Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/30/17
Area Forecast Discussion
National Weather Service Dodge City KS
801 PM CDT Sat Jul 29 2017
...updated aviation section...
.SHORT TERM...(This evening through Sunday)
Issued at 241 PM CDT Sat Jul 29 2017
Radar indicating scattered convection trying to develop across
western Kansas as of 2 pm. The HRRR may be a little too aggressive
with the storms developing late today but it does seem to have
the right idea on location for these afternoon and evening storms.
These storms late today are not expected to be severe but locally
heavy rainfall will be possible.
The better chance for convection for western Kansas will occur
after midnight, as another upper level wave exiting the Central
Rockies and moving out into the Western High Plains. Abundant
moisture will be in place ahead of this upper wave and given
improving lift developing across western Kansas which will be northeast
of a 10C to 14c 700mb baroclinic zone the idea of a cluster of
thunderstorms developing ahead of the upper wave and moving across
western Kansas late tonight still appears reasonable. Based on
where this area of better lift and moisture is forecast to be
located overnight place the best chance for convection will be
over west central Kansas and portions of north central Kansas.
These storms much like the storms Friday night will be capable of
producing periods of very heavy rainfall so will continue with the
flash flood watch for areas west of Garden City to Hugoton line.
May also need to monitor the heavy rains that may develop towards
daybreak north of Garden City but since they did not receive much
rainfall from last night have decided not to include them in our
current Flash Flood Watch.
Clouds, Rain showers, and thunderstorms is expected to continue
through much of the day on Sunday and as a result will favor the
cooler guidance for highs, mainly across west central and north
central Kansas.
.LONG TERM...(Sunday night through Saturday)
Issued at 241 PM CDT Sat Jul 29 2017
Several subtle upper level waves embedded in a northwesterly flow
will continue to cross western Kansas over the next 5 days. As
each of these upper waves pass there will be a chance for
additional showers and thunderstorms across some portion of
western Kansas. At this time the area most favorable for
precipitation during the first half of the work week will be west
of highway 283. Heavy rainfall will be the main hazards for these
storms from Sunday night through Tuesday so there may still be a
chance for some additional water issues, mainly west of a Garden
City to Liberal line Sunday night. Currently have a flash flood
watch in effect for tonight and after good collaboration with our
neighbors we have decided no to extend the watch just yet and let
next shift reevaluate this.
Temperatures will not warm much next week given the expected
cloud cover, precipitation chances, and 900mb to 850mb temperature
trends. The warmer temperatures are expected to be east of Dodge
City where more afternoon sunshine is expected while the cooler
temperatures will be located further west. Highs mainly in the
upper 70s to mid 80s still look on track for Monday and Tuesday.
A brief warming trend will occur Wednesday and possibly Thursday
as a wedge of warmer 850mb temperatures precede out next cold
front. Temperatures will be warming through the mid to upper 80s
and even some lower 90s will not completely out of the question
across portions of southwest Kansas. Precipitation can not be
completely ruled out mid week but the better opportunity will come
with the cold front late week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 756 PM CDT Sat Jul 29 2017
There will occasional thunderstorms impacting the local terminals
going forward over the next 12 to 18 hours. Convection should
produce locally heavy rain as well as weak to moderate
thunderstorm outflow winds overnight, with minimal hail of severe
wind threat. Models are not indicating widespread low cigs in the
IFR category, however as the convective threat evolves, TAF
updates may be needed.
&&
.HYDROLOGY...
