Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/01/18
Area Forecast Discussion
National Weather Service Denver/Boulder CO
722 PM MDT Tue Jul 31 2018
.UPDATE...
Issued at 720 PM MDT Tue Jul 31 2018
Clouds moving in from the NNW over the foothills and from Wyoming
over the next few hours. This will slowly bring in a FEW to SCT
deck for the morning and into the afternoon. Maintained current
temp forecast but added some patchy smoke to the forecast for
areas of Summit and Grand county with increased smoke produced by
the Silvercreek fire. I suspect this smoke to continue into the
morning hours and tomorrow if intensity continues.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 332 PM MDT Tue Jul 31 2018
It will be a quiet night tonight with low temperatures reaching a
few degrees below average. Some upper level clouds may develop off
the higher mountains similar to what is occurring across the
western part of the state. Winds are gusting up to 25 mph out of
the north on the east side of Denver right now and these winds
will begin to settle down around sunset. Otherwise, there are no
POPs in the forecast through 12z Wednesday.
A small vort max will track southeastward out of Wyoming tomorrow
afternoon reaching our CWA by about midday. This feature, along
with some weak instability, may be enough to create a few showers
and thunderstorms that begin over the mountains and foothills and
move southeastward onto the urban corridor and plains. With
low relative humidities in the low levels and forecast DCAPE
values near 1000 J/kg, these showers and storms will be capable of
producing winds up to 35-45mph. However, the HRRR smoke model
suggests high values of vertically integrated smoke to move over
our CWA by mid morning and this may limit the already low
instability in the area. Therefore, there is low confidence in the
strength of the thunderstorms and associated wind gusts. With this
smoke, skies may be hazy tomorrow as high temperatures will be
around average.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 332 PM MDT Tue Jul 31 2018
As the calendar turns the page to August we will continue with the
mid-summer weather pattern that brings warm temperatures and a
chance of afternoon and evening thunderstorms to northeastern
Colorado. Early on, the center of the upper high will be centered
over Arizona and the northwest corner of Mexico with weak
northwesterly flow over northern Colorado. Over the last couple
days, satellite imagery has shown an increase in convective
activity over the mountains of northwest Mexico. The forecast
models are showing the results this as elevated specific humidity
levels across the desert southwest. This moisture will make its
way over Colorado as the weak west-northwest flow continues. On
Friday, the flow over northern Colorado becomes more westerly and
weakens as the upper high shifts westward toward the Pacific. A
weak upper disturbance embedded in the flow is forecast to cross
over the state Friday evening. This will drive a round of showers
from the mountains out onto the plains. Locally heavy rain will be
possible with these showers as model soundings indicate that
precipitable water values in the Denver area will be up near 1.00
inches. Medium range models indicate that this will be the day
with the most widespread precipitation over the next week.
The rest of the forecast period should see showers and
thunderstorms confined mainly to the mountains. Each evening may
see a few thunderstorms come out over the adjacent plains. The
ECMWF shows the next upper level ridge will develop over Colorado
and New Mexico by Monday morning and then remaining over the
southern plains through the week. If the center of the upper
circulation moves more eastward, this will increase the chances
for moist southwest flow to begin transporting monsoonal moisture
into the state. This would lead to an eventual increase in shower
activity and intensity. For the time being will stick with the
afternoon shower activity over the mountains through the middle of
the week with plains locations being warmer and a little drier.
Highs on the plains should make it into the lower 90s by Friday
and then remain at that level through Wednesday.
&&
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 332 PM MDT Tue Jul 31 2018
VFR conditions will continue through tomorrow evening. Winds have
increased this afternoon out of the north at DEN and APA and will
sustain these speeds or slightly less until roughly around sunset.
Overnight, winds will tend toward drainage. A shortwave moving
through northern Colorado tomorrow may provide enough forcing to
create showers and storms that move off the mountains. Some of
these showers and storms could produce gusty and variable winds up
to 40 knots with the next chance between 20-00Z.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Bowen
SHORT TERM...Danielson
LONG TERM...Dankers
AVIATION...Danielson
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
659 PM EDT Tue Jul 31 2018
.AVIATION...
Bands of showers and an occasional thundestorms can be expected into
the overnight with a steady expansion of coverage in the 02z-04z
time frame as low pressure lifts north-northeast into the area. Best
coverage of rain will focus from KPTK SSE with best low level FGEN.
Further NNW, there will be a sharp decline in coverage/intensity of
activity from KFNT to KMBS. VFR to spotty MVFR cigs will drop to
MVFR/IFR late tonight as this low skirts the area with a return to
lower VFR on Wednesday as drier westerly flow develops in the wake
of this system.
For DTW...spotty showers early in the forecast will increase in
coverage/intensity after 02z as low pressure lifts into the area. A
few thunderstorms should also be embedded with this activity. Cigs
will trend from lower VFR to MVFR with this convection and perhaps
drop to IFR for a time late tonight/early Wednesday before lifting
midday Wednesday.
.DTW THRESHOLD PROBABILITIES...
* High for cigs aob 5kft into Wednesday morning, lower by midday.
* Moderate for occasional tstorms in KDTW airspace late this
evening into tonight
&&
.PREV DISCUSSION...
Issued at 548 PM EDT Tue Jul 31 2018
UPDATE...
FLASH FLOOD WATCH NOW IN EFFECT FOR DETROIT METRO AND OUTLYING AREAS
THROUGH TONIGHT...
As of 545 PM EDT...Have continued to monitor the latest trends in
model guidance with respect to the heavy rainfall potential this
evening and into tonight across portions of southeast Michigan. The
latest runs of the HRRR and 18z NAM3km have only added further
confidence to the heavy rainfall solution already proposed by 12z
runs of the SPC 4km WRF and Hi-res ARW.
As a result, have issued a short-fused Flash Flood Watch for Wayne,
Oakland, Macomb, St. Clair, Washtenaw, Monroe, and Lenawee counties
through 4am tonight. Bands of heavy rainfall with embedded
thunderstorms, associated with a compact area of low pressure
tracking northeast into southwestern Ontario later tonight, are
expected to primarily impact these areas, with a particular concern
for the greater Detroit metro area. Timing of heaviest rainfall looks
to occur between roughly 8pm and midnight. Rainfall rates during
this time will be heavy to intense at times where banding persists
for the longest, with rainfall totals of 1-3 inches possible in as
little as less than 3 hours, with the potential for localized amounts
of 3-5 inches.
These rainfall rates and totals will pose a heightened risk for flash
flooding in the Detroit metro and outlying urban areas, as well as
susceptible low lying and poor drainage areas in the watch area.
Additionally, rapid river rises will also be possible and may further
exacerbate the flooding threat.
Previous discussion highlights the meteorological setup in greater
detail and is below.
PREV DISCUSSION...
Issued at 400 PM EDT Tue Jul 31 2018
DISCUSSION...
