Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/07/17
Area Forecast Discussion
National Weather Service La Crosse WI
948 PM CST Mon Mar 6 2017
.UPDATE...
Issued at 947 PM CST Mon Mar 6 2017
Will allow Tornado Watch to expire at 10 pm as the strongest
portion of the convective line has moved into Wisconsin. Will also
cancel the Severe Thunderstorm Watch for Trempealeau and La
Crosse Counties.
UPDATE Issued at 830 PM CST Mon Mar 6 2017
As line of storms continue to move eastward late this evening,
will be able to drop Tornado Watch. For now, cancelled Wabasha,
Dodge, Olmsted, Mower, and Fillmore Counties in southeast MN, and
Mitchell, Howard, Floyd, and Chickasaw Counties in northeast IA.
UPDATE Issued at 813 PM CST Mon Mar 6 2017
Although the environment should become less favorable for severe
convection into the late evening east of the Mississippi River,
issued Severe Thunderstorm Watch until 08Z for remaining WI
counties (sans Taylor/Clark) given mature line of thunderstorms
moving into the area over the next several hours. Primary threats
will be damaging wind and hail.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 334 PM CST Mon Mar 6 2017
Severe weather threat for tonight has increased across the area.
Satellite imagery and surface observations show incredible
clearing across much of IA/MN this afternoon under a mid-level dry
slot. Low-level scouring now into the western forecast area east
of I-35 and further destabilization is occurring. Currently, TSRA
starting on the dry line near Omaha NE on the western gradient in
CAPE.
Per SPC mesoa...MLCAPES in western IA in the 1500 J/Kg and the
06.19Z RAP bring this to the I-35 corridor at 22Z before a massive
hourly decline with only 800-1000 J/Kg by 00Z in Dodge MN-Floyd
County IA counties. Decline and stabilization of the CAPE further
occurs as the warm sector shifts east in the late evening into WI.
Wind shear is the big story. Current 1km VWP from KMSP/KDMX radars
showing 35-45 kts at 1km and 75 kts at KOAX at 6 km. So, some
excellent shear with directional shear in the lowest 1 km. 06.19z
RAP indicates 0-1km SRH values in the 200-400 m^^2/s^^2 range will
be present in NE IA and SERN MN, so plenty for low-level
spinning.
Overall...the severe weather threat has increased with a favorable
upstream environment. Storms should continue to develop into a N-S
line from MN into IA late this afternoon and move east and enter
Dodge-Floyd county /western forecast area/ around 6-7 pm. Would
expect a QLCS line of storms to enter with threats of damaging
winds and isolated tornadoes...mainly near/due to mesovorticies
on the leading edge. Being early March and per RAP guidance, this
threat should rapidly diminish east with stabilization and loss of
heating, with severe storms becoming less in coverage. Storms are
expected to continue well into WI with strong dynamical forcing.
By midnight, the storms/rain should be near/exiting central WI.
Post frontal winds still look as previously forecast for later
tonight and Tuesday. With 40-50 kts at the top of the mixed
layer...a wind advisory is warranted. On Tuesday mixing will be
enhanced in the afternoon and it appears we will tap 2km winds.
The good thing is it appears these winds decrease 5-10 kts at 2km
keeping wind gusts in the 35-50 mph range at the surface.
.LONG TERM...(Tuesday night through Monday)
Issued at 334 PM CST Mon Mar 6 2017
A wind advisory may be needed Wednesday with stronger winds
continuing.
Thursday night through Monday...Main forecast concerns are
precipitation chances and temperatures Thursday night through
Monday. The 06.12z GFS/ECMWF/GEM are in good agreement in
developing west to northwest flow aloft through the period. The
biggest differences is timing the shortwave troughs embedded in
the flow into the Upper Great Lakes Region. This will have impacts
on timing of precipitation chances/types across the forecast
area. The 06.12z GFS/ECMWF/GEM are in good agreement in advecting
cooler air aloft into the Great Lakes region through the period.
The 06.12z GFS/ECMWF show 925mb temperatures in the minus 5 to
minus 10 degree celsius range for much of the period. This will
allow temperatures to be below normal with highs in the lower to
middle 30s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 534 PM CST Mon Mar 6 2017
All eyes on an impressive line of thunderstorms just moving into
the I-35 corridor. Will impact both TAF airfields this evening
with strong gusty southwest winds from 35-40kts or more. Some hail
also possible, but not enough confidence to include in 00Z TAFs.
For the most part, upstream observations impacted by storms have
stayed VFR with ceilings, but could see reductions in visibility
to 2SM in heavy rain/thunder. Once storms move through, strong
west-southwest wind will continue through the night and into
Tuesday with frequent gusts between 35 and 40 kts. Otherwise, VFR
cloud cover will be the rule. Did not include low-level wind shear
in 00Z TAFs due to frequent high surface gusts, but expect winds
around 2000 ft agl to at least 50 kts through this evening.
&&
.FIRE WEATHER...For Tuesday
Issued at 334 PM CST Mon Mar 6 2017
Strong winds and low relative humidities will cause weather
conditions that could enhance fire spread on Tuesday, mainly in
grasses.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Wind Advisory from 6 AM to 6 PM CST Tuesday for WIZ017-029-
032>034-041>044-053>055-061.
MN...Wind Advisory until 6 PM CST Tuesday for MNZ079-086-087-094-095.
Wind Advisory from 6 AM to 6 PM CST Tuesday for MNZ088-096.
IA...Wind Advisory until 6 PM CST Tuesday for IAZ008>010-018-019.
Wind Advisory from 6 AM to 6 PM CST Tuesday for IAZ011-029-030.
&&
$$
UPDATE...Rogers
SHORT TERM...Baumgardt
LONG TERM...Baumgardt/Jones
AVIATION...Rogers
Area Forecast Discussion
National Weather Service Duluth MN
934 PM CST Mon Mar 6 2017
.UPDATE...
Issued at 934 PM CST Mon Mar 6 2017
Scattered thunderstorms will continue over far eastern Minnesota
into northwest Wisconsin for a couple more hours but the threat
for severe storms has ended. MUCAPE values were around 500J/KG
over northwest Wisconsin into the Arrowhead as of 03Z but that
will be diminishing over the next 1 to 3 hours as cold air
advection develops. Some additional showers have developed over
central to east central Minnesota behind the main line and they
will continue to move north to northeast. We still expect
temperatures to cool enough to support snow showers at all areas
later tonight.
No changes were made to the Wind Advisory at this time. Gusty
winds will develop tonight as the cold front passes but they
should mostly be below Wind Chill Advisory thresholds. The
strongest winds are expect on Tuesday.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 311 PM CST Mon Mar 6 2017
Rain with thunderstorms this evening, chances of snow overnight,
and windy for Tuesday highlight the short-term forecast period.
This evening starts off wet and stormy, with some thunderstorms
potentially severe. The Storm Prediction Center has expanded their
convective outlook, which now includes a Slight Risk south of a
Leader to McGregor to Phillips line. The Marginal Risk has also
expanded farther north and west, encompassing most of the
southwestern one-half of our forecast area. Thunderstorms are
expected to develop along a cold front boundary that is expected
to sweep through the region this evening. Latest HRRR model is
progging convective initiation to occur roughly by 00z this
evening and progressing east and northeastward towards the Twin
Ports area. The storm environment appears to be more of the low
CAPE/high shear variety, with the latest RAP/NAM model soundings
indicating SBCAPE values between 500-1000 J/kg from the Brainerd
Lakes towards the Twin Ports area, but 0-6 km bulk shear values
near 60+ knots, thanks to a strengthening low-level jet, with 850
mb wind magnitudes of 50 to 55 kts. The biggest threats in the
Slight Risk area are damaging winds and large hail. Thunderstorm
activity should exit the eastern forecast area by around midnight
tonight.
