Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/16/21
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
626 PM CDT Thu Apr 15 2021
.UPDATE...
Issued at 624 PM CDT Thu Apr 15 2021
Made some adjustments to sky cover this evening given the latest
satellite trends. Leaned toward HRRR which has a decent
representation of the break in the clouds over the James Valley.
&&
.SHORT TERM...(This Evening through Friday Night)
Issued at 308 PM CDT Thu Apr 15 2021
The challenge for the short term remains the precipitation chances
this afternoon through the day Friday. Presently twin upper level
lows remain in place over the east central Rockies and eastern Great
Lakes area. The western low continues to gradually churn its way
east southeastward. The low holds together a little better and
brings precipitation further north and east than previous guidance
suggested. Most Hi-Res models and blends bring light rain and
snow as far east as the James River Valley. That said, most
measurable precipitation is still expected to remain west of the
James River Valley and should be limited to a few hundredths at
most for most locations. The main exception is the far
southwestern forecast area where a tenth of an inch of liquid
equivalent is possible. In addition, any snow accumulations should
be limited to a tenth or two at most, with the exception again
being the far southwestern forecast area where a half inch or so
could fall.
Lows tonight and Friday night will be in the upper 20s to low 30s,
which is pretty close to average if not slightly below average for
this time of the year. With cloudy skies and light precipitation,
Friday highs will be limited to the mid to upper 40s, which is
about 10 degrees below average, across the board.
.LONG TERM...(Saturday through Thursday)
Issued at 308 PM CDT Thu Apr 15 2021
Compared to 24 hours ago, the main take away is there is better
model agreement (and less ensemble spread) on strong cold fropa
timing on Sunday. Models have begun to show a similar solution of
cold fropa timing across the cwa during the afternoon through
evening hours on Sunday. So, for the time being, a warmer
temperature forecast for Sunday persists. Dry weather conditions
book-end the post cold fropa precipitation chances showing up Sunday
night into early Monday morning, while the CWA remains under some
form of northwest flow throughout the period. There will likely be
some pretty strong forcing/lift associated with this cold fropa,
making this Sunday night/early Monday timeframe the most likely
period in the forecast for somewhat-widespread light measurable
precipitation. It does still look as though a warming trend Saturday
into Sunday will be replaced by some strong low level CAA and strong
northerly winds Sunday night into Monday. The cold air likely sticks
around Tuesday before the next warming trend would commence
Wednesday into Thursday. Depending on the amount of sunshine that
can be had Monday and Tuesday, the environment may support a handful
of steep low level lapse rate "instability" showers by afternoon.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 624 PM CDT Thu Apr 15 2021
Terminals KABR,KATY,KPIR,KMBG
The mix of VFR/MVFR cigs will fall to MVFR/IFR overnight. There
will likely be some scattered breaks in the clouds again on
Friday.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...Wise
SHORT TERM...Telken
LONG TERM...Dorn
AVIATION...Wise
Area Forecast Discussion
National Weather Service La Crosse WI
619 PM CDT Thu Apr 15 2021
.SHORT TERM...(This evening through Friday)
Issued at 226 PM CDT Thu Apr 15 2021
Upper low continues to push east, now passing through lower Ontario,
with plenty of residual cloud cover on the back side back over our
area. Lingering morning sprinkles/drizzle have diminished as the low
pulls east, so we`re looking at a period of quiet weather as weak
surface ridging continues to nudge in for tonight into Friday. Lows
overnight will be tricky, as there`s not good model agreement on
when clouds begin to break up. On the more pessimistic side of
things, the RAP would suggest clouds linger right on into Friday
morning, though other high resolution guidance would already have
clouds breaking up later this afternoon. Clouds upstream in northern
Wisconsin show some holes developing this early afternoon, so have
trended toward scattering out this evening once daytime heating is
lost, with clouds lingering longest in the west. This results in
lows in the lower 30s in much of central and north-central Wisconsin
under the most clearing, and middle 30s elsewhere.
A shortwave will begin to push across the central Plains Friday
afternoon, but thus far it`s looking like the precipitation should
stay to our south during the day Friday. As our chilly air aloft
continues to moderate and some sunshine returns, highs Friday will
climb back into the 50s.
.LONG TERM...(Friday night through Thursday)
Issued at 226 PM CDT Thu Apr 15 2021
For the weekend, a series of shortwave troughs will move southeast
of the area. Other than some clouds, we will see no impacts from
these systems. Both high and low temperatures will be seasonable.
From Sunday night into Monday, a northern stream shortwave trough
will move through the region. This system will bring widespread,
light rain to the area late Sunday night and Monday. Most of the
EPS has rainfall amounts ranging from a trace to a couple tenths
of an inch.
In the wake of the front on Monday night, much colder air will
move into the region. 925 mb temperatures will cool into the -2
to -5C range. These cool temperatures will linger into Tuesday and
possibly Wednesday. With the warmer temperatures earlier in the
month still influencing the model bias corrected grids, the NBM
continues to run too warm. As a result, went with the NBM 25th
percentile.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 619 PM CDT Thu Apr 15 2021
Stubborn stratocumulus over the area this evening. Looking for MVFR
bases to continue at KRST, eventually lifting into VFR by 15z
Friday. Cloud bases at KLSE are expected to remain VFR, eventually
scattering out later tonight (after 05z). Otherwise, plan on
northwest-north/northwest winds through the period generally less
than 10kt.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Lee
LONG TERM...Boyne
AVIATION...DAS
Area Forecast Discussion
National Weather Service Boston/Norton MA
949 PM EDT Thu Apr 15 2021
.SYNOPSIS...
