Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/01/19

Area Forecast Discussion

National Weather Service Columbia SC

 920 PM EDT Sun Mar 31 2019

.SYNOPSIS...
Cooler than normal temperatures are expected this week with a
coastal low pressure system Tuesday. Warmer and drier conditions
will occur midweek. Another cold front will approach the region
later in the week with a chance of showers.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
The cold front has moved offshore and showers remain south of
the area. There is cold air advection behind the front, and
temperatures will continue to fall through the night, with lows
in the mid 30s to lower 40s. Dry air is overspreading the area,
and precipitable water values will also continue to decrease.
However, a southwest flow aloft will hold high level clouds
over the region. Winds should stay up through the night so
temperatures will remain above freezing and fog is not expected.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/...
The next system that will be affecting the region for Monday
night into Tuesday continues to indicate rainfall, especially
across the eastern portion of the CWA. Model trends have been
very consistent over the past few days with the NAM being the
most aggressive and closest to the coast as the system develops
over the northeast Gulf of Mexico. The ECMWF is in the middle
and the GFS continues to keep the bulk of the moisture and
system offshore. Given the consistencies between the models
have continued with the compromise ECMWF. Monday looks to be an
unseasonably chilly day with some high clouds across the region
with temperatures in the middle 50s north to lower 60s south.
The clouds will thicken as the moisture deepens Monday night
into early Tuesday as the system becomes better organized along
the southeast coast. Isentropic lift will increase across the
area late Monday night into early Tuesday. This will likely be
the best window for rainfall across the Midlands and CSRA.
Expect the heaviest amount of rain to be across the southern
CSRA and eastern Midlands along and east of the I-95 corridor.
Have increased pops in that region for the period as pops will
range from the high chance across the Piedmont to categorical
along the I-95 corridor. Rainfall amounts will also be less west
to greatest east. There looks to be a tight precipitation
gradient and areas to the west may see less than one quarter
inch to near an inch closer to the coast. Temperatures will be
chilly on Tuesday with rainfall and chilly northeast to north
low level winds. Highs will only be in the 50s across the
Midlands and CSRA.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Expect deeper moisture to push out of the area Tuesday night
with high pressure and warmer/dry conditions returning for
Wednesday and Thursday. Another front with deep moisture flux
ahead of it from the Gulf coast region into the Southeast States
by Friday will result in another chance showers but near or
above normal temperatures. This system will push across the area
by Friday night and weak high pressure will build in for the
weekend. Expect temperatures to remain at/above normal for much
of the period.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
Expect VFR conditions through the 24-hour TAF period. The dry
air mass behind the cold front will dominate during the period.
Satellite trends support continued upper cloudiness. The GFS
and NAM Bufkit momentum transfer tool plus HRRR suggests a
surge in the cold air advection overnight with gusty winds. The
GFS and NAM Bufkit momentum transfer tools indicates continued
gusty winds during much of the day Monday. Expect gusts around
16 knots.

EXTENDED AVIATION OUTLOOK...Restrictions possible Monday night
through Tuesday as a low pressure system moves through the
region.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.

&&

$$



AREA FORECAST DISCUSSION...UPDATED

National Weather Service Jackson KY

 1054 PM EDT Sun Mar 31 2019

.UPDATE...
Issued at 1054 PM EDT SUN MAR 31 2019

Based on recent trends in observations and some guidance and a
look at Model Certainty, confidence in ridgetops and more open
terrain locations falling a degree or two lower tonight has
increased. Slight adjustments down for min T in those locations
have been made. The record low at JKL of 24 from 1987 could be
approached. The record low at LOZ of 22 from 1994 appear much less
likely to approached.


UPDATE Issued at 800 PM EDT SUN MAR 31 2019

High pressure continues to build into the region with cumulus and
stratocumulus continuing to mix out. Dewpoints are currently in
the teens to lower 20s across the region. The pressure gradient
will continue to slacken as the night progresses. Low temperatures
as low as the upper teens in the coldest locations still look on
target for the most part with some ridge/valley differences due
to expected earlier decoupling in the valleys. Some recent
guidance does suggest that temperatures on ridgetops and more
open terrain locations could fall a bit more than the current
forecast and this potential will continue to be monitored. At this
time, only minor adjustments were made to hourly temperatures
based on recent trends in observations.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 450 PM EDT SUN MAR 31 2019

20z sfc analysis shows high pressure building effectively into
eastern Kentucky. This has ended the last of the light showers in
the far east and also dissipated most of the post frontal clouds -
though some cu has developed in the colder air for western parts
of the CWA. The winds are still blowing pretty good from the
northwest at 10 to 15 mph with higher gusts - adding to the chill.
Temperatures only managed to climb back to the upper 30s
northwest and mid 40s south. Dewpoints, meanwhile, continue to
fall as drier air is advected into the area with upper teens seen
northwest and lower 20s southeast.

