Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/21/18
Area Forecast Discussion
National Weather Service Gaylord MI
939 PM EDT Thu Sep 20 2018
.UPDATE...
Issued at 939 PM EDT Thu Sep 20 2018
Low pressure continues to deepen as it moves into the Upper
Mississippi Valley late this evening. Associated warm front is
steadily lifting northward thru Lower Michigan. Patches of
convection continue to develop well north of the warm front over
our area...now impacting the NE half of our CWA. So far...
convection of our CWA has been rather weak and disorganized. While
both instability and shear values are steadily increasing with the
approach of the warm front...instability is elevated and lack of a
focusing/organizing feature has greatly limited intensity. Focus
of organized convective development now turns westward along and
just ahead of the surface low and associated cold front within the
strong instability and 850 mb theta-E axes coincident with strong
shear values (effective bulk shear of 50+ kts) over Wisconsin. All
near term models tend to weekend this convection very late
tonight as it moves into our CWA in response to diminishing
instability with eastward progress. Latest SPC Day1 Outlook as
taken the SE half of our CWA out of the marginal risk as a
result...which is certainly reasonable. If any strong/marginally
severe storms do manage to hold together long enough to reach our
CWA very late tonight...damaging winds will be the primary severe
risk.
&&
.NEAR TERM...(Through Tonight)
Issued at 339 PM EDT Thu Sep 20 2018
...Occasionally wet with rising temps...
High impact weather potential...A few severe thunderstorms
possible, mainly after 11 pm.
1002mb low pressure is over ne Neb. Surface warm front is lifting
into far southern lower MI. Light rain lingers over much of ne lower
and eastern upper MI; precip is spottier in nw lower MI. More
vigorous sct showers are seen downstate. The low will move quickly
ne and deepen more rapidly, reaching western upper MI toward
midnight, and just ne of Superior by morning. This will allow
northern MI to enter the warm sector overnight, albeit not for very
long.
An impressive low level jet starts to crank up early this evening.
1km winds will increase broadly to 50-65kt by midnight. This will
rapidly advect a potentially unstable airmass northward into the
northern Great Lakes, and will result in chances for deep convection,
especially ahead of the oncoming warm front. Sct/nmrs showers
will redevelop early this evening over northern lower MI. There
could be a few rumbles of thunder, but overall updraft intensity
should be unimpressive. The increasing jet and incoming front will
shove activity northward toward upper MI toward midnight. Here,
HRRR runs are showing much more vigorous updrafts, including
supercell-like structures. This area features 0-3km helicity
values on the order of 500 m2/s2, and 0-6km bulk shear values of
60-70kt. Note that this is still north of the warm front; storms
will be elevated. MuCape values in 800-1000j/kg range should be
enough to support stronger storms, and a marginal svr hail threat
is possible, as supercell dynamics amplify updraft intensity.
After 4am, a pre-frontal squall line will try to push into the
region from the west. By then, instability will have further waned,
and one would think it will be a challenge for this activity to
hold together particularly well. But, the last few HRRR runs are
trending toward having stronger convection move into the region
overnight. So a localized svr threat (wind and hail) could still
come together here as well.
Temps will climb as we move thru the night, with pre-dawn readings
from the mid 60s far north to mid 70s in some parts of nw lower MI.
S to sw winds will increase tonight, with 30 mph gusts in eastern
upper and nw lower MI overnight.
&&
.SHORT TERM...(Friday through Sunday)
Issued at 339 PM EDT Thu Sep 20 2018
High Impact Weather Potential: Thunderstorm potential ending in the
morning into early afternoon. Possible frost Saturday and
Sunday morning.