Focus for this forecast will be the heavy rainfall potential across
portions of southeast Michigan this evening and into tonight. Upper
low over eastern MO and western IL will drive a surface low pressure
northward from the Ohio River Valley this afternoon and through
portions of southeast Michigan. Trends have been towards a more
amplified wave with increasing precipitation moving from south to
north as a shortwave rotates around the low. The center of the
surface low looks to track up through the Detroit and St Clair
Rivers. This will place southeast Michigan in an area of deformation
and a favorable location for likely precipitation. Precipitable
Water values will be reach around 1.75 inches, which is in the upper
10 percent of climatology and will provide some confidence for heavy
rainfall potential. Deformation forcing and the presence of some
instability will allow for pockets of higher rain rates with
embedded thunder as system lifts northward. Afternoon precipitation
will make way for heavier precipitation potential by the evening as
stronger forcing arrives. Timing for the heaviest rainfall potential
will begin around 7-8 pm for Detroit Metro and areas along the I-
94/I-96 corridors then slowly work its way northward towards the
Thumb by midnight. There will be lingering precipitation chances
with heavy rainfall potential overnight as system lifts north.
The general higher rainfall amounts will reside roughly along and
southeast of an Howell to Bad Axe line, but latest hi-res guidance
is leaning towards Wayne, Oakland, Macomb and St. Clair Counties
seeing some of the higher rainfall amounts where the greatest
deformation forcing may line up. Main concern is for urban flooding
if heavier precipitation bands set up over any of urban areas, as 1
inch per hour rainfall rate or greater will be possible.
The upper level trough will begin to weaken throughout tomorrow with
the trough axis remaining west of the area and good moisture
remaining in place. This will keep low chances for showers and
thunderstorms in the forecast as the initial wave shears within the
troughing pattern over Michigan. Lack of shear will keep activity
unorganized and coverage should be scattered. Temperatures tomorrow
in the upper 70s and low 80s with a brief break in precipitation
chances tomorrow night.
Troughing pattern persisting over the region will again bring some
precipitation changes for Thursday, but this will reside mostly over
central Michigan where the better forcing will be. At the moment,
areas affected by rain chances will be towards the northern CWA
across the Tri-Cities. An slight increase in instability and lapse
rates will keep potential for thunderstorms in the forecast.
Temperatures will increase slightly with most areas reaching into
the low to mid 80s.
Upper-level troughing will continue to remain in place across the
Great Lakes heading into Friday. Dewpoints remaining in the 60s will
promote the potential for diurnally-driven isolated to widely
scattered showers and thunderstorms. Increased downstream ridging
over the Mid-Atlantic region will lead to drier and more capped
conditions for much of the weekend as 700 hPa temps increase into
the 8-10 C range. Weather will then become increasingly unsettled
early next week as potent northern stream energy ejects out of the
northern Plains towards the Great Lakes with scattered to
potentially numerous showers and thunderstorms.
Hot and humid conditions will persist through much of the long term
period with temperatures near to slightly above average and surface
dewpoints well into the 60s to near 70.
MARINE...
Light to moderate wind through the week with no significant events
on the horizon. Low chance for thunderstorms will exist in the
nearshore zones through the end of the week.
HYDROLOGY...
Bands of heavy rainfall with embedded thunderstorms are likely this
evening and into tonight. Confidence has increased that the greatest
threat for heavy rainfall will occur across the Detroit metro and
outlying areas. A Flash Flood Watch has been issued for Wayne,
Oakland, Washtenaw, Macomb, St. Clair, Lenawee, and Monroe counties
through 4am tonight. The potential exists for rainfall totals of 1-3
inches in the watch area, with localized areas of 3-5 inches
possible where banding persists the longest. Much of this rain may
fall in less than a 3 hour period.
These rainfall rates and totals will pose a heightened risk for
flash flooding in the Detroit metro and outlying urban areas, as
well as susceptible low lying and poor drainage areas in the watch
area. Additionally, rapid river rises will also be possible and may
further exacerbate the flooding threat. The heavy rain threat will
be highest between 8pm this evening through midnight tonight.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Flash Flood Watch until 4 AM EDT Wednesday for MIZ063-069-070-075-
076-082-083.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....DG
UPDATE.......IRL
DISCUSSION...AA/IRL/OV
MARINE.......JVC
HYDROLOGY....JVC/IRL
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Forks ND
705 PM CDT Tue Jul 31 2018
.UPDATE...
Issued at 700 PM CDT Tue Jul 31 2018
Cold front located from NW of Bemidji to near Mahnomen to just
NW of Fargo to Lisbon. Just enough shear aloft and upper level
energy for storms to form the last 2 hours in Beltrami county on
the SW edge of a line of storms that extended into Ontario. In the
past 15 min have noticed CU field is growing via vsbl satellite
pic along the front to north of Fargo and we are starting to see
t-storms get going. SPC analysis shows surface CIN increasing
already in SE ND with little CIN yet in MN fcst area. The one
storm NW of Bemidji became supercellular with large hail but as
line of broken storms form it is not clear how strong the new
storms will get as the environment become unfavorable for
intensification soon. Scattered light rain showers Grafton/Grand
Forks area moving slowly east. Updated pops to reflect current
conditions and fcst idea of a risk of a few storms thru the night
along the front into WC MN, but not severe.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 253 PM CDT Tue Jul 31 2018
Convection chances and strength tonight will be the main issue for
the period.
Northwesterly flow aloft with a digging shortwave trough has
helped push a cold front into our northern counties. As of 19Z,
the front had passed through DVL and GAF over to BDE. So far the
CAPE along the front has been very limited, and only a few rain
showers have been moving into northwestern MN. SPC meso analysis
has the northern counties near the front well capped. However,
ML CAPE values are in the 1000-1500 J/kg across parts of
southeastern ND. Several of the high res runs such as the HRRR and
a couple of HopWRF members have storms blossoming along the front
between 22 and 00Z as the front pushes south into the area of high
instability. The instability area is pretty narrow, and deep layer
bulk shear is rather marginal with 25 to 30 kts. However, shear is
more than we have seen lately, and some high based thunderstorms
with the potential for large hail and damaging winds are not out
of the question for a few hours this evening. The main band of
thunderstorms will push southeastward by 03Z, although several of
the CAMs have additional activity developing behind the surface
cold front. Will continue to keep some POPs going for much of the
night into tomorrow morning.
High pressure will be building in behind the cold front tomorrow,
with north winds bringing continued cold air advection for much of
the day. Temps should stay mainly in the low 70s, although some
upper 60s will be possible in the southeast with clouds hanging
around a bit longer.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 253 PM CDT Tue Jul 31 2018
Northwest flow aloft prevails Wednesday night in the wake of a
shortwave trough. Surface flow shifts as we head into Thursday
morning, becoming southerly and allowing moisture to advect into the
region. The surface to 850mb flow continues to increase through the
day on Thursday with enhanced long-fetch moisture flow into the
region. A shortwave ridge will be building into the area at the same
time, thus allowing temperatures to climb into the mid to upper 80s
on Thursday and into the upper 80s to lower 90s on Friday with
increasing humidity.
A relatively weak cold front will push across the CWA on Friday with
a reinforcing cold front Saturday evening. Given the increased
moisture in place, instability will be elevated ahead of the front,
with CAPE in the 3000 to 4500 J/Kg range. This, combined with bulk
shear of 30 to 50 knots, will be favorable for severe thunderstorm
development Friday afternoon with potentially strong thunderstorms
on Saturday.
