-frontal trough and surface
cold frontal boundary. Southerly winds will be 15 to 20 mph
today with gusts up to 30 mph, and will switch to the west by
tonight at 5 to 15 mph.
Behind the front, cooler and less humid conditions will be in
place for the rest of the week. RH values look to fall to 45 to
55 percent on Wednesday afternoon with westerly winds of 10 to
A line of strong to severe thunderstorms will cross through the
area this afternoon and evening. Any thunderstorm will be
capable of producing locally heavy downpours and could lead to
isolated flash flooding. The locally heavy rainfall may also
result in minor flooding of urban, poor drainage and low lying
areas. Behind this frontal system, mainly dry weather is
expected for the rest of the week.
Basin average rainfall on Tuesday will generally be around a
half of an inch to an inch, although point totals may be
higher. This rainfall will only allow for minor rises on rivers
and streams. River and stream levels should quickly recede by
Wednesday and then remain steady for the rest of the week.
For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.
The KENX radar will likely be down through at least Friday,
September 1st for the bull gear replacement. We are waiting for
a ROC maintenance team and parts to arrive to assist local
technicians with the repairs.
CT...Severe Thunderstorm Watch until midnight EDT tonight for
NY...Severe Thunderstorm Watch until midnight EDT tonight for
MA...Severe Thunderstorm Watch until midnight EDT tonight for
VT...Severe Thunderstorm Watch until midnight EDT tonight for
Area Forecast Discussion
National Weather Service State College PA
1035 PM EDT Tue Aug 22 2017
A strong cold front will move through the region overnight.
Much cooler and drier conditions will return for the second half
of the week into the weekend. Temperatures will average a few
degrees below normal highs starting tomorrow and lasting into
early next week.
.NEAR TERM /UNTIL 8 AM WEDNESDAY MORNING/...
The last of the potentially severe storms has cleared Lancaster
county. Additional showers are moving east along ther Maryland
border and there is also a line of showers moving through the
The main windshift line associated with the cold front is just
now entering NW PA. The RAP anal shows the frontal trough
jumping out to the east over central PA. The front will
continue to accelerate through the area overnight ushering in
markedly drier air by morning.
POPs will taper off rapidly after midnight as drier air moves
in behind the front. Some areas of fog are possible late at
night as skies beging to scatter out.
.SHORT TERM /8 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
Wednesday will be noticeably drier as the PW values crash to -1
sigma below normal after being well +1 to +2 sigma above
normal. It will also be significantly cooler. The 850 hPa
temperatures fall to near normal Wednesday and will fall below
normal overnight Wednesday into Thursday.
Chance of rain should be very low Wednesday.
The cool air aloft will likely produce some cumulus in the
mountains during the afternoon hours.
It should be a nice and notably cooler day.
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
An extended period of early autumn-like weather will begin
Wednesday and continue right through the upcoming weekend as a
-2 sigma upper trough (and similarly anomalous/cool 850 mb
temps) move over the Great Lakes and NE U.S.
1026-1028 mb SFC High (+2-3 Sigma) over south-central Canada
will drift slowly to the Great Lakes by this weekend
Daytime high temps will be about 5-7 Deg F below normal across
the Western Mtns on Wednesday, though still just slightly below
normal across the SE zones prior to the arrival of the
deeper/colder air for the latter part of the week.
GEFS mean 850 mb temps will dip about 2-3 deg C in all locations
for Thursday-Sunday, leading to max temps averaging 5-10 F
below normal (with min temp departures about 10-13F below
normal Friday-Sunday) as a large Canadian High Pressure area
pushes SE across the Glakes Region and becomes centered over the
Lows Fri/Sat/Sun mornings with high centered overhead will be
dipping into the l-m 40s over the Northern Mountains (and deeper
valleys of the Central Mountains) and solidly into the 50s
elsewhere. Some of the perennial cold spots near and to the east
of KBFD could see readings of 38 or 39F.
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Most of the eastern areas mostly sunny with some cumulus clouds
about making for a bumpy ride in the boundary layer. Over
western PA and OH there is a line of strong and severe storms.
