Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/19/18
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
822 PM MDT Sat Aug 18 2018
.UPDATE...
Quick update to decrease 1st period PoPs based on latest radar trends
and HRRR output. Severe threat has diminished, although a few
stronger storms are still possible through the evening hours across
the east central plains.
&&
.PREV DISCUSSION...529 PM MDT Sat Aug 18 2018...
.AVIATION...
00Z TAF CYCLE
Round of strong to severe storms moving southeast across the state
may impact KSAF and KLVS early this evening and will likely impact
KTCC, where strong to damaging winds and hail are possible between
0130-0300Z. MVFR conditions will accompany storms at KTCC, with
short-lived IFR conditions possible. KABQ and KAEG look to be spared
from this round. Otherwise, VFR conditions prevail and are forecast
to persist. Northwest breezes with gusts will pick- up again Sunday
afternoon at KGUP and KFMN.
11
&&
.PREV DISCUSSION...256 AM MDT Sat Aug 18 2018...
.SYNOPSIS...
An atypical upper level trough is expected to drag across
northeastern New Mexico this afternoon and into the evening,
providing lift and unstable conditions for scattered to numerous
thunderstorms, some of which will turn strong to severe. Showers and
thunderstorms will also form along the higher terrain of central and
western New Mexico early this afternoon, but will be shunted eastward
as the afternoon wears on. On Sunday, storms will be few in number
during the daytime due to drier air that will have worked in behind
the previously mentioned disturbance aloft, but a cold front will
spill into the eastern plains of New Mexico late Sunday and Sunday
night with a few storms possible. Gusty winds will accompany the
front, including parts of the Rio Grande valley as the front surges
westward Sunday night. Thunderstorm chances will be fairly low early
next week as moisture struggles to slowly return to the area.
&&
.DISCUSSION...
Upper low over northern ID will drop an unseasonably strong short
wave trough into eastern CO and northeastern NM late today. Southerly
surface flow over the plains of NM will be topped with increasing
north-westerlies aloft, a veering wind profile that will give plenty
of directional and speed shear for strong to severe storms today
and this evening. Abundant instability will also be present with NWP
advertising scattered areas of 2,000+ J/kg of CAPE and lifted indices
of -3 to -6 C over much of northeastern NM as well as some east
central parts of the state. Have included likely POPs for some of
these areas with mention of large hail and damaging winds. The other
notable feature with the trough will be the pronounced dry slot
working in immediately behind the trough axis. This sharp moisture
gradient will likely act as a trigger for storms, but the impending
drier air will also lead to a quick suppression of storms once the
wave aloft passes through. Quick storm motions to the southeast
should limit the flash flooding threat, but PWATs ahead of the trough
axis will be quite healthy.
On Sunday, a cold front will be spilling southward down the plains
as the remnant lobe of energy from ID finally drops into KS. Western
NM will be void of storms as the drier air will limit convective
initiation on Sunday, but a few isolated cells will be possible along
and just east of the Sangres. While storms appear to hold off for
much of the day Sunday, a line of convection is depicted by the NAM,
dropping along the leading edge of the front in the plains into the
evening and overnight. While the NAM is the most aggressive model
with this frontally-induced line of convection, it seems reasonable
given the fast propagation speed and the favorable thermal/moisture/wind
profiles ahead of the front. A gusty east canyon wind will spill
into central zones Sunday night and early Monday morning.
On Monday, in the wake of the front temperatures will cool a couple
degrees below average in central to eastern NM. Storms will be hard
to come by as the PWATs will be fairly low with the best moisture
shunted to the southern tier of NM. Through this time the upper high
will take residence near the NM-AZ border with dewpoints remaining
healthy in eastern NM, but the deeper moisture and juicier PWATs
will likely not arrive Tuesday either as the high builds more
directly over NM. Temperatures will rebound several degrees into
Tuesday with daytime highs exceeding normal by a couple of degrees in
many locales.
Forecast models diverge into the middle and latter parts of next week
with regards to the placement and strength of the high and
consequentially the steering of deeper moisture into or around NM.
Am tending to lean toward the European solution that ever-so-slowly
takes the high slightly east of NM and gradually introduces more
moisture into the far western and northern tiers of the state.
52
&&
.FIRE WEATHER...
Another round of afternoon tstms is expected, forming over the high
terrain before moving off to the E/SE this evening. Storms east of
the central mtn chain could become severe, producing strong erratic
downburst winds and large hail. Changes begin to arrive across the
far northwest where drier air behind a trough to our N will cutoff
tstm/shower activity early today. NW winds are also expected to pick
up to 20-25 kts near the Four Corners just before sunset.
The punch of much drier air reaches the RGV during the day Sunday,
as a backdoor front protects sfc moisture east of the central mtns.
Another round of breezy NW winds can be expected Sunday afternoon
over the NW Plateau, with Haines6 and MinRHs dipping to ~10%. A few
hours of elevated to critical fire weather is possible as the NW
winds pick up over the NW Plateau late Sun afternoon. A significant
downtrend in tstm coverage is also expected Sun, although a few
isold tstms can`t be ruled out over the east-central plains.
The backdoor front wins out Sun night, surging through the gaps of
the central mtn chain reaching the continental divide Mon morning.
Moisture trends up behind backdoor front across the west through Tue
as the upper high builds back over NM allowing a better tap into
monsoon moisture over AZ. Some of the moisture works its way into
far western NM. Thunderstorm coverage also trends up through the
middle to latter half of next week.
24
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
99
Area Forecast Discussion
National Weather Service Gaylord MI
1158 PM EDT Sat Aug 18 2018
.UPDATE...
Issued at 930 PM EDT Sat Aug 18 2018
Convection got a late start (thanks to strong heating being
delayed by stratus), but our initial showers did indeed develop
shortly after 5 pm. Presently, a few showers linger from GLR to
CAD. Have tweaked to expand and extend mention of showers, but per
CAMs everything should be gone by midnight.
Stratus never exited parts of the se (Iosco Co in particular),
though it is still shrinking. Stratocu is expanding over n
central lower MI. With weak sub-850mb winds veering from ne to e
to se, clouds will expand back into much of northern lower MI,
especially overnight. Cloud cover will be most extensive south of
M-68 and east of M-37. Fog is a possibility as well, especially
outside the cloudier locales.
&&
.NEAR TERM...(Through Tonight)
Issued at 309 PM EDT Sat Aug 18 2018
...A few Showers/Thunder Possible Into the Evening...
High Impact Weather Potential: Minimal. Thunderstorms, perhaps
this afternoon. Non-severe.
Pattern Synopsis/Forecast: Mid level ridging continues to
build into the upper Midwest/western Great Lakes, along with
surface high pressure building down out of Ontario into the
northern lakes region. Pesky stratus that developed before
sunrise across northern lower MI, expanding through the morning
hours, has finally eroded back across a good portion of the
region, although there is still a good amount of cloudy skies
across NE lower MI. I expect the remaining stratus to continue
shrinking through the rest of the afternoon and this evening.
Tonight: First, still waiting to see if any convection will fire.
18Z SPC mesoanalysis reveals under 500 J/KG of MLCAPE across
northern lower Michigan, greatest south of M-55, along with some
capping aloft and CINH. We may not see much more if SPC forecasts
are correct (based on 40KM RAP data). Satellite imagery does show
show congested CU across the SW/W part of northern lower Michigan,
which has some potential. But nothing on radar yet. Plan to keep
at least chance PoPs across inland parts of northern lower
Michigan heading into the evening, primarily where the congested
CU is located and along the "edge" of eroding stratus deck. But
given the meager instability and capping, think I will keep shower
chances to less than 40 percent. Thunder may not happen at all.
Will see...
Later tonight: Low level flow will veer more southeasterly in
time. This suggests "residual" low level moisture across NE lower
MI into Lake Huron may get advected back up into northern lower
Michigan, offering the potential for more expanding stratus late
overnight and through the morning hours. Have bumped up sky cover
forecasts accordingly (and that still might not be enough) along
with patchy to areas of fog.
&&
.SHORT TERM...(Sunday through Tuesday)
Issued at 309 PM EDT Sat Aug 18 2018
Sunday through Monday
...Dry Sunday, Rain Begins Monday Night...
High Impact Weather Potential...Thunderstorms Monday night.
Pattern Synopsis/Forecast...High pressure continues over the region
will continue to keep the region dry, for the most part, on Sunday.
However, as the models have continued to do, afternoon showers and
thunderstorms look to be a possibility. With this sort of "ring of
fire" dirty ridge, not surprised that with the moisture in the lower
levels, that with a little heat and the boundary collisions on the
radar, and things take off. This looks to be the case again for
Sunday, although as we have seen during the past few days, the bulk
of the forecast area won`t see anything. Sunday night, any showers
will diminish quickly as the 700-500 mb dry layer looks to help cap
off the convection. The 500 mb ridge over the region, then begins to
break down. By 15z/Mon, showers will be possible as the cold front
and 500 mb trough approach the state, having started to cross W Lake
Superior and the Upper Mississippi River. Models have been going
with the idea, the last several runs, that the main part of the
showers and thunderstorms will start Monday evening and progress
across the state through the night, evolving into a stratiform rain
event by Tuesday morning.
Primary Forecast Concerns...So far, the timing on the models has
held steady with a few showers expected to break out in the
afternoon, but the bulk of the rain and thunder to be in the evening
and overnight as the cold front moves through the state. Dynamics
don`t look that great, as the 500 mb winds barely get to 30 knots as
the front moves into the forecast area and with the timing being
after sunset, the instability isn`t all that strong, so won`t expect
any severe threat with these.
.LONG TERM...(Tuesday night through Saturday)
Issued at 309 PM EDT Sat Aug 18 2018
...Rain Tuesday then Pretty Much Dry through Saturday...
Extended (Tuesday through Saturday)...The ECMWF shows a decent band
of rain on the north side of the sfc low in a deformation zone
producing some rain, possibly heavy at times, as the system move NE
through the state. The GFS has moved its focus south of the forecast
area and doesn`t put as much of the heavy rain into the forecast
area, unlike the ECMWF. With that agree with the WPC idea that most
of N Lower is in a marginal threat for excessive rain. Not really
expecting flooding, but probably a decent relief from the D1 drought
that has been going on. Wednesday through Friday are dry from high
pressure building back into the region. Temperatures start around
normal and continue slowly above normal into the weekend. Expecting
scattered rain on Saturday/Saturday night as another cold front
moves into the forecast area. Not sure about how well the models
will do with this, but with this Monday night/Tuesday storm, maybe
we have see a pattern change?
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1157 PM EDT Sat Aug 18 2018
Fog/stratus will return to at least ne lower MI tonight.
