Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/08/18
Area Forecast Discussion
National Weather Service Denver/Boulder CO
904 PM MDT Tue Aug 7 2018
.UPDATE...
Issued at 904 PM MDT Tue Aug 7 2018
Convective activity has pushed east over the plains this evening,
with just a few storms left. Have decreased PoPs over the
mountains and urban corridor for this, and will let the current
Severe Thunderstorm Watch expire. However, the upper trough axis
is still stretched northeast to southwest through South Dakota and
Wyoming, with some isolated stronger storms ahead of it in
Wyoming and Nebraska. Have left slight chance to chance PoPs over
the eastern plains to account for this, while further west towards
the urban corridor and mountains the airmass is drying. Some
southeasterly winds south of the Palmer Divide seems to be brining
some return moisture that will bring showers and thunder to Park
County and the Palmer Divide over the next few hours. Will keep a
mention of possible storms over the aforementioned areas through
midnight, then still a slight chance east of the Palmer after
midnight.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 300 PM MDT Tue Aug 7 2018
Hot upper level ridge towering over the western one-forth of the
CONUS will move little next 24 hours. Forty-80kt northwest flow
aloft on its east face appears to contain another weak mid-level
shortwave disturbance. This wave is now over central Wyoming as
per GOES-16 water vapor satellite imagery and model 500-250 mb QG
vertical velocity fields. This disturbance is forecast to sweep
southeast over northeast Colorado this evening. Next is the
northward flow of low-level moisture on the plains of ern CO.
The cumulus clouds racing northward over Lincoln and Washington
Counties marks the axis of this moisture feed. Sfc convection has
been much slow to initiate today, but RAP and NAMNest show the
CIN all but gone now. Model CAPE fields at the present time
anywhere from 1200-2400 J/Kg on the plains. Over the next few
hours, CAPES increase even further with a bulls eye of sfc based
CAPE close to 4000 J/Kg sitting southeast of the Denver metro area
around 23z today, near the center of a Denver Cyclone. Cyclone is
already evident in observation and HiRes model wind fields.
Douglas, Elbert and Lincoln Counties already under a Severe
T-storm Watch. I can see this watch being extended northward to
include at least the southern half of the I-25 corridor, including
the greater Denver metro area. Biggest concern with the available
deep layer shear and very high CAPE will be very large hail and
damaging outflow winds. It`s conceivable storms firing over and
south of the Denver metro area during the next couple of hours
could produce hailstones at least 2 inches in diameter. Looking
north again, isolated supercells now forming in southeast WY are
expected to track southeast acrs northeast CO counties during the
next several hours. These storms will also have the potential to
produce very large hail, possibly up to 1.75 inches in diameter.
Could see this area also coming under a SVR t-storm watch. Storms
just about anywhere will be capable of producing strong outflow
winds. Could see t-storms on the plains lingering late into the
evening, and possibly beyond midnight in the far eastern CWA
counties. Deeper moisture out there could lead to heavier rainfall
amounts, possibly resulting in localized flooding.
Most of this storm activity should end by midnight with drier air
spreading down from WY in the wake of this evening`s shortwave
trough.
On Wednesday...northwest flow aloft appears a bit drier over the
area. However, models show yet another weak mid-level disturbance
embedded in this flow sweeping over northeast CO by mid to late
afternoon. QPF and model radar reflectivities not as widespread
or as intense as today. Therefore, will go with lower PoPs. Even
with less cloud cover and slightly warmer temps aloft, high temps
expected to be about the same as today.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 300 PM MDT Tue Aug 7 2018
Trend toward more quiet weather in the extended as atmosphere
dries out and high pressure builds. 500mb high pressure centered
over Nevada through the end of the week extending north to Canada.
Upper flow over Colorado is northerly and weak for the rest of
the work weak. By Friday a trough moving into British Columbia
causes a positive tilt to the ridge and flattens the ridge out,
and upper flow even becomes northeast across the forecast area
through the weekend. Monday and Tuesday upper flow becomes more
variable. Moving on into the weekend jet stream westerlies remain
north along Canadian border, with weak flow aloft over the
forecast area. GFS and ECMWF Monday and Tuesday bring a closed off
upper low north from Texas into western Kansas, but right now keep
it east of the forecast area. Absent any forcing will have
diurnal chances for showers and thunderstorms over the higher
terrain, and dry out on the plains on a daily basis through the
extended period. Light southerly low level flow over the plains
in weak lee trough, with light terrain affected winds in the
mountains.
No change in airmass during this period, and temperatures will be
consistently near normal with little change from day to day for
highs and lows. Highs in the 70s mountains and 80s plains, and
lows in the 40s mountains and 50s plains.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday afternoon)
Issued at 904 PM MDT Tue Aug 7 2018
Best storm chances have moved east, yet some weak echoes continue
to form north of DEN - these aren`t expected to impact the
airports though. East- southeast winds of 7-14 kts will turn
southerly later this evening at 5-12 kts. Another upper- level
weather disturbance will swing out of Wyoming tomorrow afternoon
to produce isolated to widely scattered thunderstorms over and
near the Front Range, but storm coverage is expected to be less
with a drier and slightly less stable atmosphere. One or two
storms could move across the metro area after 21z producing a
brief rain showers and wind gusts to 35 kts.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Kriederman
SHORT TERM...Baker
LONG TERM...Hanson
AVIATION...Baker/Kriederman
Area Forecast Discussion
National Weather Service State College PA
1137 PM EDT Tue Aug 7 2018
.SYNOPSIS...
Humid and stormy weather will continue through midweek with
strong to locally severe thunderstorms possible. Thursday looks
like a drier day before an unsettled pattern redevelops over
the weekend through early next week.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
Radar is starting to quiet down as the strongest cluster of
storms moves through the lower Susq Valley. HRRR indicates just
a couple of isolated cells after 00Z/8PM. So I trimmed the POPs
down showing a mainly quiet overnight.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH 6 PM WEDNESDAY/...
After a quiet night, convection will redevelop again on
Wednesday as the weakened frontal boundary remains over the
northeast US and an upper level trough begins to swing over the
Great Lakes.
There will be another Marginal Risk for severe storms with
moderate CAPE and slightly better deep layer shear than we saw
today. We could also see the threat for flooding rain with a
very juicy airmass in place. Models show PWATs at or around 2"
over the entire region back into the OH Valley. The wet summer
of 2018 shows no signs of abating soon.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Drier wx is likely on Thursday before an unsettled pattern
unfolds over the weekend through early next week. Models and
ensembles show a cut off low developing over the OH Valley
by the end of the weekend. Widespread precipitation is likely
to the east of the low along the Appalachians into early next
week with some potential for a heavy rainfall threat
considering slow system movement. The distribution and intensity
of the rainfall will be sensitive to the evolution of the upper
low/trough. This will be something to monitor in the coming days
especially given how wet it has been this summer.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
A shower or tstorm is possible late tonight, mainly over
northwest Pa, in association with a weak warm front lifting
through. However, the main concern overnight will be fog. Across
eastern Pa, mostly clear skies and light wind will allow valley
fog to form, especially in those locations where rain fell this
evening, such as KIPT and KLNS. Over the western half of the
state, increasing mid level cloudiness could inhibit radiational
cooling and fog potential.
