Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/11/19
Area Forecast Discussion
National Weather Service Hastings NE
853 PM CDT Tue Sep 10 2019
.UPDATE...
Issued at 853 PM CDT Tue Sep 10 2019
Some comments regarding mainly thunderstorm chances rest of
tonight:
The short version:
Not to make too big of a deal out of (currently) only 20 percent
chances, but in short, have "flip-flopped" any small chances for
storms tonight in our northern zones from PRE-midnight to POST-
midnight. By "northern zones" we are generally talking near/north
of the Highway 92 corridor, as the forecast for the rest of our
coverage area (CWA) remains dry as before.
More details:
It`s been an almost eerily-quiet evening thus far within our
coverage area CWA, although this was largely expected. As
expected, a fairly expansive cluster of strong to severe
thunderstorms has blossomed to our north-northwest within north
central/northwest Nebraska along the main warm frontal zone. In
addition, more subtle forcing sparked a few rogue storms both to
our southwest (northwest KS) and southeast (northeast KS),
although this southern activity has since largely faded with the
setting sun. Based on reliable-looking short term models (namely
HRRR) and radar trends, it`s become increasingly-obvious that our
northern zones will likely get through at least midnight storm-
free. As a result, have pulled any formal mention of
showers/storms before then. However, while the previous forecast
was dry in our north for the post-midnight/late-night hours, have
now introduced a small chance for this time frame, as especially
the HRRR is suggesting that some convection could build down along
a southward-oozing outflow boundary. Because this is a fairly low-
confidence scenario for now, have only gone with 20 percent PoPs
(slight chances) at this time, but the overnight shift will have
to keep an eye on this. Fortunately, am not thinking that any late
night storms that MIGHT invade our north would be severe, but some
gusty winds/small hail cannot be ruled out. For now have not
extended any of these slight Pops beyond 12Z/7AM, but this will
also be something to watch in case any activity "leaks" into the
Wed daytime forecast period.
Of lesser consequence, a few final notes about the overnight
forecast:
1) Based largely on trends observed trends from last night (and
given stronger/steadier southerly breezes most areas tonight),
nudged up overnight lows 1-2 degrees in most areas, with the
majority of the CWA expected to drop no lower than 69-73 degrees.
2) IF late-night outflow and possible storms do make it into our
northern counties, then the wind field there will likely become
considerably more easterly than southerly, with an easterly
component perhaps lasting well into the daylight hours before a
southerly wind becomes established again. This may not be well-
captured in current forecast grids/products ,so outflow
trends/influences will need monitored.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 345 PM CDT Tue Sep 10 2019
Upper air and satellite data show continued southwesterly flow in
place across the region...set up between high pressure centered
roughly over the TN/Carolinas region and low pressure/troughing
affecting much of the west/NWrn CONUS. Outside of a weak
thunderstorm that clipped far western Dawson County earlier this
afternoon and some light precip moving into Jewell County, things
have been dry across the CWA...with partly cloudy to mostly clear
skies. At the surface, a warm front has been gradually working its
way north with time, and currently sits draped across far
northern portions of the CWA. To the south of the front, the rest
of the CWA has continued breezy southerly winds, with gusts in the
20-25 MPH range. Hasn`t been any surprises with temperatures, 3PM
obs range from the mid 80s to lower 90s.
Overall, no significant changes were made to the forecast for
tonight and into tomorrow...which for most locations remains dry.
There is expected to be an increase in thunderstorm activity
through the rest of this afternoon through tonight, but models
remain in good agreement showing those best chances focusing to
the north of the CWA. The sfc front continues to push north with
time, and convergence along the nose of a 40-50 kt LLJ will keep
most activity out of our area. It`s close enough that wasn`t
comfortable no having any PoPs in the forecast, so do have 20%
chances still across our north. More isolated/scattered activity
will also be possible off to our west through tonight, but models
are in pretty good agreement keeping it off to the west.
Kept the daytime hours tomorrow dry, there is good agreement
showing the better chances holding off after 00Z, as a stronger
system swings through the Plains. May be a close call for those
far WNWrn areas late in the afternoon. It`s looking to be another
breezy day, with low pressure deepening over NErn portions of CO.
