Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/14/18
Area Forecast Discussion
National Weather Service Wakefield VA
948 PM EDT Tue Mar 13 2018
Strong low pressure will remain well off the New England coast
tonight and Wednesday as high pressure builds from the Plains
states across the deep south through Thursday.
.NEAR TERM /THROUGH WEDNESDAY/...
The latest wv imagery indicates a powerful storm system well
off the coast of srn New England, with 2 centers of upper level
low pressure, one over the Great Lakes and the other offshore
near the sfc low. These two upper level lows are progged to
phase into a single low tonight into Wed.
Light WNW flow this evening with temperatures in the mid 30s to
low 40s under a partly cloudy to mostly clear sky. The next
upper level shortwave (currently dropping SE across IL/IN),
rapidly moves farther SE to the lower OH Valley between 03-06Z,
and then into the Carolinas by ~12Z/Wed morning. Expect clouds
to increase over the local area after midnight, with skies
becoming mostly cloudy prior to daybreak on Wed. GFS continues
to be most aggressive regarding potential for a quick burst of
accumulating snow over far southern VA and NE NC, while the
NAM/ECMWF support the clouds and probably some flurries or brief
snow showers but little to no accumulation. Genly siding with
the drier scenario of the NAM/ECMWF at this time (which is
supported by HRRR trends), given what will initially be a dry
low level airmass and only a few hrs worth of favorable lift
through the dGZ. However, did bumps PoPs up to 30-40% for snow
showers and a light dusting will be possible. Otherwise, partial
clearing/drier air filters back in rather quickly from
12-15Z/Wed. Remaining quite chilly for mid-March with highs
only ranging through the 40s (about 15 degrees below avg).
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Clearing out behind the departing shortwave Wed night with lows
in the mid 20s to lower 30s. Mostly sunny to partly cloudy on
Thursday, and turning a little warmer as surface high pressure
builds across the eastern Gulf coast into the Carolinas,
allowing for a WSW low level flow and deep mixing. Highs will be
close to 60 F across south central VA and interior NE NC, with
lower 50s on the eastern shore. Mostly clear Thu night with
lows mainly in the 30s. Upper trough centered over eastern
Canada amplifies a bit on Fri with sfc high pressure building
ESE from the Great Lakes into the mid-Atlc. Partly-mostly sunny
but turning cooler with highs in the 40s north to the mid 50s
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Overall pattern will continue to be rather progressive during
the extended period, with a couple of low pressure areas
moving into and acrs the Mid Atlc region bringing chances for
pcpn. The first low will be a weaker system Sat aftn thru Sun,
with slght chc to sml chc PoPs acrs mainly the srn half of the
region. The second low looks like a stronger/possibly more
significant system for Mon night into Tue night. At this time,
temps look to be warm enough for just rain everywhere thru most
of the event, but could end as some snow, as the system
intensifies off the Mid Atlc coast.
Highs will range fm the upper 40s to lower 50s Sat, ranging thru
the 50s Sun, ranging thru the 50s to lower 60s Mon, and ranging
fm the lower 40s extrm NNW, to the mid to upper 50s extrm SE VA
and NE NC. Lows will range fm the mid 20s to lower 30s Fri
night, in the mid 30s to near 40 Sat night, in the mid 30s to
lower 40s Sun night, and ranging fm the mid 30s to mid 40s Mon
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Low pressure remains off the New England coast as of 00z with
high pressure centered well W of the region over the Plains
states. VFR conditions prevail through this evening at all
terminals with a WNW wind diminishing to 5-10kt. A fast
moving/weak system is expected to push across NC overnight and
move off the coast early Wed. Potential for some flurries or
possibly even a brief snow shower at KECG/KORF. MVFR flight
restrictions most likely at KECG, from about 09-13Z or so.
Otherwise, another round of a gusty WNW wind is expected
Wednesday with wind speeds of 10-15kt and gusts to 20-25kt. A
period of bkn cigs ~8kft are expected Wednesday aftn.
VFR/partly cloudy and breezy/windy with a gusty W wind once
again during the day Thursday. Dry and breezy/windy Friday with
the wind shifting to NW behind a cold front. High pressure
briefly builds into the are Friday night with a quick moving
system bringing a minimal chc of showers Saturday. High pressure
builds N of the region Sunday.
Conditions are slowly improving across the area waters as the strong
powerful storm system is now moved into New England and the Canadian
Maritimes. The northwest flow is expected to continue for the next
3 days but there will be some ebb and flow with the winds during
that period. A couple weak low pressure systems rotating around the
main area of low pressure to the north will impact the region on
Wednesday and again on Thursday. In advance of each of these waves,
expect the winds to relax some and drop below SCA levels. But in
the coastal waters, the seas will remain above 5 FT for most of the
time into Friday so SCA flags will likely be needed into Friday. So
for tonight, will see a waning of the winds in advance this first
area of low pressure. So will allow the SCA flags on the Bay, area
rivers and Currituck sound come down either with this advisory or
later this evening. But they will remain up with the seas on the
Once this wave of low pressure passes the area Wednesday morning,
will see the NW flow increase again to 15 to 25 kt making SCA flags
necessary for a short period of time Wed afternoon into Wed night.
