Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/01/18
Area Forecast Discussion
National Weather Service La Crosse WI
637 PM CDT Fri Aug 31 2018
.SHORT TERM...(This evening through Saturday night)
Issued at 238 PM CDT Fri Aug 31 2018
Still lots of unknowns in the forecast but short range models are
starting to give a somewhat clearer picture of what is expected to
occur. Early this afternoon there was a cold front from extreme
northwest Minnesota into North Dakota. A stationary front was
parked across central Missouri into northern Kansas. While both of
these features will be a player for the area, the front over
Missouri is expected to be more relevant as it lifts back north as
a warm front.
Water vapor satellite showing a weak short wave trough embedded in
the mean long wave trough over eastern Montana. This wave will
push east tonight and stay to the north while pushing the cold
front southeast across Minnesota. Showers and storms already
starting to develop across northwest Minnesota ahead of this
system and these will drop southeast toward the area this evening.
This activity is not expected to be near the area until about the
middle of the evening with the best chances expected to be across
the north closer to the short wave trough.
By late this evening and into the overnight, the front across
Missouri will start to lift back to the north into Iowa. However,
not sure how far north it will make it as it is currently be held
back by ongoing convection just north of it. It may not move much
until the low level jet kicks in late this evening. If the front
can get back into southern or central Iowa, a round of showers and
storms will develop along and north of it as the low level jet
runs into the boundary. There is also a short wave trough coming
across Nebraska that will provide additional forcing for the
showers and storms to develop. Looking at several runs of the RAP
and the 31.12Z NAM, the mid level frontogenesis in the 850-700 mb
layer looks to be focused right into the southern sections of the
forecast area. Expecting to see rapid growth of showers and storms
north of this boundary during the late evening into the early
overnight with this activity then persisting into Saturday morning
before diminishing as the low level jet veers off to the east and
weakens. The main threat from this activity will be the heavy
rain/flooding potential, see the hydrology section below for more
details. Some potential for large hail and damaging winds early in
the storm cycle until a transition over to mainly heavy rain
occurs overnight. The ML CAPE pool looks to primarily stay along
and west of the Mississippi River and into southwest Wisconsin and
looks to be in the 1000-2000 J/Kg range. The shear looks to
primarily be in the 0-3 km layer and on the order of 20 to 25
knots. The 0-1 km shear will increase as the low level jet forms
develops but this doesn`t look to come into play as the storms
should be elevated above this layer north of the boundary. This
will leave some large hail and damaging winds then as the main
threats outside of the heavy rain.
The boundary will still be hanging around the area through
Saturday night with the continued threat of showers and storms
across the southern sections of the area.
.LONG TERM...(Sunday through Friday)
Issued at 238 PM CDT Fri Aug 31 2018
An active period is expected with a continued heavy rain threat
through much of the week. A large mid/upper ridge will remain
anchored across the Mid-Atlantic region with west to southwest flow
aloft upstream over the Midwest. Various embedded shortwaves will
translate through the flow to produce occasional rounds of showers
and storms. The atmosphere will remain conducive to heavy rainfall
with precipitable water values exceeding 2.0 inches at times,
corresponding to +2 to 3 standard anomalies via the NAEFS. Mesoscale
details concerning surface boundary/upper wave placement and
consequently convective focus are uncertain, especially given the
messy surface pattern and potential contamination from storm
outflow. However, the overall pattern certainly suggests a heavy
rain/flood threat will continue during this time. Not expecting much
change in airmass through the week, with highs in the 70s to low
80s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 637 PM CDT Fri Aug 31 2018
A quiet evening underway out there, and expecting that to continue
through at least 06Z with just some passing thicker mid and high
clouds at times as winds gradually subside from their earlier
gustiness. Still not the clearest picture of how far north showers
and storms will develop later tonight, but given the setup and
best moisture arriving just south of the area, starting to think
LSE and RST may escape much in the way of any showers and storms,
though of course will be watching trends closely through the
evening. Some increase in moisture later tonight should again
allow for some MVFR/IFR stratus to develop, similar to last
night, though thinking this will be later given current trends and
not sure just how widespread it will be. Nevertheless, whatever
forms may stick around longer into Saturday morning (at least)
with much weaker wind flow in place as compared to this morning.
Any risk for showers and storms for LSE and RST should taper off
by mid to late morning, with any stratus likely to gradually
scatter out through the afternoon hours.
&&
.HYDROLOGY...
