Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/14/17
Area Forecast Discussion
National Weather Service Boise ID
845 PM MDT Mon Mar 13 2017
.DISCUSSION...The 00Z run of the NAM model is a little dryer than
the previous run tomorrow for areas north of Baker City and
McCall. In addition, the latest runs of the HRRR keeps the area
near Baker City and McCall dry during the day as well. So...we
will trim pops back a bit in those areas. Otherwise the forecast
remains on track for warm and dry weather tomorrow. Temperatures
will be 15 to 20 degrees above normal. Skies will be partly cloudy
with with increasing and thickening cirrus clouds later in the
.AVIATION...VFR with scattered-broken high level clouds, mainly
northeast of KBNO-KBOI-KJER. Surface winds: Variable 10 kts or less.
Winds aloft at 10k ft MSL: West 10 to 20 kts.
SHORT TERM...Tonight through Wednesday...Upper level high pressure
continues to bring warmer air into the region. Tuesday will be
the warmest day of the year so far, with temperatures in the upper
60s to low 70s in the Snake Plain. Temperatures will be around 15
degrees above normal, although still below record highs (which is
75F for Boise on Tuesday). A chance of rain showers is possible
Tuesday morning as a system passes by to the north, mainly over
the higher terrain north of a line from Baker to Stanley.
Slightly cooler temperatures expected on Wednesday as clouds
increase and rain showers move into the region from the west. Snow
levels expected to be around 7500-8000ft with the onset of the
precipitation. A slight chance of thunderstorms may need to be
added to the forecast on Wednesday afternoon across southeast
Oregon with weak instability across the eastern Oregon mountains.
LONG TERM...Wednesday night through Saturday...A shortwave
trough will move through the region Wednesday night, brining a round
of showers to most folks, with the heaviest precip in the mountains
as usual. A cold front will send highs lower, but we will still be
around 5 degrees above normal for Thursday`s high. Showers will move
out Thu afternoon, and Thu night will be dry and cool. Friday and
Friday night will be relatively dry and mild, with a chance of
showers mainly in the north. Southwest flow will continue on
Saturday, and temps will warm up further. High are forecast from 65
to 70 in the lower elevations, with 50s in the mountains.
Saturday night through Monday...Model agreement and run
to run consistency are unusually good for the last couple of days of
the long term period, so confidence in timing is above average. A
shortwave trough embedded in southwest flow aloft will cross eastern
Oregon and southwest Idaho Saturday night and Sunday, with most of
its energy staying north of our area. We can expect scattered to
numerous showers over our northern mountains, with isolated to
scattered showers further south. Snow levels will be between 6000
and 7000 feet. On Monday a weak upper level ridge will build over
the Intermountain Region, ahead of the next Pacific weather system.
Temperatures will be around 5 degrees above normal.
PREV SHORT TERM...KA
PREV LONG TERM....SP/JT
Area Forecast Discussion...Updated
National Weather Service Billings MT
815 PM MDT Mon Mar 13 2017
Upper ridge building in from the west was creating mid level warm
advection, which was generating quite a bit of clouds across the
area. Temperatures have fallen quickly this evening despite the
cloud cover and needed to make adjustments downward on low
temperatures as some current readings were already exceeding
forecast values. Warm advection will spread to the lower levels
and temperatures should level off shortly. Raised PoPs into
central zones this evening with some weak echos showing up on KBLX
radar. One last thing, added patchy fog to parts of the
southeast. HRRR was indicting the possibility and MET guidance was
also showing that as well late tonight. TWH
.SHORT TERM...valid for Tue and Wed...
Most of the activity is out of the area, although some light
snowfall is lingering in Carter and Fallon counties. The jet that
has been producing the snow will move out into the Dakotas
tonight. Behind it, another strong jet will move across the area
late tonight and into tomorrow. This will bring another chance
snow overnight. Going into tomorrow temperatures will warmup into
the 50s and 60s across southern Montana. This will see snow change
over to rain. This will result any any light accumulations of snow
However as temperatures cool overnight there will be a chance for
freezing rain across mainly Carter and Fallon counties tomorrow
night. Models continue to show that there is some chance that with
some evaporative cooling this could be short lived. The models
have been showing this signal fairly consistently so have
continued some areas in the east.
Going into Wednesday things will be dry, and temperatures will
continue to be warmer than normal. Wednesday night the ridge will
begin to break down into more of a zonal flow. Reimer
.LONG TERM...valid for Thu...Fri...Sat...Sun...Mon...
Message remains consistent for the extended forecast period.
Temperatures will be generally above normal throughout the
period...with a progressive weather pattern bringing periodic
precip chances across the region.