Widespread rain, heavy at times, is expected tonight into
Friday with rain changing to accumulating snow in the Berkshires
and Worcester Hills. A period of wet snow is also possible in
some of the lower elevations of interior southern New
England. Precipitation winds down late on Friday into early
Saturday. Unsettled but generally dry conditions continue later
Saturday night through Monday, with daytime cloudiness and
possible light showers. Any showers that do develop should prove
spotty and not a washout. Turning mild and dry for Tuesday
before a cold front brings our next chance for more widespread
rain around Wednesday.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
945 PM Update...
Highlights
* Significant elevational snow expected in the Berkshires and
northern Worcester Hills
* Some of the lower elevations may see a slushy accumulation.
Quite a challenging forecast revolving around the threat for
heavy wet snow with the focus for that at elevations above 800
feet. Extremely dynamical intensifying closed mid level low will
be tracking across southern New England overnight into Friday.
This is a classic recipe for a late season snow event. However,
this remains a very difficult forecast because a small
adjustment in precipitation intensity, the location of the
dryslot, and thermal profiles will make a big difference between
a slushy accumulation and very impactful heavy wet snow.
We are already getting reports of rain changing to snow in
northern Worcester county at elevations above 1000 feet. Given
the dynamic nature of the storm and the guidance showing an
impressive CCB into Friday, opted to upgrade northern Worcester
County to a Winter Storm Warning for 4 to 8 inches of snow.
Those higher amounts most likely at elevations near or above
1000 feet. The threat for some power outages is also a concern
given this will be a classic 32-33 wet snow. Also, we do think 2
to 5 inches of snow may also occur in the high terrain in the
northeast Hills of CT.
As for the lower elevations, precipitation may mix with or flip
to snow for a time when intensity is maxed out very late tonight
and into Friday. However, boundary layer may make it tough for
more than a coating to inch or so of slush. So in a nutshell, we
think the heavy wet snow concerns are for the high terrain
where some power outages will also be a concern.
Previous Discussion...
Deep cutoff low over the eastern Great Lakes/Mid Atlantic lifts
into southern New England late tonight. A mid level low will
develop along the south coast late tonight. A secondary surface
low will develop in response to the strong height falls south of
southern New England and lift toward Cape Cod and the Islands.
Not too much of a change in the forecast since the mid shift
update. Expecting strong lift and dynamical cooling per the
latest RAP/NAM/HREF and HRRR guidance. The dynamical cooling
will result in rain transitioning over to snow this evening
across the Berkshires and northern Worcester Hills. There will
be some of an upslope component with 925 hPa winds showing some
strong convergence across the higher terrain especially after
06Z tonight. Expecting 925 hPa temperatures to drop below 0
degrees Celsius, so am confident in ptype changing over to snow
or a rain/snow mix across much of the interior. NAM/GFS do show
decent saturation and lift within the dendritic growth zone for
a period late tonight. Only potential concern is if drier mid
level air can punch in, but think it is more likely after
daybreak.
Given the strong deep lift associated with the system have
blended the 75th percentile of QPF and WPC. This gives QPF
amounts of 0.75 to 1.25 inches overnight. The heavy wet snow
across the eastern slopes of the Berkshires is still anticipated
and have only nudged up amounts a bit based on a slightly longer
period where the DGZ and omega matches up per the 12Z NAM/GFS
guidance. Where the Winter Storm Warning is in effect have
totals of 5-8 inches with localized amounts greater than 10
inches. Where the Advisories are in effect have 2-5 inches of
snowfall with greater than 6 inches possible above 1000 feet in
the northern Worcester Hills. Since it is so localized in
nature opted to go with an Advisory versus a Winter Storm
Warning. Still a tricky forecast given the temperature ranges
are in the 31-34 degrees. Cannot rule out some snow flakes
mixing in across other areas of the CT River Valley, southern central
MA and northern RI, but shouldn`t amount to much if anything
given the marginal temps and warm ground.
Other thing that we will need to keep a close eye on is any
frontogenetical banding that sets up. Majority of guidance does
show some sort of banding between 1000-850 hPa, but the
positioning does vary depending on the model of choice. Will be
something that the mid shift will need to keep an eye on and
potentially refine the forecast some more. Heavy wet snow
expected with SLR between 7-9:1 across the higher elevations
and 4-6:1 or lower in the lower elevations.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
* Snow persists across the higher terrain, but may be tough to
accumulate especially later in the day as temperatures climb
into the mid to upper 30s.
* Rain continues elsewhere, but precipitation intensity will
wind down as the dry slot punches in.
Closed mid level low moves across southern New England on
Friday. The surface low will be situated near or over Cape
Cod/Islands.
Precipitation intensity winding down as the day progresses as
the strong 925 hPa convergence shifts northward. In addition, am
expecting the dry slot to punch in from SE MA into eastern MA
and potentially the interior. Have tried to reflect this with
precip chances and QPF values, but may need to be adjusted in
future updates. Precipitation amounts of roughly 0.25 to 0.75
inches are anticipated. This brings the storm totals to 1 to 2.25
inches with the highest amounts across the eastern slopes of the
Berkshires.
Given the strong easterly flow expected did lean toward the
NAM/NAMNest guidance for high temperatures. The result is
readings in the mid to upper 30s across the higher terrain and
low to mid 40s elsewhere. If the dry slot clears things out a
bit quicker than currently anticipated, may need to increase
temperatures across SE MA further.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Highlights...
* Rain with higher elevation snow gradually decreasing in coverage
Fri nite into Sat. Below-avg highs with near-avg lows.
* Generally dry Sat nite into Mon, though unsettled with diurnal
clouds and spotty light showers. Not a washout in any area.
* Warming back into the 60s to near 70 on Tues before a cold front
brings our next rain chances into Wed.
Details:
Friday Night into Saturday:
Periods of lower-elevation rain and higher elevation interior wet
snow should continue early on Friday night. The nearly vertically
stacked cyclone creeps away from southeast MA to a position near or
just east of Cape Cod into 12z Sat. Moisture depth looks shallow in
general with the dry slot overhead, which could make precip more of
a drizzle at times. The bulk of accumulating snow across the terrain
should have passed by Friday night. Winds will also flip to
north/northwest as the low pulls slowly away, which will spread
cooler air eastward. Still, considerable amount of cloud cover will
keep temperatures from falling very far, with lows in the mid 30s to
near 40, mildest across Cape Cod and coolest in the terrain.