Issued at 238 PM CDT Fri Aug 31 2018
Will be issuing a flash flood watch for southwest Wisconsin into
northeast Iowa for tonight into Saturday. As noted above, as the
boundary lifts back north, rapid development of showers and storms
expected late this evening as the low level jet impinges on this
boundary. The precipitable water values will increase to around 2
inches near the boundary with warm cloud depths of 4 to 4.5 km.
Expecting the storms to be very efficient rain producers and
included a band of close to two inches of rainfall centered
roughly along the Wisconsin River in southwest Wisconsin and
expecting that localized amounts will be higher than this. Some of
this rain will fall on areas that are already dealing with
saturated ground and flooding from the rain earlier in the week
and cannot take much more water. For northeast Iowa into Grant
County, the ground is not as saturated but terrain is a concern
and this area known for mud slides with heavy rain. For now, will
include the areas where confidence is highest for a flash flooding
threat but the location of the boundary will have to be closely
monitored through the evening for possible adjustments to the
watch area.
Flooding continues along the Kickapoo River, but for the time
being, levels are going down. For more details see the latest
flood statement.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Flash Flood Watch from 10 PM CDT this evening through Saturday
evening for WIZ053>055-061.
MN...None.
IA...Flash Flood Watch from 10 PM CDT this evening through Saturday
evening for IAZ011-030.
&&
$$
SHORT TERM...04
LONG TERM...JM
AVIATION...Lawrence
HYDROLOGY...04
Area Forecast Discussion
National Weather Service Hastings NE
857 PM CDT Fri Aug 31 2018
.UPDATE...
Issued at 856 PM CDT Fri Aug 31 2018
A few thoughts regarding the rest of tonight (through sunrise):
Be prepared to hear/read this a LOT over the next several days,
but we are in the midst of a very tricky/challenging weather
pattern as far as predicting the "exact" timing and likelihood of
rain/thunderstorm activity.
Focusing solely on the rest of tonight, the very basic/general
story is that there will be a gradual increase in
shower/thunderstorm activity as the night goes on, as the coverage
of mostly-sub-severe storms continues to increase off to our west
over western NE/KS as of this writing. With time, some of this
activity will spread east into our coverage area (CWA), with
additional "new" storm development possible overhead. As noted by
preceding day-shifter, forcing is not particularly strong, but
the presence of a series of weak waves moving in from the west
should be sufficient to generate at least isolated-to-scattered
activity. Did not have the confidence to advertise "likely" 60+
percent rain chances/PoPs into any particular area overnight, but
did make some modest 10-20 percent increases in PoPs across
especially our northern half versus previous forecast. The vast
majority of storms should not be severe tonight, but agree with
SPC in maintaining a broad Marginal Risk to account for the
possibility of some marginally severe hail and (perhaps to a
slightly-lesser extent) wind. Will defer to upcoming night shift
to modify the going forecast for Saturday daytime and beyond.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 330 PM CDT Fri Aug 31 2018
Aloft: RAP dynamic tropopause animations...aircraft data and WV
imagery showed low-amplitude WSW flow over most of the CONUS with
the mean longwave trof axis from Sask down thru the Pac NW. There
is a small low over Nrn CA/NV. This low will open up as it heads E
across NV into UT tonight into tomorrow. This will result in more
of a pronounced Wrn trof by 00Z/Sun that will extend from MT to
AZ/NM.
Surface: A weak low was analyzed over SD with a weak cool front
extending WSW thru the Neb panhandle into WY-UT-NV. A sfc trof
extended S thru Cntrl Neb into Wrn KS. The low will fill with the
front sagging SE into the CWA tonight. This front will be just E
and S of the CWA by 00Z/Sun and cont to weaken. Meanwhile...very
weak high pres will settle over Neb tomorrow.
Rest of this afternoon: Hot. Humid over S-cntrl Neb. The KSU
mesonet site near Beloit hit 102F early this afternoon. 100F at
Jewell. With this cirrostratus moving thru N-cntrl KS now per IR
satellite...those locations probably won`t get any hotter.
The atms should remain capped in the wake of this AM`s tstm
activity which produced a lot of vivid CG strikes.
Tonight: Increasing clds as svrl CAMs and the HRRRX ensemble
suggest sct tstms will move thru mainly after 10 PM. SPC has a
MRGL risk for svr and it seems reasonable given the MUCAPE from
the 09Z SREF is fcst btwn 1500-3000 J/kg. Effective deep lyr shr
will be 30-40 kt. While a shortwave trof is not fcst to move
thru...the RRQ of an 85 kt jet streak over MN will move over the
Cntrl Plns.
It will be another warm/muggy night.