Issued at 241 PM CDT Sat Jul 29 2017
Models remain in good agreement with high preciptable water
values across western Kansas over the next few days as a series of
upper level waves embedded in a northwesterly flow crosses the
Western High Plains. One cluster of thunderstorms can be expected
overnight into Sunday morning as the first in a series of upper
level disturbances crosses western Kansas. Based on the rainfall
over the past 24 hours combined with the potential rainfall
overnight there will a chance for some water issues, especially
across west central Kansas. A flash flood watch has been issued by
the previous shift for areas west of a Garden City to Hugoton
line and this still looks like the most favorable area for
flooding issues. Heavy rainfall will also be possible north and
northeast of Garden City tonight but these areas have not had much
rain over the past few days at this time there are no plans to
expand the watch further northeast. Will continue to monitor this
and make adjustments as needed.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 68 79 62 76 / 70 50 60 50
GCK 67 78 62 74 / 80 60 50 40
EHA 70 84 62 78 / 50 50 70 40
LBL 71 84 63 76 / 50 40 60 50
HYS 67 76 61 79 / 60 60 30 20
P28 71 82 64 80 / 30 30 40 30
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 7 AM CDT /6 AM MDT/ Sunday for KSZ061-
062-074-084.
&&
$$
SHORT TERM...Burgert
LONG TERM...Burgert
AVIATION...Russell
HYDROLOGY...Burgert
Area Forecast Discussion
National Weather Service Houston/Galveston TX
934 PM CDT Sat Jul 29 2017
.DISCUSSION...
The pre-frontal trough was setting off some thunderstorms in
Orange and Jefferson counties toward the Sabine at 9:30 PM. The
HRRR has been handling the coverage fairly well as of the last
couple of runs. 00Z upper air profiles show the potential for a
decent low-level inversion to be in place and this is shown on the
latest NAMBufr forecast soundings across the forecast area. Best
chances will be over the far eastern areas. The current forecast
is on track.
40
&&
.PREV DISCUSSION... /ISSUED 623 PM CDT Sat Jul 29 2017/
AVIATION.../00Z TAF/
Latest radar and GOES 16 imagery show several boundaries across
SE Texas. There is the sea breeze along the coast held in check by
synoptic pressure gradient support SW to W winds. Sea breeze is
making some progress north as winds have backed to SE at KHOU and
KIAH, but it is slow progress. To the north is another boundary
from Temple to Huntsville to may be near Beaumont. The true
frontal boundary is still to the north over the Arklatex pushing
SW towards the area. Think VFR conditions continue despite the
front moving into the region. Upper level riding looks to be too
strong for convection to over come. CAMs show some convection
developing in the 08Z to 15Z time frame so will keep VCSH in the
TAFs to cover that small possibility. Again it is a small chance
and overall confidence in any convection is low.
Overpeck
PREV DISCUSSION... /ISSUED 347 PM CDT Sat Jul 29 2017/
DISCUSSION...
Heat index values range from 100 to 112 degrees across Southeast
Texas this afternoon, with highest heat index values being
observed near and just behind the seabreeze evident on the KHGX
radar moving inland across Brazoria, Galveston, and Chambers
counties. Heat will remain the big concern through the early
evening hours and a Heat Advisory is in effect for much of the
region through 7 PM CDT. Additionally, as of 3 PM CDT, Houston
Hobby had hit 100 degrees... tying its record high temperature for
today set in 2015. It`s possible that this record may be broken
before the seabreeze moves inland later this afternoon.
Afternoon surface analysis showed that a cold front had made
minimal progress towards the region, stretching from near Wichita
Falls across the D/FW Metroplex to south of Shreveport. Ahead of
this front, a prefrontal trough stretched from Midland towards
Lufkin. Subsidence from upper ridging centered over West Texas has
done a good job limiting most convective development along these
features so far today, but will need to keep an eye on both
through the evening and into the overnight hours as mid-level flow
veers from northwest to northerly and allows these boundaries to
push farther into the region. Visible satellite imagery has has
shown some enhancement to the cumulus clouds across Houston and
Trinity counties over the past hour and would expect the northern
and northeastern counties to be the first to see isolated shower
or thunderstorm development during the late afternoon hours along
the prefrontal trough.