Strong winds and large hail are possible. Check radar before
flying over western PA this afternoon and central areas this
The line of storms will move east this afternoon and evening.
Areas of patchy fog will develop around/after midnight. Spotty
MVFR and IFR.
Conditions will improve rapidly Wednesday morning, as cool
Canadian high pressure builds into the area.
Wed...AM low cigs BFD/JST, otherwise VFR.
Thu-Sat...No sig wx expected.
KCCX is fixed with new motor installed.
NEAR TERM...La Corte
LONG TERM...La Corte/Lambert
Area Forecast Discussion
National Weather Service Green Bay WI
1052 PM CDT Tue Aug 22 2017
Updated aviation portion for 06Z TAF issuance
Issued at 220 PM CDT Tue Aug 22 2017
Generally quiet late-summer weather into early next week.
Seasonably cool the next couple days, then temperatures close to
The large scale pattern will complete an amplification cycle the
next couple days as a rather strong upper trough becomes
established from eastern Canada into the lower Great Lakes region.
Jet energy working east across Canada will cause the trough to
begin weakening by late in the week. By early next week, the main
westerlies will recede north into Canada, leaving just a weak
remnant of the trough lingering across the forecast area.
Temperatures will begin the period below normal, then rebound to
near normal levels by the weekend. Rainfall will be limited with
precipitation events consisting of just scattered showers. As
such, amounts for the period are likely to end up below normal.
.SHORT TERM...Tonight and Wednesday
Issued at 220 PM CDT Tue Aug 22 2017
The latest RAP analysis and satellite/radar imagery show upper
troughing settling over the western Great Lakes early this
afternoon. A widespread cu field has developed across the region,
though cu has the most vertical extent over far northwest WI and
northeast MN where the highest capes reside. Some of this more
enhanced cu and even a few showers will move into north-central WI
later this afternoon. As cold air continues to funnel across the
region, forecast concerns revolve around light showers early this
evening, followed by lake effect showers/drizzle late tonight.
Tonight...As a secondary surge of cold air arrives from the
northwest tonight, high res models continue to indicate that
scattered showers will persist over north-central WI through the mid
evening hours. Then attention turns to precip off western Lake
Superior overnight. 1000-850mb flow veers around to the NNW
direction after midnight, which is a good trajectory for showers or
drizzle to move into north-central WI. Increased cloud cover some
late as a result, but 10-15 kts of low level flow should not be
strong enough for these clouds to move into central or east-central
WI. With enough wind to prevent temps from tanking, should see lows
ranging from the mid 40s north to mid 50s south.
Wednesday...Broken cloud cover along with patchy drizzle/showers
will likely linger into the mid-morning hours over northern WI. With
day time heating, however, think mixing will cause these clouds to
scatter by midday. Elsewhere, should see scattered fair weather cu
develop, which will lead to a partly cloudy day for most. Highs
ranging from the low 60s in the far north to mid 70s at Wautoma.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 220 PM CDT Tue Aug 22 2017
At low-levels, a cool, dry Canadian air mass will settle across
the area and linger through the weekend. Some pretty chilly
nights are likely unless clouds move through during the nighttime
hours. The typical cool spots across the north will probably fall
into the 30s Wednesday night and Thursday night, and would not be
surprised if there is some patchy frost. The anticyclone and its
associated air mass will linger across the area for much of the
forecast period, but moderation of the air mass should allow
temperatures to rebound to near seasonal levels by the weekend.
While the dry anticyclone dominates at low-levels, the forecast
area will be at least brushed by some middle and upper level
shortwave energy at times. That will lead to some clouds and
maybe some showers. But given the limited moisture, any rains are
likely to be scattered and light.
Tweaked mins down in the typical cool spots Wednesday night and
Thursday night, but tempered the adjustments some due to uncertainty
about passing clouds. Otherwise, the standard forecast
initialization grids based on a broad blend of model output seemed
reasonable, so no other significant changes were necessary.
