Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/02/23

Area Forecast Discussion

National Weather Service Denver/Boulder CO

 726 PM MST Wed Mar 1 2023

.UPDATE...
Issued at 710 PM MST Wed Mar 1 2023

Major changes in the PoPs through overnight as lack of forcing,
the Denver cyclone shifting winds, and lack of moisture has left
us with dusting for some areas. Additionally, the trough axis has
shifted even more south meaning there will be another decrease
snow amounts this forecast package update. The single persistent
snow band over parts of Boulder, southern Weld county, and
Broomfield will likely diminish by 9PM. Flurries are possible
through midnight as snow showers remain south of our region.
Although, a few light snow showers could occur after midnight for
the Palmer Divide and Park County valleys but no accumulation
above half an inch expected. Mostly cloudy skies continue for all
areas tonight.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 114 PM MST Wed Mar 1 2023

Complex scenario has developed early this afternoon over the portions
of Northern Colorado. Moderate to heavy snow showers have developed
over portions of the northern urban corridor...mainly from Denver
International Airport and extending northward through portions of
Weld and Larimer counties. ACARS soundings over Denver showed
near moist adiabatic airmass with healthy near east to
southeasterly upslope winds to 25kt. Aloft, there is a lead upper
wave which is ahead of the main low over California with moderate
QG ascent (~15mb/hr). In addition, Denver cyclone is intensifying
over Denver with strong southeast winds over south/east Denver
while northerly winds are wrapping around the low across west
Denver area. Of course the southeast, downsloping winds are
keeping things drier south of Denver and across the Palmer Divide.

The heavier snow showers are beginning to dissipate but still should
see snow showers increasing again later this afternoon through
early evening with mesoscale forcing from the cyclone and still
weak ascent aloft. Much of the snow shower activity will diminish
by midnight with more neutral forcing aloft behind the wave and
light downsloping flow developing. Overall, still looks like up to
2 inches of snow from this afternoon and evening but amounts
rather sporadic with more convective nature.

The next system to contend with is the main upper low over
California but is expected to track south of Colorado through
southern New Mexico. Any impacts with this storm will be over
Southern Lincoln county, and even that may be a stretch as the GFS
has the band even further south than Lincoln county. Much of
Northern Colorado will be dry on Thursday under subsident large
scale flow.

.LONG TERM...(Thursday night through Wednesday)
Issued at 114 PM MST Wed Mar 1 2023

Thursday night through midday Friday, a short wave ridge will
move across the region with drier air associated with weak
subsidence. The next system will brush across northern CO Friday
afternoon and evening. The flow aloft will remain zonal with a
brief period of weak-moderate qg ascent impacting the mountains in
the afternoon and the urban corridor/ne plains around 00Z Friday
evening. 700/500 mb lapse rates won`t be too bad at that time,
around 7-7.5C/km. The main question will be how much moisture will
be available in the lower levels. The GFS is a little more
generous in comparison to the other model data. For this reason,
we will keep the pops similar to what they have been, in the
50/50 category. SREF plumes for Denver generate around one half
inch of snow Friday evening. Confidence in potential snowfall
amounts is low to medium, but can`t rule out a brief period of a
trace to 2 inches for Denver mainly east of I-25 and areas south
and east. The progressive pattern will carry into the weekend.

A strong southwesterly flow aloft aloft will set up over CO, with a
500 mb trough over the Pacific Northwest coast.  The jetstream west
the trough will drop out of the Gulf of Alaska then stretch across
CA and into the Central Rockies. This will result in a series of
weak systems moving across CO.  Increasing moisture and relatively
stable lapse rates will result in light snow over the mountains this
weekend, with gusty downslope winds and warmer temperatures on the
plains for Sunday.  There could be localized parts of the southern
Front Range Foothills could see elevated fire weather conditions
Sunday afternoon where there will be no snow cover.  Much of next
week will be cool and unsettled.  With the jetstream over CO there
will be a steady stream of Pacific moisture continuing to bring
periods of light to moderate snowfall in the mountains. The trough
over the northwestern U.S. will shift inland with a better chance
of snow spreading into the northeast plains of CO by Wednesday of
next week, what a surprise!

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 440 PM MST Wed Mar 1 2023

Looks like snowfall chances are trending downwards and HiRes
models cannot keep up. The cyclone has also delayed winds near the
terminals from shifting northerly. Thus it is possible
northwesterly winds will occur briefly sometime after 03Z then
shifting south as snow showers push southeastward of all
terminals. VFR conditions are possible for all terminals through
the TAF period. Drainage winds are unlikely as SCT to OVC skies
will remain. There is not high confidence in wind direction after
17Z. Most guidance favors southeast at KAPA and more easterly at
KBJC and KDEN so keeping those directions for now. Higher ceiling
are possible tomorrow reaching 25k trending mostly SCT.


