Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/16/17
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
554 PM MDT Sat Jul 15 2017
.AVIATION...
00Z TAF CYCLE
Ely wave ovr west TX will set the stage for an active evening across
central and northern NM. Thunderstorm outflows from the north will
collide with outflows from the south to generate evening thunderstorms
at most terminals through 16/06Z. Storm motion will be slow and highly
variable. Brief MVFR cigs/vsbys with combined wind and rain/small
hail will result from the stronger storms. Convection will favor
northern and western areas of the state Sunday afternoon and evening.
33
&&
.PREV DISCUSSION...244 PM MDT Sat Jul 15 2017...
.SYNOPSIS...
Daily rounds of showers and thunderstorms remain on tap for the next
several days. Storm coverage should increase on Sunday and Monday
compared to today, especially over northern and western New Mexico.
Storm motion will remain quite slow, which will increase the
potential for heavy rains. A more robust monsoon plume should develop
over Arizona and far western New Mexico by mid week. Thanks to the
cloud cover and precipitation, high temperatures should be near to
just below average for the next week.
&&
.DISCUSSION...
Showers and thunderstorms started early today over the high terrain,
but have not gained much ground since then. An area of dry
air/subsidence is in place over central and east central NM in
associated with the easterly wave. This will keep showers and
thunderstorms largely at bay for the rest of the afternoon in these
areas. However, the HRRR has been consistently suggesting that
thunderstorms now developing in southeast CO will become more
organized as drop into NE NM this evening as they move around a weak
mid level low. Once these storms encounter the drier air and
subsidence associated with the easterly wave, they will likely
dissipate.
Sunday should be more active, though much of the east central and
southeast plains will be left out. Storm motion will continue to be
slow, which may result in locally heavy rains.
On Monday, the upper high that is currently centered over southern
NV will elongate eastward from NV to OK. Potentially multiple high
centers will again make storm motion slow and variable. By Tuesday,
the main high center will develop over Oklahoma. The question will
be how far westward will the high be elongated and how strong will
it be. Seems like the GFS and ECMWF are slowly coming toward a
single solution which is that the high will probably be strong
enough to steer the best monsoonal moisture into AZ and far western
NM on Tuesday, and likely on Wednesday as well. Started to trend
down PoPs across the central NM mountains both days, but if the
trend continues, PoPs will need to be adjusted down further. There`s
potential by the end of the week that the high will weaken enough
for storm coverage to begin increasing again. By early the following
week, both the GFS and ECMWF are showing the moisture plume square
over NM. Stay tuned.
34
&&
.FIRE WEATHER...
Active weather through next weekend. Still questions though as to
where the best plume of moisture sets up next week, but it`s looking
like western NM could take top honors.
Showers and thunderstorms have developed earlier today, both over
the mountains and even in parts of the eastern plains. Should be an
active evening with some storms lasting past midnight. The slow
movement of the storms could result in minor flooding of roads and
low lying areas.
The easterly wave to the south and low pressure center in CO will
head in opposite directions, both of them slowly moving away from NM
tonight and Sunday. But the high pressure anchored near Las Vegas,
NV will weaken some and PW values will come up a little, allowing
for another good round of showers and thunderstorms Sunday. The slow
moving storms could generate heavy rain producing localized flash
flooding.
The Las Vegas high pressure area will weaken a little more early
next week while the high over the central plains builds. This will
set up a favorable southeast to northwest flow of moisture from the
Gulf of Mexico, across TX and into Mexico before reaching us. The
primary plume looks like it will set up across western NM, with the
ECMWF grudgingly giving up on the farther east plume of moisture. A
couple of inverted troughs/easterly waves could add to the mix later
next week and next weekend. This all adds up to widespread
convection next week into the weekend, primarily across the western
half of the state.
Moderate or lower Haines values are forecast through next week.
Generally fair or better vent rates, except for patches of poor
rates over western and northern areas. Nighttime RH recoveries will
be good to excellent.
CHJ
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
34
Area Forecast Discussion
National Weather Service La Crosse WI
634 PM CDT Sat Jul 15 2017
.SHORT TERM...(This evening through Sunday)
Issued at 257 PM CDT Sat Jul 15 2017
At 245 PM, a cold front extended from Marquette Michigan to Sioux
Falls South Dakota. The visible satellite loop shows that much of
the clouds are located in the wake of this front. With plenty of
sunshine ahead of this front, temperatures have warmed into the
80s and they will likely warm into the 85 to 92F range by late
afternoon. Southwest winds have advected dew points to around 70F.
Looking further downstream, there will a strong possibility that
they will climb into the mid 70s in some locations. This will
result in surface based CAPES of 3000 to 4500 J/kg by late
afternoon and early evening. Looking at the RAP soundings, still
some questions on how far west the convection will develop. At
this time, feel good that the counties along the Mississippi River
and east will see scattered storms develop. Further to the west,
the cap may hold. Soundings continue to show that shear is less 30
knots or less, so the shear looks rather marginal for supercells.
However, the soundings and DCAPE (1000 to 1700 J/KG) are very
favorable for microbursts. In addition, the NCAPE is favorable for
large hail (maybe up limes or 2 inch in diameter). With limited
low level shear not seeing much for tornadic development. However,
we will have to watch out for the storms potentially interacting
with outflow boundaries from previous storms. The highest threat
for storms and severe weather will be from 4 PM to 10 PM.
For late tonight and Sunday morning, the models continue to show
some 925 and 850 mb moisture across the region. Since the current
satellite is showing this moisture in the wake of the cold front
and this has been a consistent feature, increased the cloud
percentages some.
.LONG TERM...(Sunday night through Saturday)
Issued at 257 PM CDT Sat Jul 15 2017
The models continue to show that a short wave trough will flatten
out the 500 mb ridge from Monday night through Tuesday. As this
occurs, a frontal boundary will move into the Upper Mississippi
Valley. This boundary than lingers across the area through
Thursday. As short waves embedded in the westerlies move through
the area, there will likely be several rounds of storms from
Monday night into Thursday. Still plenty of questions on where
these mesoscale convective complexes will end up and when they
will move through the region. At this time, there is some
consensus that one may move through areas north of Interstate 94
on Monday night and Tuesday morning, another one on Tuesday
afternoon and night, and then a final one Thursday as a cold
front moves through the region. There will be the potential for
severe weather and heavy rain, but with questions on the southern
extent confidence was not high enough to include this in the
forecast at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 634 PM CDT Sat Jul 15 2017
Watching a narrow line of scattered thunderstorms dropping
southward across the area this evening. Current radar trends
suggest storms should remain just east of KRST, but impact KLSE
between 15.01Z and 15.03Z. Given some lingering coverage
uncertainty, will just keep VCTS at KLSE, but may need to add a
TEMPO or predominant thunder with lower ceilings/visibility in
the next couple hours. Storms are forming along a weak cold front
and once it passes south of TAF airfields, expect a return to VFR
conditions with winds shifting to the northwest.