Any fog should dissipate between 13Z-15Z. The focus will then
shift toward afternoon and evening showers and thunderstorms
associated with an approaching cold front. Brief reductions
appear likely as this system moves through during the PM hours.
.Outlook...
Thu...AM low cigs possible KBFD/KJST.
Fri...AM valley fog possible western Pa. Isold PM tsra impacts
possible.
Sat...Scattered PM tsra impacts possible, mainly southern Pa.
Sun...AM low cigs possible central mountains. Scattered PM tsra
impacts possible.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...Ceru/Tyburski
LONG TERM...Steinbugl
AVIATION...Fitzgerald
Area Forecast Discussion
National Weather Service Dodge City KS
1040 PM CDT Tue Aug 7 2018
...UPDATE TO SYNOPSIS...
.SYNOPSIS...
Issued at 1038 PM CDT Tue Aug 7 2018
WV imagery indicates a westerly flow aloft prevailing across the
Western High Plains. Near the surface, a stalled frontal boundary
extends from extreme southeast Colorado southeastward into the Texas
Panhandle.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 155 PM CDT Tue Aug 7 2018
There will be a chance for an isolated thunderstorm or two late
today but the better opportunity for thunderstorms for southwest
Kansas will occur overnight.
700mb moisture will be present late today ahead of an upper level
trough as it crosses southwest Kansas late today. Based on 00z
Wednesday instability and 850mb to 700mb forcing forecast late day
there will be a chance for an isolated thunderstorms or two ahead
of this upper wave in south central Kansas. Several short term
models also hinted at this earlier today so will therefore
continue with some very small chances for late day convection
southeast of Dodge City. Severe weather late today with these
isolated storms are not expected at this time time given the late
day instability and 0-6km shear but should any storm develop late
today it may be capable of producing some small hail or even some
gusty winds.
Another round of convection will be possible across southwest
Kansas overnight. This round of convection appears be to more
likely given the location of the 0-1KM theta-e axis, 850mb warm
air advection developing and location of the mid level baroclinic
zone ahead of another upper level system. This area of convection
will initially begin in Colorado and then move across southwest
Kansas during the overnight hours. The primary hazard from these
storms overnight will be strong gusty winds along with period of
heavy rainfall.
These overnight thunderstorms will taper off from northwest to
southeast early Wednesday morning as the upper level trough
crosses southwest Kansas. An upper level ridge will slowly move
east across the western United States mid week as another upper
level disturbances rotates around this ridge axis, down the north
to northwest flow, and across the Central Plains late Wednesday.
As this next upper wave passes Wednesday afternoon it will bring
with it some increasing afternoon clouds along with another chance
for thunderstorms to portions of western Kansas. Temperatures
will be cooler Wednesday afternoon compared to the past few days
given the increasing clouds and chance for precipitation. Highs
will be mainly in the 85 to near 90 degree range.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 155 PM CDT Tue Aug 7 2018
Thursday and Friday...the western United States upper level ridge
will slowly move into the Rockies as the next in a series upper
level waves rotates around this upper ridge axis and down the
northwest flow into the Central Plains. As this next upper wave
moves across the central and southern Rockies the GFS and ECMWF
were both are in agreement with cutting off this upper level
system from the mean flow early this weekend. As this closed
circulation develops there will be another chance for
thunderstorms on Friday and possibly even again early this
weekend, especially in south central Kansas. Temperatures late
week and over the weekend still appears to be on the cool side
compared to the temperatures that were experienced earlier in the
week. Based on the 850mb temperature trends the highs for the last
half of the work week and over the weekend are expected to range
from the upper 80s to around 90.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 500 PM CDT Tue Aug 7 2018
Scattered thunderstorms are expected during this TAF forecast
cycle, mainly during the overnight hours tonight. Retained the
integrity of the inherited 18z TAFs, as the TEMPO groups still
aligned with the latest HRRR iterations. HRRR shows convection
developing near the terminals around the 05-06z Wed timeframe, and
subsequently spreading SE through 12z Wed. Convective impacts are
most likely at GCK/DDC/LBL. Model consensus continues to keep HYS
dry, with perhaps a period of VCSH around 12z Wed, and kept the
HYS TAF dry. Winds outside of thunderstorms will continue to be
light, generally less than 10 kts, and at times variable in
direction.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 65 86 64 89 / 60 20 10 0
GCK 64 85 63 88 / 50 10 10 0
EHA 63 85 62 88 / 60 10 20 10
LBL 66 86 63 89 / 60 20 20 10
HYS 64 88 65 90 / 10 20 10 10
P28 69 88 66 91 / 60 30 10 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...JJohnson
SHORT TERM...Burgert
LONG TERM...Burgert
AVIATION...Turner
Area Forecast Discussion
National Weather Service Des Moines IA
645 PM CDT Tue Aug 7 2018
.SHORT TERM.../Tonight through Wednesday/
Issued at 316 PM CDT Tue Aug 7 2018
Storms have developed this afternoon along a boundary associated
with a shortwave trough moving across the state. Overall, HRRR has
had the best handle on the convection earlier this morning and
through the early part of the afternoon. The storms across north
central Iowa are expected to continue to move to the southeast, with
additional development along a boundary across central Iowa this
afternoon, continuing and strengthening some through south-
southeast Iowa 00-03Z. While stronger storms are possible, the
severe threat with these storms is relatively low. Instability and
shear parameters are marginal, with MLCAPE around 1000-15000 J/kg
and shear 35-40kts. There is also an indication that a few
funnels may be possible with higher surface vorticity across
central portions of Iowa. With the trough pushing east, overnight
lows will be a few degrees cooler than last night. With ample
moisture, fog is expected to develop around and east of I-35 by
08Z, lasting through 14z.
.LONG TERM.../Wednesday night through Tuesday/
Issued at 316 PM CDT Tue Aug 7 2018
The upper level ridge over the western CONUS will continue to become
more amplified then begin to move east Wednesday night and through
the end of the week. As this occurs, the 850 mb thermal ridge will
move east into Iowa. Warmer temperatures will arrive as a result for
Thursday with highs in the mid to upper 80s north to low to mid 90s
south. Good mixing should occur over southern Iowa by Thursday
afternoon allowing for dew points to drop into the low to mid 60s,
which will lessen the heat impacts. Farther north, pooling dew
points in the low 70s will lead to more humid conditions along with
greater instability. A boundary will drop into Iowa by the afternoon
and evening and may spark thunderstorm development. An upper level
low will begin to form over the central Great Lakes late Friday
and will form a blocking pattern thru Monday before the system
finally begins to move east. Friday through the weekend will be
mainly dry with high temperatures in the 80s. The next chance of
precipitation will arrive towards the end of the period as the
upper level low departs to the east and releases the block.