Some stratus still lingers in the OSC area, while higher stratocu
and some fog is found in patches in the rest of northern lower MI.
Anticipate another night of expanding low clouds, with APN again
likely to get the worst of it. This should be a little faster to
burn off on Sunday. Showers again possible in the interior Sunday
afternoon, inland from the TAF sites, so no problems there.
Light/variable winds.
&&
.MARINE...
Issued at 309 PM EDT Sat Aug 18 2018
Winds and waves remain on the lighter side. Persistent N/NE flow
may result in some better waves along the Lake Huron nearshore
areas into this evening. Winds veer southeast overnight and south
for Sunday and beyond, but remain 10 knots or less through the
period. No marine headlines anticipated.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&
$$
UPDATE...JZ
NEAR TERM...BA
SHORT TERM...JL
LONG TERM...JL
AVIATION...JZ
MARINE...BA
Area Forecast Discussion
National Weather Service Bismarck ND
908 PM CDT Sat Aug 18 2018
.UPDATE...
Issued at 908 PM CDT Sat Aug 18 2018
SPC expanded the Day One Marginal risk into most of south central
North Dakota with their 01 UTC update. The 01 UTC RAP analysis
depicts an unstable airmass across south central North Dakota and
the James River Valley with MUCAPE around 3000-4000 j/kg with
steep mid level lapse rates. The 00 UTC KBIS sounding was also
quite unstable, however, it did show some residual capping around
750 mb. While shear remains weak, convection has increased in
intensity in a similar airmass across north central South Dakota
over the past hour. With an outflow boundary inbound into south
central North Dakota and a cold front still to approach the
unstable airmass, a marginal severe threat is plausible south
central, and hinted at by the CAMs through their 00-01 UTC
iterations. Again, weak shear limits the threat ceiling and
coverage for hail and damaging wind. Locally heavy rainfall is
possible given the expected slow storm motions, and precipitable
water at 132% of normal on the 00 UTC KBIS sounding.
UPDATE Issued at 620 PM CDT Sat Aug 18 2018
Convection and smoke this evening and tonight highlight this
update.
Scattered, slow moving thunderstorms continue along a pre-
frontal trough from Hettinger and Adams counties north through
Billings, and Dunn counties ahead of a cold front approximately
from Bottineau through Minot and Watford City. Severe convection
is not expected given weak shear, as storms will continue to
exhibit a pulse nature through sunset. However, steep low and mid
level lapse rates and high LCLs do suggest a few wind gusts to 50
mph are possible, especially with collapsing storms. Locally
heavy rain is also likely given the slow storm motions. Hail is
likely to be limited to a half inch or less. After sunset and
through the overnight, rain showers and thunderstorms will
increase in coverage across southwest and south central North
Dakota to the north of the upper level low and ahead of the slow
moving cold front.
With regards to smoke, NDDOT webcams and surface observations
have shown increasing near surface smoke across western North
Dakota as winds turn to the northwest behind the trough and cold
front. Expect this to continue through the evening and overnight
as the cold front continues to move southeast per upstream trends.
Visibility of 4-6 miles is possible.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 152 PM CDT Sat Aug 18 2018
A cold front lying across southern Alberta/northeast Montana will
move southeast tonight and Sunday. The front will be the focus for
scattered showers and thunderstorms during this period.
Smoke continues to be widespread across the northern plains again
tonight, although current observations suggest its thinning more
today than yesterday. This has allowed temperatures to rise close
into the lower 90s west this afternoon, and will eventually rise
close to 95 across the west central.
Expect showers and thunderstorms to initiate along and just ahead
of the cold front late this afternoon, coincident with an h850
thermal ridge possibly suppling a bit more instability.
The severe threat will be limited as the bulk shear remains low
although cape values look sufficient.
Sunday will be much cooler behind the front. By then the chances
for showers and thunderstorms should be across teh southeast.
Severe weather is not expected.
The HRRR/RAP smoke models both indicate a break in the smoke
beginning northwest in the morning reaching the east by evening
Sunday.
.LONG TERM...(Sunday night through Saturday)
Issued at 152 PM CDT Sat Aug 18 2018
Northwest flow aloft will allow cooler surface temperatures to
remain in place through Tuesday, followed by a slow moderation
Wednesday through Friday, then cooler by Saturday. The next
significant chance of precipitation will be Thursday night and
friday with the next h500 shortwave trough and associated cold
front.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 908 PM CDT Sat Aug 18 2018
Rain showers and thunderstorms will become more numerous this
evening and through the overnight across southwest and south
central North Dakota with the approach of a cold front. Near
surface smoke reducing visibility to 4-6SM is expected behind the
front across most of western and central North Dakota tonight
into Sunday morning. Scattered rain showers and thunderstorms will
continue across the far south central and James River Valley on
Sunday.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...PA
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...PA
Area Forecast Discussion
National Weather Service Columbia SC
1111 PM EDT Sat Aug 18 2018
.SYNOPSIS...
Surface high pressure in the Atlantic will extend westward along
the Gulf Coast through Monday. North of this ridge troughing
will be in the forecast area. The pattern supports scattered to
numerous showers and thunderstorms with near normal temperatures.
&&
.NEAR TERM /UNTIL 8 AM SUNDAY MORNING/...
An upper-level trough will remain over the region with surface
high pressure extending from the western Atlantic into the Gulf
of Mexico. Convection decreasing across the Midlands and CSRA as
weak shortwave crosses the area. PWAT will remain around 2.0
inches as the air mass stabilizes overnight. Thunderstorms were
north of the Midlands with showers crossing the forecast area.
High-resolution models indicating showers ending after 07Z.
Convective debris clouds should thin during the early morning
hours. Still expect overnight lows in the low to mid 70s.
&&
.SHORT TERM /8 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
Surface ridging from the Atlantic will continue to extend westward
into the Gulf of Mexico Sunday. North of this ridge, a front
will extend from the mid-Atlantic region into the Tennessee
Valley. With the forecast area situated between these two
features, moist southwest flow will dominate and a weak lee-
side thermal trough should develop. Diurnal showers and
thunderstorms can therefore be expected, and may be enhanced by
a weak shortwave trough that is forecast to move through during
the late afternoon and evening. Upper ridging may be more
dominant Monday, yet there should still be ample moisture for
diurnal storms, especially across the northern Midlands.
Temperatures will be near normal with highs around 90 and lows
in the low 70s.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
The models indicate unsettled weather continuing through next
week. There will be surface troughing early. A cold front will
approach the area Tuesday and should stall near the coast
Wednesday. Each day will therefore see a chance of showers and
thunderstorms. Cooler and somewhat drier conditions can be
expected behind the front Thursday and Friday. However, with
the front remaining stalled along the coast through Saturday,
cannot rule out diurnal convection each afternoon and evening.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Mainly VFR conditions expected overnight. Stratus is possible
during the early morning hours.
Scattered showers crossing the TAF sites should move out of the
area by 07Z. Mid- and high-level convective debris clouds
expected to decrease overnight. Stratus possible during the
early morning hours but latest HRRR and lamp suggest no
restrictions. Convection will develop Sunday afternoon in a
continued moist and unstable atmosphere. Have indicated VCTS at
all TAF sites after 19Z.
EXTENDED AVIATION OUTLOOK...Areas of late night and early
morning stratus and fog possible each day. There will also be a
chance of mainly afternoon and evening thunderstorms.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
SYNOPSIS...99
NEAR TERM...99
SHORT TERM...99
LONG TERM...99
AVIATION...99
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
903 PM EDT Sat Aug 18 2018
.AVIATION...
Thunderstorm activity being driven by convergence along colliding
convective outflows and composite lake breeze boundaries will wane
here the next hour or two. Concern for the overnight is fog and some
guidance is extremely bullish with LIFR and VLIFR potential late
tonight/around daybreak. HRRR suggests fog may develop near Saginaw
Bay initially and spread southward overnight. Did include IFR fog
now and will monitor trends. Winds will remain light.
.DTW THRESHOLD PROBABILITIES...
* Moderate for ceiling/visibility down to 200ft and/or 1/2 mile.
* Moderate to high for ceiling 5 kft or less tonight and Sunday.
&&
.PREV DISCUSSION...
Issued at 339 PM EDT Sat Aug 18 2018
DISCUSSION...CORRECTED FOR WORDING
Biggest change to the forecasting period as discussed in the 16Z
update is the increase in PoPs from slight chance to high-end chance
as latest 12Z hi-res model guidance and internal probabilistic
guidance has trended towards higher rain and thunderstorm chances.
Low-level convergence caused by an a lake boundary coupled with weak
divergence aloft in conjunction with MLCAPE values ranging between
1000 - 1200 J/kg has and will continue to provide a source for
showers and convection. Main focus for shower and convection
initiation will take place across the Metro area up into Flint and
the southern region of the Thumb (Tuscola and Sanilac) as this is
the area where the boundary is expected to move into, coinciding
with peak CAPE values. Severe weather is not anticipated as lack of
meaningful shear and modest mid-level lapse rates hold across SE MI
through the afternoon. Storm mode will be pulse storms with isolated
to scattered coverage. Otherwise, precipitation chances will
diminish throughout the evening as diurnal heating diminishes,
cutting off the lake breeze and lowering CAPEs.
Main weather concern for the overnight period will be the
development of patchy fog, with the possibility to see areas of
locally dense fog. Surface RH will remain high overnight (>90%),
especially for areas that do see rain showers/thunderstorms this
afternoon and evening. Another plus for fog development will be
light winds in the low to mid-levels that will prevent any mixing.
However, model discrepancies still exist regarding cloud cover and
how well the mid-levels of the atmosphere dry up overnight. 17Z HRRR
and RAP runs hold light winds and high RH up to 850 mb, with dry
conditions aloft from 700 mb up, conducive for fog formation. Some
hints that a stratus deck at 700mb may advect north into the Metro
region overnight which may hamper meaningful fog development,
however, latest MOS guidance suggests potential clearing of cloud
cover across Metro region overnight. Overall, Tri-Cities up into Bad
Axe saw pockets of dense fog last night, and with calmer winds and
potential dry conditions aloft, opted for patchy fog across CWA.
Evening/overnight crew may amend forecast if dense fog looks
probable for any morning commutes.
Additional isolated to scattered rain showers will again be possible
on Sunday as low-level convergence is again the the cause of
forcing, coupled with a weak shortwave aloft that swings through SE
MI between 12Z - 00Z. Additionally, weak divergence aloft may help
precipitation development more-so for the late afternoon and evening
hours as a right entrance region of a weak jet clips SE MI.
Otherwise, with a similar air mass in place, highs will again peak
in the low to mid-80s (upper-70s along the shoreline) as conditions
remain humid.
