Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/22/21
Area Forecast Discussion
National Weather Service Denver/Boulder CO
840 PM MDT Wed Apr 21 2021
.UPDATE...
Issued at 840 PM MDT Wed Apr 21 2021
And, just like that the heavy snow bands break down as some sort
of a westerly surge pushed across the Front Range. The more
intense snow is trying to hang on over Denver and the southern
foothills, but even there it seems a stronger downslope flow
component is developing now and overcoming any synoptic support.
Also, road conditions have caught up as snow intensity has
decreased so we`ll be canceling the short fused Advisory earlier
issued for the foothills. The tricky forecast has done it`s number
tonight. There is still large scale lift over us, but the
majority of the snow showers should be organizing over the
mountains overnight as the west/southwest flow aloft strengthens -
lending more upslope to the mountains and stronger downslope for
the plains.
UPDATE Issued at 722 PM MDT Wed Apr 21 2021
Given the impacts along the I-70 Corridor already this evening,
and up to another 3 inches expected with further cooling and more
widespread impacts, we opted to issue a Winter Weather Advisory
for the foothills. There are still some very heavy localized bands
of snow, and those will likely continue for the next couple hours.
Some indications of drying occurring farther north, but the large
scale lift remains in place, as well as this tricky forecast
tonight. We think areas along/south of I-70 may do well for the
next few hours. HRRR keeps drying things out too fast. NAMNEST
seems a more reasonable solution with the favorable frontogenesis
and forcing from the weakly coupled jet.
UPDATE Issued at 517 PM MDT Wed Apr 21 2021
Tricky forecast shaping up this evening with a persistent but
fairly narrow band of heavier snow streaking through the northern
portions of Denver. There is a pretty healthy band of 700-500 mb
frontogenesis, as well as a weakly couple upper level jet. We
would hope these bands start to move to spread the accumulating
snowfall out, but will have to watch this closely since the upper
level frontogenesis and upper level forcing really doesn`t move
much through the course of the evening. There are some 1-2 inch
amounts in the forecast, but we`ve already nudged things in the
observations direction, and can`t rule out a few 3-4" reports if
these bands stay nearly stationary.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 221 PM MDT Wed Apr 21 2021
The closed low has transitioned into an open wave and is moving into
the Great Basin. The jet is circumventing the base of the trough and
is pushing northeast into central Colorado. This, combined with
continued QG ascent and enhanced moisture will help to continue
light snow over the region through the overnight hours. In the mid-
levels, the 700 mb low will transition to the east across the CO/KS
border helping to deepen southwest winds through the column by
midnight. This will aid in gradually diminishing the snow through the
early morning hours Thursday for the Denver metro area south to
north. At the surface a weak cyclone formed helping to increase
southeasterly flow and a subsequent Denver Cyclone. This combined
with a break in the clouds over Park and portions of southern
foothills/metro area could help to increase convection and snow
potential for the late afternoon timeframe. Increased potential for
this area as well as areas along and West of I-25. With the
prolonged lift have also increased snow potential for the eastern
plains slightly into the overnight hours with amounts are still
considered to be on the lower end. For elsewhere, still anticipating
3 to 6 inches for the mountains overall with 1 to 3 inches for the
foothills, and 1 to 2 inches for the high valleys and areas west of
I-25. The eastern plains could see a trace up to 1 inch by Thursday
morning mainly on grassy areas. Lows overnight will be slightly on
the more mild side with the increased cloud cover and southwest WAA
into the early morning so will stay in the upper 20s on the plains
and teens in the mountains.
On Thursday, the lift provided by the aforementioned wave and
accompanying jet will be transitioning east and becoming elongated
through the day. The southwest flow will help to dissipate clouds
into the early afternoon but a piece of energy will drop south and
provide enough lift for some diurnal convection by the afternoon.
Current models show 200-450 j/kg of CAPE across the northern
mountains and foothills by the afternoon. Albeit weak, it will
provide a chance for some showers, especially over the ridges and
eastern slopes of the Front Range. With the current temperature
profile expect any precipitation to fall as snow in the mountains
with mostly rain over the plains with a possible mix in the
foothills. Highs will be able to reach into the lower to mid-50s by
the afternoon with 30s and 40s in the high country.