&&
.AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/
Issued at 644 PM CDT Tue Aug 7 2018
Isolated convection may briefly affect TAF sites early this
evening, but confidence towards dry, VFR conditions increases
sharply by shortly after sunset. The next question becomes fog
potential early Wed with lingering low level moisture and light
winds. Have included MVFR to isolated IFR conditions at most
sites for now until confidence in other trends increases. Conditions
should improve to VFR by mid morning.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...Hagenhoff
LONG TERM...Donavon
AVIATION...Small
Area Forecast Discussion
National Weather Service Goodland KS
943 PM MDT Tue Aug 7 2018
.SHORT TERM...(This evening through Wednesday)
Issued at 319 PM MDT Tue Aug 7 2018
Pops have been increased for the overnight period, as a shortwave
is expected to pass over our eastern CWA from Yuma County,
Colorado to potentially Wichita County, Kansas. Disturbance may
be enough lift to aid in thunderstorm development. Convection is
expected to develop over eastern Colorado and die off over the
plains. Biggest area of favored conditions will be the Palmer
Dive and to the east of it.
West Northwest wind flow aloft will aid in bringing in dryer
area, especially in the mid and upper levels. Model soundings are
showing favorable subsidence tomorrow. Pwat values are still
sitting ~1" in the low levels.
There is currently no well-defined synoptic support for
convection. But short term models like the HRRR and HREF are
pointing to late night convection from 06 to 12Z . MLCAPE values
are ~1000-1500 with about 35-40 knots 0-6 km shear. Expecting
isolated storms with marginally severe hail and winds.
Tonight, lows will sit in the upper 50s to lower 60s across the
Tri-State area. However, depending on convection, this may drop
5 to 10 degrees lower.
Lastly, tomorrow`s highs will be in the mid to upper 80s, with
another round of slight chances for convection in the late
afternoon. An isolated severe thunderstorm or two cannot be ruled
out.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 222 PM MDT Tue Aug 7 2018
A shortwave embedded in upper level ridge flow expected over the
northern Plains by Thursday morning. This shortwave moves southeast
over eastern Kansas by Friday night. During the southeastward
progression of this shortwave, thunderstorm chances will exist for
parts of the Tri-State region during the afternoon and overnight
hours. The shortwave will extend into the southern Plains due to
upper level lows settled over Oklahoma and Texas. This trough
becomes split Sunday with the main trough over the Midwest and a
cutoff low remaining over the southern Plains. By Tuesday morning,
the cutoff low over Texas migrates northward towards strong flow
aloft creating a shortwave trough over Kansas. The migration of the
cutoff low over Kansas could potentially bring precipitation to the
Tri-State region Tuesday.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 943 PM MDT Tue Aug 7 2018
An isolated thunderstorm cannot be entirely ruled out at the GLD
terminal early this morning (06-12Z), however, confidence is too
low to warrant explicit mention with the 06Z TAFs. Otherwise,
VFR conditions and light/variable winds are expected to prevail
through the TAF period.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...EV
LONG TERM...NEWMAN
AVIATION...VINCENT
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
646 PM CDT Tue Aug 7 2018
.SYNOPSIS...
Issued at 316 PM CDT Tue Aug 7 2018
H5 analysis from this morning had a strong area of low
pressure roughly 1000 miles off the coast of Oregon. Ridging
extended downstream of this feature from Oregon, north into central
British Columbia. Downstream of this feature, low amplitude flow
extended across the remainder of the northern half of the CONUS.
Within this flow, numerous shortwaves were noted from the central
plains, east into the Mid Atlantic. Further west, strong shortwaves
were noted over swrn Minnesota, and a second, weaker wave over
western Montana. At the surface, low pressure was located over
eastern Iowa with a cold front extending to the southwest into
southwestern Kansas. Weak high pressure had settled in behind the
front and was located over nern Nebraska. After fog and low
cloudiness across swrn Nebraska into portions of central and north
central Nebraska this morning, skies were clear this afternoon.
Readings as of 3 PM CDT ranged from 81 at O`Neill to 85 at
Valentine.
&&
.UPDATE...
Issued at 645 PM CDT Tue Aug 7 2018
A 21z blend of the HRRR, RAP and HREF models has correctly
predicted the development and trajectory of the ongoing
thunderstorms over the cntl Sandhills. The 00z KLBF sounding
indicates 25kt winds at 500mb which is producing very modest wind
shear. The storms should track into nern Lincoln and Custer
counties this evening and dissipate.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 316 PM CDT Tue Aug 7 2018
he main forecast challenges
tonight are thunderstorm chances and fog potential, mainly over
southwestern portions of the forecast area. During the late
afternoon hours Tuesday, the shortwave which was analyzed over
western Montana, will dive to the southeast into Wyoming, leading to
the development of thunderstorms over the higher terrain of sern
Wyoming and the front range of Colorado. The latest HRRR, Nam12 and
WARW develop convection INVOF the Cheyenne ridge during the 21-00z
time frame this afternoon forcing this into the southern panhandle,
then far southwestern Nebraska this evening as it rides
northwesterly mid level winds. Will continue the isolated pops in
the forecast this evening in the sern panhandle and far southwestern
Nebraska. As for the severe threat, not totally sold on a total
absence of severe storms across the southwest tonight. Deep layer
shear tonight is on the order of 30 to 35 KTS in the far southwest
and h7-h5 lapse rates are favorable for hail. That being said,
wouldn`t be surprised to see a strong to low end severe storm this
evening in the far southwest. Will hit this in the afternoon
issuance of the HWO. With respect to fog potential tonight,
persistence based on what occurred the last couple of nights, would
dictate a mention of fog. However, looking at the high res models
and numerical guidance for tonight, there is no support for fog
attm.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 316 PM CDT Tue Aug 7 2018
The upper level low off the coast
of Oregon, will approach the west coast of the CONUS midweek
amplifying the ridge across the intermountain west. As the ridge
amplifies in the west, one last shortwave will drift south across
Nebraska Wednesday afternoon with an increased threat for
thunderstorms mainly south of Interstate 80. After Wednesday night,
the ridge will amplify further across the intermountain west, taking
a positive tilt toward the northern plains toward the end of the
week. This will place the forecast area in northerly or north
northeasterly flow in the mid levels. With this flow regime, dry
conditions are expected at least through Saturday. The next outside
chance for pcpn may arrive across the area Sunday into Monday. The
mid range solutions this morning have trended the best forcing
further north into North Dakota and southern Canada, so a dry
forecast will be retained with this package. Temperatures in the
long range will be slightly above average with highs generally in
the upper 80s to lower 90s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 645 PM CDT Tue Aug 7 2018
Mostly isolated thunderstorms should dissipated 03z-09z tonight.
No thunderstorm activity is expected Wednesday.
Patchy valley fog may develop overnight, mainly in the Platte
valleys. burnoff should occur 14z Wednesday morning.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...CDC
SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...CDC
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
832 PM CDT Tue Aug 7 2018
.UPDATE...
826 PM CDT
Stabilizing influence from earlier storms/clouds and lake breeze
is evident as additional showers attempt shift into NE Illinois
this evening and then fade given the more subtle forcing aloft.
