Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/22/17
Area Forecast Discussion
National Weather Service Bismarck ND
1009 PM CDT Fri Apr 21 2017
.UPDATE...
Issued at 1001 PM CDT Fri Apr 21 2017
Weak shortwave energy and surface convergence near developing
low pressure and an approaching cold front is occurring over
northeast Montana. This has produced some lightning over the past
few hours as convection tracks across far northeast Montana. Did
add some small pops far northwest ND to account for this late this
evening. Think thunder will have ended by then.
Otherwise no significant changes to the going forecast. updated
pops with latest consensus blend of short term models, which was
not much change from the previous forecast. Kept a mention of
patchy fog also across the far north. Updated text products will
be sent shortly.
UPDATE Issued at 640 PM CDT Fri Apr 21 2017
High pressure over central North Dakota will move slowly southeast
tonight. Light and variable winds with mostly clear skies tonight.
A cold front will drop south into the area bringing increasing
clouds from north to south during the day. No significant changes
to the going forecast at this time other than populating latest
sensible weather elements.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 258 PM CDT Fri Apr 21 2017
Latest GOES16 mid level water vapor and visible imagery indicates
the mid/upper level high was centered over northeast South Dakota
this afternoon, while the surface high pressure resided over
Streeter ND, in Stutsman County. Large fair weather cumulus field
dominated south central ND and the James River Valley. Elsewhere
sct/bkn cirrus clouds were becoming dominant in western ND along
with a few fair weather cumulus underneath. Dry weather will persist
through the evening, then the high pressure area is squashed
farther south through the short term period. Heights and thicknesses
lower from north to south through Saturday, in response to a surface
cold front and associated shortwave now located over south central
Saskatchewan and into Manitoba. This cold front will slide into
northern ND 09z-12z Saturday, gradually sagging into central ND
21z Sat-00z Sun. Will add some patchy fog late tonight into
Saturday morning, along and just behind the cold front in far
northern ND including the Turtle Mountains. This has support from
the HRRR and RAP13. With the thickness packing/baroclinic zone
remaining along and north of Interstate 94 through 00z Sunday,
expect much warmer conditions across southern ND versus northern
ND. Main impact in southern ND with the proximity of the sagging
cold front in the afternoon will be some increase in cloud cover.
Highs Saturday will range from the 40s north, to the mid 60s
south. The NAM/GFS QG fields shows the best alignment/overlap in
forcing, 850-700mb frontogenetical forcing and 500-300mb synoptic
scale ascent, resides over northern ND. Pops/rainshowers essentially
stretch and increase from Renville County east to Rolette County,
and south into Wells County through Saturday afternoon.
.LONG TERM...(Saturday night through Friday)
Issued at 258 PM CDT Fri Apr 21 2017
The front/baroclinic zone sags into northern South Dakota Sunday,
with the area of forcing mentioned in the short term discussion
continuing over north central ND. Ascent does spread a bit farther
south, along and north of a line from Williston to Jamestown
Saturday night through Sunday. Some concern for minor snowfall
accumulations Saturday night and into Sunday morning along and
north of Highway 2 where up to one inch of snowfall is forecast
before the precipitation mixes with and changes back over to
rainshowers in the afternoon. Main effect across southern ND
Sunday will be more cloud cover and cooler temperatures, but
remaining dry through the day. Highs across the north Sunday
continue in the upper 30s to lower 40s, while mid 50s to lower 60s
occur in the south.
Once the baroclinic zone slips into South Dakota Sunday, we really
never recover back into the 60s for the rest of the long term
period. An active/cooler period ensues with periodic chances of
rain/snow. Sunday night through Monday will be our next round of
precipitation. Accumulating snow of another inch is possible
across northern ND from late Sunday night through Monday morning.
Elsewhere precipitation will fall as rain. Highs Monday will range
from the upper 30s north to lower 50s south. Tuesday will be the
coldest day with highs generally in the 40s across western and
central ND. Precipitation chances will mainly be confined to
western ND Tuesday and Wednesday.
Will need to monitor at least one potent system ejecting across
the Central Plains and possibly curling back into the northern
plains Thursday through Friday. Both the ECMWF and GFS spread
precipitation across western/cental ND, but the GFS is more widespread
and heavier with precipitation amounts versus the ECMWF. Main
reason is because the Operational/Deterministic GFS track brings
the low pressure into ND, while the ECMWF track is farther east.
The GFS Ensemble Mean favors a track farther south and east from
the Operational GFS. Thus, at this time, perhaps one would lean
towards more of a ECMWF solution. Highs during this period remain
in the 50s.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1001 PM CDT Fri Apr 21 2017
A cold front will move south through the northern TAF sites of
KMOT and KISN tomorrow. This will bring a chance of MVFR ceilings
and a few sprinkles to KISN and KMOT Saturday morning. Mesoscale
and global models are in pretty good agreement bringing the cold
front through KISN and KMOT around 15 UTC. What they do not agree
on is the amount of low level moisture with the front. Currently
the mesoscale models bring MVFR-IFR clouds into the state
quickest, while the NAM and especially the GFS hold off on
bringing lower ceilings south. lower ceilings can be seen across
southern Canada and clouds will make it south to at least the
northern TAF sites. For now though, just brought MVFR ceilings
for a period to KMOT Saturday morning, before raising to VFR.
Winds will shift north to northeast behind the cold front.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...TWH
SHORT TERM...KS
LONG TERM...KS
AVIATION...TWH
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
655 PM CDT Fri Apr 21 2017
.DISCUSSION...Updated for latest aviation discussion below.
&&
.AVIATION...Mainly VFR should prevail over the next 24 hours.
Breezy SE winds of this afternoon have already begun to settle
down. Overnight, expect that a low cloud deck will form around
midnight at 020-025, but confidence not particularly high that a
ceiling will prevail. SREF probabilities of MVFR CIG`s only in
the 20-30% range, and RAP BUFKIT soundings showing the thickness
of the cloud layer to be rather shallow. Patchy fog was inherited
in the public forecast grids, but currently thinking that winds
will stay up enough to prevent temps from cooling to the dewpoint.
SE breezes return mid-morning on Saturday, but should weaken by
mid-afternoon and back somewhat as the pressure gradient
decreases ahead of an approaching cold front.
At this time, model solutions are consistent in keeping the cold
front north of the RGV airports through 23/00Z. Isolated
convection may develop along and behind the front tomorrow
evening, with MFE perhaps being favored.
&&
.PREV DISCUSSION... /issued 245 PM CDT Fri Apr 21 2017/
SHORT TERM (Tonight through Saturday Night): The most
significant event in the short term portion of the forecast will
be the passage of a weak cold front through Deep South Texas and
the Rio Grande Valley early Saturday evening through early
Saturday night. The Storm Prediction Center has placed the entire
BRO CWFA in a general risk of thunderstorms from Saturday morning
through Sunday morning, and isolated showers and thunderstorms
will be included in the upcoming local forecast from Saturday
afternoon through Saturday night. Temperatures will prevail at
above normal levels in advance of the front, but cooled to below
normal levels Saturday night in the wake of the front.
LONG TERM (Sunday through Friday): Have not made any significant
changes to the forecast this afternoon. Current thinking is that
some light lingering rain will be possible across the Lower RGV
for a few hours Sunday morning, with the cold front now south of
the region. Any precip should exit the Deep South Texas by mid to
late morning with cloud cover continuing to hold on over the RGV
through mid day. After that, high pressure will build south into
the area will much drier Plains air. This will erode away cloud
cover rather quickly, with mostly sunny skies by the afternoon.
The real story will be how much cooler it will Sunday, with
readings topping out nearly 10 degrees lower than the day before.
By Monday morning, under mostly clear skies and near calm to light
high pressure winds, temperatures will have fallen into the 50s
for much of the areas, with the exception of locations right along
the coast. In fact, these readings could be around 10 degrees
below normal lows for late April. With ridging aloft and surface
high pressure in place to start the new work week, the dry air
will warm quickly and highs Monday will be right back to near
normal. The warming trend will continue through the week, with
both highs and lows warming a few degrees each day. Triple digit
readings across the mid to upper RGV and Western Ranchlands are
likely Wednesday though Friday, with mid to lower 90s from the
mid valley towards the coast. Meanwhile, the forecast is expected
to remain rain free.
MARINE:
Tonight through Saturday Night: Buoy 42020 reported south winds
around 12 knots with seas slightly under 3.5 feet with a period of
8 seconds at 13 CDT/18 UTC. Generally moderate winds and seas
will prevail along the Lower Texas Coast in advance of a cold
front, which will sweep from north to south through the waters
from early Saturday evening through early Saturday night.
Increasing winds and building seas are likely in the wake of the
front, and Small Craft Advisories may be needed for all or
portions of the Lower Texas coastal waters Saturday night after
midnight.
Sunday through Tuesday: Hazardous winds and seas will continue
across the Gulf waters on Sunday, with any SCAs from the night
before continuing into the morning or afternoon hours due to the
tight surface pressure gradient behind the front. The winds and
seas will improve later on Sunday as high pressure quickly
settles across Deep South Texas and the Western Gulf with the
gradient relaxing. Light winds and lows seas will be noted on
Monday and for the better part of Tuesday. However, by later on
Tuesday, the pressure gradient will quickly tighten as the surface
high pressure shift into the Central Gulf of Mexico and interacts
with another developing low pressure system across the Panhandles
of Texas and Oklahoma. Winds and seas may approach SCA conditions
by Tuesday evening.
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
This product is also available on the web at:
HTTP://WEATHER.GOV/RGV
53-Schroeder...Aviation/Short-term
59...Long-term
56...Graphicast/Upper-Air
Area Forecast Discussion
National Weather Service State College PA
1120 PM EDT Fri Apr 21 2017
.SYNOPSIS...
A stalled frontal system just to the south of the Commonwealth
will keep the region flirting with clouds and precipitation
into the weekend.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Meso anal shows northerly winds finally establishing across the
entire CWA as the surface low over the Mid Atlantic settled
slowly south.
The rest of the overnight should remain dry with clouds
returning from the southwest. Overnight lows in the 30s and 40s
will average near normal over the north, and some 5-10 warmer
than normal over the south.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
Latest HRRR is very aggressive returning the rain into the
southern half of my CWA during the hours just after sunrise, and
continuing well into the afternoon hours. I adjusted POPs up a
bit to cover this, but I suspect they are still underdone. From
about I-80 south it could be a rather chilly and wet Saturday
with the driest weather indicated over the northern tier.
