Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/01/17
Area Forecast Discussion
National Weather Service Denver/Boulder CO
934 PM MDT Sat Sep 30 2017
.UPDATE...
Issued at 922 PM MDT Sat Sep 30 2017
Lightning still going on in northwest CO between Craig and Meeker
this evening so have opted to extend isolated thunderstorm coverage
west of the Continental Divide into the early morning hours tngt.
Latest HRRR show some of the shower activity surviving the downslope
late tngt into Sunday morning and possibly moving Weld County so
have added isolated showers there. Localized bands of gusty winds
still occurring across parts of the Urban Corridor this evening
but these should gradually decrease the rest of the evening.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 341 PM MDT Sat Sep 30 2017
The leading edge showers is moving over the central and northern
mountains with thunderstorms approaching Aspen and the Grand Lake
area. The back edge of this shower activity is crossing the
western Colorado border now with all of the activity tracking in
an east-northeast direction. This shower activity is expected to
move out onto the plains during the early evening. Satellite
imagery shows a fair amount of cloud cover already over the plains
which will reduce the strength of surface based convection
through this evening. A few thunderstorms from elevated convection
will be possible, but no strong surface based thunderstorms are
expected. The latest HRRR shows most of the convection moving out
of northeast Colorado by 9 PM, but then another round of rain
showers after midnight. The latter showers may be related to the
approaching upper level jet, and will be the onset of tomorrow`s
expected precipitation. Model temperature fields keep the mid-
levels warm enough for snow levels to remain above 10,000 feet
overnight.
Tomorrow will feature a transition to showers being driven by the
upper jet and dynamics aloft as Colorado will be under
strengthening cyclonic westerly flow aloft. Mid-level temperatures
will be falling through the day with falling snow levels by
afternoon. Temperatures on the plains will remain mild as the
westerly flow aloft will be downsloping. Late in the afternoon,
banded precipitation will be on the increase.
.LONG TERM...(Sunday night through Saturday)
Issued at 341 PM MDT Sat Sep 30 2017
Main concern surrounds the potential for significant snowfall in
the northern mountains Sunday night through Monday. Models have
remained consistent with the overall pattern, but the details will
be what`s hard to pin down, as this event will be closely tied to
the resultant banded precipitation associated with the upper level
jet.
For Sunday night, cold advection kicks in across northern Colorado
with snow levels expected to drop to 7,000-8,000 feet for
locations near the Wyoming border, and down to 8,500-9,000 feet
along the I-70 Corridor. However, these numbers could change quite
a bit as the thermal gradient under the jet is sharp. While
moisture is somewhat limited, it`s still moist and large scale
forcing is present as noted in the Q-G fields. Lapse rates are
not terribly unstable with values of 5-6 C/km, but cross sections
show Conditional Symmetric Instability and potential for
convection. Not surprising given the proximity and positioning of
the upper level jet. As a result, we`ll be increase PoPs and QPF a
bit more for this period. Snow accumulations are expected to be
heaviest where it`s coldest and banded convection should be more
persistent, generally just north of the I-70 Corridor at this
time. We`ll issue a Winter Storm Watch for the northern tier of
mountains including the Rabbit Ears Pass and Rocky Mountain
National Park area where potential for 8-16 inches of snow. Snow
level should hit the valley floor of Jackson county by Sunday
night, and given the banded convective potential there will also
issue the watch for North Park.
On the plains, we have potential for a couple strong/severe storms
over the eastern plains into Sunday evening. Then more widespread
showers should develop behind the cold front through the course of
the evening. Points generally along/north of I-76 should see
higher and perhaps widespread coverage of showers into Monday
morning. Temperatures will turn much cooler, and hard to say
exactly how much warming we`ll see Monday with increasing
baroclinicity along a surface cyclone. Stratus usually intensifies
these situations keeping cold air near the foothills.
By Monday night, precipitation is expected to decrease later in
the night as weak subsidence builds over the forecast area.
For Tuesday through the end of next week, we should see gradual
moderation in temperatures as drier southwest flow aloft develops.
A chance of storms should return by Thursday or Friday with a
return of mid level moisture.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 922 PM MDT Sat Sep 30 2017
Ceilings will be in the VFR range through Sunday afternoon. KFTG
radar still showing a locally stronger band of wind extending
from southeastern Boulder County into KDEN and KBJC at this time.
Stronger gusts of 20-25 kts still possible over the next hour or
so, but still expect the wind to decrease and shift more
southwesterly by late this evening. It may last longer at KBJC.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Sunday afternoon through Monday evening
for COZ030-031-033.