The next chance for widespread likely showers will start to move in
across SE MI throughout Tuesday morning as an upper-level wave,
currently stationed just east of Idaho, strengthens and digs into
MO/IA, before opening and pushing northeast into Michigan. WAA ahead
of the low will transport subtropical air into SE MI ahead of
precipitation, pushing PW values between 1.80 - 2.00 inches by Tue
12Z.
Upper trough axis and strengthening surface low pressure reflection
still on track to move through central Lower Michigan during the day
Tuesday. Plenty of moisture advection ahead of the system will lead
to numerous showers and thunderstorms through the day as the height
fall axis tracks overhead. Gusty winds during the afternoon will be
possible given enhanced pressure gradient, and highs will reach the
mid to upper 70s under overcast skies. A secondary shortwave
dropping through from northwestern Ontario will sustain a lesser
chance for precipitation overnight into early Wednesday. With this
second shortwave comes a surge of cooler, drier Canadian air with
850mb temps just below 10C. This translates to surface high temps
only reaching the mid 70s on Wednesday. High pressure will build
into the area from the upper Midwest with heights aloft rebounding
through the remainder of the week. As a result, quiet weather
expected from Wednesday through next Saturday. Highs will gradually
moderate back into the low 80s by the weekend.
MARINE...
High pressure settling into the central Lakes region will aid in
slackening the wind field over Lake huron during the evening. Light
flow is expect to persist into Monday. Winds will increase from the
southeast later Monday as a stronger storm system approaches the
region. Strong northwest flow and much higher wave conditions are
expected late Tuesday into Wednesday.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....CB
DISCUSSION...AM/TF
MARINE.......Mann
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service El Paso Tx/Santa Teresa NM
224 PM MDT Sat Aug 18 2018
.SYNOPSIS...
A pair of upper level disturbances will move through the area
tonight, bringing scattered showers and thunderstorms to much of
the region. Much drier air will work into the area behind the
disturbances, nearly shutting off afternoon thunderstorm activity
on Sunday, and helping boost temperatures across the lowlands. A
few areas may see highs around 100 degrees on Sunday. A weak
backdoor cold front will drop temperatures by a few degrees on
Monday. Thunderstorm chances will increase over the higher
terrain of the Gila Region and Sacramento Mountains again
starting on Monday, but will stay focused over the higher
mountains for much of the week.
&&
.DISCUSSION...
We should see an active afternoon and evening across the area (in
terms of convection), followed by a sharp downturn in activity
for tomorrow, and a fairly anemic start to the week ahead.
Water vapor imagery shows a well-defined shortwave trough/vort
lobe moving into Grant and Sierra Counties from the NW currently,
with a more significant trough further to the north (with
significant drying in its wake). There`s a bit of wind shift at
the surface, going from light W over most of SW New Mexico to
light NW over Catron County, and this is likely the ill-defined
tail end of a surface trough that curves up into SE Colorado.
The NAM and GFS push both of these upper disturbances through the
area overnight, with significant drying behind the second trough
basically shutting us down tomorrow as PW values drop into the
0.50 to 0.75 inch range tomorrow afternoon over most of the CWA.
Modifying the 12Z EPZ sounding for a Dewpoint of 55 and a Temp of
94 (and mixing the boundary layer) yields a SBCAPE of 1200 J/Kg
and little to no CIN, and maintains a healthy 1.40" PW. However,
RAP analysis shows moderate instability (CAPEs of 800-1200 J/Kg)
mainly south of I-10, with weaker instability further north, and
much lower values over the Rio Grande Valley north of Las Cruces.
Rather flat Cu over the lowlands on satellite supports this, as
does the weakening trend of the first round of storms coming off
the Black Range. Additional storms/outflow over Catron and Socorro
Counties suggests we`ll see another round of storms in Grant and
western Sierra Counties in the next hour or two.
Most higher-res models suggest storms over Grant/Sierra Counties
will propogate south and east into the lowlands, while isolated
storms develop later this afternoon over the Sacramento Mountains,
Hudspeth County, and higher terrain in NE Chihuahua. This
convection NE to SE of El Paso should be enough to produce an
outflow boundary which may become a focus for additional
thunderstorm development later on, especially as storms and
stronger outflow from the NW push into the area, aided by the
aforementioned upper level trough. Earlier runs of the HRRR seemed
to really favor SW New Mexico (esp Luna County) for convective
coverage later today, but subsequent runs have been far less
consistent. HREF members seem to prefer South-Central NM and the
El Paso area, but with little agreement on timing.
All that being said, I like SW New Mexico this afternoon and early
evening (and more spotty storms over Otero/Hudspeth), with the
focus shifting to Dona Ana/El Paso/Southern Otero Counties this
evening. This will largely hinge on getting a decent storms going
in the next few hours to our NW, as outflow generated by these
storms will be a necessary trigger.
With the other (more significant) upper level trough approaching
later this evening, there`s a good chance at seeing storms linger
after midnight, with the most favored area sort of stretched out
E-W near and just south of New Mexico/Chihuahua border and into
West Texas... basically following the orientation of the
approaching trough.
Main weather hazard will be localized flooding with back-building
storms or slow-moving. Storm motion has been a little better than
this morning`s sounding would suggest, but storm motion is likely
to be slower closer the further SE you go (note the storms south
of Hudspeth County are barely moving).
We could see a few showers lingering in southern Hudspeth County
early in the morning tomorrow, otherwise, significant drying aloft
and at the surface will shutoff thunderstorm activity for
tomorrow. I kept in a slight chance over the Sacramento
Mountains, but that might be a stretch. With the lack of moisture,
temperatures will climb up and possibly meet or exceed the
100-degree mark over some lowland areas, including ELP.
Sunday night, a backdoor cold front will bring increasing NE to E
flow, with some noticeably gusty (but below advisory-level) winds
expected along west-facing slopes. Low level moisture will
increase markedly behind the front, but we`ll remain very dry
aloft, with PW values Monday afternoon hovering around 1.00 inch.
Stable conditions will limit thunderstorm potential over most of
the area, but scattered storms can be expected over the higher
terrain of the Gila Region and the Sacramento Mountains. With the
subtropical ridge located over the AZ/NM border, steering flow
will remain weak, and the risk of spot flooding will crop up again
in the higher terrain.
The ridge looks to drift eastwards slowly through the week, with
weak steering flow continuing. Upper and lower-level moisture will
remain anemic, and slowly warming temperatures aloft coupled with
the drier conditions will yield weak instability. What limited
thunderstorm chances we`ll have will be mainly focused in the
higher terrain. Luckily, the ridge itself isn`t terribly strong,
so while temperatures will climb above average, they should stay
in the middle to upper-90s.
Better moisture will be pulled up west of the Continental Divide
towards the middle and later parts of the week, to the benefit of
Arizona and Sonora. But as the ridge shifts into central Texas
Fri-Sat, we`ll hopefully start to see some of that moisture work
back east of the Divide.
&&
.AVIATION...Valid 19/00Z-20/00Z...
Period will start out with SCT-BKN080-100 BKN150-200 and isolated to
scattered VRB25G40KT 1-3SM TSRA BKN030-040 through 06Z. After 06Z
skies will begin to clear from N to S with just some FEW-SCT100-120
expected to develop after 18Z.
&&
.FIRE WEATHER...
After some afternoon and evening showers and thunderstorms, much
drier air will be moving in from the north for Sunday. Just a
couple isolated storms possible in the Sacs during the afternoon.
Relative humidities will be falling into the teens for most
locations Sunday afternoon as temperatures approach the 100 degree
mark again for the lowlands. A back door cold front will move
through Sunday night and bring an increase in low level moisture and
relative humidities for the upcoming week. Thunderstorm chances look
minimal except the mountains through midweek as upper ridge that`s
been persistent over the western U.S. moves eastward. As the high
moves east, a more typical monsoon pattern will setup,toward the end
of the week, but at this time it looks like the best precipitation
chances will be closer to the Arizona border.
&&
.PRELIMINARY POINT TEMPS/POPS...
El Paso 76 101 76 95 / 40 10 0 0
Sierra Blanca 72 96 70 91 / 40 20 10 0
Las Cruces 69 98 69 94 / 40 0 0 0
Alamogordo 68 97 68 93 / 40 10 0 10
Cloudcroft 52 75 48 67 / 50 10 10 50
Truth or Consequences 70 98 68 93 / 30 0 0 0
Silver City 63 92 60 89 / 40 0 0 10
Deming 68 99 69 96 / 40 0 0 0
Lordsburg 68 97 66 96 / 40 0 0 0
West El Paso Metro 75 99 75 94 / 40 10 0 0
Dell City 70 99 70 93 / 40 20 0 0
Fort Hancock 75 101 73 96 / 40 20 0 0
Loma Linda 70 96 69 89 / 50 20 0 0
Fabens 70 100 70 95 / 40 20 0 0
Santa Teresa 73 99 73 95 / 40 10 0 0
White Sands HQ 71 98 70 94 / 40 0 0 0
Jornada Range 68 98 67 95 / 40 0 0 0
Hatch 67 98 67 95 / 40 0 0 0
Columbus 71 99 71 97 / 40 10 0 0
Orogrande 73 98 73 93 / 40 10 0 0
Mayhill 59 83 54 75 / 50 10 10 40
Mescalero 58 85 54 79 / 40 10 10 50
Timberon 56 84 55 77 / 50 10 10 40
Winston 57 91 52 86 / 40 0 0 20
Hillsboro 65 96 64 92 / 40 0 0 10
Spaceport 67 97 67 92 / 40 0 0 0
Lake Roberts 51 90 49 87 / 40 0 0 30
Hurley 63 93 61 90 / 40 0 0 10
Cliff 57 96 56 94 / 30 0 0 20
Mule Creek 57 94 55 93 / 30 0 0 10
Faywood 65 94 64 90 / 40 0 0 10
Animas 69 97 67 97 / 30 0 0 0
Hachita 69 98 68 96 / 40 0 0 0
Antelope Wells 67 95 67 94 / 40 0 0 0
Cloverdale 65 92 63 91 / 40 10 0 20
&&
.EPZ WATCHES/WARNINGS/ADVISORIES...
NM...None.
TX...None.
&&
$$
25-Hardiman / 26-Grzywacz
Area Forecast Discussion
National Weather Service Grand Forks ND
917 PM CDT Sat Aug 18 2018
.UPDATE...
Issued at 917 PM CDT Sat Aug 18 2018
The surface boundary appears to be located somewhere along a line
from Bismarck to Rugby to Winnipeg. Storms have been firing over
southwest North Dakota and north central South Dakota, as well as
near Winnipeg. However, so far nothing in this FA. The HRRR is
still holding to its guns, depicting some precipitation breaking
out along the frontal boundary after midnight and continuing into
Sunday.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 309 PM CDT Sat Aug 18 2018
Wildfire smoke continues to impact the Northern Plains and Upper
Midwest today. Smoke has dissipated somewhat since yesterday but
is still present overhead. This lead to slightly higher than
expected temperatures with highs today now forecast to be in the
mid to upper 80s. Much of this smoke is expected to clear out
with the cold front that will move though tonight into tomorrow.
