Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/05/20
Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
405 PM AKDT Sat Jul 4 2020
.SYNOPSIS...
Showers and thunderstorms are expected this evening, mainly from
Fairbanks. A front will reach the Yukon Delta on Sunday and will
slowly push inland.
&&
.DISCUSSION...
The 04/12 UTC model suite initialized well when compared to
observations. The models are in decent agreement through the
weekend; however, agreement breaks down on Monday.
Aloft, at 500 mb, a 546 dam low is currently over the Mackenzie
Delta, while a ridge stretches along the west coast into the
Chukchi Sea. The aforementioned low will very slowly start to
slide to the south tonight. By Tuesday it will be in the central
Yukon Territory, where it will persist into Thursday. The ridge
over the west coast will be knocked south some late Sunday as a
southward moving low approaches the Arctic Coast. A low that is
currently over Siberia will reach the west coast of Alaska on
Tuesday; however, there is a great deal of uncertainty in its
movement thereafter.
Central and Eastern Interior: A shortwave that is associated with
the low over Mackenzie Bay is currently bringing isolated
thunderstorms to parts of the eastern Interior. Looking at
satellite and radar trends, the western edge of the thunderstorm
activity is a bit farther west than we previously anticipated.
Because of this, we did add in isolated thunderstorms for the
Fairbanks area for the evening. Given the timing of the shortwave,
we expect showers and thunderstorms to persist in the eastern
Alaska Range well past midnight. Another shortwave will bring
thunderstorms to areas to the east of Fairbanks again on Sunday.
The HRRR is enthusiastic about the potential for thunderstorms
tomorrow over the Fortymile Country. Chances for showers will
increase late Monday and Tuesday.
North Slope and Brooks Range: Things will be relatively quiet
tonight into Sunday aside from some patchy fog and/or low status
along the coast. A slow moving and decaying front will bring
isolated to scattered rain showers to areas west of Wainwright
Monday and Monday night.
West Coast and Western Interior: A weakening front will move
onshore the Yukon Delta Sunday morning and will continue weaken
as it moves eastward through Monday. Showers will accompany the
front. Ahead of the front, temperatures will trend upwards Sunday,
with many locations in the Western Interior seeing high
temperatures in the upper 60s to lower 70s. Behind the front,
temperatures will cool.
Coastal Hazard Potential Days 3 and 4...None.
&&
.FIRE WEATHER...
Isolated to widely scattered thunderstorms are expected this
evening and again on Sunday, mainly over areas to the south and east
of Fairbanks. Expect the driest conditions to continue to be over
the Yukon Flats.
&&
.HYDROLOGY...
No concerns at the moment.
&&
.AFG WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory for PKZ210-PKZ245.
&&
$$
JUL 20
Area Forecast Discussion
National Weather Service Charleston SC
1015 PM EDT Sat Jul 4 2020
.SYNOPSIS...
A stationary front will linger south of the area through the
weekend, then lift back northward by early next week. Low
pressure will then bring unsettled weather to the region for
much of next week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 1010 PM: I will updated to remove headlines for the
Coastal Flood Advisory. The forecast remains on track. No
additional changes needed with this updated package.
As of 835 PM: KCLX indicated that the sea breeze has pushed west
of the forecast area, with no showers over the CWA. I will
update the forecast to remove the mention of showers this
evening and make minor temperature tweaks.
As of 6 PM: KCLX detected isolated showers along a sea breeze
pushing inland across Berkeley and Dorchester Counties. The
latest run of the HRRR indicates that a few showers will develop
along the breeze across SE GA over the next hour or two. Given
the state of the Cu field west of the sea breeze and latest
radar trends, I will update the forecast to add SCHC PoPs to the
forecast through the early evening.
Previous Discussion:
A weak mid-level low will be over the Lower MS Valley, causing
northwest flow overhead. At the surface, weak high pressure
across our area will keep a stationary front located to our
south. Though, models indicate moisture and some lift associated
with the front should approach our southernmost locations late
tonight. Hence, we have slight chance POPs for McIntosh County
and vicinity. A rumble of thunder also isn`t out of the
question given the instability in place. But nothing severe.