Sat: Any tstms lingering at dawn should exit the CWA to the E
during the AM. With the front bisecting the CWA most of the
day...can`t rule out an isolated shwr or two developing at any
time...but much of the daytime hrs should be dry. By 4 PM sct
tstms should develop with the greatest chance near the front (from
N-cntrl KS to near HJH).
SREF MLCAPE is fcst btwn 2000-2500 J/kg with effective shear near
40 kt. 0-3 km SRH is fcst 150-200 m2/s2. So while the primary
convective mode should be multicell...a supercell or two can`t be
ruled out.
Temps will drop back to near normal behind the front...but it
will still be humid.
.LONG TERM...(Saturday night through Friday)
Issued at 330 PM CDT Fri Aug 31 2018
Aloft: A longwave trof will remain over the Wrn USA with a
subtropical high over the E. Early week will be more amplified
with SW flow over the Cntrl Plns. Mid-late week will be more WSW.
Multiple low-amplitude shortwave trofs will exit the Wrn trof.
Surface: Another weak cool front will move into the CWA Sun. That
front will dissipate Mon with a stronger front fcst to arrive Wed.
High pres will briefly move in Thu then it`s back to the warm
sector Thu-Fri.
Temps: Highs will be near or a little cooler than normal. Lows
will be warmer than normal.
Rain: It could be heavy. WPC has SLGT risk of excessive rainfall
Sat and Sun due to potential for repeated tstm development.
Sat eve/night could be quite active as sct tstms will be on-
going over the SE 1/3 of the CWA. Other storms could be moving in
from the W...and other storms could develop over the CWA as the
low-lvl jet ascends above the remnants of the weak front.
There are no dry periods in the fcst. There will be at least a
chance for tstms every day...the way it`s currently looking. Some
chances will be better than others...but predictability is low
with tstm development tied to low-amplitude shortwave trofs. The
last 4 operational EC runs are outputting an average of 2" of rain
across the entire CWA over the next 10 days...with potential for
some areas E of Hwy 281 to receive as much as 4-6".
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday)
Issued at 714 PM CDT Fri Aug 31 2018
General overview:
This is going to be a tricky/challenging period with regard to
especially the potential and timing of thunderstorms. As for
ceiling and visibility, have officially advertised VFR through the
period for now, but this is also no guarantee, as at least brief
MVFR ceiling and/or visibility could materialize, either
associated with convection or perhaps not. Wind-wise, assuming no
pronounced thunderstorm-related influences (outflow), sustained
speeds should average near/below 10KT the vast majority of the
time, with direction generally somewhere between northerly and
east-southeasterly. Read on for more element-specific details...
Rain/thunderstorm potential:
Honestly, the only high-confidence in this forecast is these first
5-6 hours, as both terminals should manage to stay storm-free
through then. However, anytime after that, there is JUST enough of
a chance for convection in the general area that have decided to
blanket the majority of the period with a basic "vicinity
thunderstorm" (VCTS) mention. Do not normally like to run with
VCTS so many consecutive hours, as there will likely be some
"breaks in the action" so to speak. However, these "breaks" are
looking difficult to pin down, with various forecast models
showing the potential for showers/storms at almost any point
between late this evening and late Saturday afternoon. Hopefully
later forecasts can better pin down details. It`s also worth
noting that there will be at least limited potential for a severe
storm with hail/strong winds.
Ceiling/visibility:
While the majority of models/guidance suggest prevailing VFR, and
have advertised as such for these TAFs, there are at least 3
caveats that bear watching: 1) Obviously any localized
thunderstorm activity could briefly promote sub-VFR
conditions...2) There appears to be at least limited potential for
an intermittent low-end MVFR ceiling especially beyond the first 9
hours...3) There could be some light fog potential late tonight
into Saturday morning (especially if thunderstorm activity is
minimal), and have "hinted" at this with a "6SM BR" mention
between 06-15Z.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
UPDATE...Pfannkuch
SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1103 PM CDT Fri Aug 31 2018
.UPDATE...
Short term grids adjusted to match ongoing temperature/moisture/rainfall
behavior. Expecting a quiet early morning start to the holiday
weekend with coastal showers beginning to fester up once again
just before sunrise. As has been the case the past couple of days,
early day near coastal showers will move across the first two
tier coastal counties before noon...more isolated shower or storm
activity may reach further inland once mid to upper 80 F convective
temperatures are met. As we travel further into the weekend, an
upper level inverted trough moving westward towards the upper
Texas coastline will increase areawide rain. Increasing moisture
levels will also spike Sunday and Monday`s rainfall probabilities.