Highs will average in the 50s, or some 5-10 deg cooler than
normal for a change.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
The period of Sunday to Wednesday will be dominated by the flow
around a slow moving cut-off low which eventually will pass to
our south and east. This system will bring clouds and light rain
to the parts of our region for several days. Once this system
goes by large scale retrogression will put our region on the
western edge of a relatively strong 500 hPa ridge and it will
get warm fast. It should feel like summer by next Thursday.
Sunday weak high pressure and low moisture values should provide
for a relatively nice day. We will be well north of the frontal
boundary.
Monday the low to our south begins its slow journey towards
the Carolina coast. Our PW values come up and the threat of QPF
in the GEFS/SREF and CMCE show increased chance of light rain
overnight Sunday into Monday. Best chance of rain should be in
southeastern PA. The potential for rain will be higher in
southeastern PA and much lower in northwestern PA. Rainfall will
likely be very light and the best chance for measurable
rainfall will in southeastern PA. Enjoy the mostly cloudy and
relatively cool weather while it lasts.
As the 500 hPa low fills and the attendant moves to our
northeast the chance of rain should fall off Wednesday into
Wednesday evening. Our 850 hPa temperatures will rise rapidly
Wednesday and it should be noticeably warmer Wednesday relative
to Monday and Tuesday.
Thursday into Saturday the 850 hPa temperatures will be well
above normal, mainly in the 14 to 16C range and we will be on
the western edge of a rather impressive early season subtropical
ridge. The GEFS and GEFSBC show a closed 5880 m ridge along the
VA/NC/SC coast with +2 sigma height anomalies by Fri-Sat.
Thus Thursday through at least Saturday should be very warm and
humid. We should have several days with high temperatures well
into the 80s. Any precipitation after Wednesday will likely be
in a more summer-like atmosphere so added thunder in all
forecasts beyond Wednesday.
The ridge will likely continue retrograding. If the NEAFSBC and
GEFSBC are correct we could be looking at our first enduring
period of warm weather from this coming thursday into the
following week.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Fcst in good shape. Very minor adjustments to 03Z
TAF updates.
Earlier discussion below.
Mainly just mid and high clouds now.
A few showers just south of MDT.
Did cut back on lower clouds some later tonight
and Saturday. Left some lower clouds in at JST and
BFD.
Perhaps a shower in a few spots this weekend, but
mainly dry, not bad for mid to late April.
Outlook...
Sun-Tue...No sig wx expected for much of this period.
However...Rain/low CIGs possible at times...mainly across
southern PA.
Wed...Improving conditions.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...Dangelo/Gartner
LONG TERM...Grumm
AVIATION...Martin
Area Forecast Discussion
National Weather Service Cheyenne WY
951 PM MDT Fri Apr 21 2017
.UPDATE...
Issued at 942 PM MDT Fri Apr 21 2017
Evening water vapor loop showed a mid/upper level low circulation
located over central Wyoming. An inverted surface trough extended
south across west central CO into northern NM. Moist upslope
southeasterly flow and weak forcing aloft still producing light
rain and snow showers across much of southeast WY into far western
NE this evening. Snow levels are expected to fall to near 5500
ft tonight with changeover to all snow. Additional accumulations
up to an inch expected, mainly for higher elevations of southeast
WY. Areas of fog, dense in spots, will likely form late tonight
from the Laramie Valley east into Laramie County. Also concerned
about very slick roadways as temperatures fall into the 20s,
especially along the I-80 corridor between Cheyenne and Laramie.
The Winter Weather Advisory remains in effect for the southern
Laramie Range and foothills through 8 AM Saturday.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 411 PM MDT Fri Apr 21 2017
Rain and snow continuing to diminish very slowly this afternoon
with the most concentrated area holding over the far southwest
Panhandle into far southeast Wyoming. Radar showing a small
circulation center over far northern Colorado southeast of
Cheyenne...which has only drifted slowly southeast this afternoon
and helped to keep somewhat enhanced pcpn going.
Models continue to show a slowly diminishing area of pcpn over
mainly southeast Wyoming overnight as a secondary shortwave drops
southeast across the area. Additional snowfall amounts should be
light but given rather cold temperatures overnight and the
potential for freezing of water and additional snowfall between
Cheyenne and Laramie have opted to post a winter wx advy for that
area into Saturday morning. Some fog...possibly dense...also a
likelihood over far southeast Wyoming overnight.
The weekend will see warming temperatures with any lingering pcpn
ending Saturday morning and upper ridging nosing into the region.
Skies expected to clear out during the day Saturday with max temps
rebounding into the 50s to mid 60s...and in the 60s and the 70s
over lower elevations Sunday as the upper ridge slides by.
.LONG TERM...(Sunday night through Thursday night)
Issued at 411 PM MDT Fri Apr 21 2017
A fast zonal flow pattern will be overhead through the middle part
of the week with embedded midlevel disturbances moving through the
flow. Expect chances for showers and afternoon t-storms through
this time. Temperatures look to be warm enough to keep precip type
mainly rain, except for the mountains and Laramie Valley where we
may see temps drop below freezing during the overnight hours to
support snow. Westerly winds will be on the breezy side as well
in this pattern. A deeper upper low is progged to dig into the
Rockies on Wednesday and Thursday although GFS/ECMWF differ quite
a bit at timing and strength of this system. Will keep it simple
and just maintain chances for precip through this time, along
with a trend towards cooler temperatures.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 530 PM MDT Fri Apr 21 2017
VFR CIGS will prevail tonight, except invof KCYS where IFR-LIFR
CIG/VIS in fog develops 03Z-04Z. HRRR model introduces MVFR-IFR at
KLAR and KSNY, and MVFR at KRWL by 09Z tonight. These low conditions
will likely persist through late Saturday morning. Winds will be
variable less than 10 kt through the TAF period.
&&
.FIRE WEATHER...
Issued at 411 PM MDT Fri Apr 21 2017
Concerns look to remain low through the weekend into early next
week given wetting pcpn over much of the area today and min RHs
remaining above critical levels.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until 8 AM MDT Saturday for WYZ116-117.
NE...None.
&&
$$
UPDATE...MAJ
SHORT TERM...RE
LONG TERM...RJM
AVIATION...MAJ
FIRE WEATHER...RE
Area Forecast Discussion
National Weather Service Dodge City KS
1022 PM CDT Fri Apr 21 2017
...UPDATE TO AVIATION...
.SYNOPSIS...
Issued at 1020 PM CDT Fri Apr 21 2017
WV imagery indicates an upper level shortwave trough of low pressure
transitioning eastward across the Central Plains. Meanwhile, weak upper
level ridging is moving slowly eastward across the Pacific Northwest
and northern California. Near the surface, a broad area of high pressure
is shifting slowly east across the Upper Midwest.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 241 PM CDT Fri Apr 21 2017
An upper level trough was passing across western Kansas
this afternoon. Widespread rain was occurring on the
cool side of the front and this was keeping temperatures
from rising out of the 40s to lower 50s. This system will
pass off to the east tonight, with surface high pressure
building into western Kansas through Saturday. Temperatures
tonight should fall into the mid to upper 30s in far western
Kansas where skies may partially clear toward morning, with lower
40s in south central Kansas. Saturday will be partly to mostly
sunny and warmer with highs in the upper 50s to lower 60s.
.LONG TERM...(Saturday night through Friday)
Issued at 241 PM CDT Fri Apr 21 2017
Near freezing temperatures are possible Sunday morning with
clear skies and light winds. A frost advisory will likely be
needed for Dodge City westward to the Colorado line. Several
upper level disturbances will pass across the central plains
next week but low level moisture will be limited this far
west. There are small chances for showers and thunderstorms
with each system. Severe storm chances look rather limited
although it cant be ruled out, especially over south central
Kansas. Highs will warm to near 70 degrees Sunday and then
into the lower 80s by Monday before gradually falling into the
high 60s by Thursday. The best chance of rain is Wednesday
night as a stronger system passes. However, with all the day to
day changes in the various model solutions, confidence is very
low in a widespread precipitation event.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 610 PM CDT Fri Apr 21 2017
Two upper level waves will rotate around an upper low as it moves
east across the central plains overnight and Saturday. One of
these upper waves this evening will move into central Kansas after
sunset, and as it does the ongoing precipitation at 00z Saturday
across western Kansas will taper off from west to east. Model
soundings differing on how quickly ceilings will improve overnight
once this first upper wave passes but based on the past few
observations trends across western Kansas will favor the more
progressive RAP on improving ceilings and trend towards VFR
ceilings At HYS at the start of the 00z Tafs cycle. Ceilings at
GCK and DDC should have low VFR ceilings developing between 03z
and 09z Saturday. Gusty northerly winds early this evening will
fall back to around 10 knots by 06z Saturday and then continue
through Saturday afternoon as a surface high builds into western
Kansas. Wind direction along with stronger winds forecast in the
boundary layer does not favor dense fog development overnight but
given the recent rains and light winds tonight can not rule out
some patchy fog will be possible.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 38 58 34 69 / 70 0 0 0
GCK 36 58 32 70 / 40 0 0 0
EHA 36 57 35 72 / 0 0 0 0
LBL 37 58 33 71 / 10 0 0 0
HYS 39 59 36 70 / 80 0 0 0
P28 41 59 37 69 / 80 0 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...JJohnson
SHORT TERM...Finch
LONG TERM...Finch
AVIATION...Burgert
Area Forecast Discussion
National Weather Service Duluth MN
645 PM CDT Fri Apr 21 2017
.UPDATE...
Issued at 645 PM CDT Fri Apr 21 2017
Please see the 00Z Aviation Discussion below.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 319 PM CDT Fri Apr 21 2017
An area of high pressure over eastern Dakotas will shift south
through Saturday, maintaining the clear skies across the Northland
through at least tonight, if not much of Saturday. The clear
skies, light wind flow, and low dew point temperatures tonight
will promote radiational cooling. Temperatures should drop into
the lower 30s. Some areas in northern Wisconsin and far northern
Minnesota could get into the 20s. It appears to be too dry to
warrant patchy fog in the forecast, but it is not impossible.
Breezy westerly flow will develop Saturday with the good heating
and resulting mixing. The increasing westerly flow aloft, ahead of
a cold front approaching from the north, could support gusts to
around 20 mph. Leaned on the warmest guidance for temperatures
considering the scenario and dry conditions. Manually increased
the highs for downtown Duluth and Canal Park because the westerly
flow will be strong enough to stave off a lake breeze, and to
account for downslope warming. Downtown Duluth and the city of
Superior should reach highs similar, if not warmer, than inland
areas in the higher terrain.
There will be increasing clouds from the north Saturday afternoon
as the cold front works its way into the Borderland areas. There
could be middle to late afternoon rain showers.
.LONG TERM...(Saturday night through Friday)
Issued at 319 PM CDT Fri Apr 21 2017
Main concern for the short term will be precip chances and type
during the forecast period.
