Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/17/18
Area Forecast Discussion
National Weather Service Denver/Boulder CO
316 PM MST Fri Feb 16 2018
.SHORT TERM...(This evening through Saturday)
Issued at 310 PM MST Fri Feb 16 2018
Main concern surrounds winds later tonight and Saturday. The flow
aloft will be increasing rather quickly by midnight tonight as
strong 120+ knot Pacific jet plows across the northern Rockies.
The right front exit region of the upper jet will arrive 09Z-12Z
so we should see a sharp uptick in winds at that time. Cross
section shows cross mountain flow will increase to 45-50 knots,
and a mountain top stable layer quickly develops with the onset of
subsidence. As a result, we expect a high amplitude mountain wave
to develop and result in peak wind gusts of 75-85 mph on the
eastern slope of the Front Range mountains late tonight. Can`t
rule out stronger winds given the favorable parameters, and latest
HRRR is suggesting peak gusts reach 90+ mph in wind prone areas
of the foothills. There is some concern that the stronger gusts
may attempt to push out onto the nearby adjacent plains, so will
continue to monitor the Boulder-Golden corridor for possible high
winds in this setup.
There should be some light snow in the northern mountains as mid
level moisture increases. This wave of moisture is currently
pushing through western Wyoming and northern Utah and should reach
the northern Colorado mountains by mid evening. Moisture depth and
instability are limited so only light snow with a dusting to 2
inches expected from Rabbit Ears Pass and the Indian Peaks
northward.
On Saturday, winds are expected to gradually subside as mountain
top stable layer lifts, resulting in weakening mountain wave.
Westerly flow also gradually relaxes before next big push of winds
tomorrow night.
Temperatures will warm about 10 degrees more for Saturday with
warm advection in place. Should see highs on the plains reach the
50s, with 40s in the foothills, and 20s/30s in the mountains.
.LONG TERM...(Saturday night through Friday)
Issued at 310 PM MST Fri Feb 16 2018
Westerly winds at mountain top will increase Saturday night again
as a jet sinks south towards the area and as the surface pressure
gradients increase. Direction will begin to change to just south
of west...favoring the Mummy Range for seeing the strongest gusts.
Will allow the High Wind Warning to extend into Saturday night
with gusts up to 80 mph possible. Would not be surprised if we
could drop the zones including the mountains and foothills along
and south of I-70 from the warning that night where they`re less
likely to see the higher gusts.
A system will begin to drop into the Pacific Northwest Sunday
bringing warmer temperatures to the area in southwest flow,
readings will be in the low 60s over the plains. Flow will
increase as well, keeping windy conditions over the mountains. At
the surface, a low will deepen over the eastern plains before
sinking south that evening. Tight pressure gradients will increase
winds, bringing a fire weather concern to the plains with
humidity in the low teens. Slightly more humid airmass will push
into the northeastern corner of the state as the surface low sinks
south. Snow will push into western Colorado during the day, then
push into the mountains Sunday evening with up to a few inches
possible overnight.
Cold front will push down the plains Monday morning to bring snow
to the front range urban corridor. The front and will slow its
speed keeping the better chance of snow along and west of I-25,
before the better moisture and colder air pushes down Monday
evening. The upper trough will lift north Tuesday bringing the
moisture with it, but high surface pressure will slide south into
the Great Plains to keep some light upslope flow and cold air
damned into the area. Temperatures will struggle to get higher
than the low 20s. Initially at this time, snow fall amounts may be
in the 6 to 12 inch range for the mountains, and in the 1 to 5
inch range for the plains. But plenty of time between now and
then.
Flow aloft will remain southwest Wednesday through Friday as a
series of shortwave upper troughs continue to pushes down from
the Pacific Northwest. A surface trough develops along the lee of
the mountains Wednesday and Thursday to allow for temperatures to
warm up. Enough moisture in the southwest flow may push in
Thursday and Friday for a chance of snow into the mountains.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 310 PM MST Fri Feb 16 2018
VFR conditions will prevail through tonight. Light/variable winds
under 8 knots at KDEN and KBJC should eventually swing around to
south/southwest winds 02Z-05Z tonight. Southerly winds may hold
through the day but increase to around 12-15 knots. There is a
chance that mountain wave reflection produces a period or two of
gusty west winds up to 25 knots after 09Z tonight.
At KBJC, gusty west winds are likely to develop 06Z-09Z tonight
and strengthen through 12Z. Peak gusts 35-45 knots will be likely
there, although a slight chance winds could gust upward of 50
knots 12Z-16Z Saturday.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from midnight tonight to 8 AM MST Sunday for
COZ033>036.