The models are in decent agreement aloft through the short term
portion of the forecast. They all depict the southern node of the
deep North American trough pulling northeast out of the area into
Monday morning. Heights will start to rebound into the day ahead
of a southern stream trough moving through the Southern Plains
that evening. The NAM is weaker with this wave than the GFS and
ECMWF, but still pretty close. The energy with this will spread
into Kentucky Monday night favoring its southern extent - but
with still some significance closer to Kentucky. Given the general
agreement and low spread through the period will favor a model
blend with a lean toward the HRRR for near term details and NAM12
thereafter.

Sensible weather will feature a very cold start to April as clear
skies and lightening winds set up a good night for radiational
cooling. With this, already cool temperatures will fall quickly
this evening as a hard freeze ensues for the entire area
overnight. Locations where the growing season has begun are
under a freeze warning from late this evening into Monday
morning. Widespread frost can also be expected, though the ridges
may be too dry for much to develop. The deeper valleys will also
be colder than the thermal belts and ridges tonight. Sunny skies
Monday morning will help temperatures to rebound with just some
high clouds possible moving in from the west late in the day.
These clouds will likely thicken and lower Monday night and a
stray shower cannot be ruled out depending on how a passing
southern stream wave develops. For now, have kept it dry but with
some single digit PoPs into early Tuesday morning in the far
southeast.

Again the CONSShort and ShortBlend guidance where used as the
starting point for the grids with some significant adjustments to
low temperatures tonight and to a lesser extent Monday night to
account for generally favorable radiational cooling conditions
leading to small to moderate ridge to valley temperature splits
both nights. As for PoPs, the only adjustments were to keep them
sub 15 percent Monday night into Tuesday morning due to
uncertainty with the northern extent of the southern wave at the
end of the period.

.LONG TERM...(Tuesday through Sunday)
Issued at 330 PM EDT SUN MAR 31 2019

The extended will start off slightly cooler than normal, with highs
in the upper 50s expected for Tuesday. After that, we can expect
several days of above normal temperatures across the area. A ridge
of high pressure will become firmly entrenched across the region
through Thursday afternoon. Daily highs from Wednesday onward will
vary from the upper 60s to the low to mid 70s. Nightly lows will be
in the 40s and 50s most of the period. The exception to this will
Tuesday morning, when we are expecting to see lows ranging from the
upper 20s to mid 30s. Some valley locations may experience frost
early Tuesday morning. We may also frost across the area Tuesday
night into early Wednesday morning, as temperatures fall into the
upper 30s across the area. The latest model data is suggesting that
the next chance for rain across the area will be from late Thursday
through Friday night. The model blend seemed a bit too fast with the
precipitation onset on Thursday, so the precip probabilities that
day were modified accordingly base on the more reasonable timing
seen in the ECMWF and GFS models. A few thunderstorms will be
possible Thursday night and Friday, as a trough of low pressure
moves across the Ohio Valley. Once this precip exits the area Friday
night, we should see dry weather going into the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 808 PM EDT SUN MAR 31 2019

High pressure continues to build into the region with the pressure
gradient gradually slackening. Winds at the TAF sites will
initially be in the 5 to 10KT range, but should become closer to
5KT by 6Z as the center of the high nears the area. With the high
building in and drier air working in as well, cumulus and
stratocumulus have dissipated giving way to VFR. High pressure
will dominate through the end of the period with VFR persisting.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Freeze Warning until 10 AM EDT Monday for KYZ058>060-068-069-079-
080-083>088-104-106>120.