A Pacific trough will cross the region through the day
Thursday/Thursday night. This trough should bring a few showers to
the region...but forcing is weak...so precipitation amounts should
Ridging builds in for Thursday night through Saturday, bringing
dry weather. Ridge begins to break down on Sunday as southwest
flow aloft brings in disturbances and Pacific moisture over the
region, resulting in scattered showers Sunday and Monday. These
disturbances look weak and fast-moving, so precipitation amounts
again should be light.
High temperatures on Thursday should be about 10 degrees cooler
than Wednesday`s readings as low-level flow turns northwesterly
and brings in cooler air. Friday`s high temps should generally be
around Thursday`s readings. Some downsloping develops on
Saturday, which should bring high temperatures to the 60s across
the lower elevations. A cold front looks to drop southward on
Sunday, bringing a cooling trend to the temperatures for later
Sunday into Monday. RMS/Reimer
VFR should prevail tonight over much of south central MT and north
central WY. Low clouds and fog should develop over southeastern
MT including KMLS after 06Z. Scattered showers with MVFR are
possible near KBIL and KLVM by early morning. Walsh/RMS
.PRELIMINARY POINT TEMP/POPS...
Tue Wed Thu Fri Sat Sun Mon
BIL 032/051 037/068 043/059 033/056 038/066 044/062 035/050
25/W 10/E 14/W 20/B 11/B 12/W 22/W
LVM 042/054 038/065 041/055 030/055 037/065 043/059 034/051
45/W 20/N 24/W 21/B 11/N 32/W 22/W
HDN 030/047 032/067 038/059 030/055 032/065 039/062 032/051
24/W 20/B 15/W 40/B 01/B 12/W 22/W
MLS 021/037 033/056 038/056 031/053 032/062 038/056 032/047
13/W 30/B 13/W 20/U 01/B 12/W 22/W
4BQ 026/046 032/067 037/060 030/054 031/068 039/062 033/049
14/W 30/B 05/W 40/B 01/B 12/W 22/W
BHK 015/034 029/053 034/055 028/049 029/060 036/056 029/044
22/J 31/B 14/W 20/U 00/B 11/B 21/B
SHR 032/051 035/068 040/061 031/055 033/069 043/063 035/052
22/W 10/B 05/W 51/B 00/B 02/W 22/W
Area Forecast Discussion
National Weather Service State College PA
1131 PM EDT Mon Mar 13 2017
A major winter storm will bring heavy snow to central
Pennsylvania tonight through most of Tuesday. The eastern half
or more of the commonwealth will see over 12 inches of snow.
After a period of lake effect snow during mid-week and brief
high pressure at the end of the week, an unsettled pattern will
.NEAR TERM /UNTIL 8 AM TUESDAY MORNING/...
* Major to even crippling storm possible for the eastern half
of the state.
Very little change made to the onset timing of the snow, period
of heaviest snowfall, and forecast snowfall amounts.
Region radar mosaic loop shows the expansive shield of light
snow to our west, combining with the quickly northward advancing
light to moderate snow shield moving into our SE zones attm.
Phasing of the potent up trough diving SE from the Upper
Midwest and Western Glakes region, and the lead shortwave
lifting NE up and over the stationary coastal front will cause
rapid phasing of the features aloft and intensification
overnight of the current elongated sfc lows from the Carolina
coast to the NE GOMEX.
EC and NAM much wetter than the GFS. The high QPF seems on-
order in the east where the greatest 8H easterly wind anomalies
advect copious moisture up and over the sharpening and steep
850-700 mb front.
A gradually pivoting belt of enhanced 850-700mb FGEN forcing
and associated band of enhanced adiabatic cooling from the
strong uvvel is see late tonight through the late morning hours
near the I-83, 1-81 corridor from York, Harrisburg and Lebanon,
northeast to Pottsville and Hazleton where the NCAR ensemble
excessive snowfall probability hourly loop indicates a high
probability of snowfall rates easily in the 1.5-2 inch per hour
There is increasing concern that we may have to tighten up the
east/west snowfall gradient between the Susq Valley and Central
Mtns, based on the NCAR data and after looking at the latest
few runs of the HRRR (which shows LEQ QPF of 2-3 inches in a
nearly stationary 30-40NM wide, intense and slowly pivoting FGEN
snowband close to the I-83/I-81 corridor between 06Z-12Z
Tuesday). Snowfall rates as high as 3-4 inches a few hours,
along with some flashes of lightning/thunder are possible should
this snowband come to fruition as some higher res models
Previous late afternoon discussion...