A weak shortwave will move along the international border sunday
night bringing a chance for a rain and snow mixture to areas mainly
north of Highway 2. There not as much moisture with this shortwave
so the precipitation will be scattered in nature. On Monday and
Monday night, a stronger shortwave will move through MN along with
a deep low pressure area moving across the state Monday afternoon
and Monday night. There is more moisture with this system so the
precipitation will be more widespread. As like the previous night,
the rain will change over to a rain/snow mixture Monday night and
Tuesday morning. There will be some accumulation but there are
still some differences with amounts. The best area for snow
accumulation will be north of Highway 2.
A small area of high pressure will build into the forecast area
Tuesday afternoon keeping the area precip free through Thursday
morning. The next strong system will affect the region Thursday
afternoon into Saturday. Models to show major differences in
solution with the GFS having the low center in SW MN at 18z Fri
while the ECMWF has the center near GRB. Canadian has the low in
Southern WI. The GFS takes the low west of the forecast area Friday
night which would keep warmer air over the area. The ECMWF has the
low center moving through the northern great lakes which will make
it colder. So there are still major differences in ptype and
amounts. Temperatures will be colder than normal next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 645 PM CDT Fri Apr 21 2017
VFR conditions through the TAF period with high pressure building
over the region. Winds will remain light and skies clear. The
latest RAP hints at radiation fog development at KHIB/KBRD late
tonight. Not confident at this point that fog will develop, but
will continue to monitor as the night progresses.
A backdoor cold front will move southward into the International
Border Saturday afternoon/evening. This will spread rain showers
into KINL and bring the possibility of MVFR ceilings towards the
end of the TAF period per the DLHWRF/NAM. There is some
instability ahead of the front, so a few thunderstorms cannot be
ruled out. Held off for now on including thunderstorms in the
KINL TAF. Gusty winds will develop at KINL/KHIB and KDLH as the
pressure gradient tightens due to the incoming front and the
exiting high.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 35 63 35 41 / 0 0 50 30
INL 35 60 30 45 / 0 20 40 20
BRD 35 65 39 54 / 0 0 20 20
HYR 29 64 37 52 / 0 0 10 20
ASX 31 67 35 43 / 0 0 40 30
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
UPDATE...WL
SHORT TERM...Grochocinski
LONG TERM...Stewart
AVIATION...WL
Please see the 00Z aviation forecast discussion below.
AVIATION...
VFR conditions are in place at area TAF sites and this will continue
through the remainder of the evening. Low cloud should first develop
along the I-35 corridor around 06Z (around 11Z at DRT), with bases
initially low end MVFR. Cigs should lower into IFR between 10-12Z
along I-35, with DRT still low end MVFR. We could also see some fog
develop at the I-35 terminals, but suspect cigs will be the main
concern. As the front moves through early tomorrow morning, northerly
winds will increase and become gusty around 18Z. We could also see a
shower or two develop along the front, but with chances low, we will
not mention in the forecast at this time. Afternoon wind gusts could
approach 25 kt between 18-00Z tomorrow. We should see enough drying
in the low-levels to allow cigs to rise and clouds to gradually thin
late tomorrow afternoon or early in the evening. For now, will show
improvement to VFR at AUS around 21Z, with remaining terminals still
likely still in the upper end of MVFR.
PREV DISCUSSION... /ISSUED 243 PM CDT Fri Apr 21 2017/
SHORT TERM (Tonight through Saturday)...
Only weather focus remains centered on the frontal passage expected
overnight/early Saturday morning that will bring gusty north winds of
20-25 mph but with only a thin line of showers that will not amount
to much rainfall accumulation. Much cooler temperatures are expected
Saturday afternoon and through the initial part of next week.
A strong shortwave trough is shifting across the south-central
Plains this afternoon and supporting a large storm system across
Oklahoma and north Texas. This storm activity will remain well north
of the region with no activity expected across south-central Texas
due to lack of forcing and a very strong capping inversion in place.
Given the surface low development across north Texas in response to
this system, gusty south to southwest winds are ongoing this
afternoon. Gusts could reach as high as 20 to 25 mph at times but
should subside through the evening hours as vertical mixing
decreases and effective boundary layer contracts.
Weather conditions will continue to be mild and pleasant through the
evening hours tonight as the front is not expected to enter the Hill
Country and northern I-35 corridor until 3am or so. As mentioned
earlier, forcing will remain north of the region, and with weak
lapse rates with little instability with continued weak capping
still in place with the frontal passage, only am expected a thin
light of light showers to come through south-central Texas. Attempted
to time it in weather and rain chance wise in 3 hour blocks through
the overnight hours. Front should be through Austin and San Antonio
through 9am Saturday morning, if not earlier. Strong north winds of
20-25 mph will be likely following frontal passage. Winds will
slowly decrease through the afternoon hours with slowly clearing
skies from north to south by late in the day. However, a good portion
of Saturday appears cloudy per model soundings. If thicker clouds
remain in place, high temperatures may struggle to reach into the low
to mid 70s.
LONG TERM (Sunday through Friday)...
Well-below normal temperatures are expected Sunday and Monday morning
with readings in some locations approaching record lows within a few
degrees. Warming will return however by mid- and late-week with
south to southwest flow returning. While most of the next 7 days will
be dry, rain chances look to increase late next week.
Skies are expected to clear with weak winds Sunday and Monday as
surface high pressure develops over the southern plains. This will
allow for some of the coolest temperatures in the past several months
to occur. With dewpoints in the mid 30s and radiant cooling
conditions nearly optimized, low temperatures are expected to fall
into the low to mid 40s in the Hill Country and the upper 40s to near
50 elsewhere. Low temperatures were lowered 2-3F degrees from
guidance given the pattern set-up and the likely over achieving of
cooling a greater possibility. Despite the cold mornings, a nice
warm up each afternoon is expected given the dryness of the air.
Moisture will begin to return Wednesday with warmer lows and higher
highs. Early indications are that pattern will flip back to an above
normal temperature regime mid- to late-week as south to southwest
flow in the mid and upper levels occurs.
Mostly dry conditions are expected through at least Wednesday of next
week with the dry air in place. A stronger trough is being
advertised in both the GFS and ECMWF for late next week across the
four corners region that then ejects into the southern plains. Have
introduced low rain chances at this point (20%) given the potential
mid-level support and moisture in place but much of the stronger
activity (at this point) looks to remain north of the region.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 61 71 50 75 49 / 30 20 0 0 0
Austin Bergstrom Intl Airport 64 73 48 73 47 / 20 20 0 0 0
New Braunfels Muni Airport 64 73 49 75 46 / 20 20 0 0 0
Burnet Muni Airport 56 68 46 72 46 / 30 10 0 0 0
Del Rio Intl Airport 63 77 52 78 54 / - 10 0 0 0
Georgetown Muni Airport 59 69 48 72 47 / 30 10 0 0 0
Hondo Muni Airport 65 77 50 78 48 / 10 20 0 0 0
San Marcos Muni Airport 64 73 49 75 46 / 20 20 0 0 0
La Grange - Fayette Regional 65 74 50 72 48 / 30 20 0 0 0
San Antonio Intl Airport 65 74 52 75 49 / 10 20 0 0 0
Stinson Muni Airport 67 75 52 75 49 / 10 20 0 0 0
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale/Aviation...24
Synoptic/Grids...17
Public Service/Data Collection...30
Area Forecast Discussion
National Weather Service Goodland KS
1000 PM MDT Fri Apr 21 2017
.SHORT TERM...(This afternoon through Saturday)
Issued at 228 PM MDT Fri Apr 21 2017
Latest RAP analysis shows mid-upper low pressure over our CWA. WV
imagery supports two distinct mid to upper level circulations:
one over southeast Colorado and another near west central Kansas.
A deep moist plume extends across our CWA while there was some
clearing across southern Colorado that eventually filled back int
with CU field developing.
This afternoon-tonight: Precip shield (light-moderate) continues to
impact the majority of our CWA, though there has been drier more
stable air in the northeast keeping coverage limited there . There
is still an indication by short range guidance that this activity will
slowly decrease in coverage through the late afternoon and then
transition eastward. An instability axis has developing in southeast
Colorado where better thunderstorm coverage is occurring and in
region of our CWA closer to the upper low circulation in that region
we may see a set up for non supercell funnels to develop before
sunset. Will need to monitor, but threat looks better southwest of
our CWA. Current guidance has trended towards precip ending across
much of our CWA by late tonight with a little weak forcing on back
side of system in our far west possibly supporting a few light
showers lingering into the late night hours.
Regarding temps tonight: Models show low level moisture pooling in
our far west and this could support low stratus or even patch fog
development. While air mass will support temps below 36 over our
west, the combination of wet ground and lingering cloud cover create
poor radiational conditions and frost is not currently anticipated
despited cooler temps.
Saturday: Clearing should occur from the northwest, while I am
concerned cloud cover could linger across our west if stratus holds
on. Cold pool will be present, but with almost no CAPE if we do not
clear in the west and develop good low level lapse rates I am
skeptical we would see showers redevelop in the afternoon.
Particularly with subsidence aloft. Temperatures should warm to near
seasonal normals (60s) in our east where afternoon clearing is more
likely. I am less confident in highs in the west where clouds could
linger.
.LONG TERM...(Saturday night through Friday)
Issued at 212 PM MDT Fri Apr 21 2017
Dry weather starts out the long term period before the return of an
active pattern. Temperatures climb through Monday and decrease
thereafter.
Warming temperatures and dry conditions result from a ridge building
over the region Saturday night and Sunday. The combination of clear
skies, light winds, and temperatures bottoming out in the low/mid
30s leads to the potential for frost Saturday night into Sunday
morning. Winds do begin to strengthen in the morning which may
inhibit frost development, especially over the western portion of
the forecast area, but stay lighter further east.
Southerly winds peak in the afternoon as a lee trough develops along
the Rockies. Wind gusts of 30 to 40 mph are possible, making for a
windy day. Flow aloft turns zonal Sunday evening as the ridge
progresses east.
The next system travels across the northern Plains on Monday, with
most of its precipitation up in the Dakotas. However, there is a
chance some showers could develop as far south as locations north of
I-70 as the wave moves through and a cold front pushes south.
Another disturbance traverses the High Plains on Tuesday along with
a second blast of cooler air, dropping temperatures and generating
precipitation chances.
A stronger trough forms over the western CONUS on Wednesday and
pushes east onto the Plains through Friday, bringing the region a
better opportunity for precipitation. Rain showers and the
occasional chance for some thunder linger through the end of the
work week with this system. There are differences in the timing,
location, and strength of this feature, so will have to wait to
pinpoint details.