Elsewhere, plenty of dry air in place should lead to a rain free
night. Otherwise, light onshore flow is expected to generate
some low clouds later tonight. Though, these shouldn`t cause
visibility issues outside of the smoke from the fireworks. Lows
will mostly be in the 70s.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
All models continue to indicate a more active/unsettled pattern to
develop during this period. A broad upper low over the lower MS
River valley will slowly move northeastward toward the region
through early next week. As this system moves toward the area, it
brings higher values of deep layer moisture and instability. This
will result in an increasing trend in PoPs.
Sunday will begin the transition toward increasing PoPs, starting
from south to north. Have kept chance PoPs mainly over the GA
region. Monday and Tuesday, models continue to go likely to
categorical PoPs. A little uncomfortable going with likely to
categorical PoPs that far out, but models have been consistently
trending in that direction for the last several runs. Rainfall
totals through Tuesday expected to be 1-2 inches south of the
Savannah River, and 1/2-1 inch north of the river.
High temperatures are expected to be near normal on Sunday, then
slightly below normal for Monday and Tuesday due to increased cloud
cover and PoPs. Lows in the lower to mid 70s.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Low pressure is forecast to linger in the region mid to late week.
There are still large discrepancies between models regarding the
position and evolution of the low, however the overall pattern
favors higher than normal rain chances, especially during the mid-
week time frame. High temperatures will average slightly cooler than
normal, while lows stay a couple degrees above normal.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
VFR. Smoke from fireworks should remain localized and are not
expected to impact the terminals.
Extended Aviation Outlook: Sunday: Mainly VFR conditions expected.
Monday through Thursday: Periods of flight restrictions likely,
especially during the afternoon/early evening within scattered to
numerous showers and thunderstorms.
&&
.MARINE...
Tonight: Weak high pressure over the area will keep a
stationary front well to our south. The weak pressure gradient
should keep sustained winds 10 kt or less. Seas will be 1-2 ft.
LONG TERM MARINE...SUNDAY THROUGH THURSDAY...No highlights
expected Sunday through Wednesday with generally southerly winds
of 15 knots or less and seas 3 feet or less. Scattered to
numerous showers and thunderstorms expected. Models indicate a
developing surface low later Wednesday and Thursday, possibly
tracking inland/well west of the waters. The track and intensity
of this low pressure system will impact how strong the winds
will get. Right now, the latest model trends indicate
southwesterly winds by Thursday, possibly increasing to the 15
to 20 knots. However, due to uncertainty, the forecast for this
period was left unchanged.
&&
.TIDES/COASTAL FLOODING...
Astronomical influences will maintain higher than normal tide
levels into early next week. Minor coastal flooding will be
possible around the time of the evening high tides, primarily
along the South Carolina coast. In addition, the risk for heavy
rain early next week will only add to any tidal flooding.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...NED
SHORT TERM...
LONG TERM...ETM
AVIATION...BRM
MARINE...
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Dodge City KS
659 PM CDT Sat Jul 4 2020
...Updated for aviation discussion...
.SHORT TERM...(This evening through Sunday)
Issued at 254 PM CDT Sat Jul 4 2020
We have a low overall shear profile environment with high theta-e
owing to pwats well in excess of 1 inch in far sw KS. The HiRes
model earlier this morning had backed off the idea of an mcs
reaching western KS in the evening and began allowing the
central/eastern CO convection to decay before reaching the Syracuse
to Elkhart area. However the HRRR is indicating a weak convergence
zone from around Meade to Garden City where a pulse storm or two
could develop, in the late afternoon. There continues to be nothing
in the CAMs at this time to indicate any organized storms this
evening in the sw, and general thunder outlook has been removed in
the central KS counties. With this in mind we have scaled back the
probabilities of precipitation fairly significantly for this evening
and tonight while not wholesale removing them.