For Sunday and Monday, several weak shortwaves will move through the
area along northwest flow aloft. This will allow several
opportunities for scattered showers and thunderstorms each afternoon
and evening.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 700 PM CDT Tue Jul 31 2018
MVFR stratocu deck in S Manitoba extends into far NE ND at
23z/00z. Unsure how far south it makes it though as the main 500
mb cold pool is moving more east-southeast and models indicate 850
mb moisture weakens as it drops south. Better chc of MVFR cigs in
to NW MN tonight into Wed AM.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Riddle
SHORT TERM...JR
LONG TERM...Lynch
AVIATION...Riddle
Area Forecast Discussion
National Weather Service Grand Junction CO
240 PM MDT Tue Jul 31 2018
.SHORT TERM...(Tonight through Wednesday night)
Issued at 240 PM MDT Tue Jul 31 2018
With high pressure sitting to the west, the western slope is
sitting on the eastern periphery of the high with a drier north to
northwest flow overhead. There is no shower or thunderstorm
development yet this afternoon with a few cumulus clouds forming
over the southern ridges. Do not anticipate much in the way of
precipitation due to the more stable atmosphere present today,
helping to suppress the cumulus growth. A bit more cloud cover is
anticipated tonight with an increase in high level moisture, so
not expecting temperatures to be quite as cool as they were this
morning.
The morning started off a bit smokey as smoke from the wildfires
in California is making its way around the high pressure and down
into our CWA for widespread hazy and smokey skies. The several
wildfires burning across our state are allowing for localized
heavier smoke nearby, as seen on radar and satellite this
afternoon. The HRRR smoke model shows this trend continuing
through at least Wednesday night/Thursday morning, so kept smoke
in the forecast through that period. Wednesday will be a
transitional day as the high pressure begins slowly shifting
eastward, allowing for a little more moisture to infiltrate from
the west. Precipitable water (PW) values rise towards 0.75 inches
across eastern Utah and extreme western Colorado, which will
result in isolated to scattered thunderstorms over the higher
terrain Wednesday afternoon. Storms are expected to be high based
with gusty outflow winds and lightning the main concerns. A weak
shortwave looks to rotate around the periphery of this high,
which does remain to the west, but it seems that this shortwave
will impact locations more downstream over the Front Range as it
interacts with better moisture. Overall though, anticipating a
mostly dry, smokey and hot day. Afternoon temperatures overall
have been trending warmer than guidance in this type of regime, so
inched those numbers a bit above statistical guidance.
.LONG TERM...(Thursday through Tuesday)
Issued at 240 PM MDT Tue Jul 31 2018
The high pressure ridge will begin a more eastward shift on
Thursday as a trough pushes into the Pacific Northwest, allowing
the flow to lay over to the west. This will also advect in better
moisture as PW rises above 0.75 towards an inch near the Four
Corners and eastern Utah. Anticipating a dry start to Thursday as
the better moisture and associated stronger shortwave do not
arrive until Thursday evening. This will carryover into Friday,
which is looking like the better day in terms of thunderstorm
chances and coverage, as well as better moisture, with PW values
above an inch across portions of eastern Utah and western
Colorado. The regime will transition on Thursday from drier, high
based thunderstorms towards better chance of heavy rainers heading
into Friday. The valleys even look to be impacted late Thursday
into Friday as this better moisture push is supported by a more
robust shortwave and better upper level support. Due to the heavy
rain potential increasing for Friday, future shifts will have to
look at potential for localized flash flooding on any recent burn
scars. This is still a few days out so models can change, but
something to keep in mind. Temperatures will be hot on Thursday
and a bit cooler Friday due to increased clouds and showers. Still
trended above guidance as periods of sun still expected to heat
things up despite the increase, but it will not feel as noticeably
hot.
Confidence decreases this weekend into early next week as the
models become out of phase with each other. Expecting enough
residual moisture to hang around this weekend for afternoon storms
focused over the higher terrain and drifting into some valleys
late in the day with the high shifting a bit eastward but still
having its influence over our region. An embedded shortwave looks
to move through the flow late Sunday, for another potential uptick
in storm activity through the evening. By early next week, the GFS
is now indicating the high pressure building back to the west over
the Great Basin, bringing much drier air into the region from the
north-northwest which is quite the polar opposite from the model
runs 24 hours ago. The EC, however, is still holding onto the
ridge placement east of the divide with a decent continued push of
moisture from the southwest. The trend so far this summer has
been to shift the high back west after a decent moisture push so
trending towards the drier forecast for next week, until models
come into better agreement. Temperatures are also anticipated to
make a rebound late this weekend into next week due to the drier
trend.
&&
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 109 PM MDT Tue Jul 31 2018
Drier air on northerly flow will bring VFR conditions to the
region over the next 24 hours. Visibility may be impacted by smoke
that settles into the valleys with possible MVFR conditions in
isolated places. Will continue to monitor this impact.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...MDA
LONG TERM...MDA
AVIATION...TGJT
Area Forecast Discussion
National Weather Service Wilmington NC
908 PM EDT Tue Jul 31 2018
.SYNOPSIS...
Deep tropical moisture will shift inland through mid-week as
ridge builds westward from the Atlantic. This will push most
active weather farther inland with a return to more localized
shower and thunderstorms, especially along the coast. The trend
toward more localized thunderstorm activity will continue into
early next week as high pressure takes residence over the
Carolinas.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 910 PM Tuesday...well the big change is GOES-East water
vapor channels is showing the atlantic ridge building westward.
This is seen from the dry air moving in on all three layers of
the water vapor. The precipitable at MHX fell from 2.3" to 1.96"
in the past 12 hours.
The 18 UTC run of the GFS is showing the relatively drier air
shifting over the area but is a tad to slow shifting the dry air
into the area.
The lower levels are still very moist and the southerly flow
continues over the forecast area. The HRRR 00 UTC continue to
show shower developing overnight along the coast especially
after midnight.
With the drier air expecting the rainfall intensity to be less
tonight and early in the morning than the last few days.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
As of 300 PM Tuesday...A subtle change in the pattern is forecast
this period as ridge of high pressure sitting offshore will ridge
more significantly to the west. This will bring a drop in PWAT as
well as a reduction in convective potential, finally. That being
said, the period is not forecast to be dry, but the best rain
chances and heaviest QPF should shift westward into the central and
western Carolinas. Continued warm and humid air on deep southerly
flow will maintain instability and a good chance for tstms, but in a
more typical summertime diurnal fashion, although i-95 counties will
likely see widespread convection lingering into the night thanks to
deeper moisture there. PWATs will feature a reverse gradient from
many of the past several days, with lower values, around 1.7 inches
near the coast, rising to 2.1 inches inland. This supports still the
potential for heavy rainfall and some training of tstms, especially
across the Pee Dee on Thursday, with nocturnal decrease in coverage
and intensity expected both nights. Highs will climb into the
mid/upper 80s on Thursday, warmest in the middle part of the CWA
which will be both away from ocean influence and experience less
cloud cover than further west. Mins will drop into the low and mid
70s both nights as the muggy southerly flow persists.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 300 PM Tuesday...This period should finally see a return of
more seasonal weather as a building ridge aloft limits shower and
thunderstorm activity to a scattered nature more typical of summer
by Saturday through Tuesday. On Friday, an upper low passing by to
the east will enhance shower and thunderstorm chances. Overall,
temperatures will be near normal through the period with maximums in
the upper 80s to lower 90s and lows in the low to mid 70s.