Satellite images showing a rapidly advancing shield of low
clouds moving northward from Central VA. Deepest moisture is
still a few hours away, with all models now very well-agreed on
timing. Sfc low will deepen rapidly tonight, but even more- so
on Tuesday as it passes our latitude. Snow rates will become
1-2"/hour in the heaviest mesoscale bands. Thundersnow is also
possible in those bands. Where and when these bands set up and
how/when they pivot is the major factor of where the totals will
be highest. These details are not easily seen even at this
close range. HRRR and RAP will be important tools in this
.SHORT TERM /8 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
The challenge with this forecast lies in where to make the
really deep (>12") snow taper off. Placement of highest QPF is
generally E of State College by all models, but SLRs will be
greater/fluffier in the W. The sfc air is dry and winds
generally 10 mph sustained. The wind will certainly be stronger
closer to the coast and in eastern PA. However, no guidance
gives any of Central PA sustained winds of blizzard criteria
(frequent >=35mph gusts). Blizzard conditions are very rare
this far inland.
The biggest threat lies in the timing of the heaviest of the
snow. 1" and 2"/hr rates may be common between 3 and 10 AM. This
will create an extreme amount of trouble for travel.
Deformation snowfall will persist into Tuesday afternoon with
additional light accumulations in most areas. Far eastern areas
will continue to significantly add to their totals while
remaining on the western periphery of the heaviest snowfall
associated with the offshore coastal low.
The western counties will have the wind go northwesterly and
additional snow will come first from perhaps a lingering
deformation band and then some lake effect. The winds Tuesday
night will be stronger than during the rest of the storm.
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
A reinforcing surge of cold air will follow behind the big storm
with snow showers and a breezy NW wind Wed-Thu. Temperatures
well below average Wed behind the system with below average
temps continuing through the week.
Another wave drops across the region Fri into Sat with light
snow (rain/snow south) likely. Additional scattered snow showers
will impact the NW mtns through the weekend as breezy and chilly
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
An intensifying storm moving up the east coast will spread snow
across the entire region overnight. The heaviest snow, with
visibilities between 1/2SM to 1/4SM, will fall over the the
eastern half of the state overnight through late Tuesday
morning. Across the western half of the state, expect lighter
snow, but still IFR conditions.
Improving conditions are expected Tuesday afternoon and
evening across the eastern half of the state, as the storm
pulls away. However, lake-enhanced upslope snow should continue
to produce IFR conditions at BFD and JST through Tuesday
Winds will pick up on Tuesday PM, as the storm pulls away from
the region. Bufkit soundings indicate there will be frequent
gusts of 20-25kts with occasional gusts of around 30kts,
especially at JST/AOO/LNS.
Wed...Mainly VFR, with residual MVFR conditions in snow
showers, especially in the west and north. Windy.
Thu...Mainly VFR, with residual MVFR conditions in snow
showers in the west and north. Winds slowly diminishing.
Sat...Chance of rain and snow showers.
Winter Storm Warning until 10 PM EDT Tuesday for PAZ006-011-
Winter Storm Warning until 8 AM EDT Wednesday for PAZ004-005-
Area Forecast Discussion
National Weather Service Quad Cities IA IL
951 PM CDT Mon Mar 13 2017
Issued at 949 PM CDT Mon Mar 13 2017
Radar, surface observations, and trends from the HRRR confirm that
the snow band will continue for another few hours, and I have
upped pops to categorical, and increased amounts to a half inch
from the Quad Cities eastward. This minor event will be over
around 2 AM.
UPDATE Issued at 609 PM CDT Mon Mar 13 2017
Visibilities under 2 miles in many locations, and a few under 1
mile show that there are more than flurries headed toward our
eastern 1/2 of the CWA this evening, and have put in snow showers
into the forecast.
Issued at 233 PM CDT Mon Mar 13 2017
Analysis at 2 PM CDT shows slow clearing with cold Canadian high
pressure moving into the region as storm has moved to the southeast.
Local tools all support clearing next 12-18 hours with main issue
the speed of clearing. Amount of subsidence per local nowcast tools
all suggest most models are likely too slow on this clearing. Upstream
energy shows after Wednesday a return to zonal flow and near normal
temperatures will limited moisture into next weekend.
.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 233 PM CDT Mon Mar 13 2017
Short term forecast confidence assessment...poor or below average. Timing
of clearing could be off by 6 hours or more with main risk is clearing
is too slow by late evening into the overnight hours most areas. If
this occurs then mins may be too mild by 3 or more degrees many/most
locations. Areas that will have at least 2 inches of new snow could
be too mild by 5 or more degrees. This is the main issue for evening
shift to monitor and update as needed.
Tonight...Clearing to slowly occur with northerly winds of 5 to 15 MPH.
All or almost all the area should be mostly clear by sunrise with main
risk clearing is too slow. Forecast mins of upper single digits to around
20F may be off by 3 plus degrees. Local techniques suggest with light
winds and clear skies for several hours overnight in 2 plus inch snow
locations suggest lows may be 5 degrees too mild.