The low pressure system mentioned in the previous forecast
discussion above will depart to the northeast. As the system departs
it`s cold front will sweep across northern Michigan Friday morning
producing more chances of rain showers and possibly a rumble of
thunder. These chances will continue throughout much of the day as a
post frontal trough approaches from the northwest with some synoptic
support above and lingering moisture. Southerly winds begin to veer
to the northwest behind said cold front by the end of the day and
continue to be very gusty, with some gusts nearing 35-
40mph...possibly locally higher...especially near the coast of the
Great Lakes. As aformentioned system above departs to the east, high
pressure and much drier air will move into the region...providing
precipitation free weather and cooler temperatures Saturday and
Sunday...possibly even some frost Saturday and Sunday mornings. The
frost Saturday will be dependent of course on the timing of the
clouds clearing and if winds decouple enough to allow temperatures
to drop to allow frost to form. Even though temperatures are progged
to be just a tad warmer...still believe that the normal "cool spots"
of interior northern lower could see some. Eastern upper may be
protected under some cloud cover from a very weak cold from
associated with a low pressure system over James Bay as it drops
south throughout Saturday night. Friday`s highs will generally be in
the mid 60s to low 70s. Saturday and Sunday will be much cooler,
only reaching into the upper 50s to low 60s behind the
aforementioned cold front. Lows will be in the upper 40s to low 50s
Thursday and Friday and mid to upper 30s Saturday morning.
.LONG TERM...(Sunday night through Thursday)
Issued at 339 PM EDT Thu Sep 20 2018
High pressure mentioned above will continue to dominate northern
Michigan`s weather through Monday. Looks like the pattern will once
again become active thereafter, with several disturbances that may
bring more chances of rain through the forecast area early to
midweek. It appears we may moderate a bit during the extended period
with a southerly component of the wind advecting some warmer
temperatures in the mid 60s to low 70s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 719 PM EDT Thu Sep 20 2018
A strong warm front will surge northward thru Northern Michigan
tonight associated with deepening low pressure currently moving
out of the Northern Plains and into the Upper Mississippi Valley.
Showers and thunderstorms will remain possible this evening...with
chances increasing overnight into Friday as the associated cold
front approaches and moves thru the region. Conditions will
decrease to MVFR and possibly IFR within heavier showers and
storms. Areas of fog and resulting MVFR/IFR will remain an issue
tonight along and north of the warm front. LLWS will develop
tonight as winds rapidly strengthen around this deepening system.
&&
.MARINE...
Issued at 339 PM EDT Thu Sep 20 2018
Strengthening low pressure will cross western upper MI and Lake
Superior overnight tonight. Sw winds will ramp up tonight,
especially overnight, before a strong cold front goes thru Friday
morning. That will veer winds to the west and eventually nw, with
gusts becoming stronger yet. Gale warnings remain up on all waters.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...GALE WARNING until 8 PM EDT Friday for LHZ345.
GALE WARNING until midnight EDT Friday night for LHZ346>349.
LM...GALE WARNING until 8 PM EDT Friday for LMZ323-341-342-344>346.
LS...GALE WARNING until 8 PM EDT Friday for LSZ321-322.
&&
$$
UPDATE...MR
NEAR TERM...JZ
SHORT TERM...TL
LONG TERM...TL
AVIATION...MR
MARINE...JZ
Area Forecast Discussion
National Weather Service La Crosse WI
1100 PM CDT Thu Sep 20 2018
.SHORT TERM...(This evening through Friday)
Issued at 236 PM CDT Thu Sep 20 2018
Surface analysis early this afternoon shows the area of low
pressure has progressed into northeast Nebraska with the warm
front stretched across northern Iowa. The warm front was just to
the south of the local area as observations showed the wind shift
and temperature jump with the front at KIIB and KDBQ at 18Z. As
the surface low continues to track northeast tonight, the warm
front will be synoptically pulled north by the low and should be
working north through the local area late this afternoon through
the early evening. Once the low and warm front are past the area,
the cold front tied to the low will then sweep across the area
during the evening and overnight hours. These features will pose
the severe weather threat through the evening hours.
While the hi-res meso scale models in general do not show any
activity developing along the warm front as it lifts north, not
entirely comfortable with this. The low level moisture transport
will be increasing ahead of the surface low and approaching short
wave trough. As this intersects the frontal boundary, it could
cause some activity to form along the front. The main activity
looks to be tied to the cold front where the forcing from the
short wave trough will be stronger. A line of convection is
expected to quickly from along the front over central Minnesota
into northwest Iowa and move east with the front. The expected
timing of this activity now looks to have it entering the western
sections between 7 and 8 pm and exiting the east after 1 am.
