Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/19/17
Area Forecast Discussion
National Weather Service Columbia SC
1041 PM EST Sat Feb 18 2017
.SYNOPSIS...
An upper-level disturbance will cross the region tonight then
move off the coast Sunday morning. High pressure and dry weather
will return for Sunday through Tuesday night with unsettled
weather for Wednesday onward. High temperatures are forecast to
be well above normal into next week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Showers moving across the north Midlands associated with short
wave trough moving through the area. Additional weak short
waves rotating around upper low may trigger more showers during
the evening although deeper moisture lifting northeast of the
area. High resolution NMM/ARW appear overdone based on lack of
showers upstream in Georgia.
The HRRR suggests diminished shower coverage for central SC/CSRA.
The shower chance should further diminish overnight because of
shallow moisture in the wake of a lead mid-level shortwave
trough. The shallow low- level moisture plus nocturnal cooling
may lead to stratus and fog late. Stratus may be favored because
of boundary layer wind. The temperature guidance was close.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
Upper level disturbance will move offshore around sunrise with
an upper level ridge quickly building into the southeastern
states. Cloudiness will rapidly diminish during the morning
hours with mostly clear skies from Sunday afternoon through
Monday as high pressure dominate the region. Expect clouds to
slowly increase Monday and Monday night as the high pressure
begins tracking toward the coast with northeast to easterly
winds over the area. Temperatures will be in the middle to upper
70s with lows in the middle to upper 40s.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
Over the past several runs models have come into good agreement
for the middle through the end of the week. High pressure will
move away from the region Tuesday as the remains of a frontal
boundary move toward the area from the northwest while an area
of low pressure develops along the TX coast. The front along
with low chances of rain will move through the area Wednesday
as the area of low pressure moves into the central Gulf of
Mexico and becomes less organized. This will leave the forecast
area under easterly flow for Thursday and Friday as deep low
pressure tracks from the Central Plains into the Western Great
Lakes and pushes a cold front to the Gulf Coast. Models have
significant differences in timing of the cold front into the
Midlands and CSRA...however they agree a cold front will cross
the area Friday night or Saturday. Temperatures through the long
term will be above normal.
&&
.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
Latest radar still indicating a few light showers over portions
of the area late this evening. Precipitation is very limited in
areal coverage and intensity and should dissipate over the next
couple of hours so will not mention at any of the TAF sites.
Latest CAE VWP indicating a 20 kt LLJ around 2kft and the latest
BUFKIT guidance showing that LLJ will persist for much of the
overnight period. Latest HRRR guidance seems to be more
optimistic with CIGS and VSBYS during the overnight period, but
given plentiful low-level moisture, will still keep some
restrictions before sunrise, but confidence is low. VFR
conditions will return after 14Z Sunday.
EXTENDED AVIATION OUTLOOK....Moisture associated with an
onshore flow may help bring widespread MVFR or IFR conditions
Tuesday through Wednesday.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Dodge City KS
549 PM CST Sat Feb 18 2017
...Updated Aviation Section...
.SHORT TERM...(This evening through Sunday)
Issued at 231 PM CST Sat Feb 18 2017
Temperatures late this afternoon look highly probably to fall into a
narrow range of upper 60s under the increasing clouds region of
the west, to lower 70s near the surface front in central KS. The
latest bias corrected HRRR was trending this way. Beyond that, the
forecast problem becomes the increasing moisture, low clouds and
fog that is probably going to develop between 9 and 12 z.
Dewpoints will increase into the 40s on light south winds, driving
dew point depression to 2 or 3 degrees at most in the far west.
Dense fog and stratiform cloud bases a should fall below 400 ft
across central Kansas by the middle of the night, and there may be
portions of the area where dense fog becomes widespread enough to
impact travel at least locally by early morning Sunday.