Next shortwave over Iowa will pivot through the area this evening
and more so overnight. Coverage will remain low, but subtle
surface boundary ahead of this will maintain shower chances
mainly along and south of I-80, maybe brief t-storm as the MLCAPE
axis remain place due to continued humid conditions. Areas north
of this axis have very limited thunder concerns for evening
outdoor activities.
The light pressure gradient and moist low levels still suggest
some fog potential overnight, especially later tonight towards
daybreak, just not clear yet as to the extent given the clouds
ahead of the upper wave.
KMD
&&
.SHORT TERM...
228 PM CDT Today through Tonight...
Evolution and timing of shower/thunderstorms late this afternoon
and evening are primary near-term forecast concerns.
Regional radar mosaic depicts an area of rain/isolated
thunderstorms spreading northeast across the forecast area this
afternoon. This activity is in association with a mid-level short
wave, which will continue its transit of the area through late
afternoon. Extensive cloud cover has helped to limit
destabilization, with temps becoming further cooled by rainfall
across areas north of I-80, thus there has been relatively little
lightning with this activity. Still, RAP soundings and SPC
mesoanalysis date depicts 500-1000 J/kg of MLCAPE exists,
particularly along an axis of slightly higher dew points roughly
along I-80 into northwest Indiana. This location may have a
greater potential for isolated/scattered thunderstorm development
this afternoon into early evening as the mid-level wave
approaches. 35-40 kt mid-level speed max will also produce an
increase in deep layer shear, suggesting at least an isolated
strong/severe wind potential with any more organized cells or
clusters. Much of the convective rainfall moving across north
central Illinois is fairly low-topped, with shallow reflectivity
centroid heights, which suggests these may be more efficient
rainfall producers than their returns would indicate. This is also
supported by low visibility observations as these cores pass
various AWOS/ASOS platforms. Bulk of this precipitation looks to
move through the Chicago metro by 430-530 pm, though additional
more isolated to scattered showers and thunderstorms are possible
into early evening as another short wave drops southeast across
the Upper Mississippi Valley into tonight. Loss of diurnal
instability should result in diminishing coverage by/after sunset
however. Moist low levels, wet ground and light winds will likely
allow for patchy fog development again tonight, especially across
areas north of I-80 where heavier rainfall is likely this
afternoon/early evening.
The second short wave is progged to clear the forecast area by
midday Wednesday. Given poor diurnal timing, have maintained only
slight chance pops mid-late morning for our southeast counties,
with rain potential generally decreasing by early afternoon as the
upper trough axis moves east of the area. Column dries out in mid
and upper levels in the afternoon in the wake of this wave, which
should allow for partly/mostly sunny skies and for temps to warm
into the low-mid 80s most areas, though light onshore flow will
keep things just a bit cooler along Lake Michigan.
Ratzer
&&
.LONG TERM...
300 PM CDT
Wednesday night through Tuesday...
For Wednesday night into early next week, the GFS and ECMWF continue
to be in reasonable agreement and the GEM is getting a bit more on
board regarding the amplification of a longwave ridge over the
western CONUS and the digging of an eastern CONUS trough, with the
eventual but relatively brief development of an upper low over the
local area this weekend.
A short warming trend that begins Wednesday will be more pronounced
on Thursday as winds turn westerly or southwesterly. By Thursday
afternoon into Friday the combination of increased low level
moisture, shortwave energy aloft, and the approach of a surface low
out of Iowa will support periods of showers and thunderstorms, with
the highest chances and greatest coverage presently appearing to be
Friday afternoon across the southern half of the forecast area.
There will also be a decent temperature contrast Friday afternoon,
with upper 70s in areas seeing onshore flow along the lake, and mid
80s in far southern locations.
Temperatures cool a bit for the weekend but shower and thunderstorm
chances persist under a digging longwave trough and developing upper
low. It is likely the weekend activity will be more diurnally
driven given the cyclonic circulation aloft and relative lack of low
level moisture or focused convergence.
By Monday the aforementioned models are already starting to push the
upper low away from the area and have moved the longwave trough axis
to our east while also indicating the approach of a surface ridge.
Given these trends the Monday afternoon period may not be dry for
the entire area but overall shower coverage should be less than
during the weekend.
Confidence obviously decreases considerably into early next week,
but early trends suggest moisture and warmth will start to work back
into the area by Tuesday.
Lenning
&&
.AVIATION...
For the 00Z TAFs...
Main concern for the evening and overnight hours will cig/vis
trends.
The main area of rain has moved out of the area, but there will
still be some chance for isold shra/isold tsra into the evening.
The main focus for any additional pcpn will be lingering outflow
boundaries and weak mid-level impulses over the area. The most
well-organized outflow boundaries are south of the terminals and
expect the bulk of any pcpn to remain coincident with these
boundaries. However, there are a few weak mid-level impulses
moving across nrn IL that could still bring some isold pcpn. given
the isolated nature of any pcpn, confidence is too low to include
in the TAFs at this time, except for a vcsh mention at RFD/GYY
based on latest radar trends.
With the winds expected to becm lgt/vrbl and continued moist low
levels, in recent rainfall, fog is expected to develop across the
region overnight. Latest model guidance continues to suggest that
the denser and more widespread fog should be west of the Fox
Valley, with RFD/DPA likely to see the lowest vis to 1/2sm or
less. Have gone with a tempo 2sm at ORD/MDW, but there is the
potential for lower vis at these sites as well, though confidence
is lower in the potential for LIFR vis.
&&
.MARINE...
152 pm...A weak area of low pressure will move across the
southern Great Lakes region tonight as a weak area of high
pressure moves across the western Great Lakes region on Wednesday.
Strong low pressure will move across Hudson Bay tonight into
Wednesday morning. A trailing cold front from this low will move
south across the region Wednesday night with generally northerly
or northeasterly winds prevailing into the weekend. cms
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Medford OR
903 PM PDT Tue Aug 7 2018
.DISCUSSION...A minor update this evening to more precisely depict
the inland movement of stratus into Coos and far western Douglas
Counties into Wednesday morning.
Little change to the forecast is expected with the next issuance
early Wednesday morning. The major weather concerns remain
unusually hot temperatures through Thursday, gusty and strong
southerly winds in the Shasta Valley on Thursday (with breezy
southwest winds on the east side), then the region of strongest
southwest to west winds transitioning to east of the Cascades for
Friday with the passage of a dry cold front.
The thickness/visibility of smoke has made slight but noticeable
improvement in much of the Rogue and (to a lesser extent) Klamath
Valleys this evening. The HRRR model seemed to pick up on this,
and shows a slow, gradual deterioration overnight into Wednesday.
This variability in smokiness for the smokier areas...south of
Coos and northern/central Douglas Counties is to be expected while
conditions generally do remain smoky while the current pattern
continues to trend hotter and drier through Thursday.
Please see the previous discussion below for further details of
the seven-day forecast.
&&
.AVIATION...For the 08/00Z TAFs...Over the coastal waters, along the
coast, and coastal valleys...IFR cigs persist from the waters to the
coast and will spread into the coastal valleys tonight. IFR cloud
cover will retreat back to the coast again by Wednesday afternoon.
