Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/14/21
Area Forecast Discussion
National Weather Service La Crosse WI
1040 PM CDT Thu May 13 2021
.SHORT TERM...(This evening through Friday)
Issued at 245 PM CDT Thu May 13 2021
Forecast concerns will be how far east showers will advance Friday,
clouds, and temperatures.
Clear skies this morning allowed a few spots to drop into the 20s
(BCK and CMY), otherwise, most locations held in the 30s and 40.
Scattered to broken clouds were noted on visible satellite at 18Z,
however with increasing southwest winds, temperatures were all in
the 60s by 18Z. The WSR-88D mosaic did show a weakening line of
storms over southeast South Dakota and eastern Nebraska.
Tonight, an upper level jet over Montana/Colorado will dive
southeast, gradually shifting eastward across South Dakota and
Nebraska toward Iowa and Kentucky/Tennessee. Meanwhile, a 40 to
50kt low level jet increases across Kansas and Nebraska and to a
lesser extent around 25kts into southeast Minnesota and eastern Iowa
Friday morning. Thunderstorms will re-develop over parts of South
Dakota, Nebraska and Kansas and we`ll see showers develop far east
along the Missouri River around 06Z. These showers will result from
a shortwave dropping southeast in the northwest flow aloft in
combinations with the upper level jet support and increase moisture
transport with the strengthening low level jet. The stronger
frontogenesis and 700 mb warm advection tracks south of the forecast
area with weaker forcing across the forecast area. Timesections and
soundings show moistening in the 3000-7000ft layer 12-00Z with
limited lift. Will continue with isolated to scattered pops. The
EC EPS 90th percentile for rain has only a trace to 0.02 west off
the Mississippi River through 00Z and only of 50/50 probability of
over .01 toward La Crosse. Current convective allowing models are
mainly dry through 15Z. The HRRR is the most robust with greater
coverage making it to the Mississippi River by 00Z while the
RAP/NamNest/ARW focus more over parts of northeast Iowa. With the
lack of forcing farther north, will mention sprinkles and have the
higher pops over parts of northeast Iowa. The instability and shear
are better north and south of the area. With more clouds Friday
have highs in the 60s to around 70. South winds should be gusty at
times around 20kts for parts of southeast Minnesota and northeast
Iowa.
.LONG TERM...(Friday night through Thursday)
Issued at 245 PM CDT Thu May 13 2021
A series of shortwave energy embedded in the northwest flow aloft
will produce periodic chances of showers across the forecast area
Friday night into Sunday. Instability is lacking during this time
frame across much of the forecast area...storm chances remain
low. The 13.12z GFS/NAM show weak moisture transport/convergence
and weak forcing with the shortwave energy...especially Friday
night into Saturday morning. Higher chances for showers will occur
during this time. QPF amounts look to be up to a quarter of an
inch...mainly across northeast Iowa and southwest Wisconsin.
Main forecast concern Sunday night through Thursday are
precipitation chances and temperatures through the period. The
13.12z GFS/ECMWF/GEM are in decent agreement in amplifying upper
level ridge over the central United States by middle of next week.
With southerly winds and ridge building in over the area...warmer
air is expected to advect into the forecast area by middle of next
week. The 13.12z GFS/ECMWF are warming 925mb temperatures to plus
15 to plus 20 degrees celsius by 00z Wednesday. This would
suggest high temperatures in the upper 70s to middle 80s
potentially. However... the deterministic models suggest weak
pieces of energy in the south to southwesterly flow aloft to track
into the Upper Midwest Wednesday into Thursday. Depending on
shower/storm activity and clouds...this may produce cooler
temperatures across the forecast area...especially Wednesday into
Thursday.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1040 PM CDT Thu May 13 2021
Mostly clear skies overnight will give way to broken VFR clouds
Friday as a trough of low pressure approaches the region. A few
-shra are also possible after 19z west of the Mississippi (KRST)
and by Saturday 00z at KLSE. Some MVFR cloudiness looks likely
at KRST after Saturday at KRST. Otherwise, light south winds
overnight will become a bit breezy, gusting near 20kt during the
day Friday.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Zapotocny
LONG TERM...DTJ
AVIATION...DAS
Area Forecast Discussion
National Weather Service Dodge City KS
613 PM CDT Thu May 13 2021
...Updated aviation discussion...
.SHORT TERM...(This afternoon through Friday night)
Issued at 1145 AM CDT Thu May 13 2021
Pressure gradients are increasing as of midday, as the cool
surface ridge finally exits, and return flow establishes. South
winds will gust in the 30-40 mph range this afternoon and early
evening. The warming trend continues, with all locations within a
few degrees of 70 at max heating, about 10 degrees warmer than
Wednesday.