Loss of heating should result in anything that develops to fall
apart by mid-evening, but weak divergence spreading over the
region as the upper ridge retreats overnight should allow for
another round of isolated to scattered showers and thunderstorms
to develop along the cold front as it moves southwest across the
region. Anything that develops during the afternoon or evening
hours would be capable of a gusty wind threat as forecast
soundings continue to indicate an inverted-V signature (meaning
that dry sub-cloud air may enhance evaporational cooling leading
to downdraft acceleration) with showers and thunderstorms that
develop along the front tonight capable of producing locally heavy
rainfall. Surface convergence inland along the front is expected
to be weak and, as a result, expect greatest shower and
thunderstorm coverage across the coastal waters tonight. However,
with precipitable water values pooling in excess of 2 inches
ahead of the front, expect areas generally along and south/east
of Highway 59 to have the greatest potential for seeing rain (and
locally heavy rain/ isolated 1-2 inch totals).
The front will continue to slowly sag southwest across the region
during the day Sunday, with a few showers lingering along it as
it washes out approaching the Middle Texas Coast. Otherwise,
morning lows on Sunday are expected to range in the mid 70s to low
80s and warm into the low to mid 90s during the afternoon. Drier
air behind the front will help keep afternoon heat index values a
bit "cooler" than today in the 96-106 range... but Sunday will
still feel like summer.
Upper ridging will continue to retreat from the region towards the
west Monday and Tuesday, with falling mid-level heights resulting
in temperatures dropping back to near normal for this time of year
(highs in the upper 80s to mid 90s) and increasing rain chances
Wednesday into the next weekend. Timing of greatest chances still
remains a bit uncertain at this time as it appears to largely
depend on when disturbances rotate through upper troughing that
becomes established across the eastern CONUS mid to late week.
Huffman
MARINE...
A light southwesterly wind regime can be expected out ahead of
the weak front this evening, which should reach the coastal waters
overnight tonight and into early Sunday morning. With the passage
of this system, high PW values between 2.1-2.4 as well as the
added lift could result in isolated to scattered showers and
thunderstorms developing in the near and offshore waters. Gusty
winds can be expected beneath stronger storms. Expect to see the
winds begin to turn due to the influence of the frontal passage,
becoming northeasterly by late Sunday morning. Seas should stay
around 2 ft in the beginning of week and eventually bump up to 3
ft towards the end of next week. Onshore flow should also return
to the forecast late Wednesday into early Thursday.
Hathaway
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 78 96 72 96 75 / 20 10 10 10 10
Houston (IAH) 79 95 75 94 76 / 30 20 10 10 10
Galveston (GLS) 81 90 80 90 81 / 30 30 10 10 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&
$$
Discussion...40
Aviation/Marine...39
Area Forecast Discussion
National Weather Service Wichita KS
921 PM CDT Sat Jul 29 2017
.UPDATE...
Issued at 920 PM CDT Sat Jul 29 2017
Convection over the high plains, hasn`t really gotten going too
well, considering the weak moisture transport in wrn KS. Latest RAP
doesnt show moisture transport increasing considerably late this
evening, with instability axis also staying across wrn KS as well.
Even if convection can increase much, propagation takes most of the
convection to the S-SE, or no where near the wrn sections of the
forecast area overnight or early Sun morning. There is some
additional convection across SE CO, which may drift east
overnight, but think this convection will diminish as it shifts
east, away from the main instability axis, which will remain over
wrn KS. So plan on cutting back on pops for areas west of I-135
with this in mind. Will leave a slight pop in for Cen KS, but
think convective chances are diminishing.
Ketcham
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 253 PM CDT Sat Jul 29 2017
Shortwave trough is rotating across the northeast conus with water
vapor imagery showing a much weaker impulse tracking across the
northern Rockies. Cluster of storms that tracked out of western KS
early this morning is currently dissipating over central KS.
Should see another round of showers and storms develop over
eastern CO/far western KS late this afternoon and track southeast
tonight. Just like last night, this activity should go through a
slow dissipating trend as it approaches the western fringes of
our forecast area with the better 850-700mb moisture transport
staying out over western KS. Once again, areas west of I-135 will
have the better chances at showers/storms early Sun morning into
the early afternoon hours. Overall repeat can be anticipated for
Sun night into Mon morning before the better low level moisture
gets pushed southwest for Mon night through Tue night.