&&
$$
UPDATE...Cooper
SHORT TERM...Dankers
LONG TERM...Barjenbruch
AVIATION...Cooper
Area Forecast Discussion
National Weather Service Dodge City KS
600 PM CDT Sat Sep 30 2017
...Updated Aviation...
.SHORT TERM...(This evening through Sunday)
Issued at 332 PM CDT Sat Sep 30 2017
Water vapor and RAP analysis this afternoon showed a negatively-
tilted trough in the upper troposphere extending from Washington-
Idaho southeast into New Mexico. An axis of ongoing convection was
found along this trough axis per ENTLN data. In the low levels, a
cool and moist airmass existed across the High Plains from West
Texas and eastern New Mexico northward through western Nebraska.
There was quite a bit of stratus cover within this axis, although
breaks in the cloud were becoming more evident per satellite data.
Mostly clear sky was found across eastern Colorado, which allowed
SBCAPE to develop on the order of ~ 1500 J/kg. Nebulous convergence
along the lee trough axis across eastern CO will be the focus for
surface-based thunderstorm development late in the
afternoon/evening. These surface-based storms would not likely reach
far western KS until well into the evening, and they will be moving
into an increasingly stable airmass, as SBCAPE along the K-25
corridor was about 600-800 J/kg. There is somewhat greater
confidence in nocturnal thunderstorm development as the base of
the trough axis approaches southwest KS late tonight, leading to
enhanced low level warm advection. There are, however, some mixed
signals in convective-allowing models regarding placement, timing,
and even if coherent nocturnal thunderstorm development will
occur. Nevertheless, will have 30-40 POPs through the overnight
hours until 09-12Z time frame.
Going into Sunday, the entire trough axis out west will reconfigure
and become broader in areal extent with stronger west-southwest flow
aloft across Colorado and western Kansas. This will lead to stronger
leeside trough, increased pressure gradient, and stronger surfacer
winds. We should see 25-35 mph winds as a result in the afternoon,
with some gusts around 40 mph. Surface convergence along leeside
trough will foster isolated to widely scattered thunderstorm
development, mainly across northwest KS, and we will have some 20-30
POPs confined mainly to our northern counties along/north of K-96.
.LONG TERM...(Sunday night through Saturday)
Issued at 332 PM CDT Sat Sep 30 2017
An initial push of a surface front will occur Monday, however this
will quickly stall out across northwest KS, keeping southwest KS
region in the warm/moist (and windy) sector. Again, we will likely
see south winds in the 25-35 mph range with gusts 40-45 mph at
times. 850mb Temps of around +20C at DDC will support afternoon
surface temps well into the mid 80s. The next shortwave trough that
rounds the larger scale trough will move from Colorado Rockies into
western Nebraska, and this will put the greatest deep tropospheric
ascent well to our north. As a result, best organized strong/severe
thunderstorm cluster(s) will be in Nebraska and adjacent far
northern Kansas Monday Night. Highest POPs will again be confined to
areas along I-70.
Once this Monday Night shortwave trough ejects northward into the
Dakotas, the surface front will push south sometime Tuesday. The
front will slow down as yet another significant piece of energy in
the upper levels is left behind across the Great Basin region. This
is when our best precipitation chances will begin, going into
Tuesday Night and Wednesday, as low level moist southerly flow
converges with the quasi-stationary front to produce fairly
organized and widespread showers and thunderstorms. POPs of 50-60
percent are in the forecast Tuesday Night period, with 30-40 POPs
Wednesday. Wednesday looks cool and cloudy regardless of any
precipitation. The ECMWF and GFS both show this front to our south
dissolving and reforming back into central /northern Kansas as the
secondary Great Basin system develops into an upper low and induces
leeside cyclogenesis across eastern Colorado. The details become
increasingly noisy in the models after Thursday, with the ECMWF
faster with the next cool push (Friday) and the GFS being slower
(early Saturday). As long as the frontal zone(s) remain in the
vicinity through end of week, precipitation chances will remain in
the forecast for just about everyone across western and southern
Kansas.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 600 PM CDT Sat Sep 30 2017
High end MVFR (2500-3000 ft AGL) stratus cigs will prevail through
at least 12z Sunday, as strong south winds maintain moisture
advection from the south. South winds will remain elevated and
gusty also through the night, gusting 25-30 kts at times.