.LONG TERM...(Sunday night through Saturday)
Issued at 254 PM CDT Sat Jul 4 2020
A flat ridge aloft remains in place Sunday and Monday before the
patten begins to show a slight shift to sw flow aloft and a ramp
down in even the low PoPs beginning Tuesday. The trend after that is
for far hotter temperatures as we head through the middle of the
week and toward the weekend. The GFS develops an MCS Wednesday
night/Thursday morning in the central Plains, developing over the
DDC and spreading east overnight into the moisture axis of the lower
Plains. Beyond that, the National Blend model is indicating
widespread highs in excess of 100 degrees over all of western and
central Kansas by Friday and Saturday. Impacts from heat indices may
become a concern in central Kansas if the dew point remains around
60 degrees or higher.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 655 PM CDT Sat Jul 4 2020
A weak pressure gradient will result in light east to southeast
winds through the period along with VFR conditions. There is only
a very small chance of thunderstorms moving eastward out of
Colorado overnight after 06z.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 68 91 66 89 / 10 30 20 20
GCK 66 93 64 89 / 10 30 20 20
EHA 66 91 64 88 / 30 30 20 30
LBL 66 94 65 89 / 10 30 20 20
HYS 66 90 67 89 / 10 20 30 20
P28 70 92 69 91 / 10 20 30 20
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Russell
LONG TERM...Russell
AVIATION...Finch
Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
935 PM CDT Sat Jul 4 2020
.UPDATE...
Both WV and IR channels are showing a cluster of upper level clouds
over central Texas pushing to the south. Area Doppler radars are
showing only light echoes associated with this activity at this time.
Latest HRRR and NAM 3Km do not show any convection making it down to
our region for the tonight period. However, some of the outflow
boundaries coming out of this activity will act as focus for possible
showers and storms across the Hill Country on Sunday afternoon.
Otherwise, a warm overnight period with lows in the low to mid 70s
and Sunday`s high temperatures in the upper 90s to 105 degrees for
Del Rio.
&&
.PREV DISCUSSION... /ISSUED 651 PM CDT Sat Jul 4 2020/
AVIATION...
/00Z TAFS/
VFR conditions are expected across area airports through the
forecast period. Winds should remain light through Sunday morning and
from the southeast and south for the most part with gusts up to 20
knots especially over KDRT before sunset (between 02Z and 03Z
Sunday). HiRes models suggest for showers and storms to fire up on
Sunday afternoon across central Texas and then move closer to the
Hill Country and the Austin area. At this time, there is low
confidence on this outcome and decided to keep out mentioning
convective activity. Winds will remain from the southeast and south
on Sunday afternoon while averaging from 7 to 10 knots with gusts up
to 16 knots along the Rio Grande/KDRT/
PREV DISCUSSION... /ISSUED 219 PM CDT Sat Jul 4 2020/
SHORT TERM (Tonight through Sunday Night)...
The upper level ridge which has kept South Central Texas hot and dry
for the last several days has shifted to the west. At the same time
a mid-level area of low pressure is beginning to take shape across
Mississippi and Louisiana. This leaves Texas caught in the middle
with generally northerly or northwest flow aloft.
After another hot day today and mild night with little to no cloud
cover tonight, changes begin on Sunday. With the weakness in the
ridge convection will be possible well to our N and NW tonight along
a weak boundary. While this activity itself should dissipate long
before it reaches South Central Texas, outflows from that activity
could approach the Hill Country and Austin Metro area Sunday
afternoon. Combined with decent moisture and plentiful sunshine
there may be enough lift to generate some very isolated shower and
thunderstorm activity. This is depicted in all of the short term
models like the Texas Tech WRF, HRRR, NAM, NMM/ARW, and others,
while the global models and NBM remain dry tomorrow. While most
folks won`t see rain on Sunday, there could be a lucky few that see
a brief downpour before the sun returns. Increased cloud cover from
the remnant convection across north Texas and cumulus hanging around
Central Texas tomorrow should keep temperatures a degree or two
cooler than today, but upper 90s to near 100 are still expected.