.AVIATION...for 06Z TAF Issuance
Issued at 1026 PM CDT Tue Aug 22 2017
VFR conditions will rule over most of the TAF sites through the
period. The one main exception will be across far north-central
Wisconsin where cool north-northwest flow off Lake Superior will
bring some low clouds and patchy light showers or drizzle
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
251 PM PDT Tue Aug 22 2017
.SYNOPSIS...Near normal temperatures will persist across central
California through Friday with a warming trend this weekend into
early next week. Otherwise...thunderstorms will be possible over
the Sierra Nevada each afternoon and evening through Thursday.
.DISCUSSION...An upper low remains nearly stagnant off the central
California coast this afternoon...bringing another shot of showers
and thunderstorms to the Sierra Nevada this afternoon and early
evening. Showers were developing across the Sierra from Fresno
county north toward Yosemite National Park. Any storms that do
form are forecast to move north northeast. The HRRR and high res
ARW are showing very little activity this afternoon and evening
while the NMM and NAM are showing quite a bit more activity.
Either way...it looks like the Sierra should see quite a bit less
activity compared to the past few days.
In addition to thunderstorms...the upper low has kept temperatures
seasonable across the area....with San Joaquin Valley readings
forecast to top out in the mid 90s.
The upper low is forecast to move slowly east southeast into
southern California early Wednesday afternoon...resulting in an
increase in thunderstorm activity. The high res models are in good
agreement tomorrow...especially from Sequoia National Park
northward. The movement of storms tomorrow will switch to a more
westerly direction...with possible thunderstorm cloud blow off
possibly entering the foothills and valley by the early evening
There is a possibility of thunderstorms again on
Thursday...however confidence is much lower compared to today and
Upper level high pressure will begin to build over the desert
southwest Friday into the weekend resulting in a warming trend
across the region. Triple digits will once again be possible over
the San Joaquin Valley Saturday and continue into the weekend.
Dry weather will also prevail across the area Friday into at least
early next week with high pressure firmly in place.
Unfortunately the above normal temperatures do not look to come to
an end anytime soon. According to the Climate Prediction Centers 8
to 14 day outlook (valid from August 30th through September 5th)
there is a good chance of above normal temperatures for the entire
.AVIATION... Isolated to scattered thunderstorms will occur over the
Sierra after 20z today through 03z Wednesday. Areas of smoke are
possible Near Yosemite National Park in association with the South
Fork Wildfire. Otherwise VFR conditions can be expected over much of
the central CA interior during the next 24 hours.
.AIR QUALITY ISSUES...
Please see SFOAQAHNX for an Air Quality Alert
The level of certainty for days 1 and 2 is medium.
The level of certainty for days 3 through 7 is high.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.php for additional information
an/or to provide feedback.
Area Forecast Discussion
National Weather Service Wilmington NC
740 PM EDT Tue Aug 22 2017
Warm and humid weather will prevail through mid week. An
approaching cold front will bring increasing storms over the
area late Wednesday into Thursday. Canadian high pressure will
bring an early fall feel Friday and into the weekend. Breezy
conditions may develop late Sunday into Monday, as a possible
tropical low passes offshore and interacts with the Canadian
.NEAR TERM /THROUGH WEDNESDAY/...
As of 730 PM Tuesday...Weak high surface high pressure off the
coast will begin to retreat tonight as the pressure trough
surrounding a cold front over the Ohio Valley approaches from
the northwest. Pressures should fall by about 3 millibars along
the coast tonight in advance of this feature. Diurnal
thunderstorms are diminishing now that the sun is setting and
the boundary layer is stabilizing. Short-range high res models
(HRRR and NAM) show no precip potential for the next 8-9 hours.
What may develop some showers or t-storms late tonight or
Wednesday morning is the landbreeze. In the same way the
seabreeze develops due to air temperature/density differences,
cooler air inland will surge offshore late tonight creating a
boundary that can initiate convection and precip. The HRRR is
focused on the 6-8 AM timeframe along the beaches and just
offshore. With the steering flow aloft I imagine the bulk of any
activity will develop and remain offshore.