The ML CAPE will spread in behind the warm front with several runs
of the RAP suggesting 1500 to 2000 J/Kg will be in place ahead of
the cold front. Plenty of shear will be in place with up to 50
knots in the 0-6 km layer. Most of this looks to reside in the 0-1
km where there will be up to 40 knots with a slight increase up
through 3 km and then increasing a bit more through 6 km. Given
the expected line structure along the front, the main threat
should be damaging winds, but withe amount of low level shear, a
short-lived embedded tornado will be possible. Also concerned that
if the warm front does not progress as far north as expected, a
storm could latch onto it and ride along it with an increase
tornado threat. The storms should be able to produce a period of
heavy rain as an axis of 2 inch precipitable water will be in
place right along the front. However, given the north/south
orientation of the line and that it will be progressive, any heavy
rain should be rather short-lived at any given point and not be
enough produce any new or aggravate on-going flooding.
The system will be past the area for Friday, but cyclonic flow
around the surface low will keep the area covered in clouds for
much of the day along with a lingering shower chance in the
morning across the north in the morning. Much cooler air will be
ushered in with highs only reaching the upper 50s to lower 60s. It
will also be breezy with northwest winds gusting to around 30 mph.
.LONG TERM...(Friday night through Thursday)
Issued at 236 PM CDT Thu Sep 20 2018
With the cooler air and clearing skies Friday night, some low
temperatures in the 30s and frost will be possible across central
Wisconsin. The weekend then looks quiet with upper level zonal
flow and surface high pressure in place. Upper level troughing
then looks to move across the Upper Midwest early next week that
will push a cold front through with a chance for more rain from
Monday afternoon through Tuesday. There will then be some more
chances for rain Wednesday into Thursday as more upper level
troughing looks to impact the region.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday evening)
Issued at 1100 PM CDT Thu Sep 20 2018
Cigs: low cigs going to hang around into Friday afternoon, with
increasing decks and then clearing out for Friday night.
WX/vsby: -shra hanging around for a few hours into the overnight,
which could result in mostly mvfr vsby restrictions. With winds
staying brisk, don`t see a fog threat.
Winds: winds on the increase as pressure gradient tightens ahead of
approaching sfc low. Winds swing to the west/northwest later tonight
with the passage of systems`s cold front - staying strong and gusty
through Friday afternoon.
&&
.HYDROLOGY...
Issued at 236 PM CDT Thu Sep 20 2018
While there may still be some minor flooding issues ongoing across
Fayette, Clayton and Grant Counties, reports indicate the impact
are minimal and the areal flood warning will be discontinued.
Runoff from last night rains has caused some river rises with
active flood warnings along portions of Turtle Creek and the
Turkey and Kickapoo Rivers. See the latest flood statements for
the latest information.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...04
LONG TERM...04
AVIATION...Rieck
HYDROLOGY...04
Area Forecast Discussion
National Weather Service Denver/Boulder CO
754 PM MDT Thu Sep 20 2018
.UPDATE...
Issued at 754 PM MDT Thu Sep 20 2018
A cold front charging south across eastern Colorado will move
through the Denver area later this evening. Low level moisture
increases behind it and may bring low clouds after midnight. Best
chance for these low clouds will be upslope favored areas along
the foothills and Palmer Divide. Above this shallow moist layer,
the airmass is very dry. Clear skies and light winds later tonight
will lead to good radiational cooling. Mountain valleys will be
quite chilly tonight with lows mainly in the 20s. Other than a few
small changes to line up with current trends, will not make any
major adjustments to the forecast.
&&
.SHORT TERM...(This evening through Friday)
Issued at 317 PM MDT Thu Sep 20 2018
One last set of showers on the tail end of the passing upper
trough will move across Logan, Sedgwick and Phillips Counties
over the next couple hours. Elsewhere over the forecast area,
skies have been clearing out as dry air moves back into the region
and high pressure begins building into the region. A dry airmass
and clear skies should allow for decent radiational cooling, and
chilly temperatures in the morning. The exception will be around
the Denver area, where an area of low clouds are expected to
develop after midnight. This should hold Denver area temperatures
some 5-10 degrees warmer than the rest of the plains.
On Friday, after the morning clouds over the Denver area
dissipate, skies across northeast Colorado should be mostly sunny.
Temperatures will remain cooler than earlier this week, but highs
should still be around seasonal normals. A flat ridge aloft will
produce dry and moderate westerly flow aloft, while a surface high
pressure area building over the northern Great Plains will produce
southeasterly winds across the plains. Mountain areas will have
weak westerly winds as daytime heating mixes the flow aloft down
to the surface.