Shortwaves arriving from the west, embedded in the SW flow aloft,
are expected to trigger scattered convection overnight. Followed
the latest HRRR solution for thunderstorm timing, and VCTS/CB
placement in the TAFs. Models are not in good agreement on
convective placement, or even its existence, so did not include
TEMPO groups in the TAFs yet. If a coherent convective line does
materialize, TEMPO groups would be warranted. Any convection is
expected to clear SW KS by sunrise, with cigs improving during
the day Sunday. After 15z Sunday, strong S/SW winds will impact
aviation operations at all airports, averaging 25-35 kts.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 61 83 62 84 / 30 10 10 10
GCK 60 82 59 82 / 30 10 10 20
EHA 58 81 58 82 / 20 10 10 10
LBL 60 82 61 84 / 40 10 10 20
HYS 63 82 61 82 / 40 10 30 20
P28 61 82 64 86 / 20 10 10 10
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Umscheid
LONG TERM...Umscheid
AVIATION...Turner
Area Forecast Discussion
National Weather Service Sioux Falls SD
1039 PM CDT Sat Sep 30 2017
.SHORT TERM...(This evening through Sunday)
Issued at 328 PM CDT Sat Sep 30 2017
Scattered showers will continue to lift northeast across the region
into the early evening with weak mid level forcing working its way
through the heart of the forecast area. Do not expect more than a
tenth of an inch of rainfall for most locations, while south central
SD should remain largely dry. Later tonight we see more substantial
forcing lift north northeast out of western Nebraksa after midnight.
With the low level jet also intensifying at this morning, more
widespread shower activity will quickly spread across the region in
the warm air advection regime. We will also begin to see some
marginal elevated instability, so will continue to mention
thunderstorm potential. Breezy winds across the region this
afternoon will continue into the overnight hours, with gusts to 25
to 30 mph possible.
Shortwave lifts north of the region Sunday morning, which will allow
shower and thunderstorm activity to gradually diminish from west to
east. Models suggest that some destabilization will be possible
ahead of an approaching boundary Sunday afternoon in south central
SD. Speed shear looks strong enough to support severe weather in the
mid to late afternoon, however the question will be how much we will
actually be able to destabilize in this area. Will leave out
precipitation will remain in our west during the afternoon for now,
while some lingering afternoon showers and non severe thunderstorms
east of the James River. Highs will be tricky, with clouds and
precipitation in the area. Overall should see highs from the mid 60s
to mid 70s.
.LONG TERM...(Sunday night through Saturday)
Issued at 328 PM CDT Sat Sep 30 2017
By Sunday evening the main jet max nudges into the region and with
persistent warm air advection aloft and consistent disturbances
riding up in the he southwest flow, expected shower and thunderstorm
activity to expand in coverage. Instability will be waning into the
overnight hours however and thus suspect so will any severe risk
from earlier in the day. Some areas could pick up decent rainfall
amounts, around an inch or better, as the boundary remains parked
across our area.
Expect somewhat of a break during the daytime hours on Monday but
will still leave some chance mention of showers in there. Monday
night we see a resurgence of the warm air advection and favorable
dynamics aloft and thus a re-expansion of shower and thunderstorm
activity. Instability profiles are lacking in impressiveness but
probably sufficient enough given strong shear to have at least a
chance of an isolated strong to severe storm during the late
afternoon and evening hours across our eastern half or so. The other
issue will again be the flow parallel to the mid-level front leading
to another shot of healthy rainfall across the region. Similar to
Sunday evening, the exact location of heavier rainfall is still
somewhat uncertain dependent where heavier bands ultimately set up.
Regardless, the GEFS climatology situational awareness tables show
the potential for some locations to pick up quite a bit of rain over
this period. Both the heavy rain threat and severe weather threat
are represented well in the Day 3 slight for excessive rainfall from
WPC and Day 3 marginal for severe weather from SPC.
Tuesday the northern branch of the main parent upper level trough
breaks off and begins to move east through North Dakota and
eventually pulls the boundary to the south and east somewhat. The
Canadian looks to be an outlier with its evolution of this and keeps
rain chances around for longer on Wednesday and thus have trimmed
back these chances some. Thursday could have some small precip
chances along the Neb/SD boarder with more widespread chances
returning by Friday and into the weekend as the main trough ejects
into the plains.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1034 PM CDT Sat Sep 30 2017
The same concerns still hold true for the 06Z TAF set. A
disturbance will lift northeastward from central Nebraska
impacting our CWAs weather late tonight and early Sunday with
showers and embedded thunderstorms. The timing in the 06Z TAFs
will reflect a blend of the NAM and HRRR for convective trends,
primarily lasting from about 09Z to 14Z Sunday. It still appears
that KSUX may remain VFR except perhaps for some short term reduced
visibilities in the stronger showers around sunrise Sunday.
However the latest indications still show a trend toward MVFR
conditions at KFSD and KHON late tonight through about midday
Sunday. Lastly, KFSD and KSUX will likely experience 25 knot gusts
or a little stronger midday Sunday and Sunday afternoon.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
SHORT TERM...
LONG TERM...Kalin
AVIATION...MJ
Area Forecast Discussion
National Weather Service Goodland KS
600 PM MDT Sat Sep 30 2017
.UPDATE...