The main frontal boundary spends the day off to the NW of the
CWA, the resultant southerly winds look to be in the 20-25 MPH
range, with gusts over 30 MPH. No big changes to forecast highs
for tomorrow, which will again be in the mid 80s to lower 90s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 345 PM CDT Tue Sep 10 2019
At this point, the best chances for widespread precipitation for
over the next week looks to come Wednesday night. The upper level
system currently impacting the W/NW CONUS is shown by models to
keep pushing east with time. By 12Z Wed, the trough has moved well
into the Rockies, emerging onto the northern/central High Plains
by 00Z...this timing helping keep the area dry during the daytime
hours. Between 00Z-12Z Thur, models show a closed 500mb low
developing over the MT/WY/ND/SD, with the southward extending
trough axis swinging into the Central Plains. Thunderstorm
activity is expected to push through the area with the surface
cold front, and looks to clear all but eastern portions of the CWA
by 12Z Thurs. Models continue to show the potential for
strong/severe thunderstorms during this period, especially early-
on across the western half of the CWA. Damaging winds/large hail
would be the primary threats...heavy rain will also be possible,
but activity should be pretty progressive in nature.
Outside of some lingering activity during the morning on Thursday,
the rest of the day...and most of the extended period
forecast...is dry. Models show the main upper level system
continuing to make its way east, leaving more zonal flow in its
wake through the weekend...turning more southwesterly once again
for the start of next week. Forecast does have a couple low
chances PoPs in there, late Friday night and again late Saturday
night, but confidence in timing/location is not high.
As far as temperatures go, highs drop back into the 70s on
Thursday in the wake of the cold front...before warming back up
into the 80s/low 90s for the latter portions of the extended
period.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 703 PM CDT Tue Sep 10 2019
Confidence is very high in VFR ceiling/visibility through the
period, with mainly only limited mid-high level clouds. Although
the chance for a VERY random/isolated shower is not necessarily
zero, it is far too low to justify TAF inclusion. By far the main
story through the period will be breezy/gusty southerly winds
(likely some of the strongest non-thunderstorm speeds observed
around here in a few months), along with a period of low level
wind shear (LLWS) this evening into Wednesday AM.
Surface winds:
A fairly consistent southerly direction will prevail, with
sustained speeds averaging 12-16KT/gusts 18-22KT through most of
the period. However, these speeds will kick up another notch for
the latter hours of the period on Wednesday afternoon, commonly
sustained around 20KT/gusting 25-30KT.
LLWS:
Despite surface winds remaining somewhat elevated, have maintained
a mention of moderate LLWS for the entire 03-14Z time frame, as
southerly winds within the lowest 1,500 ft. AGL will accelerate to
around average around 45KT, resulting in generally 30-35KT of
shear magnitude.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
UPDATE...Pfannkuch
SHORT TERM...ADP
LONG TERM...ADP
AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Huntsville AL
831 PM CDT Tue Sep 10 2019
.NEAR TERM...(Tonight)
Issued at 831 PM CDT Tue Sep 10 2019
While virtually the entire CWA is now rain-free, we have additional
clusters of thunderstorms edging up against southeast DeKalb County
from NW GA into Cherokee County. Unsure if these will enter our
forecast area as the HRRR suggests over the next few hours. Thus,
will leave a low PoP this evening in northeast AL. Otherwise, may
have to introduce patchy fog as well given the very moist boundary
layer conditions, especially for area that received rainfall this
afternoon and early evening.
.SHORT TERM...(Wednesday through Thursday)
Issued at 230 PM CDT Tue Sep 10 2019
This weak convergence boundary moves north into Kentucky and Tennessee
on Wednesday, so left out precipitation chances on Wednesday.
Overall, high temperatures should remain in the mid 90s, with some
afternoon cumulus development expected. However, it still looks very
humid with afternoon dewpoints values remaining in the lower 70s
primarily. So heat index values look to remain between 100 and 104
degrees. Could see a few 105 values, but not enough to warrant a heat
advisory at this time. Not much change in the overnight conditions
Wednesday night, with a humid airmass still in place and lows only
drop into the upper 60s/lower 70s.
Several models forecast the upper ridge to strengthen more right over
the Tennessee Valley on Thursday. 925 mb temperatures also climb a
bit higher to between 25 and 27 degrees again. Believe that a return
to highs in the mid to upper 90s will be the result over northern
Alabama. It looks as though enough mixing of drier air will occur to
keep dewpoints a bit lower and keep heat index values between 100 and
104 degrees on Thursday.
.LONG TERM...(Thursday night through Monday)
Issued at 230 PM CDT Tue Sep 10 2019
Lows around 70 degrees are expected Thursday night. Friday looks
very similar and may be a tad hotter but drier. Wouldn`t be surprised
to see a 99 high or two. Again heat index values in the afternoon
will be close to advisory criteria but likely still between 100 and
104.