Still watching the potential for some MVFR stratus Sunday morning
at both KRST/KLSE, but should be short lived. Otherwise, expect
periodic VFR cumulus with light winds shifting to the northeast.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Boyne
LONG TERM...Boyne
AVIATION...Rogers
Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
850 PM CDT Sat Jul 15 2017
.UPDATE...
Issued at 850 PM CDT Sat Jul 15 2017
Cold front has moved well south into central Wisconsin as of mid
evening, with cooler and drier air filtering into the Duluth CWA
as high pressure builds in from the north. Overall, we expect a
fairly quiet weather night.
However, GOES-16 imagery and surface obs indicate a fairly well-
organized secondary northeasterly surge moving southwest-ward
near Isle Royale and the Minnesota Arrowhead, with a well-defined
wind shift/cloud line, and Rock of Ages is now gusting to 25 knots
from the northeast. The previous forecast and hi-res guidance
hinted at this feature earlier, and it appears that guidance was
on to something. Confidence in any meaningful precip with this as
it reaches the south shore later tonight is very low, but it
should be sufficient for a period of locally stronger winds,
cooler temps, stratus clouds and perhaps some drizzle in the
primary upslope areas prone to northeast flow. We have updated the
forecast to reflect these trends, and also increase the coverage
of patchy fog in many areas during the overnight hours.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 330 PM CDT Sat Jul 15 2017
At 330 PM, skies were partly to mostly sunny across the Northland.
Temperatures ranged from 86 at McGregor, to 73 in Crane Lake,
where there was a bit more extensive cloud cover. Winds had
generally shifted to the north/northwest across the entire CWA.
The focus for tonight will be the potential for a few showers and
thunderstorms, along with the potential for some late night
stratus/rain showers off Lake Superior.
Quite unstable air across northwest Wisconsin this afternoon. CIN
has been decreasing across that area, although there was still a
bit of a cap on forecast soundings across that area. These
forecast soundings indicate there will exist a small window where
storms could develop late this afternoon or early evening,
although the threat will quickly shift south of the CWA with time.
The CU field elsewhere across the CWA has not shown much growth at
all, but would not be surprised to see a few showers or a storm
across the Minnesota Arrowhead this afternoon. Still, the best
chance for some development would be south of a line from Hayward
to Ironwood. Dewpoints in this area are in the lower 70s as of 3
PM. The rest of the Northland should see skies generally clear
overnight. The HRRR is consistent in trying to bring some stratus
and perhaps some spotty rain showers or drizzle to the areas
surrounding Lake Superior overnight, first along the south shore,
and then across the Twin Ports and portions of the North Shore.
Any clouds/showers that do develop overnight should gradually
break up on Sunday, as high pressure brings sunshine to the CWA.
Lows tonight will range from the 40s in the north to the 50s to
around 60 south. Highs on Sunday will range from the 60s to lower
70s near Lake Superior, to the 70s inland.
.LONG TERM...(Sunday night through Saturday)
Issued at 330 PM CDT Sat Jul 15 2017
A ridge of high pressure will build southeastward into the central
Great Lakes Sunday night, while a trough lifts into the central
Canada. At the surface, high pressure will slide from the Upper
Midwest into the central Great Lakes. Behind the surface high, a
cold front will move into the northern Plains and northwest
Minnesota. On Monday the front will slide southeastward through much
of northern Minnesota. This will bring increasing chances of showers
and thunderstorms late Sunday night through Monday. It will be humid
with mid 60s to near 70 degree dewpoints advecting into the region
ahead of the front due to southerly flow. In addition, there will be
1500-3000 J/kg of MLCAPE, 0-6 km bulk shear increasing to 25 to 40
kts, and PWATS of 1.5 to 2.0 inches per the GFS/NAM/ECWMF. Based on
these parameters combined with forcing from the front, strong to
severe storms will be possible as highlighted in the current SPC Day
3 Outlook. With PWAT values near the 90th percentile for this time
of year, heavy rainfall will also be a concern. Highs on Monday will
range from the mid 70s along the Lake Superior shoreline, to the
upper 80s in the Brainerd Lakes region.
The cold front will slowly continue sliding southeastward through
the Northland Monday night and Tuesday. Aloft, another shortwave
will be moving through bringing continued shower and thunderstorm
chances. Cannot completely rule out strong to severe storms on
Tuesday especially if the latest GFS pans out with MLCAPE of 1500-
2500 J/kg with 0-6 km bulk shear of 40-50 kts. Think these
instability values may be a bit overdone as cloud cover from the
ongoing/previous days convection should inhibit the amount of
daytime heating. By Wednesday, the GFS stalls the cold front across
southern portions of the CWA, while the ECMWF/CMC are more
progressive and have already moved the front through. Uncertain at
this point how things will evolve, but opted in continuing
shower/storm chances as another shortwave will be moving through.
High pressure will build into the region Thursday/Friday as an 850
hPa ridge axis moves northeastward from the northern Plains into the
Upper Midwest. Late in the week and heading into the weekend, a
trough will move into the Upper Midwest from central Canada bringing
more chances of showers and storms. Expect seasonable highs for
Tuesday through Saturday with readings in the 70s and low 80s. Lows
range from the 50s to low 60s Tuesday night through Friday night.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 647 PM CDT Sat Jul 15 2017
Cold front has cleared all of the TAF sites as of 00z, with
north/northwest winds and diminishing fair weather cumulus field.
VFR conditions are expected throughout the period, with the
only risk for some MVFR conditions being near the south/southwest
shore of Lake Superior later tonight/Sunday morning as winds
become northeast. Scattered to broken cumulus should develop in
most areas again Sunday, but any ceilings are expected to be well
above MVFR thresholds.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 57 69 48 78 / 10 10 0 20
INL 48 77 54 79 / 0 0 10 50
BRD 57 77 58 87 / 0 0 0 20
HYR 53 74 50 82 / 10 0 0 10
ASX 55 69 48 82 / 10 0 0 10
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
UPDATE...Miller
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
953 PM CDT Sat Jul 15 2017
.UPDATE...
The diurnal activity across North and Central Texas has come to an
end, but showers and thunderstorms remain upstream. Some of these
cells may slip into northern portions of the CWA into the early
morning hours.
