Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/22/20
Area Forecast Discussion
National Weather Service Caribou ME
1043 PM EDT Tue Apr 21 2020
Low pressure from the west track across the region overnight
into Wednesday. High pressure will build into the area Thursday.
A low from the Mid-Atlantic states will track well south of the
region on Friday followed by high pressure Saturday. Another low
from the mid Atlantic states will track south of the region on
.NEAR TERM /THROUGH WEDNESDAY/...
1025 PM Update...
Upgraded Piscataquis and Nrn Penobscot County into a Winter
Weather Advisory. Radar enhancement redeveloping in this region
and received a report of 4 inches in Wellington, SW Piscataquis
County. Nrn Penobscot County under and enhanced band of snowfall
and this band is pushing ne into Aroostook County. Increased
snowfall totals to 4-5 inches and this still could be a bit
underdone, given that there is some upslope enhancement. So far
across the northern areas, less snowfall amounts(around an
inch), but this expected to change overnight w/more snow on the
way. Sfc low lifting ne toward an area of pres falls as seen
on the latest satl imagery and sfc analysis. The latest HRRR and
RAP continue to match up well. A quick look at the latest HREF
guidance brings a batch of moderate to heavy snowfall across
Aroostook County overnight which will increase snowfall amounts.
Some areas in the County could see 4 inches by early morning.
This will need to be monitored.
Temps have settled down into the lower 30s across the n and
w while snow keeps going. Further s across central and Downeast,
temps in the mid to upper 30s w /rain-snow mix. Adjustments made
to match w/the latest conditions.
For Wednesday, sn shwrs will linger longest across the N and
Cntrl Mtns with unseasonably cold and windy conditions with
generally mostly cloudy to cloudy conditions. With highs only
around in the lower to mid 30 northwest to around 40 Downeast,
Wednesday will definitely have a more winter feel than spring.
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Cooler than average temperatures continue into the mid-term. A
few snow showers could persist Wednesday evening, mainly over
the north, as steep low level lapse rates persist in the cold
airmass. Think that snow showers should finally die off after
midnight with just enough subsidence with approaching high
pressure. Awfully cold Wednesday night with lows around 20 in
the north and mid to upper 20s Downeast, especially impressive
considering little decoupling is expected with enough of a
pressure gradient to keep west wind all night.
Still cooler than average for Thursday, but a bit warmer than
Wednesday as high pressure continues to build in. Still fairly
windy though. Looks dry.
Thursday night high pressure builds in. Surface high pressure is
more of a col rather than a well defined high. Could get rather
cold if places decouple, and it appears most places will
decouple thanks to mostly clear skies and diminishing winds.
Generally looking for 20s with some teens in colder northern
For Friday, low pressure passes by offshore from west to east.
Question is whether it`s close enough to bring precipitation to
Downeast. Majority of models keep precipitation just offshore,
but it`s close enough to warrant chance PoPs for coastal
Downeast. Could be cold enough for mixed precip or snow Downeast
if precipitation can make it that far north. Most likely
Northern Maine will remain north of even most of the clouds from
the passing system.
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Longwave trough remains in the Eastern US with cooler than
average temperatures persisting into early next week. May see a
quick shortwave ridge with quiet weather and slightly warmer
temperatures for Saturday. However, then general model consensus
is for unsettled late Sunday into Monday as an upper level low
approaches from the WSW and moves through the region. May see
modest Nor`easter development, though models not in good
agreement on the strength and timing of this. Regardless, late
Sunday to late Monday looks like a generally wet period. Should
be cool enough for mixed rain and snow inland, though not too
concerned about accumulating snow inland at this point unless
the Nor`easter gets stronger than currently expected. High
pressure may build in Tuesday, but the Eastern US should still
be under a longwave upper level trough so not much confidence in
any dry or warmer weather coming any time soon.
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
NEAR TERM: Tue Ngt...Conditions lowering to IFR by late eve
with rain/snow Downeast and mostly snow in Northern Maine with
conditions improving to MVFR Downeast in scattered rn/sn shwrs.
Breezy from the SE, shifting to the W late.
Wednesday...From KHUL north MVFR with sct sn shwrs. South of
KHUL, VFR with isold rn/sn shwrs. Windy from the W.