Friday night into the weekend, a frontal boundary and boundary ahead
of it push southeast and into northern Alabama. How much moisture
that ends up along the front is a bit uncertain, but kept a 20 to 30
percent pop in Friday night into Saturday. The cloud cover and any
precipitation should keep highs a bit lower in the lower to mid 90s.
Drier and cooler air is expected to move into the area behind the
front Saturday night into Sunday. Lows in the mid 60s to lower 70s
are expected.
A return to a wetter pattern may occur next week, but models are very
divergent. For now went with low scattered chances of showers and
precipitation.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 628 PM CDT Tue Sep 10 2019
A few light showers will at least be in the vicinity of either
terminal through 3Z to 5Z this evening. Broken high CIGS will
give way to clear skies shortly after midnight. This and light
winds should allow patchy fog to form tonight. For now dropping
VSBYS into the MVFR realm after 09Z. Guidance shows KMSL dropping
to 2SM (or possibly lower) between 10Z and 12Z. Will have to watch
for the formation of denser fog at either terminal. VFR conditions
should return by 15Z at both terminals and continue through the TAF
period.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...17
SHORT TERM...KTW
LONG TERM...KTW
AVIATION...KTW
For more information please visit our website
at weather.gov/huntsville.
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1016 PM EDT Tue Sep 10 2019
.UPDATE...
Issued at 1010 PM EDT TUE SEP 10 2019
Hourly grids were freshened up based on recent observations and
trends. The main changes were to hourly temperatures and dewpoint
curves to better align with the observations. Some convection is
still occurring in parts of Middle TN and the Cumberland Plateau
of TN and in portions of central KY. As the night progresses this
should continue to weaken and probably dissipate. Some guidance,
such as recent RAP runs and 0Z HRRR and 01Z HRRR suggest a bit of
convection is possible overnight developing over or near the
west and north. Earlier HRRR runs did not have this and the RAP
generally trended toward less activity from 21Z to 0Z runs. Given
the presence of upper level ridging centered in the Appalachians
and time of day would be limiting factors to this potential.
A shortwave does appear to pass by to the northwest and GFS and
NAM runs show some height falls overnight as well. At this time,
we have continued with some 5 to 10 percent pops in the northern
and western areas overnight to early on Wed as some convection
cannot be completely ruled out during that time. This potential
will continue to be monitored and if confidence in this were to
increase, pops would be increased in those northern and western
areas.
UPDATE Issued at 815 PM EDT TUE SEP 10 2019
Diurnally driven convection that was occurring over our southwest
counties has dissipated over the past couple of hours. Some
convection is still ongoing over central KY and parts of Middle TN
and the TN Cumberland Plateau. At this time, we expect that
convection to dissipate as it attempts to move northeast as the
atmosphere stabilizes as we are now past sunset. Temperatures
remain warm, especially on the ridges and in more open terrain
locations. However, several valley locations have dropped into the
70s bringing relief from today`s record warmth. No significant
changes were needed at this time.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 400 PM EDT TUE SEP 10 2019
19z sfc analysis shows high pressure in place through eastern
Kentucky with strong ridging aloft. This kept the skies sunny and
allowed for record highs throughout the area. In fact, with JKL
hitting 97 degrees we have now set the highest temperature on
record for September. Certainly portions of the area being in a
drought that is worsening has contributed to this heat. Dewpoints,
meanwhile, in the low to mid 60s, have kept heat indices from
exceeding 100 degrees in too many places, but still it is quite
hot, especially for this time of year. With nearly as hot
temperatures expected through Friday will highlight the heat
concerns in the forthcoming HWO. A stray shower/future
thunderstorm is trying to develop near the Cumberland Plateau and
could linger just across the border into McCreary or Whitley
County. Winds are mostly light from the west to southwest with a
few places seeing gusts up to 20 mph.
The models remain in excellent agreement aloft through the short
term portion of the forecast as they depict the 5h ridge peaking
over the Tennessee Valley and Southern Appalachians. This will
keep most of the energy off to the north and west of the area for
the period, but some weakness in the height fields to the north of
the area on Wednesday could affect Kentucky. Given the model
agreement have again favored the NBM as the starting point for all
the grids along with some consideration to the NAM12 PoP and QPF
fields on Wednesday.