The complex in western Oklahoma will likely dissipate as the
impulse responsible for its initiation outruns it. However, this
disturbance may result in renewed development across North and
Central Texas early Sunday morning. The coverage should be
isolated at best with lightning the primary concern.
25
&&
.AVIATION... /Issued 734 PM CDT Sat Jul 15 2017/
Showers and thunderstorms that were scattered across North Texas
this afternoon had dissipated as of 00Z. The remainder of the
night should be quiet with VFR and scattered to broken high
clouds.
We are watching the convection currently across western
Oklahoma. This activity should weaken as it approaches the
Metroplex TAF sites overnight as per HRRR and TTU WRF solutions.
There will be an outside chance of a shower across the Metroplex
TAF sites toward sunrise Sunday, but impacts should be minimal.
Sunday will be VFR with scattered daytime CU and a few afternoon
showers and isolated storms in the late afternoon.
An east to southeast will prevail at speeds generally less than 10
knots.
79
&&
.DISCUSSION... /Issued 345 PM CDT Sat Jul 15 2017/
Showers and thunderstorms have been most numerous this afternoon
across Central Texas and the southeastern part of North Texas.
This is the area that was south of this morning`s outflow
boundary. A few strong storms have produced wind gusts in excess
of 40 mph. Rainfall rates are high as you would expect with nearly
2 inch Precipitable Water Values. Fortunately the storms are
moving at around 15 mph but some training may still result in
localized flooding issues. Other thunderstorms occurred west of a
Hillsboro to Jacksboro line in the untapped air there and also
across areas east of a Sherman to Athens line where the remnants
of some of this morning`s activity refused to die. There was quite
a variation in temperatures with mid to upper 80s across areas
north and northeast of the Metroplex and mid to upper 90s across
parts of Central Texas before the storms hit. A weak shortwave
will continue to move around the eastern periphery the upper
level high centered to our northwest but with the loss of daytime
heating, expect most of the showers and thunderstorms to decrease
in areal coverage toward sunset. Cannot completely rule out
additional showers and thunderstorms overnight, so have left some
20 percent PoPs for the late evening through the overnight hours
area wide. Lows will be in the 70s.
With the upper ridge remaining to our northwest on Sunday, we
will keep at least a slight chance of showers and thunderstorms
with the best chances (30 percent PoPs) being southeast of a
Goldthwaite to Waxahachie to Paris line. Highs will be in the 90s
area wide with heat index values reaching 98 to 107 degrees.
The ridge will build eastward across Kansas and Oklahoma during
the early part of the week and the strengthen its grip on North
and Central Texas during the middle to late part of next week.
This will result hot weather with chances of showers and
thunderstorms shifting southward. We will be near heat advisory
criteria especially along and east of the I-35 corridor.
58
&&
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 77 96 77 97 77 / 20 20 10 20 10
Waco 74 97 75 96 75 / 20 30 20 30 20
Paris 75 94 73 93 73 / 20 20 10 10 10
Denton 75 95 74 95 75 / 20 20 10 10 10
McKinney 74 95 74 95 75 / 20 20 10 10 10
Dallas 78 97 78 97 77 / 20 20 10 20 10
Terrell 75 95 74 95 75 / 20 30 10 20 10
Corsicana 75 96 74 95 74 / 20 30 20 30 20
Temple 73 96 74 96 74 / 20 40 20 30 30
Mineral Wells 75 95 73 96 73 / 20 20 10 10 10
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
25/79
Area Forecast Discussion
National Weather Service Goodland KS
826 PM MDT Sat Jul 15 2017
.UPDATE...
Issued at 821 PM MDT Sat Jul 15 2017
Storm intensity has transitioned to light to moderate rain.
Latest data indicates the best chance for rainfall tonight will be
over mainly Cheyenne County CO and western parts of Wallace and
Greeley counties. For this part of the forecast area lift from the
closed low overhead will persist through the night, which should
result in continued rain activity. Early in the morning lift will
reach a minimum then increase as temperatures warm.
&&
.SHORT TERM...(This afternoon through Sunday)
Issued at 202 PM MDT Sat Jul 15 2017
Mid level upper low continues to linger over eastern Colorado,
with deep plume of moisture overriding our CWA. Thunderstorm
coverage has continued to increase early this afternoon, and there
has been one report of severe hail near the NE state line with
one of the stronger cells.
High resolution guidance continues to favor increasing coverage
through the rest of the afternoon then decreasing coverage near
sunset. With a tendency for slow moving clusters along narrow
regions of mid level vorticity it is hard to zero in on overall
coverage, so I have continued to hedge towards high "chance". I
could see increasing coverage for some locations, but I will wait
in until we have a better handle on short range trends. With mid
level circulation and moist plume lingering I would expect at
least a few showers or weaker thunderstorms overnight tonight and
Sunday morning. Coverage should increase midday Sunday, with
increase in lapse rates due to daytime heating and models support
this trend.
Regarding severe potential: Meso analysis from RAP indicates axis
of 2500-3000 J/KG ML CAPE is in place over the northeast 2/3 of
our CWA, with very weak shear and slow 0-6km winds. PWATs are
shown to be anomalously high with values in excess of 1.5" across
our KS counties. Considering antecedent conditions isolated severe
hail and localized flash flooding would be the main concerns.
RAP/NAM show downward trend in CAPE, and a decreased severe threat
after sunset. We could see a repeat Sunday afternoon, with
similar conditions over at least part of our CWA.
.LONG TERM...(Sunday night through Saturday)
Issued at 202 PM MDT Sat Jul 15 2017
Sunday night-Tuesday: Weak closed upper level low meanders across
the area through Monday morning. This, combined with surface
troughing and abundant 700mb moisture, will bring chances of rain
and thunderstorms to southeastern portions of the CWA. Will carry
slight chances of storms on Monday and Tuesday afternoons due to
residual moisture and troughing. Temperatures will warm through the
period.
Wednesday-Thursday: Upper level ridging dominates the weather
through the period. Today`s 12Z runs of the GFS and ECMWF are in
better agreement on temps than yesterday`s. Temperatures will be
well above normal with some areas at or above 100 degrees for highs
both days.
Friday-Saturday: Models are not in good agreement for this period,
so have low confidence in this portion of the forecast. Ridge
progresses off to the east, putting the area in more of a zonal
flow pattern aloft. Could see some showers/storms by Saturday.