Issued at 551 PM MDT Sat Sep 30 2017
Just completed an update. Currently a cluster of storms is moving
in from southeast Colorado. Also not a lot of activity near the
northwest corner of the area per the previous grids. The Hrrr was
catching the current trends the best which also fits where the
best and deepest lift is in place. So pulled the highest pops
further south and east through the middle of the night.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 215 PM MDT Sat Sep 30 2017
Weak shortwave trough will eject northeast out of the central
Rockies this afternoon and tonight providing weak lift. Lee trough
draped across northeast Colorado will be likely location for
initiation, with storms racing northeast at 30 kts with the mean
flow. Persistent clouds have somewhat limited instability, but
latest analysis still shows weak to moderate CAPE across the area,
best in northeast Colorado where it cleared earlier. Deep layer
shear is marginally conducive for organized updrafts at 20-30kts.
So, a marginal risk seems about right for the late afternoon
through evening hours with the threats being hail up to the size
of quarters and damaging wind gusts with stronger storms.
Activity will weaken by mid to late evening with loss of surface
heating as it continues to move into Nebraska. Winds will be
breezy out of the south through the night, keeping temperatures
from dropping too much and making fog unlikely despite high dew
points.
The set up for Sunday is similar to today, though parameters are
better for severe weather. Another shortwave trough will rotate
out of Colorado, but stronger, and a surface cold front will sag
into the area by late in the afternoon, providing additional focus
for thunderstorms. Instability will be stronger, particularly in
the northeast part of the area from McCook to Hill City, and deep
layer shear will be 50-60kts. SPC has accordingly increased the
risk for severe weather to slight, with large hail, damaging winds
and maybe a tornado with any supercell that may develop given the
strong shear. Severe chances will probably be best along the
Kansas and Nebraska border area, which is where the front will be
located by late afternoon. It will continue to be breezy south of
the front, but slacken a bit on the cool side. Temperatures will
warm into the upper 70s to lower 80s south of the front and lower
to middle 70s north.
.LONG TERM...(Sunday night through Saturday)
Issued at 133 PM MDT Sat Sep 30 2017
Wet weather continues in the long term period with a deep trough
over the western portion of the country and a ridge to the east,
placing the High Plains under southwesterly flow aloft.
A cold front pushes into the region on Sunday and is the focus for
shower and thunderstorm development Sunday night. The potential for
severe thunderstorms persists into the evening hours with
instability in place and ample shear. Supercells will be possible
with large hail and damaging winds as the main threats. A tornado
cannot be ruled out into the early evening.
The cold front stalls over the area and regresses on Monday,
providing forcing for thunderstorms again in the afternoon and
evening. With continued shear and increasing instability, a few
strong to severe storms are possible. A similar set up is expected
on Tuesday with the location of convection depending on the
placement of the front.
Precipitation chances linger into Wednesday as the front slides
southeast of the region. Meanwhile, a closed low develops over the
Rockies and travels east across the northern and central Plains
through the end of the work week. This system brings another
opportunity for showers and storms to the area. Conditions dry out
on Saturday behind the late week system. With differences in
guidance, will continue to monitor how models handle the development
and progression of the northwestern trough during the extended.
There is a wide range in high temperatures on Monday (60s/70s) and
Tuesday (50s/60s) due to the front nearby. This is followed by a
warming trend with highs climbing from the 60s on Wednesday to the
70s on Saturday. Lows generally stay in the 40s and 50s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 551 PM MDT Sat Sep 30 2017
For Kgld, a cluster of thunderstorms will move near and affect the
site per latest radar trends and the latest Hrrr which is
catching this nicely. So inserted thunderstorms into the forecast
from 02z to 04z with some mvfr visibilities possible. Otherwise
southerly winds of near 20 knots with gusts to near 29 knots will
continue through the night. Low level wind shear will also be in
place through most of the night. Southerly winds will start
gusting to near 20 knots beginning at 19z. Thunderstorms look to
not affect the site again until after this period.
For Kmck, not as certain that thunderstorms will affect this site
as Kgld. So only inserted vcts from 04z to 06z. Southerly winds
of 15 to 20 knots with gusts to near 25 knots, along with low
level wind shear, are expected through the night. During the day
south to southeast winds near 12 knots are expected. No
thunderstorms are expected during the daytime.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...BULLER
SHORT TERM...024
LONG TERM...JBH
AVIATION...BULLER
Area Forecast Discussion...UPDATED
National Weather Service Jacksonville FL
810 PM EDT Sat Sep 30 2017
.UPDATE...