&&

$$

UPDATE...JP
SHORT TERM...GREIF
LONG TERM...AR
AVIATION...JP



Area Forecast Discussion

National Weather Service Lubbock TX

 846 PM CDT Sun Mar 31 2019

.UPDATE...
Minor update to boost PoPs into the 15-25% range over much of the
Caprock after midnight tonight. Water vapor imagery shows the
upper low that was anchored near the Four Corners most of today
was now accelerating southeastward as expected. The low will
weaken/open as is emerges over the southern High Plains late
tonight. Ahead of the low, increasing lift has been producing
precipitation aloft from central New Mexico into the western Texas
Panhandle and northwestern South Plains much of this evening.
Light rain and light snow were being reported from Dalhart and
Clayton westward into north-central New Mexico. However, a
relatively deep dry sub-cloud layer has kept the moisture from
reaching the ground in our CWA to this point. Eventually, the
persistent moistening from aloft should be sufficient for a few
areas of sprinkles/flurries to surface, and recent runs of the
HRRR and RAP even suggest one or two narrow swaths of light snow
could grace the southwest Texas Panhandle and/or the western to
central South Plains after midnight. Any snow should be spotty and
light, but a few locations could see a quick dusting of snow
accumulate in grassy locations in the pre-dawn hours of Monday.
Given this, we have decided to increase PoPs to add a low mention
of light snow over much of the Caprock in the 06-12Z time-frame.
Given the marginal temperatures and light snow totals (if any),
impacts should be minimal. Aside from the adjustments to the
PoP/Wx/Snow grids, no other changes were made to the ongoing
forecast.

&&

.PREV DISCUSSION... /issued 626 PM CDT Sun Mar 31 2019/

AVIATION...
VFR conditions will prevail through the next 24 hours.

PREV DISCUSSION... /issued 300 PM CDT Sun Mar 31 2019/

DISCUSSION...
A nearly stationary and compact upper low centered almost
directly atop the Four Corners was finally getting a kick
southeastward this afternoon courtesy a 200 mb jet streak
spreading across the Great Basin. Streaks of mostly opaque
cirrus with virga already over our region should continue to
expand tonight ahead of this wave as large scale ascent
improves in response to favorable upper divergence ahead of
the low. Although some cumulus are noted on satellite and area
skycams across our far NW counties, moisture deficits are pretty
sizable from about 6000 feet up to 10k feet. Additional virga
/top-down moistening should erode a chunk of this layer and
culminate with some sprinkles and eventually flurries once wet
bulb cooling deepens. Using primarily the HREF, this process
should initially occur across our N-NW zones this evening before
redeveloping farther S-SW after midnight with the arrival of a 500
mb jet streak and deeper saturation. However, this second batch
of ascent will still have to overcome the aforementioned moisture
deficits that were left largely untouched compared to areas
farther north that will see a bigger window for top-down
moistening. As such, most model soundings over the southern half
of the CWA show sprinkles and flurries after midnight. A steady
decay of the upper low during most of this time doesn`t bode well
for much in the way of measurable precip, so PoPs were pulled
below 15% for now.

Following the decaying low, clouds should clear from W-E with
little hesitation on Monday morning as heights aloft rebound
swiftly. Downslope winds meanwhile should ensure highs reach
into the 60s for a change, before zonal flow aloft amplifies on
Tue and Wed spurring breezy and windy conditions, respectively.
High temps from Mon-Wed should easily surpass the unusually cool
Superblend and Nationalblend numbers given dry boundary layer
conditions and favorable downslope winds. SW winds on Wed are
still favored in the 25-35 mph range given the base of a shortwave
trough arriving around peak heating. Following the buildup of
modified moisture return from the Gulf on Wed, a decent dryline
looks to develop just east of the CWA by Wed afternoon. Combined
with the aforementioned upper trough, some dryline storms should
ignite just east of our CWA. Unfortunately, a more westerly
dryline position does not appear to be in the cards with this
setup given only modest and shallow moisture return - conditions
easily overwhelmed by very dry and gusty SW winds.

A cold front on the heels of Wednesday`s trough still looks to fall
well short of the Gulf which should allow a healthier return of
low level moisture by later in the week. Precip chances still appear
reasonable late Fri into the weekend provided a low latitude and
slow moving trough overspreads much of West Texas. Not yet
believing the GFS` depiction of this wave cutting off nearby, so
for now we are siding with a more progressive trough per the GEFS
mean, ECMWF and CMC.

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

23/51/93