All grids are dry for all zones through 7 pm. High based
thunderstorm development is expected across Nebraska early this
evening, which organizes into a complex with a consolidated cold
pool over south central Nebraska and north central Kansas by late
evening. Latest HRRR iterations and 12z NAM suggest this activity
may clip the far northeast reaches of our zones, and kept some
low/slight chance pops in for these locales through the night to
cover this possibility. Outflow from this small MCS may pose a
strong wind threat tonight (particularly in the Hays/Ellis
vicinity), and it will be monitored. Agree with SPC`s reduction in
marginal wind/hail probability on the 1630z update, favoring only
the I-70 corridor tonight. Elsewhere, south/southeast winds will
remain elevated and gusty overnight with a strong low level jet
keeping the boundary layer mixed. As such, the warming trend in
the minimum temperatures will continue, with most locations near
50 Friday morning.
Convective instability finally returns Friday, with warmer
afternoon temperatures near 80, and continued moist advection
pushing dewpoints well into the 50s. 12z NAM continues to develop
MUCAPE around 2000 J/kg by late afternoon. Even though instability
returns Friday afternoon, with no triggers for initiation
available, all grids are dry through 7 pm. Guidance is in good
agreement that convection will need the higher terrain of eastern
Colorado to initiate, and then subsequently move southeast into
SW KS in the WNW flow aloft. Moderate instability and modest shear
will support marginally severe wind/hail from the strongest
activity Friday evening, per 5% wind/hail SPC probability. High
end/significant severe is not expected. Highest pops remain
focused on Friday evening. The warming trend continues with min
temperatures sunrise Saturday in the lower to mid 50s.
.LONG TERM...(Saturday through Thursday)
Issued at 215 PM CDT Thu May 13 2021
There is no shortage of rainfall opportunities in the long term,
and a very wet regime is expected with numerous rounds of either
stratiform rain/showers and periods of thunderstorms.
12z ECMWF maintains great continuity from its previous runs,
keeping the closed cyclone in the vicinity of California Saturday
through Sunday. Moisture and instability will be sufficient to
support convection both days this weekend, but with the better mid
level flow and effective bulk shear displaced well westward,
there continues to be kinematic concerns regarding the severity
of the expected storms. Although modest for May, the ingredients
appear sufficient to support at least marginally severe wind/hail
both Saturday and Sunday afternoon/evening. Chance to likely pops
from the NBM were accepted, but organization will be a struggle
for many storms, with outflow dominant tendencies and heavy rain
potential (given the relatively weak flow/slow storm movement).
Afternoon highs in the upper 70s and lower 80s, with lows in the
50s over the weekend.
12z GFS/ECMWF continue to show a slow drift eastward of the weak
closed low, still over western New Mexico Tuesday morning. At
least a transient Rex block attempts to develop, with 12z ECMWF
building a 580-582 dm upper high near South Dakota Tuesday. This
will slow the cyclone`s ejection to a crawl and encourage a
southward track, with ECMWF placing the cyclone near Midland,
Texas 7 pm Tuesday. GFS and its ensembles are aligning with this
thinking, with its cyclone also in west Texas late Tuesday. This
track would clearly keep the warm sector and its associated severe
risks well south of SW KS, with any rainfall in our region more
stable/stratiform in nature. Healthy pops from the NBM early next
week were retained, considering the proximity of the cyclone and
its deformation. Afternoon temperatures from NBM/MEX are also
trending cooler, given the expected clouds and rainfall.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 613 PM CDT Thu May 13 2021
A cluster of storms over western Nebraska is expected to track
southeast into tonight. While there is some uncertainty, some of
the latest short term model guidance moves the southwest edge of
this cluster through the Hays terminal by around 04-06z. For now
will include VCTS along with a tempo group with variable, gusty
winds. The southwest Kansas terminals should see southerly winds
continue overnight with LLWS developing. Winds at GCK/DDC could
also become northeasterly later tonight if outflow from the
northern Kansas thunderstorms can make it that far southwest.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 50 81 55 80 / 10 20 50 40
GCK 49 81 53 78 / 10 10 50 20
EHA 50 83 53 81 / 10 10 30 20
LBL 48 82 53 83 / 10 20 40 20
HYS 50 78 55 74 / 20 20 60 50
P28 51 78 58 80 / 20 20 60 50
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Turner
LONG TERM...Turner
AVIATION...Gerard
Area Forecast Discussion
National Weather Service Gray ME
1042 PM EDT Thu May 13 2021
.SYNOPSIS...