&&
$$
SHORT TERM...Barjenbruch
LONG TERM...Kriederman
AVIATION...Barjenbruch
Area Forecast Discussion
National Weather Service Melbourne FL
833 PM EST Fri Feb 16 2018
.DISCUSSION...High pressure ridge will continue to extend across
the area with mostly clear skies and light winds again favoring
fog formation overnight. Both the HRRR and local WRF guidance
indicate stratus and fog initially spreading eastward across west
central and north Florida near to after midnight, reaching Lake
County, northern Volusia County and potentially the I-4 corridor
late tonight through daybreak Saturday. Will therefore keep areas
of fog in the forecast across this region with patchy fog farther
south. Locally reduced visibilities of a quarter of a mile or
less will again be possible, especially across northern areas.
Temperatures will fall into the low 60s for most locations after
midnight, except upper 50s for a few low lying and normally cooler
locations.
&&
.AVIATION...VFR conditions should remain in place through
midnight, then patchy/areas of fog will reduce cigs/vis into late
tonight. Best stratus/fog potential will be for the northern
interior TAF sites and across KDAB through early Saturday morning,
with LIFR conditions possible. As fog and stratus burn off by
late morning, predominant VFR conditions will return for the
afternoon.
&&
.MARINE...S/SW winds 5-10 knots will become W/NW into late tonight
with a weak land breeze pushes offshore. Seas will range 2-4 feet.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 59 79 60 79 / 0 0 10 0
MCO 61 84 61 84 / 0 0 10 0
MLB 63 82 62 81 / 0 0 10 0
VRB 59 82 61 82 / 0 0 10 0
LEE 61 84 61 84 / 0 0 10 0
SFB 62 83 61 83 / 0 0 10 0
ORL 64 84 63 83 / 0 0 10 0
FPR 58 82 60 82 / 0 0 10 0
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Weitlich/Pendergrast
Area Forecast Discussion
National Weather Service Nashville TN
842 PM CST Fri Feb 16 2018
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Isolated showers are showing up on radar across southern Middle
Tennessee this evening, and the HRRR suggests this trend will
continue throughout the evening, so am including POP`s prior to
06Z. Also increased cloud cover, as the current satellite and
surface obs aren`t showing many breaks. Hourly temperature grids
are holding up well, so no changes to overnight temperatures are
planned.
&&
.AVIATION...
00Z TAF DISCUSSION.
Frontal boundary south of all terminals will lift northward
tomorrow bringing more rain and low cigs. Expect a period of VFR
cigs overnight before deteriorating again in the morning. The
window of heaviest rain will be between 14z-21z for CKV, BNA, and
MQY. Rain will hold on longer at CSV. Northerly winds will be
around 5-10 kts overnight before relaxing and veering to the east
shortly after daybreak. By the end of the period winds will have
a westerly component below 5 kts.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......08
AVIATION........Reagan
Area Forecast Discussion
National Weather Service Blacksburg VA
656 PM EST Fri Feb 16 2018
.SYNOPSIS...
A series of upper-level disturbances will continue to track from
west to east across the region over the next few days.
Meanwhile, a Canadian cold front will move slowly southward through
the region tonight, then stall across the Southeast. Light to
moderate rainfall will accompany the front tonight. Then, an upper-
level disturbance will bring a chance of wintry precipitation to the
area Saturday as the cold air settles in place. Then early next
week, a warm front will move back north bringing unseasonably warm
temperatures to the area that will last several days.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 6:45 PM EST Friday...
For the most part, forecast seems on track. Incoming high
resolution guidance is trending toward slightly warmer than
previously forecast, so nudged overnight lows up a bit.
Adjusted PoPs to better reflect current radar and to dissipate
near completely in the next few hours.
As of 308 PM EST Friday...
A cold front will drop southeast across the region this evening into
tonight. A shortwave moving across the northern states will help to
ensure that the front moves through the entire CWA and down into the
Southeast States before it stalls during the weekend. Scattered
showers noted on WSR-88d images ahead of and along the front
boundary will move southeast across the region tonight. Utilized a
blend of HRRR and Conshort will pops this evening, then shaped pops
towards NAM tonight. As the front becomes parallel to the upper flow
and encounters the strong upper ridge, it will begin to lose a lot
of the associated precipitation. Low temperatures tonight are tricky
and will depend on how far south the boundary pushes. In general,
Lows overnight will range the lower 20s in northwest mountains of
Greenbrier county to the upper 30s in the Piedmont.