Conditions will again relax again before another wave slides across
late on Thursday, again allowing the NW flow to briefly increase
back to SCA levels into Friday morning, before high pressure finally
builds into the area and allow for more tranquil conditions For
Friday and Saturday. A weak wave of low pressure may impact the
region on Sunday, but with westerly flow and little cold air around,
should be little impact on the waters.
MARINE...Small Craft Advisory until 10 PM EDT this evening for ANZ634.
Small Craft Advisory until 4 PM EDT Wednesday for ANZ650-652-
Area Forecast Discussion...Updated
National Weather Service Billings MT
835 PM MDT Tue Mar 13 2018
Upper ridge and dry airmass continued over the forecast area this
evening per water vapor imagery. Chances for overnight and early
morning fog will be confined to the Yellowstone River Valley
around KMLS where humidities will be high. The HRRR hinted at
possible fog in this area as well. Warm advection will bring 850
mb temperatures to +8 degrees C by 12Z Wednesday. These
temperatures will be higher than they were back at 12Z this
morning, and surface temperatures were running higher than this
time last night. Dewpoints were in the 20s this evening. The above
factors supported higher min temperatures than what occurred last
night, and guidance was in good agreement with the min
temperatures. Mostly clear skies will continue through the night
with just some high clouds over the SW part of the area. Only
forecast adjustment was to bring winds more in line with ADJLAV
guidance which had captured the observed easterly component well
this evening. Arthur
.SHORT TERM...valid for Wed and Thu...
The rest of the today will be quiet. There could be some more
localized fog in the east again, mainly in the river valleys.
Given that the snowpack is providing some boundary layer moisture
and then letting temperatures cool off at night cannot rule it
out. Tomorrow an initial wave energy moving through during the
afternoon bringing some snow showers to the mountains, and some
rain to the lower elevations. There will be a bit of a break
during the day Thursday before more energy works into the area,
with a deformation zone beginning to setup from Miles City west.
There is some decent QPF overnight with some areas over a quarter
of an inch. The cold air is in by the time the precip starts, so
this will likely fall as snow, but given the much warmer
temperatures to start with, it is going to be a fairly wet snow.
This will still result in 1 to 2 inches of new snowfall by Friday
.LONG TERM...valid for Fri...Sat...Sun...Mon...Tue...
Models have come into alignment on wet snow event Thursday night
through Friday. An upper trough over the western United States
kicks energy out into the midwest Thursday night. This sets up a
prolonged period of diffluence over the forecast area. Cold air
will get pulled down as a surface low deepens over Wyoming, with
850mb temperatures falling to -3c. A deep period of upslope will
develop. Have raised PoPs and snow amounts for Friday. A
significant accumulation of snow is possible with this storm
(mainly over south central Montana and Sheridan county Wyoming)
and will have to keep a close eye on this for potential
The main low moves out of the western United States and slides
into the northern Rockies Saturday night and Sunday. This could
generate another wet snow event. The impacts on this event could
be farther east than the previous one, hitting southeast Montana
harder than south central. Models were still struggling with
timing and placement of the low kicking out, so will keep PoPs
scattered for now. Confidence was growing on temperatures
remaining below normal this weekend, into early next week. TWH
Dry, high pressure aloft will dominate the weather with clear
skies and light winds. Areas of river valley fog are possible from
KBIL east, and will continue until around 18z Wednesday. Arthur
.PRELIMINARY POINT TEMP/POPS...
Wed Thu Fri Sat Sun Mon Tue
BIL 026/049 029/048 029/039 026/044 025/040 024/041 023/044
00/U 76/R 88/O 31/B 35/O 54/O 11/U
LVM 031/057 034/050 030/043 028/047 027/042 027/043 025/046
03/W 76/R 56/O 21/B 45/O 43/O 11/U
HDN 020/048 024/048 024/039 023/045 022/040 020/041 017/045
00/U 53/R 88/O 41/B 34/O 54/O 11/U
MLS 017/040 025/039 023/035 021/037 020/036 019/034 016/037
00/U 23/J 75/S 31/B 25/S 64/S 21/B
4BQ 023/047 027/049 025/038 024/044 024/037 021/038 018/042
00/U 33/W 88/O 31/B 26/S 75/S 11/B
BHK 020/042 021/037 022/033 022/038 021/036 018/033 015/037
00/U 22/J 42/S 11/B 25/S 72/S 11/B
SHR 023/053 032/052 029/041 026/046 025/039 023/041 020/044
00/U 42/R 88/O 31/B 34/O 54/O 11/U
Area Forecast Discussion
National Weather Service Caribou ME
1128 PM EDT Tue Mar 13 2018
Intense low pressure will move northeast and cross Nova Scotia
overnight then slowly north through the northern Canadian
Maritimes Wednesday night through Friday. A cold front from
northern Canada will cross the region Friday night.