&&
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
As of 00Z...it seems like a week but for now the area
and all TAF sites are free of showers and thunderstorms.
The mid-level water vapor imagery shows dry air has moved
over the area has curtail the convection for this evening.
The HRRR is showing convection forming again along the coast
around 04 UTC so will bring in the mention of VCSH to the
coastal TAFs of KILM, KMYR, and KCRE. VFR conditions are
expected overnight with a hint of MVFR visibility restrictions
from fog.
Introduced PROB30 for inland sites mainly after 16 UTC for
thunderstorms as the deeper moisture will be available.
Extended Outlook...MVFR/IFR from scattered to numerous SHRA/TSRA
each afternoon and evening across all sites through Friday.
Lesser chances for showers and storms over the weekend.
&&
.MARINE...
NEAR TERM /THROUGH WEDNESDAY/...
As of 910 PM Tuesday...southerly winds of 15 knots continue to
blow around the western periphery of the Atlantic high
pressure. The seas currently are 4.6 feet at Frying Pan Shoals
light tower.
The seas should be slowly weakening through the night and the
exercise caution maybe dropped overnight.
SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 300 PM Tuesday...High pressure offshore will gradually ridge
westward into the coastal waters, slowly causing the gradient to
ease. Southerly winds will persist through the period, with speeds
of 15-20 kts early, falling to 10-15 kts Thursday night. Wave
heights may fall a bit through Thursday night as the winds ease
causing the wind-wave component to relax, but this wind wave
combined with a persistent 8 sec 2-3 ft SE swell will keep
significant seas at 3-4 ft.
LONG TERM /FRIDAY THROUGH SUNDAY/...
As of 300 PM Tuesday...S winds of 10 to 15 KT Fri will diminish to
about 10 KT for Saturday and Sunday as they become more
southwesterly. Seas of 3 to 4 FT Friday will subside to 2 FT by
Sunday. Chances for showers and storms with locally higher winds and
seas remain through the period. However, rain chances over the
water should be higher overnight than during the day as is more
typical of summer than conditions have been of late.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Beach Hazards Statement from 6 AM EDT Wednesday through
Wednesday evening for SCZ054-056.
NC...Beach Hazards Statement from 6 AM EDT Wednesday through
Wednesday evening for NCZ106-108.
MARINE...None.
&&
$$
NEAR TERM...RH
SHORT TERM...JDW
LONG TERM...RAN
AVIATION...RH
Area Forecast Discussion
National Weather Service North Platte NE
639 PM CDT Tue Jul 31 2018
.SHORT TERM...(This evening through Wednesday)
Issued at 322 PM CDT Tue Jul 31 2018
The RAP indicates dry air will remain across western and north
central Nebraska tonight with very little return moisture and high
pressure across KS. This should support another night of radiational
cooling. Southwest winds will probably limit the potential for
moisture pooling and fog formation in the valleys. The guidance
blend plus bias correction suggests lows in the 50s.
A back door cold front will drop through ncntl Nebraska Wednesday.
The model consensus suggests isolated afternoon showers and
thunderstorms across the Sandhills. Only the NAM12 and NAMnest
develop appreciable convection; the HREF is dry and the NMM is very
sparse developing just two showers.
There is also a disturbance across the Bitterroots in Idaho this
afternoon that will be dropping through the Panhandle and swrn
Nebraska. The NAM12 suggests and isolated chance but this
disturbance might track too far west to affect the Panhandle so
just an isolated chance is in place for the Sandhills Wednesday
afternoon.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 322 PM CDT Tue Jul 31 2018
Warm air will continue build into western and north central Nebraska
this week and remain in place over the weekend and beyond. This is
in response to a long wave trof developing off the West Coast which
will drive hot desert air into the Great Plains. Temperatures aloft
will return to seasonable levels across Nebraska with -5C to -7C at
500mb and 12C-14C at 700mb. The latest model consensus continues to
suggest highs in the upper 80s to mid 90s with dew points in the 50s
and 60s.
Chance thunderstorm POPs are in place Friday afternoon through
Sunday night, mainly in the evening and at night. Dry weather is
expected Monday and Tuesday. Precipitable water peaks Friday night
between 1.5 and 1.75 inches with the passage of a weak short wave
trof. Rain chances Saturday night appear to be directed more across
the Dakotas and MN where the better forcing will be located. Sunday
night is more interesting with the ECM and Canadian model favoring
SD for storm development and the GFS and GEF models favoring
northern Nebraska. This will be the one to watch as winds aloft at
h500mb increase to 40-50kt supporting strong to perhaps severe storm
development. Ordinary storm development would be more likely Friday
and Saturday night with weak winds aloft.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 637 PM CDT Tue Jul 31 2018
VFR conditions will prevail through Wednesday evening. Winds will
remain fairly light and variable through tonight. A frontal
boundary will move across north central Nebraska switching the
winds to the north northeast near 10 knots for Wednesday.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Gomez
Area Forecast Discussion
National Weather Service Louisville KY
802 PM EDT Tue Jul 31 2018
...Updated Aviation Discussion...
.Forecast Update...
Issued at 640 PM EDT Tue Jul 31 2018
Latest HRRR and data from the 12Z HREF continue to argue for a sharp
increase in rain chances east of the I-65 corridor later this
evening. By daybreak, the 12Z ARW and 18Z NAM were showing a
secondary band right along I-65 forming. Will have to watch for
training of cells in this area, where local peak rainfall totals of
2-3 inches are not out of the question, similar to this morning. One-
(Six-) hour flash flood guidance is still above 2 (3) inches in the
Lake Cumberland area, so they should be able to handle it, assuming
it comes spread out. Have blended the forecast toward the latest
guidance and will send out new products with only minor tweaks
shortly.
&&
.Short Term...(This evening through Wednesday)
Issued at 342 pM EDT Tue Jul 31 2018
Lower level dry slot and entrainment limiting new convection going
for the rest of this afternoon and into this evening. However, the
12z ECMWF/CMC (Canadian)/NAM guidance suggest that the lower rain
chances will be short-lived overnight, as the trough axis/low
sharpens from Lake Michigan down through the Lower Mississippi
Valley. This will advect in deeper layer moisture and channeled
vorticity over the southeast half of the WFO LMK forecast area
(generally east of Bowling Green to Shelbyville line) after
midnight. With the anticipated sharper gradient of lift, enhanced
PoPs to likely category centered from Cynthia to Campbellsville
and Glasgow overnight.