This cold front will also have some higher winds that we are now
experiencing as the pressure gradient tightens. Rain showers with
some thunderstorms are expected to fire along this cold front
tonight into tomorrow. The best chances for rain and thunderstorms
tonight will be in eastern North Dakota and far northwest
Minnesota. As the front continues to move to the southeast the
rain and thunderstorms chances will move to the southeast
spreading the chances into west central and the rest of northwest
Minnesota.
Severe weather is unlikely with weak shear present but
ML CAPE in the 1500 to 2000 J/kg range will provide the
instability for thunderstorms. Another limiting factor is the cap
which will help to limit the occurrence of thunderstorms. The
best chances for thunderstorms will be along the cold front thanks
to the synoptic lift that it will provide.
.LONG TERM...(Sunday night through Saturday)
Issued at 309 PM CDT Sat Aug 18 2018
An amplified west coast H5 ridge and mid continental trof will set
the stage for the early into mid week period... providing at least
the possibility of a somewhat freshened and cooler northerly blayer
flow into the area from Monday into Tuesday. Highs are expected to
reach only into the 70s either day. In regards to air quality...
there is a caveat, however, as at least one Canadian smoke plume
model would show a strong return of intense smoke into northwest MN
with the north winds on Monday... from fires along the MB/ON border.
And, since very little rain is expected to accompany this weekends
frontal passage its a good bet that existing large fire areas across
central and western Canada will persist in some form into the coming
work week.
Thus when surface high pressure, originating in west central Canada,
settles over the area from Tuesday into Wednesday... we will likely
see the return to a somewhat smokey and/or hazy sky and a reduced
air quality. Light and variable winds on Tuesday should turn from
the south on Wednesday... but the same dry and smokey airmass
qualities are likely to persist. Temperatures on Wednesday and
Thursday should rise near seasonal normals /lower to mid 80s/ for
the mid week period... but if substantial smoke is also present,
expect this warming to be somewhat reduced.
There is some hope as we get to the late week period... for a more
substantial and widespread rainfall, and for a improvement in air
quality. Mid range forecast models agree in bringing a strong H5
shortwave trof into the Northern Plains area late Thursday into
Friday which could flush any lingering smoke from the area and
provide rainfall to fire affected area in central and western Canada
to boot.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 651 PM CDT Sat Aug 18 2018
The regional radars show the surface boundary nicely, extending
from near Killdeer to Minot in western North Dakota. There has
been some shower/TSTM activity near Killdeer, but not much to the
northeast of there. Shear is nearly non existent, so not sure
there is much to push this western activity eastward. However, the
HRRR runs are pushing the activity toward KDVL by around midnight,
and KGFK/KFAR several hours later. Doubting there will be much
coverage though, so kept a VCTS mention for now. Looks like more
organized coverage is possible at KFAR Sunday afternoon.
Otherwise do expect winds to lighten up after dark, then switch
to the north behind the frontal boundary. Guidance is showing it
getting fairly breezy Sunday afternoon, with the north winds
behind the front.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Godon
SHORT TERM...NC
LONG TERM...Gust
AVIATION...Godon
Area Forecast Discussion
National Weather Service Glasgow MT
903 PM MDT Sat Aug 18 2018
.DISCUSSION...
Main change this evening was to tweak the patchy smoke tomorrow.
We should get a break for most of the area (per experimental HRRR
Smoke), with better air quality at the surface. Used the
Vertically Integrated Smoke display to draw in patchy smoke for
Sunday.
Will let the Dense Smoke Advisory expire on-time (9 pm MDT/3Z) as
visibilities have climbed and stayed above 3 miles.
Should be a cool night tonight compared to the last several, with
lows dipping into the 40s and 50s across the CWA and a mild day
tomorrow with highs mostly in the 70s with a few 80s dotted in.
Avery
Previous Discussion...
A vigorous short-wave trough is sliding through eastern MT today
and tonight. This storm initially brought thunderstorms to the
area, but they have since moved south. Rain showers are ongoing,
but will move out of the area by Sunday morning. The surface
analysis depicts a cold front pushing south from Canada. Its main
affect will be to lower temperatures to below normal. There still
is plenty of wild fire smoke spreading over the region. It remains
to be seen if there will be much clearing of this smoke before
Sunday. Smoke was dense enough and unhealthy enough to issue a
dense smoke advisory for Phillips & Valley Counties, based on
written guidance. Templer
Previous discussion for Sunday and beyond:
Cooler weather will move in by the end of the weekend and early
next week, as another trough moves into the northwestern CONUS.
This will bring another chance of showers to the area Monday, with
high temperatures mainly in the 70s across the region.
The cool weather will be short-lived as by the middle of next
week, an upper ridge will set up over the area, and temperatures
will once again reach the 80s and 90s across northeast Montana.
Beyond this, expect mainly zonal flow with embedded shortwave
troughs from Thursday through the end of next week, although
little to no precipitation is expected from these. Temperatures
are expected to remain within a few degrees of normal during this
period.
Hickford
&&
.AVIATION...
FLIGHT CATEGORY: MVFR (HZ) to VFR. VFR expected on Sunday.
DISCUSSION: Showers across the region associated with a cold front
and upper level trough will move out of the area overnight
tonight. Visibilities should briefly improve on Sunday for much of
the area, although hazy conditions are expected to make a return
to the area late Monday into Monday night. Visibilities at TAF
locations should be over 6 SM on Sunday.
WINDS: Generally out of the N between 10 to 15 knots.
Avery
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
weather.gov/glasgow
Area Forecast Discussion
National Weather Service Hastings NE
702 PM CDT Sat Aug 18 2018
.SHORT TERM...(This evening through Sunday)
Issued at 204 PM CDT Sat Aug 18 2018
A few light rain showers are currently moving east-northeast
across west-central Kansas. This appears to be associated with an
area of weak isentropic ascent ahead of the main trough that will
impact the area late tonight through tomorrow. For the most part,
models don`t have a good grasp on this, with only the last few
runs of the HRRR starting to initialize this activity.
Nevertheless, it appears that parts of north-central Kansas may
see a light shower through late afternoon, before these showers
dissipate this evening.
This evening, models agree that thunderstorms should continue to
develop over western Nebraska and Kansas...gradually moving
eastward with the deepening upper trough. It appears that
most...if not all...of the forecast area will remain dry through
midnight tonight, and the bulk of the precipitation should move in
after 3am. At this time, it appears that any marginally severe
storms that develop should weaken to below severe criteria before
reaching the forecast area.
By mid to late morning on Sunday, the trough axis will be pushing
into the local forecast area, which should lead to fairly
widespread showers and thunderstorms across the area into the
early afternoon. The threat for severe weather continues to be
minimal, as the saturated atmosphere limit instability. Deep layer
shear is also very lackluster.
Locally heavy rain will likely be the main threat. While PW
values of 1.6-1.8" aren`t "off the charts", they still are quite
high for this time of year and indicative of efficient rainfall
production. Model QPF is widely variable, but most models have a
bullseye of at least 2-2.5" somewhere in the forecast area. Given
that this will be a relatively long-lived event, any flooding
threat should be confined to low-lying areas and areas near
creeks/streams.
There could be a bit of a lull in precipitation during the
afternoon as the center of the upper low moves into the
area...especially across south and western parts of the the
forecast area. Overall, the forecasted PoPs are quite high through
this entire period, but I do believe that there will be dry
periods through the day. Unfortunately, the timing of these dry
periods is near impossible to pin down.
The widespread precipitation and cloud cover should limit high
temperatures to the low 70s on Sunday.
.LONG TERM...(Sunday night through Saturday)
Issued at 204 PM CDT Sat Aug 18 2018
By Sunday night, the corridor of deepest moisture will have moved
off to the east of the forecast area, but we should continue to
see scattered showers and perhaps a few thunderstorms wrap around
the backside of the low through the overnight and into Monday
morning.
By late Monday morning and early afternoon afternoon, the
forecast area will begin to dry out from west to east. Monday will
also bring gusty northerly winds. Gusts of 30 to 35 MPH are
possible across the area...which would be some of the strongest
non-convective winds that the area has seen in quite some time.
With highs only in the 70s, it may even feel chilly for mid to
late August.
Dry conditions will prevail Monday night as high pressure settles
into the area. Decreasing winds and clearing skies should allow
overnight lows to dip into the low to mid 50s.
Dry and mild conditions continue Tuesday, but a series of weaker
disturbances will move through the area Tuesday night through
Thursday night, bringing slight chances for rain and storms to
portions of the forecast area. Temperatures should also gradually
bounce back closer to climatological normals (highs in the low
80s) by Thursday.
At this time, the Friday and Saturday appear to be warm and
mostly dry across the area. High temperatures are once again
forecast to reach the mid to upper 80s.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday)
Issued at 654 PM CDT Sat Aug 18 2018
High clouds are working into the area from the western
thunderstorms, but any rainfall should hold off until after
midnight at our TAF sites. Rain is likely early Sunday morning
with some lightning around but more just a nice steady rain. The
wind will remain light and out of the south this evening, but will
become more variable tomorrow in and around the showers, but
should remain light. Ceilings are expected to fall Sunday morning
into the MVFR range in the rain. We might see improvement in the
ceiling heights until late Sunday afternoon.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
SHORT TERM...Mangels
LONG TERM...Mangels
AVIATION...Wesely
Area Forecast Discussion
National Weather Service Grand Junction CO
542 PM MDT Sat Aug 18 2018
.SHORT TERM...(Tonight through Sunday night)
Issued at 304 PM MDT Sat Aug 18 2018
Many residents on the western slope woke up to rainfall and
cleaner skies as a recent cold front and upper level trough moved
through the area, helping clear the valleys of persistent smoke
from local and regional wildfires. Much of the cold front is
already on the Front Range with the trailing southern edge of it
currently moving through Archuleta county in our extreme southeast
corner of our CWA. Some isolated storms are forming along the
ridges in the trailing northwest flow but do not expect much out
of these storms as they will remain of the pop and drop variety
with much drier air moving in behind this system and much weaker
instability. The storm activity will shift focus over northwest
Colorado late this afternoon into the early evening as the front
moves well east of the area, before ending by or after sunset. The
temperatures will be noticeably cooler tonight into Sunday in the
wake of this departing cold front with much drier conditions as
precipitable water (PW) values drop below 0.5 inches.