A band of showers will cross portions of the region through
this evening and again Friday afternoon. Thereafter, warming
weather will continue but and we will have to dodge a daytime
rain showers and thunderstorms over the weekend as the morning
sunshine provides some instability. High pressure will move off
the coast early next week before a cold front approaches from
the northwest on Tuesday. Cooler conditions will arrive midweek.
&&
.NEAR TERM /TONIGHT/...
1045PM UPDATE...
Primary adjustments with this update were to overnight lows.
Clouds and showers have dissipated pretty quickly and
temperatures will be on their way down again. Not expecting
temperatures to get as cold as last night, but we will likely
see a run at the freezing mark again in the northern valleys.
Outside of there, some upper 30s are possible.
645PM UPDATE...
Made some minor adjustments to temperature, sky cover, and
precipitation chances. Shower activity is quite sparse and
unlikely to get much more numerous. Thunderstorm threat is quite
low, so this was removed. Afternoon cumulus has already shown
signs of decay, so sky cover has been adjusted downward as well.
ORIGINAL DISCUSSION...
A weak disturbance will continue to bring a few scattered
showers to the region through this evening with the best chance
over the mountains. The atmosphere will continue to be unstable
with a slight chance for a thunderstorm with gusty winds as
well. This precipitation will weaken as we head through the
night with the latest HRRR ending any showers after 06Z.
Temperatures will drop into the 30s in the mountains with 40s
for overnight lows expected over southern and central areas.
&&
.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
A weak short wave will cross the forecast area once again on
Friday. This will lead to a few scattered showers and possibly a
thunderstorm, mainly with the aid of daytime heating, modest
destabilization and CAPE values around 200 J/KG.
Heights aloft will be slow to rise during this period. However,
H8 temperatures will top out above +4C during the afternoon.
With partly sunny conditions, this will allow surface
temperatures to reach the lower to mid 70s in most locations.
There will be a seabreeze during the afternoon hours as the
gradient becomes weak, especially along the Midcoast region of
Maine where temperatures will be confined to the 60s for highs.
Very dry conditions will continue on Friday with surface dew
points in the 20s and 30s. An increasing gradient aloft and
increased mixing during the daytime hours will allow for gusty
winds as well.
Nightfall will once again allow for stabilization and a
weakening/dissipation of the showers. We will likely be frost
free across much of the region with upper 30s in the north and
40s in the south.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
This weekend, broad surface high pressure crests the East Coast,
pushing out over the Atlantic early next week with warm and
pleasant temperatures. While high pressure provides a fairly
quiet weather pattern for a large portion of the eastern CONUS,
upper level disturbances crossing to our north through the
weekend will provide support for diurnally driven showers and
storms. Next week, the main question will be if/when upstream
blocking over the Atlantic breaks down and allows for a more
amplified patten to develop.
Starting Saturday...cumulus and the first showers of the day will
pop by mid-morning with strong mixing while temperatures warm
through the 60s on their way to the mid-70s over the southern
interior, near 70 elsewhere. Between strong mixing and
moderately steep lapse rates aloft leading to a few hundred
J/kg of tall+skinny CAPE, there will be adequate thermodynamic
forcing to produce thunderstorms... especially over the
mountains with additional convergence there in the weak-flow
regime. Speaking of weak flow, there won`t be much dynamic
support for sustained updrafts with 0-6 bulk shear clocking in
at 15-25 kts at best. So, am expecting short-lived showers and
storms with the stronger cells having potential to produce
briefly gusty winds in outflow as storms collapse through a deep
mixing layer. Sunday is almost a repeat with the only real
difference being a little more upper level support... which
should lead to greater coverage of showers that last into the
early overnight hours. One mesoscale component to keep an eye on
as we near the weekend will be the behavior of the seabreeze...
weak surface flow will allow a strong sea breeze to develop,
which may then become a focus for convection inland. Elevated
instability doesn`t look strong enough to overcome the stability
of the sea breeze, so am expecting overall a pretty nice day
along the coast - albeit with a cooler breeze coming off the
waters.
With high pressure settling east out over the waters, a moist
onshore flow develops by Monday. The moisture availability could
lead to another round of diurnally driven showers and a few
afternoon thunderstorms. Beyond that, the model suite is
beginning to hone in on a common solution WRT a shortwave
tracking across Canada and diving southeastward toward the
eastern maritimes early next week. This wave pushes a cold front
southeastward across New England around the Tuesday timeframe
with rain showers. After that... models diverge greatly when it
comes to bringing in another ridge with warming for the second
half of the week or keeping cool troughing overhead.