Tuesday...mostly sunny with some cold air strato-cumulus mid day to
mid afternoon hours suggested. North to northeast winds of 5 to 15
MPH. Highs should be with mid March sunshine still reaching the upper
20s north and northeast to well into the lower 30s south sections.
.LONG TERM...(Tuesday Night through Monday)
ISSUED AT 233 PM CDT Mon Mar 13 2017
Quiet and cold conditions will be seen across the area Tuesday night
as high pressure settles over the Midwest. The near calm winds and
relatively fresh snow has the potential of producing near record
lows. Refer to the climate section for specific numbers.
Quiet and dry conditions will continue Wednesday and Wednesday night
as high pressure moves into the Ohio Valley. Temperatures will
average below normal.
On Thursday moisture will flow back into the area. Thermal profiles
show relatively cold, dry air initially over the area as the
increased moisture aloft and forcing move into the area. Thus
precipitation should initially start out as snow and slowly change
over to all rain during the afternoon. Any new snow accumulation
Thursday morning will melt as the snow changes over to all rain.
Thursday night on...
A weak storm system will move through the area Thursday night/Friday
morning. How much moisture will be available for the system is
somewhat in question. However, the rain will mix with and change
back over to all snow Thursday night before changing back to all
rain on Friday. The model consensus has chance pops Thursday night
and chance to likely pops on Friday.
Friday night through Sunday the model consensus has dry conditions
for the area as high pressure moves through the Midwest.
Temperatures are expected to average above normal.
Sunday night/Monday the solutions of the global models diverge
considerably on where the next system will track. As a result the
model consensus has mainly dry conditions Sunday night with slight
chance to chance pops on Monday. Precipitation type will depend upon
the track of the storm but a rain/snow mix at night that changes to
rain during the day looks reasonable.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
ISSUED AT 609 PM CDT Mon Mar 13 2017
MVFR CIGs around 2000 ft will continue this evening along with
flurry and snow shower activity, especially in Illinois. By
midnight, clearing should begin to spread over the region, with
VFR weather through the early morning and day on Tuesday.
ISSUED AT 233 PM CDT Mon Mar 13 2017
Record Lows for March 15...
Moline.........3 in 1890
Cedar Rapids...3 in 1979
Dubuque........2 in 1979
Burlington.....9 in 1951
Area Forecast Discussion
National Weather Service Jacksonville FL
901 PM EDT Mon Mar 13 2017
...Widespread Rainfall This Evening...
...Much Cooler Tomorrow through Thu...
.UPDATE...Stratiform rain on the northern side of a Gulf Low was
overspreading the forecast area this evening. Deeper convection
was well south of the forecast area nearing the SW FL coast with
the HRRR now only supporting a low isolated chance of embedded
tstorms across Marion...Putnam and Flagler counties as well as the
adjacent coastal waters over the new couple of hours on the
northern side of the surface low as it tracks across north-
central Florida. After this wave of stratiform pushes offshore of
the coast through midnight...a fading pre-frontal area of
scattered showers will approach from the NW associated with the
actual surface cold front. There will be an ongoing chance of
light showers after midnight due to rainfall potential with this
line...but also expected a gradual erosion of showers through
daybreak as mid/upper level dry slot now across the western FL
panhandle wraps northward across the local area as the upper
trough begins to lift out to the NE. Min temps tonight will range
in the 40s across SE GA to 60s across our southern FL zones under
cloudy skies with some gradual clearing from the west after
midnight as the dry slot punches across the area.
.AVIATION...Prevailing LIFR ceilings are expected through tonight
with recent guidance suggesting the potential for VLIFR 06Z-12Z at
JAX and SSI. Widespread stratiform rainfall will blanket the
terminals through midnight with rainfall gradually tapering off
from the west by 06Z with only a low chance of early morning
showers Tue morning through about 10 am ahead of the surface cold
front. Breezy WNW flow will increase before sunrise to near 10-15
kts ahead of the surface cold front then trailing the front later
in the morning wind gusts up to 20 kts are expected by mid-
morning. Drier air will begin to mix down and erode low clouds
trailing the morning frontal passage with prevailing VFR
conditions expected by midday.
.MARINE...Small craft advisory conditions expected later tonight
trailing surface frontal passage.
Rip Currents: A low risk of rip currents expected on Tuesday.
.PRELIMINARY POINT TEMPS/POPS...