With the upper trough expected to move little eastward during the
day on Wednesday, kept chance or better PoPs over the eastern
third of the WFO LMK forecast area. Made little change to
temperatures into Wednesday, except for raising temperatures
slightly in the western third of the forecast area where lower
rain chances are anticipated.
.Long Term...(Wednesday night through Tuesday)
Issued at 342 pM EDT Mon Jul 30 2018
There will continue to be general ridge (southwest U.S.), trough
(central U.S. / Mississippi Valley), ridge (eastern U.S. seaboard)
blocking pattern in place through at least Saturday with mainly
diurnal chances for showers and thunderstorms from Thursday
through Saturday. The best chances for rain will be centered east
of a Louisville to Bowling Green line onward to the remainder of
central Kentucky. At this time, the ECMWF/Canadian/NAM are
somewhat consistent with the persistence of this blocking pattern,
so have moderate forecast confidence with the PoP/Weather.
Beyond Saturday, forecast confidence is lower, as the blocking
pattern shifts to a split flow with ridging expanding across the
southern U.S. and the WFO LMK forecast area moving toward a
diffluent pattern ahead of a faster zonal flow in the upper
Midwest. Kept close to the regionally initialized model blend for
general weather conditions. Temperatures outside rain areas should
return closer to normals for this time of year early next week,
especially in the western half of central Kentucky and southern
Indiana.
&&
.Aviation...(00Z TAF Issuance)
Issued at 800 PM EDT Tue Jul 31 2018
Low level clouds have scattered out this evening with radar mostly
quiet this hour. Plenty of high cloud cover will continue to stream
overhead, but a bit more clearing was noted over southwest Indiana.
Fog may become an issue overnight at HNB, especially after 08z. Went
with 3SM for now, but some potential for IFR fog as well.
Expect more BKN/OVC cloud cover for the other three TAF sites. After
03z, a round of showers and thunderstorms is expected to lift NNE
out of Tennessee, roughly on a Glasgow to Lexington axis. Prevailing
showers are likely at LEX early Wednesday, with BWG likely seeing
some of this activity as well. Lower MVFR stratus will also be more
common further east during the first half of Wednesday. SDF should
stay just west of the steady rains. A line of scattered
thunderstorms should develop between 18-00z tomorrow, again with BWG
and LEX the most likely sites to be impacted.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...RJS
Short Term...WFO PAH
Long Term...WFO PAH
Aviation...EBW
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
719 PM CDT Tue Jul 31 2018
.SHORT TERM...(This evening through Wednesday)
Issued at 338 PM CDT Tue Jul 31 2018
The main concern in the short term period is the frontal boundary
expected to move through the region from Northwest to southeast and
associated showers and thunderstorms.
As of this afternoon, the aforementioned frontal boundary was draped
across southern Canada and an amplifying upper level trough from near
Hudson Bay to the southwest. South of the front, high pressure has
taken hold over the high plains, with our region on the northern
extent.
The weak cold front will push south through much of central MN late
tonight, primarily from 07-10Z for places like Alexandria and St.
Cloud. Scattered thunderstorms along the front are expected, but
severe weather is not expected and the storms should generally be
decaying as they progress southeastward. By the time they reach the
Twin Cities metro, it`s very possible they`ll just be scattered
showers with no thunder remaining in the 11-14Z time frame. There is
a marginal risk of severe weather for tomorrow afternoon for along
and east of the front, which by the afternoon will be from northwest
WI to the southwest, the Mankato area and toward northwestern Iowa.
A scattered thunderstorms are likely east of the front, with a few
of the storms strong. Instability will be marginal, but shear will
be rather limited hence the threat for severe weather is low.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 338 PM CDT Tue Jul 31 2018
The cold front will be south of the area by Wednesday night with
clearing skies and drier air behind the front leading to a
relatively chilly morning, with some 40s expected in spots across
central MN and west-central WI. One last cool & pleasant day with
highs in the 70s is expected Thursday, before a pattern change
comes Friday.
Flow aloft becomes more zonal on Friday as the upper trough
flattens out and the persistent southwest ridge begins to build
back to the east. Our flow becomes southerly at the surface behind
a warm front with dewpoints surging back into the mid-upper 60s
and temperatures in the mid-upper 80s. Multiple vorticity lobes
passing over the area will create rain chances beginning overnight
Friday, and continuing into next week. When we see our best shot
will depend on the timing and location of the frontal boundary
extending south over the area from a surface low over central
Manitoba. With the juicy dewpoints at the surface SBCAPE will have
no problem approaching 3000 J/kg and the stronger flow aloft will
allow for deep layer shear of 30-40 kts. Storm coverage will
likely be limited to near the front as there isn`t much else in
terms of surface forcing so will have to watch the threat for
severe weather this weekend if the front sets up over our area
during the afternoon/evening.
Beyond the weekend, models really begin to diverge in handling the
upper air pattern so there is little confidence in the forecast.
Precip chances look to linger into Monday as the front remains in
the vicinity of the area, with a cooler/wetter pattern next week
favored by the 12Z GFS & a warmer/drier under continued ridging
from the 12Z Euro.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 719 PM CDT Tue Jul 31 2018
Uncertainty remains with coverage of storms we will see as cold
front pushes through Wednesday. Timing of the front remains
similar to 18z TAF, but HRRR and other models are all over the
place on how much activity we`ll see, though that trend is a
downward trend, so pulled back any precip mentions to VC. Frontal
position in afternoon looks to be far enough southeast where EAU
is the only airport with a good chance at seeing afternoon storms.
Behind the front, forecast soundings, LAV guidance, and HRRR cig
forecast all show a band of MVFR, possibly IFR up toward AXN/STC
moving through.
KMSP...Shower chance still looks best between 11z and 15z as the
front is working through, though those chances look rather meager.
Front looks far enough southeast in the afternoon to where
afternoon storm development will be well southeast of MSP. For
post frontal MVFR, HRRR is starting to really thin out it`s MVFR
field at the end of the run, so wouldn`t be surprised if residence
time in MVFR cigs is even shorter than the 4 hours we currently
have.
/OUTLOOK FOR KMSP/
Thu...VFR. Wind E bcmg S 5 kt.
Fri...VFR. Wind S 10-15 kt.
Sat...VFR. Chc -TSRA. Wind SW 10-15 Gusts 20-25 kt.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...SPD
LONG TERM...ETA
AVIATION...MPG
Area Forecast Discussion
National Weather Service Morristown TN
1049 PM EDT Tue Jul 31 2018
.DISCUSSION...
A very late evening update here, mainly to account for trends in
precipitation over the last hour or two. Guidance has struggled
greatly to latch on to how the evening would play out, but it
seems a bit of a consensus has been reached. Trended the rest of
the overnight hours heavily in the direction of the most recent
RAP runs, which will favor some continued high chance or likely
PoPs along the western CWA boundary over the plateau region. The
RAP seems to be handling the trends well over the last few hours,
so there`s increased confidence there. Lowered, but did not get
rid of, pops over the central and northern valley, southwest
Virginia, and the eastern Tennessee mountain areas. Otherwise, no
significant changes were made to the forecast.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 71 80 71 80 / 80 80 70 60
Knoxville McGhee Tyson Airport, TN 69 77 69 78 / 50 90 70 80
Oak Ridge, TN 69 78 69 79 / 60 80 60 60
Tri Cities Airport, TN 67 77 67 79 / 70 90 70 80
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...Flash Flood Watch from 8 AM EDT Wednesday through Thursday
evening for Cherokee-Clay.