SHORT TERM: Wednesday Night and Thursday...Mainly VFR and windy
from the west.
Thursday Night...Diminishing winds and VFR.
Friday...Mainly VFR with N breeze. Can`t rule out MVFR along the
coast as a system passes offshore.
Friday Night to Midday Sunday...VFR with N/NW breeze.
Late Sunday...MVFR/IFR possible with the next weather system.
Update...Extended the Gale Warning for the outer zones til 4AM.
Winds have been delayed in kicking and have just started
upwards. Latest ob from 44027 showed gusts to 37 kt. 44034 was
nearing 35 kt gusts. It will be about a 4 to 6 hr period of gale
force winds and then winds will be dropping off by daybreak.
SCA stays for the intra-coastal zone.
SHORT TERM: Remaining windy out of the west over the waters
Wednesday night and Thursday high end small craft or possibly
low end gales. Improving below small craft winds/seas by late
Thursday night with high pressure. However, another system for
Friday passing offshore could bring conditions up close to small
craft again late Friday. Mainly below small craft Saturday to
midday Sunday. Small craft again possible late Sunday with
another low pressure system.
ME...Winter Weather Advisory until 4 AM EDT Wednesday for MEZ004-
MARINE...Small Craft Advisory until 6 AM EDT Thursday for ANZ052.
Gale Warning until 4 AM Wednesday for ANZ050-051.
Area Forecast Discussion
National Weather Service Fort Worth TX
717 PM CDT Tue Apr 21 2020
.SHORT TERM... /NEW/
A few showers/storms tried to develop this afternoon generally
north of the I-20 corridor, but the cap was a bit too strong. The
only exception was across the northeast zones where a few robust
updrafts were able to break through.
The isolated storms south of Abilene will likely dissipate in the
next couple of hours as they lose all surface heating and move
into more stable air. However, we will include some low PoPs in
the far western zones to account for this activity.
We also will keep an eye on the storms moving out of the
Panhandle, but these will likely stay to the north and west of
the CWA, at least through the night. It appears that the necessary
forcing for storms across the forecast area will not arrive until
The forecast with regards to Wednesday potential severe weather
event has not changed and the specifics are detailed in the
/Through Wednesday Night/
The main story over the next 36 hours will be the multiple rounds
of thunderstorms, some of which will likely be severe. The
greatest potential for severe weather will be on Wednesday
afternoon and evening, generally near and east of the I-35/35E
corridor. All modes of severe weather, including tornadoes, large
hail, and damaging winds will be possible. A few strong tornadoes
are not out of the question.
Morning surface analysis shows a broad area of low pressure over
the Permian Basin. A dryline extends from this surface low, out
across the Edwards Plateau. A warm front was analyzed across North
Texas, but this warm front has since lifted north of the Red
River. In the upper levels, a shortwave trough is moving through
the Great Basin and into the Four Corners region. Later this
afternoon, a few thunderstorms may develop east of the dryline.
While instability is quite strong owing to the mid to upper 60s
dewpoints in the warm sector, the cap is very strong. The strong
cap and lack of upper-level support will likely prevent convection
from developing. Will maintain low (less than 15 percent) PoPs
over areas west of U.S. Highway 281.
The next chance for thunderstorms will come late tonight. As the
upper-level trough moves through the Four Corners region and into
the Southern Rockies, thunderstorms will develop over western
Oklahoma. These storms will track east-southeast across the Sooner
State, and should stay north of the Red River. Some model guidance
brings them close to the river however, so will carry slight
chance (about 20 percent) PoPs overnight.
Wednesday is when things will get interesting. The upper-level
trough will continue its trek eastwards, bringing the surface low,
dryline, and cold front along with it. Widespread thunderstorms
will develop ahead of the dryline. Initial development will
likely occur west of the Dallas/Fort Worth Metropolitan Area
during the mid to late morning hours. This is probably one of the
bigger sources of uncertainty: the extent of morning convection.
The HRRR is the most aggressive model with this convection, with
the NAM being the most conservative. The HREF which takes into
account both of these (and others) seems to have the best picture
though. The HREF develops convection by late morning near or just
west of the Dallas/Fort Worth area, with increasing coverage
through the afternoon as the dryline continues east.
