Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/20/17
Area Forecast Discussion...UPDATED
National Weather Service Birmingham AL
615 PM CST Thu Jan 19 2017
.UPDATE...
For 00Z Aviation.
&&
.SHORT TERM...
This Afternoon through Friday.
--Significant severe weather potential on the board for this
weekend--
Central Alabama was generally in the warm sector this afternoon. A
developing low was located along the Mississippi River south of
Memphis with a cold front extending southward. A warm front was
located across northeast Alabama into central Georgia. A trough was
analyzed with the more organized line of storms stretching from
central to southwest Alabama.
The current rap analysis has plenty of atmospheric shear near the
line of storms and low LCL`s. Therefore, rotation is possible and
weak rotation has already been noted in the lower levels. This area
of storms did produce a tornado back in Mississippi earlier this
morning. Surface based instability has been limited today due to the
low clouds, fog and drizzle/showers. But the latest water vapor
imagery has the upper trough beginning to turn negative with some
good heating noted south. Upper level divergence will increase as
well as the wind speeds. Therefore, some destabilization is
anticipated the next few hours, especially south. Will continue to
mention a threat of a brief tornado or some damaging winds along and
ahead of the line of storms, and south of Interstate 20. This area
is moving rather slowly but may pick up some speed. Due to
uncertainty in speed, held the threat through midnight east.
Rain chances very slowly decrease from west to east into Friday
morning. Did hold onto some chance pops south a leftover boundary
from the convection hangs over the area. Overnight lows will be very
similar to last night mainly in the 50s. With little change in the
airmass, went near record highs on Friday especially south.
75
.LONG TERM...
Friday Night through Weekend.
--Instances of severe weather this weekend. Significant severe
weather possible across southern portions of the service area--
*Headline: Rounds of thunderstorms are expected to move through the
region this weekend. Friday night to Sunday morning holds the
greatest potential for severe weather. Details on threats, timing,
and areas are outlined below.
*Weather setup: Several impulses will emanate from a southern U.S.
longwave trough, while a very strong ~125-knot jet streak moves into
northern Mexico, instigating the development of an upper-level low.
Our severe weather potential will be tied to the broad southwesterly
flow preceding the upper low, and with associated upper- and low-
level lobe impulses translating through the region. Dynamics-wise,
the low-level wind field will essentially be a mishmash of
comparatively laxed winds and surges of ~35-45 knots (key factors in
subsequent severe activity), southwest at 850mb. Instability-wise,
CAPE will be available alongside a plume of steeper lapse rates.
*Forecast changes: There are no changes to threat areas or hazards.
As of Thursday afternoon, we are maintaining a swath of `elevated`
severe weather risk through roughly the southern-half of the service
area, with a `limited` risk points north. Refer to the severe
weather threat graphic on our homepage.
*Impacts_Severe: There will be a risk of tornadoes, severe-
caliber hail (1"+), and severe straight-line winds.
Multiple rounds of thunderstorms are expected:
1) Friday night through Saturday morning as storms advance into
the area from Mississippi and southern Alabama, associated with an
inland- moving boundary. This could end up being the main show,
focused on roughly the southern-half of the service area (and
toward the immediate Gulf coast). Supercells and thunderstorms
segments are expected. Forecast models are suggesting a zone of
backed surface and low-level winds in the vicinity of a northward-
moving maritime air mass, locally enhancing hodographs and SRH as
the first low-level jet surge occurs. This will be a principal
area to watch as storms interact with the boundary. A best
estimate `window of concern` (this will be adjusted) appears to
line up from 09Z/3AM Saturday to 18Z/noon, or so;
2) A questionable period Saturday afternoon when renewed
thunderstorm development is uncertain (pending morning storm
characteristics/progression, trigger), but would have severe
potential if recovery is realized to the extent of some model
projections; and
3) Saturday night as another impulse moves through, especially
toward southeastern counties. This will be another period to watch
closely as it`ll be associated with another low-level jet impulse.
*Impacts_Hydro: Analysis from our senior hydrologist indicates that
streamflow remains low across area rivers. It is anticipated that
basins will be able to handle forecast storm total rainfall amounts
of 2-4 inches. However, localized flooding could occur in poor-
drainage areas or small streams, associated with any heavy downpours.
89^GSatterwhite
&&
.AVIATION...
00Z TAF Discussion.
Line of showers and thunderstorms moving across Central Alabama at
this writing. Line is already through TCL/BHM/EET and about to
move through ASN/ANB then MGM/TOI. Some lower cigs/reduced vsbys
possible with the TS. However, expecting -RA then later
transitioning to -DZ after midnight as system progresses. With
IFR/LIFR cigs expected behind the rain some fog is also expected
to develop and last through mid morning.
08
&&
.FIRE WEATHER...
A wet and chaotic pattern sets up today through Sunday. Afternoon
relative humidity values will generally remain above 40 percent
due to the southerly winds bringing gulf moisture northward. Some
strong to severe storms can be expected today, Saturday and Sunday
morning. Rain amounts through Sunday will be 3 to 4 inches.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 56 72 56 68 54 / 100 30 40 70 80
Anniston 59 74 59 69 56 / 100 30 50 70 80
Birmingham 58 74 59 69 56 / 90 20 60 70 80
Tuscaloosa 59 76 60 72 57 / 90 20 60 70 70
Calera 59 75 60 70 57 / 90 20 60 70 80
Auburn 60 75 61 70 59 / 90 30 60 90 80
Montgomery 60 79 62 73 58 / 90 30 90 80 80
Troy 61 78 63 73 60 / 90 30 80 90 80
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
None.