.NEAR TERM /THROUGH WEDNESDAY/...
1110 PM Update...
Adjusted the hrly temps w/a bump up across eastern Washington
County as Maritime air gets wrapped into the region. Reports
from Lubec w/light rain mixing in w/the snow at 34F. The latest
run of the RAP & HRRR doing ok the warmer temps moving into
eastern Washington County. It looks like temps will stay up from
earlier predictions and decided to raise them a few degrees
overnight. Used the blend of the RAP and HRRR for progression of
heavier snow nnw overnight. It looks like NE Aroostook County
will see just on and off show. Fort Kent and Frenchville
receiving light snow. Spotter in Fort Kent reported the snow to
be very light. Steady snow w/pockets of heavy snow occurring
from north-central areas down to the coast as radar depicted.
Mid level low to lift up into the state overnight w/banding
potential shifting further n and w.
Kept headlines as they are w/the Blizzard Warning staying up for
the coast as winds still gusting to around 40 mph according to
spotter reports. Winter Storm Warnings remain up elsewhere.
Snow becoming heavy at times tonight across central and
Northern areas. Across far northeast Aroostook County, snow will
be slower to begin, do to some drier air remaining in place,
thus snow amounts will be just a bit lower here. A Blizzard
Warning remains in effect for the Downeast coast overnight,
where travel will be very difficult to impossible due to the
combination of heavy snow and gusty northeast winds. Across
interior Downeast, including the greater Bangor region, Winter
Storm Warnings remain up into through Wednesday. A Winter Storm
Warning remains up for the Central highlands and Southeast
Aroostook through midnight Wednesday. A Winter Storm Warning
remains for far Northern Aroostook through 6 am Thursday. The
low will continue to track north through the Canadian Maritimes
on Wednesday, with snow continuing through much of the day. The
snow will begin to wind down,especially across Downeast areas
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Whats left of deformation lgt snfl will cont across the N hlf of
the Rgn Wed ngt with Cntrl and Downeast areas tapering to sct sn
shwrs as the upper low conts to move slowly N from Nrn NB prov
into the Nrn Maritimes. Wntr stm wrngs have been xtnded a few
hrs longer into or thru Wed ngt due to contg steady accumulating
snfl into this pd.
Sn shwrs will then cont thru the day Thu, with warmer Sfc-BL
temps resulting in rn mixing with sn shwrs durg the aftn across
Cntrl and Downeast areas. Unsettled conditions will cont Thu ngt
into Fri as the upper low remains ovr the Nrn Can Maritimes,
with most sn shwrs over Nrn areas durg these pds. Temps will
cont mild, spcly ovrngt lows.
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
A clipper s/wv alf and associated sfc cold front from Nrn Can
will bring the region the first shot of drier low residence
arctic air in nearly 3 weeks as it crosses the Rgn Fri ngt with
isold to sct sn shwrs, colder ovrngt lows and and day tm hi
temps Sat, and with the potential of more day tm sunshine.
Another stronger clipper s/wv from Nrn Can potentially will
bring the region a better chc of sn shwrs late Sat ngt into Sun
followed by dry...colder mdt residence arctic air from Nrn Can
into the Rgn Sun ngt contg into Tue with perhaps some
modification of the air mass by Tue from milder air advcg SW
from the Nrn Can Maritimes.
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
NEAR TERM: Widespread LIFR/VLIFR conditions will persist at
KBGR/KBHB this evening in heavy snow/blowing snow, with
Northeast wind gusts to 40 kt possible, especially KBHB where
Blizzard conditions are expected. Further north, snow is
expected to overspread the rest of the terminals this evening
with IFR/LIFR conditions developing at the remaining terminals.
IFR conditions are expected to persist on Wednesday in
SHORT TO LONG TERM: IFR conditions across all TAF sites Wed ngt
in lgt snfl will gradually improve to MVFR from S to N durg the
day Thu in sn shwrs, with Downeast sites improving to VFR Thu
ngt. Conditions improve to VFR across Nrn TAF sites Fri ngt from
MVFR clgs/vsbys with remnant sn shwrs. VFR conditions then xpctd
all TAF sites Sat into Sat eve before another possible pd of
MVFR clgs/vsbys with sn shwrs occurs for msly Nrn TAF sites late
Sat ngt and Sun.