Sensible weather will feature a warmer night than last, but still
able to see a ridge to valley temperatures split to set up along
with more river valley fog towards dawn. Likewise, similar
conditions can be expected on Wednesday night. During the day -
hot temperatures will again be the rule with low to mid 90s
expected but more in the way of clouds and a potential for spotty
showers or storms at peak heating should keep it from being a
complete repeat of today. The scattered convection on Wednesday
will not be a certainty but conditions appear favorable given some
upper support and the fact that even some air mass thunderstorms
are developing in the far south this afternoon.
Did again adjust the temperatures from the NBM for spot highs on
Wednesday and also to incorporate the expected ridge to valley
differences each night. As for PoPs and QPF - did not adjust them
much from the near 20 percent values and light QPF for Wednesday
afternoon - more spread included.
.LONG TERM...(Thursday through Tuesday)
Issued at 315 PM EDT TUE SEP 10 2019
The trend of extremely warm weather will continue on through the end
of the extended period. Southerly flow and partly cloudy skies will
initially lead to the hot weather. Even though we may see a few
showers and storms across the area on Friday, these should not occur
until late in the day, and should allow temperatures to once again
rise to near record values. The overall trend in the extended is for
daily chances of late day showers and storms and warmer than normal
temperatures. A poorly defined frontal boundary is forecast to stall
out across the region over the weekend and will be the trigger
needed for shower and storm activity. Winds will be primarily from
the south or southeast during the period, which will contribute to
the expected warm weather. Highs will range from the low to mid 90s
the first couple of days in the extended, with max values mostly in
the upper 80s after that. Nightly lows will average in the mid to
upper 60s across the area. The best chances for rain should be over
the weekend, as the front stalls over the area. The rain chances
should last through the day on Monday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 820 PM EDT TUE SEP 10 2019
With upper level ridging and surface high pressure dominating the
region, mainly dry weather will continue for at least the first 18
hours of the period. Isolated convection is expected to develop
during the last 6 hours of the period. Chances and confidence in
this are too low to include at this time. Few clouds near 5kft AGL
were included at all sites during all or portions of the last 6
hours as more in the way of cumulus development is expected on
Wednesday as compared to today at the very least. Winds will
remain out of the south to southwest during the first 15 to 18
hours of the period, before becoming west. However, outside of any
convection, speeds will remain below 10kt. Patchy river valley
fog will develop around or after 6Z and affect some locations as
late as 13Z, but this is not expected to affect any of the TAF
sites.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...JP
SHORT TERM...GREIF
LONG TERM...AR
AVIATION...JP
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
901 PM CDT Tue Sep 10 2019
.UPDATE...
900 PM CDT
While all is quiet this evening with a mid summer-like warm and
humid air mass in place, things *could* get more active later
tonight and into or even through Wednesday morning. It`s a
tricky/low confidence forecast regarding convective trends, as
potential available forcing is pretty subtle amidst high MUCAPE
and little capping. 00z RAOBs at DVN and ILX featured ~3000-3500
j/kg of MUCAPE, mean mixing ratios of 14.5-15 g/kg, high freezing
levels near 14kft and anomalously high PWAT values near 1.75".
The main uncertainty is whether there will be enough forcing to
kick off convection over the area and/or convection festering into
the area on outflows. Given the strong instability above
stabilizing boundary layer, it won`t take much to get
thunderstorms to go, but forcing mechanisms are less clear,
leading to a wide range of solutions on near term and high-res CAM
guidance. A few weak short-waves may approach the region
overnight into early Wednesday, one lifting northeast from Kansas
City area and another near St. Louis that will lift northeast
across central Illinois and into central Indiana.
Models are varying given lower magnitude of the forcing. Our
official forecast is relatively similar to afternoon forecast
package and favors the northern wave possibly kicking off storms
near the Wisconsin border after midnight with outflows then
potentially aiding in scattered storms trending southward with
time toward I-88 and even I-80 corridor or south during Wednesday
morning. Interestingly, RAP is much more aggressive than recent
HRRR runs, which initializes with RAP as initial conditions.
Despite the uncertainty, should storm coverage increase tonight
into Wednesday morning, could be a localized flooding threat given
high PWATs and mixing ratios along with high freezing levels (warm
cloud processes). As such, the WPC updated 01z day 1 excessive
rainfall outlook maintained a Marginal Risk for I-80 and north.
Also can`t rule out the southern wave kicking off thunderstorms in
southeast CWA, as shown on latest HRRR and new 00z 12km NAM,
though new 00z 3km NAMNest is much less aggressive than 18z run.