&&
$$
75/89/08
Area Forecast Discussion
National Weather Service Denver/Boulder CO
659 PM MST Thu Jan 19 2017
.UPDATE...
Issued at 645 PM MST Thu Jan 19 2017
Satellite shows fog moving westward from Kansas into the far
eastern plains at this time. The RAP and HRRR continue to show
this trend overnight, with the fog primarily impacting eastern
sections of Sedgwick, Phillips and Washington Counties. This fog
then gets flushed east late tonight and Friday morning. Have
included areas of fog in these zones tonight and also increased
the cloud cover there. In the mountains, we increased the pops,
but no adjustments to the snow amounts as the overall totals still
appear to be on the light side.
&&
.SHORT TERM...(This evening through Friday)
Issued at 308 PM MST Thu Jan 19 2017
Models show southerly flow aloft overnight into Friday morning. The
flow weakens and becomes southwesterly by afternoon. There is a
weak upper trough that moves across the CWA from 09Z to 21Z on
Friday. The QG Omega fields show some moderately strong upward
synoptic scale energy for the CWA tonight and much of Friday. The
low level wind fields have southeasterlies this evening, then weak
normal drainage winds overnight. Winds are weak and downsloping
for the most part on Friday. Models have moisture on the increase
tonight from west to east. By 12Z Friday morning, moisture is
deep over the mountains and that continues through Friday. There
is plenty of moisture over the plains, but not in the lower levels
on the GFS or the ECMWF. The QPF fields have limited measurable
in the mountains tonight and Friday. There is a tad of measurable
precipitation over the plains on Friday. For pops, will go with
50-80%s in the mountains from about 06Z tonight through Friday.
Orographic enhancement is not the greatest, but there is moisture
and some synoptic scale energy. Snowfall amounts do not warrant
highlight criteria amounts. For the plains, will go with mostly
"chance"s late tonight into Friday afternoon. For temperatures,
Friday`s highs are 3-6 C cooler than this afternoon`s.
.LONG TERM...(Friday night through Thursday)
Issued at 308 PM MST Thu Jan 19 2017
A series of weakly organized weather systems will move across
Colorado over the weekend, and then a bit stronger system will
move over the state during the first half of next week. Each
system will bring a little light snow to the mountains, but not
necessarily affect the plains. The system that sets up over the
state for the Monday through Wednesday time period will have more
of a region-wide impact. The first trough, on Saturday will be
diving southeastward as it produces the bulk of snowfall over the
western slope and San Juan mountains. The north central mountains
will see scattered afternoon snow showers. Upper ridging will
build over the state Sunday with dry weather across the forecast
area.
Monday will be transitional as an upper trough carves out over
the entire western United States. By Monday evening snow should be
moving into the mountains. Then on Tuesday the ECMWF shows an
upper low developing over over northeast Colorado which will lead
to unsettled weather across the mountains and plains. A strong
upper level jet will accompany this trough which may add to the
strength of the developing system. The GFS shows a very similar
solution, so we will have to watch how much moisture this system
brings with it. Unsettled weather and cooler temperatures are the
main story for now.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 645 PM MST Thu Jan 19 2017
The southeasterlies should move towards normal drainage
directions, south/southwest after 03Z this evening. MVFR ceilings
020-030 after 10Z Friday morning with a chance of snow showers.
Ceilings should climb back above 060 by 18Z Friday, with VFR
conditions in the afternoon.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Cooper/Meier
SHORT TERM...RJK
LONG TERM...Dankers
AVIATION...Cooper
Area Forecast Discussion
National Weather Service Duluth MN
552 PM CST Thu Jan 19 2017
.SHORT TERM...(This evening through Friday)
Issued at 419 PM CST Thu Jan 19 2017
Hopefully everyone in the area got outside today, as conditions
are going to get progressively worse tonight, with clouds
overspreading the area from the south this evening, and then
precipitation spreading in from the south as well. Stratus is
currently over southwest Minnesota, eastern South Dakota and
Nebraska, and spreading in our direction. It should advance into
the forecast area here in 2-4 hours, continuing north during the
evening. RAP 900-925 RH progs have been good indicators of this
stratus during the daytime, and I expect that to continue, even
showing the stratus accelerating some this evening as would be
expected. Towards morning, an area of lift will rotate across the
area as a shortwave and weak vort max pushes across the area,
bringing a band of precipitation and warm temperatures aloft
across the area during the early morning and most of the day on
Friday. Of great concern are the surface temperatures, which
should dip to around freezing this evening and then fluctuate
around there through the night before rising again in the morning.
Have concerns that the precipitation will be freezing
drizzle/freezing rain instead of liquid rain/drizzle, causing
icing on local roads. Road surface temperatures this afternoon are
in the 40s and low 50s, with sub surface temperatures in the low-
mid 30s. It will be a very near thing, and is going to depend on
exact values as the precipitation moves in. In addition to all of
this, the warm temperatures over the snow are going to produce
copious amounts of fog again tonight. We are likely to need
headlines once again, but the specific location of the lowest
visibilities is uncertain still, though am favoring northwest
Wisconsin for the worst conditions overnight. Friday temperatures
should warm enough to bring precipitation back to liquid for most
locations as the precipitation comes to an end from south to
north.
.LONG TERM...(Friday night through Thursday)
Issued at 419 PM CST Thu Jan 19 2017
Wintry precipitation is expected Friday night through the weekend
with another system moving into the region around midweek.