Cold air advection will increase behind the cold front boundary,
which will transition any rain showers to snow showers during the
overnight hours. Snow accumulation through the day Tuesday are
expected to be between 1 to 3 inches along the Iron Range and
points northwest. Sfc winds are expected to weaken behind the cold
front before intensifying again during the day Tuesday. The sfc
low pressure center will meander its way across southeast Manitoba
and extreme western Ontario Canada. Both the NAM and GFS are
progging very deep boundary layer mixing of strong 850 mb low-
level jet winds on the southern end of the sfc low, with the
models progging strong momentum transport to the sfc, indicating
gusts capable of 40 to 50 kts. Made some adjustments to the
previous Wind Advisory as the start time seemed to be too early,
so delayed the start time of the advisory to 12z Tuesday, and
trimmed back the end time to 00z Wednesday. Moreover, decided to
expand the Wind Advisory east to encompass all of northwest
Wisconsin due to model soundings at Phillips indicating
sufficiently strong boundary layer mixing of strong flow from
aloft. Models have continued boundary layer mixing up to the 700
mb level, which would be sufficient to tap into the strong 850
flow. Due to the region staying underneath the cyclonic flow from
the sfc low, kept chance POPs going for the rest of the day
Tuesday, especially over the northern half of the forecast area.
Temperatures Tuesday are expected to be closer to seasonal
averages, but still slightly above average, with highs ranging
from the mid to upper 20s northwest to the lower 40s southeast.
Lows tonight will range in the upper teens northwest to upper 20s
southeast.
.LONG TERM...(Tuesday night through Monday)
Issued at 311 PM CST Mon Mar 6 2017
Main forecast concern for extended will be colder air and shortwaves
bringing the possibility of light snow.
Colder temperatures will continue to flow into the forecast region
Tuesday night and will persist through the end of the week. A
strong upper low over northern Ontario will pull down the air
through mid-week. A shortwave will move through the region Tuesday
night and Wednesday causing light snow to develop. Accumulations
will be mainly around 1 to 2 inches along and north of the Iron
Range and in the Arrowhead. The high winds will slowly drop
Tuesday evening and should be below advisory criteria by midnight.
With the cold north-NW flow across the lake Wednesday, there will
be a possibility of lake effect snow showers along the south
shore Wednesday and Wednesday night. A ridge builds into the
region late Wednesday night and will dominate the weather through
Friday reinforcing the colder air across the region. Unlike last
night`s run, the ECMWF now has the main precip area south of the
forecast area similar to the the GFS/Canadian. So will keep the
area mostly dry with little snow.
Models are still depicting a low possibility of light snow on Sunday
mainly south of Highway 2 but confidence is low for this shortwave.
A stronger shortwave will move through central Minnesota on
Monday bringing a better shot for snow for the forecast area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 558 PM CST Mon Mar 6 2017
A strong area of low pressure was located along the far northeast
North Dakota and southern Manitoba border early this evening with
a warm front extending southeast into central and southern
Minnesota. A cold front was located through eastern North Dakota
into western South Dakota. The low will lift north and the fronts
will move through the region overnight with strong cold air
advection developing. Showers and thunderstorms will be possible
this evening across much of the Northland diminishing from west
to east. Some of the storms could be strong this evening over
southern parts of the Northland. As the colder air moves in later
tonight, snow showers will be possible. There will be low level
wind shear this evening, then the wind will veer to west to
southwest overnight and become gusty. Strong west to southwest
winds are expected on Tuesday.
IFR ceilings will gradually improve to MVFR for most areas
overnight and improve further on Tuesday. There were some VFR
conditions in the Brainerd Lakes region already but we do expect
MVFR ceilings to move back in over the next couple hours.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 24 35 12 23 / 80 30 20 10
INL 19 24 7 18 / 50 60 60 20
BRD 25 38 14 27 / 40 20 20 10
HYR 28 41 17 28 / 80 20 20 10
ASX 30 42 18 27 / 80 20 20 20
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Wind Advisory from 6 AM to 6 PM CST Tuesday for WIZ001>004-
006>009.
MN...Wind Advisory from 6 AM to 6 PM CST Tuesday for MNZ018-019-025-
026-033>038.
LS...None.
&&
$$
UPDATE...Melde
SHORT TERM...JTS
LONG TERM...Stewart
AVIATION...Melde
Area Forecast Discussion
National Weather Service Houston/Galveston TX
925 PM CST Mon Mar 6 2017
.UPDATE...
The main update to the evening forecast was to add a mention of
patchy fog to the bays and coastal waters where southeast winds
continued to advect warm, moist air (platform observations
reporting dew points in the upper 60s to mid 70s) across the
somewhat cooler shelf waters. May also see some radiation fog
development inland as winds decrease ahead of an approaching cold
front tonight, particularly in more sheltered or low-lying areas.
Increasing isentropic lift on the 305K surface ahead of the front
should result in a few sprinkles or possible a shower through the
night, with some of this activity possible able to tap into some
of the instability (lapse rates around 6.5 C/km) over far eastern
Texas to produce possibly an isolated thunderstorm or two closer
to sunrise. Otherwise, expect overnight lows to fall into the mid
60s to low 70s under partly to mostly cloudy skies.
Anticipate the cold front now pushing across the Panhandle and
central Oklahoma to reach the northern counties of the forecast
area 7-9 AM and reach the Houston metro midday to early afternoon.
Preliminary evaluation of the 00Z model guidance shows quite a
bit of discontinuity between the timing of the cold front as it
approaches the Houston metro, with the 00Z NAM now almost 3-6
hours slower than the 12Z ARW and NMM as well as the 02Z RAP. As
of now, continuing to advertise the cold front pushing off the
coast but will have to see how much the post-frontal airmass
modifies as the front may slow or stall near the coast. Forecast
soundings show precipitable water values increasing to around 1.5
inches ahead of the front and this, combined with a decelerating
frontal boundary, may produce some locally heavy rain across the
southern two tiers of counties during the afternoon to early
evening hours tomorrow.
Huffman
&&
.PREV DISCUSSION... /ISSUED 601 PM CST Mon Mar 6 2017/
AVIATION...
MVFR cigs are expected to return early this evening and gradually
lower overnight toward IFR. Winds will not relax until between
06-09z as a cold front nears the area. Once the winds decouple,
would expect some patchy fog to develop. Sfc dew pts near KGLS are
near 70 so can`t rule out some sea fog developing near the coast.
The RAP and TT WRF also begin to produce some light streamer
showers between 08-10z so added a VCSH for inland TAF sites but
could really get a shower just about anywhere. The front will
approach KCLL between 13-15z, Houston between 17-21z and Galveston
between 20-23z. PW values ahead of the rise to between 1.5 and 1.6
inches with CAPE values between 1500-2500 J/kg. LI values are
progged between -4 and -7 so can`t rule out getting some strong to
possibly severe storms along the front. Have tempo for the fropa
and associated convection and might need to beef up the wind gusts
with the front. Fcst soundings keep some cloudiness behind the
front so will slow clearing until after this TAF package ends. 43
PREV DISCUSSION... /ISSUED 356 PM CST Mon Mar 6 2017/
DISCUSSION...