Temperatures climb from the low/mid 70s on Sunday to the 70s/low 80s
on Monday. Cooler air filters in and temperatures gradually decrease
into the upper 50s/low 60s by Thursday. With the exception of
Saturday night, lows are generally in the upper 30s and 40s.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1000 PM MDT Fri Apr 21 2017
For KGLD and KMCK, vfr conditions expected through the period.
Winds at both terminals variable in direction through the period
at speeds around 6kts or less. Scattered to broken clouds at taf
issuance expected to linger through sunrise then quickly
dissipate/decrease by mid to late morning with little if any
clouds for the afternoon through midnight hours.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...DR
LONG TERM...JBH
AVIATION...99
Area Forecast Discussion
National Weather Service Huntsville AL
932 PM CDT Fri Apr 21 2017
.NEAR TERM...(Tonight)
Issued at 932 PM CDT Fri Apr 21 2017
Radar had quieted down signficantly over north Alabama, but that has
changed over the last 30 minutes as storms associated with the
surface front have pushed eastward. One particular storm showed
strong rotation as it moved along the front and became more of a
right-mover; it has since outpaced the enhanced low-level shear
though it is moving into a generally more unstable environment. The
front now stretches from north of Greenville MS, to near Nashville.
Prefrontal conditions have air temperatures in the mid 60s (usually
rain cooled) to lower 70s, with dewpoints in the 60s.
Model guidance has generally never brought the front into the area
tonight, and short-term models continue this trend. Newer runs of the
HRRR take the ongoing activity to the northeast, then regenerate
storms towards daybreak. This is a wetter solution than other short-
range models, but not a bad option overall. There should still be a
sharp gradient in rain chances from north and northwest (highest) to
south and southeast (lowest) overnight. Some patchy fog can`t be
completely ruled out where it stays clear, though the coverage
remains questionable.
.SHORT TERM...(Saturday through Sunday night)
Issued at 245 PM CDT Fri Apr 21 2017
Chances for more showers and thunderstorms are in the forecast on
Saturday, given an unstable atmosphere with deep moisture and an
approaching cold front from the west. Model variances even this close
to this next event still have a variety of solutions, with the
GFS/ECMWF the wettest and NAM/ARW the drier runs. The latter two do
indicate the frontal boundary marching in a west to east manner
across the area during Saturday; indicative of a convective line. The
ECMWF was similar but wetter with its precipitation mass fields. The
GFS similar to the NAM yesterday was hinting at a low forming over
the region tomorrow evening. Additional bulk shear provided by this
low and more warmer air moving inland will help with convection
development and strength. As such, some of the storms could become
strong to severe in intensity during the day tomorrow - with the
primary threats from strong to damaging wind gusts.
The front should move across the region, reaching our eastern areas
late Saturday afternoon/early evening. The models led by the GFS
keeps post frontal showers going into Sunday morning. The showers
should taper off from west to east as the system exits stage right.
Along with an end of showers, more clouds than sun, and strong for
this time of year cold air advection will result in a rather chilly
day on Sunday. Highs will only rise into the lower 60s - compared to
low/mid 80s the past week and a half or so, and lows Sunday
night/Monday morning bottoming out around 50.
.LONG TERM...(Monday through Thursday)
Issued at 245 PM CDT Fri Apr 21 2017
By Monday, model guidance moves the upper low into southeastern
Georgia. This should push all precipitation east of the area.
However, some cloud cover and northerly flow will keep high
temperatures (normal highs ~75 degrees) just below normal values in
the 68 to 73 degree range and low temperatures (normal lows ~52
degrees) near normal around 50 degrees. Upper level ridging quickly
builds into the Tennessee Valley on Tuesday and strengthens into
Wednesday. This along with very warm temperatures in the boundary
layer are advected via southwest flow into the Tennessee Valley as a
result. This will allow highs on Tuesday and Wednesday to climb into
the low to mid 80s (possibly higher if some model guidance is right).
In northwestern Alabama and Southern Middle Tennessee, models do
increase lift and moisture ahead of a shortwave south of a main
longwave trough further north moving through the Great Lakes region.
Models pull this energy and deeper moisture northeast of the
Tennessee Valley during the day on Wednesday, but not before more
cloud cover/isolated convection possibly clips these areas. At this
point, given some models are slower moving the shortwave at the base
of the longwave trough axis eastward, leaving out chance of rain near
the MS/AL border and in Southern Middle Tennessee.
As a strong longwave trough axis associated with a potent upper low
develops over the Rockies on Thursday, the upper level ridging over
the southeast sharpens significantly. This should bring even warmer
temperatures into the area on Thursday as 925 mb temperatures warm
to between 21 and 25 degrees. Could see some upper 80s/lower 90s.
However, for now included upper 80s in the forecast on Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 629 PM CDT Fri Apr 21 2017
VFR conditions look good at both KHSV and KMSL overnight. The
forecast diverges before sunrise. KMSL has a good chance of lower
stratus developing due to their proximity to the next system, and
TAFs reflect a brief window of MVFR ceilings 11-13Z. Scattered storms
will also be in the vicinity at KMSL by early morning, before the
main line of storms arrives 18-20Z. KHSV will continue with VFR
conditions with less chance (though not zero) chance of low stratus
and less chance of storms until about 18-20Z. Winds at both sites
will be southerly overnight, then will become gusty out of the SW
after daybreak.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...BCC
SHORT TERM...RSB
LONG TERM...KTW
AVIATION...BCC
For more information please visit our website
at weather.gov/huntsville.
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1054 PM EDT Fri Apr 21 2017
.UPDATE...
Issued at 1054 PM EDT FRI APR 21 2017
Periods of showers will continue to affect the area through the
rest of the night as a short wave trough moves through eastern
Kentucky, and then additional moisture advection occurs along the
nose of an 850 mb jet that will be ramping up across the Tennessee
Valley closer towards dawn. The thunderstorm threat will be low
overnight, with waning instability, so will leave out this mention
by around midnight. Have had a few locally heavy rainers this
evening, but these have been isolated. The latest HRRR supports
generally lighter showers overnight, so have removed the locally
heavy rainfall mentioned in the HWO. The latest 00z NAM has
shifted the heavier QPF further southeast into Tennessee Saturday
through Sunday, so will await further 00z model guidance before
deciding to ramp up to any hydro headlines. Updates have been
sent.
UPDATE Issued at 630 PM EDT FRI APR 21 2017
Convection is currently aligned along the Cumberland Valley,
close to the surface boundary near the TN/KY border. Some of the
embedded thunderstorms are slow-moving, and will have to watch
for locally heavy rainfall in places. Further west, an area of
showers and storms are moving in from the southwest, associated
with a short wave trough in the mid-levels. The HRRR seems to
have a decent handle on this feature and its timing. As such, have
beefed up the POPs a bit into this evening from southwest to
northeast. A lot of the thunderstorms will likely remain confined
to along and south of Highway 80 and the Hal Rogers Parkway, where
better instability will remain. Updates have been sent.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 311 PM EDT FRI APR 21 2017
Slow moving frontal boundary lies across Southeast Kentucky,
through Tennessee to Northern Mississippi. Showers and a few
thunderstorms are showing a diminishing trend early this
afternoon as a short wave travels east. This drier trend should be
short lived as more ripples of short wave energy interact with
moisture along the boundary. Locations in the southern portion of
the area should see widespread showers and thunderstorms by this
evening. Locations farther to the north should experience
widespread precip by around midnight when the front will be
lifting northward in response to a potent wave of low pressure to
the southwest. Thunder chances are expected to be limited to the
early evening hours until instability wanes with loss of daytime
heating.
For Saturday, the front should be located near the TN/KY border.
1005 mb low pressure is expected to be tracking through TN.
Numerous to widespread showers and thunderstorms are forecast to
develop and persist through the day and into Saturday night. High
precipitable water lifting over the slow moving frontal surface
parallel to the mid level flow will result in a few rounds of
heavy rain, possibly leading to localized high water problems.
Elected to hold off on a flood watch due to model uncertainty with
respect to rainfall amounts and locations of heaviest amounts.
Rainfall should decrease in coverage and intensity over western
counties late Saturday night when the low is forecast to be over
East Tennessee, though far Eastern Kentucky could stay under
showers for the bulk of the period.
While all locations can expect below normal temperatures, highs
Saturday will vary with respect to the frontal position, with
upper 60s in the far south contrasting with upper 50s central and lower
50 far north.
.LONG TERM...(Sunday through Friday)
Issued at 305 PM EDT FRI APR 21 2017
An upper level low will drop southeast across the Tennessee Valley
and across the southeastern United States Sunday into Monday. This
will keep a lingering chance of showers across the area through much
of the day on Sunday before tapering off heading into Sunday night.
Highs on Sunday will generally be in the lower 60s. Weak high
pressure will then build into the area Monday into Tuesday leading
to dry conditions and a bit of a warming trend. Highs on Monday will
be in the upper 60s to around 70, increasing to the mid 70s for
Tuesday.
An upper level trough axis will weaken as it moves from the central
United States into the the Great Lakes region Wednesday through
Thursday. This will help a weakening cold front drop down toward the
area through mid week but there is quite a bit of model variation
with the timing and placement of the front. Will therefore just
allow for some lower chance pops to overspread the area Wednesday
afternoon into Wednesday night. Highs on Wednesday will warm into
the lower 80s across most of the area.
Mid and upper level ridging will then build into the area Thursday
into Friday. This will lead to dry conditions and unseasonably warm
temperatures with highs both days in the mid 80s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 813 PM EDT FRI APR 21 2017
Showers and a few thunderstorms will be advancing from the south
and west across the area this evening. Ceilings will gradually
lower down to MVFR, with temporary IFR conditions expected within
any thunderstorms. Ceilings will continue to lower down to IFR
through Saturday, as an area of low pressure tracks along a
stalled frontal boundary near the Tennessee/Kentucky border.
Periods of showers, along with a few thunderstorms generally
along and south of a line from KSME to KPBX will continue across
the area. Light and variable winds will become north to
northeast at 5 to 10 kts through the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GEOGERIAN
SHORT TERM...Coniglio
LONG TERM...Lott
AVIATION...GEOGERIAN
Area Forecast Discussion
National Weather Service Key West FL
1002 PM EDT Fri Apr 21 2017
.DISCUSSION...
A relatively large pocket of showers is slowly diminishing in the
western third of the Keys service area late this evening. More
isolated echoes stretch eastward across portions of the Florida
Straits, the Keys island chain, and nearshore Gulf and Bay waters.
Winds are moderate to occasionally fresh from the east/southeast.
Under mostly cloudy skies, temperatures in the Florida Keys are in
the middle 70s.