TN...Flash Flood Watch from 8 AM EDT Wednesday through Thursday
evening for Blount Smoky Mountains-Cocke Smoky Mountains-
East Polk-Sevier Smoky Mountains-Southeast Carter-Southeast
Greene-Southeast Monroe-Unicoi.
VA...None.
&&
$$
CD
Area Forecast Discussion
National Weather Service Mount Holly NJ
1146 PM EDT Tue Jul 31 2018
.SYNOPSIS...
A warm front will lift north across the region overnight and
Wednesday morning. High pressure will stay anchored off the
East Coast while a surface trough remains entrenched over the
eastern seaboard through the early part of the weekend. The high
begins to break down over the weekend and the surface trough
finally moves offshore late Saturday. Another surface trough may
develop across the region Sunday through early next week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of late evening, an area of showers is moving across parts of
Delmarva and southern New Jersey. This has been weakening
however with a northern extent as it outruns the instability.
The greatest instability remains south of the warm front. Some
lightning strikes are occurring at times just to our south, and
this could get into Delmarva at times overnight. Hi-res models
such as the HRRR and NAM-nest are not representing this very
well, so don`t know whether to believe their trend to diminish
the precip coverage. The short term PoP grids were adjusted to
fit the radar-observed precip. Otherwise not much change to the
going forecast.
Otherwise, clouds are expected to remain overhead for tonight.
As the warm front approaches from the south with a mid level
impulse passing overhead from the southwest should result in an
increasing chance of showers and isolated thunder overnight.
Low temperatures are forecast to favor the upper 60s in the Poconos
and in far northern New Jersey. They should be mainly in the lower
70s in the Lehigh Valley, southeastern Pennsylvania, much of New
Jersey, Delaware and northeastern Maryland.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
We expect showers and isolated thunder, associated with the warm
front in our region, during the morning hours. The boundary should
lift through eastern Pennsylvania, and central and northern New
Jersey on Wednesday. Once the front moves to the north, and our
region will get into the warm sector. The focus of the shower and
thunderstorm activity is expected to shift to areas mainly along and
to the northwest of the Interstate 95 corridor.
Precipitable water values will rise in excess of 2 inches. As a
result, there will be an increasing threat of locally heavy
downpours as we get into the afternoon hours. Also, mixed layer CAPE
values are expected to build into the 1000 to 2000 J/kg range with a
fair amount of shear present. Most of our region is under the Storm
Prediction Center`s marginal risk designation for severe weather.
Parts of eastern Pennsylvania and northern New Jersey are one
category higher and under the slight risk designation.
The wind should become south to southwest in the wake of the warm
front. Wind speeds will likely increase around 10 MPH with gusts
near 20 MPH, especially on the coastal plain.
Maximum temperatures are anticipated to be mainly in the 80s.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
An unsettled forecast is still expected for much of the long term
period, although it will not rain the entire time.
A southwest flow will strengthen across the area as high pressure
begins to build westward into the area from the Atlantic at the
beginning of the long term period. This high is expected to remain
offshore through Friday. Meanwhile, a cold front is expected to
dissipate Wednesday night as it approaches and a surface trough
develops across the eastern seaboard. With the high offshore,
this surface trough will remain stationary through the end of
the week. A ridge aloft will remain offshore of the east coast
while a trough remains in place to our west as well. This will
all keep a steady southwest flow across the area, which will
allow moisture to continue to pump into the region through the
week. This is evident from PW values increasing to 1.75- 2.00
inches across the area and remain in place through the end of
the week. So there will be a chance of showers and thunderstorms
each day from Wednesday night through Friday. Much of the
activity will likely be diurnally driven and focused during
times of short wave/vorticity impulse passages. Latest guidance
has been trending the precipitation generally to the west, so
will continue to monitor future runs for consistency.
By Saturday, the high pressure at the surface begins to break
down as the ridge aloft begins to shift westward across the deep
south. This will allow for the surface trough to move across the
area later Saturday, while the flow aloft becomes more westward or
nearly zonal. There will remain a enhanced chance of showers and
thunderstorms on Saturday with the passage of the surface trough and
any short wave/vorticity impulse passages. There is some discrepancy
between the GFS and ECMWF as to the amplitude of the short
wave/surface trough and associated precipitation.
By Sunday, another surface trough may develop across the east coast
and remain in place through at least Tuesday as another short wave
moves around the ridge to our south. The flow aloft remains more
westerly, or shifts more northwesterly by Tuesday, while PW values
lower to 1.5-1.75 inches. The shower/thunderstorm chances decrease
for Sunday into Monday, but do not drop off completely as there
could be some weak short waves/vorticity impulses move across the
area. However, the GFS suggests a stronger short wave could move
across the area on Tuesday, which could lead to an enhanced chance
of showers and thunderstorms. The ECMWF does comply as it suggests
continued zonal flow across the north-central U.S.
Overall, temperatures are expected to remain near to slightly above
normal through the weekend.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Overnight...Ceilings lowering to MVFR and IFR with some showers
expected, and with isolated thunder possible. Southeast wind 8
knots or less.
Wednesday...MVFR and IFR in the early morning, improving to VFR
ceilings. A chance of showers and thunderstorms. The rain may be
locally heavy in the afternoon. Wind becoming south to southwest 8
to 12 knots with gusts near 20 knots.
OUTLOOK...
Wednesday night-Friday night...Showers and thunderstorms
possible each day, most likely during the day and early evening.
Lower ceilings and visibilities possible with the showers and
thunderstorms. However, outside of any shower and thunderstorm
activity, generally VFR conditions are expected.
Winds generally from the south to southwest 5-10 knots, with
gusts 15-20 knots during the day. Higher gusts in thunderstorms.
Saturday...Chance of showers and thunderstorms continue with
lower ceilings and visibilities associated with the showers and
thunderstorms. Otherwise, generally VFR is expected.
A surface trough pushes offshore late Saturday, shifting winds to
the west to northwest for Saturday night and Sunday.
&&
.MARINE...
A warm front will lift slowly northward across the coastal waters of
Delaware and New Jersey tonight and Wednesday.
The wind should be from the east and southeast around 10 knots into
tonight. The wind is forecast to shift to the south and increase to
15 to 20 knots on Wednesday in the wake of the warm front. Gusts
around 25 knots are possible on our ocean waters on Wednesday
afternoon. The Small Craft Advisory remains in place.
Waves on our ocean waters should be 3 to 4 feet tonight, and 4 to 6
feet on Wednesday. Waves on Delaware Bay are expected to be 2 feet
or less tonight, and 2 to 3 feet on Wednesday.
OUTLOOK...
Wednesday night-Friday night...Small Craft Advisory
conditions may continue through the end of the week as southwest
flow could keep seas around 5 feet and winds could gust 25-30 knots
at times.