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Short Term...Mainly VFR conditions tonight. Similar conditions
expected on Friday with mainly diurnally driven showers and
possibly a thunderstorm bringing MVFR conditions to a few
locations.
Long Term...VFR prevails at all terminals through the long
range with chances for restrictions in afternoon -SHRA/TSRA,
mainly Saturday and Sunday but possibly Monday as well. This
will be most likely for KHIE/KLEB... and least likely for
coastal terminals. Light and variable flow this weekend will
yield to onshore breezes each afternoon, certainly impacting
coastal terminals but possibly impacting as far inland as
MHT/CON/AUG this weekend.
&&
.MARINE...
Short Term...Winds and seas will remain below SCA thresholds
tonight through Friday night.
Long Term...High pressure builds into the waters by the
weekend, departing east over the Atlantic next week. Thus winds
and seas are expected to remain below SCA thresholds. One
exception to the fairly quiescent conditions is the low
probability of a stray shower or storm forming over land and
tracking out over the waters with the ability to produce briefly
gusty winds. The greatest chance of that will be Sunday as a
weak cold front drops southward through the region.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR TERM UPDATE...Kimble
SHORT TERM...Cannon
LONG TERM...Casey
Area Forecast Discussion...UPDATED
National Weather Service Miami FL
839 PM EDT Thu May 13 2021
.UPDATE...
A cold front will continue to move southward through South Florida
this evening and should be in the Florida Keys by early Friday
morning. This will allow for the ongoing showers and storms over
the southern areas of South Florida to slowly dissipate through
rest of the evening hours. The weather should remain dry through
the overnight hours over South Florida, except for some showers
and a few storms over the Atlantic waters. Therefore, POPs will
continue over South Florida for the evening hours before going dry
for the overnight hours.
Rest of the forecast looks good at this time and no other changes
are planned.
&&
.AVIATION(00Z TAFS)...
VCSH will continue for all of the TAF sites, except for KAPF taf
where VCTS will remain until 02Z. After 02Z until 18Z Friday the
weather will remain dry, then VCTS for rest of Friday afternoon.
The only exception is KAPF where it will remain dry for Friday.
Ceiling and Vis will remain in VFR conditions but could fall into
MVFR or even IFR conditions with any showers or thunderstorms.
&&
.PREV DISCUSSION... (Issued 354 PM EDT Thu May 13 2021)
Mesoscale Discussion (valid through this evening)...
Bottom Line:
Isolated strong to locally severe storms capable of producing strong
gusty winds, heavy rainfall/localized flooding, and small hail will
be possible along the east coast metros this afternoon, though large
uncertainty remains. Present indications are that this threat will
be maximized between 2PM and 8PM today.
Technical Discussion:
A frontal boundary continues to slowly progress southward across
central Florida early this afternoon, with dense cloud coverage
mainly confined to areas north of South Florida -- where mid-level
height falls/large-scale ascent are being maximized amidst the
surface boundary. Ahead of the surface frontal zone, rich boundary-
layer moisture (lower 70s dewpoints) will be maintained, and pockets
of cloud clearing/thinning will result in diurnal destabilization of
the moist PBL -- yielding around 2000 J/kg MLCAPE across South
Florida, especially along the east coast where onshore flow will
continuously reinforce the inland boundary-layer with moist ocean-
modified air. Current mid-level water vapor loops and RAP analysis
show strengthening mid/upper-level westerly flow associated with an
eastward-advancing low-amplitude upper-trough, and this feature will
allow for both continued peripheral adiabatic cooling across South
Florida (increasing deep-layer instability and ascent) and
strengthening deep-layer wind shear as well. The strengthening deep-
layer shear (nearing 35 to 45 knots on the east coast) combined with
the above mentioned increasing buoyancy will support loosely
organized convection this afternoon -- primarily along the east
coast metros -- where strong gusty winds, heavy rainfall/localized
flooding, and small hail will be possible.
Present indications are that locally backed NNE low-level flow (on
the backside of a weakly developing surface low over the Atlantic
waters) below the strengthening westerly flow aloft will act to
elongate hodographs along the east coast, and these hodographs will
remain generally straight through the convective layer. The
primarily straight hodographs should support splitting cells and
associated cell mergers/messy storm modes, though one noteworthy
feature in the forecast hodographs is a slight anticyclonic bow in
the low-levels (associated with the NNE low-level flow) which may
tend to favor left-movers over right-movers upon cell splits. The
presence of both left and right moving cells will introduce the
potential for undercutting, which could reduce convective residence
time in the favorable surface-based effective inflow layer air.