The late evening local sounding shows a veered wind profiles, with
an unseasonably wet moisture tally...very near 2 inches. We are
conditionally unstable, and scattered/chance of showers still
looks like a good forecast through the overnight period with a few
thunderstorms possible, despite the slow shrinkage of showers to
the west. This agrees with the most recent HRRR local solution.
A recently updated zone forecast had a minor change in the wind
direction from the afternoon issuance...setting the initial winds
more to the southeast. No other changes were included, of course
the same for the gridded weather elements.
&&
.MARINE...
The upcoming coastal waters update will have little if any changes
included. Was initially thinking of going with much higher
coverage of showers to our west, but the radar trend over the past
hour or so makes the scattered advertisement more agreeable. Small
craft should exercise caution if plans are to head into the
offshore Atlantic waters overnight and Saturday.
&&
.AVIATION...
Light rain will persist through Saturday morning with embedded
heavier showers. The heavier showers could result in visibilities
being briefly reduced to 3-5SM. Ceilings of 4000-6000 feet are
expected. Rain is expected to increase in intensity late
morning/early afternoon hours Saturday with isolated thunderstorms
developing. Will mention VCTS in the TAFS beginning 20Z Saturday.
Heavier showers could result in visibilities briefly reduced to
1- 3NM Saturday afternoon. Ceilings will gradually lower during
the day Saturday with MVFR ceilings likely in the afternoon.
Expect southeast winds 11-14 knots with gusts around 20 knots
through the period.
&&
.CLIMATE...
Keys Weather History, on April 20, 1987 the low temperature fell to
63 degrees. This set the daily record minimum temperature for the
date in Key West. Temperature records for Key West date back to
1872.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...04
Aviation/Nowcasts....MM
Data Collection......Fling
Visit us on the web at weather.gov/key
Follow us on Facebook and Twitter at:
www.facebook.com/nwskeywest
www.twitter.com/nwskeywest
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
636 PM CDT Fri Apr 21 2017
.SHORT TERM...(This evening through Saturday)
Issued at 329 PM CDT Fri Apr 21 2017
High pressure across the Northern Plains will build into Wrn and
Ncntl Neb tonight followed by Pacific high pressure Saturday. The
guidance came in with subfreezing lows tonight in the Platte valley
and elsewhere. These data sets were blended and bias corrected for
lows mostly in the mid 30s. The RAP model indicates drying aloft and
residual low level moisture but no fog. The HRRR and SREF models
also indicate no fog.
Generally clear skies are expected Saturday with high pressure
moving overhead. H850mb temperatures warm to near 10C by 00z which
supports highs in the 60s.
.LONG TERM...(Saturday night through Friday)
Issued at 329 PM CDT Fri Apr 21 2017
The models continue to show strong dry return flow Sunday. 500m AGL
winds increase to around 25kt in the afternoon which supports south
winds of 25 mph. A low level jet takes over Sunday night ahead of
Pacific cold front forecast to move through Monday morning.
A series of disturbances will move through the Cntl Plains Tuesday
through Friday. The models show significant timing and track
differences with the disturbances. The GFS and it`s ensemble are
paired off with a strong upper low lifting through the region
Thursday while the ECM and GEM show the same across KS followed by a
second strong disturbance Friday or beyond. This is a significant
difference which forces a broad brush to the forecast.
POPs have been limited to 30 to 50 percent which is about 10 percent
higher than yesterday. WPC suggests around an inch to 1 and 1/2
inches of rainfall Tuesday through Friday and the CPC continues to
outlook most of Nebraska for heavy rainfall Wednesday and Thursday.
The storm mode would be showers and generally isolated
thunderstorms. K indices in the GFS and ECM hover in the lower 30s
at times across Wrn Neb and a check on the ensemble severe weather
procedure indicates no organized severe weather opportunities...this
would likely occur near or in the warm sector which will be south of
Wrn and Ncntl Neb.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 633 PM CDT Fri Apr 21 2017
Isolated showers over the Nebraska Panhandle this evening. VFR
over Western Nebraska with mid and high clouds and easterly winds
around 10kts. Winds will diminish this evening with some clearing
Saturday morning.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Power
Area Forecast Discussion
National Weather Service Louisville KY
714 PM EDT Fri Apr 21 2017
...Updated Aviation Discussion...
.Forecast Update...
Issued at 525 PM EDT Fri Apr 21 2017
Two separate areas of precip nearing central KY/south central IN
this hour. One, more stable in nature is along our western border
with PAH`s forecast area. An occasional lightning strike has been
noted in this region over southern KY. The second, more active area,
is across middle TN, and slowly lifting northward. Despite some good
heating over central KY this afternoon, RAP model forecast soundings
show this has not been enough to overcome an inversion around 800
mb, and consequently not even seeing much in the way of cumulus
development. So any rain chances look to come as these two waves of
precip move into our region. The more stable one looks like it will
get here faster, though our Lake Cumberland area still may see a few
stronger storms...there is an area of new development just over
southern Pickett county in TN.
Have trended the forecast toward the models that are handling the
present situation the best. A third system out over southern
MO/northern AR looks to move in with another wave of rain late
tonight. Rainfall totals by daybreak could get up to an inch across
portions of southern KY.
&&
.Short Term...(This evening through Saturday night)
Issued at 300 PM EDT Fri Apr 21 2017
Early this afternoon, a cold front was draped from SW TN into far
southeastern Kentucky. North of the front, precipitation had
diminished and clouds have started to scour out. In the near term,
it appears that several hours of mainly dry weather are expected
along with some clearing skies. This will result in temperatures
rising with some late day highs in the upper 60s to the lower 70s.
For this evening and overnight, the lull in convection is not
expected to hold across the region. With the afternoon sun, we
should see some pockets of instability developing. Convection has
already begun to develop along the I-40 corridor in TN in the weakly
capped airmass down that way. Decent bulk shear values (>30kts)
have been helping convection become strong at times. The latest
short term mesoscale models lift this line of convection northward
into southern KY later this evening (23-01Z) and then into central
KY toward midnight. We may see a secondary lull in convection until
the upper wave arrives overnight brining the main slug of convection
to the region. Given the good agreement in the models, have gone
ahead and bumped up PoPs for the tonight period. Lows tonight will
range from the mid-upper 40s across southern IN and northern KY to
the lower 50s in southern KY.
For Saturday, cloudy skies with periods of showers and a few
thunderstorms are expected. The best chance of storms would be most
concentrated across our southern counties. A strengthening pressure
gradient will result in breezy/brisk conditions throughout the day.
Sustained winds of 15-20 MPH with gusts up to 30 MPH will be
possible at times. It will be rather raw with highs only warming
into the lower 50s across southern IN and northern KY. Some warmer
temperatures with lower-mid 60s are possible down across southern KY.
For Saturday night, bulk of heavier rainfall will shift into eastern
Kentucky. For much of southern IN and north-central KY, low
cloudiness along with some light rain showers are expected to
continue into the overnight hours. It will remain a breezy and a
rather raw evening with lows cool into the upper 40s with overnight
lows dropping into the lower-mid 40s in most spots. The only
exception will be Lake Cumberland region where upper 40s to around
50 will be possible.
In terms of rainfall, a general 1 to 2.5 inches of rainfall is
expected through the short term period. Antecedent conditions are
relatively dry across much of west-central KY. Current rivers are
not running high. Some FFG values are lower across our Bluegrass
region. However, 24hr FFG values are slightly over 3 inches in many
places. So while heavy rainfall will be possible during the period,
it appears that the threat of widespread hydrologic issues remains
low, but we`ll continue to monitor things closely.
.Long Term...(Sunday through Friday)
Issued at 305 PM EDT Fri Apr 21 2017
Upper level low will slowly move across the region on Sunday. This
will result in mostly cloudy conditions with some scattered light
showers around. Skies will likely take time to clear out Sunday
evening. Highs will warm into the lower 60s where we clear out
first (our NW areas). In areas that stay socked in, highs will
likely top out in the mid-upper 50s. Lows Sunday night will cool
into the mid-upper 40s.
Ridging will build into the region for Monday and Tuesday resulting
in dry conditions. Daytime highs will warm into the 70s with
overnight lows in the 50s.
The models are in agreement that the next front will come into the
region on Wednesday bring showers and a few thunderstorms. As we`ve
seen in previous systems of late, it appears that the front will sag
southward and stall out across TN late Wednesday into Thursday
before lifting back as a warm front on Thursday. Model differences
crop up by Friday as the models are trying to resolve when the next
weather system comes in from the west. That system could be a
decent severe weather maker to our west next week and could bring
unsettled weather to our area by next weekend.
Highs on Wed/Thu will be in the upper 70s to the lower 80s, with
highs solidly in the lower 80s by Friday. Overnight lows will
generally cool into the upper 50s to the lower 60s.
&&
.Aviation...(0Z TAF Issuance)
Issued at 712 PM EDT Fri Apr 21 2017
A few rounds of showers and storms are expected to affect the TAF
sites tonight and tomorrow. These will bring lowering ceilings and
visibility reductions at times.
The first round of rain is moving through SDF and BWG right now and
will be to LEX by 02Z or so. Any lightning that was in the vicinity
of BWG earlier has fizzled, so these are expected to just be rain.
This round will push off to the east by 06-08Z or so with a break
for a few hours. However, ceilings are expected to lower at this
time to high end MVFR.
Ceilings will continue to lower to below fuel alternate as another
round of rain moves in during the early morning/predawn hours. Winds
will pick up out of the northeast. The best chance for any storms
tomorrow morning will be at BWG, so have added in a PROB30 group
there.
There then looks to be another lull in the rain from mid morning
through mid day with showers then moving back in. As this round
moves out during the afternoon there then could be some improvement
in cigs at SDF after 20-21Z or so. Winds through the day Saturday
will be 10-15 knots with gusts up to 20 knots at times out of the
northeast.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...RJS
Short Term...MJ
Long Term....MJ
Aviation...EER
Area Forecast Discussion
National Weather Service Marquette MI
738 PM EDT Fri Apr 21 2017
.SHORT TERM...(This evening through Saturday)
Issued at 353 PM EDT FRI APR 21 2017
WV imagery and RAP analysis indicated a split flow pattern with a
ridge over the nrn plains and a trough into Quebec resulting in
confluent nrly mid/upper level flow through the nrn Great Lakes. At
the surface, brisk nrly winds were diminishing into Upper Michigan
as high pressure over the eastern Dakotas builds toward the area.
Tonight, the high will move overhead tonight with clear
skies/light winds. With PWAT values aob 0.25 inch very favorable
radiational cooling conditions will allow temps to drop toward the
lower end of guidance, into the lower 20s over interior west.