Over the Umpqua Basin...MVFR cigs are expected to spread inland as
far as Scottsburg tonight. The remainder of the area will remain VFR
through Wednesday.
Over the remainder of the area...Areas of MVFR vsbys and local IFR
vsbys in smoke will persist through Wednesday.
&&
.MARINE...Updated 800 PM PDT Tuesday 07 August 2018...A thermal
trough will persist near the coast with north winds and short period
seas south of Cape Blanco reaching a peak this evening. Conditions
are below small craft advisory levels over most of the area. The
exception will be a small area between Cape Blanco and Gold Beach
from 5 to 10 nm offshore that may see borderline small craft
conditions through this evening. Winds and seas will be lighter
Wednesday through Friday. A front will move onshore Friday then a
thermal trough will strengthen behind the front. Strong north winds
and choppy wind driven seas may develop Saturday afternoon and
continue through Sunday.
&&
.PREV DISCUSSION... /Issued 240 PM PDT Tue Aug 7 2018/
SHORT TERM...An upper level ridge will continue to build over the
region through Wednesday, then remain in place into Thursday.
This will bring hot temperatures to inland areas. Then an upper
trough will move into the Pacific Northwest late Thursday and
Friday. Gusty winds are expected ahead of and with the trough
passage in the afternoon and evening on Thursday and Friday. On
Friday temperatures will lower across inland areas.
Models are in good agreement with the upper ridge building over
the area and bring hot temperatures to inland locations. This is
expected to bring triple digit temperatures to many inland west
side valleys. Model guidance indicates temperatures heating up
into the 106 to 107 range Wednesday and Thursday for Medford.
However with the effects of smoke factored in, expect highs to be
in the 101 to 103 range. Similar temperatures in the lower 100s are
expected in other parts of the Rogue Valley as well as in the
Azalea and Sunny Valley areas, Applegate Valley, Shasta Valley.
Only limited relief is expected overnight for these areas with
temperatures briefly lowering into the mid to upper 60s. Other
inland valleys east of the Cascades, in Northern California and in
the Umpqua Valley are also expected to heat up with highs rising
into the 95 to 100 range.
Meanwhile wildfire smoke will continue to impact inland areas.
Across western valleys in Jackson and Josephine county, expect
continued significant smoke impacts each day due to northwest
daytime winds bringing smoke in to the valleys from area
wildfires. Location east of the Cascades and over Northern
California will see smoke from fires both in Oregon and California
today and Wednesday. On Thursday, expect winds to become gusty
out of the south to southwest with upper level winds also out of
the southwest. This will bring smoke up from wildfires in
California. Of concern, the gusty winds combined with low
humidities may bring increased fire weather concerns on Thursday,
especially to the Shasta Valley where strong winds are possible.
A fire weather watch (RFWMFR) is in effect on Thursday for the
Shasta Valley.
For coastal areas, expect continued areas of low clouds and
patchy fog overnight and in the morning today and Thursday with
partial daytime clearing.
On Friday, as the upper trough moves over the Pacific Northwest, a
dry cold front will move inland. Winds ahead of this front for
areas from the Cascades east are expected to be gusty out of the
southwest with breezy west winds expected across areas west of the
Cascades. This pattern will also bring a cool down with daytime
temperatures lowering 10 degrees into the upper 80s to mid 90s
across inland areas. Along the coast and into the Umpqua, expect
relatively cooler and moister conditions with a marine push of
low clouds expected along the coast and into the Umpqua Valley
Friday night.
LONG TERM...Saturday through Monday...The upper trough will
gradually shift northeast on Saturday then a zonal westerly flow
pattern sets up aloft on Sunday, transitioning to a ridge on
Monday. At the surface, models indicate a thermal trough will
develop along the coast by Sunday and expand north on Monday. This
pattern will result in warming temperatures across inland areas
Sunday into Monday. Offshore flow will bring dry easterly winds to
the coastal ridges. This will also result in partially clearing
skies along the coast with decreased low clouds. With the ridge
remaining in place Monday into Tuesday, will need to monitor if
mid level moisture and shortwaves move up from the south, which
may bring a slight chance for thunderstorms. Models currently show
very weak mid level moisture. So have kept thunderstorms out of
the forecast.
FIRE WEATHER...Updated 200 PM PDT Monday, 6 August 2018...A
warming and drying trend will continue through Thursday, followed by
a dry cold front passing through the area on Friday, bringing
increasing winds to most areas.
The air mass on Wednesday and Thursday is expected be one of the
hottest for this time of year (top 10 percent). That being said, the
thick smoke from the fires will prevent the hottest temperatures
from being realized. A weak thermal trough pattern will deliver
generally light northeasterly nighttime winds to areas of Northern
California and east of the Cascades, as well as upper slopes and
ridges west of the Cascades tonight. Overnight ridgetop humidity
recoveries will gradually worsen and become poor to moderate over
the ridges by Wednesday night (tonight through Wednesday night in
areas east of the Cascades). the latest low level moisture images
are showing a dry layer to the south of us that should push into the
region with 700 mb winds becoming more southerly overnight. Have
lowered ridge RHs tomorrow to somewhat mirror this.
Model guidances suggest a slight increase in winds Wednesday, and
then significant increases on Thursday and Friday. The increasing
southerly general winds will impact areas east of the Cascades and
in Northern California from the Shasta Valley eastward. Other areas,
like the Rogue Valley and other West Side valleys will likely see
enhanced afternoon winds from the typical summertime direction of
northwest, especially on Friday. This increase in winds and dry cold
front passage will definitely represent a significant change in fire
weather environment. With the increased winds and dry weather,
conditions could easily become near critical east of the Cascades as
well as for the Shasta Valley--especially on Friday, but conditions
could also be close on Thursday as well. Have issued a fire
weather watch for the Shasta Valley on Thursday and decided to
headline these conditions in the FWFMFR and FWLMFR for east of the
Cascades. However, could see the possibility of a fire weather watch
on Friday for over eastern areas. This will need to be monitored
with the next couple forecast cycles.
Models continue to show little support for thunderstorms ahead of
the approaching trough on Friday. There is very little moisture per
the latest operational GFS, and many model runs before this one.
Confidence is increasing that the major impact from this trough will
be the windy, hot, and dry conditions, and not thunderstorms. Cooler
conditions on Saturday will follow the frontal passage. -Sven
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory from 11 AM Wednesday to 9 PM PDT Thursday for
ORZ023-024-026.
CA...Fire Weather Watch from Thursday afternoon through Thursday
evening for CAZ281.
Heat Advisory from 11 AM Wednesday to 9 PM PDT Thursday for
CAZ081.
Pacific Coastal Waters...None.
$$
DW/NSK
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1046 PM CDT Tue Aug 7 2018
.UPDATE...
Issued at 1046 PM CDT Tue Aug 7 2018
Updated to include 06Z aviation discussion below.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 301 PM CDT Tue Aug 7 2018
The main short term concerns remain timing of convection into the
evening and again to the east into Wednesday afternoon.