With the weakness in the ridge the rain chances Sunday and continued
slight rain chances in the first few periods of the long term are
all low confidence events with very little in terms of a focus for
convection but plenty of heat and moisture to work with should
anything get going.
LONG TERM (Monday through Saturday)...
Midlevel ridge will have since fractured and retreated westward with
a slowly retrograding upper level trough over the Mississippi Valley
by Monday. This trough looks to meander around the Arklatex Monday
and Tuesday bringing likely chances for showers and storms for the
eastern portion of the state. Upper level pattern will be somewhat
favorable over our northeastern/eastern CWA for some storm activity
early next week along with pwat values nearing 2 inches. Slight
chances to chances of showers and storms for Monday and Tuesday with
the possibility of persisting into Wednesday. Euro is the only model
as of now that has storms that far west still on Wednesday. This
added moisture will keep high temperatures suppressed to the mid 90s
for these northeastern areas but will make it difficult to cool off
at night with overnight lows forecasted to remain in the upper 70s.
Although high temperatures will be in the mid 90s, heat indices will
still remain above 100 degrees for a good portion of the region. Heat
indices will be something to monitor closely much of next week.
Currently calling for 105 to 108 heat index values along the Rio
Grande and 103 to 106 for I-35 corridor and Coastal Plains, Monday
through Friday. Should remain below heat advisory criteria for all
areas but will come within a few degrees for our eastern zones.
Subtropical ridge begins to expand from the west on Wednesday and
forms a broad area of high pressure over the southern US in
conjunction with ridging over the central Gulf by end of the week.
This will usher away any other chances for rain and usher in a
gradual warm up of temperatures back into the upper 90s for most of
the area and remaining 100 to 103 along the Rio Grande.
Blended guidance in the long term suggests daily afternoon chances
for seabreeze driven convection for far southeastern counties but
did not give this much credence give the large subsidence pattern
expected to anchor in place.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 77 101 76 96 77 / 0 20 - - 10
Austin Bergstrom Intl Airport 74 99 73 96 76 / 0 20 - - 10
New Braunfels Muni Airport 73 99 73 97 76 / 0 - - - 10
Burnet Muni Airport 75 98 73 94 74 / 0 20 10 - 20
Del Rio Intl Airport 78 105 79 105 80 / 0 0 - 0 -
Georgetown Muni Airport 77 99 74 97 76 / 0 20 10 10 20
Hondo Muni Airport 71 102 73 101 76 / 0 - 0 0 -
San Marcos Muni Airport 73 99 75 97 75 / 0 - - - 10
La Grange - Fayette Regional 76 98 77 97 77 / - 10 - 10 10
San Antonio Intl Airport 77 100 78 99 77 / 0 - - - 10
Stinson Muni Airport 74 101 76 98 77 / 0 - - - -
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Short-Term/Aviation...17
Long-Term...Runyen
Area Forecast Discussion
National Weather Service Jackson MS
944 PM CDT Sat Jul 4 2020
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
Scattered rain showers will persist over the next hour or so.
There has been some training with some storms and we`ve seen
localized flash flooding over the last couple of hours especially
in the north/south east and that will be the main concern over
until things begin to diminish. An additional half to an inch of
rain could be possible for areas east of I-55. Around 11pm we
should see some clearing in the east with no real expectations of
reinitiation through the night but can`t rule out an isolated
shower or two after midnight in some places. There is a chance for
fog again tonight/early morning before daybreak for areas in the
south. Partly to mostly clouds skies will prevail with lows in the
lower 70s./JNE/
&&
.AVIATION...
00Z TAF discussion:
Scattered convection is across all of Central Mississippi this
evening. Mainly VFR forecast overall, with some MVFR vis closer to
dawn for HBG/PIB. RAP is a little more generous with the
development of fog, putting JAN/HKS on the edge of the reduced
visibilities. Given enhanced llvl RH and little to no wind
overnight... again, will have to watch for clearing. IFR cigs near
dawn for the southeast as well. Remainder of the forecast is
similar with attempt to capture afternoon convection tomorrow.