.LONG TERM...(Sunday night through Saturday)
Issued at 231 PM CST Sat Feb 18 2017
The low clouds and fog may persist for several hours early Sunday
morning before a significant improvement is noticed. The moisture
advection will continue and showers may develop by the afternoon
hours from south to north. The consensus of the convective allowing
models suggest late evening thunderstorms over eastern Colorado that
have a low probability of affecting any of our counties, and a
larger area of showers and embedded convection across central
Oklahoma into south central Kansas through midnight with mainly a
lightning risk.
A relative dry period then follows through at least about Late
Thursday through Friday when the ECMWF and the GFS both show the
next vigourous shortwave move though the area with a frontal passage
to follow. This should be a period of higher than average surface winds
across the entire region, possibly with windy conditions through
the overnight Thursday - important with all the ice storm debris
burning continuing. Friday into next weekend may be a return to
the climatological normal for this time of year, but the colder
air does not penetrate very far equatorward for sustained winter
like temps.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 543 PM CST Sat Feb 18 2017
Aviation conditions will deteriorate during the overnight hours,
particularly in the 09-15z time frame, as low level moisture moves
in to the area from the south as a storm system approaches from
the Southern Rockies. There is a fair degree of uncertainty as to
the extent and duration of LIFR conditions in fog and very low
stratus, but the official TAF will call for 1/2 mile visibility in
fog for at least a few hours around sunrise at GCK, DDC, and HYS.
Thereafter, conditions will slowly improve through IFR and MVFR
during the mid to late morning hours. Winds will be out of the
south, increasing during the afternoon hours to 15 to 20 knots
sustained, especially GCK and DDC.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 45 65 46 68 / 0 30 30 0
GCK 42 66 41 67 / 0 10 20 0
EHA 41 67 39 66 / 0 10 10 0
LBL 43 70 40 69 / 0 20 20 0
HYS 45 65 48 67 / 0 20 30 0
P28 48 63 52 72 / 10 50 60 10
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Russell
LONG TERM...Russell
AVIATION...Umscheid
Area Forecast Discussion
National Weather Service Wilmington NC
945 PM EST Sat Feb 18 2017
.SYNOPSIS...
An upper level disturbance may bring a few light showers
tonight. Warmer temperatures this weekend should last through
next week. Dry weather during the first part of next week may be
interrupted as low pressure passes to the south spreading some
clouds and possible showers into the Carolinas late next week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 930 PM Saturday...Precip on radar has almost completely
dissipated over the past few hours. Where light rain was
reported in ASOS/AWOS observations, only trace amounts fell.
I`ll keep a small region of 20 PoPs in the forecast for late
tonight with the approach of a vort max, now moving eastward
across Georgia where some patchy light rain is breaking out near
Atlanta. I`ve also added a little patchy fog across the Pee Dee
region where light winds, clearing skies, and just enough
boundary layer moisture may coexist just before sunrise Sunday.
Discussion from 630 PM follows...
Upper level low pressure located over southern Kentucky will
weaken as it moves eastward tonight, ending up over Virginia by
daybreak Sunday. Moving downward through the atmosphere...the
low is still discernible at 700 mb but by the time you get to
850 mb there is very little perturbation left in the wind field.
Low-level baroclinicity is naturally maximized near the Gulf
Stream this time of year, and this is where surface low pressure
should develop late tonight.
Satellite and radar show a zone of clouds and light rain
extending across the central Carolinas. ASOS cloud bases are
generally 10kft where precip is falling. With surface dewpoints
in the 30s and 40s I can`t imagine precip rates are going to
become heavy enough for measurable amounts to occur. I`ve
removed PoPs for this evening, anticipating only non-measurable
sprinkles to fall across the Pee Dee region into Lumberton over
the next few hours.