.LONG TERM...(Friday night through Thursday)
Issued at 317 PM MDT Thu Sep 20 2018
A flat upper ridge will continue to dominate the weather for the
forecast area Friday night through Sunday night. The flow aloft
will be west-southwesterly and pretty weak through Sunday morning.
It will get a bit stronger by Sunday night. The QG Omega fields
keep neutral synoptic scale energy over the CWA through Sunday,
then upward vertical velocity is on the increase Sunday night. The
low level winds appear to follow fairly normal diurnal patterns
Friday night through Sunday night. Moisture-wise, it will be
pretty dry through SUnday. Precipitable water values are in the
0.15 to 0.50 inch range Friday night through Sunday, then they
increase a bit Sunday night. There is nothing on the QPF fields.
Will continue with no pops in the GFE grids through Sunday, then
low pops for the far northwestern corner of the CWA Sunday night.
For temperatures, Saturday`s highs will warm 3-7 C above Friday`s
highs. Sunday`s highs will be 0-1.5 C warmer than Saturday`s
highs. For the later days, Monday through Thursday, some of the
medium range models have an upper trough move across the CWA
Monday into Monday night. Some of the models show it a bit slower.
After that there is upper troughiness to the northeast and east
of Colorado with cool northwesterly flow aloft for the forecast
area through Thursday. There is some moisture with the upper
trough, enough for some 10-40% pops Sunday night into Tuesday
night for some of the CWA. Wednesday and Thursday are pretty dry.
Temperatures now look to be below seasonal normals Monday through
Thursday, with Tuesday the coolest day.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 754 PM MDT Thu Sep 20 2018
Low level moisture will increase behind a cold front this evening
and bring a chance for low clouds after 06Z. Northeast upslope
winds should produce low cloud south and west of Denver. Still a
good amount of uncertainty if low clouds will develop over KDEN.
The past few runs of the HRRR keep the low clouds along the base
of the foothills west of Denver and over the Palmer Divide south
of Denver. This seems reasonable given the northeast surface
winds. Have a tempo for low clouds at KAPA with just few at KDEN.
&&
.FIRE WEATHER...
Issued at 317 PM MDT Thu Sep 20 2018
Relative humidities will be quite low over North Park and Middle
Park Friday afternoon, but flow aloft is only moderate and surface
winds are expected to remain lighter than 10 to 15 MPH. Dangerous
fire behavior is not expected.
There will be a couple of brief periods of elevated fire danger
conditions, mainly over northern Jackson and northwestern Weld
counties Saturday afternoon and again Sunday afternoon.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Meier
SHORT TERM...Dankers
LONG TERM...RJK
AVIATION...Meier
FIRE WEATHER...RJK
Area Forecast Discussion
National Weather Service Charleston SC
1039 PM EDT Thu Sep 20 2018
.SYNOPSIS...
High pressure will prevail into early next week. A coastal
trough of low pressure may impact the area by early to the
middle of next week. A cold front may then approach from the
northwest later in the week, and possibly stall over the area.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Late this evening: Radar imagery shows that showers have
developed sooner than expected across the Georgia waters and
have pushed into the Georgia coast south of the Altamaha. The
HRRR and RAP still don`t seem to know that this is happening and
feature completely dry conditions for the Georgia coast through
the next several hours. Have updated rain chances based on radar
trends to add in some 20 percent chances mainly for McIntosh
County. Otherwise, no notable changes.
Early this evening: Skies have cleared out with the loss of
diurnal cumulus and should remain that way for much of the
night. With the center of the surface high centered inland and
the development of subtle coastal troughing, some stratocumulus
development is expected across the coastal waters. Some of this
cloud cover could advect onshore, but the expectation is for
skies to remain scattered. The best chance for more cloud cover
and even isolate showers will be along the Georgia coast where
the most well-defined coastal troughing should setup. Lows
should dip to around 70 well inland, ranging to the mid 70s at
the coast.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
A deep layer of high pressure, centered over North Carolina,
will move slowly eastward into the Atlantic through the period.
Models have been very consistent with showing an easterly moving
east to west around the base of the ridge toward the area later
Sunday. Low chances for precip. will persist through Saturday,
with the only slight chance PoPs over the extreme southeast GA
region. By Sunday, deep layer moisture increases, and have gone
slight chance to low end chance PoPs most areas by afternoon and
evening.