Enjoy the cleaner air this afternoon while it lasts because smoke
from wildfires burning out west will move back into the region
this evening and linger through at least Sunday evening according
to the latest HRRR smoke model. The main players appear to be the
Coal Hollow wildfire in northeast Utah for near surface smoke and
the Watson Creek wildfire in Oregon for smoke higher up in the
atmosphere, mainly impacting eastern Utah and portions of
southwest Colorado by Sunday. Smoke from British Columbia and the
state of Washington looks to make it to northwest Colorado by
Sunday as the flow shifts to more north-northwest by Sunday
afternoon as the ridge of high pressure rebuilds out west over the
Great Basin. Due to the slightly faster flow on Sunday behind the
departing shortwave trough, breezier conditions will be seen with
some marginal critical fire weather conditions possible over
southwest Colorado. The coverage and timing was not enough to
warrant fire weather highlites.
.LONG TERM...(Monday through Saturday)
Issued at 304 PM MDT Sat Aug 18 2018
The ridge of high pressure slides over the New Mexico-Arizona
border south of the Four Corners by Monday as a trough moves into
the Pacific Northwest. A shortwave looks to eject ahead of this
PacNW trough with a trailing boundary moving through northeast
Utah and northwest Colorado Monday evening through Tuesday
morning. The models are not in great agreement on how to handle
this shortwave with the NAM being the driest of the models and the
GFS being wetter. Thinking there is potential for at least
isolated coverage of showers and thunderstorms mainly north of
I-70 Monday evening. Overall though, Monday looks to be a mostly
dry day with temperatures warming up a bit from Sunday`s post-
frontal airmass.
By Tuesday, an upper low splits off the main trough and forms a
brief rex block over the PacNW. This looks to be enough to help
shift the high pressure ridge further east into eastern New Mexico
and allow subtropical monsoonal moisture to work northward through
Arizona and Utah and spread into western Colorado by Tuesday
evening. The PacNW trough merges with the upper level flow and
passes through the northern Rockies late Wednesday afternoon and
evening into Thursday morning. Bottom line, late Tuesday through
Thursday morning appear to be the peak in moisture surge and
noticeable increase in thunderstorm activity and coverage as these
embedded disturbances rotate through this southwest flow with PW
values increasing above 0.75 inches with values nearing an inch or
greater across southeast Utah and southwest Colorado. The
deterministic models all seem to remain in fairly good agreement
with the overall synoptic pattern, so confidence is high in this
time period being the better days for increased moisture and
thunderstorm activity, some of which looks to persist through the
overnight hours. Therefore, increased the PoPs to at least chance
and expanded the coverage to include valleys as well through this
period.
Moisture drops off a bit by Thursday through the coming weekend
but remains elevated enough with PW values near or above 0.75
inches south of I-70. The high pressure area remains positioned
east over the New Mexico-Texas border with embedded wiggles in the
flow, which is favorable to keep thunderstorms in the forecast
each afternoon and evening through the period. This is by no means
a significant surge of monsoonal moisture but will be noticeable
and at this point in time, any moisture is welcome as the west
continues to burn. Temperatures through the period look to remain
a few degrees above normal, but depending on how much moisture
increases, daytime highs mid week onwards could be lower than
forecast.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 539 PM MDT Sat Aug 18 2018
Isolated showers and thunderstorms will continue to affect NE UT
and NW CO until sunset. These will be in the vicinity of KHDN,
KEGE, and KASE until about 03z. Gusts between 25-35 MPH area
expected with these storms. VFR conditions will prevail thereafter
and at all other TAF sites for the next 24 hours.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...MDA
LONG TERM...MDA
AVIATION...CC
Area Forecast Discussion
National Weather Service Huntsville AL
717 PM CDT Sat Aug 18 2018
.NEAR TERM...(Tonight)
Issued at 716 PM CDT Sat Aug 18 2018
Have made some minor adjustments to PoPs this evening and tonight.
Radars currently detect just a few showers in southern portions of
our forecast area (south of Moulton to Guntersville). The shower band
between Lynchburg and Nashville in southern middle TN are slowly
drifting southeast. The weak convergence zone along and near the I-40
corridor has little to no development west-southwest of Nashville.
Have configured PoPs this evening to better fit these convergence
zones, but confidence in overnight weather is rather low. The HRRR
runs are showing isolated-scattered development, but exact locations
are still such that I will keep the PoP at a chance level. Lower
clouds are likely to develop as well given the very moist lower 2km
per the 00Z OHX sounding.
.SHORT TERM...(Sunday through Monday)
Issued at 225 PM CDT Sat Aug 18 2018
A potential wet pattern remains in place on Sunday as a surface
boundary stalled north of the region drifts north as a warm front.
Again, a caveat remains the south to north moisture gradient, which
would again favor central AL for better coverage of showers/storms as
opposed to N. AL and S. Middle TN. As such, on average, have under
cut Superblend PoPs a bit for tomorrow. Still cannot rule out some
scattered showers during the afternoon tomorrow given a southerly
component to the flow regime and a surface boundary near our northern
border.
As we head into Monday, expect deeper southerly flow to develop ahead
of an approaching cold front, progged to shift through the region
later this week. Additionally, there will be some mid/upper level
support for more organized thunderstorms, so we cannot rule out the
potential a strong storm or two for Monday afternoon/evening. Partly
to mostly cloudy conditions through the period will keep temps maxed
in the mid to upper 80s each afternoon.
.LONG TERM...(Monday night through Friday)
Issued at 225 PM CDT Sat Aug 18 2018
A mid-level trough, located across southeastern IA/northeastern MO
at the beginning of the extended period, is predicted to deepen and
lift east-northeastward into the eastern Great Lakes by 00Z
Wednesday. Downstream west-southwesterly flow and attendant lower-
tropospheric WAA will strengthen across the TN Valley on Monday
night, supporting a fairly widespread coverage of nocturnal
convection in the very moist airmass (PWATs in the 1.9-2.1 inch
range). Although lightning and locally heavy rainfall will be the
primary threats with this activity, increasing deep-layer shear may
support some storm organization and a threat for strong wind gusts
with the most intense cells.
Extended range guidance from the global models indicates that the
trailing mid-level trough axis and surface cold front will cross the
forecast area after sunrise on Tuesday morning, with lingering
showers and thunderstorms expected to end rather quickly across the
southeastern zones. However, for much of the mid-week period, the
region will remain beneath a northwest flow aloft along the
northeastern periphery of a large subtropical high centered across
eastern NM/western TX. Several weak disturbances traveling
southeastward in the northwest flow aloft may provide sufficient lift
for the generation of isolated-widely scattered showers on Tuesday
night/Wednesday, before atmospheric moisture becomes depleted by
persistent northerly flow at the surface from Wednesday night-
Thursday night. Max temps will range from the lower 80s in the
elevated terrain of the northeast, to the m-u 80s elsewhere. Lows
will respond more effectively to the southward advection of drier
air, with lower 60s expected on Thursday/Friday mornings.
Low-level southeasterly flow will become reestablished across the
CWFA on Friday-Saturday, as a surface ridge builds southward in the
lee of the Appalachians. This should allow for at least some return
of deeper moisture, with scattered afternoon convection possible both
days.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 529 PM CDT Sat Aug 18 2018
A weak front in TN will drop south into north AL producing isolated
to scattered thunderstorms overnight. However, confidence is too low
to include at either KMSL or KHSV at this time. Scattered to broken
clouds at ~050agl are expected at times this evening before lower
clouds and IFR conditions (ceilings of ~005-008agl) develop by 06Z.
These clouds will slowly lift to ~025agl by 15Z, then lift and
possibly scatter out by midday Sunday. However, scattered showers and
thunderstorms will remain possible, and may need to add to the
forecast when it becomes more certain at our terminals.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...17
SHORT TERM...Barron
LONG TERM...70/DD
AVIATION...17
For more information please visit our website
at weather.gov/huntsville.
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1055 PM EDT Sat Aug 18 2018
.UPDATE...
Issued at 1055 PM EDT SAT AUG 18 2018
With some holes in the clouds showing up on satellite, subsidence
behind the passing cold front, and plenty of ground moisture
around expect areas of dense fog to form overnight in places where
low stratus does not late hold. Due to the cloud cover uncertainty
will go with an SPS for the fog rather than an NPW and also run
it through 5 am so that the midnight shift can reevaluate before
dawn Sunday. Otherwise, have taken out the thunder chances and
lowered PoPs to 20 percent or less through the night. Have issued
new zones and HWO to account for the thicker fog in the wx grids.
For this update have also added in the latest obs and trends for
the T and Td grids. The updated grids have been sent to the NDFD
and web servers.
UPDATE Issued at 745 PM EDT SAT AUG 18 2018
23z sfc analysis shows the cold front responsible for the shower
and thunderstorm activity across eastern Kentucky this afternoon
and evening cutting through the area. This will gradually bring
drier conditions to the CWA later this evening and through the
night. Meanwhile, training cells and high PW air has led to some
flash flooding concerns across eastern Kentucky with Corbin and
Barbourville most notably affected by flowing water across local
roads. Things are quieting down now with the coldest cloud tops
warming and departing the area to the east. Temperatures are
running in the low to mid 70s with dewpoints nearly matching their
values. Winds outside of any storms have been light and generally
from the southwest.
Cannot rule out a stray shower or thunderstorm for the rest of
the evening, but most places will be dry per trends and the latest
CAMs guidance. Attention then turns to post frontal fog
development later tonight for a good portion of the area -
especially in the valleys - though a build down of stratus could
also result in limited visibility on the ridges after midnight.
Have updated the forecast with these thoughts in mind. Also added
in the latest obs and trends for the T/Td grids. The updated grids
have been sent to the NDFD and web servers along with the
issuance of a freshened set of zones and HWO.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 358 PM EDT SAT AUG 18 2018
Current surface observations show a cold front moving over
Kentucky, coincident with the passage of an upper level shortwave.
Convection has been forming ahead of the front, as seen in
current radar signatures, and gradually moving southeast. The main
threats with this convection will be heavy rainfall, leading to
flooding concerns. A Flood Advisory was issued earlier this
afternoon just north of the Mountain Parkway due to higher rain
rates in the convection. Rain rates in this line have since
decreased, but this will continue be monitored through the evening
with the development and progression of other convection. This is
particularly true in areas that have seen heavier rainfall during
the day such as the area from Breathitt County to Pike County. A
Flood Advisory as well as a Flash Flood Warning was recently
issued for portions of this area in Floyd County.