.LONG TERM...(Thursday night through Wednesday)
Issued at 221 PM MDT Wed Apr 21 2021
Showers will be winding down across the higher terrain Thursday
evening. By Friday the trough axis will be overhead and moving to
our east, with only weak QG forcing around. Still, there looks to
be just enough lift, moisture, and instability to see a renewed
round of showers and a few thunderstorms. Most of this activity
will be confined to the higher terrain, but some of this activity
could spread into the plains. Temperatures on Friday are a bit
warmer... so any precipitation will likely be rain across the
plains and the lower half of the foothills, with snow levels near
7500 feet Friday afternoon. Across the higher mountains, another
1-3 inches of snow is possible in the most persistent showers.
Warmer and drier weather is on the way for the weekend as upper
ridging builds into the region. Saturday will see temperatures
back in the 60s for the first time in a while, with Sunday likely
to reach the 70s. Winds will increase a bit this weekend as well
as southwesterly flow aloft gradually strengthens.
Monday should be another warm day as our next storm system takes
its time reaching the area. Forecast guidance varies a bit with
the speed of the approaching system, but the current forecast
leans towards the slower (and warmer) side of the ensemble
guidance. The next system arrives by Tuesday with increasing PoPs
and cooler temperatures Tuesday and Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 840 PM MDT Wed Apr 21 2021
Snow showers will be tapering off through 04Z and should be mostly
over, or just flurries by 06Z. Concern will then shift toward
patchy but possibly dense fog (1/4SM FG) toward early Thursday
morning. That potential exists due to narrow T/Td spreads and a
weak Denver cyclone expected to develop. That would favor light
W/NW winds redeveloping at KDEN after 12Z with possible fog
development at that time. We`ll opt for a TEMPO 1/2SM FG group
for now between 13Z and 15Z. Otherwise, VFR conditions may
redevelop either side of that with a light downslope
south/southeast flow 06Z-12Z, and then daytime heating and mixing
after 16Z-17Z Thursday.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Barjenbruch
SHORT TERM...Bowen
LONG TERM...Hiris
AVIATION...Barjenbruch
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
627 PM CDT Wed Apr 21 2021
...Aviation Update...
.DISCUSSION...(This evening through Wednesday)
Issued at 244 PM CDT Wed Apr 21 2021
Afternoon cumulus will gradually diminish across the area through
the late afternoon, leaving mostly clear skies for this evening.
Winds will also go light and variable, allowing temperatures to
dip quickly into the 30s. A shortwave trough will bring increasing
cloud cover and southerly winds by Thursday morning which should
ultimately keep low temperatures 5 to 10 degrees warmer than last
night.
This trough will also bring some light precipitation to the area.
This will be mostly in the form of rain, but we cannot totally
rule out some snow/flurries in western areas Thursday morning.
Regardless, no snow accumulation is expected. In fact, many short
term models, including the HRRR and RAP are rather stingy with
precipitation of any kind and would develop the most widespread
and persistent rain over eastern portions of the area Thursday
afternoon/evening. Therefore, we have maintained only chance PoPs
and very light QPF (less than 0.10"). Even with only light rain
expected, strong south wind gusts to around 35 MPH will make for a
rather unpleasant day.
Dry weather returns to the forecast for Friday/Saturday. There
will be another shortwave moving through the central Plains, but
any precipitation is likely to remain just south of the forecast
area. High temperatures are expected to reach the low 60s, which
is pretty close to normal for this time of year.
Dry and increasingly warm weather returns for the beginning of
next week as we see continued height rises aloft. Highs should
reach the 70s on Sunday and will likely reach the 80s on Monday as
southerly flow increases ahead of a deepening trough over the
western CONUS. Because of this warmup and increasing wind, western
portions of the area could see heightened fire weather concerns,
especially on Monday.