Temperatures are expected to remain above normal, with highs in
the upper 80s to around 90s, and lows in the upper 60s inland
to lower to mid 70s toward the coast.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Aloft, high pressure will be centered northeast of the area
over the Atlantic through much of week. At the sfc, a front will
attempt to push south over the Mid-Atlantic states before
stalling north of the area on Monday. Shower and thunderstorm
chances are anticipated to increase early in the week as PWAT
levels increase to around 2.0 inches south of the stalled
front/boundary. However, the bulk of shower and/or thunderstorm
activity should arrive Tuesday and/or Wednesday as a wave of low
pressure/coastal trough shifts onshore. A large mid/upper
trough of low pressure is then expected to shift over the East
Conus by Thursday, helping force a cold front southwest into the
region by early next weekend. Given the setup, chances of
showers and thunderstorms could increase in coverage as the
front nears the area by early next weekend.
High temps will generally range in the mid/upper 80s across
Southeast South Carolina through much of the week. Some areas
could touch 90 degrees across Southeast Georgia. Overnight lows
should range in the upper 60s to around 70 degrees inland to
mid/upper 70s along the coast.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
VFR conditions are expected to prevail through 00z Saturday.
Late tonight, MVFR level stratocumulus could advect onshore
along the Georgia coast, but still expected the cloud deck to
remain scattered at KSAV. There could also be isolated shower
development over the coastal waters, but this activity isn`t
expected to impact either terminal.
Friday and Saturday: VFR conditions are expected to prevail at
both KCHS and KSAV terminals through Sunday. Isolated afternoon
showers and thunderstorms will be possible, mainly for KSAV.
Increasing deep layer moisture is expected Sunday night through
Tuesday ahead of an advancing easterly wave feature in the
Atlantic. Expect scattered showers and isolated thunderstorms,
especially during the afternoons, which could result in brief
flight restrictions.
&&
.MARINE...
Tonight: High pressure will persist with east winds 10-15 kt
and seas averaging 2-3 ft nearshore and 3-4 ft offshore.
Isolated shower activity across far southern Georgia coastal
zones cannot be entirely ruled out.
Friday through Tuesday: Current models keep winds/seas below
highlight levels through the period. A deep layer ridge will be
centered just north of the waters through Sunday, with easterly
winds of generally 15 knots or less and seas 2 to 4 feet. By
later Sunday and Monday, and easterly wave moves toward the area
from the east, and then possibly weakening as it moves into the
waters on Tuesday. Winds could increase to 15-20 knots ahead of
the wave Sunday night and Monday as the pressure gradient
increases between the wave and higher pressure well inland.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...BSH
SHORT TERM...RFM
LONG TERM...DPB
AVIATION...BSH/RFM
MARINE...JMC/RFM
Area Forecast Discussion
National Weather Service Grand Rapids MI
919 PM EDT Thu Sep 20 2018
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 256 PM EDT Thu Sep 20 2018
Thunderstorms are expected this evening as a warm front pushes
north. Some of these storms could be locally severe. A cold front
will arrive Friday morning along with strong wind gusts. Fair and
much cooler weather can be expected for the weekend.
&&
.UPDATE...
Issued at 920 PM EDT Thu Sep 20 2018
We were concerned that thunderstorms would redevelop near or just
north of the warm front after dark, northeast of Grand Rapids. As
it turned out that does not seem to be the case. I am thinking we
will still have to watch the line of storms from Minnesota to see
how it does crossing Lake Michigan after midnight. The lake is
still fairly warm, I could see the storms holding together better
then the models area forecasting them too. These storms would pose
threat for gusty winds and brief heavy rain if they make it into
our western CWA.
Friday will be rather windy, we may have to consider a wind
advisory but I will let the midnight shift think about that.
&&
.DISCUSSION...(This evening through next Thursday)
Issued at 256 PM EDT Thu Sep 20 2018
Active weather the next 24 hours as severe threat late today is
followed by strong synoptic winds on Friday. Then fair and much
cooler into the weekend.
There will be a window between late afternoon and early evening
when instability spikes close to 2000 J/kg along with a local max
of storm relative helicity just north of a front. This, combined
with low LCLs will yield the threat for quick hitting svr storms
with hail and a brief tornado possible. The threat should
continue into the evening then diminish as sfc based instability
decreases.