&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...AD
SHORT TERM...Entrekin
LONG TERM...Cooper
AVIATION...AD



Area Forecast Discussion

National Weather Service Raleigh NC

 940 PM EST Wed Mar 1 2023

.SYNOPSIS...
A weak front stretching across western and southern North Carolina
will lift slowly northward through North Carolina as a warm front
late tonight. A weak cold front will follow, shifting eastward
through the area Thursday morning before stalling over the Carolinas
and holding in place through Friday. A strong low pressure system
crossing the Ohio Valley and Great Lakes regions will drag a cold
front through the area late Friday night.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 940 PM Wednesday...

...Strong storms possible in the NW Piedmont later tonight...

The primary weather focus this evening for us is the areal expansion
of the marginal (level 1 of 5) risk of severe storms by SPC into our
NW Piedmont for later tonight, mainly a hail threat. The latest
surface analysis shows the weak frontal zone / edge of stable pool
extending from far NE NC along the S edge of the CWA and central
Foothills into far NW NC. The front then continues to a prominent
low over OH, with a trailing cold front along the IN/KY border and
through the MO Bootheel to AR/TX. A prefrontal trough is evident in
the warm sector from N LA across N MS into central TN. Between these
two latter features, widespread strong to severe convection persists
from AR and N MS/AL into central/E TN/KY. The mid level flow over
the Mid South/Carolinas remains fairly flat with a gentle
anticyclonic curve (marred only by an MCV which models depict
crossing VA/NC with the convection late tonight/Thu morning). We`ve
briefly lost much of the afternoon cloud cover which has shifted E,
however the preconvection cloud shield is already rushing into W NC.
The main challenge tonight is determining what will happen to the
ongoing convection as it shifts eastward into the Mid Atlantic
region overnight. The dynamic forcing for ascent will remain
somewhat muted, with only the MCV evident through the mid levels,
and the vigorous jet-induced upper divergence currently to our W
over TN into N MS/AL is expected to weaken as it heads eastward
overnight. The thermodynamic environment to our W and WSW supporting
the ongoing storms is decent, with moderate CAPE and fairly steep
mid level lapse rates noted on 00z soundings at JAN/BMX/FFC and
recent ACARS soundings near BHM. But the better (6+ C/km) MLLRs will
remain suppressed just S of NC and push entirely to our S overnight.
The 925-700 mb LRs are nearly 6.5 C/km over central NC currently but
are projected to shift to our E overnight. Beneath this layer, the
surface-based stable pool is expected to linger well into tonight
but weaken as it`s overtaken by increasing SSW flow (although
confidence in a nocturnal mix-out of a stable pool over the Piedmont
is usually fair to low, and I wouldn`t be surprised if the models
are wrong and the weak stable pool holds through daybreak). Chasing
the better thermodynamic environment will be the strengthening wind
field, including the arrival of a 70-80 kt mid level jet across
NC/SC very late tonight concurrent with a 40-50 kt SW 850 mb jet
nosing into the NC Piedmont. While the features don`t line up
temporally (the already-low CAPE exiting as the wind field
strengthens and hodograph lengthens and straightens), given this
robust deep layer shear, there is enough potential for a strong
storm to survive the mountains (and overall nocturnal stabilization)
for a risk of storms late tonight into Thu morning, mainly across
the N two-thirds of the CWA, according to CAM consensus including
HREF paintballs. I don`t have a lot of confidence that we`ll see
hail tonight, much less severe hail, given RAP projections with
little to no CAPE overnight along with the lack of ground truth
reports from upstream in the last few hours. Nevertheless, the risk
is non-zero, and have updated the Hazardous Weather Outlook to
include this risk. Otherwise, with minor temporal and spatial
adjustments, have retained the W-to-E trend of pops toward high-
chance (far S) to categorical (N) through the rest of the night and
into Thu morning, with an hour or two potential for isolated thunder
added in most areas. Temps are expected to move little tonight, and
perhaps rise a few degrees, with the incoming blanketing clouds and
higher dewpoints advecting in. Temps for the rest of the night will
range from the upper 40s to around 50 N to the lower 60s S. -GIH

Earlier discussion from 230 PM: Water vapor satellite showed a broad
ridge across the Caribbean providing nearly zonal flow across
central NC, an upper low lifting northeast across the Midwest and a
deep upper low across southern CA. Surface observations displayed a
warm front stretching from the southern Piedmont to the central
Coastal Plain. The warm front will continue to lift north across the
region this afternoon. This evening will be dry, then a prefrontal
trough and shortwave aloft will develop an area of showers and
isolated thunderstorms from west to east across the region tonight.
Conditions should be stable enough to prevent storms from becoming
strong, however lightning is expected as they traverse the region.
Temperatures will drop to the low-50s N to mid-60s S by late
evening, then become fairly steady the rest of the night as cloud
cover thickens and precipitation develops. Rainfall amounts will
range from just over one-half inch for the northern half of central
NC to near two-tenths near the SC border.