AMG 44 60 34 55 / 80 0 0 0
SSI 48 61 39 54 / 90 0 0 0
JAX 51 62 36 57 / 90 0 0 0
SGJ 52 64 39 57 / 90 0 0 0
GNV 50 66 38 59 / 100 0 0 0
OCF 52 67 39 61 / 100 0 0 0
AM...Small Craft Advisory from 5 AM Tuesday to 6 PM EDT Wednesday for
Waters from Altamaha Sound GA to Fernandina Beach FL from
20 to 60 NM-Waters from Fernandina Beach to St. Augustine
FL from 20 to 60 NM-Waters from St. Augustine to Flagler
Beach FL from 20 to 60 NM.
Small Craft Advisory from 5 AM Tuesday to 11 AM EDT Wednesday
for Coastal waters from Altamaha Sound to Fernandina Beach
FL out 20 NM-Coastal waters from Fernandina Beach to St.
Augustine FL out 20 NM-Coastal waters from St. Augustine to
Flagler Beach FL out 20 NM.
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1017 PM EDT Mon Mar 13 2017
Issued at 1015 PM EDT MON MAR 13 2017
Further adjustments have been made to hourly temperatures based on
recent trends. Snow has been mixing with rain at times per AWOS
and spotter observations from Pulaski county northeast to Rowan
County if precipitation has not changed to snow entirely. Also,
snow has likely fallen at Black Mtn. with a little over a tenth of
an inch of liquid equivalent since the temperature has fallen to
32. The temperature adjustments led a tenth or two more of snow
accumulation in some locations, although attempts were made to
fine to snow ratio to better highlight the higher ridges and lower
elevation valleys. At present, we have about 1 to 1.5 inches
forecast for the top of Pine Mtn above 2500 feet and around 2.5
inches for the top of Black Mountain at about 4000 feet. Lower
elevation locations should pick up generally a dusting to a half
of an inch in some locations. Even with the quicker cool down,
accumulations should mainly be confined to grassy and elevated
surfaces. The SPS will be freshened up a bit based on these
UPDATE Issued at 805 PM EDT MON MAR 13 2017
Recent sfc analysis indicates a surface low over the WV coalfields
east of the CWA east of KSJS and KPBX and south of KCRW and west
of KBKW. The cold front trails south southwest into East TN. A The
temperature on the top of Black Mountain in Harlan County has
wet bulbed down to the 33 degrees per KY Mesonet site data and
snow has likely already started to fall there. Temperatures on NW
flow cold advection have dropped into the mid to upper 30s in the
eastern Bluegrass Counties just east of Lexington while some of
the Big Sandy valley locations are in the lower 50s. LEX recently
reported -SN and 37. The combination of earlier cold air advection
and wetbulbing has led to temperatures cooling off a bit faster
than the previous forecast. Therefore, temperatures have been
trended a couple of degrees colder especially over the next 6 to 9
hours with a lean toward recent HRRR runs. Further fine tuning of
the temperature curve will be needed over the next few hours. In
addition, with preceding low level dry air ahead of the band of
precipitation, qpf has been lowered across northern and eastern
sections to better align with recent observations.
.SHORT TERM...(This evening through Tuesday night)
Issued at 350 PM EDT MON MAR 13 2017
...Some Snow Tonight & Tuesday...Hard Freeze Tuesday Night...
19z sfc analysis shows low pressure centered near STL as high
pressure remains strong along the East Coast. This, and down
sloping in the eastern parts of the CWA, is helping to slow the
arrival of any pcpn from the west ahead of that low. Even the
clouds are having a tough time pushing into eastern Kentucky
resulting in more insolation sending temperatures toward 60
degrees through much of the area. The warmer temperatures and
still very dry air at the sfc are making for another very low RH
afternoon for our eastern counties. Based on satellite trends, the
sky should cloud up over the next couple of hours improving the
low RH as temperatures fall. Dewpoints vary from west to east as
well ranging from the upper 20s over the Cumberland Valley to the
10 to 15 degree range in the east. Winds have also picked up in
the east with the deep mixing resulting in sustained values from 5
to 10 mph and gusts up to 20 mph from the southwest.
The models are in better agreement aloft through the short term
portion of the forecast. They all depict the twin troughs moving
in tandem through the breadth of the country. The southern one is
running along the northeast Gulf Coast this afternoon as the
northern one plows into the Great Lakes. While the southern one
whips up the Southeast Coast, the main portion to the north
settle south toward the Ohio Valley on Tuesday. This brings
sharply lower heights to Kentucky along with a stream of mid
level energy flowing over the state. Heights fall further through
Tuesday night as the mid levels bottom out just to the northeast
with huge impacts along the Mid Atlantic to New England. The
models coming together will make for higher confidence with this
forecast and the blends a decent starting point.