The synoptic wind threat begins after sunrise on Friday as mixing
in the dry slot brings down 30 to 35 mph wind gusts from late
morning into the afternoon. This looks like a marginal wind
advisory event but we will hold off on headlines for now.
There could also be a marginal frost advisory for the northern
zones Friday night. This will depend on the timing of clearing.
Surface dew points are progged to fall close to 0C as winds
decouple late at night, so clearing skies would mean some
scattered frost in the cold hollows.
After a spell of quiet weather, deep moisture return begins ahead
of strong cold front which could touch off strong storms on
Tuesday afternoon. There is currently good model agreement on the
timing of the front so confidence is currently higher than
average at that time range.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 749 PM EDT Thu Sep 20 2018
The afternoon convection seems to be dissipating as the sun sets.
There is 2000 to 3500 kt of cape over the SW GRR CWA but unlike
what both the NAMNEST and HRRR shows, no storms are developing
near or NE of GRR as of yet. Still it is possible so I did put
VCTS in the GRR taf till 03z for that. The squall line on the cold
front may or may not reach our TAF sites between 09z and 12z. I
have VCTS / VCSH for that. I expect low level wind shear tonight
so that is included in all of the TAFs. Behind the cold front I
expect gusty northwest winds to 35 knots at times. Near and west
of US-131 (MKG and GRR) I could see MVFR cigs due to lake effect
clouds.
&&
.MARINE...
Issued at 256 PM EDT Thu Sep 20 2018
Winds and waves will be increasing tonight and gales are expected
across north of Pentwater tonight and Friday. The Gale Warning and
Small Craft Advisory are unchanged with this forecast. Winds and
waves will decrease beginning Friday night and be much lighter
over the weekend.
&&
.HYDROLOGY...
Issued at 1217 PM EDT Thu Sep 20 2018
River levels are around to a little above normal for the time of
year. Levels are also steady or slowly falling. Rain and
thunderstorms this morning dropped over an inch of rain across
Ottawa, southern Kent, Ionia, and southern Clinton Counties. This
includes much of the Grand River basin. This should result in river
level rises which remain mostly below flood stage along the Grand
River.
More storms are expected tonight into Friday morning. Rainfall rates
in excess of one inch per hour are possible. This could lead to
additional localized flooding on roads, in low-lying areas, and
along small creeks. Drier weather is expected Friday afternoon
through Sunday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Gale Warning until 8 PM EDT Friday for LMZ849.
Small Craft Advisory until 8 AM EDT Saturday for LMZ844>848.
&&
$$
UPDATE...WDM
SYNOPSIS...Ostuno
DISCUSSION...Ostuno
AVIATION...WDM
HYDROLOGY...63
MARINE...Ostuno
Area Forecast Discussion
National Weather Service North Platte NE
612 PM CDT Thu Sep 20 2018
.SHORT TERM...(This evening through Friday)
Issued at 349 PM CDT Thu Sep 20 2018
The primary forecast challenges through tomorrow are temperatures
and precipitation as the cold front finally clears the area. A
secondary boundary and shortwave will be the forcing mechanisms for
additional storms this evening, while temperatures continue to cool.
This evening and tonight... One post frontal band of showers with
embedded storms is slowly pushing east across central Neb as of 20z.
Moisture convergence and mid-level speed convergence (notable at H7)
are helping feed this band of showers. Farther west across the
panhandle, isolated thunderstorms have developed ahead of the main
trough axis. Continued schc PoP through the evening, mainly across
SW Neb where weak instability exists. Short-term guidance and CAMs
have been handling the whole situation differently today, but
trended more toward the HRRR and HREF this evening as they`ve picked
up on the redevelopment of isolated thunder. After 03z or so,
subsidence really takes over across western Neb and expect clearing
skies. Visible sat shows the back edge near CYS to CDR, while sfc
obs indicate rapidly drying air (dew points in the 50s/60s in Neb vs
10s/20s in WY). NW winds gradually lighten overnight across the
panhandle and SW Neb, setting up efficient decoupling. Winds remain
elevated over north central Neb, which is closer to the main low.
Generally took a couple degrees off the previous forecast lows for
areas west of Hwy 83, resulting in upper 30s near the Pine Ridge,
lower/mid 40s NW Neb and upper 40s elsewhere.