What could turn out to be a slightly better potential for precip
will develop late tonight as a 500 mb vort max currently over
Mississippi moves east to the Carolina coast. Models show
steepening lapse rates aloft as this feature (and the broader
upper low) approach from the west. If low-level winds remain
backed enough to maintain a ribbon of moisture along the coast,
elevated convection could develop from bases around 6000-7000
feet AGL with tops in the 15000-20000 ft AGL range. I`ll keep a
20 PoP in the 08-11z timeframe along the coast for this
potential and will continue to monitor model trends to judge how
likely it is we need to keep this in the forecast.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
As of 300 PM Saturday...Time-height cross sections indicate rapid
drying early Sunday as winds throughout the column shift quickly to
the northwest. The mid-levels will remain quite dry through the
period as a mid/upper ridge transitions from the central plains
states on Sunday to the eastern seaboard by late Monday night.
Mainly clear skies Sunday will start to become filtered by cirrus on
Monday and through Monday night, but the period will remain precip-
free.
There will be some cool advection in the 1000-850 mb layer Sunday
behind the front as low pressure strengthens offshore, and this
should result in max temps a few degrees cooler than Saturday. As
heights rise on Monday, temperatures should bounce a few degrees,
though light onshore flow should keep them in check along the
coast.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 300 PM Saturday...Medium range guidance continues to point to
a very warm and mostly dry scenario for the eastern Carolinas
through the period. Overall the mid level pattern is one of west
to east with the exception of a closed mid level system
trudging very far south through the Gulf of Mexico and out in
the Caribbean. This system will have little to no affect on the
region. Regarding surface features, high pressure to the north
will be the dominant player with a weak coastal trough
developing Wednesday and hanging around through Friday. This
prevents the forecast from being totally dry with low chance to
slight chance pops for these days. A more significant system
approaches from the west next weekend. For temperatures its
mostly highs in the 70s and lows in the 50s beyond a slightly
cooler Tuesday.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 00Z...An upper vort will try to rotate through the area,
however the HRRR model keeps dissipating the precip as it tries to
enter the CWA. Will keep the current VCSH in place with only a
sprinkle possible. A 5k ceiling is a bit pessimistic, but we should
see ceilings lower after midnight. Some MVFR fog is possible after
08Z, confidence mod/low. Sunday, northwest flow on the backside of
the surface low pressure, scattered skies.
EXTENDED OUTLOOK...VFR conditions are expected. Chance of
showers Wednesday and Thursday.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 930 PM Saturday...No significant changes are needed to
the forecast at this time. Discussion from 630 PM follows...
The 12z Canadian appears to be the winner with wind speeds this
afternoon and this evening. Most of the other model guidance
was several knots too weak versus observations from buoys,
piers, and coastal airports. As weak low pressure develops off
the coast tonight southwesterly winds should veer west, then
northwesterly late. Seas are generally around 2 feet, although
there is some potential for an area of 3 foot seas to develop
south of Cape Fear this evening due to the 15 knot southwest
winds that have been blowing across Long Bay for the past
several hours.
SHORT TERM/SUNDAY THROUGH MONDAY NIGHT/...
As of 300 PM Saturday...Offshore flow Sunday will veer to the
northeast Monday as a large area of high pressure extends southward
across the Mid-Atlantic. Although low pressure will develop well off
the SC coast Sunday, it will progress eastward rather quickly and
the gradient winds across the coastal waters are expected to remain
15 knots or less through the period.
LONG TERM /TUESDAY THROUGH THURSDAY/...
As of 300 PM Saturday...Expect northeast winds Tuesday on the order of
10-15 knots. By Wednesday the gradient weakens considerably with
more of an east to southeast flow developing. The sea breeze will
become more of a factor both Wednesday and Thursday. The weak
gradient will only produce wind speeds of ten knots or less.
Significant seas quite unimpressive through the period as would be
expected with the light wind fields with 2-4 feet Tuesday followed
by 1-3 feet Wednesday and Thursday.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...SHK/TRA
NEAR TERM...TRA
SHORT TERM...CRM
LONG TERM...SHK
AVIATION...DL
Area Forecast Discussion
National Weather Service Memphis TN
901 PM CST Sat Feb 18 2017
.DISCUSSION...