Temperatures appear to remain above normal.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 517 PM MDT Sat Jul 15 2017
VFR conditions expected for the TAFs. Main impact will be the rain
activity at KGLD in the first couple hours of the TAF. Latest
radar shows an area of rain just south of the site. If the rain
moves overhead, will end in a few hours. Last 20 minutes of radar
data show the rain moving very little to the north, which gives
concern that it may not move over KGLD.
KMCK will remain north of the storm activity.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...JTL
SHORT TERM...DR
LONG TERM...SME
AVIATION...JTL
Area Forecast Discussion
National Weather Service Green Bay WI
1045 PM CDT Sat Jul 15 2017
Updated aviation portion for 06Z TAF issuance
.SYNOPSIS...
Issued at 229 PM CDT Sat Jul 15 2017
Scattered thunderstorms through this evening, then a couple days
of quiet weather. Humid conditions and more thunderstorms will
return mid-week.
A band of westerlies was located across northeast Canada, flowing
around a deep upper low over northern Hudson Bay. Farther south,
another fairly amplified band of westerlies stretched across
southern Canada and the northern CONUS. Within that branch of the
flow, there were troughs along the West Coast and over New
England, with a ridge over the Intermountain West. That branch of
the flow will amplify a bit more during the next 24 hours and then
begin to deamplify as the main features within it become
progressive. There will also be some consolidation of the flow
across NOAM, with much of Canada becoming dominated by flow around
the Hudson Bay upper low. Meanwhile, a lower amplitude flow is
forecast to persists across the CONUS from mid-week into the
upcoming weekend and beyond. The medium range models have tried
that before in the past few weeks, only to have the western
ridge/eastern trough pattern reappear. We`ll see what happens this
time.
Air masses moving across the region favor temperatures falling
off to a little below normal the next couple days, then warming
back to near or above normal for the rest of the forecast period.
But temperatures are likely to be held back on days with
widespread clouds and convection. At least a couple more humid
days are likely mid-week. The area will spend enough time near the
main frontal zone lingering near the southern edge of the
westerlies to result in above normal precipitation amounts for the
period. Totals could end up being quite heavy, depending on the
movement of individual convective systems.
&&
.SHORT TERM...Tonight and Sunday
Issued at 229 PM CDT Sat Jul 15 2017
The latest RAP analysis and satellite/radar imagery show a cold
front stretching from just northwest of Minneapolis to northwest WI
early this afternoon. 12z soundings from GRB and MSP indicate a
rather stout cap in place across the region, beneath an elevated
mixed layer comprised of some very dry air. Will probably take until
after 21z for convection to break through the cap, which the
mesomodels support as well. Once developed, ml capes upwards of
2000 j/kg and 0-6km bulk shear of 30-35 kts will be supportive of
severe thunderstorms capable of producing damaging straight line
winds and large hail. The storms should then proceed southeast from
north-central WI late this afternoon, into central and northeast WI
by early this evening. Besides severe weather potential, forecast
also centers on gusty north winds.
Tonight...The cold front will continue to move southeast across
central and northeast WI during the evening before exiting around
midnight. Instability and shear will remain supportive for severe
thunderstorms until the front exits, including damaging winds and
large hail. Behind the front, north winds will ramp up and will
likely become gusty along the Bay and Lake. Scattered to broken
cloud cover from north of Lake Superior is expected to reach into
northern WI late tonight, though not sure how far south these clouds
will make it. Did increase sky cover some though. After a warm and
stormy evening, temps to fall into the mid 50s north to mid 60s
south.
Sunday...High pressure will build in from the north, with winds
turning to the northeast. With gusts of 20-25 kts and waves
approaching 4ft, will issue a small craft advisory, starting late
Saturday night. Should have some scattered to broken clouds through
late morning/midday before dry air mixes out the clouds. Temps will
be cooler, with highs ranging from the low to mid 70s.
.LONG TERM...Sunday Night Through Saturday
Issued at 229 PM CDT Sat Jul 15 2017
High pressure across the area will create light winds and mostly
clear skies, so temperatures should drop off considerably Sunday
night. Patchy fog could also develop, but that will depend partly
on the coverage and rainfall amounts from today`s late
afternoon/evening storms.
Not surprisingly given the flattening of the upper flow, models
started to offer differing ideas on how quickly convection in the
return flow around the high would move into the area. Stayed with
the broad-based blend of guidance for PoPs, and that resulted in
mainly chance PoPs Tuesday through Thursday. Would like to say
we`ll be able to add significant detail to those in coming days,
but this may wind up being another one of those situations where
it`s tough to gauge convective evolution more than 12 hours in
advance. The overall pattern looks favorable for heavy/excessive
rainfall somewhere near or in the forecast area. Will reflect
this with more aggressive wording in the HWO. A severe risk could
also evolve at some point as well.
Even the relatively flat flow on the medium range guidance tilts
northwest just enough to drive the main frontal zone south of the
area by late in the week, though they also show the return flow
developing pretty quickly. There will probably be a dry day in
there somewhere--most likely Friday.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1045 PM CDT Sat Jul 15 2017
Showers and thunderstorms have ended behind a departing cold
front. In its wake mostly clear skies and VFR conditions are
expected through Sunday. Although the amount of rain the area
received this evening would suggest patchy fog, MOS guidance does
not generate fog as it keeps winds up with falling dew points.
Therefore will continue to leave fog out of the TAFs with this
issuance but would not be surprised to see some form given the
rainfall.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement from 7 AM CDT Sunday through Sunday
evening for WIZ050.
&&
$$
SYNOPSIS.......Skowronski
SHORT TERM.....MPC
LONG TERM......Skowronski
AVIATION.......Kurimski
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1044 PM EDT Sat Jul 15 2017
.SYNOPSIS...
Hot and humid conditions will persist through the weekend, with
scattered to numerous afternoon and evening thunderstorms each day.
A cold front will move into the region from the northwest and stall
near the area through Sunday. Another cold front will approach on
Monday and move southeast of the area on Tuesday, with drier and
warmer conditions arriving by the middle of next week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 1030 PM EDT: Another quick update mainly to PoPs and Temps to
reflect latest trends. Am seeing a few showers popping up across the
southern Upper Savannah Valley. There is not much CAPE left to work
with, but will bump up PoP for the next couple hours there.
Elsewhere, the CAMs still hint at spotty redevelopment overnight.
The last few runs of the HRRR have been consistent in showers
developing over the NW NC piedmont after midnight. Not sure what it
is keying on. But the front is in the area, and there is still
500-1000 J/kg of MUCAPE with low LFC heights. So I will keep a
slight CHC PoP in for most of the area thru the overnight. Not
expecting too much additional convection. Otherwise, expect a mix of
mid and high clouds with temps near to slightly above normal.