A distorted Omega Block pattern will continue over the Plains
and Upper Midwest Friday evening through the weekend. An upper low
will meander northward through the region and into the Canadian
Prairies by Saturday morning. Warm air aloft and near the surface
will continue, leading to numerous challenges regarding precipitation
type. Another shortwave trough will rotate northward into the Upper
Midwest Saturday night and Sunday with precipitation chances
continuing. A mix of rain, freezing rain, and snow is likely Friday
night gradually switching over to a rain/snow mix and eventually all
snow by Sunday night. There is a potential for around one-tenth of
an inch of ice accumulation Friday night and Saturday in the high
terrain along the North Shore, with less ice accumulation expected
elsewhere. Surface temps will be the main governing force in
precipitation type through Saturday night. If forecast temps are even
a few degrees too cool, precip will likely be all rain instead of a
mix.
The blocking pattern aloft will continue during the first half of
the week with slight chances of rain or snow. A more organized
shortwave trough and slug of vorticity will move into the Upper
Mississippi River Valley Tuesday night through Wednesday night. The
midweek system will bring another round of rain/snow to the
Northland. Temperatures will remain fairly mild through the end
of the forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 552 PM CST Thu Jan 19 2017
Largely VFR conditions have been found across the TAF sites this
afternoon, but things will change considerably as the night wears
on. An elongated area of low pressure and upper level shortwave
will lift northward across the region overnight. Any VFR
conditions are likely to give way to IFR/LIFR or even VLIFR
overnight. A wintry mix of precipitation is expected, which will
generally turn to rain on Friday.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 32 37 31 37 / 30 80 50 70
INL 28 38 30 38 / 10 70 70 50
BRD 31 37 31 38 / 50 60 40 60
HYR 33 40 33 41 / 70 70 40 60
ASX 32 40 32 40 / 40 70 50 60
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
SHORT TERM...LE
LONG TERM...Huyck
AVIATION...DAP
Area Forecast Discussion
National Weather Service Jacksonville FL
853 PM EST Thu Jan 19 2017
.UPDATE...
A few showers developed on the Gulf Coast seabreeze this afternoon
near the Gainesville area and these showers continue to push
northeastward towards Jacksonville, weakening in the process. We
also had an Atlantic seabreeze today which collided with the gulf
coast seabreeze, a very unusual occurrence for this time of year.
The main update was to add 20% pops to account for this activity,
which should wind down completely here in the next hour or two.
Parts of the Jacksonville area could get a light sprinkle but it
shouldn`t amount to much. The main line of showers/storms upstream
will continue to march in our direction overnight but is expected
to weaken significantly as it reaches our western zones late
tonight. As a result, we will continue with only slight chance
pops to account for a few leftover light showers with this
activity late tonight.
We also backed off a little on the fog wording overnight. The
transitioning state of the atmosphere is not really favorable for
significant fog development tonight. Upper trough pivoting along
the northern Gulf Coast will continue to nudge the upper ridge,
which has had a stronghold over us this past week, eastward. This
will bring a gradual increase in clouds and winds just above the
boundary layer overnight, thus fog development should be held
somewhat in check. Still cannot rule out the possibility of some
areas of fog across our western Florida zones, mainly along and
west of the I-75 corridor.
&&
.AVIATION...
Conditions tonight are not nearly as favorable for fog like they
were last night. Best chance for IFR conditions will be at the GNV
TAF site where the SREF shows a medium chance of some advection
fog moving in from off the Gulf. The HRRR is way more aggressive
with the fog bank off the Gulf, bringing it all the way into the
Jacksonville area again. But so far the HRRR has been way
overdone and we will side with the SREF and stick with mainly just
MVFR impacts for TAF sites along and east of the I-95 corridor.
The exception will be at VQQ where typical shallow ground fog will
develop.
&&
.MARINE...
Relatively benign conditions will continue overnight with some
patchy fog possible. No updates needed.
Rip Currents: Low Risk.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 59 78 62 72 / 20 20 20 80
SSI 58 76 62 71 / 10 20 10 60
JAX 60 81 62 77 / 20 20 10 40
SGJ 62 79 61 78 / 20 20 0 20
GNV 59 79 60 77 / 20 20 10 40
OCF 59 79 61 79 / 10 20 10 10
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&
$$
Shuler/Sandrik/Shashy
Area Forecast Discussion
National Weather Service Phoenix AZ
835 PM MST Thu Jan 19 2017
.SYNOPSIS...
A series of Pacific storm systems will move into the region. After a
weak disturbance tonight, a stronger and wetter system will affect
the region Friday through early Saturday. Snow accumulation will be
above 5500 feet, with a Winter Storm Warning posted for the
mountains east of Phoenix. A break in the weather is expected
Saturday night and early Sunday, however another Pacific storm is
expected in the region later Sunday through Monday night. Dry but
cool weather will settle over the region for the middle of next week.
&&
.DISCUSSION...
The 1st in series of Pacific storm systems that will be affecting
our region over the next several days is now moving across South-
Central AZ at this hour. Current 88D radar imagery is showing very
light shower activity moving eastward across Maricopa County, and
into southern Gila county. So far, rainfall amounts with this system
have been quite, light, mainly 0.10 inch or less, with many spots
only seeing trace amonuts of rainfall. Latest HRRR high-res model
guidance continues to show light shower activity developing through
the rest of tonight over south-central AZ, but with many areas
likely not seeing measurable rainfall between now and Friday
morning. Further to the east, the rainfall should turn to snow above
5500 feet, with a few inches still possible over the highest peaks
of our cwa between now and early Friday. For the short term, have
adjusted POPS downward through the rest of this evening and up a bit
overnight over the lower deserts to reflect updated high-res model
forecasts, and also made some adjustments to hourly
temp/dewpoint/wind grids to better reflect current trends.