Some high resolution guidance are becoming more aggressive with
their QPF mass fields...particularly on Sunday. Best to have an
indoor Plan B in place for any Sunday or Labor Day outdoor activities.
31
&&
.PREV DISCUSSION... /ISSUED 629 PM CDT Fri Aug 31 2018/
AVIATION...
Iso shra should taper off with the loss of heating this evening.
The next 24 hours looks fairly similar to the past, so will be
going w/ a fcst of persistence: mclear to partly cloudy
overnight, scattered shra/tstms developing near the coast toward
sunrise, then some developing inland during the day w/ heating.
VFR conditions should persist outside of any convection. 47
&&
PREV DISCUSSION... /ISSUED 358 PM CDT Fri Aug 31 2018/
Overall there has not been nearly as much convection today as the
last couple of days. There is still enough moisture along the
coast to support at least some isolated storms along the US59/I-69
corridor between Sugar Land and Victoria. Short range model
guidance has been decent with resolving this convection. There is
also some convection developing along the Harris/Montgomery Co
line which the HRRR has also resolved. Going with these trends in
the near term forecast look good going forward. The main issues
for not having more convection deal with the overall upper level
pattern and gradient in higher moisture to the east and along the
coast. Upper level analysis shows that the upper level ridge has
moved more over the Red River with 500mb temperatures increasing
from -7C to -5C. That might not seem like a lot but it does
signify more stability aloft and possible subsidence from the
ridge. Also noted in upper level analysis is the inverted
trough/tropical wave off the Louisiana coast. This should be the
system to affect SE Texas Sunday and Monday.
The forecast next week is really the story of two tropical waves.
The first as noted above will be moving into the area Sunday into
Monday. Precipitable water values increase to around 2 to 2.3
inches over the weekend and remain there into Monday. The NAM
increases PWAT values closer to 2.5 inches but based on current
trends in the GOES 16 PWAT imagery that might be overdone. The NAM
also produces quite a bit more rainfall on Monday due to this.
This trend in the NAM is something to put away back in our minds
but the forecast will lean more on the GFS/ECMWF solutions.
Rainfall amounts over the weekend look to be anywhere from 0 to 3
or 4 inches on the high end and those higher totals will be
isolated like we saw on Wednesday. Labor day weekend may not be a
complete washout but with the trends in the models the odds of a
washout look to be going higher. As such we have also increased
rain chances for Sunday and Monday based on the higher moisture
and the upper level trough/tropical wave moving over the region
during this time.
Finally there is the tropical wave/invert trough aloft over
Hispaniola that has been the subject of future tropical cyclone
development in the eastern Gulf by next Monday through Wednesday.
Most models are taking this trough/tropical wave towards Louisiana
Wednesday and then westward towards SE Texas Thursday into
Friday. The track will largely depend upon the strength of the
upper level ridge to its north and if that ridge expands west
towards the Midwest. This development of the ridge will likely
steer the system more on a westward track rather than turning the
system north. The main impacts from this system so far should be
higher thunderstorm chances. None of the models are showing the
development of a tropical system but conditions should be more
favorable late next week that this system deserves monitoring
through the weekend and early next week. Mainly Gulf waters are
well warm to say the least but forecast data differ on 250mb winds
which would determine how much shear would affect the system.
These kinds of details will need to be watched but still way too
soon to speculate on the nature of tropical development with this
system. Bottom line is to just keep track of NHC outlooks and
monitor forecast trends. 39
MARINE...
Generally light to occasionally moderate E/SE winds are expected
to prevail through the weekend...and into the first part of next
week. This pattern is courtesy of broad high pressure over the
east coast and a low pressure system slowly moving across the
Northern Plains. However, winds/seas will be higher in and near
the scattered storms that are expected to develop over the coastal
waters these next few days. The unsettled weather pattern (from
weak disturbances embedded withing the easterly flow aloft and
deeper Gulf moisture) should remain in place through the forecast
cycle. The better rain chances are expected during overnight/early
morning hours. 41
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 75 95 75 93 74 / 10 20 10 40 40
Houston (IAH) 76 91 76 89 76 / 10 40 40 60 50
Galveston (GLS) 81 90 80 88 81 / 20 50 60 70 50
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&
$$
Discussion...31
Area Forecast Discussion
National Weather Service Lincoln IL
1051 PM CDT Fri Aug 31 2018
.UPDATE...