This aforementioned trough then is expected to move through the
central Plains in the Tuesday/Wednesday timeframe. Exact details
remain pretty uncertain, but it appears that at least a few
thunderstorms are possible ahead of this system Tuesday and
Tuesday night. Temperatures are also expected to trend back closer
to our climatological normals through the middle of next week
(highs in the mid 60s).
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 621 PM CDT Wed Apr 21 2021
An upper level disturbance crossing the Central Plains could bring
some light precipitation (rain/snow or sprinkles/flurries) to the
terminals after 12Z Thurs with little if any accumulation
expected. Cloud cover will also increase/thicken heading into
Thursday and have kept cigs at VFR however have included
scattered MVFR clouds as well. Southerly winds will ramp up during
the daytime with gusts of 30-35kts expected.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
DISCUSSION...Mangels
AVIATION...Fay
Area Forecast Discussion
National Weather Service Gray ME
1026 PM EDT Wed Apr 21 2021
.SYNOPSIS...
Low pressure and a cold front will cross the region this evening
resulting in showers and isolated thunderstorms. The low
will drift east of the area overnight tonight resulting in a
strengthening northwest wind, colder temperatures, and scattered
rain and snow showers on Thursday. On Friday high pressure will
build south of the region resulting a some moderation in
temperatures however winds will remain gusty. This area of high
pressure will result in improved and warmer weather for Saturday
before another area of low pressure returns the likelihood of
wind and rain over the area on Sunday.
&&
.NEAR TERM /TONIGHT/...
1000 PM Update...Expanded the winter weather advisory across the
remainder of zones along the international border. Although most
of the heaviest precipitation has moved east and out of the
forecast area this evening...there is still one batch of rain
and snow moving through Maine at this hour. This will provide
one final burst of moderate to heavy snow over northern zones
before upsloping becomes predominant through tonight and into
tomorrow. Temperatures continue to rapidly cool into the 30s...
with the 20s starting to make an appearance over northern zones
on a northwest wind. Also made some changes to temperatures and
PoP tomorrow; HREF shows fairly expansive cumulus and stratocu
development tomorrow in strong cold advection which should slow
the warming trend during the first half of the day. Additionally
the steep lapse rates and weak low/mid-level instability likely
leads to autoconvective showers tomorrow, although dry low
levels will still make it tough for anything to reach the ground
over the coastal plain.
700 PM Update... Ended up making more changes with temperatures
quickly crashing into the 30s over New Hampshire... for
instance Rochester sits at 48 degrees, Laconia at 39, and
Lebanon at 34. This has led to some pockets of locally moderate
snowfall.
530 PM Update...
Only some minor changes using latest temperatures observations.
At this hour low pressure is approaching the Gulf of Maine with
an area of convection in its wake. This convection, while
producing steady lightning over New Hampshire along with
scattered wind gusts 30-40 mph and small hail, has trended
steadily these last couple hours and is expected to trend down
by 7 PM or so.
Previously...
Pattern: Shortwave trough along the eastern edge of a much
larger scale trough at H5 is moving north and east into New
England as of this afternoon with attendant surface low pressure
moving into southern New England. This low is riding north and
east along a very strong baroclinic zone with T8s ranging nearly
20C from Lake Ontario to Nantucket. This implies strong
mid/upper level flow with near term RAP analyses and forecasts
showing a 80-90kt coupled jet on the 1.5PVU surface.
Through this evening: Initial round of rain and embedded thunder
is moving north and east...with temperatures having dropped
10-15F in it/s wake. Regional GOES 16 imagery shows some
clearing west of this activity...providing perhaps an hour or
two of heating before the next convective line associated with
the surface cold front and low center arrives. Lightning is
expanding across the Berkshires with 500 J/kg of MUCAPE ahead of
this line. This line will be combating decreasing instability as
it moves north and east...but there is a threat of a
strong/severe storm along our far southern border /along and
south of a EEN-MHT-PSM line/ through 6pm.
Otherwise...temperatures will start to fall rapidly from west to
east through 8pm as the cold front moves across the forecast
area.