Finally, exact evolution of thunderstorms or lack thereof will
certainly have potential to significantly impact high temperatures
on Wednesday for at least portions of the area. This will
especially be the case if wind direction is augmented by outflows,
while warmer temps will be possible if convection is lacking. For
now, trended slightly lower with high temps, particularly north of
I-80. At this time, appears best chance to reach 90 again will be
south tomorrow, but certainly still possible north.
Castro
&&
.SHORT TERM...
329 AM CDT
Through Tonight...
Following the passage of a warm front lifting north across the CWA
has spread unseasonably warm, humid air across the region.
Temperatures across the region should top out this afternoon in
the upper 80s to lower 90s with sfc dewpoints in the upper 60s to
middle 70s. Latest radar and satellite imagery indicate the main
cu development across nwrn IL into ern IA with a sct line of
showers from sern WI to ern IA. Some of these showers could linger
into the early evening with an isolated cell potentially
developing into a short-lived thunderstorm, but with the main
forcing and low-level jet focused more to the west into IA, expect
much of the area to be dry through the evening and into the
overnight hours.
The main window of opportunity for more widespread showers and
thunderstorms should be after midnight and more likely toward the
pre-dawn hours. The high res guidance is divided into 2 camps,
with either developing an MCS over srn WI and then diving into nrn
IL or a more restrained solution with activity more confined to
the area invof the warm front with outflow and and a lower
coverage of shra/tsra, but also sagging south into the northern
portions of the CWA. Have trended the latest update more toward
the latter solution, but there does still remain the chance that
the former solution could develop as well. In either case, there
should be ongoing convection for the morning rush hours, with the
main question being how far south that the activity will push.
Currently, feel that much of the activity will be along and north
of I-80, at least into tomorrow morning. With the warm/moist
airmass already in place and a persistent swly fetch of warm/moist
air expected to continue through the night, expect unseasonably
muggy conditions tonight, with lows in the 70s.
&&
.LONG TERM...
224 PM CDT
Wednesday through Tuesday...
Wednesday and Thursday...Challenging forecast with regards to
temperatures and thunderstorm chances as a warm front continues
linger across the region. Model guidance through the day on
Wednesday does suggest that the front will remain north of the WI
border through the day with any earlier in the day convective
outflow likely shifted back north of our area, with the exception
possibly being right near the lake shore across NE Illinois.
Therefore warm and humid conditions should be able to
develop/redevelop following any remnant morning precipitation each
of the next few days.
Guidance would tend to favor areas north into WI for development
during the day, but with this development being a bit more robust,
we could be in pattern where convective outflow will drive into NE
Illinois during the later afternoon/evening. These details are
certainly challenging to pinpoint at this distance, and much will
hinge on where the composite outflow/synoptic boundary ends up based
on convection Wednesday afternoon. Portions of the area are in a
Marginal risk for severe storms on Wednesday afternoon/evening.
Suspect during the day any development would be more isolated away
from I-90 north or I-88 north, and even there it could be low
coverage. Competing influences with an increasing low level jet
Wednesday night and cool northeast outflow should inhibit the front
from diving back south across the remainder of the area, and
therefore and lends some credence to another warm and humid day
Wednesday, with more uncertainty Thursday as it appears we would
maintain some form of onshore flow. Areas south should warm
without issue.
Our next more organized front is slated for later Thursday. The
timing is important locally as it will likely play a significant
role in how widespread/intense convection will be. A slower system
would be a more diurnally unfavorable timing of fropa locally
(overnight Thursday into early Friday morning) for more
intense/widespread convection, while a faster system (which seems
unlikely), could place convective timing into the evening hours
Thursday, a bit closer to more favorable time of day. There is also
the possibility of prefrontal warm sector development, whereas if
that were to occur would favor thunderstorms, but even so the shear
is more tied to the upper trough and front. Therefore highest severe
probs are currently upstream of our area.
Friday through Monday...The strong surface cyclone will Friday
should be breezy and much less humid with any lingering showers in
the eastern CWA likely to end in the morning. Current forecast
for the weekend is dry with moderating trend, though the latest
GEM and ECMWF suggest a shortwave could kick off convective in the
region Sat night into Sunday morning in advance of a northward
returning warm front, but neither is too overly excited, and the
higher probs will be NW CWA, mainly west of the Chicago area (and
more so I-39). There is still a fairly good signal in the majority
of the medium range guidance on the eastern CONUS upper ridge re-
strengthening early next week, not to the strength of the current
ridge, but its amplitude appears to be larger as a deep trough
develops in the west. This pattern would suggest additional warm
and humid days next week, maybe not to degree of this week, the
amplitude of the pattern is one that would keep the lower Great
Lakes mostly dry.