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 73 89 72 86 / 30 67 47 91
Meridian 72 89 72 87 / 30 68 44 88
Vicksburg 74 90 74 86 / 30 66 50 88
Hattiesburg 73 89 72 87 / 30 85 52 92
Natchez 73 88 72 84 / 30 79 57 90
Greenville 74 89 74 87 / 30 63 35 82
Greenwood 74 91 73 88 / 30 64 29 81
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
JNE
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
620 PM CDT Sat Jul 4 2020
.SHORT TERM...
208 PM CDT
Through Sunday night...
Weak surface high pressure will remain in place across the western
Great Lakes region through the remainder of the Independence Day
weekend. Hot and slightly more humid weather will persist, with lake
breezes cooling areas near Lake Michigan. An isolated afternoon
shower or thunderstorm can`t be completely ruled out, though the
likelihood remains quite low.
Early afternoon GOES water vapor imagery depicts a weak mid-level
short wave propagating southeast across southern Lake Michigan and
adjacent portions of lower Michigan and northern Indiana. RAP
initialized soundings indicate fairly dry thermodynamic profiles
above the boundary layer, which along with relatively warm mid-level
temps and poor mid-level lapse rates should limit development of any
extensive cloud cover. Regional surface obs do show that boundary
layer dew points have crept up a bit, especially within the marine
layer off of Lake Michigan where dew points in the upper 60s/around
70 were noted, as well as hazy conditions over the cooler lake
waters. Thus while temps across the region are fairly similar to
this time yesterday, the heat index has nudged up a bit, with some
low-mid 90s observed early this afternoon. Warm/dry sounding
profiles are generally not favorable for convective development, an
isolated afternoon shower or thunderstorm can`t be completely ruled
out in the vicinity of the lake breeze boundary, where slightly
higher marine-influenced dew points and localized convergence could
perhaps produce deeper convective updrafts during peak heating.
Better chances will exist farther east/southeast into Indiana
however, where slightly cooler mid-level temps will be found beneath
the aforementioned mid-level short wave.
More of the same appears to be in store for the region Sunday,
though with a slight increase in low level warmth. Temps in the 925-
850 mb layer are progged to warm a Celsius degree or so on Sunday,
supporting temps solidly into the lower 90s away from the Lake
Michigan shore, and probably a mid-90 reading in a spot or two. With
surface dew point temps again in the mid-upper 60s during peak
heating, the heat index will likely top out in the mid 90s for the
most part, with a few upper 90s possible. Similarly to today, an
isolated shower or thunderstorm is not completely out of the
question, with the afternoon lake breeze boundary again the primary
focus for initiation, though as today the potential for any isolated
storms looks to be greater off to the east of the cwa across
southwest Michigan and north central Indiana. Nighttime conditions
both tonight and Sunday night will be mostly clear/partly cloudy,
with mild overnight temps from the mid-60s to lower 70s.
Ratzer
&&
.LONG TERM...
249 PM CDT
Monday through Saturday...
Hot and increasingly humid weather continues to be the key
message for the long term period as the area remains locked within
a persistent summertime pattern. This continues to be the primary
forecast concern, especially considering we could be approaching
heat advisory criteria (Heat indices around 105 degrees) in some
areas Wednesday and Thursday.
Monday still is appearing to be a precipitation free day across
most of the area, as we continue to only carry some slight chances
for afternoon isolated storms. Humidity will increase a bit
Monday, but heat indices should remain at or below 100, with
actual temps in the low 90s inland from the lake. Cooler afternoon
temperatures (in the lower 80s) are likely near the lake due to
the likelihood of an lake breeze.
The heat and humidity will ramp up by mid week as heights aloft build
across the Mississippi Valley and lower Great Lakes concurrently
with the northward flux of the humid airmass currently residing
to our south. The net result of this will be hot and humid conditions
Tuesday through at least Thursday, with Wednesday and Thursday
potentially being the most oppressive. Temperatures on these days
are forecast to be into the mid 90s, with dew points into the
lower 70s, which would support heat indices in the 100 to 105
range.