No significant changes have been made to overnight low
temperature forecasts, still mid to upper 70s for most
.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 300 PM Tuesday...Cold front entering western zones in
addition to some height falls and weak vorticity centers ahead
of the main belt of westerlies buckling into deep troughiness
north of New England States. With several factors leading to
lift thunderstorms will not exhibit their normal diurnal
decrease, or at least display a much lessened one. Wind fields
look weak enough to preclude a severe weather threat. Shower and
thunderstorm chances will remain pretty high early Thursday
night, highest along the coast. Then some dry air pushes in
rather strongly from NW to SE during the latter portion of the
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 300 PM Tuesday...The mid level pattern will initially
feature a decent trough for late August. The flow will quickly
transition to a more zonal configuration by the end of the
weekend. At the surface a cold will push into the Bahamas by
early Saturday with high pressure building down into the
Carolinas. Friday and Saturday should be cooler and mostly dry
although the easterly flow may keeps some low clouds and perhaps
a light shower or two offshore around.
The forecast gets interesting later in the period when the global
guidance spins up what could be a tropical system along the residual
front and moves it up off the southeast coast. The guidance has been
showing this for a few cycles but the disclaimer of its pretty far
out in time still holds. I did keep a partly to mostly cloudy
forecast intact with some pops increasing especially along the
coast. Temperatures will be on the cool side especially for highs
more near normal for overnight lows.
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 00Z...A cold front approaching the area from the northwest
is still west of the Appalachians and won`t directly affect our
area until Wednesday night at the earliest. Today`s afternoon
thunderstorms are falling apart now that the sun is setting and
we`re expecting the next 8-9 hours to be quiet with only mid-
level altocumulus and perhaps a little low cumulus near the
A landbreeze should develop an hour or two before sunrise. This
boundary will develop scattered showers and maybe an offshore
thunderstorm. These will probably just far enough east to not
have significant effects on the coastal airports (ILM, CRE, MYR)
however they may approach within the vicinity (5-10 miles).
Where surface wind speeds are lightest inland, MVFR visibilities
are possible at FLO and LBT.
Scattered showers and t-storms should pop up during the heat of
the day Wednesday. The best potential should be near the coast
during the late morning and early afternoon, shifting farther
inland during the mid to late afternoon with the seabreeze.
Extended Outlook...Showers and t-storms Wednesday night and
Thursday associated with a cold front could produce localized
IFR conditions. Most showers and storms will push offshore
Thursday night into Friday. MVFR ceilings could linger,
especially near the coast Friday.
NEAR TERM /THROUGH WEDNESDAY/...
As of 730 PM Tuesday...Falling pressures across interior North
Carolina and Virginia tonight ahead of an approaching cold front
should keep wind speeds up in the 10-15 kt range most of the
night. Seas already 2.5 to 3.5 feet could build by another 0.5
to 1 foot by late tonight in a choppy short-period wind wave.
Shower activity is currently absent from the coastal waters,
however a landbreeze pushing off the coast between 4-6 AM should
help develop a line of showers and perhaps a thunderstorm
SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 300 PM Tuesday...Prefrontal flow regime Wednesday night
will have a few knots of wind speed knocked off as cold front
and its associated pressure trough approaches. The front will
move quite slowly and so most of Thursday will feature very
gradually veering winds, through FROPA itself will still likely
lead to a quicker turn to NE. With the front nearly stalling not
far to our south the NE winds will not pick up significantly.
LONG TERM /FRIDAY THROUGH SUNDAY/...
As of 300 PM Tuesday...Not the best of weekend`s coming up for
the marine community as high pressure will be building down into
the area from the north. At the same time a front will become
stationary to the south and keep the gradient elevated. For
basically the entire period expect northeast winds of 15-20
knots. Seas will be elevated as well with values from 3-6 feet.
Area Forecast Discussion...CORRECTED
National Weather Service Medford OR
326 PM PDT Tue Aug 22 2017
.Edited portion of AFD.