Confidence remains high that below normal temps will remain in
place through Tue with highs in the low to mid 80s. Normal highs
for this time of year are in the low 90s.
.LONG TERM...(Wednesday through Saturday)
Issued at 253 PM CDT Sat Jul 29 2017
The main story through these extended periods will be another
cold front set to come through toward the end of the work week.
There is decent model agreement in shortwave energy diving out of
the northern Plains and into the mid Mississippi Valley by Thu
night. This will allow an unseasonably strong cold front to push-
in from the northeast. Some scattered showers and storms will be
tied to this front as it tracks southeast for Thu night into Fri
morning. Would not be surprised if medium range models continue
this trend that some locations over central KS end up with highs
in the 70s for Sat.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 628 PM CDT Sat Jul 29 2017
VFR conditions are expected for the next 24 hours. Convection over
the high plains and NW KS is expected to form into an eastward
forward propagating MCS late tonight. As it moves further east,
think the storms will diminish as they outrun the main instability
axis as they approach Cen KS. But a few storms may make into KGBD
and KRSL after 08-09z/Sun. So will go with a VCTS for this chance.
Expect mid level clouds to remain over most areas west of I-135 for
the daylight hours on Sun.
Ketcham
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 66 84 64 83 / 10 10 10 10
Hutchinson 65 83 61 82 / 10 20 10 10
Newton 64 83 61 82 / 10 10 10 10
ElDorado 64 84 61 83 / 10 10 10 0
Winfield-KWLD 65 85 63 84 / 10 10 10 10
Russell 63 79 61 82 / 30 40 20 10
Great Bend 64 79 60 81 / 30 40 30 20
Salina 64 83 62 86 / 10 10 10 0
McPherson 65 83 60 83 / 10 20 10 10
Coffeyville 63 86 63 86 / 0 0 0 0
Chanute 61 84 62 84 / 0 0 0 0
Iola 61 83 61 84 / 0 0 0 0
Parsons-KPPF 62 85 63 85 / 0 0 0 0
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Ketcham
SHORT TERM...RBL
LONG TERM...RBL
AVIATION...Ketcham
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1119 PM EDT Sat Jul 29 2017
.UPDATE...
Issued at 1100 PM EDT SAT JUL 29 2017
Clouds persist across the southeastern part of the region though
they appear to be decreasing in areal extent. Also, light
northeast flow persists and is keeping the atmosphere mixed in
many locations though winds have slackened in the valleys. Some
valley locations in the central part of the CWA have small
dewpoint depressions so some valley fog development potential
exists though mixing should limit the areal extent.
UPDATE Issued at 830 PM EDT SAT JUL 29 2017
Some cumulus and stratocumulus remain across the region with
drier air having filtered into the far north. Model guidance
continues to suggest that the clouds may linger in some areas
past midnight as drier air continues to filter in as high
pressure builds in. Some valley fog should develop across the
southern part of the area mainly when skies clear. Confidence in
the extent of this remains low at this time. Overall, the
previous forecast was in good shape and only minor adjustments
have been made to hourly grids.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 335 PM EDT SAT JUL 29 2017
19z sfc analysis shows high pressure building into Kentucky from
the northwest. This is bringing in drier air that is helping to
clear the lingering low clouds through the area. It has also
brought a cooler air mass partial responsible for temperatures not
climbing out of the 70s today (along with the extensive cloud
cover for much of the day). North to northeast winds at 5 to 10
mph with some higher gusts also helped to lock in the cool air.
Dewpoints this afternoon varied from the mid 50s north to the low
and mid 60s south. Just recently a few light showers have been
sinking into far eastern Kentucky - as seen on the RLX radar. Do
not expect these to last long, but enough to include in the first
few hours of the forecast grids.
The models are in good agreement aloft with the longwave pattern
for the region through the short term portion of the forecast.
They all depict a fairly deep shortwave trough departing to the
southeast today and into the evening. In the wake of this, heights
will quickly climb with northerly flow and only weak energy
available through the rest of the weekend and into Monday morning.