Latest SPC mesoanalysis showing 1000 J/kg MLCAPE and weak surface
boundary working over west central WI. Satellite showing upper
circulation weakening but still evident working very slowly east
over south central MN. Able to regenerate some convection under
the low central. Otherwise, widely scattered convection over
mainly west central WI with some isolated land spout reported up
in Burnett Co region. We`ve also gotten several reports of funnel
clouds in central MN (near the Hector-Hutchinson areas). Convection
follows southwest into east central MN(Chisago and Polk Co Wi).
Mesoanalysis still showing some surface vorticity along the
boundary and enough low level CAPE to continue the landspout
threat a couple more hours. Forecast trend on the SPC meso site
does weaken this by late afternoon. Not certain on overall timing
of ending the PoP chances to the southeast. HRRR trends has been
slowing the movement into west central WI. Will hold onto slight
chance through about 02z for now.
Clouds may linger much of the night to the east, at least high
level clouds. This may limit overall fog threat but still will
likely see some patchy fog where clouds thin/clear the most. Have
included patchy/areas fog over the eastern area late.
Expect temperatures to warm through the 80s Wednesday afternoon
and both he GFS and ECMWF bring down a weak short wave trough
and surface boundary and generate some light QPF from St Croix
River east into WI Wednesday afternoon, Does look pretty unstable
with MUCAPES over 1750 J/kg, best LI`s around minus 7 and bulk
shear around 35 kts off the GFS. DAY2 SPC outlook was updated to
include marginal risk for severe. Will have to monitor timing of
boundary and overall strength of destabilization for that period.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 301 PM CDT Tue Aug 7 2018
Wednesday night through Sunday...A cold front with limited
moisture will drop through the MN/WI region Wednesday night into
Thursday morning and will continue to drift south during the day
Thursday. While this will result in the end of any lingering
showers over interior western Wisconsin Wednesday night followed
by dry weather for Thursday, it will not result in any significant
cooling. Upper level ridging over the southwestern CONUS will take
a NE-SW orientation and spread into the Northern Plains Friday
then into the Upper Mississippi River Valley region over the
weekend. Meanwhile, the surface front to the south will gradually
wash out and dissipate. The net result of the surface and aloft
features will be a continuation of above-normal warm temperatures
through the weekend and dry conditions. Dewpoints will remain in
the low-mid 60s so in peak heating, heat index values will climb
to near 90 each day through the weekend.
Monday through Tuesday...For the early portion of next week, the
upper level ridge will break down to a more zonal pattern while a
cold front slowly approaches from the west. While this will
maintain the warm and humid conditions, this scenario will also
force the inclusion of chance PoPs into the forecast. Not looking
for anything strong but there will be several periods of scattered
showers/thunderstorms going into the mid-August period.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1046 PM CDT Tue Aug 7 2018
Shortwave trough currently moving through South Dakota could bring
some SCT and perhaps briefly BKN VFR clouds across the southern
half of the area Tuesday morning, but otherwise things look to be
mostly clear across most of the area through the period. The
exception looks to be over the east, where some fog could occur
later tonight, and where there is a possibility of some SHRA/TSRA
late Wednesday afternoon or early evening as a shortwave trough
drops southeast from Canada into the area. A few of the CAMs
suggest activity may pop up over northeast Minnesota and northwest
Wisconsin during the mid to late afternoon and potentially move
near KRNH or KEAU thereafter. However, there hasn`t been
consistent agreement on this scenario, and confidence is too low
at this point to include a mention. But, will bear watching in
subsequent forecasts. The fog overnight seems to be somewhat more
likely, particularly at KEAU where there was some rain nearby
today.
KMSP...Will have some southerly winds in the morning hours, but
should generally be below 10 kt, and look to veer more westerly by
afternoon. May also see some SCT-BKN clouds AOA 5k ft late
afternoon or evening depending on what`s able to develop to the
north and drop southeast. For now any of that looks to stay east
of the area, so stayed optimistic and left out any mention.
/OUTLOOK FOR KMSP/
Thursday and Thursday night...VFR. Northeast/north wind 5 kt or
less.
Friday through Saturday...VFR. Variable wind less than 5 kt.
Saturday night...VFR. South wind 5 kt or less.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
UPDATE...
SHORT TERM...DWE
LONG TERM...JPC
AVIATION...
Area Forecast Discussion
National Weather Service San Francisco Bay Area
901 PM PDT Tue Aug 7 2018
.SYNOPSIS...Strong high pressure over the western United States
will maintain warm to hot conditions across inland areas through
the end of the work week. Along the coast temperatures will be
seasonably mild as a shallow marine layer and moderate onshore
flow prevail. Temperatures may be impacted through the week as
wildfire smoke spreads across the region from time to time.
&&
.DISCUSSION...As of 9:00 PM PDT Tuesday...High temperatures today
were as much as 15 degrees cooler compared to Monday. Today`s
cooling was the result of a number of factors including an
increase in the depth of the marine layer and a slight increase in
the strength of onshore flow - both triggered by a weak shortwave
trough moving across northern California. Another contributing
factor to today`s cooling was decreased solar insolation due to a
thick layer of wildfire smoke aloft. Based on the most recent HRRR
smoke model data, smoke will linger across our region at least
into Wednesday. Most smoke is expected to remain aloft, but some
areas will experience smoky conditions near the surface, primarily
in the North Bay.
An upper level ridge dominating the western third of the nation is
forecast to build more strongly over California during the next few
days. This is expected to result in warmer temperatures,
especially inland, through Thursday. However, continued smoky
skies may reduce the amount of expected warming by at least a few
degrees. A deep upper low, currently centered several hundred
miles off the West Coast, is forecast to move to the ENE later in
the week and inland across the Pacific Northwest by late Friday or
Friday night. This is expected to result in 5 to 10 degrees of
cooling inland over the coming weekend.
Hurricane John, currently off the west coast of Mexico, is
forecast to drift to the northwest off the coast of Baja through
the end of the week. The models agree that moisture from John will
be drawn northward by southerly flow aloft and make its way across
portions of our forecast area by Thursday night or Friday. The 12Z
run of the NAM indicated scattered precipitation and possible
thunderstorms across the North Bay on Friday morning. However, the
subsequent 18Z and 00Z runs of the NAM no longer show convective
precipitation over our area. However, the NAM does continue to
show increased mid/upper level moisture and instability across the
Bay Area late Thursday night through Friday which potentially
could mean high-based thunderstorm development. The latest GFS and
ECMWF do not forecast as much mid/upper level moisture and
instability as the NAM and so forecast confidence is not yet high
enough to explicitly add thunderstorm chances to the forecast
late in the week. Thunderstorm potential in our area may not be
limited to Friday. The models indicate mid and upper level
moisture will increase once again by late in the weekend and into
early next week. Will continue to closely monitor this influx of
tropical moisture during the extended forecast period and look for
any potential for lightning (see fire weather discussion below).