Sfc low continues to spin near the east central FL coast...just
south-southeast of Flagler Beach this evening...with slow movement
to the south in the past few hours. This trend is noted in recent
HRRR model runs for the overnight period. Heaviest showers and
storms have transitioned a bit offshore in the past few hours but
additional development of convection is over central FL recently.
There is a good possibility some of the heavier showers and
storms may move ashore on Sunday...mainly south of Duval County.
Overall, no significant changes to the POP Forecast at this time.
Reports of sustained winds of 20-25 mph and gusts to 40 mph along
the coast prompted starting the wind advisory earlier. Given the
stronger winds have also began high surf advisory this evening
with St Augustine buoy and Fernandina Beach buoy reporting 7 to 10
foot seas this evening.
&&
.AVIATION...
No significant changes to the TAFS this evening. MVFR to IFR
restrictions in passing waves of showers expected through Sunday
evening with the most persistent restrictions along the coast.
Localized heavy rainfall could lower restrictions briefly to LIFR
which did occur at VQQ earlier today, but overall trend will be
MVFR to IFR overnight tonight. Strong ENE winds will near
sustained 15-20 kts with gusts 25-30 kts at coastal sites tonight,
with much lighter winds inland for GNV.
&&
.MARINE...Have included all coastal waters in a gale warning for
the CWF update...with CMAN SAUF1 reporting sustained winds of
27-30 kt and gust to 36 kt. Gusts near 35-38 kt also reported by
trained spotters on the Flagler county coastline.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 65 75 64 81 / 20 10 10 10
SSI 76 77 73 81 / 40 30 20 30
JAX 74 77 71 81 / 70 70 30 20
SGJ 76 79 73 81 / 90 90 50 20
GNV 73 80 70 82 / 60 70 50 20
OCF 73 83 71 84 / 50 70 30 20
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through Monday evening for Coastal Duval-
Coastal Nassau-Flagler-St. Johns.
Wind Advisory until 8 PM EDT Sunday for Coastal Duval-Coastal
Nassau-Flagler-St. Johns.
High Surf Advisory until 11 PM EDT Sunday for Coastal Duval-
Coastal Nassau-Flagler-St. Johns.
Flood Watch through Sunday evening for Clay-Coastal Duval-
Flagler-Inland Duval-Putnam-St. Johns.
Coastal Flood Advisory until 8 PM EDT Monday for Clay-Coastal
Duval-Flagler-Inland Duval-Putnam-St. Johns.
GA...High Rip Current Risk through Monday evening for Coastal Camden-
Coastal Glynn.
Wind Advisory until 8 PM EDT Sunday for Coastal Camden-Coastal
Glynn.
High Surf Advisory until 11 PM EDT Sunday for Coastal Camden-
Coastal Glynn.
AM...Small Craft Advisory from 4 AM Monday to 3 PM EDT Tuesday for
Coastal waters from St. Augustine to Flagler Beach FL out
20 NM-Waters from St. Augustine to Flagler Beach FL from 20
to 60 NM.
Gale Warning until 4 AM EDT Monday for Coastal waters from
Altamaha Sound to Fernandina Beach FL out 20 NM-Coastal
waters from Fernandina Beach to St. Augustine FL out 20 NM-
Coastal waters from St. Augustine to Flagler Beach FL out
20 NM-Waters from Altamaha Sound GA to Fernandina Beach FL
from 20 to 60 NM-Waters from Fernandina Beach to St.
Augustine FL from 20 to 60 NM-Waters from St. Augustine to
Flagler Beach FL from 20 to 60 NM.
&&
$$
Shashy/Peterson/Corless
Area Forecast Discussion
National Weather Service Mobile AL
955 PM CDT Sat Sep 30 2017
.DISCUSSION...See updated information for land areas below.
&&
.UPDATE...Adjusted PoPs for the overnight as radars still continue
to indicate scattered showers and isolated thunderstorms moving
east across the coastal counties of Alabama and the western
Florida panhandle. HRRR indicates that this trend will continue
through around 4 AM Sunday morning, so will now include chance
PoPs for coastal counties through that time. Otherwise, no changes
to current overnight forecast. 12/DS
&&
.PREV DISCUSSION... /issued 645 PM CDT Sat Sep 30 2017/
DISCUSSION...Updated for latest aviation discussion below.
AVIATION...