.DISCUSSION...Over the next 7 days the weather conditions will evolve
from warm and unstable to cool and stable, to hot and dry...with
continual periods of smoke affecting the forecast area.
The next two days will feature thunderstorm chances, focused today
over northern California, extending into Southern Oregon later this
afternoon and evening. There is potential for nocturnal storms as
disturbances aloft make their way south to north into Oregon.
Tomorrow a cold front will approach the forecast area and
gradually introduce a westerly component to the upper level winds,
drying out the midlevels and stabilizing the atmosphere. This
will push the threat from thunderstorms eastward tomorrow,
primarily along and east of the Cascades. We have Red Flag
Warnings out at RFWMFR for the expected abundant lightning on dry
fuels today and tomorrow. Some of the storms will produce heavy
rain, and we have a Flash Flood Watch at FFAMFR to highlight the
threat for flash flooding on some of the recent wildfire burn
scars in Siskiyou and Modoc Counties. Note that we do expect
plenty of lightning outside of storm cores, so new fire starts are
still expected despite some wetting rainfall.
Smoke is another big concern, impacting a majority of the forecast
area. In general, air quality has trended similar or worsened
compared to yesterday. The HRRR smoke models suggest some
improvement tomorrow but with similar wind flow, we have maintained
an Air Quality Alert out through tomorrow afternoon for much of the
West Side, Cascades, and portions of the East Side to around Highway
97. Brookings and the Curry County coast should continue to see
periods of poor air quality through tomorrow at least, based on weak
winds, overnight drainage northeast winds down the Chetco drainage,
and the abundant smoke from the nearby large fire.
A cooler air mass, not surprisingly, will accompany the cold front
on Thursday, but this trend towards lower temperatures will be very
brief. 850mb temperatures, a good indicator for trends of surface
temperatures, rise starting Friday and peak Monday or Tuesday. 850mb
temperatures reach the top 5 percent for this time of year on
Monday per GEFS output, and temperatures could reach 100 degrees
in the Rogue Valley. The surface temperatures will partially
depend on the amount of smoke in the area, so that will have to be
continually evaluated. Needless to say, the fire environment will
become hotter and drier late this week into the weekend. We have
increased northeasterly overnight winds near the coast as the
thermal trough strengthens into the weekend. Looking at cross-
sections of the atmosphere on Monday, relative humidity values
throughout the column are all 10 to 25 percent...indicating an
extremely dry air mass.
.AVIATION...22/18Z TAF CYCLE...Onshore flow is keeping LIFR/IFR
cigs/vis at the coast and just offshore. It is possible that the
OTH TAF site sees some clearing this late morning and early
afternoon with some breaks in the cloud decks.
Elsewhere smoke from wildfires blanket southern Oregon and this is
affecting visibility at most terminals. Look for visibility to
drop down to to IFR at some sites and MVFR for inland areas because
of the smoke. Isolated to scattered thunderstorms are possible
later this afternoon and evening with Klamath Falls at greater risk
for thunderstorms near or over the terminal. -Petrucelli/Smith
.MARINE...Updated 130 PM PDT Tuesday 22 August 2017...A weak
thermal trough near the coast will strengthen Thursday...bringing
increasing north winds and steep seas to the area into the
OR...Red Flag Warning until 11 PM PDT this evening for
Red Flag Warning from 1 PM to 8 PM PDT Wednesday for ORZ624-625.
Flash Flood Watch until 11 PM PDT this evening for ORZ028.
CA...Red Flag Warning until 11 PM PDT this evening for
Red Flag Warning from 1 PM to 8 PM PDT Wednesday for CAZ285.
Flash Flood Watch until 11 PM PDT this evening for
Pacific Coastal Waters...Small Craft Advisory from 11 PM this evening to 5 AM PDT
Thursday for PZZ356-376.
Area Forecast Discussion
National Weather Service Morristown TN
924 PM EDT Tue Aug 22 2017
.DISCUSSION...Initial broken line of showers and thunderstorms has
basically faded away in the relatively stable air well ahead of
the main pre-frontal trough making progress through Middle
Tennessee. RAP, HRRR predict quite a bit of weakening of the
southern portion of the line heading through the post midnight
period, although the WRF doesn`t agree. Believe there will be
continued weakening as convection gets closer to the forecast area
but not as much as the previously mentioned mesoscale models.