Issued at 835 PM CDT Fri Aug 31 2018
We still have some isolated showers and storms around the
forecast area this evening with one area mainly east of I-57
tracking to the north. A second area of weakening showers was over
west central IL, and they were tracking to the east. The latest
HRRR continues to show a weakening trend with both areas this
evening with our attention turning towards west central Iowa on
the nose of a 50 kt low level jet and some decent 850 mb moisture
transport later this evening which should produce stronger
convection overnight to our west, eventually making its way into
our area by morning in a weakening state.
The outflow boundary from the Iowa MCS will provide a focus for
additional thunderstorms to develop tomorrow afternoon. However,
the main question is where that will be as models are not exactly
depicting one location for storms to develop later tomorrow,
although the trend over the past few runs has been hinting at
areas to our north. Another very warm and humid day in store for
the area, in fact, there will be little change in the forecast
into a good portion of next week as an upper level ridge builds
west across the Midwest, which would tend to shift the better storm
threat further to our west and north with time. This pattern should
keep afternoon temperatures well above normal for the first week
in September with daytime highs well into the 80s, possibly the
low 90s in a few locations, which will drive heat index values
into the mid to upper 90s through at least Wednesday.
Have made some adjustments to the POPs for the overnight hours
along with some tweaks to the early evening temperatures. We
should have the updated ZFP out by 9 pm.
&&
.SHORT TERM...(This evening through Saturday)
ISSUED AT 313 PM CDT Fri Aug 31 2018
500 mb map dominated by a weak trough over the western coastal
states, and a general southwesterly flow pattern from the desert
SW into the Great Lakes. Central IL is on the edge of the more
progressive flow, and with a high pressure ridge situated along
the eastern coast of the CONUS, southerly flow is keeping the warm
and humid air moving into the region. That southerly flow and
plenty of warm air in the mid levels will keep tonights lows near
70/lower 70s in most areas. The warm the temperatures will
continue tomorrow, warming considerably over todays highs, and
starting another hot stretch of the forecast, through the weekend
and into next week. With temperatures very warm, and plenty of low
level moisture, and the ridge axis well off to the east, the
boundary layer is vulnerable to the forcing of outflows from
surrounding areas. This afternoon, the showers and thunderstorms
are confined to the southeast, as well as to the west of the
Mississippi River Valley. Minor pops are in place for areas
southeast of Interstate 70, and NW of the IL River to cover
potential development in those areas...with the northeast getting
an assist going into tomorrow from an approaching weak boundary.
.LONG TERM...(Saturday night through Friday)
ISSUED AT 313 PM CDT Fri Aug 31 2018
Forecast blend having a hard time resolving the approach of a weak
boundary and the southerly extent of the showers associated with
that boundary, given that Central IL is caught between the more
southwesterly flow aloft, and a building upper ridge over the
southeastern portion of the country. Low chance pops are more
widespread on Sunday, then retreat with the better chances west of
I-55. However, until a forecast pattern changes, the region will
likely see a lot of chance pops (particularly diurnal enhanced
showers/thunderstorms) until the hot and humid boundary layer
either moves out, or dries out. After midweek, the chance pops
become the norm instead of the exception for just that reason. The
same stagnation of pattern also means that the heat is here for
the duration of the forecast. And with temps in the upper 80s/low
90s, and dewpoints surging into the low 70s...the nights through
next week do not drop below the lower 70s, and the max heat
indexes are back in the mid to upper 90s.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1045 PM CDT Fri Aug 31 2018
The main forecast concern will be timing of storms into our
northern TAF areas Saturday morning as convection was slowly
beginning to develop over west central Iowa late this evening.
Outside any thunderstorm, we expect VFR conditions through this
forecast period. The CAM models have done a poor job with respect
to the isolated convection across east and southeast Illinois
this evening as well as with a secondary disturbance which brought
in some scattered showers to the west early in the evening.
However, with the stronger forcing event starting to occur west
of the Missouri River late this evening, thanks to the increasing
850 mb moisture transport/convergence and low level jet, short
term high resolution models seem to be handling things well with
convection developing across southwest through west central Iowa.
It then tracks the storms east and a little north of east overnight
with a suttle shift east and then finally southeast as the storms
become primarily outflow dominant. This should bring at least
VCTS to PIA and BMI in the 12-15z time frame.
This outflow boundary will be the key for any redevelopment late
in the afternoon, and once again, the favored areas will be PIA
and BMI, but again, this far out, will handle with a VCTS during
the time frame redevelopment is expected. Otherwise, scattered to
broken cumulus will develop again by early afternoon and then
quickly dissipate just after sunset. Southeast to south winds
tonight at 8 to 13 kts will be south on Saturday at speeds of 10
to 15 kts with a few gusts near 20 kts at times in the afternoon.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Smith
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...Smith
Area Forecast Discussion
National Weather Service Key West FL
946 PM EDT Fri Aug 31 2018
.CURRENTLY...