Tonight: Cold front quickly sweeps east with precipitation
ending during the evening hours over southern areas. Further
north...as cold air arrives...expect rain to changeover to snow
and linger longer over the mountains...with some light
accumulations through daybreak. Deepening low pressure to our
northeast and strengthening cold advection will cause winds to
strengthen across the area as we move towards daybreak with lows
falling into the 20s in the mountains and foothills...and close
to the freezing mark further south and east.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
High Impact Weather Potential:
* Wind gusts approach advisory levels on Thursday.
* Accumulating snow comes to an end over far northern areas.
Pattern: Longwave trough axis shifts east and overhead through the
short term period as low pressure strengthens upon departing
the northeast. Primary forecast concerns center on 1-the
continuation of mountain snow shower activity and expected
accumulations and 2- strong northwesterly winds given an
impressive gradient on the western flank of the departing low.
Thursday: West-northwest winds will primarily be gradient-driven
with cold advection pretty much having ended by daybreak and little
isallobaric assistance. Still..the H9 gradient supports winds 30-
40kt at this level which with deep boundary layer mixing should
allow much of this to mix to the surface. Model soundings support
gusts 30-40 mph and changed little from inherited forecast. Given
some of the other missing ingredients...expect that we`ll fall
a bit short of wind advisory criteria and will hold off on
issuing any headlines. T9s will remain below 0C through the day
which translates to highs in the 30s across the north and low to
perhaps mid 40s across the south...with wind chills about 10F
colder than this given the strong winds.
Upslope snow showers will gradually wane through the day
Thursday with another 1-2" along the Canadian border.
Thursday Night: Cool cyclonic flow will continue through the night
with continued drying bringing mountain snow showers to an end. It
will remain breezy given gradient between 975 mb low over eastern
New Brunswick and high pressure over the southeastern US. This full
mixing should keep temperatures from going too low, but the airmass
itself will be cold enough to allow lows to fall into the 20s in the
mountains and right around the freezing mark to the south.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
A rather active weather pattern to continue in the long range
forecast period. Early in the period low pressure over the Maritimes
will continue a cyclonic flow of cool air over the region. While it
will not be as windy as the previous day, winds will still be
gusty on Friday. While most of the area will be dry, with
cyclonic flow aloft and an upslope wind direction there may
still be some isolated shower activity over the mountains during
the morning. On Saturday, high pressure located to our south
will briefly nose in resulting in warmer temperatures and dry
weather. By Saturday Night low pressure ejecting NE out of the
Tennessee Valley will rapidly strengthen and move to the Mid
Atlantic Coast. Clouds will overspread the region overnight
Saturday with rain developing by daybreak over NH. As the low
continues to strengthen over the Southern Gulf of Maine, the
rain shield will overspread Western Maine Sunday morning and may
become locally heavy during the day. Rain will taper to showers
Sunday Night as the low moves NE of the area. As colder air
moves in, mountain areas will see the chance of snow showers
returning. GFS-ECMWF-Canadian models agree in the over all
evolution of this pattern but there are some subtle differences.
ECMWF is the strongest and furthest west with this track. GFS
is a bit weaker and further east and the Canadian is faster and
further NE with the system. This far out these differences are
not that large and within the range of possibilities. Another
thing to keep an eye on are tides which start to increase
astronomically on Sunday and therefore some splashover is a
possibility during Sundays high tides.
Behind this low on Monday expect a cyclonic flow to once again
produce a few showers and cooler breezy conditions. High pressure
builds in on Tuesday and crests over the area on Wednesday
resulting in dry conditions and moderating temperatures.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Short Term...
Summary: Low pressure crosses the region tonight with rain and snow
ending late this evening before strong winds develop for
Thursday and Thursday night along with continuing mountain snow
showers.
Restrictions: VFR conditions with some embedded MVFR at the moment
in SHRA. This will continue through this evening before the cold
front pushes through the region. For HIE...this will transition
rain to snow with IFR conditions likely. For LEB-AUG-RKD MVFR
will dominate through the night with VFR and occasional MVFR to
the south. Outside of HIE...conditions should improve to VFR
for Thursday and continue VFR through Thursday night.
Improvement to VFR will come by late day Thursday at HIE and
remain generally VFR through Thursday night.