Skies are cloudy over most of West Tennessee and portions of
northeast Arkansas and the Missouri bootheel with mostly clear
skies elsewhere across the forecast area. Temperatures this
evening range from the upper 40s to mid 50s. The light rain which
was mainly over portions of northwest Tennessee appears to have
ended. Some dense fog has formed over portions of the Missouri
bootheel and extreme northeast Arkansas. If dense fog becomes more
widespread a Dense Fog Advisory may be needed. Will update
forecast to remove evening wording.
ARS
&&
.PREV DISCUSSION... /issued 620 PM CST Sat Feb 18 2017/
DISCUSSION...
Radar continues to show some light rain over extreme northern
sections of the forecast area. HRRR model shows that this rain
should end in the next couple of hours. Updated forecast to show
low pops in this area this evening. Also expanded mention of
patchy fog to start after midnight and included entire forecast
area.
ARS
PREV DISCUSSION... /issued 302 PM CST Sat Feb 18 2017/
Upper level low center pivoting in Western Kentucky this
hour...with very little in rainfall to its south. Only rain likely
hitting the ground is across northern Dunklin County. Clouds
however were covering most of the Midsouth with light south winds
and temperatures ranging from the mid 50s to upper 60s.
For tonight through Tuesday...clouds will gradually clear
tonight...mainly after midnight as the upper low pulls east. Mild
lows expected. Amplifying ridge ahead of the next upper level low
in the Baja will slide over the Midsouth tomorrow...providing for
a very nice winter day. Temperatures will climb into the 70s area
wide with light southeast winds. WAA will continue Sunday night as
high level moisture streams northeast out of Texas. Bumped up
Monday morning lows a degree or two to reflect that. Models
continue to hold back precipitation with the Baja low until Monday
night and Tuesday...and even then the GFS and ECMWF keep lesser
QPF across the north as the northern stream shortwave advances
faster to the east. Only significant changes to Monday`s forecast
was an increase in afternoon highs as 850mb temperatures warm to
16C. Made changes Tuesday night...as lingering moisture in the
boundary layer coupled with weak low level flow could easily lead
to patchy fog and drizzle...especially in the east.
Wednesday through Saturday...mild and dry air will remain in the
wake of Tuesday`s system for Wednesday...as eyes turn to the
Central Rockies for the next storm. This shortwave will deepen to
a new closed 500mb low in the Plains on Thursday...triggering a
deepening surface low in Kansas. This feature will quickly
occlude by the time it reaches the Lower Missouri Valley late
Thursday night. The Midsouth will be warm and capped for Thursday
as south winds increase. Raised highs a couple of degrees and
introduced a slight chance for a WAA sprinkle under the cap. A
cold front with the occluded low will cross the Midsouth
Friday...but the strong cap coupled with nearly no height falls as
the upper feature lifts out will provide for limited convection.
Though an isolated strong storm could form...confidence and
coverage is so low from the models to make any mention outside of
this AFD. Strong winds out ahead of the front though may lead to
a wind advisory in the Delta. Post-frontal Saturday looks to be
dry and seasonal.
JAB
&&
.AVIATION...00z TAFs
Variable skies are expected over the next 24 hours. Temporary
clearing this evening will be short lived as low clouds redevelop
tonight. Guidance is in poor agreement with respect to the
coverage of clouds as well as cigs. With light winds...dewpoints
in the upper 40s to low 50s feel like it is a pretty good bet to
side with the lower cigs and widespread coverage. Will bring cigs
down to MVFR levels before midnight then IFR after midnight with
TEMPO LIFR cigs around sunrise. Will keep vis MVFR at MKL and MEM
with IFR vis at JBR and TUP. By midday cigs and vis should improve
to VFR. Winds light from the South.
30
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Melbourne FL
830 PM EST Sat Feb 18 2017
.UPDATE...
Tonight...Earlier band of convection moved into drier air that was
in place across central Florida and weakened rapidly, but acted to
moisten the air mass. Trough aloft will move slowly eastward across
the deep south with large scale ascent staying to our north.