Coverage beginning to decrease this afternoon and expecting most
of this activity to be gone by this evening. However, this break
should be short lived as the strong onshore winds help to gin up
more WAA-type showers along/near the coast toward sunrise. Further
north, we will be seeing development along/just ahead of the cold
front moving down from the Southern Plains. While the upper
dynamics look more favorable for strong storms NE of the CWA, we
should still see a fairly healthy line of SHRA/TSRAs develop and
begin moving into the area Tues morning. Still a bit concerned
with locations in/around SE TX that received some good rainfall
Sun and with the rains/clouds today, not really getting much
drying. However, do think that the storms we do get will be moving
and not likely to train.
A brief break in the weather expected behind this front for most
of Weds as a flat upper ridge builds in from the west. Returning
onshore winds on Thurs will begin setting the stage for increasing
POPS through the latter part of the week. Models are still a tad
disparate with the upcoming pattern but starting to see some
consensus with the GFS idea of a more active southern stream jet
by late Thur on through Sat. The next cold front is currently on
track for a Sat night FROPA across SE TX. 41
Marine...
SCEC across the Upper Texas Coast tonight and into Tuesday
morning, as winds will remain between 15 to 20 knots. Seas
will also remain elevated in the offshore waters, remaining between
6 to 7 feet with the occasional 8 foot seas. Expecting south
southeast winds out ahead of the next cold front that is passing
through SE Texas Tuesday afternoon. Showers and scattered
thunderstorms will begin Tuesday morning and continue through the
afternoon out ahead of the front. The front should push offshore
late Tuesday, and winds will shift out of the east northeast for
much of the day Wednesday. Winds will quickly return to onshore flow
overnight Wednesday and into Thursday. Still expecting moderate seas
for the rest of the week.
Hathaway
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 66 73 54 73 64 / 20 60 10 10 10
Houston (IAH) 70 76 54 72 62 / 20 60 20 20 10
Galveston (GLS) 67 72 62 68 65 / 10 60 30 20 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 6 AM CST Tuesday for
the following zones: Coastal waters from Freeport to the
Matagorda Ship Channel out 20 NM...Coastal waters from High
Island to Freeport out 20 NM...Waters from Freeport to the
Matagorda Ship Channel from 20 to 60 NM...Waters from High
Island to Freeport from 20 to 60 NM.
&&
$$
Discussion...14
Area Forecast Discussion
National Weather Service Lincoln IL
829 PM CST Mon Mar 6 2017
.UPDATE...
Issued at 829 PM CST Mon Mar 6 2017
Updated the forecast to increase wind speeds tonight with gusts of
35-45 mph and locally higher gusts especially with thunderstorms
by overnight. Bloomington already gusting to 46 mph at 8 pm.
Southerly sustained winds range from 20-35 mph over central IL at
mid evening and have been gradually increasing during the evening.
KILX 00Z sounding had 2k ft wind of 55 kts and some of this higher
wind is mixing down toward the surface. Will continue to monitor
to see if a wind advisory is needed, but for now have issued a
special weather statement addressing these higher winds.
A strong and deepening 980 mb surface low pressure was over south
central Manitoba, with its cold front extending southward through
eastern MN, central IA and nw MO. A line of strong to severe
thunderstorms was along the cold front and quickly moving east.
HRRR model has the squall line reaching areas nw of the IL river
between 05-06Z (11 pm- midnight), nearing I-55 by 07Z/2 am, just
east of I-57 by 09Z/3 am and to the IN border around 10Z (4 am).
This line is still projected to weaken as it moves east across IL
overnight, with slight risk west of I-57 and enhanced risk west of
Peoria and Springfield. Main severe wx threat is damaging wind
gusts with 15-30% risk, with 5-15% risk of large hail in western
CWA and 2-5% risk of tornadoes over western half of CWA. Lows
overnight to range from lower 40s over the IL river valley where
skies clear late tonight, to the lower 50s over southeast IL.
&&
.SHORT TERM...(This evening through Tuesday)
ISSUED AT 243 PM CST Mon Mar 6 2017
Main concern in the short term is with the convection expected this
evening. Pre-frontal line of showers and embedded storms is edging
eastward across central western Illinois early this afternoon.
Further west, radar imagery and GOES-16 1-minute visible imagery is
showing a line of storms beginning to fire from northwest Iowa into
south central Nebraska, along a dry line. High-resolution model
guidance continues to show this filling in and marching eastward
this evening, with decent agreement in the line reaching the
Illinois River toward midnight and marching through the CWA through
about 4-5 am. Latest SPC Day1 outlook has brought the enhanced risk
as far east as a Peoria-Springfield line, focused on the wind
potential as the line focuses into a QLCS, though in a weakening
state as it pushes east across Illinois. A very sharp cutoff on the
back edge of the rain shield will occur, but the rain will linger
over the far southeast CWA into early Tuesday.
Secondary concern will be the winds through Tuesday. Gusts of 25-35
mph are occurring this afternoon, but are expected to increase a bit
this evening ahead of the line, with some 40-45 mph gusts likely.
Conditions are a bit borderline for a wind advisory, but will need
to monitor this closely over the next few hours. After the
convection passes, there will be a short window when winds subside,
but they should become gusty again by late morning as deep mixing
takes place on Tuesday. Gusts of 30-35 mph appear more likely at
this time for Tuesday afternoon.
.LONG TERM...(Tuesday night through Monday)
ISSUED AT 243 PM CST Mon Mar 6 2017
Central and southeast Illinois can expect an active weather period
through the extended range of the forecast, with a system passing
through or near the area about every other day. Model guidance
continues to struggle with the details within this fast flow regime,
which has required notable forecast adjustments from day-to-day.
Despite the model variation/disagreement, the most consistent trend
has been a further south/colder track to the weather systems.
The first wave to impact the area is the weakest, and is currently
forecast to brush by the area later Thursday into Thursday night.
Initially, conditions would be warm enough for rain across the
entire area. However, It will likely cool enough in the north
Thursday night for a change over to snow, although no accumulation
is anticipated. If the models continue to trend south with this
wave, there is still the potential that it will miss us entirely.
The second wave is the most significant, and is forecast to impact
the area late Friday night into Saturday evening. This timing has
been pretty consistent of late, but again this system has been
trending more southerly in its track. If these trends hold, at least
some light snow accumulation appears possible across the northern
half of the forecast area into midday Saturday.
A final wave arrives around Monday, but model agreement with respect
to its timing is not as good as with the first two waves. This system
also seems poised to produce snow and/or rain across the forecast
area, with the snow more likely in the north and early in the day
before temperatures warm.
Above normal temperatures to start the period will trend below
normal by the end of the week. The passage of each disturbance will
deepen the upper-level troffing over eastern North America and
advect cold low-level air into the area. I guess winter wasn`t
quite done with us yet.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 555 PM CST Mon Mar 6 2017
MVFR ceilings (as low as 1k ft at BMI and CMI) could lift to VFR
next few hours as SPI recently did. Continued VCSH in central IL
TAFs this evening in warm sector. Strong southerly winds around 20
kts with gusts of 23-33 kts early this evening will increase
during this evening as cold front in nw IA and eastern KS
approaches IL/MS river by late evening. KILX 00Z sounding showed
2k ft southerly winds of 55 kts and supports these stronger winds.
Latest HRRR model shows squall line pushing quickly east from
western IA toward the IL river by PIA around 06Z, to I-55 by 07Z
and to DEC and CMI by 08 or 09Z. Carried 2 hour period of TS with
MVFR ceilings and vsbys along with SW wind gusts of 35-40 kts.