NEAR TERM: Gale Force conditions continue into early Wednesday
across all the waters. Visibility will be reduced to less than
1 NM at times tonight into Wednesday in snow.
SHORT TO LONG TERM: Strong SCA conditions Wed ngt will
gradually subside to low end SCA or below SCA thresholds
aftwrds. Kept close to WW3/NWPS wv guidance for fcst wv hts thru
these ptns of the fcst.
ME...Winter Storm Warning until 6 AM EDT Thursday for MEZ001-002.
Winter Storm Warning until midnight EDT Wednesday night for
Winter Storm Warning until 6 PM EDT Wednesday for MEZ011-
Blizzard Warning until 8 AM EDT Wednesday for MEZ029-030.
MARINE...Gale Warning until 6 PM EDT Wednesday for ANZ050>052.
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
927 PM CDT Tue Mar 13 2018
Updated for evening discussion.
Clear skies and a light wind as surface high pressure builds in
from the northwest should contribute to frost development at most
locations along with freezing temperatures in the northeast.
Forecast is on track and no changes were necessary. /22/
Prior discussion below:
Tonight through Wednesday night: Latest RAP and satellite imagery
showed a broad upper trough in the mid to upper levels of the
atmosphere, which was providing cold air advection in northerly
flow to the region. Under mostly sunny skies with some high clouds
readings were mainly in the 50s.
For tonight, expect another round of unseasonable temperatures as
a 1027 mb surface high settles over the ArkLaTex region. This
will cause light winds overnight under clear skies. Readings will
dip into the upper 20s to the middle 30s. The coolest areas will
be confined to our northeastern counties from Grenada to Kosciusko
to DeKalb, where a freeze warning is in effect. This is the area
that has the best chance of dipping below freezing for at least
several hours. Have less confidence of this happening as we
venture southwest from Meridian to Greenwood with frost expected.
Across the remainder of the forecast area, low temperatures are
expected to range from around 32 degrees to 37 degrees, with areas
of frost possible.
For Wednesday, a 1024 mb surface high will settle over the
region. Light winds and cool air advection will bring another
unseasonable day across the forecast area. Highs will range from
the middle 50s north to the lower 60s south. Minimum humidities
will dip in the lower to middle 20s, but light winds and recent
rainfall will limit fire danger issues. As we move into Wednesday
night, the 1023 mb surface high will settle over southern
Mississippi. There will be some potential for freezing
temperatures in our eastern counties for Wednesday night. So have
issued a freeze watch for that area. Lows for Wednesday night will
range from mainly the lower 30s east to the upper 30s west. Put
in patchy frost across the east. Be sure to see the latest
Hazardous Weather Outlook text and graphics, as well as Freeze
warning/watch for more details./17/
Thursday through Monday: Amplified mid level pattern at the
beginning of the period will begin breaking down moving forward as
energy rotates out of base of trough along the west coast through
the Rockies and into the western High Plains by Thursday evening.
Meanwhile, surface high pressure will remain anchored over FL with
resulting southerly flow serving to slowly moisten the lower levels.
As the storm system moves further into the Plains Thursday night
into Friday morning, increasing wind fields will rapidly initiate
isentropic ascent over exiting cool airmass resulting in showers in
the west by early Friday morning. Surface dewpoints will continue to
rapidly rise as strong warm advection continues with mid 60s
dewpoints in the ArkLaMiss Delta region by late Friday afternoon.
Negative tilt of mid level cold core trough will support good mid
level lapse rates. This coupled with 50+ knots of deep layer
shear should support severe convection during the afternoon and
evening and could linger into Saturday ahead of the approaching
frontal boundary. Have continued the slight risk for the ArkLaMiss
Delta region in the HWO.
As the mid level system ejects out to the northeast Saturday night,
trailing frontal boundary looks to hang up over southern sections
with the next system approaching from the west Sunday. Warm
advection in advance of this system will take advantage of the
leftover surface boundary to initiate more convective development in
the south by Sunday afternoon./26/
00Z TAF discussion:
VFR conds wl cont through Wednesday. /22/
.PRELIMINARY POINT TEMPS/POPS...
Jackson 33 58 33 71 / 0 0 0 0
Meridian 31 58 31 70 / 0 0 0 0
Vicksburg 34 59 35 72 / 0 0 0 0
Hattiesburg 32 62 34 71 / 0 0 0 1
Natchez 35 60 37 72 / 0 0 0 1
Greenville 32 56 38 69 / 0 0 0 0
Greenwood 31 55 37 69 / 0 0 0 0
MS...Freeze Watch from late Wednesday night through Thursday morning
Freeze Warning from 1 AM to 9 AM CDT Wednesday for MSZ026-
Area Forecast Discussion
National Weather Service Louisville KY
950 PM EDT Tue Mar 13 2018
Issued at 945 PM EDT Tue Mar 13 2018
Numerous snow showers spreading southeast through southern IN and
central KY currently, including some pockets of moderate to
briefly heavy snow. Expect increasing traffic issues from this
point forward over the next couple of hours. Areas impacted by a
heavier burst of snow could see a half inch in as little as 15
minutes. Use caution if traveling late this evening. Some areas in
the advisory area could certainly still get an inch, locally
higher. The snow will be out of here by midnight.