KMD
&&
.AVIATION...
For the 00Z TAFs...
Quiet conditions with light SW winds are expected through at least
the early overnight hours under plenty of mid to upper level clouds.
Two clusters of convection are possible late tonight into Wednesday
morning. A veering low-level jet to the west overnight will focus
convection into southern WI late tonight. Much of this activity
should remain north of the Chicago metro terminals, but possibly
affect RFD. A second cluster of convection with a small mid-level
disturbance is also possible across portions of northern IL into
northwest IN generally in the 11-15Z period Wednesday. Confidence
remains low on if this convection will develop, so have maintained a
PROB30 TS for the Chicago metro sites until newer guidance is
available and observational trends are more apparent after 00Z.
Winds on Wednesday will depend on potential convection during the
morning. If convection fails to materialize, gusty SW winds can be
expected most of the day. However, if convection does occur in the
morning, a period of SE winds will likely occur behind the
convection for several hours before gusty SW winds develop.
Finally, a boundary shifting south across the area by late Wednesday
evening is expected to initiate scattered convection, so have used a
VCTS to convey this in the ORD/MDW TAF.
Kluber
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
735 PM CDT Tue Sep 10 2019
.Updated for 00Z Aviation Discussion...
Issued at 725 PM CDT Tue Sep 10 2019
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 348 PM CDT Tue Sep 10 2019
Short term concern is severe convective threat Tonight and
Wednesday night along with the heavy rain/flash flood threat.
Sky finally broke out to attain forecast highs around 80 over much
of the southern CWA. Sunshine will give way to increasing clouds
this evening from the southwest along with increasing rain/thunder
threat into the southwest area before 06z in the southwest and
working east into west central WI after 09z. Various HIRES models
continued their trend of developing convection over South
Dakota/Nebraska region and shift east ahead of the propagating
trough and development of low level jet into southwest MN late. High
PW`s to 1.75(2 to 3 standard deviations above normal) into southern
MN by 12z Wed should provide some decent rainfall rates. The current
QPF forecast has 1 to 2.5 inches into a small part of south central
MN through 18z Wed. Contemplated flash flood watch for the southern 2
tier of counties along I-90 but believe convective system that does
develop over South Dakota will be progressive through early Wed
morning. Latest HRRR model trend does develop linear complex as it
moves into southern MN late. Will need to monitor for severe
convective wind threat per SPC Day1 outlook.
System moves east during the early morning and should weaken as it
moves east. Then convective setup for Wednesday afternoon and night
will depend on overall movement of surface warm front. At the moment
the front is forecast to remain over the southern third of the area
through the afternoon. At least lower 80s expected into south
central MN with 70s into southern MN with some 60s over the far
northern CWA. Should see convection fire by late afternoon
along/north of the front with all modes of severe weather possible
along warm front and at least a wind threat with the propagation
of the cold front. Heavy rainfall will remain a threat with
another 1 to 2 inches possible over eastern central MN into a
portion of west central WI. Flash flood threat may lift into this
region if warm front lifts fast enough north into early Wed
evening. Will have to monitor model trends for possible flood
headline this period.
.LONG TERM...(Thursday through Tuesday)
Issued at 348 PM CDT Tue Sep 10 2019
We will not be out of the woods with the threat for severe weather
and heavy rainfall on Thursday. At daybreak Thursday, the
mid/upper trough is progged to be over the western Dakotas, with
the surface low entering southwestern Minnesota. Expect showers
and thunderstorms to be be ongoing Thursday morning as overrunning
continues. We really don`t look to see a break until the cold
front passes Thursday night. Given PWATS still nearing 2 inches,
heavy rainfall will remain a concern. The severe weather threat
will be contingent on where boundaries are located and how much
instability we can tap into.
Showers look to be possible on Friday in the cyclonic flow behind
the departing trough, primarily over central MN/WI. Zonal flow
then develops for the weekend, which will mean an overall trend
to drier weather but we can`t rule out a hit or miss shower.