&&
.PREVIOUS DISCUSSION...
Tonight through Saturday...
A series of Pacific weather systems has begun to move into the
region. The first one, a minor one, moved through southwest and
south central AZ this morning, followed by another system late this
afternoon and evening. Most showers through tonight will be on the
light side, except in the upslope areas of southern Gila county
where rain and snow should be a little heavier.
With the passing systems tonight through Saturday, snow levels will
rise and fall with each system. For example, in the area where we
have a Winter Storm Warning in southern Gila County, snow levels
fall to near 5500 feet late tonight, lift to 6000 feet Friday
evening, then fall to 5000 feet by Saturday morning. In general the
Winter Storm Warning in southern Gila County is posted above 5500 ft
where storm total accumulations by Saturday afternoon could reach
nearly a foot in the highest elevations.
With the cold frontal passage Friday night, low level winds at 5000
feet begin to approach 45-60 mph in a belt from just east of Yuma to
Phoenix. Rainfall and isolated thunderstorms could tap this momentum
to develop gusty surface winds in the 30 to 45 mph range, higher
near thunderstorms. A Wind Advisory is posted for southwest and
south central AZ Friday night.
Sunday...
A break in the weather will develop Sunday afternoon, but with
cloudy skies and a slight chance of showers over the mountains of
southeast CA ahead of the next weather system for Sunday night and
Monday.
Sunday night and Monday...
Another Pacific weather system will move into the region this
period. The character of precipitation will be light. Additional
snowfall is expected in southern Gila County above 5800 feet Monday
afternoon and evening with perhaps an inch or two.
Tuesday through Thursday...
Partly cloudy, drier and colder weather is expected this period
under northerly flow aloft from Nevada and Utah.
&&
.AVIATION...
South-Central Arizona including KPHX, KIWA,and KSDL:
Expecting sct-bkn ceilings to in the 3-5k foot range to continue
this evening. Showers are approaching from the west and should begin
to affect terminals as early as 22Z, persisting through 06-07Z. Rain
should become more spotty after this period across south-central AZ,
with some improvements in ceilings possible to around 8k feet.
Easterly winds around 5 kt should be maintained through late evening
as well, before a shift towards the southwest is anticipated after
06Z.
More widespread rainfall is anticipated late Friday evening and
Saturday morning and will be associated with another period of
increased cloud cover. Winds will also strengthen during this time
as a cold front approaches, shifting from southerly to westerly by
early Saturday morning.
Southeast California/Southwest Arizona including KIPL and KBLH:
Areas of sct-bkn ceilings as low as 7k feet, along with scattered
showers, have developed across southeast California into the lower
Colorado River Valley. Otherwise, expect sct clouds with bases near
10-12k ft this afternoon and overnight. Gusty west winds are still
anticipated to develop across the Imperial Valley this afternoon,
before weakening around 03Z. Periods of more widespread showers are
possible across the area Friday afternoon, and will be associated
with an increase in westerly winds.
Aviation discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Saturday through Wednesday: After a brief respite from the rain
Saturday evening through Sunday morning, precipitation associated
with another low pressure system will develop Sunday afternoon and
evening across the Desert Southwest. Additional rainfall is likely
Monday along with breezy to windy conditions. High pressure will
gradually rebuild across the area Tuesday and Wednesday, resulting
in a drying trend though temperatures will remain below normal. Fire
danger will remain low through the period due to the persistent and
anomalously moist conditions.
&&
.SPOTTER INFORMATION STATEMENT...
Spotter reports of rain and snow will likely be needed later this
week.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Winter Storm Warning from midnight tonight to 11 AM MST Saturday
for AZZ024.
CA...None.
&&
$$
Visit us on Facebook...Twitter...and at weather.gov/phoenix
DISCUSSION...Percha/Vasquez
AVIATION...Hirsch
FIRE WEATHER...Hirsch
Area Forecast Discussion
National Weather Service Blacksburg VA
1104 PM EST Thu Jan 19 2017
.SYNOPSIS...
High pressure centered over our region this afternoon will shift
east to the coast tonight as a warm front lifts north from the Gulf
Coast states into the southern Appalachians. The warm front will
swing north across Virginia and into the mid-Atlantic Friday, before
stalling. Another storm system moving across the southern U.S. will
impact our region Sunday into Monday.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 1100 PM EST Thursday...
Adjustment to the forecast address to main features, overnight
low temperatures and timing of arrival of precipitation. Several
locations over parts of Southside Virginia and neighboring
portions of north central North Carolina are already
experiencing temperatures in the upper 30s. Forecast lows were
in the lower 40s. Have adjusted forecast lows to reflect
readings not too much lower than the ongoing readings, allowing
for additional slow cooling into the early morning hours before
a slight rise in temperatures before sunrise as weak warm air
advection starts.
Have slowed the arrival of rain into the region from west to
east. This amounted to not a whole lot of changes across the
western portions of the area, but for eastern areas, the arrival
of the main area of rain looks delayed until a little after
sunrise Friday.
As of 700 PM EST Thursday...
Incoming moisture is hitting a wall of dry air this evening,
therefore slowed the arrival of rain entering the forecast area
until after midnight. Otherwise no major changes to previous
forecast.
As of 200 PM EST Thursday...
Upper Ridge over our region this afternoon will slide east tonight
into Friday. Warm advection high clouds this afternoon will be
followed by increasing mid clouds starting to roll into the
southwest by dusk.