Expect higher readings tonight in the mid 30s near the relatively
warmer Great Lakes.
Saturday, sunshine and mixing through 850 mb temps in the 3C to 5C
range will push inland max temps into the lower to mid 60s. Winds
will be light enough to allow lake breeze development over the
central and east.
.LONG TERM...(Saturday night through Friday)
Issued at 325 PM EDT FRI APR 21 2017
Although there may not to be any hi impact wx events during the
upcoming week, the fcst pattern is fcst to be changeable/active,
with a sw flow alf bwtn an upr trof over the Plains/upr rdg over the
se CONUS in the srn branch dominating next week. A cold fnt wl pass
the Upr Lks on Sat ngt accompanied by some patchy lgt pcpn on the
srn flank of a disturbance passing thru Ontario within the nrn
branch flow. There wl be some drying in the wake of this fnt on Sun
that wl persist for the most part thru Mon, but a shrtwv/sfc lo pres
aprchg fm the sw wl then bring a return of more showers on Mon
ngt/Tue, especially over the w. Depending on whether the cold fnt
attendant to this lo pres stalls nearby on Tue ngt into Wed, there
could be another round of showers mainly over the se cwa later on
Tue into Wed. After a period of drying associated with hi pres bldg
over Hudson Bay, another shrtwv aprchg fm the sw wl likely bring
more ra back to the area by next Fri. Most of the medium range time
wl feature aob normal temps, except perhaps on Tue and next Fri.
Sat ngt...Lingering dry air associated with sfc hi pres retreating
slowly to the se wl bring dry wx early in the evng, but then a cold
fnt associated with a disturbance in the nrn branch tracking thru
Ontario wl pass during the early mrng hrs on Sun. The bulk of the
models show a narrow band of lgt pcpn under axis of fgen on the cold
side of the fnt arriving over the far nw cwa toward midngt and
influencing mainly the nrn tier with an upslope nly flow in the wake
of the fropa. Any pcpn, which wl start as ra but could mix with sn
as colder air follows, wl be on the light side with an absence of
sgnft mstr inflow and passage of sharper dynamic forcing to the n
closer to the shrtwv track.
Sun...Hi pres bldg into nw Ontario under larger scale subsidence
following the exiting shrtwv is fcst to extend a sfc rdg axis into
the Upr Lks. Although the arrival of this rdg axis/some drier llvl
air and acyc flow wl tend to diminish any pcpn lingering in the mrng
over mainly the nrn tier, a good deal of mid lvl mstr/cld cover wl
linger near an h85-7 fntl bndry that remains near the area to the n
of the relatively shallow cooling left in the wake of the sfc fnt
that wl stall in WI. The best chc for more aftn clrg wl be over the
ne cwa, which wl be more influenced by deeper drying/subsidence. H85
temps falling as lo as -5 to -6C over the Keweenaw and llvl nly flow
off Lk Sup wl cause much cooler wx for the cwa, with hi temps
holding in the 30s near Lk Sup.
Sun ngt into Wed...A shrtwv in the srn stream flow that wl be moving
thru the central Rockies on Sun ngt wl dvlp a sfc lo pres in the
central Plains. This shrtwv/sfc lo pres are then fcst to lift enewd
toward the far nw Great Lks and across wrn Lk Sup on Tue mrng toward
James Bay by Wed mrng. Some mixed pcpn may return to the nw cwa as
early as Sun ngt as the flow alf veering to the sw results in incrsg
isentropic ascent within the mid lvl fntl bdnry best shown on the
290K sfc. Most of the medium range guidance shows some rather
vigorous mid lvl dry slotting following the shift of the mid lvl
fntl bdnry to the n of the cwa on Mon before the sharper dpva/upr
dvgc ahead of the shrtwv aprchg fm the wsw arrives with some deeper
mstr/hier pops for showers on Mon ngt over the w. The sfc lo pres is
fcst to lift to the ne acrs wrn Lk Sup on Tue, with only sct showers
along its attendant cold fnt then spreading to the e during the day
into the evng. Many of the medium range models indicate the fnt may
stall just to the e on Tue ngt under a more sw flow alf on the nw
flank of an upr rdg over the se CONUS. Another shrtwv/sfc lo pres
riding ne along this bndry could bring more showers for at least the
se cwa on Tue ngt into Wed. The best chc for above normal temps
during this stretch wl be on Tue when the sfc lo pres wl be passing
to the nw of Upr MI.
Wed thru Fri...There wl be a period of drying on Wed into at least
Thu under the subsidence in the wake of the shrtwv riding to the ne
along the fnt to the e. Although a sfc rdg axis on the srn flank of
hi pres bldg over Hudson Bay is fcst to prevail over the Upr Lks,
there could be quite a bit of lo cld lingering in the rather shallow
nly flow of cool air. Another shrtwv riding to the ne in the sw flow
alf btwn an upr trof in the Plains/upr rdg over the se CONUS wl
bring a return of some hier pops and perhaps a TS/heavy rain Thu
ngt/Fri. Temps should run blo normal on Wed into Thu, but then may
rebound aoa normal on Fri depending on the track of the sfc lo pres
that could pass over or just to the w of Upr MI.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 737 PM EDT FRI APR 21 2017
Dry high pres will dominate thru Sat aftn, ensuring VFR conditions
prevail at KIWD/KCMX/KSAW thru this fcst period.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 325 PM EDT FRI APR 21 2017
Lingering stronger nnw winds up to 20-25 kts over the e portion of
the Lake will diminish this evening with the arrival of a surface hi
pres. Expect a wind shift to the wsw on Sat as the hi center sinks
to the se. As the pres gradient tightens ahead of an approaching
cold front, wind speeds up to 20-25 kts will be possible in the
afternoon/evening in the area between the Keweenaw and Isle Royale,
where the topography funnels this flow. In the wake of the frontal
passage, n winds up to 20-25 kts will occur late Sat night into Sun
before the gradient slackens on Sun as hi pres building into Ontario
extends a ridge into the Upper Lakes. E veering s winds will then
increase up to 25 to 30 kts on Mon into Tue as a lo pres moves from
the ncentral Plains across the Upper Lakes. Where the winds are
stronger over portions of the ncentral and e parts of the Lake, not
out of the question there could be a gale at least a part of this
time depending on the strength of the lo pres. Expect a wind shift
to the n up to 25-30 kts on Wed following the exiting lo pres/
attendant cold frontal passage.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...KC
AVIATION...Rolfson
MARINE...KC
Area Forecast Discussion
National Weather Service Morristown TN
1009 PM EDT Fri Apr 21 2017
.DISCUSSION...
Tweaked overnight temperature/dewpoint trends a bit based on
current obs. Otherwise, only major chance with this update was
bringing PoPs and cloud cover a bit further south for Saturday and
upping QPFs to match WPC guidance. Still some major differences
in short term models with regards to precip timing tomorrow, and
confidence is below normal. The latest NAM wants to keep areas
south of I40 dry Saturday morning (with some lighter showers
north), and just slowly nudges the precip into the Cumberland
Plateau by early evening. From there, precip slowly works into a
TRI-TYS-CHA line by 00-03Z. In contrast, latest HRRR run (which
currently goes through 18Z Saturday) is much faster bringing the
line in, having it across much of the TN valley by 16Z.
To further complicate matters, there is not much model
consistency from run to run either. Regardless, looks like a
decent potential for some severe storms tomorrow as the cold front
pushes through with decent instability, shear, and plenty of
moisture.
We will continue to monitor the heavy rainfall potential across
the area this weekend. Current WPC forecasts indicate rainfall
totals maxing out around 3-4" across SW Virginia and NE
Tennessee.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 62 81 59 67 / 50 50 80 60
Knoxville McGhee Tyson Airport, TN 61 77 56 65 / 80 70 80 70
Oak Ridge, TN 61 76 55 63 / 80 70 80 70
Tri Cities Airport, TN 57 73 53 63 / 80 80 80 80
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...None.
VA...None.
&&
$$
EMH
Area Forecast Discussion
National Weather Service Paducah KY
944 PM CDT Fri Apr 21 2017
.UPDATE...
Issued at 943 PM CDT Fri Apr 21 2017
As of 02z, the 1 hour deterministic GFS and the 12z Canadian
(CMCnh), and to a letter degree the ESRL HRRR and 4km NAM-WRF
(ARW version, seem to be getting a better handle on the timing and
intensity of the convective activity for the remainder of the
first period (tonight).
A Mesoscale Vorticity Circulation (MVC) that moved across
Southern Missouri earlier this afternoon enhanced lift across the
WSW-ENE 850 mb frontal boundary stretching from north of Poplar
Bluff to near Owensboro, producing moderate rain and sharpening
the surface pressure gradient across the northeast part of the WFO
PAH forecast area.
The 850mb flow gradually increases for the rest of this evening
over Arkansas into Southern Missouri, gradually working northeast
after midnight. Sharper lift will be realized over Southeast
Missouri with a gradient of thunderstorm development along and
east of the inverted trough (currently along the western border of
Arkansas).
Anticipate that Southeast Missouri should see the greatest
increase in QPF (rainfall amounts) from 1 am to 5 am CDT. Given
the antecedent (past) rainfall, the potential for flooding should
spike during this time period. This area still looks to have the
best chance for flooding overnight.
Modified the coverage of the thunderstorm activity to coincide
with transit of the surface low/inverted trough overnight.
Am somewhat concerned that the zone of higher QPF may shift
southward into West Kentucky around daybreak. However, given the
eastward speed of the system expected to increase slightly, there
will be a delicate balance between residence time of higher
rainfall amounts at any one location in West Kentucky. Allowing
for the lack of significant antecedent rainfall over southern
sections of West Kentucky the past two days, am doubtful that any
extension of a flood watch into Kentucky will be needed.
UPDATE Issued at 750 PM CDT Fri Apr 21 2017
Updated aviation discussion.
.SHORT TERM...(Tonight through Saturday night)
Issued at 240 PM CDT Fri Apr 21 2017
Main concern through Saturday is heavy rainfall potential.
A moist southwest flow aloft has been overrunning the cool low
levels, resulting in persistent moderate rains across parts of the
area. The heaviest rainfall has been in southeast Missouri, where
1 to 3 inches have fallen.
A Flood Watch has been issued for most of se Missouri and srn
Illinois through Saturday. Antecedent rainfall and higher soil
moisture has made those areas more favorable for quick runoff. In
addition, the 850 mb warm front is forecast to remain quasi-
stationary across those areas through Saturday morning. As a well-
developed 500 mb shortwave moves east toward our region, forcing
for ascent will increase along the 850 front tonight into early
Saturday. The models indicate the low-level southerly flow aloft
will increase to 30-40 knots south of the 850 mb front tonight.