Sensible weather will feature the area clouding up by sunset with
rain moving in early along with falling temperatures. Snow will
start to mix in during the early morning hours tonight in the
highest elevations from northwest to southeast. Extra warmth this
afternoon will make for warmer road temperatures lingering well
into the changeover late tonight and into Tuesday morning. This
should prevent any of the snow from sticking to the roads, though
falling temperatures in the upper 20s northwest may result in some
slick spots on bridges and overpasses there. Will highlight this
in a forthcoming SPS along with a discussion of light
accumulations anticipated through Tuesday afternoon for our ridges
and higher elevations. Expect scattered to numerous snow showers
through the area tomorrow with most places hard pressed to see any
accumulations outside of ridges and places at elevations above
2500 feet. The highest peaks could pick up as much as two inches
of snow before all is said and done, but the vast majority of the
area will see little more than a dusting and mainly on
grassy/elevated sfcs. Temperatures will not go too far on Tuesday
setting up a very cold night into Wednesday morning where mid
teens will be possible for lows - missing record status mainly due
to the post `Storm of the Century` lows of 1993. Will issue a
freeze warning for this night starting at 8 pm Tuesday and lasting
through noon Thursday as readings will not make it far above
freezing on Wednesday.
Again used the CONSShort and the ShortBlend as the starting point
for the grids throughout the short term portion of the forecast.
Made only minor changes to the lows tonight and Tuesday night
given the higher moisture tonight and CAA into Wednesday morning.
Worked with the PoP grids to slow the higher values arrival this
evening and to fine tune them later tonight into Tuesday for
some upslope flow enhancement.
.LONG TERM...(Wednesday through Monday)
Issued at 308 PM EDT MON MAR 13 2017
High pressure will settle over the area from Wednesday through
Thursday evening. The abnormally cold conditions will continue
with temperatures on Wednesday struggling to reach freezing. Then
lows Wednesday night may fall into the lower to mid teens
areawide, setting up the coldest night of the week. Given this
long period of sub-freezing temperatures, will keep the freeze
warning going through Thursday morning. A shortwave trough will
then cross the Ohio river valley Friday and Friday night with our
next good chance for rain. Temperatures should warm enough ahead
of this system to yield all rain. While it does cool off in the
wake of this system on Saturday, not nearly as good of a push of
cold air this time, so may see a few wrap around rain showers into
Saturday afternoon. We dry out again by Saturday night and Sunday
as high pressure again crosses the area. Rain chances will start
to ramp back up on Monday as our next system starts to approach
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 835 PM EDT MON MAR 13 2017
A band of rain is moving across the area on the backside of
surface low moving across the Appalachians and in advance of a
mid level wave. CIGS will continue to fall into the MVFR range at
the TAF sites over the first 3 to 5 hours of the period with KSJS
expected to reach MVFR last. Conditions will continue to
deteriorate down to IFR between 03Z and 09Z, with snow mixing in
with the rain starting by 3Z at KSYM in the northwest and the
highest elevation near VA first then mixing everywhere by 7Z. CIGS
should improve from northwest to southeast between 10Z and 16Z as
drier air moves in at lower levels and lingering snow showers
diminish to . Winds should average out of the west and northwest
at 5 to 10 KT.
Freeze Warning from 8 PM Tuesday to noon EDT Thursday for KYZ044-
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
850 PM CDT Mon Mar 13 2017
850 PM CDT
No big changes planned to going forecast at this time.
Lake effect snow has been blossoming this evening, largely
consisting of multi-banded structure into NE IL and SE WI as the
previously semi dominant single band over SE Wisconsin weakened.
The array of hi-res model guidance is in good agreement in
depicting strengthening low level convergence through the night
with already favorable LES parameters actually growing even more
favorable with time. Eventually, would anticipate this multi-
banded LES structure to begin to transition back to a more
dominant and intense single band, though how long that process
takes to occur is the big question.
Given recent observational trends, increasingly leaning toward a
later development of the single banded structure, possibly not
until closer to sunrise. The more multi-band structure should
result in a more widespread snowfall, but likely less intense
snowfall rates. Snowfall intensity/rates will increase
significantly when single band eventually develops, with snowfall
rates exceeding 2"/hour likely at that time.
The later the transition to single band occurs, the likely farther
east placement of the heaviest totals. Starting to look like the
highest totals tonight into Tuesday could be across eastern and
southern Cook County, though Lake County IL is not quite out of
the woods yet.
Have decided to add Lake Co IN into the warning as such strongly
favorable parameters will likely keep the intense snow rates going
through at least midday tomorrow with a good chance of at least 6
inches of snow in northwestern Lake Co IN and double digit totals
not out of the question by late tomorrow afternoon.