However, if any cells can remain discrete within the favorable
surface-based buoyancy, the above mentioned hazards will become more
likely. In addition, the cell interactions could also yield
localized upscale growth (supported by favorable vertical wind
shear) which may also result in locally gusty winds as convective
cold pools amalgamate. The above mentioned cell mergers, rich
moisture/minimal CINH, and tall buoyancy profiles will support
locally heavy rainfall which could lead to isolated flooding along
the east coast metros into the evening hours -- especially with
repeated rounds of convection. The WPC has placed portions of the
east coast metros in a marginal risk of excessive rainfall to
account for this flooding threat.
At this time, the risk for isolated strong to severe storms appears
most likely along the east coast metros from Broward through Miami-
Dade County, though if left-movers become established and dominant
(as discussed above), Palm Beach County and inland areas could also
be at risk of seeing the previously mentioned convective hazards.
There is plenty of uncertainty in the convective forecast for today,
so be sure to keep up with the latest from NWS Miami.
SHORT TERM...
Scattered showers and thunderstorms will redevelop during the
overnight and early morning hours on Friday over the Atlantic
waters. A couple of these showers and storms may affect portions of
the east coast metro areas, however, most of the activity should
remain offshore. As the surface frontal boundary slowly moves
through the region on Friday, mid to upper level winds will start to
shift to a west northwesterly direction as the mid level trough axis
starts to shift into the western Atlantic. There will still be
plenty of lower level moisture to work with on Friday which will
allow for scattered showers and thunderstorms to redevelop during
the afternoon and early evening hours. The greatest chances of
showers and thunderstorms will continue to remain across the east
coast metro areas as well as portions of the interior. High
temperatures on Friday will generally range from the lower 80s
across the east coast metro areas to around 90 over the western half
of South Florida.
LONG TERM...
(Friday Night Through Monday)... High pressure will slowly move
eastward from the Southeastern United States into the Western
Atlantic Waters as a the stationary front remains over the Florida
Straits. This will keep the moderate to breezy easterly wind flow
over South Florida during this time leading to some showers over
the east coast and the adjacent Atlantic Coastal waters. The only
exception to this is on Saturday where the models are showing some
deeper moisture working around the high and across the region.
This will lead to an increase in moisture across South Florida
which in turn will lead to an increase in shower coverage
especially over the east coast metro areas. At this time, it still
looks to be showers only as the moisture will be in the low
levels of the atmosphere.
Highs will be in the lower to mid 80s east coast metro areas to
upper 80s west coast metro areas each day this weekend with lows
in the 60s except around 70 east coast metro areas.
(Rest Of Next Week)...
The long range models are showing the high to become nearly
stationary over the Western Atlantic waters, as the stationary
front starts to move slowly northward towards South Florida. At
the same time, there could be a broad weak low developing along
the front over the Florida Straits and moving northwest into the
Southern Gulf of Mexico. This will allow for deeper moisture to
work northward into South Florida especially for the middle to end
of next week leading to scattered showers and thunderstorms over
the region.
The long range models are also showing the PWAT values increasing
to around 2 inches by end of next week which is at the maximum
PWAT values for this time of year. Therefore, there could be some
heavy rainfall across South Florida late next week if this trend
plays out. Therefore, continue to monitor the latest forecast
through the weekend into middle of next week for the potential of
heavy rainfall for late next week across South Florida.
Highs will be in the mid 80s east coast metro areas to around 90
west coast metro areas each day next week with lows in around 70
except lower to mid 70s east coast metro areas. Heat indices next
week will be in the around 90 east coast metro areas to mid 90s
west coast metro areas.
AVIATION(18Z TAFS)...
A frontal boundary will slowly move through the local waters this
afternoon through Friday. Scattered showers and thunderstorms will
be possible throughout this time frame which could lead to locally
higher winds and waves. Marine conditions will gradually deteoriate
later tonight and through the upcoming weekend as a northeasterly
wind flow develops and increases. At the same time, a northeasterly
swell will be moving into the Atlantic waters and will remain in
place throughout the weekend. Seas over the Atlantic waters could
reach 7 feet through the first half of the upcoming weekend.
MARINE...
A frontal boundary will slowly move through the local waters this
afternoon through Friday. Scattered showers and thunderstorms will
be possible throughout this time frame which could lead to locally
higher winds and waves. Marine conditions will gradually deteoriate
later tonight and through the upcoming weekend as a northeasterly
wind flow develops and increases. At the same time, a northeasterly
swell around 2 feet will be moving into the Palm Beach Atlantic
waters and will remain in place throughout the weekend. Seas over
the Atlantic waters could reach 7 feet in the Palm Beach Atlantic
waters through the first half of the upcoming weekend. Therefore,
an SCA has been issued for the Atlantic waters of Palm Beach
County through Saturday evening.