Low begins to shift further east through Sat, with PoP being focused
more across eastern MA and into RI as mainly a cold plain rain.
Still only looking at highs in the mid to upper 40s for most, except
low 50s with enough breaks in the clouds across the CT Valley.
Saturday Night Through Monday:
Though weak high pressure returns, it remains a generally unsettled
period on the whole as cyclonic flow and related cool thermal
profiles aloft are maintained. This should support more diurnally
driven cloudiness during the daytime, perhaps enough to generate a
few instability showers at times but not a washout by any stretch.
Less cloudiness anticipated at night as the boundary layer
stabilizes. Really isn`t much in the way of upper-level support for
appreciable precip so not expecting a washout in any one area.
Modest warm thermal advection occurs each day which should bring
slowly warming highs each day. Lows Sat nite into the mid to upper
30s and into the upper 30s to lower-mid 40s Sunday night. Highs in
the 50s (upper 50s CT Valley) for Sunday, and mid 50s to mid 60s on
Monday.
Monday Night into Tuesday Night:
In this period, we shake free of cooler cyclonic flow aloft with a
transition towards anticyclonic flow/500-mb height rises into
Tuesday.
High pressure parked to our south will afford a milder southwest sfc
flow. Expect plenty of sun and dry weather, with warming 925-850 mb
temps. The 12z ECMWF brings 925 mb temps around +9 to +12C and about
4-6C at 850 mb. Should see highs reach well into the 60s for most
except 50s across Cape Cod, with a few lower-70s within conceivable
reach across the CT Valley as well. Will see dewpoints start to rise
as well so we may have to keep an eye for return of overnight fog
near the South Coast. Otherwise, mostly clear in the interior. Lows
in the mid/upper 40s.
Wednesday into Wednesday Night:
Increasing height falls aloft as a deep longwave trough approaches
the Great Lakes into interior New England through Wed nite. It will
also sweep across a surface cold front bringing with it a period of
showers. The exact timing isn`t clear this far out in time and
moisture and stability parameters don`t indicate significant rains
with this frontal passage, but it does offer the next chance for
more widespread precip.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels.
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High confidence in trends, moderate in timing.
Starting out MVFR to VFR across southern New England. Will see
conditions deteriorate to IFR and localized LIFR with
widespread rain. Rain will transition to wet snow across the
Berkshires and Worcester Hills. Some of the lower elevations may
transition over to a mix of snow and rain at times as heavier
precip moves through. E to NE winds from the Worcester Hills
eastward and N winds in western areas. Gusts of 15 to 30 kts
with the highest speeds along the immediate eastern coastline.
Friday...Moderate Confidence.
IFR to LIFR conditions slowly improve to IFR and borderline MVFR
late in the day. NE to N winds at 10-20 kts across much of
southern New England. The only exception along the South Coast,
Cape Cod and the Islands where winds shift to the W/SW with the
low pressure center overhead in the afternoon. Gusts of 25 to 30
kts. May have a brief period Friday morning where gusts along
the east coast get to 35-40 kts, but will be most likely for the
Outer Cape.
Friday night...Moderate confidence.
Precipitation gradually winding down low pressure lifts
offshore. Will see IFR and borderline MVFR condition with snow
still possible across the higher terrain. NW/N winds of 5-15
kts and 15-25 kts. Eastern coastal areas could see some
localized gusts of 30-35 kts especially after 06Z.
KBOS TAF...Moderate Confidence in TAF.
KBDL TAF...Moderate Confidence in TAF.
Outlook /Friday Night through Tuesday/...
Saturday: Mainly VFR, with local IFR possible. Windy with local
gusts up to 30 kt.
Saturday Night: Mainly VFR, with local MVFR possible. Breezy.
Sunday: Mainly VFR, with local MVFR possible. Slight chance
SHRA.
Sunday Night: VFR.
Monday: VFR. Chance SHRA.
Monday Night: VFR.
Tuesday: VFR. Breezy.
&&
.MARINE...
Today through Friday...High Confidence.
No major changes to the previous forecast. Slow moving
intensifying low will result in strong SCA to Gale force E to NE
winds. Seas building 9-13 feet across our eastern open waters.
Outlook /Friday Night through Tuesday/...
Friday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 13 ft. Chance of rain.
Saturday: Moderate risk for Small Craft Advisory winds with
areas of gusts up to 30 kt. Rough seas up to 10 ft. Slight
chance of rain showers.
Saturday Night: Winds less than 25 kt. Local rough seas.
Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Sunday Night through Tuesday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Winter Storm Warning until 8 PM EDT Friday for MAZ002-004-008-
026.
Winter Weather Advisory until 8 PM EDT Friday for MAZ003-009-
010.
RI...None.
MARINE...Gale Warning from 5 AM to 2 PM EDT Friday for ANZ231-232-250-
251-254-255.
Small Craft Advisory until 8 PM EDT Friday for ANZ233>235-237-
256.
Small Craft Advisory from 5 AM to 8 PM EDT Friday for ANZ230-
236.
&&
$$
SYNOPSIS...BL/Loconto
NEAR TERM...Frank/BL
SHORT TERM...BL
LONG TERM...Loconto
AVIATION...BL
MARINE...Loconto
Area Forecast Discussion
National Weather Service State College PA
1129 PM EDT Thu Apr 15 2021
.SYNOPSIS...
Low pressure near Lake Ontario this evening, will drift southeast
slowly and cross PA through Friday. Colder air will sweep across
the region and result in temperatures below normal for the next
few days.
Snow showers will fall across the higher terrain of the north
and west into Friday and a light accumulation of an inch or so
is expected across the ridgetops by Friday morning. Rain
showers will mix with wet snow at times at lower elevations.