LES should begin to weaken somewhat tomorrow afternoon, but
continue into tomorrow evening. Parameters tomorrow night again
look quite favorable for heavy lake effect snow. While inversion
heights will be somewhat lower and we`ll lose the added synoptic
ascent, instability and low level convergence look stronger than
tonight. We are far enough out that there is an urgency to issue
any headlines for Porter Co, but this is something the midnight
shift will likely have to contend with. Will leave the expiration
for Lake Co the same at 06z tomorrow night, but that may be a bit
soon and could need refining tomorrow.
Will get updated WSW shortly, updated grids and forecasts will
follow, though perhaps not quite as quickly!
311 PM CDT
Through Tuesday Night...
Heavy lake effect snow continues to be the primary forecast
concern and forecast challenge this afternoon. Overall, the same
thinking holds true, with the potential for localized areas of
very heavy snow tonight into Tuesday across the warned area. The
only change to the headlines was to add a lake effect snow
advisory to Will county and Lake county Illinois, where lake
effect snow showers are likely to lead to some accumulations.
Lake effect snow has been ongoing across southeastern Wisconsin
for much of the day. In spite of the fact that these snow showers
have yet to focus into a single band, reports under these snow
showers have been for periods of moderate to occasionally heavy
snow, with visibilities of 1/2 to 1/4 mile. Therefore, the
confidence in lake effect snow impacting northeastern Illinois
tonight into Tuesday is high. Overall, we expect the focus for the
lake effect to shift southward into northeastern Illinois by mid
evening as a lake induced boundary layer convergence zone sets up
over southern Lake Michigan and extends onshore over far northeast
Illinois. This convergence zone should help focus the lake effect
snow showers into a more organized band by mid to late this
evening. HiRes forecast guidance including the latest HRRR is in
favor of this thinking. Overall, we expect this lake effect band
of snow to be quite intense at time as thermodyamics over the lake
remain favorable for good lake effect through into Tuesday.
Therefore, snow rates of 2"+ per hour are likely under the band of
The main challenge with lake effect snow events such as this is
forecasting snowfall accumulations over a broader area. Because
the heaviest snow showers are likely to be in a band only about
around 15 miles wide, there is likely to be considerable
variability in snowfall amounts over short distances. Some of
this large variably is likely to occur over the Chicago area.
Areas falling under the heaviest band of snow, which at the
present time looks to favor portions of Cook...eastern Dupage and
at least southern Lake county Illinois, a good 5 to 10 inches with
isolated higher amounts appear likely.
The main band of heavy lake effect snow appears that it may
gradually shift southward or waver across Cook and Dupage
counties through the night. This would suggest that the lake
effect showers will begin to impact portions of Will and Lake
county Indiana, especially later tonight into Tuesday. Additional
heavy bands of snow may then shift back over far northeastern
Illinois by Tuesday morning. For this reason, it appears that
there could be a prolonged period or two of heavy lake effect snow
over portions of the warned area, and this could result in
isolated higher amounts than currently forecast.
Lake effect showers will be possible through Tuesday for
northeastern Illinois, before the main focus for lake effect
begins to shift over northwestern Indiana. Additional headlines
for lake effect may be needed for more counties in Indiana, but
since most of these areas will not get in on most of the lake
effect snow until either later Tuesday or Tuesday night, we have
opted to hold off on this for now. Its even possible that the
current advisory in effect for Lake county Indiana may need to be
upgraded to a warning if it becomes apparent that heavier snow
will fall there on Tuesday.
328 PM CDT
Wednesday through Monday...
Following the lake effect snow, which should wind down over over
northwestern Indiana on Wednesday, cold surface high pressure will
build over the area. As a result, daytime temperatures on
Wednesday are likely to remain in the 20s. However, with the cold
surface high moving overhead Wednesday night, this may set the
stage for cold temperatures over the area into Thursday morning.
However, after this cold morning, temperatures should begin to
moderate later in the week as the surface high shifts east of the
Another fast moving storm system looks to take aim on the area
later in the week (Friday into Friday night). This system could
produce another period of mainly rain over the area, though it
could onset as a mix of rain and snow Thursday night. Otherwise,
temperatures should become more seasonal later in the period.
For the 00Z TAFs...
Tricky forecast regarding lake effect snow potential tonight with
high confidence in lake effect snow in the region, but low
confidence on the extent and location of the more intense snow.