Unlike the last few days, we will have some occasional diurnal
thunderstorm chances with the arrival of this very humid airmass.
Capping should become minimal, so we cannot rule out the
possibility for some isolated to widely scattered afternoon
storms at times Tuesday through Thursday. While this is the case,
the best potential for a higher coverage of thunderstorms is
looking to be late Thursday into Friday as a more substantial
mid-level disturbance and surface cold front approaches.
KJB
&&
.AVIATION...
For the 00Z TAFs...
Some minor VSBY restrictions in smoke from fireworks could occur
later this evening, particularly at MDW, though with far fewer
firework shows than normal, confidence is low. Cannot rule out
some brief MVFR VSBY at RFD with BR/HZ pre-dawn Sunday. Otherwise,
look for VFR conditions and light winds through the TAF cycle.
- Izzi
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 311 PM CDT Sat Jul 4 2020
Forecast Summary:
Upper ridge currently over the Plains will break down in our area
for several days next week before building back in even stronger for
late next week and weekend. Thunderstorm chances will increase
during the break-down period as systems are allowed to settle a
little farther south from current storm track. Then even warmer
temperatures are expected Friday and Saturday.
Tonight through Monday:
Upper ridge extending from southern Arizona/New Mexico into the
Central Rockies and Central Plains will remain in place into Monday.
A weakness in ridging was noted on RAP analysis and water vapor
imagery drifting south through Missouri. Associated moisture
extended northwest into southeast Nebraska and southwest Iowa
where cumulus field has occasionally enhanced through the
afternoon. If we were to see any convection through the evening,
it would likely be in this area. The same scenario will present
itself Sunday afternoon. Current model trends keep bulk of any
convection south of Nebraska and Iowa, and since chances and
expected coverage will remain low, will keep current dry forecast
going for this evening, but add a small chance for Sunday
afternoon.
By Monday, system riding westerly flow in the Northern Plains Sunday
night will nudge a cold front southward toward the South Dakota
border in the afternoon. Plume of low and mid level moisture
intersecting this boundary near northeast Nebraska should result in
scattered convection, perhaps as early as late Sunday night. SPC
has painted a marginal risk of severe along frontal zone, just
touching northeast Nebraska. And given MLCAPE near or above 3000
J/kg with modest bulk shear approaching 30kt, this seems
reasonable. Southeast development farther into eastern Nebraska
and southwest Iowa is possible through the day.
Tuesday through Saturday:
Ridging flattens more Tuesday through Thursday as westerlies sink
farther south into the region with lowering height fields. This
pattern is more conducive to scattered convection as minor ripples
in flow provide necessary forcing and mid level cooling to take
advantage of a generally unstable environment. Identifying and
timing these disturbances this far out is impossible, so will try to
focus highest probabilities with stronger shortwaves which models
are a little better at recognizing. There has been some
consistency between GFS and ECMWF the last couple of days in
showing Monday night and especially Wednesday night for these
higher probabilities.
Otherwise temperatures in the lower 90s will be common Tuesday and
Wednesday, and maybe a little cooler Thursday given lingering precip
and cloud cover. Highs should reach at least the middle 90s Friday
and Saturday as heights rise with ridge building back into the
region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 618 PM CDT Sat Jul 4 2020
VFR conditions through the period with southeasterly winds less
than 12 knots.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...Dergan
AVIATION...DeWald
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
757 PM EDT Sat Jul 4 2020
.SYNOPSIS...
A weak backdoor front will continue to slowly slide through central
NC overnight, but will dissipate Sunday morning. Additional shower
and thunderstorm chances are expected across the area Sunday
afternoon.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 757 PM Saturday...