All of this looks like a good setup for heavy rainfall, especially
with increasing elevated instability later tonight.
WPC and model qpf is in fair agreement that the axis of heaviest
rain will be near the 850 mb warm front. The actual values are not
especially high, generally 1.5 to 3 inches in the watch area, but
all guidance underforecast amounts that fell last night. In
addition, there is a chance thunderstorms will increase overnight
as the low-level jet strengthens and the mid levels cool with the
approach of the 500 mb shortwave. This could result in isolated
higher amounts than indicated by the models or WPC guidance.
Rainfall intensity will diminish quickly Saturday afternoon once
the 850 mb low passes across the Lower Ohio Valley. However,
numerous areas of light rain will occur in the moist deep cyclonic
flow into Saturday evening. The system is forecast to slow down
over the Tennessee Valley Saturday night. Nuisance-type areas of
light rain/drizzle will persist much of the night. Temps will show
very little change through Saturday night, generally stuck in the
upper 40s to mid 50s.
.LONG TERM...(Sunday through Friday)
Issued at 240 PM CDT Fri Apr 21 2017
Sunday looks to be the the beginning of improving weather
conditions, especially over the northwest half of the region as high
pressure presses slowly southeast from the Midwest toward the Ohio
Valley. Will need to leave some small lingering POPS in the morning
over the southern Pennyrile of wrn KY, and pesky wrap around clouds
may hang on most of the day along and south of the OH River.
However, most of se MO and srn IL should have a much prettier day
with highs in the mid 60s.
High pressure will take over for the first part of next week. In
addition to the return to ample sunshine, a warming trend will get
underway, especially Tuesday as the sfc high moves off to the east
and winds turn southerly. Afternoon temperatures by Tuesday
afternoon should end up very close to 80 at most locations.
Next weather maker will come with the approach of a cold front from
the northwest on Wednesday. There looks to be ample instability by
that time to support thunderstorms, so will keep that mention in the
forecast. There is some indication the front may stall very close to
the region Wednesday night, then retreat back north as a warm front
Thursday. This will all depend on how quickly upper ridging off the
Southeast Coast builds during the period. If the upper ridge builds
as quickly as the GFS indicates, we would be quickly back into a
warm sector regime with warm temps and little chance of precip. The
12Z ECMWF is not so quick to build the ridge, and actually pushes
another H50 short wave toward the mid MS River Valley. The jury is
still out on this one, at least for now.
&&
.SHORT TERM...(Tonight through Saturday night)
Issued at 240 PM CDT Fri Apr 21 2017
Main concern through Saturday is heavy rainfall potential.
A moist southwest flow aloft has been overrunning the cool low
levels, resulting in persistent moderate rains across parts of the
area. The heaviest rainfall has been in southeast Missouri, where
1 to 3 inches have fallen.
A Flood Watch has been issued for most of se Missouri and srn
Illinois through Saturday. Antecedent rainfall and higher soil
moisture has made those areas more favorable for quick runoff. In
addition, the 850 mb warm front is forecast to remain quasi-
stationary across those areas through Saturday morning. As a well-
developed 500 mb shortwave moves east toward our region, forcing
for ascent will increase along the 850 front tonight into early
Saturday. The models indicate the low-level southerly flow aloft
will increase to 30-40 knots south of the 850 mb front tonight.
All of this looks like a good setup for heavy rainfall, especially
with increasing elevated instability later tonight.
WPC and model qpf is in fair agreement that the axis of heaviest
rain will be near the 850 mb warm front. The actual values are not
especially high, generally 1.5 to 3 inches in the watch area, but
all guidance underforecast amounts that fell last night. In
addition, there is a chance thunderstorms will increase overnight
as the low-level jet strengthens and the mid levels cool with the
approach of the 500 mb shortwave. This could result in isolated
higher amounts than indicated by the models or WPC guidance.
Rainfall intensity will diminish quickly Saturday afternoon once
the 850 mb low passes across the Lower Ohio Valley. However,
numerous areas of light rain will occur in the moist deep cyclonic
flow into Saturday evening. The system is forecast to slow down
over the Tennessee Valley Saturday night. Nuisance-type areas of
light rain/drizzle will persist much of the night. Temps will show
very little change through Saturday night, generally stuck in the
upper 40s to mid 50s.
.LONG TERM...(Sunday through Friday)
Issued at 240 PM CDT Fri Apr 21 2017
Sunday looks to be the the beginning of improving weather
conditions, especially over the northwest half of the region as high
pressure presses slowly southeast from the Midwest toward the Ohio
Valley. Will need to leave some small lingering POPS in the morning
over the southern Pennyrile of wrn KY, and pesky wrap around clouds
may hang on most of the day along and south of the OH River.
However, most of se MO and srn IL should have a much prettier day
with highs in the mid 60s.
High pressure will take over for the first part of next week. In
addition to the return to ample sunshine, a warming trend will get
underway, especially Tuesday as the sfc high moves off to the east
and winds turn southerly. Afternoon temperatures by Tuesday
afternoon should end up very close to 80 at most locations.
Next weather maker will come with the approach of a cold front from
the northwest on Wednesday. There looks to be ample instability by
that time to support thunderstorms, so will keep that mention in the
forecast. There is some indication the front may stall very close to
the region Wednesday night, then retreat back north as a warm front
Thursday. This will all depend on how quickly upper ridging off the
Southeast Coast builds during the period. If the upper ridge builds
as quickly as the GFS indicates, we would be quickly back into a
warm sector regime with warm temps and little chance of precip. The
12Z ECMWF is not so quick to build the ridge, and actually pushes
another H50 short wave toward the mid MS River Valley. The jury is
still out on this one, at least for now.
&&
.AVIATION...
Issued at 750 PM CDT Fri Apr 21 2017
A complex convective event will continue across the region
throughout most of the 00Z TAF period. An west-to-east warm front
around 4-5 kft off the ground will continue to bisect the region,
resulting in a wind shift from northerly to southwesterly with
increasing height. This boundary will also continue to be focus for
increased pcpn as mid level impulses move through. Overnight, an
inverted surface trough is progged to move into the area from AR,
increasing gustiness of the northeasterly surface winds in some
locations. In the west, cigs should be intermittently MVFR this
evening, but should drop again overnight, eventually to IFR levels.
In the west, cigs should become predominantly MVFR with time. Vsbys
may go briefly IFR in bursts of heavier rainfall. Pcpn is expected
to begin to let up toward the end of the TAF period.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Flood Watch through Saturday afternoon for ILZ081>094.
MO...Flood Watch through Saturday afternoon for MOZ076-086-087-100-
107>111.
IN...None.
KY...None.
&&
$$
UPDATE...Smith
SHORT TERM...MY
LONG TERM...GM
AVIATION...DB
Area Forecast Discussion
National Weather Service Raleigh NC
935 PM EDT Fri Apr 21 2017
.SYNOPSIS...
A pre-frontal surface trough will linger over western NC tonight.
Meanwhile, a cold front will approach from the north tonight, then
sag into NC Saturday. The front will stall over far southern NC late
Saturday into Sunday, as a slow-moving area of low pressure tracks
along the front through the weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 935 PM Friday...
Highest threat for scattered showers and isolated thunderstorms into
the overnight expected to occur across the Piedmont into the far
northern coastal plain. Air mass across the region fairly moist with
precip water values hovering around 1.25 inches. At the sfc a weak
sfc trough extended from the foothills of western NC newd into VA.
The main sfc cold front stretched from western PA southwest into
middle TN. Aloft a weak perturbation was traversing eastward,
entering the western sections of central NC. This feature aloft
interacting with available moisture and weak convergence along the
sfc trough will maintain a threat for scattered showers, primarily
prior to midnight across the western Piedmont, and into the
overnight across the northeast Piedmont and the far northern coastal
plain. Severe storm parameters barely register across our region
while the better shear and instability reside well to our west and
north.
Plan to maintain broken-overcast skies across the north half, and
variably cloudy skies across the south. Temperatures should be
fairly uniform in the 60-65 degree range.
&&
.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 355 PM Friday...
The focus for showers and thunderstorms is expected to remain over
the western and northern zones of the Piedmont, as far south as
Albemarle to Raleigh to Rocky Mount - mainly Saturday afternoon into
the evening. This is where the low level boundaries should aid in
focusing the convective development. A blend of the Hi-res models
along with the GFS/EC were used in trying to place the main synoptic
cold front that is forecast to dive into the northern Piedmont
Saturday afternoon. Convection and associated outflows tonight will
greatly aid in convective initiation Saturday. The latest Hi-Res HRRR
suggests this may occur by early afternoon in a SW-NE corridor from
west-central NC to just north of the Triangle area. The main push of
much cooler and damp NE flow should hold off until late afternoon
and evening, which will eventually stabilize the boundary layer and
spread a low deck of clouds with it. Therefore, the temperatures
should show a very large range from upper 50s NE into the mid 80s
south during the late afternoon. A few marginally severe storms may
occur especially along the leading temperature/cloud gradients.
Showers and a few thunderstorms (elevated north of the cold front)
are expected for much of the Piedmont, Sandhills, and Coastal Plain
Saturday night. Widespread activity is expected in the west into the
central portions of NC, with more scattered activity down east. The
cold front should backdoor much of central NC, except the far SE
zones by 12z/Sunday. This will eliminate much of the severe threat,
but elevated storms will likely produce locally 1 to 2 inches of
rain in the western and central Piedmont by 12z/Sunday.
Since it has been dry recently, flash flooding is not likely through
12z/Sunday unless 1.5+ inch/hour rates and/or 3+ inches
in 3 hours materialize.
Lows will cool into the 50s, except 60s south Saturday night with
POP nearly 100 all zones.
&&
.LONG TERM /SUNDAY THROUGH SATURDAY/...
As of 255 PM EDT Friday...
An amplifying upper level low digging SE from the Rockies into the
Lower Midwest this afternoon will track eastward through the TN
valley on Saturday, progress ESE/SE toward the Southeast coast on
Sun/Mon, then shift offshore the GA/SC coast on Tue. Shortwave
ridging /WSW flow aloft/ is expected in the wake of the upper wave
on Wed/Thu. Even though the upper wave has moved ashore and been
sampled by the RAOB network, confidence in forecast specifics
(precip amounts, severe weather potential, temperatures) remains
below average due to the potential interaction between the
aforementioned upper low and northern stream shortwave energy
progressing east across the Great Lakes into New England, with
additional uncertainty assoc/w the effects of upstream convection
(heavy precipitation /latent heat release/) progged over portions of
the Carolinas/Southeast late this weekend. Broadly speaking, expect
mostly cloudy skies, cooler temperatures, and increasing chances for
convection over the weekend, particularly Sunday/Sunday night. The
best potential for surface based convection will be on Sat, though
coverage is difficult to ascertain at this time. Elevated
convection is more likely on Sunday, though some potential for
surface based convection may exist in the far S/SE. Chances for
precipitation will diminish from west-east and skies will clear by
Tue/Tue evening as the upper level wave progresses offshore. Expect
dry conditions and a warming trend Wed-Sat as an upper level ridge
builds over the Southeast CONUS. The next best chance for
precipitation may not materialize until early next week. -Vincent
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
As of 840 PM Friday...