Convection pick up at least across southern zones on Sunday. Some of
the hires models want to develop some showery activity across the
northern tier as well so have kept pops a little higher, but these
may need to be pulled back down with later forecasts. Temperatures
will be improving through the period, with highs today near seasonal
normals, lows tonight just slightly above and highs tomorrow
actually a couple of degrees below.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 130 PM EDT Saturday: A shortwave embedded in upper longwave
troughing will cross the area Sunday night as a surface front
settles over the forecast area. The front will wash out on Monday as
heights aloft fall and another potent shortwave rounds the trough
base, so widespread showers and thunderstorms are anticipated once
again on Monday. Another front will descend from the northwest on
Monday night and will stall near the forecast area Tuesday,
providing a focus for enhanced diurnal convection in the afternoon.
Mid-level dry air makes an entrance Monday and Tuesday, and with
respectable instability both days, some type of wet microburst
threat is possible. Temperatures will be near climo.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 100 PM EDT Saturday: The medium range begins Tuesday night
immediately post-frontal passage with a few lingering showers and
thunderstorms. Upper troughing lifts by Wednesday, though there is
some model disagreement in just how far the front is able to
progress as it washes out on Wednesday. Strong upper ridging builds
over the central Plains on Wednesday to exert some influence on the
southeast, though, so maximum temperatures were increased and
"silent 10" pops remain. The extent to which drier air will be able
to work in as the ridge continues to build Thursday and Friday is
also uncertain, but enough moisture lingers in the global model
solutions that slight chance pops were maintained both afternoons. A
back door front dips down from the northeast as upper heights fall
again on Saturday, bringing pops close to climo back into the
forecast. Maximum and minimum temperatures during the middle and end
of next week will be above climo through the period, though the
extent is uncertain due to model inconsistencies in handling the
sprawling high over the central Plains.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
At KCLT and Elsewhere: Convection got an early start and is now
south and east of the area as of 00z TAF issuance. Some debris
cloudiness and a few spotty light showers may linger thru the
evening, but overall VFR conditions are expected heading into the
overnight. But after around midnight, expect valley fog and stratus
to develop in the mountain valleys. With a front stalled over the
piedmont, guidance shows more mid-level moisture and not hitting fog
or stratus too hard. However, if skies manage to clear and winds
remain light, could see some areas of fog and/or stratus over
portions of the piedmont. For now, will only put in some MVFR vsby
late tonight at KAND/KGSP/KHKY. For Sunday, the front will remain
close to the Piedmont sites, and guidance is in good agreement on
enough instability for mountain-top convection as well. So will put
PROB30 groups in all TAF sites for Sunday afternoon. Winds will be
light, favoring a N/NW direction tonight, then switching back to
S/SW by early afternoon.
Outlook: Scattered to numerous afternoon and evening thunderstorms
are expected both Monday and Tuesday across the area, with higher
coverage in the mountains. Morning fog development can be expected
in the mountain valleys and in areas that receive rainfall the
previous afternoon/evening. Drier air will limit convective coverage
to more isolated for Wednesday into late week.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 100% High 98% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 95% Med 73% High 97% High 100%
KHKY High 100% High 95% High 100% High 100%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 100% High 90% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...Carroll
NEAR TERM...ARK/TDP
SHORT TERM...Carroll
LONG TERM...Carroll
AVIATION...ARK
Area Forecast Discussion
National Weather Service Huntsville AL
626 PM CDT Sat Jul 15 2017
.UPDATE...
For 00Z TAFS.
&&
.NEAR TERM...(Tonight)
Issued at 626 PM CDT Sat Jul 15 2017
Went ahead and made some updates to the forecast for the rest of the
evening, mostly to account for diminishing radar trends and quick
cooling of the locations that have received heavy rainfall. At 21z,
WPC analyzed a stationary front sitting west to east across our
middle TN counties and it is very difficult to identify where that
boundary is now or if it`s even there. Winds are light and variable
and dew points aren`t falling much to the north and the only tip
would be a theta-E boundary that`s been moving through the area and
is now to the south.
Current LAPS soundings show cooling at the surface thanks to the
rain and outflow boundaries and has quickly weakened the ongoing
storms with little to no lightning ongoing across the area. The
storms that were impacting the area earlier have diminished into
light to moderate rainfall and mainly impacting areas around
Huntsville and farther south. Looking at the latest HRRR runs as well
as the deep dry air moving in from the north, evident on the
multiple GOES-16 water vapor bands, it looks like we should stay
mostly dry overnight after this batch weakens and moves off to the
south. However, given the questionable boundary that will linger and
PW values staying around 1.5 inches overnight, will keep the mention
of isolated storms. Granted, I am not overly confident we`ll get any
rumbles overnight, probably just isolated showers.
The one major change to the forecast was the addition of fog
overnight. Dew points won`t drop very fast overnight and we could see
some clearing skies by midnight. The areas that received rainfall
will likely see patchy fog at least and will monitor to see if we
need to increase the coverage.
.SHORT TERM...(Sunday through Monday)
Issued at 309 PM CDT Sat Jul 15 2017
Sunday will be more typical of mid-July with scattered showers and
storms, perhaps favoring the southeast part of the area where better
moisture will linger. However, while the threat of heavy rain
abates, the increasing mid-level dry air and steep lapse rates could
increase the threat for strong microbursts. Monday will bring
another weak shortwave into the area, but it will do more to bring
deeper dry air into the area than increase precipitation coverage.
All in all, PoPs for the next two days will be much more typical for
mid-July than they are today: generally in the 20-30% range and with
slightly higher values to the southeast where more persistent
moisture exists. High temperatures will decrease slightly, back to
seasonal norms for July, while low temperatures will stay more or
less persistence.
.LONG TERM...(Monday night through Friday)
Issued at 309 PM CDT Sat Jul 15 2017
A shortwave will dive from the Great Lakes down into the
Appalachians on Tuesday as a ridge anchored over the central U.S
begins to expand into the Southeast. At the sfc, a weak front will be
south of the area with high pressure building in from the north. A
few showers and thunderstorms are possible across the TN Valley
Tuesday afternoon with highs in the upper 80s to lower 90s. Some
drier air filters into the region Tuesday/Wed, but a few
showers/storms are still possible Wed afternoon with temps in the
upper 80s/lower 90s and heat index values reaching the mid/upper 90s.