The HRRR did not seem to have a very good handle on current
trends, but the CONSShort did have heavier PoPs in the north with
the advancement of the lines of convection. Therefore, used the
CONSShort as a baseline for PoPs. Made minor adjustments to better
show the current radar trends and expected progression. The cold
front is expected to slow and stall just to the south of the
Commonwealth. This will keep chances of showers through Sunday,
mainly in the southeast. However, a weak upper level ridge will
set up Sunday night, bringing a brief lull in precip overnight
into Monday. A warm front, associated with a low pressure system
located over the Central Plains, will begin to lift northward over
Kentucky Monday morning and increase the potential for some
showers into the afternoon.
Stuck close to guidance and CONSShort for temperatures. Low
temperatures tomorrow morning will be in the upper 60s and
afternoon highs will be in the low 80s. Lows Monday morning will
also be in the upper 60s, but valleys could potentially see
slightly cooler temperatures with the clearing of clouds
overnight.
.LONG TERM...(Monday through Saturday)
Issued at 407 PM EDT SAT AUG 18 2018
At the start of the period an upper level short wave trough and
associated surface low will be in the vicinity of the IA/NE/MO tri
state area. This system will advance east northeast towards the
lower Great Lakes. Initially this will result in a warm front moving
across the area from Monday into Monday night with a trailing cold
front then pushing across the area on Tuesday. With a good flow of
deep moisture in advance of this system we`ll see increasing shower
and thunderstorm chances on Monday, with the best chance for showers
and thunderstorms on Tuesday with the cold front. The overall upper
level system will be weakening as it moves east northeast, but mid
level wind fields still look fairly strong as we move into Monday
night and Tuesday. Depending on exact timing of the cold front
passage it is possible we could see some strong storms on Tuesday.
Some showers may linger into Wednesday, but the end of the week will
feature cooler and drier weather as the front moves into the
southeastern United States and surface high pressure builds into the
area. Temperatures will be below normal for the end of the week
before warming again next weekend as surface high pressure slides to
our east.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 820 PM EDT SAT AUG 18 2018
While the convection will die down over the next few hours there
is the expectation that later this evening and overnight will see
low CIGs and VIS in fog from some post frontal radiational effects
along with a stratus build down. As a result, have some MVFR BR
and IFR CIGs developing later tonight at all sites. The VIS should
improve following sunrise, though lower CIGs will likely linger
into the afternoon along with the potential for a stray shower for
the southern sites on Sunday. Winds will generally be light and
variable through the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GREIF
SHORT TERM...CGAL
LONG TERM...SBH
AVIATION...GREIF
Area Forecast Discussion...UPDATED
National Weather Service Miami FL
727 PM EDT Sat Aug 18 2018
.AVIATION...
The winds will be mostly light and variable tonight, except for
KAPF taf site where the winds should remain more of a easterly
direction around 5 knots. The weather should remain dry this
evening, before VCSH conditions after 6Z tonight for the east
coast taf sites as showers work into the east coast metro areas
from the Atlantic waters. There could even be a thunderstorm late
tonight, but the coverage is to small to put into the east coast
taf sites at this time. KAPF taf site will remain dry tonight.
The ceiling and vis will also remain in the VFR conditions
tonight, but could fall down into MVFR conditions with any shower
or thunderstorm passage.
&&
.AVIATION..54/BNB
.PREV DISCUSSION... /issued 638 PM EDT Sat Aug 18 2018/
UPDATE...
Quick update to the forecast package for this evening over South
Florida. The showers and thunderstorms have dissipated over the
region late this afternoon leaving the weather dry. The latest
SREF and HRRR models are showing dry conditions through the
evening hours over South Florida. Therefore, the pops have been
removed from South Florida for the evening hours.
Rest of the forecast looks good at this time and no other changes
are planned.
UPDATE...54/BNB
PREV DISCUSSION... /issued 339 PM EDT Sat Aug 18 2018/
DISCUSSION...
Scattered to numerous showers and thunderstorms have developed
across South Florida this afternoon. The greatest coverage of
convection has been located across the interior and west coast
areas. Most of this activity will begin to diminish as the evening
progresses. A slight chance of showers and thunderstorms will
still remain over the Atlantic waters as well as the east coast
metro areas during the overnight hours. Low temperatures will
range from the lower 70s across interior areas to near 80 across
the east coast metro areas. High pressure over the western
Atlantic will remain in control of the weather pattern through
the rest of the weekend and into early next week. Latest computer
model guidance continues to show an east to southeasterly flow
across the region. This will allow for an increase in low level
moisture to continue as well which will keep the chances of
showers and thunderstorms elevated. These showers and
thunderstorms will develop during the late morning and early
afternoon hours as the east and west coast sea breezes move
inland. The greatest chances of showers and thunderstorms will
remain over interior and west coast sections during the afternoon
hours. There will also be enough instability to support one or two
strong storms especially across the interior sections.
As the middle of the week approaches, both of the GFS and the
ECMWF show a similar weather pattern remaining in place. The area
of high pressure located over the western Atlantic does not move
much which will allow the southeasterly flow to continue. A
typical summertime weather pattern is expected during this time
frame with showers and thunderstorms developing along the east and
west coast sea breezes during the late morning hours. The
convection will then push towards the interior sections during the
afternoon and evening hours. Temperatures each afternoon should
reach near 90 degrees along the coast and low 90s for the
interior.
MARINE...
An area of high pressure located over the western Atlantic will
continue to dominate the weather pattern across the local waters
through the middle of the week. Moderate east to southeasterly
flow will continue across the Atlantic and Gulf waters with seas
generally remaining at 2 feet or less. Scattered showers and
thunderstorms will be possible each day. Winds and waves could be
higher in and around any shower or thunderstorm.
&&
.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach 77 89 77 91 / 20 40 20 20
Fort Lauderdale 80 89 80 90 / 30 50 20 20
Miami 78 89 78 90 / 30 50 20 30
Naples 76 91 76 91 / 10 40 20 40
&&
.MFL WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
GM...None.
&&
UPDATE...54/BNB
DISCUSSION...55/CWC
MARINE...55/CWC
AVIATION...54/BNB
Area Forecast Discussion
National Weather Service San Francisco Bay Area
857 PM PDT Sat Aug 18 2018
.SYNOPSIS...Very warm conditions will persist inland on Sunday,
although temperatures are expected to be a few degrees cooler
than today. An upper disturbance will move into Northern
California by late Sunday and generate a modest cooling trend
regionwide during the first half of the work week. Below seasonal
temperatures can be expected near the coast, in conjunction with a
deepening marine layer, while near to slightly above seasonal
temperatures will persist inland. Seasonal conditions are expected
later in the week.
&&
.DISCUSSION...As of 8:55 PM PDT Saturday...Temperatures at most
inland locations inched slightly higher today as an upper ridge
reached its maximum strength over California. Most inland valleys
warmed into the 90s. The warmest location in our forecast area
today was Pinnacles National park with a high of 106. A shallow
marine layer persisted near the coast, as did light onshore flow.
Thus, coastal temperatures remained mostly in the 60s and lower
70s. Whale Point, on the southern Monterey County coast had a high
today of only 55, which is 51 degrees cooler than the 106 at
Pinnacles just 35 miles to the northeast.
Evening water vapor satellite imagery shows a weak upper trough
just off the coast of the Pacific Northwest. This trough is
forecast to dig southeast into the Pacific Northwest on Sunday and
into northern California from Sunday night into Tuesday. Impacts
from the upper trough are expected to mostly be felt starting
Monday, but minor effects are expected tomorrow. There will
likely be an uptick in onshore flow by late afternoon and the
marine layer may begin to deepen from its current depth of 1000
feet. Modest cooling is likely in the coastal valleys and around
San Francisco Bay tomorrow, but no more than a few degrees of
cooling is expected for the inland valleys and hills. Thus, expect
another very warm day inland tomorrow. Low clouds and fog will
likely persist along the coast, helping to maintain cool
conditions in coastal communities. The latest HRRR Smoke model
indicates continued poor air quality across the Bay Area on Sunday
as smoke from the Mendocino Complex increases across the area.
Inland areas are expected to experience relief from the heat early
in the work week as the trough sags into northern California,
triggering a increase in the depth of the marine layer. The inland
valleys are expected to cool by as much as ten degrees by Tuesday.
The upper trough is forecast to move off to the east by Thursday,
allowing for slightly warmer temperatures late in the week.
Longer range models agree that a longwave trough will develop
across the western United States by next weekend and perhaps
persist for a while. The Climate Prediction Center`s 8-14 day
outlook calls for near normal to below normal temperatures across
northern and central California during the final week of August.
&&
.AVIATION...as of 5:27 PM PDT Saturday...Webcams, metars,
satellite imagery show a fair amount of wildfire smoke and haze
over the Bay Area, biggest impacts have been reduced slant range
visibilities as well as areas of haze and smoke resulting in MVFR
surface visibilities. Hazy conditions aloft have also reached as
far south as the Monterey Bay Area. A few pireps from earlier on
in the vicinity KSTS and KUKI flight levels 2500-7000 feet
indicated vsby 3 miles in smoke, recent pirep during descent into
KLVK reports 3.5 miles visibility.
The latest high-res rapid refresh model shows an increasing trend
in smoke originating from the Mendocino Complex spreading into
the Bay Area overnight and Sunday. Coupled with the smoke will be
a steady influx of marine based stratus and fog, stratus ceilings
on the coastline are IFR as the marine layer is compressed to 1000
to 1500 feet deep. Visible imagery this afternoon shows a
widespread coverage of stratus and fog over the coastal waters. As
cigs and vsbys on the immediate coast and locally inland lower
tonight LIFR and VLIFR will likely develop.
Vicinity of KSFO...VFR. Westerly winds 15-20 knots until 04z then
lighter westerly winds tonight, increasing chances of MVFR visibility
by early Sunday morning due to smoke and haze. Some improvement in
surface visibility is possible at KSFO while slant range vis will
quite likely remain moderate to poor Sunday.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...IFR developing between 02z and 04z, LIFR to
VLIFR late tonight and Sunday morning. Clearing to MVFR-VFR conditions
by late Sunday morning and afternoon. Coastal stratus and fog likely
moving back in Sunday evening.
&&
.MARINE...as of 4:50 PM PDT Saturday...Northwest winds will
remain generally light through the week as high pressure resides
over the eastern Pacific and an inland trough sits over
California. Expect locally gusty northwesterly winds in the
northern outer waters through Tuesday. Light to moderate mixed
northwest and southerly swell will continue through the weekend.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm
&&
$$
PUBLIC FORECAST: Dykema
AVIATION: Canepa
MARINE: AS
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Area Forecast Discussion
National Weather Service Paducah KY
622 PM CDT Sat Aug 18 2018
.UPDATE...
Issued at 622 PM CDT Sat Aug 18 2018
The AVIATION section has been updated for the 00Z TAF issuance.