00Z issuance...Isolated showers will dissipate this evening with
VFR conditions expected overnight and on Sunday. Easterly winds
will increase to 10-15 knots with higher gusts by Sunday
afternoon. /13
PREV DISCUSSION... /issued 423 PM CDT Sat Sep 30 2017/
NEAR TERM /Now Through Sunday/...Increased deep layer moisture
associated with a weak shortwave impulse moving westward over the
area in addition to convergence along a weak seabreeze is resulting
in the development of isolated to locally scattered rain showers
over interior south central Alabama as well as coastal portions of
the CWA this afternoon. We will keep a 20-30% chance of showers and
possibly a thunderstorm in the forecast through the early evening
hours, with the best chance over southern portions of the forecast
area. Isolated to scattered showers during the overnight period look
to become focused near the coast and offshore. Lows tonight are
expected to range in the mid to upper 60s inland and in the lower
70s near the immediate coast and beaches.
A surface ridge of high pressure will become oriented from the Mid-
Atlantic region to the southeastern U.S. Sunday, while a wave of low
pressure begins to track westward across the north central Gulf of
Mexico. The resultant MSLP gradient will bring breezy easterly winds
of 10-20 mph inland, and 15-25 mph near the immediate coast. Gusts
could approach advisory criteria near the immediate coast and
beaches Sunday afternoon. Later shifts will monitor for that
potential. Otherwise, the bulk of deep layer moisture remains
focused from near the coast to the offshore waters Sunday. We will
keep a slight chance of rain in the forecast south of the I-10
corridor, with dry conditions inland Sunday. Highs Sunday afternoon
should range from the lower to mid 80s. /21
SHORT TERM /Sunday night Through Tuesday night/...An upper level
ridge will build along the Eastern seaboard, helping to build a
surface high over the Mid-Atlantic region. In combination with a
weakly organized surface low over the Bay of Campeche, strong
easterly flow will continue over the northern Gulf of Mexico and
southern third of the land portion of the forecast area, easing a
bit as one moves inland. With this, guidance is indicating very
strong easterly flow setting up beginning Sunday along and south
of the I10 and lasting into Tuesday. Feel a wind advisory will be
needed for Monday, mainly along and south of I10, but this
issuance will come in later shifts. Also, with the strong easterly
flow, the need for a coastal flood advisory will need to be
accessed. More on this in the "Coastal Hazards" section. A
shortwave moving west just south of the northern Gulf coast will
work with the strong easterly to bring a chance of rain to mainly
marine and southern portions of the land area (due to the
shortwave passing just south of the coast) Sunday night into
Monday night, with highest PoPs being Monday.
Looking at the chance of any severe weather, model sounding show
enough instability for tsra to develop, especially more so the
farther south one goes in the forecast area. The instability will
be limited, though, and with little upper support to help non
existent, well well-developed severe thunderstorms are not
expected. Do feel small spinners will be possible along and south
of the coast, especially in light of the strong low level winds.
On to temps, with the increasing cloudiness and strong mixing from
the winds, a tighter than seasonal diurnal temp range is expected
Sunday night through Monday night. Overnight low well above
seasonal expected, ranging from low 60s inland to mid 60s along
the AL/FL state line. From there, overnight lows quickly increase
to low to mid 70s along the immediate coast. Highs in the low to
mid 80s expected, especially due to subsidence from building
upper ridge. By Tuesday, highs rebound a bit with the high
building even more and skies clearing as the shortwave moves west
of the area. Highs in the mid 80s expected, with lows in the mid
60s to low 70s along the coast.
/16
LONG TERM /Wednesday Through Saturday/...The upper ridge over
the East shifts southwest as upper energy digs south over SE
CA/NE Conus. This ridge remains in control of temps through the
Friday, keeping temps well above seasonal. From there, guidance
diverges into the coming weekend, with the GFS bringing shortwave
energy north over the eastern Gulf whilst the ECMWF keeps any
shortwave energy east of the Fl peninsula. The current forecast
brings a small chance of rain back in for Saturday, but slows it
down more in line with the ECMWF. Temps remain well above seasonal
levels.
/16
COASTAL HAZARDS...A period of increased easterly flow will result
in tidal levels running about 1 to as much as 1.5 feet above normal
levels mainly as we go into Monday and Tuesday. These increased
levels may result in the potential for minor coastal flooding along
the Alabama bay and sound shorelines (particularly east-facing) both
days. Later shifts may consider the issuance of a Coastal Flood
Advisory within the next 12-24 hours. The rip current risk also
becomes moderate, possibly high, Sunday into Tuesday, with surf
heights along area beaches increasing to 3-5 feet during this time
frame. /21
MARINE...An increasing pressure gradient between a ridge of high
pressure building over the southeastern states and a wave of low
pressure moving westward across the north central Gulf of Mexico
will result in increasing easterly flow and building seas over the
marine area late this weekend into the middle of next week. Winds
and seas will be at small craft advisory levels early Sunday morning
and will persist through at least early to mid next week. We will
keep the Small Craft Advisory in effect offshore, and also add Lower
Mobile Bay and the Mississippi Sound. The advisory will likely need
to be extended past Monday with later issuances. Occasional gusts to
around gale force will also be possible well offshore Sunday and
Sunday night. Seas build to 5-8 feet near shore and 7-10 feet well
offshore Sunday into early next week. /21
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...Small Craft Advisory from 1 AM Sunday to 7 AM CDT Monday for
GMZ631-632-650-655-670-675.