The building ridge will increase temps through the week reaching the
low/mid 90s by Friday. With southerly flow, moisture returns towards
the end of the week. This will increase the heat index values,
reaching 100 degrees or slightly above by Friday. Look for isolated
to scattered showers/storms Thurs and Friday afternoon as the
shortwave cuts off then retrogrades westward.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 626 PM CDT Sat Jul 15 2017
Showers/storms are almost over for the terminals and will keep both
terminals dry for the TAFs. An isolated shower or storm is possible
overnight but confidence is not high enough to include in the TAFS.
CIGS may rise slightly in the next few hours but lower clouds may
move in by morning. In addition, fog is possible and have added a
TEMPO group for 3SM and BKN020. CIGS should rise after sunrise with
sct/bkn afternoon clouds expected on Sunday. Winds will remain light
and variable through the TAF period.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...LN/BCC
SHORT TERM...BCC
LONG TERM...JMS
AVIATION...LN
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Lubbock TX
633 PM CDT Sat Jul 15 2017
.AVIATION...
VFR and light winds. Very isolated showers and occasional TS will
dwindle after sunset, before returning Sun afternoon with a bit
more coverage near an easterly wind shift. This boundary will push
through CDS in a few hours, but slow or stall as it reaches LBB
and PVW on Sunday. Later TAFs may entertain TS mention on Sun if
prospects for TS improve.
&&
.PREV DISCUSSION... /issued 252 PM CDT Sat Jul 15 2017/
DISCUSSION...
Isolated convection has started to develop across the
northwestern Permian Basin/southeastern NM and the southern South
Plains along the edge of the caprock. The main sources of lift are
weak surface boundaries. The RAP and the HRRR have been the only
models hinting at these isolated showers/thunderstorms. These reason
seems to be that they appear to be handling the mid and upper level
dry air better than the larger scale models. WV shows a pocket of
dry air across the central TX Panhandle into western OK. Models such
as the GFS and NAM have this dry air pushing south and westward over
the FA by this afternoon. WV actually shows this area of dry air to
be shrinking as it is being overtaken by moisture associated with a
shortwave over northern Mexico as well as gulf moisture. Showers
and thunderstorms that develop this afternoon and evening should
dissipate by midnight. The one exception may be convection
associated with the cold front across our northeastern zones.
Another area of possible precip development is across our
northeastern zones close to the surface front which is across
central OK/northern TX Panhandle. Convection has already begun to
develop along the front and is slowly pushing southward. Better rain
chances will come tomorrow as deep layer moisture continues to
improve. As has been the norm lately, upper level lift, though not
nill, will be mostly lacking and any development will be dependent
upon surface boundaries left over from convection that happens today
as well as the position of the surface front. The NAM forms
convection during the afternoon along the front as it pushes
westward from the caprock escarpment. The GFS follows suit but holds
off until after 00Z tomorrow evening. Pops will only be increased
slightly as there is still uncertainty over timing and coverage.
Monday still looks to be dry as the upper high takes back its hold
on the region. Questions remain on whether the high will continue to
block rain chances into mid and late week or if it will weaken and
push eastward. The ECMWF and GFS continue to differ on the evolution
of the upper high by mid week, but the GFS is slowly changing its
portrayal of how the high will evolve next week and, while not fully
like the ECMWF, it is more of a match than it has been in recent
days. The GFS keeps most of the upper high overhead despite an
eastward shift. The ECMWF breaks the ridge down as it brings a few
short waves southward from Canada to the southeast helping little by
little to erode the ridge. Pops through next week will still remain
below mention for most areas as there is still some uncertainty in
the forecast, but they will be nudged just a bit higher towards the
mentionable mark.
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
93
Area Forecast Discussion
National Weather Service Omaha/Valley NE
612 PM CDT Sat Jul 15 2017
.SHORT TERM...(Tonight through Tuesday)
Issued at 305 PM CDT Sat Jul 15 2017
Temperatures will provide the main forecast challenges into Monday
then will have to look at precipitation chances for our area.
Pattern is still very similar to 24 hours ago, with a large mid
and upper tropospheric ridge over the Rockies extending out into
the western Plains. Closed low at 500 mb over CO shows up quite
nicely in water vapor imagery. Some thunderstorms noted at mid
afternoon over parts of eastern CO, western KS and southwest NE.
700 mb temperatures in this area were a little cooler (from KDEN
to KLBF) compared to areas farther to the west, north and east.
At the surface, synoptic scale cold front was pushing south toward
our area. There was another weak boundary that extended from the
southwest corner of SD into north central NE. ESRL HRRR keeps most
of the activity out over western and parts of central NE into at
least early Sunday afternoon, so will keep the forecast dry for
now. Look for lows tonight in the upper 60s to around 70.
On Sunday, that weak front should start to lift north, but it
doesn`t look like convergence will be strong enough to generate
any precipitation. Look for highs in the lower and mid 90s. A low
pressure system and cold front should move into the western
Dakotas Sunday night, with southerly low level in our area
increasing a bit. The result will be lows in the upper 60s and
lower 70s. Surface pressure gradient and low level winds will be
increasing a bit more on Monday, and the closed low that is to our
west today should be moving slowly east but as more of an open
wave. The front could stay to our south, but the combination of a
few different factors may be enough to trigger some showers and
thunderstorms in our area, especially by Monday night. The GFS in
general seems to have been too aggressive with development of
precipitation in our area Monday/Tuesday, but will keep at least
some low POPs going. Airmass does not change a lot, so will keep
highs Monday (and Tuesday) in the lower and mid 90s.
.LONG TERM...(Tuesday night through Saturday)
Issued at 305 PM CDT Sat Jul 15 2017
At the start of this period, a 500 mb ridge should stretch from UT
and CO eastward into MO and AR. There will be a weak Rex block off
the coast of western Canada with the southern branch of polar
jetstream from the Pacific northwest across the northern Plains
and into Ontario Canada. We will probably be on the northern
edge of a hot airmass centered to our south across KS and OK. Some
intermittent low thunderstorm chances are expected, mainly Tuesday
night and then Thursday night into Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 610 PM CDT Sat Jul 15 2017
VFR conditions are forecast through Sunday evening. Mainly
scattered mid and high clouds are expected overnight, then maybe
scattered cumulus between FL050 and FL070 Sunday afternoon.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
SHORT TERM...Miller
LONG TERM...Miller
AVIATION...Dergan
Area Forecast Discussion
National Weather Service Reno NV
155 PM PDT Sat Jul 15 2017
.SYNOPSIS...
Isolated thunderstorms remain possible through the weekend. The best
chances are each afternoon into early evening over the eastern
Sierra into central Nevada, however a couple storms could occur
overnight tonight into Reno and Tahoe areas. Low pressure
approaching the west coast will increase winds Monday and Tuesday,
leading to critical conditions for rapid fire spread. Decreased
winds with hot temperatures expected for the balance of next week.