As thunderstorms continue eastward into the afternoon, they will
encounter and increasingly unstable air mass. The rapidly
deepening low tracking through the Red River Valley will draw
lower 70s dewpoints northward. Model guidance forecasts SBCAPE in
excess of 3,000 J/kg by late afternoon near and east of I-35/35E.
The 3 km NAM shows SBCAPE exceeding 4,000 J/kg in a narrow
corridor immediately ahead of the dryline. Meanwhile, as this low
deepens, a strengthening LLJ will lead to increasingly large and
curved hodographs. 0-1 km SRH will likely approach or exceed 200
m2/s2, especially east of I-35/35E and north of I-20. This is the
area where SPC has indicated not just an enhanced risk, but has
drawn in a 10% significant (EF2+) tornado area. The parameter
space and mesoscale setup certainly appears favorable for
tornadoes, with a few strong tornadoes possible. In addition to
the tornado threat, the forecast very large CAPE and mid-level
lapse rates exceeding 7 C/km will support very large hail. One
question however is whether storms will remain discrete. Deep-
layer shear vectors will be oriented orthogonally to the dryline,
which would favor discrete supercells given the large magnitude of
the shear. The issue however is that sometimes very dynamic, and
strongly-forced systems can often result in total cap erosion,
leading to widespread convection. Still, any thunderstorms that do
remain discrete will have the potential to become strong
supercells capable of all the hazards mentioned already.
Thunderstorms will end rapidly from west to east as the day
progresses, with storms ending over our CWA by midnight Thursday.
.LONG TERM... /Issued 334 PM CDT Tue Apr 21 2020/
/Late Week, This Weekend, and Early Next Week/
A late season cold front will be pushing off the Upper Texas Coast
by sunrise Thursday with little fanfare in regard to low level
cold advection. The western counties will see a brief and modest
push of drier air, as broad and diffuse surface high pressure
settles across the region. Another strong mid level shortwave will
arrive within northwest flow aloft and across the Southern Plains
Thursday night and Friday. With our surface ridge shifting east
of the area and rapid cyclogenesis to our northwest, breezy
southerly winds will return to the area Thursday night into early
Friday morning...before a dry cold front arrives during the day
Moisture will be fairly meager for this disturbance and its
associated ascent to work off of, but there may be a better plume
of mid level moisture for a slight chance of high- based &
elevated storms across our northeast counties Friday. Despite the
very low coverage of storms, mid level lapse rates will be very
steep, so could not rule out a strong storm or two north of I-30
and east of I-35E with smaller hail. Rainfall amounts are not
expected to be of any significance. Lows each day will start off
pleasantly cool in the 50s/60s, with highs between 75-85 degrees
each afternoon as the dry air warms readily where more abundant
sunshine exists across the West and Central Texas.
This weekend will be mostly dry with cool mornings and mild
afternoons in the 70s. A few locations will read in the lower 80s
in our western counties with better low level cold advection with
Friday`s cold front. A few shortwaves will transit the dry
northwest flow aloft particularly across our north and east parts
of our counties, but as of right now it appears the airmass
should be too dry in the lower levels for more than some virga or
sprinkles Saturday night into Sunday morning across the northeast
counties. Otherwise, the weekend should be fine for limited
outdoor activities as we see our longwave pattern flip flop from
the trough/split-flow regime in the Western CONUS/ridge in the Eastern
CONUS seen in recent weeks. This means we`ll likely see more of a
drier and warmer regime to end the month of April and likely
continue through the first week of May. Lows in the 50s Monday
morning will modify to the 60s next Tuesday/Wednesday, as highs
average 5-15 degrees above normal into the 80s and possibly a few
lower 90s reading across western Central Texas up through
Northwest Texas. I have some low rain/convective chances during
this time as our Eastern CONUS longwave trough amplifies in
response to a strong shortwave and upper jet energy diving
southeast across the Midwest into the Mississippi/Tennessee
No significant aviation weather concerns through the evening with
VFR conditions and a south to southeast wind.
A few showers/isolated storms will be possible through the
evening, generally north of the I-20 corridor, but a cap of warm
air aloft will limit development. Otherwise, scattered CU between
5000 and 6000 ft at the start of the TAF cycle will likely
dissipate after sunset.