&&
$$
This product is also available on the web at:
http://weather.gov/mob
Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
1056 PM CDT Sat Sep 30 2017
.SHORT TERM...(This evening through Sunday)
Issued at 325 PM CDT Sat Sep 30 2017
RAP h5 analysis shows a broad longwave trough across western North
America with an upper ridge moving into the Great Lakes. There are
three waves rotating around the trough. The fist is pushing into
northwest MN this afternoon, the next is coming up out of northeast
Nebraska, while the main one is just now pushing out of the 4-
corners region. At the surface, the pressure gradient is tightening
between a 1004 mb low over eastern Montana and a 1032mb high over
the Great Lakes. This is resulting in strengthening SE surface winds
that are advecting in a fair amount of dry low level air that is
undercutting a lot of the mid-level moisture we see streaming in.
For the short term, the CAMs are in fairly good agreement on there
being two main batches of precip tonight/Sunday associated with the
Nebraska and then 4-corners wave. The Nebraska wave will be
struggling with dry low levels, much like the wave in NW MN did.
However, like we saw with the wave over NW MN, we`ll see a
few areas with high enough precipitation rates to occasionally get
some light rain down to the surface. Like the idea of the HRRR that
we see scattered showers move into the upper MN River Valley a
little before 00z, that push into the St. Croix river valley shortly
after midnight.
Our main precipitation though maker is that wave currently down by
the 4 corners. This wave will be moving up through western MN Sunday
morning, and will be crossing the international border in northwest
MN by the end of the short term period. Given strong agreement in
the CAMs with widespread rain and embedded thunderstorms breaking
out across western MN by the start of the day Sunday, we did boost
pops up into the categorical range for the morning in western into
central MN. Going into the afternoon, confidence in precipitation
coverage begins to decrease. As the main upper wave forcing the
rain in western MN pushes off farther to the northwest, the upper
forcing leading to the rain in western MN will begin to diminish as
this area of rain tries pushing into eastern MN/western WI. The
NAMnest is most bullish with holding rain together to the I-35
corridor in the afternoon, but the NMM/ARW/NSSLwrf all show precip
coverage really falling off through the course of the afternoon as
the forcing starts to not be strong enough to overcome the dry low
level air. As a result, the categorical pops Sunday morning in
western MN are held back in the 30s/40s for eastern MN and western
WI in the afternoon.
.LONG TERM...(Sunday night through Saturday)
Issued at 325 PM CDT Sat Sep 30 2017
The longer term concern s remain the timing and development of
the western CONUS trough and attendant cutoff circulation.
Deterministic models continue to trend the surface boundary
developing east into central MN by Monday. Favorable southwest
flow aloft over the boundary and short wave trough moving through
will bring a good likelihood of showers and possible thunder over
much of the area sunday into into Tuesday. Forecast PW`s continue
to trend above 1.5 inches along the boundary later Monday/Monday
night and this looks like the best chance for heavier rains and
scattered thunder. At the moment we have QPF totals Sunday through
Tuesday over 2.5 inches southwest to northeast in about a 60 mile
wide band from Redwood Falls to St Cloud. Most of the rest of the
area will see around an inch accumulation during this period.
Overall, the blended model temperatures looked reasonable and were
finally raised Monday night to the 60-65 degree range east of the
front.
Model trends continue to indicate the northern stream wave will
move across the area Tuesday night and should be enough to push
the front to the east of the area. We did collaborate trimming
PoPs some for Wednesday. The secondary cutoff circulation is
another issue with models handling timing and ejection east over
the central CONUS. It appears it will depend on the strength of
the eastern North Pacific trough which moves into the northwest
later in the week. The GFS seems to be a more likely solution with
the cutoff being forced east later Friday and across the area
into next weekend. It remains to be seen how far north it will
affect the area. Pretty much left the blended guidance PoPs alone
this period.
It does appear after this secondary tough departs a more amplified
deeper trough will develop over Canada and the northern tier of
the country. This should bring even cooler conditions into the
early part of the second week in October.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1056 PM CDT Sat Sep 30 2017
Scattered showers across MN will continue for much of tonight.
VFR conditions expected until mid morning or later Saturday across
western MN when MVFR cigs develop near AXN. Widespread rain
expected by Sunday morning across the western half of MN, breaking
up by evening as it heads toward WI.
KMSP...There may be some scattered showers around tonight, but
the better chance will hold off until Sunday afternoon.