But as the snow showers are moving in, temperatures are dropping
quickly due to evaporational cooling. After midnight, the rest of
the night looks dry but cold. Wednesday morning lows will range from
the upper teens to mid 20s. Use caution if traveling tonight. Sudden
visibility reductions are also occurring in those heavier snow
Issued at 624 PM EDT Tue Mar 13 2018
Expanded the Winter Weather Advisory slightly to include Bullitt,
Nelson, Marion, and Casey counties. Trends in the latest hi-res
guidance have bolstered confidence we`ll see similar impacts from up
to 1 inch of snow in parts of those counties. Certainly not everyone
will get an inch of snow, due to the cellular nature of the snow
showers. But that also means folks that do see a persistent snow
shower could see locally up to 2 inches, mainly due to steep lapse
rates and higher snow ratios by 03-06z tonight. In latest storm-
total snowfall forecast, have the higher 1+ inch totals in northern
and northeast Nelson and eastern half of Marion, so the risk for
travel impacts is a bit higher in those areas.
.Short Term...(This evening through Wednesday night)
Issued at 247 PM EDT Tue Mar 13 2018
...Winter Weather Advisory This Evening/Tonight...
A batch of scattered rain/snow showers is working through the
Bluegrass region at this hour as a cold front also pushes through.
Saw snow out of this precipitation with temps in the upper 30s, but
don`t expect much in the way of accumulations given surface temps
As we move through this evening (roughly 8 PM EDT to 2 AM EDT) a
potent mid level shortwave will drop into the area, with steepening
low level lapse rates and low to mid level saturation up through
most (if not all) of the DGZ. Given the forcing, steep lapse rates,
and good saturation think we`ll see numerous snow showers slide
across southern Indiana, north central Kentucky, and into the
Bluegrass region of east central Kentucky around and after sunset
through just after Midnight. Expecting brief but intense bursts of
snow where ratios should approach 20:1. Given surface temps around
freezing, then falling below freezing as we approach Midnight, and
good rates, think we`ll see some light accumulations. The main area
of concern is along and east of a line from Salem, IN down through
Louisville, KY and over to Richmond, KY where local amounts could be
up to 1 inch. Spots that see the most persistent and intense snow
showers could pick up a quick 1 to 2".
Plan on issuing a Winter Weather Advisory to cover both the threat
of brief/intense accumulations (impact-based) and the threat of
localized amounts of approaching 2 inches. The Advisory will run
from 7 PM EDT to 5 AM EDT tomorrow morning. Will probably be leaving
some of the northern Bluegrass counties north of Lexington out of
the Advisory as best coverage/intensity should be just south.
Lexington will be included. Will also issue a Special Weather
Statement around the advisory to cover the counties that could see
around a half an inch or less of snow, but still intense bursts.
Main messaging should be to watch for rapidly deteriorating
conditions over short distances with snow bursts. Folks traveling
along I-64 along and east of Louisville should especially be
cautious, in addition to I-65 in southern Indiana down through
Louisville and I-75 between Lexington and Richmond. These types of
snow showers have been known to cause numerous accidents in the past.
Main snow showers should move out shortly after Midnight with a cold
and dry morning expected for Wednesday. After lows in the low to mid
20s, look for highs on Wednesday only struggling into the upper 30s
and low to mid 40s SW. Dry conditions continue into Wednesday night
with lows dropping around freezing to just above.
.Long Term...(Thursday through Tuesday)
Issued at 247 PM EDT Tue Mar 13 2018
Thursday - Thursday Night...
Forecast remains dry for Thursday with dry NW flow aloft over us.
However, the surface pattern will start to take on the shape of a
loosely defined col over the region, signaling a developing frontal
boundary near our SW CWA as we head into Thursday night. Will only
mention small chances of rain across our SW on Thursday night as the
front slowly becomes better defined. Highs Thursday will be around
normal for this time of year in the mid and upper 50s in most spots.
Locations along the TN border should sneak into the low 60s. Lows
Thursday night are expected to range from around 30 in our NE, to
around 40 in our SW down by the developing front.
Friday - Saturday Night...