Given the agreement and general quiet weather will favor a model
blend with a lean toward current radar trends and the higher
resolution HRRR for near term details.
Sensible weather will feature clearing skies this evening, but not
before a few light showers track through our far eastern Kentucky
counties this afternoon. For this, will issue the zones using the
pre-first period option. Otherwise, clear skies and light winds
should make for a good night for radiational cooling, though one
not ideal for ridge to valley differences given the position of
the high`s center well off to the northwest. Nevertheless have
gone with a small to moderate one for low temperatures and hit the
river valleys with some patchy fog by morning - potentially
locally dense. Sunday will feature more sunshine and warmer temps
with highs back into the low 80s most places. Likewise, expect a
bit better conditions for a ridge to valley temperature split
Sunday night as the high settles in a tad closer, but still not
ideal. Patchy fog will again be a concern for the river valleys
heading into Monday morning - locally dense.
Used the CONSShort as a starting point for all the grids through
Monday morning with some point and terrain based adjustments to
temps for tonight and Sunday night. Did end up adding in PoPs for
this afternoon above the CONSShort - otherwise kept them minimal.
.LONG TERM...(Monday through Saturday)
Issued at 350 PM EDT SAT JUL 29 2017
The period is expected to begin with a large area of mid and upper
level ridging from Mexico into the Western Conus and Southern
Plains and troughing from Eastern Canada into the Southeastern
Conus. At the surface, high pressure is expected to be centered
over the Great Lakes and Lower OH Valley regions to start the
period. A colder and drier airmass compared to much of the past
couple of weeks will be in place.
The upper level ridge will become centered over CA and NV by late
Monday into Tuesday with disturbances moving around this ridge and
through the westerlies across southern Canada while weak troughing
remains in place from the MS Valley east. The pattern is expected
to amplify with the ridge building along the US West Coast around
midweek before dampening about a week from now. Downstream of this
ridge, a Central to Eastern Conus trough should deepen as well. At
the same time, the ridge of sfc high pressure will have begun to
move east with return flow returning to the area from mid to late
week. Weaker disturbances should traverse the area at midweek,
Wednesday and combine with daytime heating to bring a return of
chances for convection.
Chances for convection will increase as a stronger shortwave
trough moves into the OH Valley late Thu night into Friday and
then moves east of the area by late Friday night. The axis of the
mid and upper level trough will remain west of the area through
the end of the period. In advance of the shortwave trough moving
through the area from Thursday into Friday night, a cold front
will approach the area on Thursday and then move across the area
Friday into Friday night. Chances for convection will peak as this
boundary moves through the area. Pending instability and
available moisture, a few stronger storms with gusty winds will be
possible, though, locally heavy rain would be the primary threat
from this activity.
Temperatures will begin the period a couple of degrees below
normal for early August with dewpoints mainly in the low to mid
60s. However, by Tuesday into Wednesday as return flow kicks in
temperatures will return to near normal for highs with lows a
couple of degrees below normal. Temperatures will return to below
normal levels with cloud cover and precipitation across the area
on Friday and as a colder and drier airmass begins to filter in on
Saturday remain below normal.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 836 PM EDT SAT JUL 29 2017
VFR cumulus and stratocumulus linger in some locations as high
pressure continues to build into the area. Through 6Z or 8Z, skies
should gradually clear in all locations with some patchy river
valley fog forming towards dawn. At this point, this is not
expected to affect the TAF sites through LAMP guidance does
suggest some MVFR fog at LOZ and SME. LAMP guidance also hit the
fog harder at JKL and SJS, but fog would have to develop in nearby
valleys and lift into both locations. With timing of clearing and
extent of valley fog development uncertain, kept JKL and SJS as
well as SYM VFR. Winds should remain at 10kt or less.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...JP
SHORT TERM...GREIF
LONG TERM...JP
AVIATION...JP
Area Forecast Discussion
National Weather Service Marquette MI
735 PM EDT Sat Jul 29 2017
.SHORT TERM...(This evening through Sunday)
Issued at 404 PM EDT SAT JUL 29 2017
WV imagery and RAP analysis indicated a mid/upper level ridge from
the srn plains into the Great Basin and a trough over the ern CONUS
resulting in downstream nnw flow through the wrn Great Lakes. At the
surface, high pressure remained across the wrn Great Lakes with
light winds and only sct diurnal inland cu across the cwa.