Shower and thunderstorm activity has decreased over the early
evening hours. A few showers with embedded thunderstorms can be
found in the eastern straits, and showers and storms in the Gulf
waters south and west of the lower Keys. The evening Key West sounding
again found ample conditional instability with abundant MLCape.
Although the PW is still over 2 inches the mid-level RH values
are slightly lower than the past several evenings, and lower
tropospheric lapse rates are not impressive. Upper level winds
have shifted more out of the northwest from northerly earlier, so
the lower Keys are no longer under the thick cirrus seen earlier
today. However, the upper Keys are still shrouded in cirrus from
storms in the Gulf. Easterlies dominate from the surface through
20 kft, indicating the depth of the ridge.
.SHORT TERM...
Guidance analysis finds the mid-levels continuing to dry slightly,
with the RAP indicating RH percentages in the convective layer
(700-500mb) dropping into the 40s by Friday afternoon. The
relatively drier mid-level air is moving through in advance of the
tropical wave expected to traverse the area on Labor Day. Overall
MOS guidance does reflect the above with lower precipitation
chances (near climo) than previous runs for Friday and Friday
night. Additonally, the HRRR and the Key West local WRF are not
very bullish on widespread precipitation coverage overnight and
tomorrow. The pops currently advertised for the next 24hrs may be
slightly overdone, but are in chance category which is probably
appropriate.
&&
.MARINE...
Gentle to moderate easterly breezes can be expected overnight and
Friday morning over Hawk Channel and the Florida Straits, with
gentle easterly breezes expected over the Gulf and Florida Bay.
Thunderstorm and shower coverage will be isolated. Storms that do
develop will be moving towards the west northwest between 15 and
20 knots. Winds in the vicinity of thunderstorms could gust near
25 knots.
&&
.AVIATION...
VFR conditions to prevail at both terminals with a few showers in
the vicinity this evening. East-southeast winds should settle
around 10 knots tonight, becoming gusty again tomorrow. Short term
trends and high resolution models suggest a mainly quiet night,
with convective coverage perhaps ramping up again by mid-morning.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...Devanas
Aviation/Nowcasts....CLR
Data Collection......SD
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Area Forecast Discussion
National Weather Service Midland/Odessa TX
602 PM CDT Fri Aug 31 2018
.DISCUSSION...
See aviation discussion below.
&&
.AVIATION...
VFR conditions are expected at the west Texas and southeast New
Mexico terminals the next 24 hours under mostly clear skies.
Any thunderstorm activity should remain in the mountains.
12
&&
.PREV DISCUSSION... /issued 308 PM CDT Fri Aug 31 2018/
DISCUSSION...As of 3:00 PM CDT Friday...after I looked at the
models I had to rub my eyes a couple of times and find my glasses.
Could it be true? Yes...rain and cooler temps are in store for
the latter part of the holiday weekend and thru most of the
upcoming week! A very nice respite from the interminable heat we
have been experiencing for months and months and months. Now on to
the fun details!
KMAF radar is showing a few storms popping up in the Davis and
Guadalupe Mtns...likely due to the intense heating...moisture...
and upslope flow. Even though the HRRR doesn`t have a good handle
of the current conditions the high resolution NAM Nest CAM model
is doing well. Simple Water Vapor RBG imagery shows the ridge
centered over North Texas stretching east to the Atlantic. Any
storms will dissipate overnight.
The long awaited (seems like many months) and welcome pattern
change begins this weekend as the westerlies make their way south.
Due to the large scale (synoptic) pattern change have mainly
followed the ECMWF. On Saturday the ridge center shifts to the
NC/VA coast as a trof deepens over the Rockies. It will still be
hot on Sat as the H85 thermal ridge edges closer. Slt chc/chc pops
will spread slowly east thru Sat night...mainly over the mountains
but moving further into the adjacent Plains as lift increases. On
Sunday the ridge moves off the mid Atlantic coast as the trof
deepens in the Rockies and edges into the Plains. Lift ahead of
the trof and subtropical moisture being advected into the area
will lead to a chance of thunderstorms across the area.