Temperatures will gradually rebound to normal by Monday.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Had some snow showers just west of the office earlier this
evening. Made a few changes to the grids this evening.
Still seeing visibilities just below 2 miles at times in some
of the heavier snow showers just to the west of State College.
Earlier discussion below.
At 19Z, a moderately strong, albeit dry sfc cold front (here in
PA) was pushing east of the Lower Susquehanna Valley.
925 mb RAP temps around 8C (and sfc temps around 60F) across
the Lower Susquehanna Valley drop to around +2C over the Western
Mountains where temps have held pretty steady all day - in the
35-40F range.
Deepening cold air pushing into the Western Mtns attm will
support an increasing trend in showers of rain, gradually mixing
with and changing to mainly snow showers tonight at elevations
AOA 1800 FT MSL.
Painted in a light accum of snow on the ridgetops of Central,
Northern and Western PA late tonight and early Friday, with
perhaps an inch or two falling at elevation AOA 2500 MSL over
the Ski Country of the Laurel Highlands where the best well-
aligned, deep layer WNW fetch of Great Lake moisture,
orographic lift, and a deep well-mixed layer will be located.
SE of a KAOO to KIPT line and in the wake of the dry slot and
weak LLVL ridging, sct-bkn dual layer of strato/altocu clouds
will be found overnight with just some sprinkles or isolated
light rain showers.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Expect Friday to feature some showers, given a rather deep
low just off the coast.
Earlier discussion below.
Any snow showers remaining during the mid morning will likely
change over to rain showers across the mtns by late morning as
the Wet Bulb zero C level rises back over 1 kft AGL and precip
rates in the showers lighten as a result of the subsidence
inversion quickly dropping below 5 kft agl.
Perhaps the biggest ticket item for Friday will be peak wind
gusts in the 30-35 mph range across mainly the SW half of the
CWA where the strongest downsloping and deep-layer subsidence
will occur beneath the thermally direct. left entrance region of
a 100 KT jet over WVA and VA.
Max temps Friday will likely run about 7-8F below normal in most
places and if we get more numerous rain/wet snow showers than
expected into the afternoon hours across the NW Mtns and Laurel
Highlands, they could run a little more than 10F below normal
there.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
The outlook for the weekend and into next week is for more
typical April weather, with chances for precipitation every
couple of days and a mixed bag of clouds and sunshine. A deep
low pressure system, which is expected to bring several inches
of snow to higher elevations in the northwest on tonight into
Friday, will continue to move east off of the Atlantic coast
this weekend. In its wake, we`ll be in a persistent northwest
flow pattern, characterized by upslope rain/snow showers and
general cloudiness. Temperatures will gradually warm up each day
through the weekend, though highs will remain below average
ranging from the upper 40s to low 50s in the north and upper 50s
to low 60s in the southeast.
By early next week, we shed the effects of the retreating
trough, but a shortwave may generate a few scattered showers
Monday. Then, we finally get a glimpse of "mild" conditions and
even some sunshine by Monday evening, with temperatures
approaching the 70 degree mark in the Lower Susquehanna Valley
by Tuesday afternoon. The sunshine Monday afternoon and warmest
temperatures of the week on Tuesday will combine for the two
best days of at least the next 7.
Increasing clouds Tuesday night will precede another good
chance of rain, and perhaps some snow on Wednesday. Details are
still unclear, but QPF amounts should remain low enough to
minimize much in the way of accumulation. Then, below- average
temperatures return for Thursday as a deep upper trough digs
back into the northeast. Model guidance is still a bit variable
in how deep the trough will be, and thus how cold temperatures
will get. We`ll be keeping a close eye on the low temperatures
for Thursday morning, which appears to be the best chance for
near or sub- freezing temperatures across the Commonwealth.
Peeking into the future, the ECENS brings a return of mild,
above average temperatures into next weekend, while the GEFS
keeps the less-enjoyable weather pattern around for awhile.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Noticeably cooler air continues to spill into Pennsylvania in
the wake of today`s cold front. Winds have turned to come out of
the northwest with scattered rain and snow showers drifting from
the northwest mountains into the central part of the state.
IFR conditions will continue at BFD and JST overnight as
upslope NW flow continues across the Alleghenies of Northern and
Western PA. Farther southeast, MVFR is expected at UNV and AOO,
mainly with passing showers. The latest guidance indicates IPT
may have a several hour period of snow showers Friday morning,
with persistent IFR conditions. By Friday afternoon, expect
little improvement in the NW airfields and a deterioration to MVFR
cigs areawide as a weak trough moves through the Commonwealth.
Outlook...
Fri night...Reduced cigs/vis in NW mountains.
Sat...Improving to VFR areawide.
Sun and Mon...Low cigs possible in scattered showers, mainly
over the northern and western mtns of PA. Central ridge and
valley airfields should only dip to MVFR.
Tues...Reductions across the northern tier in rain showers late
in the day.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Lambert/Dangelo/Martin
NEAR TERM...Lambert/Dangelo/Martin
SHORT TERM...Lambert/Dangelo/Martin
LONG TERM...Banghoff
AVIATION...Banghoff
Area Forecast Discussion
National Weather Service Cheyenne WY
547 PM MDT Thu Apr 15 2021
.SHORT TERM...(This evening through Friday Night)
Issued at 225 PM MDT Thu Apr 15 2021
The main concern with this portion of the forecast is the timing
of the changeover to snow and snowfall amounts.
Latest water vapor loop was showing our dry slot finally starting
to fill in! This is in response to strong diffluence aloft and
isentropic lift between 290-300k. Another trigger mechanism is mid
level cold pocket of air across central Wyoming near 700mb. This
cold pocket will continue to slide southeast tonight, but the
models are showing some 700mb frontogenesis developing along and
southeast of the North Platte River Valley in the southern
Nebraska panhandle. Latest radar loop was also showing some bands
of snowfall moving northeast out of northern Colorado. These bands
will continue to lift northeast during the remainder of the
afternoon and this evening. The latest HRRR is very progressive
with these bands and moves the heaviest bands out of the southern
Nebraska panhandle by midnight. In the midst of the heavy snow
bands, we may end up with snowfall rates close to 1 inch an hour.