Clearing to occur a few hours behind cold front with fair amount
of sunshine expected Tue. Winds veer westerly behind cold front
Tue and gust to 25-30 kts during day Tue, then diminish to 10-15
kts by 22 or 23Z Tue.
&&
.FIRE WEATHER...
Issued at 243 PM CST Mon Mar 6 2017
Some concerns for Tuesday with borderline red flag conditions in
parts of the area. Deep mixing to take place from around 5000
feet, as forecast soundings show 50 knot winds mixing down to the
surface. Very dry in the lower levels, and there is some concern
that dew points could get lower than the low-mid 20s already in
the grids for afternoon. Minimum humidity levels forecast to reach
the upper 20s over the southwest CWA. That area currently has
10-hour dead fuel levels of 11-15%, but could dry out quickly
despite the rain tonight as 30-35 mph wind gusts occur. No fire
headlines planned at the present time due to the uncertainty.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...07
SHORT TERM...Geelhart
LONG TERM...Bak
AVIATION...07
FIRE WEATHER...Geelhart
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
754 PM CST Mon Mar 6 2017
.UPDATE...
754 PM CST
Extensive N-S squall line extending from NW WI south through IA
south into NW MO and then into eastern KS is moving fairly quickly
eastward at about 35 kt. Line has a history of producing damaging
winds with a couple supercells over NW MO and intense embedded
mesovortices/mesocyclones in IA as well, some potentially
tornadic. SPC mesoanalysis suggests the instability axis ahead of
the line is fairly narrow, which was confirmed with the 00z
soundings from ILX and DVN which both shower very little
instability and strong CINH. Some destabilization may continue to
occur east of the instability axis, however the rate of eastward
expansion of the instability axis is being outpaced by the fast
movement of the line. The result will likely be the line
eventually outrunning the instability and weakening as it moves
across our CWA.
While the storms are expected to out run the instability and
essentially begin to run out of gas, there could be a lingering
damaging wind threat into portions of our CWA given the extreme
wind fields and how little it`d take for this line to mix some of
that momentum to the surface, even if the line is in a weakening
phase. The DVN sounding sampled 52kt winds at 1km AGL, but RAP is
forecasting the low level jet to strengthen this evening with 1km
winds increasing to over 80kt. In fact, KDVN WSR-88D is already
picking up 80kt winds at 1.7km AGL. Difficult to say how far east
this line will be able to continue to run on fumes and pose a
severe threat, but given the extremely powerful winds just off the
deck, hard to rule out even a shower producing near severe gusts
even over our eastern CWA.
Other than the convective threat, we will continue to monitor
synoptic winds this evening. As the low level flow continues to
increase just off the deck, concerned we could see gusts in the
35-40kt range this evening, as very little stabilization of the
boundary layer is taking place this evening. Have seen an ob or
two approach wind advisory criteria, but plan at this point is to
hold off on an NPW for winds unless there is a more substantial
increase soon.
Have tweaked timing of pops in the grids tonight, otherwise no big
changes planned to going forecast.
Izzi
&&
.SHORT TERM...
112 PM CST
Through tonight...
Cloudy, mild, and breezy conditions will give way to windy
conditions and a round of thunderstorms late this evening/early
overnight hours. There is a batch of showers along the
Mississippi River that will likely dissipate as they move farther
east, though we may see some light showers or sprinkles from this
espeically across north central Illinois.
We do expect winds to ramp up more considerably this evening as
the pressure gradient increases ahead strong low pressure across
the upper Midwest. The low level jet will ramp up this evening,
and there could be some lifting of cloud bases that will allow
these higher winds to mix down in the evening. 40-45 mph will
likely be reached, and in the thunderstorms it is possible that
some of the stronger/near severe winds may get mixed down, as
45-47 kt winds are depicted on RAP forecast soundings at just over
1000 ft, and 60 kt winds at 2000 ft. We will need to monitor this
potential for wind advisory level winds (sustained > 30 mph or
sustained gusts > 45 mph) and if this may just be a convectively
handled event, as there will probably be a few stronger gusts.
Guidance is also a tad slower with the arrival of the cold front,
with the main line of storms expected mainly after midnight
across most of the area. Again more isolated/scattered activity
is possible later this evening.
KMD
&&
.LONG TERM...
319 PM CST
Tuesday through Monday...
Main forecast concerns at the beginning of the period are with
windy conditions expected both Tuesday and Wednesday, and then
concerns for the weekend are with a return to a colder and
potentially snowier pattern into early next week.
Showers and thunderstorms which will move across the area tonight
will shift east of the CWA by early Tuesday morning, as large
scale ascent and front exit to the east. However, given a slower
trend tonight and with some lingering forcing early in the
morning, its possible that some light showers may still be
situated over the eastern CWA, mainly in Indiana. Did leave some
pops to account for this, but then expect dry conditions for the
remainder of the day. Much drier air arrives on the backside of
this system and anticipate skies to quickly clear Tuesday morning.
Skies should remain sunny on Tuesday, despite expected pattern.
However, some guidance showing some potential for diurnal cu and
even light precip development over eastern Iowa and far northwest
Illinois Tuesday afternoon. With the anticipated steep lapse rates
and additional forcing per mid level energy and surface trough,
this could be a possibility. Forecast soundings will be really dry
though, and so have maintained a sunnier forecast with no chance
of weather. Tight gradient will support sustained speeds around
20KT on Tuesday and with deep mixing/steep lapse rates especially
in the afternoon, strong chance to mix down much higher gusts.
Have kept gusts sub advisory, up to 40 MPH, but do think gusts of
40-45 KT will be possible over much of the CWA Tuesday afternoon.
Gusty conditions will likely persist Tuesday night, but do
anticipate a significant drop in speeds/gusts. Dry conditions
continue Tuesday night into Wednesday, despite frontal boundary
pushing through the area on Wednesday. Main concern on Wednesday
will once again be with strong winds/gusts. Some variability among
guidance on the strength of these winds. Will need to continue to
monitor this period as advisory type winds of 45 MPH or higher
appearing very possible, with some potential for higher gusts
approaching warning criteria. By the end of the work week and
especially this weekend into early next week, monitoring the
potential for a more active pattern. With the arrival of much
colder air, precip chances look to be for mainly snow. Low
probability for precip Thursday night with a wave passing just to
the south, but with guidance continuing to show southward moving
system bringing snow chances across the area Friday night into
Saturday. Have trended the forecast colder with more snow mention,
with a chance for accumulating snow during this time. However,
guidance still varying with exact evolution/track, so confidence
is lower with exact trends. Will need to keep an eye on this
system, as well as another possible snow producing system by early
next week.
Rodriguez
&&
.AVIATION...
For the 00Z TAFs...
545 pm...Main forecast concerns are winds through the period and
thunderstorm potential late this evening/overnight.
A cold front will move across the area after midnight. A line of
thunderstorms currently over west/central IA will continue moving
east into the rfd area by 06z and into the Chicago terminals
centered around 07z. Exact timing will likely need tweaking and
possible to go with a prevailing thunder time window as it
approaches. Convective wind gusts with this line will likely be
from the west/southwest and possibly 40kts or higher. A few
showers will be possible this evening with lingering showers
behind the thunderstorms for a few hours.
Strong/gusty southerly winds will continue this evening with
gusts increasing into the mid 30kt range. Winds will begin to
shift more to the southwest ahead of the cold front and then shift
more west/southwest overnight. Speeds/gusts should diminish some
but still gusty overnight.