Low pressure over western Tennessee this afternoon will lift
northeast into the Ohio Valley tonight and reach Lake Erie by Friday
afternoon. A warm front trailing from the low will lift northward
tonight into Friday. Isentropic lift increases this evening across
the mountains of North Carolina and shift to the rest of the
forecast area overnight. With a dry airmass in place, slowed down
the onset of the rain this evening. Used a blend of HRRR and
HiResW-arw-east for pops this evening, then utilized a mix of NAM
and Continuity with pops tonight into Friday. The best chance for
rain is in the mountains with lower threat in the Piedmont. Lower
dewpoints in the evening combined with increasing moisture may
allow for temperature drop once the rain starts to fall tonight.
However, it should remain mild with low temperatures ranging from
the upper 30s in the Alleghanys and portions of the Greenbrier
Valley to upper 40s to about 50 degrees in Mountain Empire.
On Friday, the best lift will push quickly northeast through the
region. An upper level shortwave ridge will build over the Mid-
Atlantic region. The bulk of the rain will have moved northeast of
the area by the early to mid afternoon. Added the mention of fog to
isc grids. Lowered high temperatures a few degrees especially in the
north Friday with clouds and rain. High temperatures Friday will
vary from the upper 40s in the mountains to the lower 60s in the
south. Rainfall amounts overall will average around a quarter inch
with locally higher in the western mountains of Southwest Virginia
and North Carolina.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 300 PM EDT Thursday
Even with limited sunshine on Saturday the air mass will be
unseasonably warm, 15 to 25 degrees above normal. Deep moisture
begins to arrive back into the area from the southwest on Saturday
afternoon. But Bufkit not showing a saturated sounding until closer
to Sunday morning.
Models forecasting good lift Sunday with a strong vorticity maximum
crossing the central and southern Appalachians along with upper
diffluence. Winds at 850MB back to the southeast by 12Z/7AM Sunday
with good upslope and increasing inflow off the Atlantic first
along the Appalachians in northern North Carolina on the Sunday
morning gradually shifting north of Roanoke by the end of the
day.
More significant differences in the guidance in the amount of
instability across southern Virginia and northern North Carolina on
Sunday all related to the location of the warm front. 12Z NAM/GFS
and latest RAP indicating enough of a secondary low developing
over eastern North Carolina that with the precipitation there
should be strong in-situ wedging. Large spread in location of
heaviest rain also so will lean toward WPC guidance. Wedge and
precipitation will keep temperatures on the cool side/or below
guidance for Sunday. Have added slight chance of thunder from
extreme southern Virginia into northern North Carolina but
confidence is low.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 200 PM EDT Thursday
Precipitation will remain in the area through Monday with the
highest rain amounts on Sunday night and Monday, mainly along and
east of the Blue Ridge. Experimental hydrologic ensembles
showed at least a small potential for 1 to 3 inches of rain.
Localized minor flooding is possible if this amount of
precipitation is realized.
Once the surface low is off the coast on Monday night and Tuesday,
precipitation will be confined to favored western upslope areas.
Enough colder air comes in Monday night that we will have snow
in the forecast from southeast West Virginia into northwest
North Carolina. Winds will also increase Monday night and
Tuesday. There may be enough of a low level jet along with cold
air advection and pressure rises for wind gusts in the 40 to 50
mph range.
By Wednesday and Thursday a long wave positively tilted upper trof
will extend from the Great Lakes across the central United States.
Prevailing deep southwest flow over the Mid Atlantic region
during this time frame results in differences among the models
in how fast any front will progress east. For now WPC has
surface front crossing the region Wednesday and Wednesday
night. Behind this system is a much colder air mass. More
upslope snow showers in the mountains are possible. At this time
the models are showing snow showers for Thursday night.
&&
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
As of 650 PM EST Thursday...
Fast moving negatively tilted short wave will rotate through the
region late tonight/early Friday, followed by an extended period
of southwest flow preceding another short wave during the
weekend and a deep low pressure area slated to move through the
southeast U.S. early next week. This system will be in/out
fairly quickly, but will leave low clouds, drizzle, fog in its
wake given the persistence of southwest flow aloft remaining in
place. It appears that the timing of this system is a little
slower than previously thought, with the main wave of rain
coming through in the 12Z-16Z time frame as opposed to 08Z-14Z
time frame. Current VFR ceilings will quickly deteriorate to
MVFR/IFR after the rain spreads into the region, then settle
into an IFR/LIFR condition during the afternoon in fog, drizzle,
low clouds. Visibility will drop into the MVFR category,
occasionally IFR during the rainfall, then settle mainly into
MVFR during the afternoon in fog and drizzle. Winds will be
mostly east-southeast 3-5kts this evening, becoming southeast
4-8kts as the rain moves into the region. Some low end gusts are
possible at KBLF with the southeast flow. Winds will become
light and variable or calm east of the Blue Ridge after the rain
moves out of the region, but become SSW-SW 4-8kts with again
some low end gusts at KBLF during the afternoon Friday.
Medium confidence in ceilings and visibilities through the TAF
valid period.
Medium confidence in wind speed/direction through the TAF valid
period.
Extended Aviation Discussion...
As noted above southwest flow aloft will persist ahead of a deep
upper low that will develop across the southeast states over the
weekend, then move off the southeast U.S. coast Monday. Low
clouds, drizzle, and fog are likely to persist Friday night with
additional waves of rain moving into the area late Saturday and
persisting into Monday. At this point it appears that the only
period of potential VFR cigs would be Saturday afternoon.