After these heavy snowbands move out of the area, we will be left
with more wrap around precip from the upper low. However, the
snowfall rates will begin to taper off by the morning commute.
Meanwhile, another shortwave will dive south from the Black Hills
and bring another round of snow showers to the region on Friday.
The greatest impacts will take place across the Nebraska panhandle
once again, but snow amounts will be 1 to 2 inches at best. The
snowfall should begin to taper off on Friday night especially at
the end of the diurnal heating cycle.
.LONG TERM...(Friday night through Thursday)
Issued at 225 PM MDT Thu Apr 15 2021
General cool and unsettled pattern expected to persist throughout
the week, with the GFS and ECMWF still showing a series of
disturbances digging south across the CWA. The positive tilted trough
axis centered just over central Wyoming begins shifting towards the
southeast just out of our region with a ridge slowly pushing in
behind it. This will bring some cooler temperatures into the region,
with highs for Saturday in the mid to high 30s and ending the long
stretch of precipitation experienced over the last few day. Even
under the influence of an upper level ridge, temperatures do not
recover very quickly, but showing a bit more seasonable totals for
the northern Nebraska Panhandle, and slightly lower in the remainder
of the CWA.
Heading into the week ahead, snow showers are possible just about
every other day under this pattern. Monday looks to bring the next
good potential for precipitation into the region as a strong cold
front digs southwards into Wyoming. Nighttime lows associated with
this system bring us back into the low 20s. There should be a slight
break in the weather Tuesday through Wednesday, before moisture
returns to the region again on Thursday ahead of a upper level
trough moving east.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 544 PM MDT Thu Apr 15 2021
IFR to LIFR conditions for most area terminals with snowfall
expected to continue through the night into Friday morning. Heavy
snow bands just south of the CO border will continue to move
northeastward this evening. KSNY and KBFF could see heavy snowfall
with these bands and significant reductions to visibility below
1SM if not down to 1/4SM. Current radar shows heavier snow bands
moving just east of KCYS which could keep visibility from dropping
below 1SM, however IFR to LIFR conditions are expected to
continue. Snow has mostly ended out west near KRWL, but a few
passing showers could briefly reduce visibility through 06z. Snow
will continue into Friday morning across the NE Panhandle before
beginning to lighten up from north to south. Some sites may begin
to lift to MVFR conditions near the end of the forecast period as
the snowfall tapers off and this system pulls off to the
southeast.
&&
.FIRE WEATHER...
Issued at 225 PM MDT Thu Apr 15 2021
Critical fire weather conditions are not anticipated during the
next couple of days due to plenty of snow cover, colder
temperatures and higher relative humidity.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Warning until 6 PM MDT Friday for WYZ106>108-114-
116>119.
Winter Weather Advisory until 6 AM MDT Friday for WYZ104-105-109-
112-113-115.
Winter Weather Advisory until 6 PM MDT Friday for WYZ101>103.
Winter Storm Warning until 6 AM MDT Friday for WYZ110.
NE...Winter Storm Warning until 6 PM MDT Friday for NEZ002-003-
019>021-054-055-095-096.
&&
$$
SHORT TERM...REC
LONG TERM...MD
AVIATION...MB
FIRE WEATHER...REC
Area Forecast Discussion
National Weather Service Fort Worth TX
726 PM CDT Thu Apr 15 2021
...New Short Term, Aviation...
.SHORT TERM... /NEW/
/Tonight through Friday/
Widespread showers and a few embedded thunderstorms continue this
evening across North and Central Texas. This convection is
occurring within a region of isentropic ascent located to the
north of a stationary front that remains stretched from a surface
low over the southern Sangre de Cristo Range, to the Trans-Pecos
Region of Texas, to the Lower Rio Grande Valley. A few of these
thunderstorms produced hail of one-half to one inch in diameter,
but these storms have since either exited the CWA or weakened.
Instability remains rather weak this far north of the cold front,
which should keep the severe weather potential across North Texas
near a minimum through the overnight hours. While some showers are
likely to continue through much of the night, convection should
wane after midnight. After midnight, some patchy fog may develop
across southwestern portions of the CWA (including the Fort Hood
area), leading to localized visibility reduction to less than two
miles at times.
On Friday, a potent upper-level shortwave trough will move out of
the Southern Rockies and into the Central Plains. Increasing
differential cyclonic vorticity advection will induce surface
pressure falls across the Southern Plains. The aforementioned
surface low over northern New Mexico/southern Colorado will track
southeast, reaching the Texas Panhandle by 12Z, then continuing
southeast through the Red River Valley through the day Friday. The
stationary front will surge northward as a warm front, spreading
a wedge of low to mid 60s dewpoints into Central Texas. HRRR
forecast soundings within the warm sector indicate upwards of
2,000 J/kg SBCAPE, but a closer analysis of these forecast
soundings reveals that the mid-level lapse rates are a fairly
meager 5-6 C/km. These "tall and skinny" CAPE profiles are rarely
associated with large and severe hail, but given that a fair
amount of CAPE will be present and combined with effective bulk
shear magnitudes pushing 70 KT, a few marginally severe
thunderstorms cannot be ruled out.
Thunderstorm chances will end across the region from northwest to
southeast late Friday as the departing surface low pulls a strong
cold front south. This cold front will usher in much drier air,
with winds turning out of the north and increasing to 20-25 MPH.
While just beyond the end of the short-term forecast period, it
is possible we could approach Wind Advisory criteria for a few
hours west of Interstate 35/35W following the frontal passage on
Friday evening.