BEACHES...
The risk of rip currents along the Atlantic Coast beaches will start
to increase on Friday and it will remain elevated through the
weekend, as a northeasterly flow increases and a northeasterly
swell develops in the Atlantic waters. The threat of rip currents
should also continue into most of next week, due to the easterly
wind flow over South Florida waters.
&&
.PRELIMINARY POINT TEMPS/POPS...
Miami 75 84 73 84 / 50 50 30 40
West Kendall 74 85 71 86 / 60 50 40 30
Opa-Locka 74 84 71 85 / 50 50 30 40
Homestead 73 84 72 84 / 60 50 40 40
Fort Lauderdale 75 83 73 84 / 40 50 30 40
N Ft Lauderdale 74 83 73 82 / 30 50 30 40
Pembroke Pines 73 84 71 84 / 50 50 30 40
West Palm Beach 73 84 70 82 / 20 50 30 40
Boca Raton 74 83 72 84 / 20 50 30 40
Naples 72 88 68 90 / 30 20 10 10
&&
.MFL WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory from 6 AM Friday to 8 PM EDT Saturday for
AMZ650-670.
GM...None.
&&
$$
Update/Aviation...BNB
Tonight/Friday and Marine...CWC
Friday Night through Thursday...BNB
Visit us at weather.gov/miami
Follow us on Facebook and Twitter at:
www.facebook.com/nwsmiami
www.twitter.com/nwsmiami
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1026 PM EDT Thu May 13 2021
.SYNOPSIS...
High pressure remains the dominant feature through early next
week.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 1025 PM Thu...Mid-level stratocu continues to stubbornly
hug coastal locales late this evening. RAP 700mb analysis
suggests this is being driven by weak mid-level Fgen right along
the Carolina coastline. Again raised sky cover trends in the
short term, expecting only slow clearing now per the HRRR.
Temperatures now dropping precipitously with good radiational
cooling, and T forecast is on track.
Prev disc...Varying amounts of cloud cover now with mid clouds
still hugging the coast from coastal Onslow County through the
central Outer Banks. Meanwhile, farther inland where most of the
day was sunny, a wide area of strato cu has formed with much
colder air aloft. The overall trend will be to clear the sky as
the clouds along the coast move offshore and the strato cu
diminish with the loss of daytime heating. With a clearing sky,
very dry air in place and light winds, temps will fall fast this
evening and bottom out in the lower to middle 40s inland with
50s along the coast.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH 6 PM FRIDAY/...
As of 345 PM Thu...After a chilly start, high pressure across
the Ohio Valley will control our weather Friday with plenty of
sunshine expected. With a very dry air mass in place (dewpoints
in the 40s), temps will recover quite nicely with highs into the
middle 70s.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
As of 345 PM Thursday...High pressure will build south and east
from the Ohio Valley Friday into Saturday as weak low pressure
remains well to the south of the area. Mid-level heights will
build as well. With deeper moisture shunted to our south, skies
will become mostly sunny for Friday through the weekend with
high temperatures warming well into the 70s, however lows will
be chilly, mainly in the mid/upper 40s Friday and Saturday
night, then into the 50s by Sunday night.
High pressure slides offshore early next week allowing for
warmer temperatures and increased humidity levels. Highs by
midweek will be into the lower and middle 80s. Despite the
increased moisture, the best mid/upper level forcing will
remain generally north of eastern NC, and most precipitation
will likely be driven by the daily sea breeze. Have opted to
just slight chance PoPs for early/middle next week.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
SHORT TERM /through 00Z Saturday/...
As of 745 PM Thu...High confidence in VFR conditions through
the period. Scattered cu deck dissipating with loss of heating,
leaving clear skies apart from a stubborn mid-level deck
hovering over Outer Banks and Crystal Coast. NE winds at 10 kt
will become light and variable overnight, and could see some
patchy fog mainly south of the Albemarle Sound with moisture
advecting off the waters.
Cu deck redevelops tomorrow late morning with NE winds around 10
kt or so, gustier closer to the coast.
LONG TERM /Friday through Monday/...
As of 320 AM Wednesday...High pressure building south from the
Ohio Valley will lead to generally clear skies and VFR
conditions through the weekend. Deeper moisture will lead to
increased cloud cover for Monday, but ceilings should continue
at or above 3000 feet.