A cutoff low will meander from the high Plains into the Mississippi
and Ohio River Valleys by late Saturday. Ahead of this feature,
precipitation is expected to increase in coverage along the stalled
frontal boundary Friday into Friday night. By Saturday morning,
surface high pressure will try to slide into the region from south
central Canada, creating an overrunning scenario. Given the warm nose
aided by a 20-30 knot low level jet, could see a brief freezing rain
sounding until temps surge above freezing later Saturday morning.
Will be something to watch in the coming days. The most widespread
precipitation occurs from W to E on Saturday as the closed low opens
up over our area and pushed ESE. We should then dry out Saturday
evening as the system moves off.
Highs Friday are only expected to be in the mid 40s to low 50s north
of the boundary. Friday night lows range from the upper 20s NE to
the upper 30s SW. Highs Saturday do find their way to near 50 in the
NE and near 60 in SW as the warm front moves into the area. Saturday
night lows drop into the 30s.
Sunday - Sunday Night...
Low amplitude upper ridging progresses through the area to end the
weekend, bringing dry conditions and temps likely just above normal.
Look for highs in the upper 50s and low 60s Sunday. Sunday night
lows drop into the low and mid 40s.
Monday - Tuesday...
The beginning of the new week looks to be another wet stretch as
models generally agree on a developing large storm system in the
region. We`ll have to keep eyes on solutions as the potential for
another phased storm isn`t out of the question. Early indications
are that this storm system would be on the warmer side, to the point
that we would have to worry more about thunderstorms than frozen
precipitation (at least on the front side of the system). Lots to
play out over the coming days.
.Aviation...(00Z TAF Issuance)
Issued at 615 PM EDT Tue Mar 13 2018
Well...the brisk west winds continue to exceed guidance with strong
caa mixing occurring and have raised the wind speeds gust through
02z. Obs at top of the hour showing several obs gusting into the 20-
25 mph range and SDF gusting to 27 mph.
Despite a break in the action the cold sc/cu is coming into CWA with
vort lobe rotating around Great lakes the 01-06z timeframe. Latest
HRRR showing the snow showers expanding in coverage from with
scattered to occasional snow showers at SDF and LEX roughly in the
01-05 UTC time period. Lapse rates are steep very steep indeed which
will bring visibilities down in the moderate to heavy snow showers.
These are not true traditional snow squall due to wind speeds <30
Conditions should vary from VFR to low MVFR cigs depending on the
intensity of individual snow showers. I expect vsbys in Snow
showers to be 3-5 miles BUT there will be some 1/2 to 1 mile quick 5
Much of this activity should stay E of HNB, but still scattered
flurries or light snow showers could affect HNB. Activity will stay
N and E of BWG with VFR conditions there.
Clouds begin to thin or clear out overnight and especially Wednesday
morning with VFR conditions. Surface winds eventually back to a
westerly direction during the day around 10 kts.
IN...Winter Weather Advisory until 5 AM EDT Wednesday for INZ077>079-
KY...Winter Weather Advisory until 5 AM EDT Wednesday for KYZ029>035-
Area Forecast Discussion
National Weather Service Paducah KY
924 PM CDT Tue Mar 13 2018
Issued at 924 PM CDT Tue Mar 13 2018
Remaining light precipitation should exit the northeastern section
of the west Kentucky Pennyrile region within the next hour. Dry
and cold (below normal) temperatures should prevail for the rest
UPDATE Issued at 601 PM CDT Tue Mar 13 2018
Updated Aviation Discussion for 00Z TAF Issuance
UPDATE Issued at 545 PM CDT Tue Mar 13 2018
Minor sensible weather adjustments made for tonight and tomorrow.
Moved the precipitation potential a little further east from 7 to
9 pm CDT across the eastern sections of southwest Indiana and into
northwest Kentucky (generally east of a Princeton Indiana to
Calhoun Kentucky line). Kept the majority of the precipitation a a
trace mix of rain and snow. As the sub-cloud layer cools this
evening, anticipate some flurries before ending altogether.
Blended current forecast with the 3km HRR, SREF, 1 hour resolution
of the 20 km GFS, and 13km RAP guidance to reflect subtle changes
tonight into Wednesday.
.SHORT TERM...(Tonight through Thursday night)
Issued at 1243 PM CDT Tue Mar 13 2018
Upper level low pressure core associated with Noreaster
currently headed through New England will bring nwly flow to much
of the region this afternoon through tonight. Within this flow
may bring some 4kft cloud decks to mainly sw IN/nw KY, but any
precip should remain east of our forecast area. Not as much
cyclonic flow expected Wednesday, but still may be some afternoon
cumulus around/east of the MS River during the afternoon.
Main weather feature to take over the remainder of the short term
will be the development of a blocking mid/upper level Omega high
pressure system over the Continental Divide and and into the
western Plains by Thursday. This should allow for plenty of
sunshine and warming west to southwest winds, with temps finally
getting back above normal into the upper 50s to mid 60s. Should ne
a fairly nice afternoon for mid March.