Most...if not all of next week looks wet with high temps in the
80s! The basic pattern will be a trof over the Western US with a
ridge over the Eastern US. A continuous feed of deep subtropical
moisture and impulses traveling out of Mexico will keep
showers/thunderstorms in the forecast thru the week. The ridge
starts to build west from the mid Atlantic into the Central Plains
by Thursday morning leaving the CWA in a deep moist southeasterly
flow. What is interesting to see...and this can change a number
of times...is that the ECMWF takes the weak tropical wave that is
near Hispaniola into the Gulf of Mexico and moves it west. If
this does verify it could add to the deep moisture over the area
and enhance the rainfall. The ridge center remains north of the
CWA allowing inverted trofs to move west over the CWA for a
continuation of the wet weather along with comfortable temps.
Bottom line is that it looks like a wet week ahead. Did consider a
Flash Flood Watch starting Sunday Night/Labor Day...but as of now
it seems like the the heavier rain will occur Tuesday thru
Thursday. The overnight shift will review the necessity of a
Watch. Will continue with the Special Weather Statement for now.
Strobin
&&
.PRELIMINARY POINT TEMPS/POPS...
Big Spring 74 97 74 93 / 10 10 10 20
Carlsbad 70 96 68 90 / 10 40 50 40
Dryden 74 98 74 95 / 10 10 0 30
Fort Stockton 71 97 72 91 / 10 10 10 40
Guadalupe Pass 67 89 65 84 / 20 30 50 40
Hobbs 68 91 66 86 / 10 10 50 30
Marfa 60 88 61 84 / 10 20 20 50
Midland Intl Airport 73 97 73 92 / 10 10 10 30
Odessa 73 96 73 91 / 10 10 10 30
Wink 72 99 73 92 / 10 10 30 40
&&
.MAF WATCHES/WARNINGS/ADVISORIES...
NM...None.
TX...None.
&&
$$
84/33
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
731 PM CDT Fri Aug 31 2018
.SHORT TERM...(This evening through Saturday)
Issued at 405 PM CDT Fri Aug 31 2018
It`s looking more and more likely that scenario 1 from this mornings
discussion will be playing out tonight, which is a split setup with
the local area between better upper forcing to the north and better
LLJ forcing to the south. This leaves us with very little forcing in
between. We see this split setup with the most recent Day1 outlook
from the SPC and have started pulling back on PoPs.
This afternoon, satellite imagery shows plenty of accas moving
across the area with steep mid-level lapse rates and broad
waa/isentropic lift. To this point none of this activity has been
able to tap into the instability in place (about 3k j/kg of muCAPE)
as it is riding above the instability. However, we are seeing a few
drops reach the ground from this activity and you can`t rule out one
our two storms managing to form out of the accas, so had to spread
some 20 pops across much of the area this afternoon as this accas
works through, but we aren`t expecting anything widespread or well
organized to develop.
Where convection has developed just before 3pm was just west of I-29
on the ND/SD border. The HRRR did a decent job in pegging this
(though the HRRR was a little late in initiating it), and agree with
the HRRR and the other CAMS that this activity will follow the h85-
h3 thickness pattern (mean flow) ENE toward DLH, just grazing our
northern CWA. This activity will pose the greatest severe risk, with
wind and hail being the main threat.
Also showing up nicely on satellite is a strong shortwave coming out
of Colorado. This wave will move into the central Plains this
evening, exciting a strengthening of the LLJ this evening down by
Omaha that will move across IA overnight. This should initiate
widespread convection with torrential rainfall across Iowa into
southern WI. The main question with this LLJ forced activity is how
far north does it develop. We are seeing from the HRRR/NMM/ARW that
it may sneak up to I-90.
So what does that leave us in between? Broad WAA with associated
weak isentropic lift. There really isn`t any forcing mechanism that
looks to focus activity in the MPX area (unless the Iowa activity
makes it to I-90), which means we get isolated to scattered storms
depending on where we get enough forcing to break through the cap.
In all likelihood, our QPF is way overdone and spreadout with the
widespread 3/4ths to 1 inch of QPF east of a STC/MKT line. Instead,
we`ll see a few streaks with amounts like this or even better, but
it`s tough to pin down where any of those streaks will end up at
this point.
For Saturday the best moisture transport shifts south, aligning from
KC toward Milwaukee, so the precip focus shifts southeast of the MPX
area. This will give us a dry day, though with the tropical
dewpoints not really leaving the area, it will be muggy and we`ll
likely hold on to a bit more cloud cover than we were previously
expecting.
.LONG TERM...(Saturday night through Friday)
Issued at 405 PM CDT Fri Aug 31 2018
The long term period can be characterized by an active and stagnant
weather pattern in which a broad trough/zonal pattern across the
western CONUS will place us in southwesterly flow which will bring
repeat rounds of shortwave energy through the Midwest. Additionally,
a frontal boundary will linger, wavering slightly northward and
southward with time, across the region which will provide a focus of
low level lift with moisture pooling along the front, leading to
repeat thunderstorm opportunities.