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
As of 300 PM Wednesday...

Broad upper ridging will remain anchored across the Caribbean
Thursday, and with a deep upper low digging across the Desert
Southwest. A strong upper jet will develop between these features,
creating several rounds of precipitation that will round the ridge
and move from TX the Carolinas starting Thursday. At the surface, a
prefrontal trough will move southeast away from the region in the
morning, then a cold front will sag southeast across the area in the
evening. Showers will linger near the NC/SC border throughout the
day as the trough slowly stalls, with areas near and north of the
Triangle having a temporary break in the rain in the afternoon.
Showers will then redevelop in the evening as the next cold front
moves towards the region, with coverage expanding across all areas
overnight as isentropic ascent develop. Rainfall amounts through the
period will generally be less than one-half of an inch. Highs: 70s.
Lows: mid-40s N to low 60s S.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
As of 135 PM Wednesday...

Friday will be the most impactful portion of the forecast through
Wednesday, bringing a chance for severe weather, mainly across the
western Piedmont with a decreasing threat with eastward extent.

A closed low over the ArkLaTex region Friday morning will lift
northeast into the OH Valley and Lower Great Lakes region by 00z
Saturday, transitioning into an open wave by 12z Saturday over the
Northeast. At the surface, a strong surface low pressure system over
the Lower MS Valley will quickly move into the OH Valley by 7PM
Friday. Strong, warm southerly flow will pull a remnant boundary to
our south through the area by late Friday evening. There is still
fairly considerable timing differences in regard to the northward
progression of the boundary as a warm front. This boundary will be
the greatest forecast concern as along and south of this boundary
will be the primary focus for severe weather. Latest 12z guidance
shows the front anywhere from the NC/SC border (12z NAM), bisecting
central NC (CMC/Euro), or north of the NC/VA border by 00z. The
afternoon update focused more heavily on the middle-of-the-road
solution that the Canadian and Euro are suggesting, given stratiform
rain across the northern tier of counties earlier in the day may
slow the northward progression Friday afternoon/evening. Before the
convective line approaches the area, locations south of the warm
front will likely experience strong southerly winds 15-25 mph with
gusts 30-40 mph and temperatures soaring into the upper 70s to
low/mid 80s; while areas north of the front will see 10-15mph winds
and highs in the upper 50s to low 60s.

Convective evolution is still fairly uncertain as timing of
convection will become increasingly unfavorable within the diurnal
cycle and drier air aloft nipping at the heels of the convective
line. Additionally, deep layer forcing for ascent will be well to
the north of central NC as the closed low progresses into the Great
Lakes Region. However, there is enough evidence with surface based
CAPE 200-700 J/kg co-located with impressive 0-6km shear of 70-85kts
and 0-1km shear of 35-45kts, to mention the threat for damaging
straight line winds with the convective line and embedded tornadoes,
especially west of the Raleigh area. Dry air in the mid-upper levels
is expected to overspread the area after 06z and limit the deeper
convection with mainly showers as the front moves through the
remainder of the area.

Behind the front, surface high pressure builds in through Monday
afternoon bringing drier conditions and only slightly above normal
temperatures. Return flow around the high as it shifts offshore
Monday night will raise temperatures 10-15 degrees above normal
before another cold front brings cooler, drier air back into central
NC through Wednesday

&&

.AVIATION /00z THURSDAY THROUGH MONDAY/...
As of 615 PM Wednesday...

TAF period: While the TAF period will start with calm conditions or
light wind out of the south, an area of rain will move in from west
to east after midnight and last through mid-morning. MVFR conditions
are expected at most terminals, although the lower clouds appear
likely to remain north of FAY and a brief period of IFR ceilings
cannot be ruled out at RWI. Confidence in a thunderstorm occurring
late tonight around sunrise is low, but decided to keep it mentioned
in the TAF since its removal might be interpreted as no chance of a
thunderstorm. Conditions will improve by late morning, both with a
return to VFR conditions and rain moving to the east. In addition,
some marginal LLWS still remains possible near FAY, but should not
be a threat at other sites.

Outlook: A few cold fronts approaching the region will increase
precipitation and storm chances Thursday night into Friday, with
associated sub-VFR conditions. Strong SW winds with frequent gusts
of 30 to 40 kts are also expected Friday ahead of the cold front.

VFR conditions will return Friday night and should remain
predominately VFR through the weekend into early next week.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...Hartfield
NEAR TERM...Hartfield/JJT
SHORT TERM...JJT
LONG TERM...Swiggett
AVIATION...Green/JJT