Winds: Southeasterly winds 5-10kts will shift westerly this evening
and increase to 10g16kts for the overnight before strengthening
further from the WNW during the day Thursday...reaching
20G30kts. Winds will diminish to 10g20kts Thursday night.
Lightning: There is a low chance of lightning for
CON/MHT/PSM/PWM through 00Z with gusty winds possible with any
thunderstorms that occur.
LLWS: No LLWS is expected through Thursday night.
Long Term...
Generally VFR to MVFR Friday and Saturday. Widespread IFR
with possible LIFR conditions Sunday as widespread rain develops.
MVFR south of the mountains on Monday.
&&
.MARINE...
Short Term...
Southerly winds gusting to near 30kts through this evening will
shift to the west northwest and strengthen overnight with gales
likely all waters through Thursday night.
Long Term...
SCA wind and waves Friday diminishing in the afternoon and
evening. Conditions below SCA levels Saturday into Sunday. Wind and
waves building to SCA levels later Sunday and lasting into Tuesday.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory until 2 PM EDT Thursday for MEZ007>009.
NH...Winter Weather Advisory until 2 PM EDT Thursday for NHZ001.
MARINE...Gale Warning from 4 AM Thursday to 11 AM EDT Friday for
ANZ150>154.
&&
$$
SYNOPSIS...
NEAR TERM...Arnott/Casey
SHORT TERM...Arnott
LONG TERM...Lulofs
AVIATION...
MARINE...
Area Forecast Discussion
National Weather Service North Platte NE
634 PM CDT Wed Apr 21 2021
.SHORT TERM...(This evening through Thursday night)
Issued at 354 PM CDT Wed Apr 21 2021
The main forecast challenge to round out the workweek deals with
another round of precipitation with unseasonably cool temperatures.
An upper low brushes the north while a surface low slides to the
south over the next 24 to 36 hours.
This evening and tonight... The cu field over north central Neb that
developed on the periphery of the Great Lakes trough will dissipate
this evening as mid/high level clouds overspread the southwest.
Cirrus blowoff from the Rockies is already evident with an upper low
entering the Great Basin and surface low tries to get organized over
the southeast Colorado plains. An inverted surface trough and mid-
level front lift north into the Sandhills tonight as indicated by
strengthening moisture advection and broad isentropic lift (notably
at 295-300K). Slowly spread PoP northeast after 06z, using a mix of
HREF and HRRR as guidance for coverage and timing. The cloud layer
stays around -10C overnight as surface temps dip into the mid/upper
20s. Used snow as the primary p-type for any showers that develop.
Expect any precip to be light as low level moisture is initially
limited. Forecast soundings suggest essentially a mixed layer
through 06z and slow saturation down from H7. Current (as of 20z)
dew point depressions around the area range from 20 to 30F. As the
night wears on, lift strengthens around H7, which could add somewhat
of a convective feature to the precip. Any snow that falls should
remain a skiff at most and mainly on elevated surfaces.
Thursday and Thursday night... Precipitation potential increases
across the Sandhills throughout the day as mid-level forcing/lift
and low level moisture advection continue to strengthen. Increase
PoP to chc after 12z across the north and eventually lkly by
afternoon. The surface inverted trough should be lined up across
western Neb by midday and H7 low over central SoDak. Greatest
potential for rain showers will generally be along the state line to
correspond with the best forcing. Will also need to monitor
development ahead of the surface boundary, so included schc PoP
farther south along the Hwy 83 corridor through early evening.
Thunder parameters are very weak with virtually no CAPE over the
forecast area. While the surface boundary nearly stalls, the upper
wave is rather progressive. Dry air fills in right behind the
shortwave and mid-level flow quickly switches to downglide, so cut
off PoP after 06z. Despite thick cloud cover over the region, nudged
max temps slightly warmer to account for modest WAA and breezy south
winds. Late day clearing is also possible in the panhandle/far
southwest, so pushed highs to almost 60F there. Farther north where
moisture chances exist basically all day, kept highs in the upper
40s to lower 50s. Clearing skies and waning surface winds should
allow temps to fall below seasonal norms again at night with lows in
the 20s west and lower 30s east.