Tonight, a weak shortwave trough over nw ontario may support some
light showers into wrn Lake Superior but are not expected to reach
the Keweenaw before dissipating. With an increase in low level
moisture and favorable radiational cooling tonight, expect some
patchy shallow fog to develop inland. Otherwise, temps will fall off
into the mid to upper 50s.
Sunday, Additional moistening with dewpoints into the low 60s with
temps into the mid 80s should result in MLCAPE values into the 1000-
1500 J/Kg range. Along with the another weak shrtwv moving into the
area, the high res models suggest that lake breeze boundaries cntrl
will provide enough low level conv to help trigger isold/sct
shra/tsra. 0-6km shear values only in the 15-20 knots and high
freezing levels will favor mainly pulse tsra with brief periods of
heavy rain.
.LONG TERM...(Sunday night through Saturday)
Issued at 238 PM EDT SAT JUL 29 2017
Nam shows a 500 mb ridge over the western U.S. and Rockies with a
trough in the ern U.S. 00z Mon. The upper pattern evolves into a
trough across the upper Great Lakes and northern Plains by 00z Wed.
Nam brings in some limited moisture Sun night into Tue along with
weak 850-500 mb q-vector convergence, so slight chance pops cannot
be ruled out anytime especially during peak daytime heating. Best
chance for rain would be Tue afternoon with a weak cold front and
lake breeze convergence occurring along with peak heating and would
be chance pops at best. Did not make too many changes to the going
forecast.
In the extended, GFS and ECMWF show a 500 mb ridge over the western
U.S. 12z Wed with a trough over the upper Great Lakes which remains
into Thu. This trough remains over the area through Sat with sfc
high pressure remaining through Sat. Temperatures will remain below
normal for this forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 735 PM EDT SAT JUL 29 2017
With the exception of patchy shallow fog at KIWD overnight, expect
VFR conditions with lights winds through Sunday morning. Winds will
increase at KCMX in the afternoon ahead of a weak trough crossing
Upper MI. A couple showers and possibly a thunderstorm are expected
to initiate near KSAW by early afternoon before shifting southward
by late afternoon.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 404 PM EDT SAT JUL 29 2017
Winds will remain below 20 knots through the forecast period as high
pressure remains over the area into Wednesday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...07
AVIATION...Kluber
MARINE...JLB
Area Forecast Discussion
National Weather Service Pocatello ID
159 PM MDT Sat Jul 29 2017
.DISCUSSION...Convection underway again this afternoon as weak
shortwave lifts through Great Basin across the region. PWAT
remains around 0.75 inch, and slowly increasing heights also
helping to limit development. Expect main threat to remain over
higher terrain, though still some signs that gusty outflow could
extend south through the Snake Plain from storms that generate
along or near the Divide this afternoon. Have slightly increased
coverage in the northeast corner of the forecast area to account
for this scenario. Otherwise expect upper ridge to continue to
slowly build across the region over the next several days.
Temperatures continue to warm with slowly decreasing moisture so
expect convective potential to decrease through the rest of the
weekend into early next week. Trend continues in amplifying ridge
axis through mid week, but mainly west of East Idaho. This keeps
this area under more of a north-westerly influence, with
temperatures not looking as warm later in the week as previously
expected. Still thinking only a few degree shift either way, with
lower elevation highs Wed-Sat remaining well into the 90s. Ridge
axis expected to shift east over Idaho next weekend as Pacific
energy shifts inland and shortwave tries to flatten the ridge.
Overall, only a few minor tweaks associated with this forecast
package from previous thinking. DMH
&&
.AVIATION...