Deep mixing of the low levels is possible Tuesday afternoon but
there remains uncertainty regarding how deep the mixing may
become. As a result...confidence for speeds/gusts Tuesday is only
medium. Westerly winds gusting 25-30kts looks on track for most of
Tuesday but there could be a period in the early/mid afternoon
when wind gusts increase into the 35-40kt range. Speeds/gusts
should diminish with sunset Tuesday evening but remain somewhat
gusty into the early evening.
A weak trough will move across the area Tuesday evening and while
there is limited moisture available...its possible there could be
some isolated showers or even a thunderstorm Tuesday evening but
confidence is low. Trends will need to be monitored with later
forecasts. cms
&&
.MARINE...
319 PM CST
Windy conditions will continue across the entire lake through
Wednesday night into Thursday.
In the near term...deepening surface low over the northern Plains
will continue to strengthen as it moves into Ontario tonight into
Wednesday. This will support stronger winds/gales over the
nearshore and open waters for the remainder of the afternoon into
Tonight. A brief lull in the stronger winds may occur by early
Tuesday morning, but this should brief as stronger winds return by
late in the morning and especially in the afternoon. However, it
does appear that prevailing gales will continue over the north
half into Tuesday. Further to the south, gales will be possible,
especially in the afternoon. This will be for both the south half
and the nearshore waters. At this time, it does appear that only
occasional gusts will be possible, but will need to monitor this
potential. Conditions favorable for stronger winds/gusts will
persist Tuesday night into Wednesday and with high confidence of
these higher winds, have extended the gale warning over the north
half into Wednesday. Have lower confidence for these stronger
winds over the south half and nearshore for Tuesday night, but
confidence does rise for Wednesday. Wednesday will not only have
the potential for gales, but even higher end gales. Will also need
to monitor Wednesday as well.
Rodriguez
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Gale Warning...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
LMZ779 until 3 AM Tuesday.
Dense Fog Advisory...LMZ777-LMZ779...3 AM Tuesday to 6 AM
Tuesday.
&&
$$
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO
Area Forecast Discussion...Update
National Weather Service Little Rock AR
830 PM CST Mon Mar 6 2017
.Discussion...
Overall forecast on track. Evening convection has been light over AR
with a bit lack of upper lift, but are now seeing additional
convection forming over northwest AR. But later this evening and
into the overnight, better lift will be seen as the upper level low
pressure trough swings closer to AR, and the cold front moves
through AR overnight. All other factors are present in the
atmosphere, good moisture, enough of instability, and speed and
directional shear with the wind fields in the atmosphere. Still do
expected isolated strong to severe storms before the cold front,
while the better chance will be seen along the boundary. Damaging
winds, large hail and isolated tornadoes are expected. Timing of the
main storms with the cold front remain around 8 PM to midnight in
northwest AR, midnight to 5 AM for central, and 4 AM to sunrise
Tuesday for eastern to southeastern areas. Otherwise, lows tonight
will be from the 40s to 50s north, the 50s to 60s central, to 60s
south. Temperatures will quickly lower behind the cold front
overnight. Winds will also be elevated from the northwest then
become west later in the day. Clouds will break and partly to mostly
sunny conditions will be seen later Tuesday, with highs in the 50s
to 60s. Late evening update will mainly fine tune convection
chances. (59)
&&
.Prev Discussion.../ Issued 540 PM CST Mon Mar 6 2017/
.Aviation...
Overall VFR ceilings with patchy MVFR conditions will start the
forecast. An area of light rain and showers, with only isolated
thunder, will initially move northeast over central to southern AR
this early evening. Later this evening and especially overnight,
additional convection, strong to severe in some locations, will be
seen as an upper system and cold front move through the region. More
MVFR and areas of IFR will be seen more after midnight and with the
stronger convection. Winds will be south at 10 to 20 mph with some
higher gusts, then switch to the west to northwest behind the front
and be 10 to 20 mph. Low level wind shear will be seen as a low
level jet has set up over AR this evening and into the overnight
hours and affect most Taf sites. (59)
&&
.Prev Discussion.../ Issued 256 PM CST Mon Mar 6 2017/
.SHORT TERM...Tonight Through Wednesday
Light showers were in place around the state for much of the day
today with overcast skies. Through the day today have continued to
see temperatures warm across the state with breezy southerly winds.
The main focus of the short term is the tonight period as a cold
front approaches from the west. Strong warm advection win some
locations, will be seen as an upper system and cold front move
through the region.ill continue through the evening hours allowing
temperatures to remain fairly steady after dark tonight...with
dewpoints on the rise as well. Ahead of the cold front...a
moderately unstable atmosphere and plenty of wind energy will be in
place across the state. Nam and HRRR model soundings show over 1500
j/kg of CAPE and 400+ 0-1 helicity across portions of west central
Arkansas. Equally concerning given these and other parameters, is
that the HRRR has shown great run to run consistency in developing
cells out ahead of the main line across portions of west central
Arkansas. Coinciding with these parameters is that in the past few
hours, have started to see some breaks in the clouds across portions
of Yell, Logan, and Scott counties. Putting the pieces together...it
does appear that if enough forcing can be generated the locations
where cells could develop ahead of the front would be north and west
of an Arkadelphia to Conway to Mountain Home line. If these cells
are able to develop...all modes of severe weather will be possible
(hail, winds, tornado).
This system will evolve very similar to what was seen last week as a
cold front will move through the state during the overnight hours.
Storms along this front will be linear in nature and lead to a
straight line wind threat as it moves quickly through the state.
Along these lines of storms, a brief tornado may spin up.
Behind the front on Tuesday, dew points will plummet and breezy
northwest winds will be seen. This will likely create a slightly
elevated wildfire danger. But at this time, it does appear that a
red flag warning will not be needed.
&&
.LONG TERM...Wednesday Night Through Monday Night
A few interesting events are shaping up during the extended term.
First event will be a frontal boundary sagging down from the north
into the state in the Thursday night into Friday time frame. Models
generally push the front southward thru the CWA and bring it back
north as a warm front later on Friday. Upper level flow will NWLY
thru the period, and I am a bit concerned that the front may end up
stalling and becoming quasi-stationary, which would lead to the
potential for a heavier rain event. Will have to see how this
evolves over the next day or two.
The bigger focus right now will be on Saturday into Saturday night.
Models are showing a vigorous shortwave dropping down, along with an
associated cold front moving in from the northwest. At this time
this certainly looks like it may have the potential to produce
severe weather, although at this range it`s tough to make a
judgement call on whether or not there will be enough instability.
&&
.PRELIMINARY POINT TEMPS/POPS...
Batesville AR 57 66 40 69 / 100 50 0 0
Camden AR 66 70 40 73 / 80 80 0 0
Harrison AR 46 63 38 70 / 90 10 0 0
Hot Springs AR 60 69 40 72 / 90 50 0 0
Little Rock AR 64 68 41 72 / 90 60 0 0
Monticello AR 65 69 41 72 / 80 90 10 0
Mount Ida AR 58 66 37 71 / 90 40 0 0
Mountain Home AR 49 64 38 70 / 90 10 0 0
Newport AR 59 66 40 69 / 90 60 0 0
Pine Bluff AR 66 70 41 70 / 80 90 0 0
Russellville AR 56 67 38 71 / 90 20 0 0
Searcy AR 60 68 39 71 / 90 60 0 0
Stuttgart AR 65 69 42 70 / 90 90 0 0
&&
.LZK Watches/Warnings/Advisories...NONE.