.LONG TERM...(Friday through Tuesday)
Issued at 241 PM CDT Tue Mar 13 2018
The deterministic medium range models were in better agreement
currently than 24 hours ago. The general consensus is that there
will be two separate closed lows ejecting from persistent eastern
Pacific/CA shortwave energy, moving across the PAH forecast area in
the extended forecast period.
The forecast period will start out with a good signal for the
formation of a west-east surface boundary across the PAH forecast
area, ahead of the first impulse. Rain showers appear likely early
Fri as the front begins to push southward. At the same time, low
level moist fetch should be enabled, and this moisture will ride up
over the shallow wedge of cooler air that will be sustained by
easterly surface winds. This should result in the best QPF through
at least the morning hours Fri.
Isolated lightning strikes might occur near the AR/TN state lines
mainly Fri night under enhanced mid level positive vorticity
advection. As the impulse continues eastward, drier air should
eventually begin to move into our region from the southwest later,
limiting pcpn, but the timing of this is a bit uncertain (Fri
afternoon? Fri night?). This was dependent on the progged position of
the first tight, nearly stacked low pressure system moving out of
the central Plains (the CMC seemed to have a more unlikely, more
northerly path). There are signs that the low may begin to weaken as
it moves by just to the north of our region, thus the QPF should be
light for us into Sat, with conditions stable enough to
probably preclude thunder.
The latter half of the weekend appears dry at this time under quasi-
zonal flow aloft. The second impulse will approach our region from
the west Sun night, trailing a surface pressure trof/cold front
south of it. At this time, fropa is forecast to occur Mon afternoon
or Mon night. PoPs remain in the chance category for Tue (Day 7) due
to the possibility of the mid/upper low lingering in our region.
The trend lately has been toward cooler temps, staying in the
general vicinity of seasonable numbers.
Issued at 601 PM CDT Tue Mar 13 2018
Diurnally enhanced cu field in northeast (KEVV/KOWB) should
dissipate with loss of fuel, scattering mid (VFR) bases by mid
evening. Gusts may maintain until almost then, and then should
diminish as skies clear all sites. Nwlys will return tmrw, not as
gusty, then back during the day, with perhaps some scattered high
clouds at times.
Area Forecast Discussion
National Weather Service Sacramento CA
300 PM PDT Tue Mar 13 2018
Series of Pacific storms will move through this week bringing
periods of rain and mountain snow, heavy at times, with gusty
wind and thunderstorms.
Pacific frontal system moving into the eastern foothills and
mountains this afternoon. Lines of stronger returns are being
observed on 88D Mosaic with embedded thunderstorms extending from
the West Slopes of the Northern Sierra Nevada through the
Motherlode, into the San Joaquin Valley. HRRR showing heavier
precip continuing in the Motherlode and Sierra throughout most of
the night. Snow level radar indicating snow level above 8000 feet
at Colfax but is lowering at Chico and Oroville to 5700 feet as
colder air is ushered in behind front. Expect snow levels to drop
below pass levels this evening, then continue to lower overnight
to 3500 to 4500 feet by Wednesday morning. Periods of heavy snow
and strong wind expected in the Sierra overnight.
Showers continue over Interior NorCal Wednesday as upper level
trough moves through. Periods of moderate snow showers expected in
the Sierra Wednesday. Models showing significant amount of CAPE
at the lower elevations tomorrow afternoon to include
thunderstorms in the forecast. Stronger storms likely to produce
Upper trough shifts through Wednesday night with showers
decreasing overnight into early Thursday. Models then show
channeled vort moving into the area Thursday afternoon into night.
Snow expected to ramp up in the mountains Thursday afternoon into
night. Main upper low digs along the NW CA coast Friday with
additional waves rotating into the area. Showers and thunderstorms
likely Friday with continued periods of heavy snow in the
mountains. Snow levels continue around 3000 to 4000 feet, but
could be down to 2500 feet in heavier convection. Have added
Winter Storm Watch for this next system. Snow advisories may also
be needed for the Coastal and Shasta mountains late Thursday and
.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)
Precipitation could continue across interior NorCal on Saturday
as a weak upper disturbance pushes through the area. Drier weather
will return Sunday into early Monday as ridging attempts to
Active pattern returns early next week as an upper level system
drops down into the Eastern Pacific and move into the West Coast.
However, there are model differences in timing and evolution of
this system. The GFS begins to spread precipitation as early as
Monday afternoon, while the ECMWF holds off until Monday evening.
In addition, the GFS digs the upper system southward and ends
precipitation faster than the ECMWF. Regardless, confidence is
high that the unsettled weather pattern will continue through at
least the middle of next week.