However, a band of higher moisture will persist across the area for
most of the night. MOS has likely POPs but will keep current chance
numbers since the HRRR has been showing isolated/scattered showers
lingering through the night. Think that the chance for thunder will
be over the coastal waters as the air mass over land will be too
stable. MOS has been showing low ceilings developing after midnight
and also shows low visibility across northern sections late. Have
leaned more to low stratus, but will keep mention of patchy fog too.
Adjustments to the previous forecast are minor at this time.
&&
.AVIATION...Considerable cloudiness will persist for most of the
night, but MOS has been showing low stratus/fog developing after
midnight, especially KISM-KMCO-KTIX northward. Have gone with IFR
stratus rather than the LIFR shown by MOS. With some rain wetted
areas, would also expect spotty visibility restrictions. The low
clouds may persist until late Sunday morning.
&&
.MARINE...
Tonight-Sunday...High pressure ridge over the Atlantic was providing
a southerly wind flow. Marginal looking exercise caution conditions
are possible offshore. The ridge will retreat seaward as a weak cold
front sags into the waters on Sunday. Northwest-north winds behind
the front look about 10-15 knots. Seas should be 2-3 feet near
shore and 3-5 feet offshore. Little change to previous forecast.
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Forecasts...Lascody
Impact Weather/Radar...Blottman
Area Forecast Discussion
National Weather Service Morristown TN
909 PM EST Sat Feb 18 2017
.DISCUSSION...Current forecast basically on track with a slow
eastward shift of the Ohio Valley upper level trough. WRF AND HRRR
paralleling mid evening satellite and radar imagery with deeper
moisture and lift building east out of the Mid South toward the
forecast area later tonight. Precipitation will be light with this
feature as it builds into the Southern Appalachians and mainly on
the Plateau with some orographic enhancement. Will adjust pop grid
to match the overnight event. Temperature forecast looks decent.
Patchy fog development on the mark as well.
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...None.
VA...None.
&&
$$
Area Forecast Discussion
National Weather Service Charleston WV
1019 PM EST Sat Feb 18 2017
.SYNOPSIS...
Weak system overnight with scattered showers. Unseasonably warm
through the work week with another weak system Tuesday into
Wednesday.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 1010 PM Saturday...
Band of showers setting up west to east from the Tri State area
along I-64. No significant changes to the previous forecast, as
the trend is on track.
As of 605 PM Saturday...
Reworked the POPs tonight based on the latest runs of the RAP
and HRRR, while still using the NAM component in a blend. Upper
level deformation zone will keep the northern extent of the
showers from going too far north into Perry and Morgan counties.
As of 1250 PM Saturday...
Models show a weak system with an upper level trough moving across
the area overnight, producing some showers. Dynamics are weak enough
that models are a bit varied on the placement of showers at any
particular time, so will generally stay with just high chance pops
in the most likely areas. With clouds remaining through the night,
will keep low temperatures are the warmer side of MOS guidance.
A stratus deck behind the system should lift into a cumulus deck on
Sunday as high pressure builds in, allowing for some sunshine,
especially in the afternoon.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 300 PM Saturday...
Anomalously warm pattern continues next week. A weak system
looks to cross Tuesday night with scattered showers. I hedged
toward the slower NAM given the stout upper ridge that will be
in place ahead of this system. Still feel many southern areas
hit or surpass 70 degrees Monday and possibly Tuesday, despite
the abundance of high clouds.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 300 PM Saturday...
The very warm pattern continues through the week. A weak system
passes Wednesday. This prolonged stretch of warmth will allow
for an early start to budding and blooming of some varieties
trees/vegetation. They looks to be a brief respite from the
warmth over the weekend as a colder air works in.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
As of 605 PM Saturday...
Upper level system will continue to overspread scattered showers
across the middle Ohio Valley and central Appalachians through
tonight. Ceilings to lower to MVFR with brief MVFR in showers.