&&
$$
Short Term...65 / Long Term...53
Area Forecast Discussion
National Weather Service Norman OK
936 PM CST Mon Mar 6 2017
.UPDATE...
&&
.DISCUSSION...
We have removed Kay and Noble counties from the Tornado Watch and
added four more counties downstream. Latest radar/IR trends have
indicated rapid cooling of CB southwestward over OKC metro. We
have received reports of severe hail with the most intense
updrafts and the thermodynamic/kinematic environment remains
favorable for severe thunderstorms through much of the evening.
The biggest uncertainty in the short term is southwestward extent
of the convection given the proximity of the upper trough.
Forcing/ascent and cooling aloft sufficient for convective
initiation is more in question further west and south, but
confidence is reasonably high for convection to impact east
central and southeast portions of the area through the evening.
Large hail and damaging winds are the main threat. Relatively wide
positive area on 00z sounding in the hail growth zone and fairly
low wet bulb zero heights support the severe hail potential. A
relatively deep mixed layer that appears to have not decoupled
significantly yet should support a continued wind threat as well.
The tornado threat is low, this far west and should be more
substantial further east in the state out of our area and into the
Ozarks region where LCL heights are lower and low level winds are
more backed contributing to higher 0-1km SRH values. Nevertheless,
low level shear remains strong enough that a tornado cannot be
ruled out. The bigger threat certainly is large hail and damaging
winds though.
Another concern is the ongoing wildfires across northwest
Oklahoma. Several large hotspots are seen on 3.9um satellite
imagery, and we have issued several fire warnings per the request
of local officials. RH recovery will be very little overnight
(-3F dew point at Buffalo mesonet currently), probably no higher
than 30 percent so the fire threat will persist well into the
night. Post-frontal northwesterly winds will decrease after
midnight helping fire managers somewhat. We are growing
increasingly concerned about the threat of fires once again
tomorrow given very dry airmass and dry fuels, even though winds
will be light. Winds may be strong enough for near critical to
possibly critical fire weather conditions across northern Oklahoma
near the Kansas border.
BRB
&&
.PREV DISCUSSION... /issued 558 PM CST Mon Mar 6 2017/
UPDATE...
DISCUSSION...
An early look at the Norman 00z sounding raw 1-second data reveals
a pronounced capping inversion still in place with MLCIN of right
around 100 joules. Convective initiation is not expected along the
dryline/surface trough until later this evening when a cold front
meets the warm moist air mass over eastern Oklahoma. Thunderstorms
have already formed well to the north of the area along the front
in Kansas and have quickly become linear. Convection is expected
to continue to build southward along the front as 1.)
cooling/ascent from approaching trough overspread the area, and
2.) frontal convergence lifts warm/moist conditionally unstable
air mass. The western edge of the threat is difficult to forecast
given the complicated nature and evolution synoptic and mesoscale
features.
Current thinking is that deeper convection will develop southward
within the band of high-based cumulus collocated with the
dryline/surface trough. As it moves east into higher low-level
theta-e axis and is overtaken by the cold front, thunderstorms
should develop into north-central Oklahoma. This may occur early
enough that Ponca City and Perry has a higher threat than the
current forecast indicates and an upward adjustment of
probabilities may be needed. We also may need to raise
probabilities for the Oklahoma City area given timing trends.
Damaging wind and large hail is expected to be the
primary hazards. Strong low-level shear is present with 0-1km
bulk shear of 20 knots and 0-1km helicity of just over 200 m2/s2.
A low tornado threat may exist, but the greater threat will be in
eastern Oklahoma into the Ozarks. Storm mode (linear) and fairly
high LCL heights (at least furtherest west) should preclude a more
significant tornado threat.
BRB
PREV DISCUSSION... /issued 513 PM CST Mon Mar 6 2017/
DISCUSSION...
AVIATION... /For the 00z TAFs/
Near term concerns for aviation are ongoing wildfires and wind
trajectories that may result in reduced visibilities from smoke at
Gage and Woodward. We have included MVFR smoke in that TAFs with 5
miles for now given the latest ob at Gage but it`s possible that
lower visibilities may occur. We`ll monitor trends. Otherwise a
cold front will move southeast across the area this evening
resulting in a shift in wind direction to northwesterly. VFR
conditions should prevail. Thunderstorms could back build
southwestward along the front toward Oklahoma City and Norman, but
probabilities of impact at either airport is low at the moment.
Storms should develop southeast of Ponca City so an even lower
probability of thunder at that site is expected.
BRB
PREV DISCUSSION... /issued 252 PM CST Mon Mar 6 2017/
DISCUSSION...
Weather impacts today are fire weather (critical to extreme fire
weather conditions), strong winds, and some potential for strong to
severe thunderstorms late in the day into the evening.
Early this afternoon, a moderately amplified but progressive upper
flow pattern is seen in water vapor channel imagery. A strong upper
level trough encroaching on the Rockies and an intense 100kt +
500 mb speed max at its base are already impacting our weather
significantly. Isallobaric response to falling surface pressures
in the lee of the Rockies have strengthened southerly low-level
flow over the past 36-48 hours with moisture advection ongoing.
Low stratus has been prevalent through the morning, with
occasional drizzle where low level saturation is deepest, but has
mostly eroded across most of the area.
A sharpening dryline will move east and eventually intersect a
southeastward moving cold front late today. A capping elevated mixed
layer should suppress convective development along and ahead of the
dryline through the afternoon. The main impetus for convective
initiation should be combination of cooling/ascent with approaching
trough and frontal forcing. Storms should build southwestward along
advancing cold front possibly into our far northeast counties by
late afternoon, and then expand and develop further across the
eastern portion of our area through the evening. Moderate
instability and strong effective bulk shear should support
organized/persistent thunderstorms and a threat of severe weather
with hail and damaging the wind the main through through the
evening. A more detailed mesoanalysis will be conducted throughout
the afternoon and evening and any pertinent information will be
communicated through updates.
A Wind Advisory is ongoing for much of the area, with a small High
Wind Warning across northwest Oklahoma. Latest NAM and RAP Bufkit
soundings suggest 40 knots near the top of the mixed layer across
much of the area, and momentum transfer should support gusts near 50
mph. Observations have indicated a few locations approaching or
reaching high wind criteria, mainly just west of our area and the
threat of high wind criteria gusts for northwest Oklahoma will
continue through the afternoon.
Medium range guidance is in reasonable agreement for precipitation
chances for the latter half of the week into the weekend. There is
some uncertainty with timing/placement, and therefore extent of
precipitation. Current thinking is warm/moist advection will be
sufficient for at least some low stratus and drizzle Wednesday
night ahead of a low- amplitude shortwave trough that will move
through later in the day. Instability may become sufficient for at
least isolated convection during the afternoon, particularly
across the south and eastern portion of the area. Two more
amplified/stronger shortwave troughs will pass through Saturday
and early Monday. These will bring at least low probabilities of
showers/storms.
BRB
Fire Weather:
Conceptually, the ongoing conditions this afternoon in the northwest
portion of our area are commiserate with some of the more active
fire days given the position of a band of strong mid-level flow
crossing a pronounced low level thermal ridge that is oriented
north-northeast to south-southwest across western Oklahoma into
western north Texas. Latest observations show RH values in the
teens across northwest Oklahoma and frequent gusts around 50 mph.