.LONG TERM...(Friday through Wednesday)
Issued at 354 PM CDT Wed Apr 21 2021
Over the weekend, a broad upper ridge sets up over the southern
CONUS, leading to a warm and generally dry spell for Nebraska.
Guidance is trending warmer, and blended in some of the warmer
solutions to account for H85 temps pushing 20C under fair skies and
south/southwest low level flow. Forecast max temps now call for
widespread mid/upper 70s Sunday and lower/mid 80s Monday. This air
mass drives humidity values down to 20 percent and even under 15
percent far southwest. When combined with gusty southwest winds,
this will create elevated to near critical fire weather conditions.
A rather strong cold front is slated to cross the forecast area
Monday night into Tuesday, which presents the next chance of precip.
Thunder is also possible across the east Tuesday afternoon, but
severe threat appears low.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 631 PM CDT Wed Apr 21 2021
In the first 12 hours of the TAF period, VFR conditions are expected
with no VIS or CIG concerns. Clouds will build in overnight and
bring a band of light snow starting in southwest Nebraska and
heading northeastward. As the day progresses, expect a transition to
rain-snow mix, or even rain. Any snow accumulations should be under
an inch, but CIGs will lower in the morning and into the afternoon
creating MVFR conditions for northern Nebraska terminals.
Confidence remains low in lower cigs, as they may locally drop
into IFR conditions, but keep an eye on later forecasts for
updates as it nears. Additionally, as the precipitation heads in,
so does some stronger winds, up to about 20kts, and gusts of up to
30kts at the sfc. Winds will be generally from the south
southwest.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Snively
LONG TERM...Snively
AVIATION...Brown/Buttler/Sinclair
Area Forecast Discussion
National Weather Service Louisville KY
1002 PM EDT Wed Apr 21 2021
.Forecast Update...
Issued at 945 PM EDT Wed Apr 21 2021
Instability-driven showers that popped up this afternoon have
dissipated with the loss of heating, and temps are well on their way
down toward the freezing mark. Another subtle upper wave has
developed a batch high-based stratus over Illinois, and this feature
will make its way east across the Ohio Valley overnight. Even if it
does limit our cooling, there is still a decent window of
opportunity for temps to drop below freezing, so will not raise mins
or alter the Freeze/Frost headlines. Text products have been updated
to clean up early evening wording.
&&
.Short Term...(This evening through Thursday)
Issued at 253 PM EDT Wed Apr 21 2021
Upper low is now over the northern Great Lakes region while the
latest surface analysis places the cold front east and parallel to
the Appalachians with expansive high pressure building in across
most of the central CONUS. With the upper trough axis still upstream
and the 850mb thermal trough analyzed over central KY, expect to see
PoPs continue through this afternoon into early evening. RAP model
soundings show steep low level lapse rates with the upper portions
of the shallow moisture column well within the DGZ, so expect that a
mix of rain and snow is likely with any showers. As such, current
radar is showing scattered showers across the CWA with a few reports
so far of both rain and snow.
Clearing this evening will be be short lived as a pair of shortwave
perturbations swing around the parent low and result in increased
cloud cover overnight. But even with the increase cloud cover, CAA
should be strong enough to drop temperatures overnight to below
freezing with upper 20s and low 30s expected for most. Will allow
the Freeze Warning and Frost Advisory to continue unchanged, both
valid from midnight EDT / 11 PM CDT tonight to 10 AM EDT / 9 AM CDT
Thursday morning. The second shortwave could create enough lift to
generate a few isolated rain showers in the Bluegrass Thursday
afternoon. Thursday afternoon highs are expected to reach into the
low 50s across the Bluegrass and into the mid to upper 50s
elsewhere.
.Long Term...(Thursday night through Wednesday)
Issued at 245 PM EDT Wed Apr 21 2021
Cool conditions will continue into the first part of the long term.
High pressure will be off to our east by Thursday night, with light
southerly to easterly return flow expected across our region.