BKW would be most prone to going down to IFR ceilings, and have
this in the TAF from 07Z to 12Z. This takes the overall
confidence down somewhat, however. Southern terminals will
settle in the 1-2kft range later tonight.
Rain ends with cumulus field developing Sunday.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z MONDAY...
FORECAST CONFIDENCE: High this afternoon, then medium.
ALTERNATE SCENARIOS: Timing of lower clouds could vary. Brief
IFR in showers is possible.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE SUN 02/19/17
UTC 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14
EST 1HRLY 22 23 00 01 02 03 04 05 06 07 08 09
CRW CONSISTENCY H H M H L H H H H H H M
HTS CONSISTENCY H M M M H H H H H H H M
BKW CONSISTENCY H H H M M H H L M H L L
EKN CONSISTENCY M M M L L L L L L L L L
PKB CONSISTENCY M M M M L H M M L L L L
CKB CONSISTENCY H H H H H H H H H L H M
AFTER 00Z MONDAY...
No widespread IFR expected.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...None.
OH...None.
KY...None.
VA...None.
&&
$$
SYNOPSIS...RPY/30
NEAR TERM...RPY/26
SHORT TERM...30
LONG TERM...30
AVIATION...26
Area Forecast Discussion
National Weather Service Topeka KS
523 PM CST Sat Feb 18 2017
...AVIATION UPDATE...
.SHORT TERM...(This evening through Sunday)
Issued at 246 PM CST Sat Feb 18 2017
Weak return flow has been established across the area today as an
upper level system tracks over the southwest US. The main forecast
issue will be the potential for stratus and fog. This morning the
stratus and fog was located in northern OK, but has since mixed out
into southeastern OK. Later tonight the approaching upper level
system will allow the low level jet to increase, but focus over the
high plains. Regardless the low level winds will increase allowing
the moisture to spread northward across the entire area. There may
be the potential for fog before and after the stratus arrives.
Surface wind speeds will be relatively light and maybe some high
clouds are possible. Stratus is not forecasted to arrive until after
midnight, which could allow some time for radiational cooling. The
current dew points along and south of interstate 70 are in the lower
to mid 40s. Temperatures are expected to reach the lower to mid 40s
by sunrise, which supports the possibility of restricted visibility.
Ahead of the stratus it would most likely be more ground fog, but
once the stratus arrives the fog may dissipate or improve. At a few
locations it may mix down from the cloud base due to the advection
especially at higher elevations. The dew points are not expected to
increase much from the current state, and the boundary layer should
not fully decouple for widespread dense fog to be a big concern.
Tomorrow the models struggle with mixing out the stratus like what
is occurring is OK today. Some models are also indicating an
increase in the depth of moisture ahead of the Pacific system, which
could inhibit mixing. Although the consensus is for highs tomorrow
to reach the upper 60s to lower 70s. If clouds were to hang around
most of the day temperatures may only reach the lower 60s.
.LONG TERM...(Sunday night through Saturday)
Issued at 246 PM CST Sat Feb 18 2017
The mid/long term forecast remains largely unchanged from previous
shifts/days as model consistency in the mid-term details remains
relatively strong, and consistency in the long-term big picture is
also quite good. The main points continue to be that much warmer
than normal conditions will persist into Thursday, with an influx of
colder air likely after that time. Two storm systems will impact the
region in the coming week, the first late Sunday into Monday, and
the second late Thursday into Friday...with at least some indication
of a continued stormy pattern beyond the extent of this forecast.
Regarding the warmer-than-normal conditions, the early week storm
system has very little cold advection associated with it, and sunny
skies in its wake will keep temperatures plenty warm. Beyond that
point, upper ridging quickly takes over with neutral to warm
advection through the week. Based on recent forecast/model
verification, have gone markedly warmer with Min/Max temps from
Monday night through Wednesday, leaning heavily on the warmer side
of MOS guidance for highs and on the warmer side of operational
model guidance for lows. Thursday could be warmer as well, but will
depend more on the eventual storm track and warm sector location by
that time.