Otherwise, much of the period will be characterized by MVFR or
worse ceilings and visibilities. Winds will become strong and
gusty from the northwest Monday night into Tuesday as the major
weather system moves up the east coast. Ceilings and
visibilities should finally improve east of the Blue Ridge after
Tuesday, but likely persist with MVFR and upslope flow west of
the Blue Ridge.
&&
.CLIMATE...
As of 305 PM EST Thursday...
Record warm Mins for January 21
Blacksburg....42 in 1954
Bluefield.....47 in 1999
Danville......56 in 1954
Lynchburg.....51 in 1927
Roanoke.......51 in 1959
Record highs for January 21
Blacksburg....59 in 1954
Bluefield.....60 in 1999
Danville......68 in 1959
Lynchburg.....72 in 1932
Roanoke.......74 in 1932
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...KK
NEAR TERM...DS/KK/RCS
SHORT TERM...AMS
LONG TERM...AMS
AVIATION...KK/RAB
CLIMATE...AMS
Area Forecast Discussion
National Weather Service San Diego CA
539 PM PST Thu Jan 19 2017
Updated SKYWARN section.
.SYNOPSIS...
A very stormy pattern will continue across Southern California
through Monday. The first of several waves of stormy weather will
continue to move across the region today bringing isolated light
showers and mountain snow. The next wave will move through Friday
with heavier rain and mountain snow, possible flooding and
stronger, potentially damaging winds for portions of the region
and scattered thunderstorms. On Sunday the next system arrives
and continues into Monday, possibly bringing the heaviest
precipitation of the event. Dry weather is expected by midweek.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
The first in a series of storms has moved through the region today,
bringing moderate and locally briefly heavy showers mainly to
areas over and west of the mountains. Over the last 18 hours, the
coast and valleys have seen generally 0.50-0.75 inches, while the
coastal slopes have seen about 0.75-1.5 inches, and about
0.05-0.15 inches in the deserts. Radar shows that showers have
diminished for the most part, with just some isolated post-
frontal light showers, with the snow level around 5500-6000 ft.
Snow levels will likely stay at around that level today. Latest
HRRR shows mainly isolated showers continuing through the rest of
the day.
On water vapor satellite, the current trough can be seen moving
east across the region. On Friday a strong short-wave trough and
accompanying 130 kt jet noses its way into Southern California,
bringing a round of heavier precipitation than we`ll have today.
For this storm, showers start to increase early Friday morning,
with widespread moderate to heavy precipitation mid-Friday morning
through Friday afternoon. Showers then diminish gradually Friday
night into Saturday morning except in mountains where some showers
may linger through the day Saturday in westerly flow aloft. As far
as thunderstorm chances goes, the NAM12 and WRF show 500-1000
J/KG of most unstable CAPE and up to 30 kt of low level wind shear
late Friday morning and afternoon. Given these parameters, would
not be surprised if we see a few strong thunderstorms producing
severe wind gusts tomorrow. In addition, 850 mb winds increase to
35-50 kt out of the southwest late Friday morning and afternoon,
which will not only increase the potential for higher orographic
precipitation along the coastal mountain slopes, but also bring
strong winds not only to the mountains and deserts but also the
coast and valleys. Hi-res models show sustained winds reaching
20-30 kt over the coastal and valley areas Friday morning and
afternoon as the cold front moves through, which translate to wind
gusts of 35-45 mph and locally stronger. This, in addition to the
likely strong convective downburst that will move through the
area, has led to the issuance of a High Wind Warning for the
coasts, valleys and Santa Ana Mountains/foothills, with damaging
wind gusts possible. Meanwhile, the San Diego county deserts look
to have a bit stronger mountain wave activity Friday and Saturday
than the other desert locations, so the High Wind Watch was
converted to a High Wind Warning for those areas while a Wind
Advisory was issued for the other deserts. Meanwhile, strong wind
gusts of 70 mph or greater will be possible along the mountain
ridges and desert slopes.
A large, broad trough will move down off the coast of California
on Sunday, directing an atmospheric river into Southern
California, with precipitable water increasing to 1.4 inches. This
moisture, in addition to southwest 850 mb winds increasing to 50
kt, will bring widespread moderate to heavy precipitation, higher
snow levels, and strong winds to the region. The trough then drops
down into Southern California on Monday, bringing colder air with
it, and less intense precipitation. For rain and snow forecast
amounts and flooding potential for the next couple storms, please
see the HYDROLOGY section below. Long-range models indicate some slight
instability on Monday, so perhaps thunder will be a possibility
that day as well.
There`s the possibility that another short-wave will move through
the region on Tuesday, with the slight chance for some showers
that day.
Warming and dry weather expected starting next Wednesday as a
ridge aloft builds over the west.
&&
.AVIATION...
192130Z...SCT/BKN low cloud will continue across the region, with
bases from 1300-4500 ft MSL. SHRA and isolated TSRA will continue
through tonight. VIS will lower to 1-3 SM BR in showers. The bulk of
the precip will move out of the region by late morning. Widespread
RA will develop Friday morning and into the afternoon. Mountain tops
will be obscured at times through the period.
SW to W wind gusts of 50-60 kt will continue over the mountains,
desert mountain slopes and into adjacent deserts and through Friday.
Severe UDDFS will be possible on the lee side of the mountains
through the period.
&&
.MARINE...
Several storms moving across the region will continue unsettled
conditions through Tuesday. Winds are currently gusting at 19 kt and
seas have risen to 8 ft at the San Clemente Bouy. The Small Craft
Advisory will continue over the waters through early Friday, then
Gale force winds will develop Friday, Saturday and possibly again on
Monday. See the Small Craft Advisory and Gale Warning (LAXMWWSGX)
currently in effect for additional details.