&&
.SHORT TERM...(Tonight through Monday night)
Issued at 125 PM CDT Sat Aug 18 2018
Mid level trof axis will depart to the east late today and this
evening. Until it does, some lingering showers will continue
through sunset, maybe an hour or so after. Mid level lapse rates
are weak, so will just mention isolated showers. One or two
lightning strikes possible. Convection is rather shallow.
Overnight a weak surface ridge will calm winds. This coupled with
breaks in the clouds and residual high surface RH, means some fog
possible late tonight. There may also be return low clouds given
high H9 moisture content and some advection from the east. That
could have a direct impact on any fog potential. Will monitor.
Most of Sunday should be dry. By the end of the day, a s/wv ridge
will be across the region. Prior to that, in the afternoon,
isolated convection cannot be ruled out across the KY Pennyrile,
maybe slightly farther west. Sunday night, focus for convection
will be mainly along and west of the MS River after midnight as a
surface low deepens over the central Plains and heads northeast
into NW Missouri by Monday morning, coincident with weak mid level
energy over Missouri. Compact strong H5 low and assoc surface low
will move across the upper Midwest Monday, with scattered
convection anticipated across the region in a warm and unstable
southerly flow regime. Chances will continue Monday night as a
surface front approaches and mid level forcing increases with the
approach of the upper trof. The chance for severe storms seems
highly conditional on clouds and existing convection. This and
forecast lapse rates are fairly lame. So concern for severe is
minimal to nil based on the latest forecast data.
15
.LONG TERM...(Tuesday through Saturday)
Issued at 125 PM CDT Sat Aug 18 2018
Given the numerical model initialization with the 12z upper air
data, the 00z Saturday ECMWF and and 12z RAP guidance had a fairly
decent handle on the northwest U.S. closed low. The timing and
location of this feature may still be an influence at the beginning
of the extended forecast period.
Adjusting for spatial and temporal model drift, the closed low
currently over the northwest U.S. today, should be an open high
amplitude, somewhat progressive, trough with the mean axis along the
Wabash and Ohio River. Weatherwise, this would place the best
chances for showers and a few thunderstorms over southwest Indiana
and West Kentucky at the beginning of the period.
Despite the passage of this trough and associated surface cold
front, decent cold air advection will not make headway into the area
until Wednesday morning. During this time, a northeastward tilted
ridge will be in place with 50H center near the eastern AZ/northwest
TX border and a surface ridge center in eastern NE and far west IA.
Further to the east, the trough axis that moves through on Tuesday
will be vertically stacked along the east coast. The pattern places
the WFO PAH forecast area in northwest flow just south of the
sharpest baroclinic zone and channeled/sheared vorticity, and just
east of the deeper layer moisture poised northeast of the upper
ridge in the southwest U.S.
The displacement of these features allows for a greater influx of
cooler and drier air into the WFO PAH forecast area Wednesday
through early Thursday afternoon, with warming taking place Thursday
night as a surface ridge moves east of the WFO PAH forecast area.
The trajectory of the moist low and middle level moisture eventually
works northward from the Gulf of Mexico by midday Friday,
intersecting weak upper level troughing further to the west, aiding
in slow moisture advection into western Missouri.
A mean trough axis centers over the WFO PAH forecast area by midday
next Saturday. This axis, combined with Gulf Moisture should support
at least a chance probability of precipitation during the afternoon
hours next Saturday.
In summary, there should be a chance of rain on Tuesday, then again
later next Saturday. In between those times, a brief cool down
below normal temperatures should take place, with the coolest
temperatures centered around early next Thursday.
KES
&&
.AVIATION...
Issued at 622 PM CDT Sat Aug 18 2018
Scattered showers will linger through sunset mainly from KHOP to
K2I0 eastward. Otherwise, the forecast is dry. Fog, possibly
dense, and/or low ceilings is expected over most of the region for
a few hours straddling sunrise. Limited IFR mention to KCGI at
this time, but LIFR conditions cannot be ruled out at any of the
TAF sites. There is a strong signal for MVFR ceilings to linger
through the morning and then lift to VFR levels by early
afternoon.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
UPDATE...DRS
AVIATION...DRS
Area Forecast Discussion
National Weather Service Reno NV
224 PM PDT Sat Aug 18 2018
.SYNOPSIS...
The streak of 90 degree days will continue across the Nevada
valleys over the next few days, while overnight lows provide
relief from what could be the hottest summer on record. Gusty
afternoon and evening winds may produce short periods of critical
fire weather conditions the next few days.
&&
.SHORT TERM...
The main concern the next couple days is the afternoon and
evening zephyr gusts near 30 mph combining with very low humidity.
Details in the fire weather section below.
Winds Sunday and Monday will produce choppy conditions on area
lakes. The zephyr winds typically develop between 2 and 4 pm. If
you are out on a lake in the afternoon be prepared for a quick
uptick in winds and resultant waves.
Afternoon highs could reach record levels Sunday. The forecast
high of 99 for Reno would tie the record for Aug 19 set in 2003
and 2009. There is some relief in sight as low pressure remains
near the west coast, which is also why we`re going to into a
period of breezy afternoon winds. Highs will decrease, but remain
at least in the low 90s. The Sierra will cool into the mid-70s to
mid-80s by mid week.
Smoke and air quality appear to be a decreasing issue the next
day or so based on the last couple runs of the HRRR smoke model
and excellent smoke dispersion from afternoon and evening winds.
Aside from any new fire activity, smoke and haze will be limited
to northeast CA and northwest NV and portions of Alpine and Mono
counties very near the Donnell and Lions fires. Brong
.LONG TERM...Wednesday and beyond...
A small amplitude trough over the Pacific NW will lift to the
northeast Wednesday. The 12Z run of the GFS has shown the trough
to sag further south than previously shown. If this solution holds
true, Wednesday afternoon could be the windiest day this coming
week. However, this is a big if since model solutions have been
fluctuating considerably with the position of this trough. Other
than this change, no noteworthy alterations were made to the
forecast.
Past Wednesday, the ridge over the southwest US will momentarily
build northward before another trough approaches the Pacific NW
late Thursday into Friday. This will keep dry southwesterly flow
over western Nevada and eastern California. Hence, there is no
mention of thunderstorms in the forecast. Usual afternoon zephyr
winds will occur with some enhancement expected due to troughs
skimming by to the north. Daytime highs will continue to be above
normal with 90s in the lower valleys of western Nevada and highs
in the 80s for the Sierra. Overnight lows will be close to
seasonal averages in the 50s- near 60 degrees for lower
elevations, with low 40s near the Sierra. -Johnston
&&
.AVIATION...
Smoke from fires in northern California and southern Oregon have
reduced visibilities to less than 6 miles at the northern terminal
areas of SVE, LOL, and NFL. Current guidance shows that this smoke
should stay to the north of RNO-TRK. However, if it does move
southward, slant-wise and flight level visibility could be reduced
at terminal areas north of CXP. Besides this concern, expect dry
conditions with light winds this afternoon and evening. Afternoon
breezes will be enhanced Sunday and Monday as a trough passes by
to the north. -Johnston
&&
.FIRE WEATHER...
The presence of an upper-level trough of low pressure to our
north over Oregon will enhance the typical zephyr winds both
Sunday and Monday...especially north of Highway 50. Gusts in the
valleys should easily reach 25-30 mph with some wind prone areas
along the Highway 395 corridor briefly exceeding 30 mph. Humidity
values remain low as well...so there may be a few areas with a
brief period of critical conditions in zones
271/278/270/458/450/453. These periods of brief critical
conditions should not persist for more than a couple of hours from
very late in the afternoon into the early evening. If the upper
trough were a bit farther south we would be looking at a longer
period of critical conditions...but this forecast scenario does
not line up well enough to produce a long-lived period of very
gusty winds. Thus...we will not issue any Red Flag Warnings. We
will headline the FWF for gusty winds and low humidity.
Maybe as important will be the poor overnight recoveries at the
ridges and mid-slopes Sunday night and Monday night. Winds will
not likely fully decouple on the mid-slopes. Humidity values are
not likely to recover much more than 20-25% either night; some
ridges may not recover past 15%. Recoveries will improve slightly
beyond Monday...but only into the moderate range for the mid-
slopes and may not recover beyond the poor range at the ridges for
much of next week.
The trough of low pressure remains just west of the forecast area
into the middle of next week. Model simulations now show this trough
moving back east Wednesday. If this were to pan out...Wednesday
would have the potential to be the windiest day of the forecast
period. We must caution that the model simulations have been
struggling the last few days with placement and movement of the
upper-level trough...so confidence is moderate at best when
trying to pick out the day with the strongest winds with any lead
time. XX
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Blacksburg VA
857 PM EDT Sat Aug 18 2018
.SYNOPSIS...
A frontal boundary will drift south into the region overnight
into Sunday before stalling, which should keep periods of
unsettled weather in place for the rest of the weekend. The
front lifts back north as a warm front Monday ahead of another
stronger cold front that should arrive with more showers and
storms on Tuesday. High pressure will follow the front resulting
in cooler and drier weather for the middle of next week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 850 PM EDT Saturday...
Overall the area remains in a void between earlier showers that
passed to the southeast with a remnant wave aloft, and upstream
convection that continues to spill across far southwest sections
well ahead of the front. However seeing a band or two of slow
moving shallow convection along the southern Blue Ridge where
unidirectional flow off evening soundings looks to be keeping
these heavy rain producing showers in place. This also in an
area of weak moisture convergence where instability has
recovered from earlier rainfall. Latest HRRR seems to have a
good handle on this but coverage persisting another couple of
hours before becoming much more isolated after midnight.
Therefore bumped up pops to likelys where showers persist and
kept in low chances elsewhere before cutting back overnight to
a 20/30 percent regime just ahead of the actual front to the
northwest. Otherwise looking at partly to mostly cloudy
overnight with patchy fog in spots espcly where debris clouds
fade in the wake of the earlier rainfall. Lows look on track
with most dipping into the 60s except near 70 ridges and out
east.
Previous discussion as of 215 PM EDT Saturday...
A weak cold front is slowly crossing over Virginia, which is
providing prevalent cloud cover and showers moving eastward over
the Blue Ridge. The 12Z RNK sounding shows a precipitable water
value of over 1.6 inches, so there still remains a threat of
localized heavy rain. Instability continues to be weak overall
in the model soundings except for east of Danville where a hole
in cloud cover depicted in visible satellite allowed surface
heating. A few thunderstorms have just developed in this area
and will head eastward into central Virginia. The shower
activity should increase over the Piedmont this afternoon, but
this activity will decrease somewhat over southeast West
Virginia. POPs should remain rather high with high temperatures
reaching the 70s and 80s.
Any convective activity will gradually diminish in coverage
overnight with POPs slowly decreasing toward Sunday morning.