Precip chances with the first storm system Sunday night into Monday
remain fairly high especially in eastern KS, but it still appears
that not everyone will receive rain. The moisture influx into the
region is quite impressive but the mid/upper level forcing during
this period continues to appear less impressive overhead. There will
be periods of weak instability, and this along with enhanced lift in
embedded short wave troughs may bring the best chance for precip
early Monday morning although scattered showers are possible both
before and after that period. The NAM is a distinct outlier and
seems to over-moisten the boundary layer ahead of a slower upper
trough, resulting in a scenario suggestive of scattered convection
Monday afternoon...but this again is an outlier and is probably
overdone and unlikely to occur.
The second storm system late Thursday into Friday is forecast by all
operational guidance to be much more dynamically impressive locally,
but with a fair amount of uncertainty in how quickly the system will
evolve among various ensemble members. What we continue to see is a
very strong jet streak entering the central Plains by Thursday with
rapid positive feedback cycle of cyclogenesis and deepening of the
upper low. While a handful of ensemble members keep this as an open
wave, it seems equally or perhaps more likely that the system will
close off and take on a negative tilt. This will probably depend on
the speed of the trough in comparison to the translation of the jet
streak...which seems to have at least loose ties to the evolution of
a wave over the northeast Great Lakes region by mid week. As always,
it`s a complex evaluation. Current forecast focuses on the
likelihood for a strengthening system to track over KS/NE during the
period with distinct warm and cold sectors. This would suggest
potential for widespread rain and even thunderstorms within the warm
sector and widespread snow...possibly heavy and accompanied by
wind...on the cold side. Currently, snow chances increase sharply
with northwestward extent, and several model solutions suggest
snowfall in portions of north central KS...but with the qualifier
that the storm track remains quite uncertain.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday)
Issued at 523 PM CST Sat Feb 18 2017
Models continue to show low level moisture advection increasing
overnight. As a result, Some fog and stratus is forecast to impact
the terminals by the early morning hours Sunday. The forecast is
based off of the model consensus and so timing of the onset of BR
and lower CIGS may need adjustment by an hour or two once the
restricted conditions become more apparent. The RAP and NAM are
showing 925MB RH remaining high well into the afternoon implying
the stratus may be slow to scatter out. Because of this, have held
onto MVFR CIGS through the afternoon.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Sanders
LONG TERM...Barjenbruch
AVIATION...Wolters
Area Forecast Discussion
National Weather Service Tulsa OK
924 PM CST Sat Feb 18 2017
.DISCUSSION...
Skies have cleared and temperatures have dropped to near the
forecast lows in many places, so will lower overnight lows a
couple degrees. Still expect some low clouds and patchy fog to
form later tonight and early Sunday morning, but the eastern
extent of the clouds/fog is in doubt. The latest experimental HRRR
keeps far eastern Oklahoma and western Arkansas relatively cloud
free through Sunday morning. The only change made at this time to
the cloud forecast is lowering sky cover the next few hours based
on current conditions.
Update on the way.
&&
.TSA WATCHES/WARNINGS/ADVISORIES...
OK...None.
AR...None.
&&
$$
SHORT TERM...07
LONG TERM....05
PLATE
Area Forecast Discussion
National Weather Service Tucson AZ
850 PM MST Sat Feb 18 2017
.SYNOPSIS...A good chance of valley rain and mountain snow continues
through Sunday afternoon, then showers will end Sunday night. Dry
conditions will prevail across much of the area Monday into next
Saturday. However, a few snow showers may occur across the White
Mountains Wednesday night and Thursday. Expect much warmer
temperatures by mid week before cooler temperatures return late in
the upcoming week.
&&
.DISCUSSION...IR satellite imagery and surface observations depict
cloudy skies across much of southeast Arizona at this time, although
some breaks in the overcast were noted. KEMX WSR-88D detected 30-35
dBZ echoes limited to portions of Pinal County as well as southern
Graham/northeast Cochise Counties. Thus, the bulk of heavier
precipitation that occurred earlier today has ended for the time
being. Surface winds valid 8 PM MST have also diminished to less
than 15 mph.