A 30 knot low level jet will develop tonight, bringing a surge of
low level moisture northward. Stratus will develop over South
Texas and the Hill Country late this evening, spreading northward
overnight. MVFR ceilings will likely reach Waco between 09Z and
10Z and by 12Z across the Metroplex TAF sites. These ceilings
will remain in place until a dryline passes in the afternoon.
The primary aviation concern with this forecast will be
thunderstorms along and ahead of a lifting upper trough and
dryline. Storms will likely develop west of the TAF sites in the
pre-dawn hours Wednesday. These storms will become more organized
as they move east through the day. The best window of time for
storms will be between 15Z and 21Z, but it is unlikely that
storms will impact the TAF sites during that entire time frame.
After 21Z, the dryline should have move east of all terminals.
A south to southeast wind tonight/Wednesday morning will become
southwest by mid afternoon and west/northwest late
afternoon/evening. Wind speeds will range from 10 to 15 knots
until mid afternoon with speeds increasing between 15 and 20 knots
along with some gusts to 30 knots behind the dryline and cold
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 66 83 60 82 62 / 10 70 5 0 0
Waco 67 81 59 83 61 / 5 80 5 0 0
Paris 62 72 58 77 58 / 20 90 50 0 5
Denton 64 83 57 81 61 / 20 70 5 0 5
McKinney 64 79 57 80 60 / 20 80 10 0 5
Dallas 66 82 60 83 63 / 10 80 5 0 0
Terrell 63 77 58 80 59 / 10 80 30 0 0
Corsicana 65 77 60 80 61 / 5 80 30 0 0
Temple 67 80 59 83 61 / 5 80 0 0 0
Mineral Wells 64 85 55 82 62 / 20 50 0 0 0
Area Forecast Discussion
National Weather Service Lubbock TX
813 PM CDT Tue Apr 21 2020
With thunderstorm activity remaining well north and east of the
CWFA, have pulled mention of storms through midnight. The RAP is
about the only guidance suggesting some storms could fire across
the Rolling Plains. Surface flow out that way remains divergent.
However, as the upper level lift associated with the trough across
AZ, we could see enough dynamical cooling aloft to erode the cap
.PREV DISCUSSION... /issued 629 PM CDT Tue Apr 21 2020/
Thunderstorm activity has remained well north of our TAF sites
this evening and the latest data suggest this will likely remain
the case...at least through most of the evening. There is some
risk that some storms could fire INVOF KCDS later this evening
though confidence in this scenario remains too low to explicitly
mention in the TAF ATTM.
The other concern will be the risk of low clouds. KPVW/KCDS look
to have the best chance though probabilities are still largely
running under 50% at both sites. Will continue to monitor trends
to our north to see if a surge of moisture laden air can work its
way into the area.
PREV DISCUSSION... /issued 238 PM CDT Tue Apr 21 2020/
A closed low was currently slowly moving east roughly along the
36th parallel. Stronger upper level jet winds will move overhead
today but especially later tonight into early Wednesday morning. The
bulk of the large scale lift will be associated with this bigger
push of stronger upper level winds.
The largest concern today is the strength of the capping that is in
place. A good surge of low level theta-e air was ongoing across the
Rolling Plains into the central Texas Panhandle extending up into
far southeastern Colorado. This has resulted in a very unstable axis
of air. Mixed layer CAPEs will max out at around 1500-2000 J/kg this
afternoon which will be coupled with extremely high shear and
helicity. The one but important issue is the cap which looks to hold
convection down for this afternoon. Almost all CAMs have a dearth of
convection in the southern Texas Panhandle but develop convection
across the northern Texas Panhandle where no capping is in place.
Instability will increase during the evening and overnight hours
with cooler temperatures at mid levels moving overhead from the
passing closed low. This time frame may be our best shot at seeing
any convection with elevated storms being able to take advantage of
the ample instability and shear.
Fog may be possible again tonight but is much more uncertain given
the expected rapidly changing conditions early Wednesday morning.
Although winds will most likely start out southeasterly this evening
a quick change will come as a strengthening surface cyclone moves
from the Texas Panhandle into Oklahoma on Wednesday. This will swing
winds around to the west/northwest early Wednesday morning possibly
allowing for a brief period of fog before the strong winds develop.