Temperatures Thursday night into Friday morning will be a bit
tricky, as skies will start off clear and winds will be light,
allowing temperatures to drop quickly... but then clouds increase
and perhaps even a few light sprinkles or showers develop by early
Friday morning ahead of a weak vort max. Models then prog the
temperatures to stabilize if not rise slightly going toward sunrise
Friday. There will likely be a window for freeze-like conditions
and/or frost to develop ahead of the clouds, mainly east of I-65,
with the highest chances toward the I-75 corridor. As a result,
after collaborating with surrounding offices, a freeze watch is in
effect for Harrison, Nicholas, Scott, Bourbon, Fayette, and Clark
counties (KY) Friday morning. Additional headlines expanding
westward (frost and/or freeze) can`t be ruled out in subsequent
updates if confidence increases in the potential.
An area of low pressure will eject into the southern Plains on
Friday and gradually work eastward toward our region. Most models
track the low just south of the KY border, keeping the warm sector
and any potential severe weather threat well off to our south. We
will, however, be in an area of enhanced upper level lift and
forcing, so we should see a modest amount (0.50-1.5") of rain
starting late Friday night and persist through all of Saturday.
We dry out Sunday as high pressure passes over the Great Lakes
region. The high gets settled over the Appalachians by early next
week and temperatures really ramp up in response to strong southerly
return flow and amplified upper level ridging over most of the
eastern half of the U.S. Looks like we should stay dry through at
least mid-week next week.
&&
.Aviation...(00Z TAF Issuance)
Issued at 705 PM EDT Wed Apr 21 2021
IMPACTS: VFR conditions through the valid TAF period. Earlier
rain/snow showers now mainly virga and will soon dissipate.
DISCUSSION: Weakening radar returns continue to show up, but based
on METARs and surrounding webcams, this activity is now mainly virga
and will continue to dissipate through sunset. Boundary-layer drying
has lifted the strato-cu to a mid-level ceiling, which will briefly
scatter out this evening.
Another wave currently near the Mississippi River is getting sheared
out, but will bring in another strato-cu deck overnight. Should
remain solidly VFR and no precip is expected. Winds should go
light/variable as sfc high pressure continues to build.
Another wave reinforcing the broad upper trof will drop SE into
eastern Kentucky Thu afternoon. We`ll see a high-based strato-cu
ceiling with this feature also. Not confident enough that precip
will extend far enough west to include it in LEX, but it bears
watching. Either way look for VFR cig/vis and WNW wind gusts just
shy of 20 kt.
CONFIDENCE: High on winds/ceiling. Moderate on afternoon precip
potential at LEX, high confidence in dry forecast elsewhere.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Freeze Warning until 10 AM EDT /9 AM CDT/ Thursday for
INZ076>079-083-084-089>092.
KY...Freeze Warning until 10 AM EDT /9 AM CDT/ Thursday for
KYZ023>025-027>043-045>049-053>057-062>067-073>078-081-082.
Freeze Watch from late Thursday night through Friday morning for
KYZ036-037-041>043-049.
Frost Advisory until 9 AM CDT Thursday for KYZ026-061-070>072.
&&
$$
Update...RAS
Short Term...CG
Long Term...DM
Aviation...RAS
Area Forecast Discussion
National Weather Service Tulsa OK
1014 PM CDT Wed Apr 21 2021
...UPDATE...
.DISCUSSION...
Only a few changes have been made to the previous forecast in this
update, namely to adjust for sky cover and temperature trends. Mid
cloud is increasing a little quicker than earlier forecast across
far southeast Oklahoma, with high cloud dominating farther north.
This should continue through the rest of the night. Have
maintained low POPs in far southeast Oklahoma given mid level
echoes showing up on the regional mosaic and consistent HRRR
output. Will also keep the Freeze Warning as is with temperature
trends showing a quick decrease at sites exhibiting a calm wind on
the last observations despite the high cloud cover. Updated
products already out.
&&
.TSA WATCHES/WARNINGS/ADVISORIES...
OK...Freeze Warning until 8 AM CDT Thursday for OKZ056>058-063-069.
AR...Freeze Warning until 8 AM CDT Thursday for ARZ001-002-010-011.
&&
$$
SHORT TERM...22