The upper low pressure system responsible for the precipitation as
per Water Vapor/IR satellite imagery and the 19/00Z upper air plots
was centered near Yuma, AZ. This low pressure system is progged to
move northeastward into central Arizona by daybreak Sunday, then
fill while moving northeastward into southern Colorado by Sunday
evening.
The 19/01Z and 19/02Z HRRR solutions and to some extent the 19/00Z
NAM were quite similar with depicting a downward trend in precip
coverage throughout much of the rest of tonight. The coverage of
precip is then depicted to increase Sunday morning. Based on
satellite/radar trends, these solutions seem to be reasonable.
However, am inclined to make only very minimal adjustments to the
inherited gridded data PoP values. Further, the NAM12 and a quick
inspection of the 19/00Z GFS suggests that an additional 6 or so
inches of snow should occur Sunday across the Catalina Mountains and
Mount Graham, and up to an additional 12 inches across the White
Mountains. Snow levels should remain around 6000-6500 feet which
coincides with the present levels. Markedly less wind will occur
into Sunday morning, then some gusts from the southwest to northwest
will prevail Sunday afternoon. However, speeds will be well below
Wind Advisory criteria.
&&
.AVIATION...Valid through 20/06Z.
Scattered to numerous valley -SHRA and mountain SHSN will occur into
Sunday afternoon, then precipitation coverage decreases markedly
Sunday evening. Otherwise, cloud decks will generally be 4k-8k ft
AGL, but occasional MVFR ceilings/visibilities will also prevail.
Surface wind mainly sly 5-15 kts with gusts to 20 kts into Sunday
morning, then surface wind swly to nwly 10-18 kts with gusts to 25
kts Sunday afternoon. Aviation discussion not updated for TAF
amendments.
&&
.FIRE WEATHER...A weakening low pressure system will bring a good
chance of valley rain and mountain snow through Sunday. A slight
chance of showers exists Sunday night, then dry conditions will
prevail across much of the area Monday into next Saturday. The
exception may be a few snow showers across the White Mountains
Wednesday night and Thursday. Some gusty west or northwest winds
should occur Sunday and Thursday. Otherwise, 20-foot winds will
mainly be less than 15 mph.
&&
.PREV DISCUSSION /221 PM MST/...By Sunday morning model consensus
has the upper low near Casa Grande and slowly shifting to the east
as it opens up. This will leave our area in a slightly unstable
regime with breaks of sunshine and scattered showers, more numerous
over the mountains and with lower snow levels should see snow
showers down to around 6,000 ft with accumulations mostly limited to
above 7,000 ft. Current forecast of 10-16 inches for storm totals
today though Sunday evening above 7,500 ft may be a touch on the
high side but in the ballpark so won`t tweak significantly at this
time.
If current timing holds, the trough axis will be moving east of
the New Mexico border Sunday afternoon, so would expect a general
decrease in the showers in the afternoon from west to east with a
rapid decrease after sunset with the loss of heating and a short
wave ridge quickly building in from the west. With some clouds,
scattered showers and cool air mass in place high temperatures
should peak a few degrees cooler than average for February 19.
As mentioned, drying will kick in Sunday night with dry weather
expected through the coming week with the possible exception of a
stray shower northern areas as a system passes by to the north
Wednesday night. It will warm quickly Monday through Wednesday
with high temps around or a bit above 80 from Tucson westward
Tuesday and Wednesday. Temps will be forced back down to more
normal levels Thursday and Friday thanks to the previously
mentioned system passing by Wednesday night. There is some
suggestion of another system passing by or through the area late
next weekend. Time will tell how that plays out.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 5 PM MST Sunday for AZZ510-511-
513-514 above 7500 feet.
Winter Weather Advisory until 5 PM MST Sunday for AZZ512
above 7500 feet.
&&
$$
Francis
PREV DISCUSSION...Cerniglia
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