Storm system will continue to bring MVFR/IFR conditions across
Valley TAF sites, and IFR/LIFR conditions over the mountains.
South winds 10-20 kt with gusts to 30 kt across the Valley will
continue through 01z Wednesday.
Winter Storm Warning until 5 PM PDT Wednesday for West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.
Winter Storm Watch from Thursday afternoon through Friday
evening for Western Plumas County/Lassen Park.
Winter Storm Watch from Thursday afternoon through late Friday
night for West Slope Northern Sierra Nevada.
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Wednesday)
Issued at 340 PM CDT Tue Mar 13 2018
Little sensible weather is forecast for tonight and tomorrow with
the biggest challenges of the forecast revolving around
A strong upper level omega block was anchored over the Rockies
early this afternoon in water vapor imagery with a 1033 mb surface
high pressure cell building southward into the Central Plains.
This setup will bring clear skies for tonight as the high moves
overhead. A dry tongue was associated with this ridge, with
dewpoints falling into the single digits above/below 0 F from
Salina northward into Central Nebraska. Leveraged the recent HRRR
runs to model this wedge of dry air for tonight and early tomorrow
as most guidance was far too moist. The combination of clear
skies, light winds, the very dry air, and little soil moisture
will cause temperatures to plummet tonight into the 20s and even
upper teens. Went close to the MET guidance for lows, with a
similar setup last week resulting in lows that were 5+ degrees
cooler than most solutions.
Wednesday will feature clear skies and increasing SW winds as the
surface high departs and the surface pressure gradient over the
state increases. There is some concern that the wedge of dry air
may linger through part of the day before increasing moisture
overspreads the region. Warmer downslope air overspreads the
region on Wednesday, allowing highs to surge into the upper 60s to
low 70s in most locations. The combination of increasing/gusty
winds and low RH values will present a widespread very high fire
danger day throughout NE Kansas.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 340 PM CDT Tue Mar 13 2018
The chance of precipitation creeps back into the forecast for late
in the week with temperatures at or above normal--the exception
possibly being Friday.
Thursday will be a near carbon-copy of Wednesday temperature-wise
with H850 temps in the +8 to +10 C range and surface temps in the
70s. Some locations in central Kansas could push the upper 70s
closer to the H850 thermal ridge. The surface flow turns slightly
more to the south, advecting increasing amounts of moisture into
the region and reducing the fire weather risk. A baroclinic zone
develops over the state during the course of the day as lee
cyclogenesis takes place over the Front Range in response to an
approaching H500 vort max. Winds on Thu night into Friday look to
remain on the strong side given the 20-40 ubar/km pressure
gradient over the region. NAM/GFS forecast soundings show a
shallow mixed BL throughout the night with winds of 15 to 25 kts
throughout this layer.
Increasing 295-305 K isentropic upglide over the effective lower
tropospheric warm front will fuel elevated showers and possibly a
few thunderstorms over NE Kansas overnight Thu/early Fri morning.
However, forecast soundings and MUCAPE plots are rather unimpressive
and only kept slight chance of thunder mentioned in the forecast.
Recent runs of the EC/GFS have come into some agreement in the
position of the warm front for Friday--bisecting the CWA from NW
to SE. Highs therefore on Friday could vary greatly between the
upper 40s on the KS/NE border to the upper 60s by Emporia. The dry
slot punches northward over the CWA by midday Friday, likely
bringing an end to any widespread precip. A light drizzle is
possible north of the warm front Friday night into Saturday
morning before the low pulls out. While it is quite a ways out to
nail down any top-down forecast parameters, the current synoptic
setup would support a small window of freezing drizzle near the
KS/NE border early Saturday morning. Did mention this possibility
in the grids but it is of very low confidence at the present time.
After the departure of this system on Saturday morning, an active
zonal flow pattern will set up for the weekend and early next week.
However, confidence in the timing and locations of these late period
systems is low. The next decent chance of precip after Sat morning
possibly arrives Sun night.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 545 PM CDT Tue Mar 13 2018
VFR conditions are forecast to persist through the period with
light winds overnight becoming southwest with some gusts after 15Z
Issued at 340 PM CDT Tue Mar 13 2018
Northerly winds today lessen tonight and then switch to the SW by
sunrise on Wednesday. These winds increase to between 10 and 15
mph with gusts near 25 mph at times on Wednesday. Dry air
currently in place over the state slowly moistens during the day
on Wednesday, but widespread very high fire danger conditions are
still forecast during the day. Currently forecast RH/wind
conditions are straddling the extreme fire danger category for
Wednesday and there is a chance that, should conditions
deteriorate any further, that a Red Flag Warning may be issued.
For Thursday, southerly winds lessen slightly and RH values will
also be somewhat higher, limiting the areal extent of the very
high fire danger threat to along and west of the Flint Hills in