Surface winds will further increase through the morning into mid
afternoon. At the moment, guidance shows wind speeds just below
advisory criteria with the highest speeds across the extreme
southeastern Texas Panhandle.
Wind speeds will decrease slowly through the day and from west to
east fairly rapidly close to sunset as the storm system continues
to move off to the east. Thursday will see a west wind redevelop
and dry air spread across the Caprock. Combination of highs in the
low to mid 80s and a breezy west wind 15 to 25 mph will result in
an elevated fire danger for much of the afternoon across the South
Plains. A weak cold front arrives early Friday morning dropping
high temperatures about 10 degrees, then even more so on Saturday
when highs will be in the low 70s mainly due to increased cloud
cover. The ECMWF is now totally dry for the weekend while the GFS
continues to try and bring some precipitation into the northern
South Plains late Saturday afternoon. Will keep the forecast dry
as the post front airmass looks to be dry and any moisture will
have to arrive from aloft and northwesterly flow usually doesn`t
favor much in the way of precipitation.
Temperatures will start to warm Sunday into the first part of next
week possibly getting back into the upper 80s to lower 90s in some
spots. Models remain variable at the end of the forecast but low-
level moisture may try to return to the region and a series of
weak shortwaves in northwesterly flow may help provide us an
outside shot at some storms but will keep forecast dry for now.
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1056 PM CDT Tue Apr 21 2020
.UPDATE...For 06Z Aviation discussion below
.SHORT TERM...(This evening through Wednesday night)
Issued at 230 PM CDT Tue Apr 21 2020
Visible satellite imagery shows a northwest-southeast oriented
band of mostly mid clouds across the western portion of the area
in association with the leading edge of warm advection and some
upper divergence. This has produced a few sprinkles/flurries, but
most of the returns have remained aloft. This should shift
eastward this afternoon and evening, with a second impulse
dropping southeast along the baroclinic zone tonight. Main focus
for any shower activity tonight looks to be near and east of I-94
given the large scale conditions and output from the HRRR, HopWRF,
and other CAMs. No significant precipitation is expected.
Wednesday still looks tricky in terms of temperature (and cloud
cover), with the frontal boundary lingering over the area. Looks
like the gradient in temperatures will make it a bit northeast of
the Twin Cities metro, so we should see readings get up to around
70 in the metro area. Southwest toward Mankato and points west of
there an 80 degree reading can`t be ruled out, while northeast
toward Ladysmith temperatures will only get into the lower 50s if
the boundary winds up where expected per the RAP extension and CAM
.LONG TERM...(Thursday through Tuesday)
Issued at 230 PM CDT Tue Apr 21 2020
The main concern in the extended period remains a couple of
better chances for rain mainly in the Thursday night/Friday and
Monday/Tuesday time frames.
Models continue to move short wave trough through the upper
midwest region Thursday and Friday. Appears better forcing remains
across the southern CWA during the period. Will still hold onto
blended guidance PoPs for this period. May see a small thunder
chance move across the southwest CWA as well. The next wave rides
the fast westerly flow across the region and moves a cold front
through Monday/Tuesday period. Southerly flow is expected to
increase ahead of the front, especially on Monday. Showers and
perhaps a chance of thunder will accompany this front.
Temperatures should trend warmer, especially into early next week
ahead of the Monday front. Looking for highs to range slightly
above normal into next weekend.
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1056 PM CDT Tue Apr 21 2020
Light radar returns have merely generated virga/sprinkles this
evening thus far, given the dry air in place at the surface (with
dewpoints in the teens to lower 20s). So while we could see
continued sprinkles overnight, don`t envision an impact at sites.
Have included a VCSH mention at KRNH and KEAU with no
restrictions. The next concern shifts to ceilings on Wednesday
with a front stalled across the area. Northern/eastern sites still
look to be on the fringes of the MVFR deck, but at this point
still think a scattered mention is the most appropriate. Winds
will be a bit variable with front stretched across the area, but
in general an east/southeast directional component will prevail
through Wednesday morning.
KMSP...Virga/sprinkles remain possible overnight, but expect
conditions to remain VFR.
/OUTLOOK FOR KMSP/
Thu...MVFR possible. Wind ENE 5-10kts.
Fri...VFR. Wind ENE 5-10kts.
Sat...VFR. Wind NE 5-10kts.