&&
.BEACHES...
High surf is likely along the beaches through Tuesday. The largest
and potentially damaging surf is likely to occur late Friday through
Saturday, and again Monday into Tuesday. Strong rip currents and
large surf will make swimming conditions very dangerous. A High Surf
Warning remains in effect through the period. Coastal flooding and
beach erosion are possible as highest sets to 16 ft occur Friday
night through Saturday coincident with times of high tide. Highest
tide during highest surf is 4.6 ft at La Jolla 435 AM Saturday. High
Surf will diminish by the middle of next week.
&&
.HYDROLOGY...
A series of storms will move into Southern California over the
next 5 days, possibly bringing the heaviest precipitation seen
here since 2010. The storms will bring significant amounts of
rain, with heavy snow accumulations at elevations above 5000 ft.
Some areas could receive 5 to 10 inches of total rainfall between
through Monday night, possibly as much as 12 inches along the
coastal slopes. This has the potential to create an extended
period of enhanced runoff into streams and main-stem rivers. Over
time, the soil will have decreasing capacity to absorb rainfall
resulting in increasing runoff. Flash flooding will also be
possible, especially during periods of heavier rainfall.
For the Friday storm, snow levels will likely be around 5500-6000 feet
or so, with 1-2 feet of snow possible above 6000 feet and 6
inches to a foot between 5000 and 6000 feet. A Winter Storm
Warning continues for the San Bernardino and Riverside county
mountains through 6 am Saturday...and a Winter Storm Warning was
issued for the San Diego county mountains for areas above 5000
foot elevation. Storm total precipitation forecast for Friday
looks to be:
Coast and Valleys: 1-2 inches
Mountains: 2-4 inches
High Deserts: 0.15-0.40 inches
Lower Deserts: 0.10-35 inches
A Flash Flood Watch has been issued for areas over and west of
the mountains on Friday due to the likely heavy rainfall rates and
thunderstorms.
For the Sunday-Monday storm, it will be a warmer storm initially
so snow levels look to be initially high around 7000-8000 ft
Sunday then lowering quickly to 4000 ft Monday. Storm total
precipitation forecast for Sunday-Monday looks to be:
Coast and Valleys: 2-3 inches
Mountains: 3-6 inches
High Deserts: 0.50-1.5 inches
Lower Deserts: 0.25-1 inch
With precipitation amounts this heavy, more flooding issues look
likely, especially considering the precipitation amounts and
saturated Ground from previous rainfall.
When all is said and done, we could see a total of:
Coast: 3-5 inches
Valleys: 4-6 inches
Mountains: 6-12 inches
High Deserts: 1-3 inches
Lower Deserts: 1-2 inches
&&
.SKYWARN...
Skywarn activation is requested Friday morning-afternoon and
again on Sunday. Threats: Damaging winds and flash flooding and
extreme mountain snowfall.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Flash Flood Watch from Friday morning through Friday evening for
Orange County Coastal Areas-Orange County Inland Areas-
Riverside County Mountains-San Bernardino County Mountains-
San Bernardino and Riverside County Valleys-The Inland
Empire-San Diego County Coastal Areas-San Diego County
Mountains-San Diego County Valleys-San Gorgonio Pass Near
Banning-Santa Ana Mountains and Foothills.
Wind Advisory until 4 AM PST Friday for San Diego County Deserts-
San Diego County Mountains.
Winter Storm Warning from 4 AM Friday to 6 AM PST Saturday for
San Diego County Mountains.
High Wind Warning from 4 AM Friday to 10 PM PST Saturday for San
Diego County Deserts.
Wind Advisory until 10 PM PST Saturday for Apple and Lucerne
Valleys-San Gorgonio Pass Near Banning.
Winter Storm Warning until 6 AM PST Saturday for Riverside
County Mountains-San Bernardino County Mountains.
High Wind Warning from 7 AM to 10 PM PST Friday for Orange
County Coastal Areas-Orange County Inland Areas-San
Bernardino and Riverside County Valleys-The Inland Empire-
San Diego County Coastal Areas-San Diego County Valleys-
Santa Ana Mountains and Foothills.
Wind Advisory from 10 AM Friday to 10 PM PST Saturday for
Coachella Valley.
High Surf Warning until 10 PM PST Tuesday for Orange County
Coastal Areas-San Diego County Coastal Areas.
PZ...Small Craft Advisory until 10 AM PST Friday for Coastal Waters
from San Mateo Point to the Mexican Border and out to 30 nm-
Waters from San Mateo point to the Mexican Border Extending
30 to 60 nm out including San Clemente Island.
Gale Warning from 10 AM Friday to 4 PM PST Saturday for Coastal
Waters from San Mateo Point to the Mexican Border and out
to 30 nm-Waters from San Mateo point to the Mexican Border
Extending 30 to 60 nm out including San Clemente Island.
&&
$$
PUBLIC...Harrison
AVIATION/MARINE...JJT
Area Forecast Discussion
National Weather Service Tallahassee FL
847 PM EST Thu Jan 19 2017
.NEAR TERM [Through Tonight]...
A line of storms stretches along central AL and the western FL
Panhandle. With the loss of daytime heating, instability ahead of
the line of storms has fallen greatly. The 00Z RAP analyzes MLCAPE
values to be around 250 J/kg in southeast AL and southwest GA,
with values approaching 500 J/kg along the northern Gulf waters.