24 Hour TAF Period: Several rounds of isolated to scattered showers
and thunderstorms are expected over the next 24 hours across central
NC in advance of a cold front.
Convection this afternoon/evening has generally remain isolated to
widely scattered and is expected to generally remain so into the
overnight hours. However, KGSO/KINT stand to see the best chance of
seeing some showers and storms for the remainder of the evening into
early Saturday morning as another round of showers and storms is
expected to clip the NW Piedmont of central NC. Brief IFR/MVFR
conditions will be possible with any convection this evening along
with perhaps a wind gust or two to around 25 to 30 kts. Otherwise,
VFR conditions are generally expected tonight. However, there is a
small chance we could see some sub-VFR cigs at KGSO/KINT/KRDU around
daybreak Saturday.
A cold front will approach the region from the north-northeast on
Saturday, possibly move south-southwestward across KRWI and KRDU
near the end of the TAF period. Near and behind the front, expect we
will see some showers and storms, along with accompanying sub-VFR
conditions and possible strong wind gusts. Thus, have included a
prob30 group for all the northern TAF sites for the last 4 hours or
so of the TAF period. Behind the front, expect cigs will quickly
fall to low end MVFR or IFR, with winds out of the north to
northeast.
Outlook: The cold front should stall over the region through Sunday
night, though likely just to the south of the central NC TAF sites.
This will allow for several waves of low pressure to track along the
front and bring numerous showers and possibly some thunderstorms.
Periods of showers and storms with MVFR to IFR CIGS and IFR VSBYS
will occur Sat PM through Monday night, possibly lingering into
Tuesday.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Badgett
NEAR TERM...WSS
SHORT TERM...Badgett
LONG TERM...Vincent
AVIATION...BSD/Badgett
Area Forecast Discussion
National Weather Service Blacksburg VA
944 PM EDT Fri Apr 21 2017
.SYNOPSIS...
A cold front will travel southeast this evening into tonight. This
front will stall near the North Carolina and Virginia border
Saturday, with a secondary low moving across the area Sunday. This
will keep us in a wetter pattern through the weekend into
Monday.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 940 PM EDT Friday...
The latest forecast adjustment will reflect an approaching gap
in the precipitation progressing through parts of eastern
Tennessee. This break in the showers will enter the southwestern
sections of the region around midnight, and progress across the
area heading into the early morning hours of Saturday.
Additional showers will arrive about three to four hours behind
this gap, thus bringing a return of showers to at least the
western sections of the area later tonight.
Thunderstorms will be likely limited to the far western and far
eastern sections of the region based upon the latest upstream
lightning trends.
Have also made minor tweaks to the hourly temperatures, dew
points, and winds based upon the latest observations and
expected trends into the early morning hours.
As of 635 PM EDT Friday...
Adjustments to the forecast this evening will reflect primarily
changes to geographical location of the best chance of
additional showers and thunderstorms through the evening hours.
This readjustment is based upon trends on regional radars of the
shower and thunderstorm activity, and expected movement through
the next few hours. The best coverage is expected to be along
and near the crest of the Blue Ridge from roughly Floyd, VA and
parts southwest into the Northern Mountains and Foothills of
North Carolina. This is expected to transition to more of a west
to east oriented location of the best coverage generally along
and south of Route 460. Have also made minor tweaks to hourly
temperature, dew point, and winds based upon the latest
observations and expected trends the next few hours.
As of 312 PM EDT Friday...
A cold front will travel southeast across the region this afternoon
into tonight and stall on Saturday. Scattered showers and
thunderstorms will develop ahead and along the boundary in the warm
unstable air. The Storm Prediction Center on SWODY1 highlighted a
marginal risk for severe thunderstorms for most of the area. With
CAPES around 1k J/kg, freezing level around 9 kft and a modest mid-
level flow of 30-40 kts, some of the stronger thunderstorms could
produce damaging winds and hail. As seen on SPC Mesoscale analysis
the best instability was located in the piedmont. Shaped the pops
tonight towards a blend of the HRRR AND NAM. The forecast area will
see a decent coverage of showers tonight, with thunderstorm chances
subsiding with loss of heating. Added some patchy fog overnight into
Saturday morning. Low temperatures tonight will range from the upper
40s in the northwest mountains of Greenbrier county in southeast
West Virginia to the lower 60s in the Piedmont.
An upper level trof will dig into the southeast State and develop
into a slow moving closed low by Sunday. as it drives a surface low
east through South Carolina. A wedge of high pressure will surges
into the region east of the Appalachians. For Saturday morning into
Saturday afternoon, isentropic lift from the surface low over the
lower Mississippi valley will bring widespread showers to the region
with a few thunderstorms. Across southern portions of the forecast
area, there will be some instability pool ahead of the wedge to fuel
development of thunderstorms, and shear along the backdoor front
will be sufficient to help organize the convection. The Day 2
Convective Outlook has placed southern portions of the forecast
area in a marginal risk for severe weather with wind and hail,
the primary threat. High temperatures Saturday will vary from
the lower 50s in the north to the mid 70s along the southern
Blue Ridge. Temperatures on Saturday will be highly dependent on
the strength of the wedge and placement of convection.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 312 PM EDT Friday...
A series of shortwaves in the northern jet stream from Colorado to
Montana will deepen the upper trough over the central United States
eventually closing off an upper low over the Tennessee Valley on
Sunday. This low continues to track southeast, reaching the Georgia
coast by late Monday. At the surface high pressure will be wedged
down the Appalachians on Sunday as a low tracks southeast out of the
Tennessee Valley. Inflow off the Atlantic is strong on Sunday night
and Monday. Upper jet supports good lift too on Saturday night and
Sunday. Forecast precipitable water values are above normal but not
excessively high, but will be watching the 1.25 to 1.5 inch values
advecting into the area because this would increase the heavy rain
threat. Any chance of thunder would be with elevated instability and
lift above the wedge. Will be keeping maximum temperatures at or
just below coolest guidance for Sunday and Monday.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 312 PM EDT Friday...
A long wave upper trough will develop over the western and central
United States Tuesday through Thursday. This will steer the weakened
upper low up the East Coast. Wide spread in the long range guidance
solutions after Thursday but overall looks like 500MB pattern is
amplifying with troughing in the west and ridging in the east.
By Tuesday the low will be off the southeast coast which will bring
surface and low levels winds around to the northwest and therefore
erode the wedge. Models have a cold front stalling through the
central United States Wednesday through Friday, with the GFS on the
east side of the differing solutions. Given the building southeast
ridge at the end of next week WPC preference was closer the the 00Z
ECMWF This keeps the Mid Atlantic region dry Tuesday night through
Friday with above normal temperatures.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
As of 705 PM EDT Friday...
Most locations still are experiencing VFR conditions outside of
the isolated to scattered heavier showers and storms across the
region. As the night progresses, look for a trend towards MVFR
ceilings and then a mix of MVFR and IFR by tomorrow morning,
with these lower flight levels continuing through the day.
A cold front will stall across the area tonight, and a
disturbances will head eastward along it during the course of
tomorrow. Visibilities will be mainly VFR with pockets of MVFR
associated with the heavier showers and storms and some late
night and early morning patchy fog.
Winds will be light and variable overnight into Saturday
outside of the areas of stronger showers and storms. Anticipate
gusty conditions along with the variable directions.
Moderate confidence in ceilings, visibilities and winds during
the taf period.
Extended Aviation Discussion...
Weather pattern active this weekend into Monday with periods of
rain/showers, heavy at times. Should expect mostly sub-VFR
condition when raining, but some VFR possible, especially north
of a LWB-LYH line.
Rain lingers into Monday as does lower cigs, and finally seeing
some VFR returning Tuesday. Drier weather continues Wednesday
into Thursday.
&&
.HYDROLOGY...
As of 300 PM EDT FRIDAY...
After 4 to 5 days straight days this week with spotty rainfall
mainly light across the area, we are still looking at the
possibility of a more significant hydro event this weekend. Despite
the semi-wet week, antecedent conditions are fairly dry across the
eastern 2/3 of the CWA and generally about normal in the west.
Moderate drought is still depicted on the U.S. Drought Monitor
across much of the piedmont and Abnormally Dry over most of the Blue
Ridge and surrounding area with near normal conditions in the west.
This suggests that we can absorb more water than might be typical. 3-
hour flash flood guidance from the River Forecast Centers ranges
generally from about 1.5 inches in the west up to around 3 to 3.5
inches in the west, reflecting well the drier conditions east of the
mountains.
A slight risk for convective rainfall exceeding flash flood guidance
was issued by WPC earlier for Day 2 and Day 3 (through 12z Monday).
Pockets of minor advisory-type flooding cannot be ruled out in
convective storms which will be more likely today and Saturday and
further south in the CWA where instability may be much higher. Any
training convection over the same basins could produce pockets of
flash flooding. At this point the river forecast is a purely QPF
based. Model QPFs have shown some decent run-to-run consistency over
the last few cycles providing more confidence that this will fulfill
expectations. Current WPC QPF in the day 1-3 period (today through
early Monday) period is generally about 2 to 4 inches, with the bulk
of it falling Saturday and Sunday and current WFO grids are close to
these numbers. The prolonged nature of the rainfall (48 to 72 hours)
will lessen the risk of serious river flooding (and flash flooding)
as runoff will be more spread out and less efficient.
The two best St. Louis University CIPS analogs to this event are
April 9-12, 2003 and March 28-30, 2010 both of which featured upper
lows over the southeastern U.S. Both events resulted in minor to
moderate river flooding on the Dan River but not on the New, James,
upper Tennessee or upper Roanoke Rivers. Ensemble river forecasts
from the GEFS ensemble are also highlighting the Dan River as the
most likely to flood, suggesting up to a 30 percent chance for
moderate flooding but the NAEFS has been consistently showing lower
probabilities. The situation will be monitored closely on future
shifts for a possible Flood Watch.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...KK
NEAR TERM...DS/KK
SHORT TERM...AMS
LONG TERM...AMS
AVIATION...DS/KK/WP
HYDROLOGY...PC