Godwin
&&
.LONG TERM... /Issued 356 PM CDT Thu Apr 15 2021/
/The Weekend through Next Week/
After an active weather week, it appears that it`ll be less
active this weekend. Cool conditions will persist, however, and
it`ll be quite blustery at least for the early half of the
weekend. Hardly any rain chances are forecast through much of
early next week with rain/storm chances returning Thursday and
into Friday.
Pressure rises near 2mb/hr coupled with strong 850mb cold
advection will equate to sustained north winds of 20 to 25 mph
with gusts as high as 35 mph possible, especially west of I-35. It
appears marginal at this time, but we may need a short-fused Wind
Advisory for parts of the forecast area Friday night into early
Saturday if trends continue. While we have experienced generally
below normal temperatures this week, the thermal pattern appears
very conducive for temperatures to be 10 to 20 degrees below
normal for daytime highs, especially west of I-35. With widespread
cloud cover in conjunction with the wind, it`ll feel like it`s in
the 40s and 50s, though actual air temperatures will climb to
near 60 degrees. IF the cold thermal advection is stronger, these
highs may be too great.
Despite the cloudy skies, dry air will rush in and shunt all of
the low level moisture southward and thus rain is highly unlikely
and the current forecast remains rain-free after 06 UTC Saturday.
Sunday morning will be cool with lows in the upper 30s and mid
40s. Monday morning has the potential to be even a little cooler
as high pressure settles in and a potentially better radiational
cooling period sets up. There`s a non-zero patchy frost potential
and we`ll monitor this over the next several days. However, the
current forecast will abstain from mentioning this explicitly.
As noted above, next week looks largely rain-free. While
temperatures will moderate each day, we will still remain below
normal by at least 4 to 8 degrees. It`s possible that we get a
reinforcing shot of cooler/drier air Wednesday, but there`s only a
few models that advertise this potential. The next rain potential
may arrive late Thursday and into Friday when the initial moisture
surge occurs in response to cyclogenesis to the northwest. At
present time, PoPs remain capped at 40-50%. This pattern may
support some more vigorous storms, so stay tuned for details.
Bain
&&
.AVIATION... /NEW/
/00Z TAFs/
SHRA and a few embedded TSRA continue across much of North and
Central TX. Convection should wane somewhat after 08Z, though some
SHRA are likely to continue through the overnight hours. MVFR CIGs
will gradually lower to IFR overnight, with all TAF sites likely
to be IFR by morning. KACT may experience brief periods of LIFR
CIGs AOB 004 as a warm front lifts north and through Central TX.
TSRA coverage will increase once again as warm front continues
north, reaching KACT by 12Z and D10 terminals by 16Z. Cold front
expected to pass through all TAF sites 21Z-23Z, bringing a wind
shift out of the north and an end to TSRA chances. While just
beyond the end of the TAF period, north winds will increase
markedly after 17/00Z with sustained winds of 20 KT and gusts to
30 KT possible.
Godwin
&&
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 58 68 47 64 44 / 80 90 10 0 0
Waco 60 73 50 64 43 / 70 70 10 5 5
Paris 52 57 47 61 43 / 70 90 20 0 0
Denton 54 64 46 62 40 / 80 90 10 0 0
McKinney 55 63 48 62 41 / 80 90 20 0 0
Dallas 59 68 48 64 46 / 80 90 10 0 0
Terrell 56 65 48 63 43 / 80 90 20 0 0
Corsicana 59 69 47 64 45 / 70 80 20 0 0
Temple 61 75 50 64 43 / 70 70 10 5 5
Mineral Wells 56 70 43 62 42 / 80 80 0 0 0
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
948 PM EDT Thu Apr 15 2021
.SYNOPSIS...
Rain spreads north and east this evening as low pressure takes
shape south of New England. This low will track towards Cape Cod
tonight bringing significant precipitation to the area tonight
into Friday night. Cold air will wrap into the system tonight
changing rain to snow across the higher terrain tonight and then
to low elevations through tomorrow morning. Heaviest accumulations
are likely in the hills and mountains, but light accumulations
are possible all the way to the coast. Low pressure moves away
on Saturday with relatively dry and mild weather expected for
the rest of the weekend and into early next week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
940 PM Update: Webcams and social media reports across
southwest New Hampshire show changeover to snow occurring up to
1 hour before earlier expectations...with snow already coating
roadways at elevations 1.5kft and over. Adjusted temperatures to
account for this...but the overall story for the forecast
overnight remains unchanged. The changeover will spread down
into the valleys /has reached AFN but not EEN/ and then slowly
east. GYX 00Z RAOB shows plenty of dry air aloft still over the
office which will take time to saturate as low pressure
strengthens south of Nantucket. This evolution will keep the
advancing precipitation shield from making much headway north
and east until after midnight. Recent HRRR runs have the overall
evolution handled well and trended the forecast towards them.
Expect a transition to snow over the more highly populated CON-
MHT-ASH corridor in the 7-9am timeframe and will continue to
monitor this for possible impacts to the morning commute.
Have also bumped up winds during the day Friday along the NH and
SW ME coast in line with the HRRR and consistent with MOS output
at PSM/PWM. A few hour period of gusts over 40 mph is possible
centered around or just after noon.
655 PM Update: Primary updates this hour are to lower
temperatures in the rainfall area just a tad...and also bring up
dewpoints...while moving the precipitation shield a bit further
east based on KGYX 88D and surface observations. This doesn`t
result in any significant changes with another 2-3 hours yet
until we expect the changeover to snow to get going /a bit
earlier on the highest hilltops in far SW NH/. This aligns well
with the latest trends in the HRRR and other mesoscale guidance.
Previous Discussion Below...