Our 00Z sounding reflects these paltry values with SBCAPE of 225
J/kg and mid-level lapse rates around 5 C/km. The low level jet
that was featuring values up to around 60 kts earlier has weakened
to around 35-45 kts. RAP forecasts for 0-1 km shear have fallen to
15-20 kts, though 0-6 km shear remains fairly high at around 50
kts. Overall, these storms and the environment are looking less
and less favorable for severe thunderstorms overnight, though
there remains a marginal risk for some isolated damaging wind
gusts or a brief tornado.
Timing for the storms however, still appears to be on track, with
our western zones beginning to see showers and thunderstorms over
the next few hours, then storms dissipating as they head further
east through the night.
&&
.PREV DISCUSSION [624 PM EST]...
.SHORT TERM [Friday Through Sunday]...
The aforementioned trough will be moving through the Tennessee and
Ohio valleys through tomorrow afternoon with southerly flow
prevailing at the surface on the western edge of high pressure. A
scattering of light to moderate showers are expected on Friday as
weak low-level (300K) isentropic ascent sits over the region.
These showers should come to an end by the evening.
The main concern in the short term period will be for the
potential for severe weather over the weekend. The northern stream
longwave trough will continue to amplify and move eastward across
the central CONUS in response to a few shortwaves; most notably a
strong shortwave moving through the Four Corners region. As the
broad longwave forcing moves along the Gulf Coast, a coastal
trough/low is expected to develop; thus increasing low-level
forcing and the low-level wind field. Deep layer shear will be
plenty from the northern stream trough and very steep lapse rates
are expected to be in place as well. This will favor discrete
storm development through the day across the Tri-State region with
all modes of severe weather possible. Saturday night into Sunday,
the potent shortwave that was over the Four Corners will move into
the southern Mississippi Valley and result in even more low-level
and upper-level forcing across the region. Lapse rates will still
be quite steep, though dampening a bit. However, a decent increase
in low/deep layer shear should compensate for the slight reduction
in lapse rates. With this second wave, a more organized squall
line is expected with the primary threats being tornadoes and
damaging winds, though severe hail can`t be ruled out along the
line as well. The local area currently resides under a Slight Risk
by the SPC for Saturday, and have a 15-30% risk on Sunday. Those
type of outlooks that far into the future tend to indicate a fair
amount of confidence in severe weather unfolding across the
region. The main variable will be the timing of the waves of
severe weather and whether the first will end up interfering with
the evolution of the squall line. Folks are urged to pay close
attention to the forecast over the next 24-36 hours. For
information on expected rainfall totals, see the hydrology
discussion below.
.LONG TERM [Sunday Night Through Thursday]...
As the system moves away from the region, some showers may
linger into Monday but the chance of severe weather should begin
to diminish. Also, fast offshore winds (20-30 kt) are expected
to decrease by Monday night. Afterwards, a cooler and dry air
mass filters in and stays over the CWA for a few days allowing temps
to cool down closer to the seasonal average. On Wednesday night
into Thursday, a low pressure system moves over Michigan into
the Northeastern seaboard while its corresponding cold front moves
into our area. There is some disagreement between the global models
as to the timing of the frontal passage. The ECWMF has the front
moving through the region by the end of Thursday which is quicker
compared to the GFS. However, both bring rain to the CWA beginning
Wednesday night.
.AVIATION [Through 00Z Saturday]...
Conditions would once again be primed for widespread fog and low
cigs overnight, but the consensus of NWP models are in good
agreement in an area of SHRA/TSRA moving east across the region
tonight. This convection will "turn over" the PBL and scour out
any dense fog. KDHN and KECP will have rain between 04Z and 08Z,
followed by KTLH and KABY between 07Z and 11Z, with a weakening
area of rain reaching KVLD by daybreak. However, between 03Z and
08Z there will be enough of a window of quiet weather for LIFR
Vis/cigs to develop at KTLH and KVLD, before the convection
dissipates the fog. Low cigs (generally below 1k ft) are likely at
all sites Friday morning, followed by VFR cigs by late morning.
.MARINE...
Winds will begin to ramp up to Advisory levels late Friday night
ahead of a strong low pressure system. Advisory levels will
prevail through early next week, with Gale force gusts and
possibly sustained winds Sunday night through Monday. Seas could
climb as high as 15 feet well offshore by Monday afternoon.
.FIRE WEATHER...
No concerns.
.HYDROLOGY...
Beginning tonight, 2 to 4 inches of rain are expected to fall
across the Tri-State region through Sunday night. Isolated amounts
around 6 inches will be possible as well. These amounts will most
likely fall over a long enough period that flash flooding wont be
a concern. While rises are naturally expected on area rivers, with
widespread average amounts probably wont force area rivers into
flood stage. Should the locally higher amounts fall over
Kinchafoonee Creek or the Choctawhatchee River minor flooding
could be possible there.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 62 76 66 70 65 / 70 50 40 90 80
Panama City 64 73 68 72 66 / 80 50 50 90 80
Dothan 61 75 64 72 62 / 100 40 60 90 80
Albany 60 76 65 72 63 / 70 40 50 90 80
Valdosta 60 76 66 71 64 / 50 40 30 90 80
Cross City 59 75 65 72 65 / 40 40 20 70 80
Apalachicola 65 73 67 71 66 / 70 50 50 90 80
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk until 11 PM CST this evening for South
Walton.
GA...None.
AL...None.
GM...None.
&&
$$
NEAR TERM...Moore
SHORT TERM...Harrigan
LONG TERM...Harrigan/Chaney
AVIATION...Fournier
MARINE...Harrigan
FIRE WEATHER...Fournier
HYDROLOGY...Harrigan