Several fires are ongoing across the Panhandles and southwest
Kansas. Fuels are dry with latest ERC-G values approaching the
90th percentile. Critical to extreme fire weather conditions will
persist through the afternoon before improving during the
evening. RH recovery will be slow overnight in a post-dryline
airmass with westerly/northwesterly flow. Most locations should
only rise to around 30 percent by morning.
Elevated to near critical fire weather conditions will develop
across much of the area tomorrow. Minimum RH values are expected to
be in the teens across the entire area. Limiting factor for a
significant fire event will be winds given the position of the
surface high pressure to our south. Nevertheless, initial attack
fires may occur. Significant fire spread should be limited to
north of the Kansas border where winds are expected to be higher.
We will need to watch trends across northern Oklahoma where
westerly winds could become strong enough for concern, albeit
below critical wind speed values.
Elevated to near critical fire weather conditions may develop
Wednesday afternoon as southwesterly winds strengthen in a
persistent dry air mass.
BRB
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 77 39 64 39 / 20 30 0 0
Hobart OK 82 38 64 38 / 10 0 0 0
Wichita Falls TX 84 43 67 40 / 10 10 0 0
Gage OK 80 31 65 37 / 0 0 0 0
Ponca City OK 79 36 64 36 / 20 40 0 0
Durant OK 77 49 67 41 / 30 70 0 0
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Red Flag Warning until 11 PM CST this evening for OKZ004>007-
009>012-014>018-021>024-033>038.
TX...Red Flag Warning until 11 PM CST this evening for TXZ083>085-087-
088.
&&
$$
12/17
Area Forecast Discussion
National Weather Service Paducah KY
606 PM CST Mon Mar 6 2017
.SHORT TERM...(Tonight through Wednesday night)
Issued at 252 PM CST Mon Mar 6 2017
Strong/deepening transport of moist air is ongoing over the Quad
State, well out ahead of a developing cold front, as evidenced by a
surge of 60s surface dew points already nosing into SEMO. Gridded
time/height cross sections show some dry air still between about 850-
600 mb, but fully saturating by late evening into the overnight
hours. Soundings reveal PW`s on the order of 1.3", or near the 99th
percentile for this time of year.
As the column moistens, it also destabilizes. We don`t see it doing
so enough to support prevalent thunder mention til after 00z,
although this is marginal for the far western Ozark counties in the
21z-00z time frame. However, by midnight, we see 0-1KM MUCapes
approach 4 digits in the western Ozarks, and maybe reach the 500-
1000 J/KG range perhaps across the remainder of SEMO. With the cold
front extending northeast to southwest across the Show Me State at
06z, we`ll see pre frontal convection/including thunder start to
develop best in our (western) counties in the 03z-06z time frame. A
Slight Risk of Severe will exist (SWODY1) for damaging winds as wind
fields/shear deepen upon the front`s approach, with an Enhanced Risk
primarily (just) west of the CWA within the heart of the instability
axis/peak wind shear. Surface gradient winds will likewise be
increasing thru the teens/perhaps into the 20s mph, and may include
gusts into the 30s mph, but should stop shy of advisory criteria.
That then translates on eastward across the FA, as the front moves
in, and bears down on the Ohio river by tmrw morning. As it does,
the instability fields are sorta pinched off to the south/west, but
bulk shear still exists and should maintain enough to support the
mention of thunder, including the SLGT risk of svr, at least for
about the western half of the FA for the first half of the night.
Even so, it`ll be increasingly transitioning to a heavy rain event
after midnight, particularly from 09z-15z. Anticipate good soaking
rains given high spring-like seasonal PW`s and still good forcing
even after max instability fields start to diminish.
The front is a little slower than previous runs, so we carry the
heavy rain along it thru our southeast counties thru tmrw morning.
Afternoon hours is when we see the drier air start working further
down the column in more earnest, and pcpn shutting off more
completely as the front departs/finally fully exits to the east.
.LONG TERM...(Thursday through Monday)
Issued at 252 PM CST Mon Mar 6 2017
Confidence in the long term portion of this forecast is low. The
12Z model suite brings a stream of 3 storm systems through our
region from Thursday through next Monday in a relatively fast west
northwesterly flow aloft. Each of these systems start out as jet
energy over the northern Rockies, that amplifies to some extent
over the Plains/MS Valley. The models have not locked in very
well, which is to be expected with this type of pattern.
A 1040+ surface high will attempt to spill down out of the
northern Plains Thursday, and a surface wave will develop along
the leading edge over Missouri by 00Z Friday. The surface wave
will move eastward over or near our area Thursday night. Elevated
instability is generated in the models, so will keep a chance of
thunderstorms in the forecast.
Friday should be dry, but temperatures are iffy with the Arctic
high trying to spill into our region. The models have trended
cooler with the system arriving early Saturday morning, and that
has led to an introduction of some snow mention in the far north
early Saturday morning. If the 12Z models are correct, our
temperature forecast is likely too warm, and there may be more of
a concern for measurable snow Saturday. Will have to wait and see
what the models do with that cold surface high before getting too
excited about a brief bout of winter. On the flip side, if that
cold air does not make it to our area, thunderstorms may be more
of a concern than wintry weather.
The final system will move into the area on Monday. In the
progressive flow pattern, the surface high will push east of the
area allowing for south winds and nice warm, moist advection ahead
of/into this system. This should be an all liquid event, but there
is a brief mention of snow with the rain in the north early
Monday morning. The precipitation is not likely to begin until
later in the morning, so no issues expected at this time. Of
course if we are colder for the Saturday system and actually get
some snow, that could have an impact on the Monday system.
Lots to watch for in this is active week of weather. Stay tuned.
&&
.AVIATION...
Issued at 606 PM CST Mon Mar 6 2017
Main challenge with the 00z Tuesday WFO PAH TAF package will be
addressing winds and timing of main convective line of
thunderstorms. Following some of the trend from the day crew, kept
non-thunderstorm winds elevated, both sustained winds and wind
gusts through the evening and post convective line. The HRRR
guidance had a reasonable solution for wind gusts through the
evening, most of it due to surface pressure gradients.
Though it is rarely used in the presence/proximity of convection,
could not eliminate the use of wind shear outside of the main
convective line during the first 3-15 hours of the forecast
period. There is sufficient shear within the layer that could
support significant wind concerns for flights traveling in these
evening, even with gradient winds at the surface.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
SHORT TERM...DH
LONG TERM...DRS
AVIATION...Smith
Area Forecast Discussion
National Weather Service Pueblo CO
705 PM MST Mon Mar 6 2017
.UPDATE...
Issued at 704 PM MST Mon Mar 6 2017
Have allowed Red Flag Warning to expire for this evening.
UPDATE Issued at 603 PM MST Mon Mar 6 2017
Updated for expiration of winter weather and high wind highlights.
Will let red flag warning run for another hour as still a few
spots on the plains are below 15 percent rh as of 01z.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 346 PM MST Mon Mar 6 2017
Upper trof is pushing eastward and tight surface pressure
gradient is expected to relax through the evening. We still have a
window for high winds through 6 PM across the southeast mountains
and plains though did trim the western areas a bit where high res
models suggest main threat is done. Otherwise...critical fire
weather conditions will continue until 7 PM after which time
relative humidity values will come up above critical thresholds.
It will remain windy all night across the higher mountains. In fact
mountain top winds across northern sections of the forecast area
(Pikes Peak...the Sawatch and Mosquito Ranges) may approach high
wind criteria again by Tuesday morning. However cross-sections keep
stronger winds aloft and do not look particularly favorable for
mountain wave activity due to too much forward shear. Will have to
watch this potential closely however as the latest hrrr run tries to
spread some strong gusts down into the higher elevations of the
rampart range towards 15z. For now it appears to stay below high
wind criteria.