Therefore, will tweak pops up a little south of I-40. Temperature
drop will be held up a bit under the alto cu ceilings advancing
with the front but current forecast looks ok.
Area Forecast Discussion
National Weather Service Pueblo CO
320 PM MDT Tue Aug 22 2017
.SHORT TERM...(This evening through Wednesday)
Issued at 319 PM MDT Tue Aug 22 2017
Thunderstorms developing over the mountains and along the Raton
Mesa at mid-afternoon, with very slow n-ne drift to most convection.
Air mass over the plains is moderately unstable, but soundings
suggest a rather stout cap will continue to suppress convection,
especially east of I-25. HRRR occasionally suggests a few storms may
drift eastward across the I-25 corridor and along the NM border
later this the evening, so will keep some low pops in place along
and west of the interstate. Models suggest best coverage of
convection will be across the central mountains late this afternoon,
with perhaps some southward development into the nrn San Luis Valley
during the evening. Given slow storm motions and weak shear, main
storm threats will continue to be flash flooding, especially over
recent burn scars. Convection fades away overnight, with just some
sprinkles lingering over the peaks by early Wed morning.
On Wed, a little less in the way of convection over the mountains as
air mass dries slightly, though still enough moisture for isolated
to low end scattered pops most areas. Cap looks weaker on the
plains, with both NAM and GFS developing some isolated storms along
and east of I-25 from very late afternoon into the evening. Again,
flash flooding will be the main storm threat, though swly steering
currents do increase as weak upper jet migrates eastward across CO,
which should lead to slightly faster storm motions versus the past
few days. Max temps will climb back toward seasonal values, with 3-6
degf of warming at many locations.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 319 PM MDT Tue Aug 22 2017
Wed night an upper level ridge will be over the area with enough
moisture over the area for isold to sct showers/tstms. The GFS has
better chances for pcpn Wed night than the NAM. On Thu an upper
level disturbance moves acrs CO, aiding in the development of pcpn
acrs southern CO. The forecast models are still showing better pcpn
chances for the southeast plains Thu night as that disturbance moves
acrs the area, with the potential for areas of heavy rain. There
could also be a few severe storms over the eastern plains.
The upper ridge rebuilds over the area on Fri behind that upper
wave, and Fri looks drier, although there should still be isold to
sct pcpn mainly over the higher trrn.
On Sat the upper ridge will be centered over the Great Basin, with
north to northwest flow aloft over southern CO. A weather
disturbance is forecast to move through eastern CO in that northwest
flow in the afternoon and evening, and it looks like fairly
widespread pcpn could occur over the southeast plains. The upper
ridge remain centered over the western states on Sun. The best
chances for pcpn on Sun are expected to be over the mtns, but a
disturbance may brush the far eastern portions of CO Sun night,
bringing increased pcpn chances to areas near the KS border.
The northerly flow aloft continues on Mon, with yet another
disturbance making its way south acrs the area to help increase pcpn
chances through Tue morning. A sfc fronts moves into southeast CO
Tue. After the morning hours, the plains may dry out but the mtns
and adjacent areas should see pcpn in the afternoon and evening.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 319 PM MDT Tue Aug 22 2017
TSRA will continue over the mountains this afternoon and evening,
and will include a VCTS mention at KALS as a few storms may drift
across the San Luis Valley. Also a low chance of a TSRA at KCOS
this evening as storms move away from the mountains, though for
now will monitor radar trends and keep any mention out of the TAF
until storm coverage increases. Convection slowly decreases
overnight with VFR conditions most areas by Wed morning. Cycle
continues Wed afternoon with storms developing over the mountains
after 18z, then drifting toward lower elevations beginning 20z.
Terminals will have a low chance of storms after 20z, though storm
coverage will remain fairly isolated at lower elevations.