Saturday-Sunday...Conditions may fall back below advisory levels,
but winds may still gust near 20 knots at times and seas could
remain near 4 feet.
RIP CURRENTS...
Increasing southerly winds and building waves, along with an
underlying 9-second southeast swell, should result in a high
risk for the development of dangerous rip currents along the New
Jersey shore on Wednesday. A moderate risk is forecast for the
Delaware beaches, where the coastline orientation should result
in a slight offshore component to the prevailing wind.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...High Rip Current Risk from 8 AM EDT Wednesday through
Wednesday evening for NJZ014-024>026.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 8 AM Wednesday to 6 PM EDT Thursday
for ANZ452>455.
Small Craft Advisory from noon Wednesday to 6 PM EDT Thursday
for ANZ450-451.
&&
$$
Synopsis...Miketta
Near Term...AMC/Gorse/Iovino
Short Term...Iovino
Long Term...Davis/Miketta/Staarmann
Aviation...Iovino/Miketta
Marine...AMC/Iovino/Miketta
Area Forecast Discussion
National Weather Service Pocatello ID
237 PM MDT Tue Jul 31 2018
.DISCUSSION...Today Through Next Tuesday.
Heat will be the main story today across SE Idaho, as high
temperatures are projected to reach the upper 90s across lower
elevations from the central Snake Plain southward. HeatRisk
guidance is brushing near Heat Advisory criteria today into
tonight, but concur with the overnight shift that the need for an
advisory is marginal, with qualifying values covering less than
half of any given forecast zone. In addition, quite a bit of smoke
and haze remains across the region per surface observations and
GOES-16 satellite imagery, and some scattered high-level cloud
cover is starting to push into the western half of the forecast
area. How much these factors might influence high temps is
uncertain, but if anything it nudges our confidence further away
from considering a Heat Advisory. See the CLIMATE section below
for more on our ongoing heat wave. We do also carry a slight
chance (15-25%) of isolated showers/t-storms this afternoon and
tonight across the Central Mntns, Upper Snake Highlands, and
western Southern Highlands. High-res HREF ensemble CAMs are
carrying some echoes, but are generally not showing significant
cores with very limited activity on the 40 dBZ paintball plot,
reinforcing our thinking that activity will be quite isolated with
limited t-storm potential. With very dry air in the low levels
and strong inverted-V soundings/modest DCAPE values, but
otherwise unimpressive instability and shear, greatest threats
from any storms today/tonight will be gusty winds and lightning
strikes, with very little precip expected to reach the ground.
Greater monsoonal moisture will surge into ID Wed, with a chance of
showers/t-storms everywhere. The two corridors most favored by
the HREF ensemble and even NAM/GFS guidance are across the Central
Mntns, Upper Snake Plain, Island Park region, and Teton Valley,
and then across the Southern Highlands and Bear Lake region. For
these two zones we`ve added scattered t-storm coverage, isolated
in between. NAM forecast soundings show PWAT values rising into
the 0.75 to 1.00 inch range, indicative of that increasing mid-
level moisture, while soundings continue to show inverted-V
signatures with LCLs at or above the melting layer and impressive
DCAPE values reaching 1,000 to 1,500 J/kg. Thunderstorms should
still be somewhat dry, but heavy downpours will be possible with
the stronger cells, and strong downdraft/outflow winds in excess
of 50 MPH will still be the greatest threat along with perhaps
some hail. Some increased deep-layer wind shear up to 35 knots
(best to the north) may aide in a bit in storm organization and
longevity. A severe thunderstorm cannot be ruled out with strong
damaging winds the greatest threat, although meager surface
instability may be a limiting factor. Lightning and gusty winds
will remain key concerns for fire weather partners, and with
scattered coverage expected, we have issued Red Flag Warnings for
large portions of the area. See the FIRE WEATHER section below for
details. We will have to monitor morning cloud cover, as this
could limit afternoon instability.
We hold on to a chance of some showers/t-storms for some of our
mountain ranges Thurs afternoon/eve, but otherwise Thurs kicks off a
drying trend as a weak cold front crosses the region. This will
usher in much drier air/low RH values along with higher winds Thurs
and Fri afternoons, both of which may reach critical thresholds to
necessitate additional Red Flag Warnings. Beyond Fri, we currently
hold the forecast dry, but it should be noted that this is a low-
confidence forecast with both the GFS/ECMWF hinting at a disturbance
Sun. The models then diverge significantly as the GFS builds a ridge
over the region with continued dry conditions, while the EC and
Canadian bring a strong low pressure system/attendant trough
across the northern Rockies. Expect adjustments to the forecast as
we watch how the models trend with these features. - KSmith/DMH
&&
.AVIATION...
Upper ridge beginning to shift east across the region today.
Moisture streaming east from Oregon producing light radar returns
in mainly upper level cloud shield. Expect any convection that
could develop today to be dry with little precipitation reaching
the ground. Thus, VFR conditions expected to continue, though
wind gusts >40 MPH will be possible. Best chances of this
activity impacting terminals will be at KSUN early, transitioning
east through the evening with VCSH for KDIJ. Cannot rule out weak
convection continuing overnight, but much better chances occur
during the day Wednesday. KPIH currently appears to have the least
chance to be affected by thunder, but do anticipate threat is
enough to have VCTS for that terminal during the afternoon. - DMH
&&
.FIRE WEATHER...
Moisture beginning to work into the region under the apex of
upper level ridge. Isolated dry thunderstorms remain possible
through the evening for almost all but the Snake Plain. Depth of
moisture increases tonight through Wednesday, with greater
coverage of thunderstorms expected during the day. Storms
transition to hybrid wet/dry, though limiting factor could be
early cloud cover. Have pulled early trigger on Red Flag Warning
for Wednesday afternoon and early evening for widely scattered or
better thunderstorm coverage. Upper trough transitions east across
the panhandle into Montana on Thursday, dragging surface frontal
boundary with it. Thunder expected to remain a potential threat
mainly ahead of the surface boundary. Much drier air pushes into
the region behind the front, and combined with deep mixing, expect
winds and humidities to exceed critical thresholds. These
conditions continue into Friday. Thus once thunder threat
decreases, both days look to be another Red Flag day just for
different criteria, and anticipate that will be issued or extended
on upcoming shifts. Model trends continue to shift toward East
Idaho remaining under the influence of weak Pacific energy. There
is not a lot of confidence in an increased threat of thunder
across the region, so forecast remains dry. Winds however do
appear to be stronger, and this may be a concern depending on the
humidities moving toward the weekend. - DMH
&&
.CLIMATE...
A historic long-duration heat wave continues into yet another week
across SE Idaho. Pocatello Airport (KPIH) continues to add to it`s
all-time record for longest streak of high temperatures at or above
90 since records began in 1939 that started back on July 4th, now
sitting at 28 consecutive days as of today. Pocatello also
continues to sit in 10th Place for highest July mean average temp
as of Mon 07/30/18 at 73.5 degrees, which dropped just slightly
and is holding us shy of the 9th Place value of 73.8 degrees from
July of 1975. Burley Airport (KBYI) is sitting at 20 consecutive
days at or above 90 as of today, holding it in 4th Place for
longest streak since records began there in 1948. 3rd Place is 21
days ending August 20th, 1981. It is possible that some of our
other non-climate sites have broken into the Top 10 for longest
streaks at or above 90 as well this month. This heat wave has been
historic in it`s persistence and duration, but not necessarily
for extreme values. Only a few days have approached 100 degrees,
and only a couple record high temps have been tied this month at
our climate sites.