On Tuesday...another round of critical fire weather conditions can
be expected across the plains...mainly north of highway 50...though
western parts of Pueblo county and eastern Fremont county will also
hit criteria on the west side of the surface lee trof. Conditions do
not look as volatile as today...with wind gusts in the 25-30 mph
range. Also appears that the window for critical fire weather
conditions will be shorter in duration. Have upgraded the Fire
Weather Watch to a Red Flag warning with the addition of Fremont
county...mainly for eastern portions. Temperatures on Tuesday will
remain above average for most areas.
Dry and warmer weather will return for Wednesday though winds should
remain lighter and below critical fire weather thresholds. -KT
.LONG TERM...(Tuesday night through Monday)
Issued at 346 PM MST Mon Mar 6 2017
Wednesday night through Friday...Nearly zonal westerly flow across
the region should keep dry and warm conditions in place through at
least the first half of Friday. Expect max temps in the 50s and 60s
for the high valleys, and in the 70s to near 80F for the eastern
plains.
Friday night through Monday...A couple of disturbances aloft will
track across the Intermountain West and Northern Rockies over the
weekend and into the start of the next work week. Look for isolated
to low-end scattered pcpn chances along the ContDvd, with the best
chance for new snow falling across the central mts. High temps are
forecast to be in the 50s and 60s for most low to mid elevation
locations each day, climbing to near 70F for the plains Sun and Mon.
Moore
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 346 PM MST Mon Mar 6 2017
VFR conditions expected at the terminals through the next 24 hours.
Main concern will be the winds with west winds gusting to around 35
to 40 kts at KCOS...KPUB...and KALS until 02z. Winds will gradually
decrease through the evening...though will remain at around 10-15
kts through the night at both KCOS and KPUB. Winds will increase
again on Tuesday with West to Northwest winds 15-25 kts affecting
both KCOS and KPUB during the late morning/early afternoon. KALS
should see light winds under 15 kts on Tuesday.
Across the mountains IFR to LIFR conditions will persist across the
continental divide due to snow and blowing snow through the evening
with improving conditions expected towards morning. -KT
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 10 AM to 5 PM MST Tuesday for COZ222-
226>228-231-234-236.
&&
$$
UPDATE...PETERSEN
SHORT TERM...KT
LONG TERM...MOORE
AVIATION...KT
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Tuesday)
Issued at 218 PM CST Mon Mar 6 2017
Intense upper trough working east across the Northern Rockies with
a smaller-scale wave swinging southeast into the High Plains. Dryline
had pushed through Concordia at 20Z with dewpoints in eastern Kansas
still in the mid to upper 50s despite intense mixing. Deep west to
southwest flow behind the dryline leading to some blowing dust to
the west and northwest, but cold front was not far behind with
northwest winds into Phillipsburg at 20Z.
On the large scale, winds continue to be the main story. HRRR has
been fairly close with trends over the past few hours and has been
hitting at gusts topping 50kts in north central Kansas in the late
afternoon. Latest runs backing off of the extent and coverage of
this however, and given observations to the west, will continue with
the Advisory into the early evening.
Storm chances still looking rather good with CIN diminishing and
dryline and front coming in. Obviously lots of deep shear is in
place, with some veering for storm organization. Early storms should
still be able to be discrete at least initially, but increasing
forcing should bring a more linear mode toward evening. Enough low
level shear for a tornado risk with the early storms too, and with a
slightly slower dryline trend, the time for tornadogenesis in this
area is increasing, though mitigated by right moving supercell
motions around 45kt. The early evening will bear close watching for
severe storms, with the front`s progression through the area by late
evening ending storm chances.
.LONG TERM...(Tuesday night through Monday)
Issued at 218 PM CST Mon Mar 6 2017
By Tuesday, the mid-level trough axis will be shifting east of the
area with northwesterly flow aloft still in place across the
Northern and Central Plains. At the surface, low pressure will
extend across the Northern Plains with high pressure tracking into
Oklahoma and Texas. Models show a pressure gradient remaining in
place over the region through the day, resulting in breezy westerly
winds. These strong winds combined with dry conditions will lead to
another day of extreme fire weather conditions for the entire
outlook area. See the Fire Weather section below for further
details. While these westerly winds will result in cooler
conditions for Tuesday, high temperatures will still be above the
seasonal normals in the upper 50s/low 60s.
Dry conditions will continue through mid-week as northwest-to-
southeast oriented zonal flow sets up over the central U.S. With
surface high pressure advancing into the southeastern U.S., a
warming trend is expected Wednesday and Thursday as winds shift to
the south, pushing high temperatures back into the mid 60s to low
70s. There is a chance for some scattered showers and isolated
thunderstorms Thursday afternoon into Thursday evening across east
central KS as a front slides southward over the area. Cooler
conditions are expected by Friday as expansive surface high pressure
builds from the Northern Plains southward into the Central Plains
behind the exiting front. This cooling trend will continue into the
weekend as a mid-level trough dives into the Central Plains with
northerly winds keeping high temperatures only in the mid 40s to low
50s. By early Saturday morning, models show two disturbances: one
across the Northern Plains in association with the mid-level trough,
and the second over Oklahoma as surface low pressure lifts
northward. Models show these two disturbances converging over the
CWA early Saturday morning with precipitation tracking eastward out
of the area by the evening. With early morning temperatures
Saturday morning near the freezing mark around the KS/NE border,
there is the potential for a rain/snow mix across far northern KS
before transitioning to all rain by mid/late morning. The next
chance for precipitation may be Sunday night into Monday, however
the ECMWF keeps this system further north of the CWA while the
GFS/Canadian track it over the area. A rain/snow mix would be
possible once again over far northern KS Monday morning as
temperatures drop to near freezing.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 542 PM CST Mon Mar 6 2017
Broken line of TSRA to impact TOP and FOE in next 2 hours. Gusty
winds and brief MVFR/IFR anticipated. Winds again become the main
challenge with speeds picking up after 14Z.
&&
.FIRE WEATHER...
Issued at 218 PM CST Mon Mar 6 2017
Today: Very strong winds with falling RHs bring extreme fire
danger to mainly western and central locations through sunset.
Exact location of RH values falling below 20% is not certain, but
any trimming of the Warning would lead to a poor message at this
point.
A tight pressure gradient will remain in place over the region on
Tuesday, resulting in breezy westerly winds gusting upwards of 30-
40mph. Model soundings show very dry conditions in place over the
entire region with dewpoints generally in the teens. Despite
slightly cooler high temperatures (in the upper 50s to low 60s),
these low dewpoints will be enough to cause RH values to plunge into
the 14 to 18 percent range during the afternoon. The combination of
these dry conditions and gusty winds will result in extreme fire
danger conditions across the entire CWA. As a result, the Fire
Weather Watch has been upgraded to a Red Flag Warning for the entire
area.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM CST this evening for KSZ008>012-
020>024-034>038.
Red Flag Warning from 11 AM to 6 PM CST Tuesday for KSZ008>012-
020>024-026-034>040-054>056-058-059.
Wind Advisory until 8 PM CST this evening for KSZ008>012-020>024-
026-034>040-054>056-058-059.
&&
$$
SHORT TERM...65
LONG TERM...Hennecke
AVIATION...65
FIRE WEATHER...Hennecke/65