&&
.MARINE...
SHORT TERM /Through Friday afternoon/...
As of 345 PM Thu...SCA continues for the ctrl/srn waters. N/NE
winds 15-25 kt will through tonight, strongest south of
Hatteras, with seas 3-5 ft north and 4-6 ft south. Northeast
winds continue Friday 15 to 20, as seas subside a bit by
afternoon.
LONG TERM /Friday night through Tuesday/...
As of 320 AM Thursday...For the coastal waters south of
Ocracoke Inlet, winds will be NE at 15 to 20 knots with gusts to
25 knots Friday with seas 4-6 feet. Winds then drop Friday
night through the weekend and will be NE 10-15 knots with seas
mostly 2-4 feet as high pressure settles along the East Coast.
As the high moves offshore Monday, winds will veer to mostly SE,
but remain fairly light.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...None.
MARINE...Small Craft Advisory until 5 AM EDT Friday for AMZ154-156.
Small Craft Advisory until noon EDT Friday for AMZ158.
&&
$$
SYNOPSIS...MHX
NEAR TERM...EH/MS
SHORT TERM...EH
LONG TERM...CTC
AVIATION...CTC/MS
MARINE...EH/CTC/TL
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 309 PM CDT Thu May 13 2021
Early afternoon analysis showed a weak shortwave trough sliding
through the northwest flow aloft, bringing some light showers to
portions of northeast Nebraska. These have been on a dissipating
trend all day and will continue to do so through the remainder of
the afternoon. At the surface, southerly flow/warm air advection
was in full swing on the back side of surface high pressure
departing to the east. Temperatures as of 3 PM were generally in
the mid to upper 60s, though a few spots had cracked that 70
degree mark.
Tonight, another shortwave trough will slide southeast through
the area, with the nose of the low level jet/moisture transport
pointed into central and then eastern Nebraska. This will lead to
additional shower development, along with potentially a few
thunderstorms given perhaps a few hundred J/kg of MUCAPE sneaking
into the forecast area. Would think with such little instability,
especially this far east, it would be tough to get much in the way
of strong storms, much less severe, but the HRRR has remained
persistent in producing some 35 to 45 kt gusts on the northern
edge of the convection. While forcing seems decent between the
aforementioned low level jet/moisture transport and shortwave
energy, along with continued warm air advection, would really
expect to see a stronger moisture transport signal or higher
MUCAPE values given the strength of the convection depicted by the
HRRR (and most of the other CAMs). One "positive" going for
potential stronger winds is steep low level lapse rates, but by
the time the storms get this far east it may be tough to get any
of those stronger winds through the surface inversion. Something
to definitely keep an eye on though as we go through the evening.
We`ll remain in an unsettled, but warmer pattern through the
remainder of the forecast period. A closed low will move onshore
in the Friday/Saturday timeframe and shift into the Desert
Southwest over the weekend. Meanwhile, a surface boundary looks to
set up west to east somewhere near or south of the KS border,
oscillating north and south each day while various bits of
shortwave energy eject out of the aforementioned low and interact
with the boundary to produce showers and storms. Really the name
of the game in forecasting the heaviest precip will be finding
where that boundary sets up each day, which will likely be
impacted by the previous night`s/morning`s convection. Model
consensus suggests it stays south of the forecast area, which
means we`ll have a tough time getting much in the way of
instability this far north. Therefore, wouldn`t anticipate much
for a severe weather threat, but will likely see periodic showers
with occasional thunderstorms, though no day looks like a washout
through at least Tuesday. Otherwise, temperatures look to
consistently top out in the 70s for most of the area from Saturday
onward.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 625 PM CDT Thu May 13 2021
Showers and thunderstorms expected to move through the area late
this evening and overnight, though generally expect VFR conditions
to prevail until Friday morning. T-storms, while isolated, could
lead to brief MVFR conditions. Powerful downdrafts are possible.
Ceilings will trend downward Friday morning and are expected to
become MVFR at KOFK. Showers could linger at KLNK and KOMA
through the morning, with guidance persistent in developing some
visibility reductions near and east of the Missouri River.
Otherwise, winds will remain southerly/southeasterly at about 9kts,
gusting in the 20 to 25 kt range Friday morning.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...CA
AVIATION...Nicolaisen
Area Forecast Discussion
National Weather Service Riverton WY
448 PM MDT Thu May 13 2021
.SHORT TERM...(This evening through Friday night)
Issued at 135 PM MDT Thu May 13 2021
Today continues in the transition pattern between the longwave trough
to our east and the ridge to our west. A weak shortwave moving
across the north today is bringing virga showers and some cloud
flashes across parts of Johnson County and some more organized
storms across Montana. Some convective showers and virga showers
have also developed along the spine of the Wind River Mountains
early this afternoon. Otherwise, not much to discuss in the forecast
through tonight. Latest runs of the HRRR have brought increased
chances of isolated showers across the north overnight, but there is
not much confidence in exact location or timing of these showers.