&&
.Short and Long Term Discussion...
Rather typical variety of summer weather for next 7-10 days.
Here`re the highlights:
* Isolated Weekend Storms: Trend for decreased storm coverage
today and Sunday remains intact. GOES-16 stability fields really
highlight dry and more stable airmass today over W Nevada and
much of the Sierra. Exceptions are Mono-Mineral Co, far NE Cal,
and Nevada east of Hwy 95 where airmass is more favorable for
storm development. Similar scenario for Sunday though guidance
is showing even less storm coverage for these areas with more
stabilized airmass.
* Overnight Storms: Guidance depicting a wave lifting from CA up
into Great Basin tonight. Coupled with instability and moisture
aloft, HRRR develops a few showers and storms around Reno/Tahoe
late this evening into pre-dawn Sunday morning. NCAR 3km
ensemble shows something similar but further north. Certainly a
concern for fire interests. Predictability of these elevated
storm scenarios is typically low - but presence of showers
offshore of central California (upstream airmass) does increase
my confidence of seeing some cells in our region tonight.
* Increased Winds Monday-Tuesday: Low pressure off the Pac NW
will drive an increased southwest flow aloft over our region,
leading to breezy afternoon-evening winds. 700mb flow nearing 30
kts. While not impactful for travel, this will lead to a
critical fire weather scenario. See the fire discussion below
for more.
* Summer Doldrums Follow: Ridging over the Great Basin resurges
mid to late next week, leading to continued hot temperatures but
a return to more typical zephyr type winds. Daily thunderstorm
potential through next week looks to be mainly confined to
central and southern Nevada and the eastern Sierra south of
Tioga Pass.
* Monsoon Surge Week of 7/23: ECMWF and GEFS ensemble guidance
both showing the heat ridge over SW CONUS fracturing some late
next weekend into the following week. This could allow a surge
of monsoon moisture to work north into the Great Basin,
especially if GEFS PW simulations pan out. This could result in
a substantial increase in storm coverage in our region starting
as early as next weekend. Predictability is marginal but it`s a
decent signal this far out.
-Chris
&&
.AVIATION...
* Typical afternoon and evening westerly winds today and Sunday,
so the primarily aviation concern is from isolated storms. Based
on recent simulations including HRRR and NCAR 3km ensemble, am
not overly impressed with storm coverage each afternoon. Roughly
10- 20%. Most of that would be over eastern Sierra (MMH) into
central Nevada (east of NFL).
* Potential for some isolated cells overnight tonight near
TVL/RNO as shortwave aloft passes by, but predictability of
coverage too low at this time to include in TAFs.
* Increased west/southwest winds Monday and Tuesday likely to
yield more turbulence and some localized wind shear. Gusts on
the order of 30 kts possible including RNO each afternoon and
evening.
-Chris
&&
.FIRE WEATHER...
There could be a few stray thunderstorms, about a 5-10% chance,
overnight tonight as a weak wave moves through the region. As
such, a rare new fire start is possible should any thunderstorms
occur. Mid slopes and ridges could see breezy conditions from any
passing showers with lighter outflows for valley locations.
Otherwise, thunderstorms will be more diurnally driven mainly
south of Highway 50 Sunday afternoon.
Monday continues to be the focus for critical fire weather
conditions. Increasing winds will combine with a significant dry
slot resulting in a marked increase in fire concerns; the Fire
Weather Watch for extreme northeastern California and western
Nevada has been upgraded to a Red Flag Warning. Generally, gusts
will be 30-40 mph region-wide and humidity percentages will be in
the mid single digits to low teens. Lightning holdovers could
start new fires, and these winds will be able to drive fire very
rapidly through area grasses and shrubs.
Concerns are increasing for Tuesday as model winds continue to
increase. Wind gusts are currently expected to be around 30 mph with
similarly low humidty as to Monday. A Fire Weather Watch has been
issued as a result. Boyd
&&
.REV Watches/Warnings/Advisories...
NV...Red Flag Warning from noon to 8 PM PDT Monday NVZ450-453-458-459.
Fire Weather Watch from Tuesday afternoon through Tuesday
evening NVZ450-453-458-459.
CA...Red Flag Warning from noon to 8 PM PDT Monday CAZ270-271-278.
Fire Weather Watch from Tuesday afternoon through Tuesday
evening CAZ270-271-278.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Blacksburg VA
904 PM EDT Sat Jul 15 2017
.SYNOPSIS...
Weak high pressure will build east across the area overnight
into Sunday. Showers and storms quickly return to the forecast
Monday into Tuesday as disturbances move through the area from
northwest to southeast. A more summer like pattern returns to
the region by Wednesday into Thursday.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 850 PM EDT Saturday...
Surface front has slipped south of the region this evening while
the actual dewpoint boundary lingers near the VA/NC border. This
seen well via evening soundings with the RNK raob very dry/capped
aloft with PWATS half than those seen from GSO where moisture
through the column remains deeper. However best support and
lingering instability has continued to dip to the south of the
region this evening, with a dry pocket along/west of the Blue
Ridge per better residual mixing of dry air from aloft this
afternoon. Latest short term guidance including the HRRR
continues to hint at trying to develop some added showers far
south under weak evening convergence and perhaps old outflow
but iffy. Therefore may leave in an isolated shower mention over
the next few hours before fading to mainly clear skies with
some patchy fog around late. Should be a bit more comfortable
tonight across central/western sections where dewpoints have
dropped enough to allow lows to slide back into the low/mid 60s,
with even a few 50s possible deep valleys across the northwest.
Will still be muggy over southern sections, with lows closer to
70, given lack of much push of weak dry advection overnight.
Previous discussion as of 230 PM EDT Saturday...
A cold front was positioned just to the south of the forecast area.
Isolated to scattered showers along this front will just barely clip
the far southern sections of the area heading into the evening
hours. Overnight, skies will trend to mostly clear across the north,
and partly cloud south. Light winds, limited cloud cover, and a
surface moisture will allow for the development of radiation fog
across mainly the river and mountain valleys. This fog should burn
off not long after sunrise Sunday. Low temperatures will average
five to ten degrees lower than those realized this morning. Expect a
mix of the mid 50s to near 60 degrees across the mountains with mid
to upper 60s across the Piedmont.