Main forecast change was to add VCSH/VCTS to KSUN 18Z-05Z, and VCTS
to KDIJ 20Z-04Z. Model consensus paints isolated activity close to
both terminals, and both have already seen nearby showers/storms
over the past 2 hours. Models keep KBYI/KPIH/KIDA dry. Confidence in
precip forecast is moderate. Winds today will be very light
(<=10kts), but as always, gusty/erratic (and difficult to forecast
in advance) outflow winds will be possible near t-storms. One item
worth mentioning...the HRRR for several runs now wants to generate
significant outflow winds from supposed future storms in
Jefferson/Clark/Fremont counties, and rapidly send them SW down the
Snake Plain as a consolidated outflow boundary. Model places 30-40kt
gusts at KDIJ/KIDA between 2330z and 0100z, and KPIH between 0130z
and 0300z. Frankly I don`t trust this scenario. This outflow is
completely dependent on convection occurring in the counties
mentioned of sufficient intensity to generate these winds, and
despite consistency over several runs, the HRRR has not been perfect
with placement/timing of initial storms firing this afternoon. Have
left this scenario out of the TAFs and will closely monitor.
Activity dies after sunset, with very similar scenario Sun. VFR
conditions expected both days all terminals. - KSmith/DMH
&&
.FIRE WEATHER...Isolated thunderstorms forecast in parts of
Eastern Idaho, particularly across the Targhee NF areas this
evening. A chance for thunderstorms is also forecast in the Central
Mountains this evening. Weak high pressure will be in place over SE
Idaho which will build tomorrow and Monday. Temperatures will thus
rise and drier conditions are expected. Critically dry conditions
during the day is expected for most of Southern Idaho and portions
of South Central areas. Eastern Idaho is expected to be above 20% RH
values at their minimum. Afternoon thunderstorm thunderstorms will
once again be possible Sunday along mountain ridges. Other than
outflow winds associated with thunderstorms, winds will not be a
concern throughout the forecast period. NP/DMH
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Tucson AZ
203 PM MST Sat Jul 29 2017
.SYNOPSIS...An elevated risk of thunderstorms will continue
this weekend with locally heavy rain and strong winds with some
storms. High temperatures will generally be a few degrees below
normal due to the rainfall coverage again Sunday and Monday. The
weather pattern will remain favorable for daily thunderstorms this
coming week.
&&
.DISCUSSION...The morning upper-air sounding at Tucson showed a
very moist air mass in place, with a much weaker steering flow and
less vertical wind shear compared to yesterday. A couple of large-
scale features in play this weekend with the GOES-16 mid and upper
level water vapor imagery depicting two westward tracking upper
lows. One exiting the Texas Big Bend and the other over the southern
tip of Baja which will influence the upper level flow pattern today
and tomorrow. The latest 19Z HRRR solution focused most of the
rainfall across Pima, Santa Cruz, and Cochise counties through later
this evening. This was in good agreement with the current activity
late this morning and early this afternoon. Based on the weaker
steering flow and abundant moisture, flash flooding will continue to
be the main concern through this evening and likely again Sunday.
The overall flow pattern will remain favorable for daily showers and
thunderstorms, although a decreasing trend in rain chances after
this weekend. Daytime temperatures will warm a few degrees to more
normal readings starting Tuesday with the decrease in rainfall
coverage.
&&
.AVIATION...Valid thru 30/18Z.
Scattered to numerous TSRA/SHRA through later this evening. Brief
MVFR/IFR conditions likely in/near TSRA this afternoon and evening.
SFC wind variable in direction mainly less than 12 kts, except in
the vicinity of TSRA where gusts may exceed 40 kts. Aviation
discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Daily shower and thunderstorm chances will continue
into next week across most of southeast Arizona. Elevated humidities
will remain in place through the weekend into next week. Outside of
thunderstorm winds, expect 20-foot winds to remain at or below 15
mph and follow typical upslope/down valley diurnal patterns. Fire
weather concerns are low through at least late next week.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
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