/OUTLOOK FOR KMSP/
Mon...MVFR. SHRA Likely, chc TS. Winds S 10G20 kts.
Tue...MVFR. SHRA Likely, chc TS. Winds SW bcmg NW 10-15G25 kts.
Wed...VFR. Chc MVFR/-SHRA. Winds WNW 5-10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...MPG
LONG TERM...DWE
AVIATION...BORGHOFF
Area Forecast Discussion
National Weather Service Pueblo CO
343 PM MDT Sat Sep 30 2017
.SHORT TERM...(This evening through Sunday)
Issued at 344 PM MDT Sat Sep 30 2017
Active weather out west today as thunderstorms continue to develop
along/ahead of the upper trof axis progged by models to swing
through CO late this afternoon through this evening. Clouds and
precipitation have limited warming across the mountains and portions
of the I-25 corridor this afternoon. CPW webcam has been showing
off and on heavy snow at times though roads have remained mostly
wet. Given lack of instability, thunderstorms diminish as they move
off into the San Luis Valley and southeast mountains. However,
latest HRRR indicates some stronger convection may develop east of
KPUB late this afternoon through this evening. Model soundings
showed a bit of a cap across the far southeast plains initially, but
with cooling aloft assoc with trof think there is the potential for
thunderstorms to develop along/ahead of the surface trof as forcing
approaches. SPC meso-analysis is showing around 1000 j/kg of mlCAPE
out that way. 0-6km shears will be increasing to around 30-40 kts
by 00z, so a strong to isolated near severe thunderstorm is still
possible across the southeast plains through early evening.
Precipitation will decrease this evening for most areas however with
more energy dropping into the base of the mean trof out west,
Continental Divide will see some isolated to scattered showers
through the night. Snow levels look like they will remain around
11.5-12kft.
Drier air moves in for Sunday with southwesterly winds increasing
for all areas as the surface low deepens and kicks eastward across
east central Colorado through the afternoon. Ordinarily would be
concerned for critical fire weather conditions, but with wet fuels
from recent rains, this threat has been mitigated. Area with best
chance for seeing precipitation will be across the central mountains
where a couple inches of accumulation above 12kft will be possible
through the afternoon. Will also have to watch for the potential of
a strong to severe storm or two along the dry line across the far
southeast plains. SPC has this area outlooked in a Marginal area and
with Nam12 CAPEs running up to 2000 j/kg and 0-6km shears in the 40-
50 kt range, this assessment looks good. Will all depend on how far
east low level moisture mixes out. Will maintain some isolated pops
across the far eastern areas to account. -KT
.LONG TERM...(Sunday night through next Saturday)
Issued at 344 PM MDT Sat Sep 30 2017
Primary meteorological challenges during the longer term include
but are not limited to temperatures, higher terrain snow amounts,
pops and gusty winds at times.
Recent longer term computer simulations, forecast model
soundings and PV/precipitable water analysis indicate that the
forecast district will be under zonal to southwesterly upper flow
during the longer term as closed upper lows remain well to the
north and west of southern Colorado during this time-frame.
Initial closed upper low situated over southern Idaho Sunday night
drifts into northern Utah Monday before splitting into
North Dakota and north-central California by later Tuesday. At
this time, it appears that this system will provide the highest
potential of precipitation over portions of the central mountains
from Sunday night into Monday and have depicted snow amounts
between 1 and 4 inches during this time-frame.
Then, the closed upper low centered over north-central California
later Tuesday is expected to move into southeastern Idaho by
sunrise Friday before moving across Wyoming Friday. Again,
primary precipitation focus with this system is expected to remain
west to north of the forecast district during this time-frame,
although northerly-northeasterly surface surges from Monday night
into Tuesday and then again from later Friday into Saturday will
be capable of providing isolated to scattered pops during these
time-frames.
Healthiest gradient winds during the longer term should be
experienced from Sunday night into Tuesday morning and then again
from Friday into next Saturday.
Finally, above seasonal early October minimum temperatures over
the forecast district should be noted during the balance of the
longer term, while maximum temperatures running within a category
or so of climatological averages are anticipated during the
longer term.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 344 PM MDT Sat Sep 30 2017
VFR conditions expected at the terminals through this
evening...though isolated to scattered showers and embedded
thunderstorms will cause a lower VFR cig at times. It does not look
likely that low clouds and fog will redevelop across the area
tonight as southwesterly winds aloft will be increasing. However
Continental Divide and higher peaks in the Sangres could see off and
on showers pinned up across the higher peaks through the night. It
will be drier tomorrow with breezy southwest winds 15 to 25 kts
spreading into all three terminals in the afternoon. -KT
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$