Tomorrow... As a surface high settles over the northern Plains and
northerly flow slowly wanes at H85, looking at a clear and cool day.
General agreement exists among the model suite with continuing CAA
into midday as H85 temps drop to around 3C. Return flow begins late
in the day in the far west, which should help highs reach 70F.
Little recovery takes place north central Neb, where some places may
struggle to reach 60F.
.LONG TERM...(Friday night through Thursday)
Issued at 349 PM CDT Thu Sep 20 2018
Fair weather continues through the weekend as a weak upper ridge
tries to build over the Mississippi Valley. The pattern turns
potentially active next week as a large trough digs into the Western
U.S. and emerges onto the Plains. The state remains in northwest
flow for the rest of the week.
Saturday and Sunday... A steady warmup is in store with
strengthening south/southwest flow in the low levels and dry air
still in place. A thermal ridge slides up the High Plains on Sunday,
pushing H85 temps toward 25C. Western Neb tops 80F again Sat and
most (if not all) the area reaches lower/mid 80s on Sun.
Monday and beyond... Another strong cold front is progged to cross
the forecast area early Monday. Best chance of precip lies in
central Neb where some daytime heating and clearing can occur before
the fropa. Regardless, remnant moisture coupled with the approaching
upper trough should allow for some showers to the west as well.
Additional precip chances exist Tuesday with the trough axis
bisecting the area and a new surface trough lines up. Waves of
cooler air aloft riding the northwest flow will result in seasonable
temps next week (highs 60s and 70s).
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 611 PM CDT Thu Sep 20 2018
Skies have begun to clear out across the panhandle and northwest
Sandhills erly this evening. MVFR ceilings at KVTN near ovc020
should lift by 01z, with VFR conditions for the remainder of the
TAF period. At KLBF, Showers in the vicinity should exit the area
by 00z, with clearing skies and VFR conditons as well. Northwest
winds across western Nebraska up to 12 kts this evening, will
become north on Friday, and diminish during the afternoon.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Snively
LONG TERM...Snively
AVIATION...Roberg
Area Forecast Discussion
National Weather Service Shreveport LA
931 PM CDT Thu Sep 20 2018
.UPDATE...
Did not make much in the way of changes to overnight temperatures
but weakening convection to our west has enough coverage to keep
chance pops riding through midnight and then kept slight chance
pops mainly near and to the northwest of the I-30 Corridor after
midnight through sunrise. The latest 00z NAM output is in good
agreement with the latest HRRR output such that convection should
really develop quickly across our northwest zones near or just
after sunrise and this is due to strong PVA signal ahead of the
upper level trough which should still be anchored across the OK/TX
Pnhdl region by noon on Friday. Heating will play the necessary
factor across our central and eastern zones on Friday to help
generate scattered convection but the main story will be with the
trough to our north and west over the next 24 to 36 hours at least
and where will the heaviest rainfall training set up. At this
time, it appears this will occur just to our northwest but will
await a full suite of models to determine if a Flash Flood Watch
will become necessary for a portion of our northwest zones Friday
into Friday Night.
Update out shortly...13
&&
.PREV DISCUSSION... /issued 537 PM CDT Thu Sep 20 2018/
AVIATION...
Have included VCTS through 03z for the TYR/GGG/LFK terminals and
may need to include it at the TXK terminal as well based on
current radar trends. Otherwise, VFR conditions should prevail
through much of, if not all of the overnight hours. Cross sections
support enough boundary layer moisture return in the 11-16z
timeframe on Friday for MVFR ceilings but they should lift by late
morning. Have reintroduced VCTS at all terminals during the
afternoon on Friday with the exception of the ELD/MLU terminals.
Look for southeast winds less than 10kts overnight and S to SE
winds at or near 10kts during the daytime hours on Friday outside
of afternoon convection.
13
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 74 89 74 85 / 10 50 40 70
MLU 73 92 73 90 / 10 30 30 60
DEQ 71 86 71 78 / 20 60 80 80
TXK 73 88 72 79 / 10 50 70 70
ELD 73 90 72 83 / 10 50 50 70
TYR 74 88 73 81 / 40 50 60 80
GGG 74 89 73 83 / 30 50 50 70
LFK 74 88 74 86 / 20 50 40 70
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
13/13