A deepening trough over the western CONUS induces mid-level
ridging over the north central CONUS early next week. This will
mean a return to above normal temperatures with highs in the upper
70s and lower 80s looking likely for Monday and Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 725 PM CDT Tue Sep 10 2019
VFR conditions this evening but thunderstorms across South Dakota
will move eastward overnight and should affect KRWF and KMKT, but
could reach as far north as KMSP, KRNH, and KEAU. Expect low
clouds to continue for Wednesday, and could see additional showers
and thunderstorms.
KMSP...
VFR conditions this evening but thunderstorms across South Dakota
will move eastward overnight and could affect KMSP for the morning
rush. The model guidance has been a bit slow, so sped up the
timing of the thunder. Expect low clouds to persist for
Wednesday, and could see additional showers and thunderstorms.
/OUTLOOK FOR KMSP/
THU...MVFR with IFR/TSRA possible. Wind SE at 10 bcmg SW at 20
kts.
FRI...VFR/MVFR possible. Wind W at 20G30 kts.
SAT...VFR with MVFR/TSRA possible. Wind S at 10G20 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...DWE
LONG TERM...LS
AVIATION...JRB
Area Forecast Discussion
National Weather Service Pueblo CO
305 PM MDT Tue Sep 10 2019
.SHORT TERM...(This evening through Wednesday)
Issued at 305 PM MDT Tue Sep 10 2019
SW upper flow over the area for another day, as deep trough slowly
edges eastward through the Pacific NW. Surface trough remains in
place over the sern plains, with weak convergence and very unstable
air mass producing some isolated thunderstorms along and east of the
boundary. Farther west, still waiting for wrn CO convection to reach
the Continental Divide as of 21z, though with very dry low levels
still in place, initial round of storms will contain more wind than
rain as activity pushes newrd into the region. Tonight, HRRR keeps
convection going in the far se until 03z or so, before storms weaken
as they shift into KS/OK. A few CAMs keep at least isolated storms
going well into the night along the Continental Divide, with a few
cells even reaching the Sangres after 06z, so will retain low pops
in the forecast for mainly the higher peaks into Wed morning.
On Wed, upper trough lifts e-ne through the nrn Rockies, while w-sw
flow deepens across CO. Still a threat of some thunderstorms near
the Continental Divide, especially earlier in the day, before
moisture is swept away by strengthening wly flow. Looks like too
much downslope flow elsewhere for convection, though a storm or two
may fire toward 00z along the surface trough near the KS border. Wly
flow and deep mixing should lead to another day of very warm to hot
temperatures, with readings deep into the 90s across the eastern
plains.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 305 PM MDT Tue Sep 10 2019
Wednesday Night and Thursday Morning:
Isolated showers will exist over the far eastern plains at the
beginning of the long term forecast period (Wednesday at 6PM MDT).
CAPE values over the far eastern plains will be around 1,500 to
2,000 J/kg with 0-6 km bulk shear values around 20-30 kts. The
hodograph doesn`t seem to conducive for sustaining severe storms,
with a slightly curved profile, but the main characteristic is speed
shear profile. DCAPEs around around 1,500-2,000 J/kg, so gusty winds
are likely under any of the storms that form. So overall, severe
criteria hail isn`t really expected, but is possible, but the main
impact of concern are severe criteria wind gusts. The storms will
likely dissipate or move out of Colorado by midnight. An upper level
trough will propagate over the region overnight, which will lower the 700 hPa temps to right around freezing, which means... snow over the higher peaks of the northern continental divide. Early Thursday morning a cold front will propagate over the eastern plains, but PW and RH fields reveal that the passage should be dry, with gusty northerly winds as the main impact.
Some drier air will remain over the western half of the region, so
low temperatures will be chilly over the shear mountain valleys.
Places like Creede and Westcliffe will see overnight lows in the low
30s. The plains will be in the low to mid 50s, the mountain valleys
in the upper 30s to low 40s, and the mountains in the 20s to low
30s.
Thursday:
With the front passed, temperatures will be around average for the
first time in a while. High temperatures over the eastern plains are
expected to be in the low 80s, the mountain valleys in the low 70s,
and the mountains will be in the 40s to 60s. The atmosphere will be
stable, so now showers or thunderstorms are expected throughout the
day on Thursday. The northerly winds will shift to the east during
the evening hours, which could create some clouds over the mountains
and the potential for low clouds over the plains.