On Sunday, expect mostly sunny skies, calm or light and variable
winds for the vast majority of the region. The exception may be the
Northern Mountains of North Carolina and neighboring sections of the
Grayson Highlands of Virginia. This area may experience enough low
level convergence and differential heating where winds become south
and advect back into the area some slightly higher dew point
readings by the late afternoon. The result will be some isolated
showers and storms that originate near ridgetop and then move
slowly. High temperatures on Sunday will range from around 80 to the
lower 80s across the mountains to the mid to upper 80s across the
Piedmont.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 255 PM EDT Saturday...
Dry conditions expected Sunday evening under weak/relative high
pressure. Increased low-level southerly flow should allow for a
modest uptick in dewpoints along with some mid-level clouds east of
the foothills of the Blue Ridge, but skies generally clear west.
Lows range from the upper 50s to the mid/upper 60s.
Sensible weather conditions Monday and Tuesday should be governed by
falling 500 mb geopotential heights associated with northern stream
closed low located north of Toronto by 12z Monday. Due to southerly
low-level flow transporting higher dewpoints northward, air mass
across the forecast area should be sufficiently enough unstable
Monday to promote showers and thunderstorms; though it does
begin the day with a convective cap around 800 mb. Secondly,
I`ve noted a slower and slightly more westward shift in the best
dynamic forcing Monday as well as a poorer-defined surface
front in today`s guidance. These trends may reflect a condition
where the best forcing aloft doesn`t necessarily line up with
the time of peak heating and greatest convective instability.
I`ve reduced PoPs areawide by around 10% to account for this,
still in the high-Chance to borderline Likely range. What I
believe unfolds is isolated to scattered showers/storms develop
in the daytime heating along the mountains, becoming more
numerous in coverage with the best height falls late afternoon
into early evening but also weaker toward sunset. A few strong
to locally severe thunderstorms producing gusty to at times
damaging winds are possible due to lifted index values of -3 to
-6 and relatively high downdraft CAPE values around 900 J/kg.
With deep-layer wind shear values at or under 30 kts, storms may
be loosely organized at best so any instances of severe weather
should be more localized/transient. The overnight Day-3
Convective Outlook valid for Monday shows a Marginal Risk/5%
severe probability for our central VA Piedmont counties, with
general thunder indicated elsewhere. A general decrease in
spatial coverage (slight chance level PoPs) are shown after
midnight into the Tuesday early morning hours. Looking at highs
topping out from the mid 70s at elevation, the lower/mid 80s
west of the Blue Ridge to the mid/upper 80s elsewhere.
By Tuesday, digging 500 mb vort from Monday over the Ohio Valley
digs into the Carolinas - a feature which closes off in the 12z GFS
over far western NC. It appears for Tuesday that the focus for
showers and thunderstorms would be mainly east of the WV/VA border.
Questions on the degree of instability in this area, with up to 2500
J/kg of surface-based CAPE, while the GFS is closer to 1000-1200
J/kg. NAM solution may be too warm and too moist, but even the GFS
instability parameters should be sufficient enough to generate
scattered thunderstorms, a few could be strong if the NAM
instability values are correct. Storms should pose a localized heavy
rain threat at least, given their slow moving nature (surface to 200
mb winds are under 20 kts) and high PWATs around 1.8". Storms should
weaken and diminish with sunset Tuesday evening. Highs in the mid
80s to low 90s, warmest in the VA/NC Piedmont and Southside, with
temps at higher elevations in the upper 70s with lows running in the
60s.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 255 PM EDT Saturday...
A bit less clarity on synoptic-scale details for the mid to late
week period, due mainly to the newest wrinkle in the global
guidance: the closed off mid-level low the GFS and the prior ECMWF
run depict to be near North Carolina to start the period. Earlier
solutions had showed the forecast area on the northeastern periphery
of an amplified heat ridge over the center of the country, a pattern
which may have been more favorable for convective complexes to
develop in the Midwest and roll into the Ohio Valley/central
Appalachians. Today`s runs show the mid-level low/trough on
Wednesday shifting westward, weakening the heat ridge as it builds
over the Ohio Valley and keeping the zone of faster mid-level winds
well north of our area. Really two potential scenarios during this
period: (1) warm to hot, humid and with potential opportunities for
thunderstorms or thunderstorm clusters dependent on mesoscale
details, or (2) hot, humid and largely dry. Due to the changes in
the guidance today, it`s hard to predict which one may play out at
this point. For that reason, will stay closer to blended solutions
to minimize errors. However potential exists for change here, mainly
on PoPs/Wx. Nonetheless, it appears that temperatures should trend
above normal at least for late in the week. Indications are at some
point into the weekend we do get into somewhat of a reprieve from
the warm/humid conditions by the upcoming weekend with more
northerly trajectories.
&&
.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
As of 715 PM EDT Saturday...
Frontal boundary will stall to our south across North Carolina
into Sunday. High pressure will build across our area tonight
into Sunday. With a closer proximity to the front, a few showers
may move across North Carolina for next couple of hours.
For the taf sites, VFR conditions will continue this evening
into tonight. Overnight, look for a return of low level clouds
with MVFR and low end VFR ceilings across the mountains. VFR
ceilings are expected east of the crest of the Blue Ridge. Late
night and early morning MVFR river/valley fog is expected along
with some temporary IFR visibilities around daybreak. Any sub-
VFR conditions will quickly trend to VFR Sunday morning. VFR
conditions will continue into Sunday afternoon.
Gusty northwest winds across the mountains this evening will
decrease and become calm or light and variable overnight and
remain that way through Sunday. Winds across the Piedmont will
remain light and variable to calm through the forecast period.
High Confidence in ceilings, visibilities and winds during the
taf period.
Aviation Extended Discussion...
Sunday afternoon and evening light/calm winds and VFR conditions
are still forecast. Some late night/early morning sub-VFR
river/valley fog will be possible.
Active weather returns to the forecast Monday into Tuesday as an
upper trough become positioned across the area. Anticipate an
increase in showers and storms, especially during the peak
heating of the day. VFR conditions will prevail outside of the
heavier showers and storms where temporary sub-VFR conditions
will be the rule. Overnight, late night and early morning sub-
VFR fog and stratus will be possible, especially over any area
that received substantial precipitation.
Wednesday into Thursday, the upper trough lifts northeast of
the area placing us back into more of a summertime Bermuda High
scenario. Anticipate a return to primarily diurnally based
isolated showers and storms. Again, any sub-VFR conditions will
be in association with the heavier showers and storms, and late
night/early morning patchy river/valley fog.
Confidence in the extended portion of the discussion is moderate
to high on the weather elements occuring, but low to moderate on
confidence of the timing of the specifics.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...DS
NEAR TERM...DS/JH
SHORT TERM...AL
LONG TERM...AL
AVIATION...DS/KK
For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php