An upper disturbance will track northeast from the Mid-South and
bring about a threat for wintry precipitation Saturday. Strong wedge
will be in place across the region as shortwave and isentropic lift
stream up over the top. As a result a wintry precipitation will
spread northeast across the region on Saturday. Precipitation
falling into the wedge with below freezing wet bulb temperatures
will help deepen the cold air at the surface, while warm air aloft
surges well above freezing. Ptype and amounts are a challenge in
Saturday forecast. Expecting a mixture of snow,sleet, freezing rain
and rain on Saturday. Total Accumulations with mixed precipitation
are quite tricky as sleet/freezing rain greatly reduce amounts on
the ground. Ground temperatures may also influence totals. Expect
snow/sleet amounts to be generally in the 1 to 4 inch range with a
glaze of ice. The heaviest snow will occur in northern portions of
forecast area mainly north of I64 with 2 to 4 inches. The highest
ice accumulation will occur along the Blue ridge mountains. Used the
Forecast blender on Saturday to produce an ensemble Ptype and
totals with complex temperature profiles. Utilized an non
diurnal temperature curve on Saturday with high temperatures
from around 30 degrees in the north to about 40 degrees in the
south.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
As of 308 PM EST Friday...
Cool wedge is forecast to linger through Saturday night with precip
fading from west to east as the weather disturbance moves quickly
northeast and away from the forecast area. Bulk of any lingering
precip should be over by midnight with partial clearing after
midnight. Winds will come around to the northwest by daybreak
Sunday, downslope drying leading to fair weather and warmer
temperatures for Sunday.
Brief break Sunday will be quickly followed by increasing clouds and
rain late Sunday night and Monday. The bubble of high pressure
which rolls across the area Sunday will waste little time moving off
the coast with return southwesterly flow allowing a warm front to
move north through the area Monday. There may be some ptype issues
around daybreak Monday with potential for freezing rain especially
from the Alleghany Highlands through northern Greenbrier, but at
this time the threat looks rather limited. A lot will depend on how
fast the clouds move back in Sunday night and whether they will
prevent temperatures from falling to near freezing. It is forecast
to be plenty warm aloft with 85H temps of +4 to +7 deg C, so p-type
favors rain unless the boundary layer temperatures can fall back to
freezing.
The warm front which moves through the area Monday will provide a 6-
12 hour window of precipitation with QPF of about a quarter /0.25/
to a half /0.50/ an inch...another beneficial wetting, but no
flooding.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 300 PM EST Friday...
Synoptic pattern features strong subtropical ridge of high pressure
from the central/eastern caribbean up toward Bermuda. As a result,
well above average mid-level heights are forecast across the eastern
U.S. with values in the 582-588 DM range. Relative to climatology,
this is 2 to 2.5 standard deviations above normal.
This set-up favors much above normal temperatures for the Southeast
States with the baroclinic zone forced to reside on the west side of
the Appalachians from East Texas to the Ohio Valley and into the
eastern Great Lakes. Repetitive rainfall is likely within this
corridor during the week with our forecast area far enough east of
the boundary to escape anything significant. Toward the end of the
week, models hint that a surface front will impinge on the forecast
area, but overall weather conditions for mid week feature above
normal warmth and only a chance for showers pending any instability
within the warm subtropical airmass.
Temperatures Tuesday and Wednesday are expected to be 20-30 degrees
above normal with highs in the 60s/70s and lows in the 40s. Models
suggest potential for a backdoor front to impinge from the north-
northeast Thursday, so somewhat cooler/wetter conditions are favored
for the end of the week.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
As of 1237 PM EST Friday...
VFR conditions will start the TAF period at most locations as
drier air moves in from the north. At the higher elevations of
BLF and LWB MVFR or worse conditions will continue to be
possible into the evening as any remaining showers in the area
begin to dissipate. A wedge will begin to set up overnight,
trapping the colder air at the sfc. An upper-level disturbance
will pass over the region tomorrow bringing a shot of mostly
cold rain into the region by the afternoon. Evaporative cooling
into the drier layer at the ground will cause precipitation to
become a mixed bag of rain, snow, sleet and freezing rain,
mainly at higher elevations caught under the wedge. Ceilings and
visibilities will drop to MVFR/IFR in precipitation.
Winds at the onset of the TAF period will be from the northwest
and slowing down from their late afternoon peaks, eventually
becoming light and variable. During the day they will shift
toward the east, topping out around 10 mph early in the day.
Extended Aviation Discussion...
Sub-VFR cigs/vsbys in rain or mixed precipitation will continue
into Saturday night before VFR returns again on Sunday under
weak high pressure. The cold/wintry weather will be brief as a
warm front lifts back north into the area on Monday with another
round of sub- VFR, especially mountains. High pressure
strengthens offshore resulting in a return to overall VFR
Tuesday ahead of the next cold front well west of the
Appalachians. Scattered MVFR showers are expected Wednesday into
Thursday.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Winter Weather Advisory from 10 AM Saturday to midnight EST
Saturday night for VAZ011-014-017>020-022>024-032>035.
NC...None.
WV...Winter Weather Advisory from 10 AM Saturday to midnight EST
Saturday night for WVZ044-507-508.
&&
$$
SYNOPSIS...KK/RAB
NEAR TERM...JR/KK
SHORT TERM...PM
LONG TERM...PM
AVIATION...JR/KK