Friday:
A tight pressure gradient over the eastern plains will cause gusty
winds during the afternoon hours, and will advect low level
moisture from the south, which will set-up a weak dryline. Some
isolated thunderstorms are possible over the Colorado and Kansas
border. Everywhere else is expected to be dry. Temperatures will
warm up again to above average, but temperatures are still expected
to be cooler than what we`ve been experiencing.
Saturday through Tuesday:
An upper level low will try and makes its way across the Great Basin
and over Colorado in the extended term. The result will be
southwesterly flow over Colorado, which means that fire weather
conditions will be possible. The limiting factor will be how strong
the surface winds get. Saturday and most of Sunday is expected to
remain dry, but low level moisture from the Pacific will advect
ahead of the previously mentioned upper level low, which will bring
showers to the Continental Divide. Temperatures will be well above
freezing, so no snow is expected while the trough is to the west of
the region. Similar conditions will remain for Monday and Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 305 PM MDT Tue Sep 10 2019
VFR at all taf sties the next 24 hrs, as any convection will stay
either over the mountains near the Continental Divide, or over the
sern plains near the KS border. Strong cold front will pass through
KPUB and KCOS Wed evening, leading to a period of strong north winds
overnight into Thu morning.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...PETERSEN
LONG TERM...SKELLY
AVIATION...PETERSEN
Area Forecast Discussion
National Weather Service Sacramento CA
325 PM PDT Tue Sep 10 2019
.SYNOPSIS...
A weather system will bring a chance of showers and isolated
thunderstorms to the mountains this afternoon and early evening.
Below average temperatures continue into mid-week. A wind shift
will provide a warm up and potential smoke issues for the Valley
from surrounding fires. Dry weather returns for the end of the
week while a stronger system passes through early next week
bringing cooler weather and potential precipitation.
&&
.DISCUSSION...
A closed upper low centered along the Washington/Oregon border is
carrying a band of shortwave energy through interior northern
California. As this disturbance sweeps through, showers and
isolated thunderstorms continue to fire over the mountains with
occasional lightning strikes already observed in many of the
stronger cells. While current observational data and dual-pol
radar estimates show hourly rates up to a quarter inch, some
isolated heavier amounts are possible within the heftier cores.
Also cannot rule out the potential for small hail and gusty winds
with the threat winding down by the mid-evening per recent high-
resolution guidance.
Outside of the mountain showers, the Valley has remained mostly
sunny with below average temperatures, generally staying in the
upper 70s to low 80s. After the longwave trough passes to the
east, a shift in the local wind fields is anticipated which will
impact the wildfire smoke transport. On Wednesday, synoptic
gradients support a shift to a light northerly flow while turning
more east-northeasterly overnight. Consequently, recent HRRR smoke
plume simulations show a bit of smoke moving back toward the
Valley.
For Thursday and Friday, an offshore ridge will swiftly advance
through the region affording a marked warm up. While a shortwave
passes through the Pacific Northwest early Friday, it should
produce little to no impact to the sensible weather. High
temperatures each day will feature mid/upper 90s across the Valley
with 70s being more commonplace over the higher terrain. This is
roughly 5 to 10 degrees above average for early September. ~BRO
&&
.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)...
While Saturday will prove to be another warm day across the
region, big changes loom ahead as a significant pattern change
unfolds for early next week. This particular feature actually has
an origin over the Bering Sea (west of Alaska) with the system
eventually reaching the Washington coast by Sunday morning. The
GFS/ECMWF/CMC ensembles and deterministic solutions are in decent
agreement, albeit with timing issues as the GFS/GEFS mean are
quicker. Fairly impressive 24-hour height falls are shown, roughly
in the 10 to 12 dm range, with 500-mb heights being 1.5 to 2
standard deviations below climatology. At a minimum, this upper
trough will provide a significant cool down with Valley high
temperatures likely in the mid/upper 70s on Monday/Tuesday (10 to
15 degrees below average). What remains to be seen is how much
precipitation spreads over the region as there are some rather
robust solutions (i.e., 12Z GFS). The mountains and foothills
should see some showers and thunderstorms with the Valley being
more of an unknown. Abundant dry air underneath cloud bases
typically makes accumulating rainfall difficult this time of year
over the Valley. For now will maintain the best chances across the
higher terrain. ~BRO
&&
.AVIATION...
VFR conditions are expected for the next 24 hours except for possible
MVFR/IFR conditions from isolated thunderstorms through 05z and
from smoke near wildfires. Winds will generally be 12 knots or
below except for gusts up to 25 knots in the vicinity of the
Delta tonight and over higher terrain through 04z this evening.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$