Forecast looks to be on track as the surface low off the
Delmarva Peninsula is beginning to deepen at this hour. Rain
shield ahead of the secondary low and parent surface low
associated with the upper level trough over New York continues
to blossom and expand. Rainfall has begun through most of New
Hampshire already and it will very slowly progress eastward this
evening as drier air is being entrained into Maine as the
easterly mid-level flow takes hold. Overall model guidance
hasn`t changed significantly over the last 12 hours in regards
to changeover timing tonight. 12z HREF and other guidance still
shows changeover to snow occurring tonight across SW NH from 9PM
to midnight as precip rates increase and dynamic cooling occurs
as the 850 and 700mb low deepen. Still looks like the most
significant accumulations after midnight will be above 1K in the
Monadnock Region. Snow will continue to changeover to lower
elevations further east as the night progresses with a wet snow
or rain/snow mix for most of NH and SW Maine by daybreak.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Difficult forecast for Friday in regards to snowfall
accumulations that will be driven by precipitation rates across
elevations below 1K. Impacts during the morning commute are
still uncertain as the low and FGEN forcing peak in intensity
from 12 to 18Z with the surface low deepening to around 992Mb
before it becomes occluded and vertically stacked by Friday
afternoon somewhere over the Cape. The low will then pivot and
drift eastward through Friday night. Guidance is in good
agreement of 1.5" of QPF for SW NH and upslope regions of the
Whites with 1 to 1.5" for the remainder of the area. The heavier
precip access looks to get off by 18Z over Southern NH and
pivots further north into Maine through the afternoon and
evening hours. A second burst is even possible across the Mid-
Coast and Capital District by evening, which could lead to some
evening travel impacts as the sun sets.
Overall snowfall amounts will be extremely elevation dependent
with 500ft making significant differences in amounts and
snow loads on trees. Due to the very wet snow and low snow
ratios, expecting heavily weighed down trees which will lead to
sagging and snapped tree branches. Most area will see isolated
power outages but some areas, especially those areas above 1K in
SW NH where 6 to 8" of snow could fall, will see scattered
outages. Overall looks like a moderate impact event due to
travel issues and snow load issues for the region. Evening and
mid shift will watch how things trend down and make snowfall
forecast adjustments as needed. Only headline change this
afternoon was to add a winter wx advisory to interior Cumberland
and Androscoggin counties for heavy wet snow.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Vertically stacked low pressure system will be in the Gulf of Maine
Saturday morning and will start weakening as it pulls away from the
area Saturday afternoon. Precipitation will end from west to east
with clouds lingering into Saturday night. As this system generated
its own cold air temperatures will be 10 degrees warmer Saturday
than Friday despite northerly winds. With little in the way of dry
air advecting into the region behind the system, clouds will linger
Sunday with a warming trend into Tuesday. Disturbances aloft will
bring low chances for for a shower Monday with a cold front
approaching late Tuesday crossing the area Wednesday with more
widespread showers.
The bulk of the impacts from our spring Nor`Easter will be winding
down Saturday as the vertically stacked system starts to weaken.
Winds will turn northerly with lingering gusts to 25 mph near the
coast with precipitation ending early morning across western New
Hampshire and eastern zones towards mid-day. Highs Saturday will
generally be in the 40s. There remains enough moisture that lingers
to maintain clouds and slight chances for rain and snow showers in
the higher terrain of the White Mountains.
A warming trend starts Sunday despite lingering clouds. Upper level
disturbances will keep low chances for a shower in the forecast
Sunday afternoon and Monday afternoon, but for the most part, mostly
dry weather is expected. Deep SW flow will develop ahead of an
approaching cold will leading to H8 temps to climb to 5C translating
to highs into 60s with highs approaching 70F in the Merrimack
Valley. The front will cross the area sometime Tuesday night through
Wednesday bringing widespread showers.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Short Term...
Summary: Low pressure passing south of the area will bring
widespread rain and snow to the region through Friday night
along with strong winds during the day Friday.
Restrictions: Deterioration to LIFR/IFR with some periods of
VLIFR possible as rain transitions to snow from southwest to
northeast. Some questions remain with precipitation type esp for
coastal terminals on Friday...but restrictions will remain
LIFR/IFR through the day regardless. Some gradual improvement to
restrictions is possible Friday night...but IFR will remain
possible.
Winds: Winds will gradually become northeasterly and slowly
strengthen overnight with gusts over 20kts likely for coastal
terminals before daybreak. East/Northeasterly winds will
strengthen on Friday...reaching 25G35kts along the coast...with
15G25kts inland. Winds shift northwesterly and gradually
diminish Friday night.
LLWS: While winds will strengthen aloft Friday morning...good
boundary layer mixing should preclude any LLWS layers during the
day.
Snowfall rates: Rates look to remain below 1" per hour at any
time for the terminals. The snow will be wet with temperatures
near freezing.
Long Term...IFR/MVFR likely Saturday morning with conditions
improving to MVFR/VFR from west to east Saturday afternoon. Mainly
VFR Sunday into Tuesday with low confidence in periods of MVFR with
low cigs and -SHRA primarily Monday afternoon.
&&
.MARINE...
Short Term...A rapidly developing area of low pressure south of
the Cape will stall across the Gulf of Maine during the day
tomorrow. Strong easterly winds north of the low will bring Gale
conditions through the coastal waters during the day tomorrow.
Winds and waves will trend down tomorrow night but SCA
conditions are still likely after midnight.
Long Term...Northerly winds gusting 25 to 30 kts Saturday morning will
drop below 25 kts Saturday afternoon. Seas will run in excess of 5
ft Saturday with seas dropping below 5 ft Saturday night. A cold
front will approach Tuesday leading to increasing SW flow with SCA
conditions possible late Tuesday into Wednesday.
&&
.TIDES/COASTAL FLOODING...
System gradually intensifies before retrograding through the
far southern portions of the Gulf of Maine tomorrow. This type
of system usually leads itself to moderately high storm surge
values, and indeed ESTOFS is forecasting about a two foot surge
tomorrow. The coupled wave action should lead to some minor
beach erosion and this is validated by the USGS wave runup
models. However, this is a borderline situation for splash-over
as we are at a low part of the astronomical tide cycle. Will
continue to monitor. If an area were to have minor splash-over
issues, it would be the beaches south of Portland to the
Massachusetts border tomorrow.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Storm Warning until 6 AM EDT Saturday for MEZ007-008-
012-013-033.