Saturday night and Sunday...this period will start out rather
quiet with all of the thunderstorm activity expected in the
vicinity of the frontal boundary to our south. There are some
differences for the forecast for Sunday, but the GFS is showing a
shortwave lifting northeast from Nebraska, leading to showers and
storms across our area. The EC keeps most of this activity farther
south, more closely tied to the frontal boundary. Pops were raised
to the around 50 percent for much of the area Sunday.
Sunday night through early next week...A fairly stagnant evolution
of the pattern and hence the front across Iowa, southern MN and
into WI is expected during this period. Ample moisture and
instability will remain pooled along this front which will start
out just to our south, but slowly lift northward Monday into
Tuesday. Each night will bring more rounds of thunderstorms along
the front as the nocturnal low level jet increases. Hence, the WPC
has QPF values on the order of 3+ inches over the next 7 days
across a fairly widespread area, which is reasonable. There will
no doubt be higher amounts on an isolated basis through the
period. The guidance does suggest a reprieve comes Wednesday as
dry high pressure drops in from our south and pushes the frontal
boundary south of the area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 731 PM CDT Fri Aug 31 2018
Most of the area is indeed in the middle of a split scenario
tonight with thunderstorms. There will be storms this evening from
northeast into portions of east central MN and adjacent WI, with
the best forcing associated with the upper jet across northern
MN. Meanwhile there may be storms later tonight from southeast MN
into WI associated with the low level jet and warm air advection.
In between, just some scattered showers and maybe an isolated
storm.
Otherwise, MVFR ceilings are possible late tonight in eastern MN
into WI, and possibly IFR ceilings as well.
KMSP...a few light showers are possible this evening around the
airfield, but it is unlikely there will be any thunder tonight
within 50 nautical miles, as best forcing remains well north and
south of KMSP. Having said that, with some instability and weak
warm advection, one cannot completely rule out seeing a brief TS,
though we are not really seeing a threat for anything organized
impacting the Twin Cities. Also, there should be abundant stratus
toward morning with plenty of moisture along the weak boundary.
/OUTLOOK FOR KMSP/
Sun...VFR. Chc TSRA. Wind S at 5 kts.
Mon...MVFR/IFR with -SHRA/TSRA possible. Wind E at 10G15 kts.
TUE...VFR. Chc TSRA. Wind SW 10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...MPG
LONG TERM...SPD
AVIATION...TDK
Area Forecast Discussion
National Weather Service Tucson AZ
209 PM MST Fri Aug 31 2018
.SYNOPSIS...
A brief return to the monsoon can be expected this weekend, with a
return of moisture to southern Arizona. The best chances for
isolated to scattered showers and thunderstorms can be expected
mainly from Tucson eastward to the New Mexico border.
&&
.DISCUSSION...
Clear skies this morning led to quick warm up around the region,
priming the atmosphere for convective initiation off the
Chiricahua Mountains this early this afternoon. This is in line
with earlier HRRR and U of A WRF solutions.
Looking at satellite imagery, an upper level trough can be seen
digging into northern California, with an upper level jetlit
swinging around the southern edge moving into western Arizona.
This will be the main driver for convective activity through this
weekend, as the trough flattens and moves eastward into the Great
Basin.
This will enhance the southwesterly flow at the lower levels,
provide moisture and be the focal point for precipitation Saturday
and Sunday. Based on the moisture profiles aloft, the activity
should be confined to the southeastern portion of the state.
By Tuesday, the precipitation chances dwindle and daytime high
temperatures will be in the mid 90s across the lower elevations.
&&
.AVIATION...Valid through 02/00Z.
SCT-BKN clouds at 8k-12k ft AGL. Isolated to scattered -TSRA/-SHRA
will continue through the evening mainly near the higher terrain and
along the International Border from KOLS to KDUG. SWLY/WLY SFC wind
at less than 12 kts this evening, except near TSRA where gusty
outflows will be possible. More scattered -TSRA/SHRA are expected to
develop Saturday morning into the afternoon hours. Aviation
discussion not updated for TAF amendments.
&&
.FIRE WEATHER...A slight chance of thunderstorms mainly near the
mountains and along the International Border through this evening.
An increase in shower and thunderstorm coverage will occur this
weekend, but some drying is expected again early next week. Expect
terrain driven 20-foot winds at less than 15 mph, except brief
strong gusts near thunderstorms.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
MJS/JKP
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