Some localized patchy fog is possible due to the wet ground and
light winds, but confidence remains high that it will be a damp
and cloudy night with low temperatures in the lower 60s to the
lower 70s. The weak cold front should sag southward toward North
Carolina on Sunday, which will keep most of the area unsettled.
Shower and thunderstorm coverage should increase again by the
afternoon due to the proximity of the cold front that will
eventually stall just south of the CWA. More breaks in cloud
cover may allow high temperatures to be a few degrees higher on
Sunday as compared to Saturday.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 300 PM EDT Saturday...
The surface frontal boundary will drift south Sunday night into
early Monday. Isolated to scattered showers and thunderstorms will
continue into Sunday evening, then taper off into the
overnight. The combination of light winds and low level humidity
will result in patchy fog late Sunday night into Monday morning.
Low temperatures Sunday night will range from around 60 degrees
in the mountains to the upper 60s in the piedmont.
A closed upper level low across the Mid-Mississippi Valley will
track northeast and reach the Great Lakes region by Monday evening.
The low center will continue to advance northeast Monday night into
Tuesday night.
On Monday, low level southwest flow will increase across the deep
south, and result in the stalled front to our south to move back
across our area as a warm front. The precipitation chances
will increase across our forecast area, with the best opportunity
in the southwest mountains Monday afternoon into Monday evening.
High temperatures Monday will vary from the lower 70s in the west to
the mid 80s in the east. Cloudy conditions with a few showers will
continue Monday night. Low temperatures Monday night will generally
range from the lower 60s in the mountains to around 70 degrees in
the east.
The upper low`s associated cold front will approach Tuesday and then
cross the area Tuesday evening into Tuesday night. Numerous showers
and thunderstorms are expected Tuesday afternoon and evening, then
convection begins to wane after midnight behind the passage of the
front. Some of the thunderstorms could be strong to severe with
locally heavy rains. Tuesday high temperatures will be cooler with
readings from around 70 degrees in the west to the mid 80s in the
east. Low temperatures Tuesday night will drop to the upper 50s to
the upper 60s.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 300 PM EDT Saturday...
A cold front will continue to travel east Wednesday, then a wave of
low pressure along the boundary will cause it stalled along the
Southeast Coast Wednesday night into Thursday. Meanwhile, cool
Canadian High pressure will build south across the Ohio Valley and
then across the Mid Atlantic by Thursday night. The High center will
slide northeast into New England for the weekend.
Isolated to scattered diurnal showers and thunderstorms will be
possible Wednesday. Drier weather is expected Thursday into
Saturday.
The ECMWF has trended weaker with evolution of the surface low
yielding a solution much closer to GFS. Eastern U.S. heights rises
expected as the cold front to stall near the southeastern and Gulf
coasts.
Cooling trend expected Wednesday into Thursday, then temperatures
moderate for the weekend.
&&
.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
As of 700 PM EDT Saturday...
Showers and isolated storms have diminished across the region
early this evening with most now lingering across far southern
sections with the passing wave and upstream in West Va near the
actual surface front. Short term models continue to show much of
this coverage also fading with loss of heating, but appears
that a shower or storm could make it into KBLF, and perhaps
KDAN where leaving in a vicinity mention through late this
evening. Otherwise looking at mainly VFR to start although cant
rule out some passing MVFR cigs below a mid deck canopy just
ahead of the front over the next few hours.
Low clouds and patchy fog will likely spread over the area
later tonight, especially around KBLF given weak upslope and
perhaps KBCB/KLWB. Although the ground will be wet from recent
rainfall, cloudy skies may keep the fog from getting dense so
fog coverage remains low confidence at this point. However given
current trends and potential for some breaks to develop, did
add in a brief period of TEMPO IFR at KLWB/KBCB, and out east
in spots where some stratus also looks possible in the wake of
the earlier heavy rain.
By Sunday morning, conditions should improve to VFR at
KROA/KLYH/KDAN, but it will take several hours more for
KBLF/KLWB/KBCB to follow suit. With the cold front sagging
toward North Carolina, its close proximity will trigger more
showers and thunderstorms during the afternoon. MVFR/IFR
conditions may occur in the stronger activity espcly across the
mountains where including a VCTS/VCSH mention for Sunday
afternoon per latest model consensus. Showers may spread east
later in the day but too iffy to include in the forecast at
KLYH/KDAN for now.
Extended Discussion...
On Monday, the stalled frontal boundary should start to lift
back north out of North Carolina. Thus, more chances of showers
and thunderstorms will continue in the afternoon espcly southern
and western sections. Additionally, the wet ground may allow
some MVFR/IFR ceilings and fog during Monday night, especially
in the mountains. The frontal boundary will move northward as a
warm front by Tuesday and keep conditions unsettled with
potential for more organized convection later Tuesday ahead of
the next stronger cold front. By Wednesday, this cold front will
push through the Mid Atlantic, and high pressure should build
overhead by Thursday. Good flying weather will return once the
cooler and drier air mass associated with this area of high
pressure arrives.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...PW
NEAR TERM...JH/PW
SHORT TERM...KK
LONG TERM...KK
AVIATION...JH/PW
Area Forecast Discussion
National Weather Service San Diego CA
129 PM PDT Sat Aug 18 2018
.SYNOPSIS...
High pressure will strengthen over the area through tonight,
continuing to dry and stabilize the atmosphere. Onshore flow and a
shallow marine layer will continue areas of night and morning low
clouds over coastal and western valley areas into the upcoming week.
Daytime temperatures will be near, to a bit above average, while
overnight lows continue between 5 and 10 degrees higher then average
due to the elevated sea surface temperatures. Monsoonal moisture may
return by the middle of next week, rekindling the chance for
mountain and desert thunderstorms.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Satellite imagery at midday showed marine stratus hanging onto
coastal San Diego County and still over a good chunk of the inner
waters. Farther to the east...patchy cumulus clouds were bubbling
over the mts. Except for the desert passes where westerly winds were
occasionally gusting 25-30 MPH, winds were mostly light.
Latest available Hires WRFEMS and HRRR runs are showing a couple of
showers popping over the mts this afternoon, so the small chance
will remain in the forecast. Otherwise, look for dry weather with
moderate to high humidity and little temp change through Monday.
Strengthening high pressure aloft over SoCal through tonight will
begin to shift back to the SE through Tue as a trough deepens over
the PacNW. The net result will be a slight warming early next week,
and then a possible return of some monsoonal moisture by midweek.
The chance of thunder returns to the mts by Tue afternoon as a
result of the shift back to SE flow aloft.
Looking at the 12Z ECMWF/GFS runs...both handle the overall pattern
similarly, and both suggest less mid-level moisture will return to
the area than this past week. However, enough is there to leave the
forecast as is. Other features of note...Both models trend 500H
lower and show increasing SW flow aloft into next weekend. This
should result in gradual cooling and decreasing thunder chances
over the mts.
&&
.AVIATION...
182030Z...Coasts/Valleys...Low clouds will redevelop and spread
inland after 01Z with bases 1000-1400 feet MSL and spread not as far
inland overnight. Local vis restrictions along inland edge of cloud
deck. Scatter out Sunday by 17Z.
Mountains/Deserts...Mostly clear through Sunday, but with some
cumulus clouds over the mountains through 01Z and again Sunday
between 19-00Z. Bases near 10000 feet MSL.
&&
.MARINE...
No hazardous marine weather is expected through Thursday.
&&
.BEACHES...
Beach Hazard Statement will continue through this evening for
elevated surf and strong rip currents. A 3-4 ft/15-16 second period
swell from 180 degrees will bring surf of 3-6 ft, with isolated sets
to 7 ft, mainly along the south facing beaches of Northern Orange
County, and strong rip currents. Surf will lower tonight through
Sunday.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through this evening for Orange County
Coastal Areas-San Diego County Coastal Areas.
PZ...NONE.
&&
$$
PUBLIC...10
AVIATION/MARINE...MM
Area Forecast Discussion
National Weather Service Shreveport LA
940 PM CDT Sat Aug 18 2018
.UPDATE...
Still dealing with some isolated showers and thunderstorms
late this evening mainly along and to the north of the I-20
Corridor of Northeast Texas and Northern Louisiana. An outflow
boundary or weak frontal boundary can be seen on radar extending
from the Sulphur River Basin of Northeast Texas to near the Ar/La
border to near Monroe, Louisiana. This boundary has pretty much
been uneventful this evening being able to initiate convection
except across Northeast Louisiana and across North Central Texas.
Looking to the west, this convection continues to develop but
shows very little push eastward. Northwesterly flow aloft is not
at pronounced as it was this time last night and is really
becoming rather neutral as upper level ridging begins to
retrograde back to the south and west into the Texas Hill Country.
For the overnight update, 00z NAM and HRRR output suggests that
renewed convection will be rather minimal overnight despite the
boundary in place so have cut pops back to slight chance variety
for all areas except Deep East Texas. Forecast min temps are in
the ballpark so did not make much in the way of changes in this
department.
Concerning pops for Sunday, with upper troughing across the
Southern Plains, it appears that our northern most zones should
experience the greater coverage of convection with only very
isolated activity expected elsewhere. This resulted in cutting
pops back to high end chance variety across our northern most
zones as latest 00z progs did not support likely to categorical
pops in these areas.
All other grids in good shape with our update out shortly...13.
&&
.PREV DISCUSSION... /issued 630 PM CDT Sat Aug 18 2018/
AVIATION...
Currently dealing with isolated to widely scattered convection
across portions of NE TX into N LA or in the vicinity of the
SHV/MLU terminals. A frontal boundary was noted across S AR into
NE TX this evening and while the short term progs suggest that
convection should be exploding along this boundary attm...just not
seeing it. Thus, this TAF forecast is a very low confidence
forecast as all available model output is contaminated.
For the package, went with VCTS at the SHV and MLU terminals for a
few hours this evening and will handle any pop up isolated
convection elsewhere with AMDs if necessary. Will need to watch
the convection across N TX through the evening hours as the HRRR
suggests it could make it into our airspace much later tonight.
Continued with the mention of VCTS at the TXK/ELD/MLU terminals
beginning late morning through the remainder of the day on Sunday
as again, this appears to be the favorable airspace given the flow
aloft and the boundary in place.
13
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 78 94 77 94 / 20 20 20 50
MLU 77 90 75 93 / 20 30 20 50
DEQ 75 87 73 89 / 20 50 70 40
TXK 76 89 76 91 / 20 30 60 50
ELD 76 89 75 89 / 20 40 30 50
TYR 79 96 77 93 / 20 20 30 40
GGG 78 96 77 94 / 20 20 30 50
LFK 77 95 77 95 / 10 10 10 40
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
13/13