Winter Weather Advisory from 8 AM Friday to 6 AM EDT Saturday
for MEZ019-020.
Winter Weather Advisory from 2 AM Friday to 6 AM EDT Saturday
for MEZ018.
NH...Winter Storm Warning until 6 AM EDT Saturday for NHZ002>009-
011-015.
Winter Weather Advisory from 2 AM Friday to 6 AM EDT Saturday
for NHZ010.
Winter Weather Advisory until 6 AM EDT Saturday for NHZ001.
MARINE...Gale Warning from 7 AM Friday to midnight EDT Friday night for
ANZ150>154.
&&
$$
SYNOPSIS...
NEAR TERM...Arnott
SHORT TERM...
LONG TERM...
AVIATION...Arnott
MARINE...
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Melbourne FL
828 PM EDT Thu Apr 15 2021
.DISCUSSION...
Weak cold front will push slowly southward through north Florida
into tonight, with low level cloud cover gradually building across
the area overnight. Unsettled pattern aloft and approaching front
may be able to develop a few showers or isolated storms after
midnight, mainly near to north of a line from the Orlando/Kissimmee
area to Cape Canaveral. However, recent HRRR runs have steadily
backed off on any precip and latest GFS MOS keeps PoPs out of the
forecast through daybreak. Will keep low end PoPs around 20-30
percent across this area, otherwise it looks like most areas
should remain dry tonight, especially south of Orlando. Temps will
remain mild, with lows in the 60s.
&&
.AVIATION...VFR conditions expected through the remainder of the
evening, with stratus gradually building in across the region, south
of an approaching cold front. Predominant MVFR cigs looks likely
after 08Z, especially north of KVRB-KSUA, with the potential for
IFR cigs around daybreak. This lower cloud cover is forecast to
linger into the morning with gradual improvement to VFR into the
afternoon.
Could see a few showers and an isolated storm or two late tonight
from KMCO/KISM-KTIX northward. Otherwise, better chance for
showers and storms will be into the mid to late afternoon Friday,
near to north of Melbourne, as front stalls out across north
central Florida. Isolated stronger storms will be possible through
late day.
&&
.MARINE...S/SW winds from the Cape southward will decrease to
10-15 knots late this evening, with winds then generally out of
the W/NW after midnight as cold front moves gradually southward
through north Florida. Seas will range 2-4 feet.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 64 79 63 85 / 20 50 20 20
MCO 67 84 65 88 / 20 40 10 10
MLB 66 85 65 89 / 10 30 10 10
VRB 64 87 63 90 / 10 20 10 10
LEE 67 82 66 85 / 30 50 10 20
SFB 67 83 65 88 / 20 50 10 20
ORL 68 85 68 88 / 20 40 10 20
FPR 64 87 63 90 / 10 20 10 10
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Weitlich/Cristaldi
Area Forecast Discussion
National Weather Service San Angelo TX
620 PM CDT Thu Apr 15 2021
...New AVIATION...
.SHORT TERM...
(This evening through Friday)
Issued at 214 PM CDT Thu Apr 15 2021
Showers and thunderstorms across the Big Country into
Coleman...Brown and Saba Counties continue to move eastward at 2
PM. Isolated thunderstorms continued to become severe, with large
hail being the main hazard. MUCAPES were still in the 2000 J/KG
range with 0-6KM bulk shears of 50 to 60 KTS...promoting the
supercells that produced several reports of golfball to ping pong
size hail, with up to baseball size hail at Loyal Valley in SE
Mason county.
Isolated severe hail will continue to be possible into this
evening with warm advection over cold air over the surface.
However, severe storms will be more isolated.
Areas of fog are likely tonight into early Friday morning as a
warm front moves through. Patchy areas may become dense
overnight.
Drier air will move in midday and afternoon Friday ahead of a
cold front that will move into the region in the afternoon. The
best chance of showers and isolated thunderstorms will be eastern
sections.
&&
.LONG TERM...
(Friday night through next Thursday)
Issued at 214 PM CDT Thu Apr 15 2021
Much cooler air will advect into the region Friday night with lows
in the lower 40s, and Highs Saturday in the 50s. Mid level
sprinkles are possible Saturday and Sunday in Crockett county and
the western Concho Valley...and possibly farther east across much
of the Concho Valley/Crockett county on Monday. Unfortunately the
air at the surface will be dry so amounts will be light if they
make it to the surface. A few sprinkles are also possible
Thursday as an upper shortwave moves across.
&&
.AVIATION...
(00Z TAFS)
Issued at 614 PM CDT Thu Apr 15 2021
Main area of showers and storms are pushing away from West Central
Texas terminals early this evening, leaving LIFR/IFR conditions
for the overnight hours with low clouds and drizzle/fog. Latest
HRRR suggests some potty showers likely again around sunrise for
the eastern terminals, but remains uncertain given the struggle
the models have in pinpointing this type of shallow lift with
relatively low based convection. Have included a VCSH mention in
the eastern and southern locations for now. Conditions will
improve by late Friday morning and into the afternoon as surface
winds swing to the southwest and start to erode the shallow cooler
air mass, with VFR and gusty north winds following a stronger cold
front into the area Friday afternoon.
&&
.PRELIMINARY POINT TEMPS/POPS...
Abilene 57 74 42 56 / 40 40 5 5
San Angelo 59 81 43 58 / 30 5 5 10
Junction 60 85 45 59 / 30 20 5 10
Brownwood 57 77 43 59 / 40 50 5 5
Sweetwater 57 73 42 54 / 30 20 5 10
Ozona 62 83 45 58 / 30 5 5 20
&&
.SJT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...04
LONG TERM....04
AVIATION...07
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