&&
.AVIATION...as of 5:20 PM PDT Tuesday...More widespread smoke seen
today with a reduction in slant range visibilities and occasionally
MVFR visibilities tonight through Wednesday. A positive 24 hour
trend in surface dewpoint temperatures with a slightly deeper
marine layer seen on the profiler data, marine layer is near 1,200
feet deep except shallower at approx 500 feet at the Point Sur
profiler. Onshore winds will usher stratus and fog inland tonight
and Wednesday morning. Clearing returning by late Wednesday
morning.
Vicinity of KSFO...VFR with gusty westerly wind this evening. Less
wind tonight and Wednesday morning. IFR cig is forecast 09z-17z.
SFO Bridge Approach...Similar to KSFO
Monterey Bay Terminals...LIFR/IFR cigs return early this evening.
Clearing returning by late Wednesday morning.
&&
.MARINE...As of 8:42 PM PDT Tuesday...Gusty northwesterly winds
will steadily weaken through mid week. Long period southerly swell
will arrive later Thursday originating from Hurricane John off
the Mexico/Baja California coast, swell will mainly affect the
outer coastal waters.
&&
.FIRE WEATHER...As of 8:55 PM PDT Tuesday...The 12z nam showed
some possible t-storms on Friday morning across the North Bay as
tropical moisture moves in from the SSW. Both the 18Z and 00Z NAM
forecast a similar evolution of moisture but are not as bullish
at producing precipitation. Modified Total Totals with the NAM are
greater than 30 across the Bay Area on Friday, and this mid level
instability is paired with a good slug mid level moisture.
However, the GFS and ECMWF are less robust with both moisture and
instability compared to the NAM. Will continue to monitor these
trends over the next day or so for possible impacts to the Bay
Area and points northward (Mendocino Complex). Even wet storms
would be problematic if down strikes occur on dry fuel beds. For
now confidence is not high enough to explicitly put thunderstorms
in forecast. Forecast only includes some low 10 percent POPS as a
starting point.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 3 AM
SCA...Pt Arena to Pt Reyes 0-10 nm
&&
$$
PUBLIC FORECAST: Dykema
AVIATION: Canepa
MARINE: Canepa
FIRE WEATHER: RWW/Dykema
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Area Forecast Discussion
National Weather Service Nashville TN
855 PM CDT Tue Aug 7 2018
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
A few ongoing showers and thunderstorms are ongoing along the KY
border east of I-65, and look to continue eastward. Models are
consistently showing another round of showers and storms moving in
before sunrise associated with the upper shortwave, so adjusted
pops accordingly. It looks like the majority of the rainfall
potential will be just after sunrise through the early afternoon
across the mid state, and lines up pretty well with existing
forecast thinking. The HRRR and NAM do bring in some isolated
convection during the overnight hours earlier than other models,
but overall CAM consensus confines the activity to the northwest
zones before sunrise, and spreading east and south after sunrise.
Other than the usual adjustments to temps and dewpoints to match
up with obs trends, rest of the forecast is on track.
&&
.AVIATION...
00Z TAF DISCUSSION.
VFR. VCSH will affect CKV and possibly CSV early this evening, but
otherwise dry conditions are anticipated until Wednesday morning
when most models show additional scattered showers and storms.
South to west winds are expected through the TAF period.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......Barnwell
AVIATION........Shamburger
Area Forecast Discussion
National Weather Service Portland OR
238 PM PDT Tue Aug 7 2018
.SYNOPSIS...High pressure will maintain warm conditions through
Thursday, along with hazy skies thanks to smoke from California and
sw Oregon. Clouds along the coast and light onshore winds will
maintain cooler conditions for the coast. An upper low will pass to
our north Friday and Saturday for cloudier and cooler weather, and
possibly light rain.
&&
.SHORT TERM...Today through Friday...The main forecast challenge with
the short term forecast is determining how hot the next several days
be east of the coast range. Model guidance and weather pattern
recognition indicates that it will be very hot, but these sources do
not take smoke or haze (from wildfire smoke) into consideration.
Forecasting the thickness of smoke not our expertise, but has the
potential to have a great impact on surface temperatures. The trend
of late is for the haze to be fairly thin or unnoticeable in the
morning and early afternoon and become more noticeable in the late
afternoon and evening (except or the Lane County Cascades where the
haze has been persistent). Satellite imagery shows a really light
haze over the forecast area now with a thicker haze layer over the
Cascades of Lane County slowly moving NNW. The hrrr forecasts this
haze to become more widespread across NW Oregon and likely over the
Willamette Valley late this afternoon and early evening, which
supports the observed trend the past couple of days.
If the haze is thin, and allows for a lot of solar radiation to make
it to the surface, then the modeled 850mb temperatures of 21 to 24
degC would allow the afternoons to peak in the upper 90s to low 100s
Wednesday and Thursday. Otherwise, if haze from smoke is similar to
as it was yesterday (Monday) evening, then the temperatures will
likely be in the mid to upper 90s. Both of these scenarios will
provide hot weather and lead to potential heat stress.And the
nighttime temperature relief will be slow with temperatures
lingering in the 70s until 1 or 2 in the morning. Another adding
factor to the discomfort of this heat is that 700-500mb south winds
will allow for higher dew points, and a muggier feeling to the heat.
This increases the heat index and will allow the temperatures to
feel warmer than they actually are. Will continue the Warnings and
Advisories for heat due to the potential impacts.
Temperatures at the coast will be much cooler as weak onshore flow
and nocturnal marine clouds will keep the afternoon temperatures in
the upper 60s to mid 70s.
An upper low that will linger well offshore the next few days will
approach the coast Thursday and begin to move over the region
Thursday night. This will increase onshore winds in the afternoon and
favor a deeper southwest marine push Thursday night into Friday.
Models indicate instability over the Cascades Thursday afternoon and
evening as upper level divergence ahead of the upper low moves over
the region. Modeled precipitation water values increase to around an
inch at this time too. The increase of mid-level moisture and
instability suggests that afternoon and possibly nocturnal convection
may be possible. Have not added any thunderstorms to the forecast
though as the increasing onshore winds would likely keep any
developing storms at the Cascade crest or east of it. The threat for
Cascade thunderstorms Thursday afternoon and evening is not 0, but
not over 10 percent either. Will re-evaluate this threat tomorrow
and Wednesday as the time period gets in the time range of the higher
resolution models.
The upper level trough and low will move over the region Friday for
cloudier and cooler weather. Light rain is possible for the coast
Friday afternoon and possibly inland Friday night. The interior
temperatures will be closer to the seasonal normals Friday afternoon
(low 80s). ~TJ
.LONG TERM...Friday night through Monday. Light rain is possible
Friday night and Saturday as an upper trough moves over the area. Any
accumulating rain will most likely be over the higher terrain and
north of Salem. High pressure returns to the surface Sunday, but a
weak upper low should maintain some coastal marine clouds and onshore
flow. An upper ridge returns for Monday for less clouds and
afternoon temperatures possibly getting back into the low 90s. ~TJ
&&
.AVIATION...IFR stratus continues along the central Oregon coast
this afternoon, with little change expected through the next 24
hours. Expect that low stratus will again return to the remainder
of the coast and the valleys of the Coast Range late this
evening, with some shallow stratus along the lowest reaches of
the Columbia River as far as KKLS. Across the remainder of the
interior, VFR conditions expected to continue through the TAF
period with an elevated smoke layer at around 8000 feet.