Isolated showers and storms continue to percolate across the area
this evening thanks to modest instability ahead of a weak backdoor
front. The majority of the storm activity earlier today was confined
to areas north and east of Raleigh where MLCAPE was on the order of
2500 J/KG this afternoon. However additional storms formed on
colliding outflows as far away as the NW Piedmont and across the
Sandhills. Although there has been an overall decrease in areal
coverage of storms since 23Z, there will be at least a continued
slight chance of showers and storms area-wide through the remainder
of the evening hours given lingering surface based instability.
Latest runs of the HRRR depict a rapid decrease in storm coverage
after 04Z and I will keep the forecast dry after that point.
Lows tonight will range from the upper 60s to lower 70s, with the
coolest values in the northern Coastal Plain. Given rain cooled air
and weak onshore flow in these areas, there`s a good chance of some
cloud/fog development early Sunday morning and I drew in some areas
of patchy fog around daybreak.
Overall the forecast is in great shape, only making minor
adjustments to near-term grids based on observational trends.
&&
.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 400 PM Saturday...
A subtropical ridge in the mid levels will strengthen and expand
with associated anticyclonic, subsident flow, amidst and 10-20 meter
mid level height rises over cntl NC both Sun and Sun night.
At the surface, an outflow and maritime nely flow-reinforced front,
likely with areas of low overcast on the ne/cool side, will extend
across cntl NC in the vicinity of I-40 Sun morning. The front will be
intersected by a lee trough/low over the wrn Piedmont. Meanwhile,
weak, 1016 mb high pressure will extend down and offshore the middle
Atlantic coast, with a cooler and more stable air mass expected to
extend inland across ern VA and nern NC. Scattered showers and
storms will focus along those boundaries with diurnal heating
through the afternoon. While convection will again be weekly-steered
and sheared, and slow-moving, a high DCAPE environment in excess of
1000 J/kg will favor strong to locally damaging wind gusts.
Otherwise, it will be hot again, with temperatures mostly 90-95 F,
and with generally persistence lows in the lwr 70s.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 200 PM Saturday...
The medium-range models develop a low over the Deep South/ARKLATEX
by Monday. Otherwise, the flow aloft will be somewhat diffuse, with
the aforementioned low slowly drifting east-northeast and amplifying
a weak trough before moving east through the region mid- to late-
week. However, specifics with respect to the evolution of the
low/trough are uncertain, resulting in a lower than normal forecast
confidence Thursday onward. At the surface, south-southeasterly flow
into the area off the Atlantic will persist, with high pressure to
the east and relatively low pressure to the west. There is not very
good agreement with the development and subsequent progression of a
low developing in response to the low aloft, thus confidence with
exactly if and when and how it would impact central NC is low at
this time. Regardless of the coverage, still expect shower and
thunderstorm activity to be diurnally driven and best chances to be
across the southern portions of the area. Temperatures should be
within a category or two of normal through the period, with the best
chance for below normal highs on the days with more extensive cloud
cover and convection. Highs will generally be in the mid 80s to low
90s and lows in the upper 60s to mid 70s.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 757 PM Saturday...
Isolated showers and storms continue across the area this evening
with the most vigorous activity around the Triad sites and Rocky
Mount. There has been a gradual weakening of storms since about 23Z
and this trend should continue for the rest of the night with the
loss of daytime heating and instability. Still looks like the best
chance of overnight stratus will be in the northeast (RWI primarily)
where IFR cigs could develop just before daybreak. Elsewhere, VFR
conditions should prevail. Additional showers and storms are
expected on Sunday, perhaps a little earlier than what was seen
today as there will be a stalled surface boundary across central NC.
VCSH introduced at all TAF sites Sunday afternoon except RWI (may be
too stable given today`s convection).
Outlook: Humid, sely flow off the sw N. Atlantic/Gulf Stream will
increase the probability of morning stratus/fog early to mid next
week, along with mainly diurnal convection whose coverage may be
enhanced by the proximity of a broad and weak area of low pressure
in the mid and upper levels of the atmosphere.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Leins
NEAR TERM...Leins
SHORT TERM...MWS
LONG TERM...KC
AVIATION...Leins/MWS