Breezy winds at the usual areas this afternoon will continue until
around sunset. Temperatures will continue to be slightly above
normal today and tomorrow.
Tomorrow, breezy winds will once again occur across the usual areas
as the ridge pushes into the region. Winds will not be as breezy as
today. Another shortwave will bring chances of scattered showers and
thunderstorms through the afternoon. Tomorrow will certainly see
greater chances of showers and thunderstorms than today. SPC is
going with a general thunderstorm outlook across the region, with
the exception of the far southwest part of the state. These showers
and thunderstorms will be isolated in nature, so it is difficult to
pin down exact locations of the showers. Went with a blend of CAMS
and the HRRR to get general PoPs and some greater PoPs across the
north to account for showers coming off of the Absarokas and
Bighorns. Shower and thunderstorm activity will diminish after
sunset when diurnal heating ends. Overnight, mostly cloudy skies and
lows staying pretty well above freezing for most areas.
.LONG TERM...(Saturday through Thursday)
Issued at 135 PM MDT Thu May 13 2021
The northern portion of a splitting trough will pull across the
Northern Rockies Saturday and Saturday night. The southern portion
will be a cut off low which is progged to settle into southern
California by 12Z Sunday. The associated weak cold front is expected
to pull across the forecast area Saturday night. A shortwave pulling
across the area in the northern stream trough in combination with
the right-entrance region of an upper jet and weak instability will
give good chances of convection across the area Saturday afternoon
and evening. The Convective Available Potential Energy (CAPE) is
tall, but skinny which would suggest updrafts would not be too
impressive.
Overall forcing will much weaker Sunday as the upper low over
southern California shifts slowly east into the southern Great
Basin. However there enough instability for some diurnal convection
especially over and near the mountains. The GFS is most aggressive
with convection, but the drier NAM and ECMWF seems to be more
reasonable.
The southern low will gradually shift east into the Four Corners
Region or tad south of that by 12Z Tuesday, and then expected to
push into the southern High Plains Tuesday. At the same time the
forecast area looks to be in a light and chaotic flow in the mid-
upper levels both Monday and Tuesday. There could be a light
easterly flow over the east with a weak convergence zone over the
far eastern zones. In addition there is also relatively weak
instability so diurnal convection remains possible both days, but
again the GFS seems to be overdoing the coverage of convection.
Late Tuesday into Tuesday night, global models show a trough pushing
into the Pacific Northwest. On Wednesday and Wednesday night this
trough is expected to swing eastward across the northern
Intermountain West and extreme northern Rockies. There is
disagreement on how far east/southeast the associated cold front
will push across the forecast area, but overall there looks to be
chances of convection Wednesday, with possibly dry slotting on
Thursday on the southern part of this trough.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday)
Issued at 430 PM MDT Thu May 13 2021
Very isolated early evening showers are expected across the area
with the best chance over the north. Confidence is not high enough
to mention at any terminal at the moment. Otherwise, VFR conditions
with scattered to broken mid-level cloudiness are expected through
Friday morning. Some models show the possibility of showers
overnight into Friday morning over the north, but again coverage and
confidence is not high enough to include VCSH at KCOD or any other
terminal. A much better chance of showers and a few thunderstorms
are expected Friday afternoon. Will have VCSH at all terminals
Friday afternoon to account for this activity. Breezy west to north
winds this afternoon across much of the area will weaken around
sunset.
&&
.FIRE WEATHER...
Issued AT 135 PM MDT Thu May 13 2021
Smoke dispersal will be good through this afternoon with breezy
winds in the usual areas. Tomorrow will see much of the same, though
winds won`t be quite as breezy. RHs tomorrow will be between 15 and
20 percent across the south with RHs above 25 percent across the
rest of the region. A few isolated showers today mainly across the
Wind River mountains and Johnson County off of the Bighorns.
Tomorrow will see greater chances of showers and thunderstorms,
especially across the north tomorrow afternoon. Saturday will see
more widespread showers across the region. Ridging with embedded
scattered showers and possibly thunderstorms will continue to be the
story into the beginning of next week.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...Fisher
LONG TERM...Murrell
AVIATION...Murrell
FIRE WEATHER...Fisher