As discussed in the DISCUSSION section above, today is slated to be
one of the hottest days we have observed so far this summer, with
high temperatures forecast to reach the upper 90s in lower
elevations from the Snake Plain southward. Even with a light haze
of smoke hanging over large portions of the region today and some
high clouds observed on satellite pushing east across western ID,
temperatures at Pocatello and Burley have already exceeded 90. Tomorrow
will provide a slim shot to break the streak, with increased
cloud cover due to showers and t-storms. Cooler temps Fri and Sat
following a frontal passage may provide a slightly better chance
of breaking the heat wave. Stay tuned. - KSmith/DMH
&&
.AIR STAGNATION...
Varying degrees of degraded air quality are expected to continue
across SE Idaho for at least the next several days due to
numerous wildfires burning across the Pacific Northwest.
Haze/smoke remains evident today on both GOES-16 satellite imagery
and surface observations, with local diurnal wind trends
governing which areas will see the most smoke at any given time.
The Sharps fire continues to be our greatest local contributor,
but the HRRR smoke model clearly shows large smoke plumes
advecting in from CA, OR, and NV as well. The Idaho Department of
Environmental Quality (ID DEQ) currently rates air quality
"Moderate" across the lower Snake Plain and eastern Magic Valley,
meaning that air quality is acceptable, however, for some
pollutants there may be a moderate health concern for a very small
number of people who are unusually sensitive to air pollution.
Air quality is now rated "Unhealthy for Sensitive Groups" in the
Central Mntns. In general, the greatest smoke pooling will occur
at night in valleys/lower elevations, and this is when the
greatest impacts may be noticed. Have maintained mention of areas
of smoke in the weather grids through at least Thurs morning. Some
relief is possible by Thurs/Fri as a weak cold front ushers in
stronger afternoon/eve winds across the region. - KSmith/DMH/NP
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon to 9 PM MDT Wednesday for IDZ410-413-
427-475-476.
&&
$$
Area Forecast Discussion
National Weather Service Great Falls MT
847 PM MDT Tue Jul 31 2018
.UPDATE...
Evening update has been published, with only minor adjustments
made to POPs to account for latest radar trends and Hi-Res model
guidance. In addition to minor tweaks to POPs, also added smoke
and haze for areas south and west of a Cut Bank, to Great Falls,
to Lewistown line to account for observations and latest HRRR
smoke guidance. A weak wave embedded within the upper level
southwest flow will rotate across the ridge axis tonight and
across portions of Central and Southwest Montana. This disturbance
is expected to bring isolated-to-scattered showers and even a few
isolated thunderstorms to areas generally along and south of a
Helena to White Sulphur Springs line. Otherwise, left the Fire
Weather Watch for Fire Weather Zone 112 for Wednesday
afternoon/evening as is so that the midnight shift can re-
evaluate with the latest model sweet. - Moldan
&&
.SYNOPSIS...
Temperatures trend warmer Wednesday into Thursday. Scattered
thunderstorms are possible across southwest Montana Wednesday and
Thursday afternoons. Breezy west winds develop later on Thursday
into Friday as a dry cold front moves through the state.
&&
.AVIATION...
Updated 2330Z.
VFR conditions are expected to prevail across Southwest and North
Central Montana beneath scattered to broken high cloud cover. A weak
disturbance moving across Idaho/Southern Montana/Wyoming this
evening may spark off a few isolated thunderstorms south of the
Interstate 90 corridor and along the Continental Divide, however,
confidence was to low to put any mention of TS in this TAF package
for the KEKS, KBZN, and KHLN terminals. Haze from fires originating
further west will continue to impact the region, which will lead to
reduced visibilities and potentially some mountain obscuration.
Finally, variable winds will gradually increase and turn to the
southwest/west tomorrow as a disturbance develops over Southern
Alberta Canada. - Moldan
&&
.FIRE WEATHER...
Hot and dry weather returns on Wednesday as an upper level ridge
settles over the region. Low pressure develops Wednesday afternoon
over southern Alberta. This will create gusty winds, combined with
low afternoon relative humidity. A Fire Weather Watch has been
issued for Wednesday afternoon across western portions of zone
112. Isolated to scattered dry thunderstorms are possible
Wednesday and Thursday afternoon over the central mountains into
southwest Montana. A dry cold front is expected to arrive later
Thursday evening, possibly producing critical fire weather
conditions across North-central Montana Thursday afternoon through
Friday.
&&
.PREV DISCUSSION...
/ISSUED 530 PM MDT Tue Jul 31 2018/
Tonight through Wednesday Night... Very warm air will move back
over the entire forecast area again on Wednesday, as many lower
elevation areas warm well into the 90s. The airmass will become
unstable once again with the warming temperatures and another
disturbance will bring another round of isolated thunderstorms
during the afternoon and evening hours.
Thursday through next Tuesday...The high pressure ridge aloft
breaks down over our CWA on Thursday as a Pacific cold front
sweeps eastward over our region and a shortwave trough approaches
from the west. Isolated showers and thunderstorms remain possible
along and ahead of this front on Thursday. The shortwave trough
then traverses our area on Friday into Saturday morning, allowing
the potential for a few showers and thunderstorms to persist. An
overall drying trend is then expected the rest of the weekend as
a shortwave ridge builds from the west. A longwave trough aloft
and embedded disturbances then overspread our CWA from the west
Monday and Tuesday of next week, renewing the potential for a few
showers and thunderstorms.
The above pattern and diurnal mixing of the boundary layer will
promote breezier southwesterly to westerly surface winds, mainly
this Thursday/Friday and perhaps again on Monday/Tuesday of next
week. These winds will contribute to the likelihood of critical
fire weather conditions developing this Thursday and Friday.
Please see the fire weather discussion for further details. Low
temperatures trend near-normal through next Tuesday. After
slightly above-normal highs on Thursday, high temperatures will
trend near or slightly below-normal for the balance of the
period.
- Jaszka
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 58 96 60 94 / 10 0 10 0
CTB 54 93 54 89 / 0 0 0 0
HLN 58 93 60 91 / 10 10 10 10
BZN 53 90 55 90 / 20 10 10 20
WEY 39 80 42 81 / 20 30 30 20
DLN 53 86 53 87 / 20 20 20 20
HVR 58 97 60 96 / 0 0 0 0
LWT 55 89 58 89 / 10 0 10 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Wednesday afternoon through Wednesday
evening Deerlodge/Western Beaverhead National Forest...Eastern
Beaverhead National Forest.
Fire Weather Watch from Wednesday afternoon through Wednesday
evening Eastern Glacier/Toole/Central/Eastern Pondera/Liberty.
&&
$$
http://www.weather.gov/greatfalls