KPDX AND APPROACHES...VFR conditions continue through next 24
hours. Elevated smoke from wildfires will remain at around 8000
feet. Cullen
&&
.MARINE...Weak surface high pressure will remain near or over
the waters for the first half of the week. The surface pressure
gradient will strengthen today as the low pressure inland
intensifies and the surface high tilts inland across southern
Washington, with low-end advisory strength gusts across the
northern zones, but only occasional gusts to this strength south
of Cascade Head. A large low pressure system currently spinning
near 140W will eventually move into the Pacific Northwest Friday
or Saturday, bringing a time of gusty southerly winds to the
waters. Seas will remain 4 to 6 feet through most of the week.
Cullen
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning until 11 PM PDT Thursday for Central
Columbia River Gorge-Central Willamette Valley-Greater
Portland Metro Area-Upper Hood River Valley-Western
Columbia River Gorge.
Heat Advisory until 11 PM PDT Thursday for Cascade Foothills in
Lane County-Lower Columbia-Northern Oregon Cascade
Foothills-South Willamette Valley.
WA...Excessive Heat Warning until 11 PM PDT Thursday for Central
Columbia River Gorge-Greater Vancouver Area-Western
Columbia River Gorge.
Heat Advisory until 11 PM PDT Thursday for I-5 Corridor in
Cowlitz County-South Washington Cascade Foothills-South
Washington Cascades.
PZ...Small Craft Advisory for winds until 9 PM PDT this evening for
Coastal Waters from Cape Shoalwater WA to Cascade Head OR
out 60 NM.
&&
$$
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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. This area is
commonly referred to as the CWA or forecast area.
Area Forecast Discussion
National Weather Service Pueblo CO
913 PM MDT Tue Aug 7 2018
.UPDATE...
Issued at 908 PM MDT Tue Aug 7 2018
Updated the fcst to expire severe weather watch and adjust flash
flood watch.
As posted on NWS CHAT and Twitter, I am still concerned isolated
severe storms will affect the region this evening and tonight. As
I write, convection was beginning to initiate over several
locations of the plains. This convection is likely elevated, but
the shear is still quite strong (40-50 knts) and the MLCAPE
values are still rather high (1500-2500) per SPC mesoanalysis
page. Locally heavy rain is still possible, with best chances
southof US50. /Hodanish
UPDATE Issued at 647 PM MDT Tue Aug 7 2018
Short range hi res guidance is having a difficult time handling
the current wx situation over the region at this time. Except for
a TSRA over Custer county, no other significant convection was
noted over the region at 645 pm. Guidance insist that strong
convection should be occurring over parts of the plains attm.
What I believe is the issue is a short wave ridge is moving over
SE Colo attm and this is suppressing convection. A rather strong
short wave is fcst to begin affecting the region late this evening
and tonight, and we may have a better chance of storms over the
plains late this evening/overnite. For now have trended POPS
downward but I am keeping the convective/flooding hilites in
place. Any small storm over a burn scar could cause flash
flooding. /Hodanish
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 203 PM MDT Tue Aug 7 2018
Forecast models continue to show showers/tstms over the eastern
mtns and along the I-25 corridor early this evening, and then as
an upper level disturbance moves southeast acrs the eastern
portions of the state, the storms will spread acrs the plains thru
the late evening. The western mtns and high valleys are still
expected to see a lower risk of showers/tstms this evening.
With abundant moisture over the area today, heavy rain remains a
threat thru the evening and into the late night hours in some
locations, and could present a flash flood risk for urban areas,
burn scars over eastern areas, and in areas where heavy rain fell
yesterday. There also continues to be the risk of a few severe
storms over the southeast plains this evening and a Severe
Thunderstorm Watch is in effect until 9 PM MDT.
The NAM shows some lingering precip over the far southeast plains
into the late night/early morning hours. The GFS does the same, but
also shows some light lingering precip over and near some of the
eastern mtns. The HRRR shows some light linger precip over Baca
county thru about 09-10Z, and dry conditions elsewhere. Have
decided to carry some low POPs thru about 11Z over mainly the far
southeast plains.
There will still be ample moisture over the area on Wed. It looks
like storms will initiate around Noon over the eastern mtns and move
off over portions of the I-25 corridor. The storms are not expected
to spread acrs the southeast plains until the evening hours.
Conditions will again be favorable for a few severe storms over the
plains.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 203 PM MDT Tue Aug 7 2018
There is continued low spreads among the ensemble members through
the extended, with some spread as we get into Monday and Tuesday
next week. Operational solutions remain similar leading to higher
confidence through at least the weekend.
Wednesday night into Thursday...high pressure will remain centered
over Nevada with disturbances rotating south across Colorado
Wednesday night into Thursday. Expect widespread showers and
thunderstorms across the Eastern Mountains, spreading east into the
I-25 corridor, then south and east overnight. Locally heavy
rainfall will remain possible with flash flooding on area burn
scars, urban areas and locations that have seen heavy rains the past
couple of days. In addition, one or two storms could become strong
to severe as they move across the Plains with large hail and
damaging winds the main threats. This activity will shift south into
New Mexico late Wednesday night into Thursday morning. Models are
slightly different on Thursday. The NAM has one last upper wave
rotating around the high to the west, dropping south across
Colorado. The GFS does not, confining shower and thunderstorm
activity to the Continental Divide. Given the uncertainty, will
continue with POPs across the mountain areas, spreading east into
the I-25 corridor through the evening hours. Expect this activity to
shift southward into New Mexico by late evening.
Friday into Monday...the high pressure over the west is forecast to
shift east and north with northeasterly flow setting up across the
region. Expect showers and thunderstorms to become more diurnally
and terrain driven Friday and through the weekend. Initial
development will occur over the mountains, primarily along the
Continental Divide. Activity will then spread southwest into New
Mexico during the evening or dissipate after sunset. Locally heavy
rainfall will remain possible, especially over the San Juan range.
Tuesday...there are slight differences in the operational solutions.
The GFS shifts the high pressure westward, while an upper
disturbances drops southeast across Colorado with a return to
widespread showers and thunderstorms across the area. The ECMWF has
a similar upper disturbance, but much further north. It also tries
to bring a disturbance up from the south which the GFS does not
have. Mozley
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 203 PM MDT Tue Aug 7 2018
KCOS and KPUB could see thunderstorms in the vicinity thru the
evening, with heavy rain being a threat. Some hail may also occur
with stronger storms. By the late night hours, the threat of storms
should end, but there is the possibility of some low stratus
developing.
KALS is expected to have VFR conditions thru the 24 hrs period.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until midnight MDT tonight for COZ072>075-
078>080-087-088-094.
&&
$$
UPDATE...HODANISH
SHORT TERM...28
LONG TERM...MOZLEY
AVIATION...28