Presently, tracking one more pronounced WSW-ENE oriented band over
SE WI and anticipate this band to continue moving southward and
likely to impact the NE IL terminals later this evening. Big
question is how progressive this band will be and whether or not
it will stall over any of the terminals. For now, took a somewhat
more optimistic approach in the TAF with a short duration of
heavier snow. Its possible the heavier lake effect snow band could
evolve and take shape just east of ORD/MDW overnight and while
confidence isn`t high, have opted to go that route for now in the
TAFs. Some hi-res guidance suggests the lake effect band could
wiggle west for a time Tuesday morning and covered this potential
in a prob30. Overall, a low confidence TAF and additional
amendments will likely be required as smaller scale lake effect
features begin to reveal themselves. Winds should favor NE
direction initially, though to the west of more prominent band
development, land breeze should result in a backing of winds to a
more northwesterly direction.
253 PM CDT
A period of strong is expected through Tuesday, as strong high
pressure builds southeast into the Mississippi Valley, and deep
low pressure lifts north along the Atlantic coast. Winds of 30 kts
are expected later tonight and Tuesday, with some gale force gusts
possible. Winds will slowly ease Tuesday night while backing to
the northwest, and will further diminish Wednesday night into
early Thursday as high pressure ridging moves east across the
area. Winds will then increase from the south late Thursday night
into Friday, as the ridge moves east and an area of low pressure
develops northwest of the Lake. This low will deepen and track
east across the region Friday and Saturday, with gusty south winds
becoming westerly Saturday and then northerly Sunday.
IL...Lake Effect Snow Warning...ILZ006-ILZ013-ILZ014 until 4 PM
Lake Effect Snow Advisory...ILZ022 until 4 PM Tuesday.
IN...Lake Effect Snow Advisory...INZ001...4 AM Tuesday to 1 AM
LM...Small Craft Advisory...IL nearshore waters until 9 AM Wednesday.
Small Craft Advisory...IN nearshore waters until 9 PM Wednesday.
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
Area Forecast Discussion
National Weather Service Miami FL
752 PM EDT Mon Mar 13 2017
Latest model data suggest a push back of the expected showers and
thunderstorm activity to late tonight, thus delay the higher POPs
closer to midnight. The HRRR shows a define line of thunderstorms
around midnight with another round of showers in the morning hours
with the main frontal boundary moving across the peninsula. SPC
continues to keep a marginal risk of damaging winds for Southwest
Florida Gulf Coast where the threat is maximized due to slightly
higher moisture and instability compared to the rest of South
Florida. Once the front moves through the area, drier air makes
its way into South Florida. No additional changes were done to
.PREV DISCUSSION... /issued 345 PM EDT Mon Mar 13 2017/
Showers and Thunderstorms Tonight, some may become strong...
Weather pattern changes tonight into Tuesday as a low
pressure system moves across the area. If you thought
it was time to put the sweaters away, don`t do so yet,
as this system will bring cooler air into South Florida
Near term: As shortwave trough digs southeast towards
the lower MS Valley this evening into tonight, deepening
surface low pressure over northern Gulf coast moves east
into the Florida peninsula. Ahead of this system, wind
fields strengthen over South Florida tonight, with deep
layered shear of 50 knots by late evening hours. This
will enhance showers and thunderstorms into the overnight
hours with some possibly strong.
As this low approaches the area from the eastern Gulf coast,
isolated showers and thunderstorms will begin to develop and
increment becoming more scattered in the evening and tonight
over South FL. Main focus of showers/thunderstorms will come
in the form of a squall line or band of embedded thunderstorms
moving west/east across the peninsula. Upper jet stream of 140+
knots over North Florida along with strengthening wind fields
down through the low levels will provide sufficient dynamics
and forcing for potentially strong to even severe thunderstorms.
Storm Prediction Center continues to keep a marginal risk of
damaging winds for Southwest Florida Gulf Coast where the threat
is maximized due to slightly higher moisture and instability
compared to the rest of South Florida. However, the potential
for a few strong storms with gusts over 40 mph are certainly
a distinct possibility elsewhere over South Florida as the
showers and storms spread east during the overnight hours.
The shower activity will continue through early Tuesday as the
associated cold front moves across the peninsula. Abundant dry
air behind the front with cooler temperatures will filter into
the region giving way to clear skies by Tuesday afternoon and
pleasant daytime temperatures. Expect a west to northwest wind
flow with high`s remaining near 80s degrees for the southern
counties and . upper 70s out west and interior. As high pressure
continues to settled into the area, the cooler temperatures will
begin to be felt into Tuesday night, with temperatures dropping
into the upper 40s to near 50s. Highs on Wednesday will struggle
to reach the 70s despite the mid-March sunshine, and probably
stay in the 60s along the Gulf coast.
Through the Upcoming Weekend: The cool, dry pattern will prevail
as continental high pressure dips deep into the Southeast U.S. and
remains in control of the weather pattern for the rest of the week
into next weekend. This will deliver the first extended period of
below normal temperatures to South Florida since late January.
Coldest night will be Wednesday Night/Thursday morning with lows
around low 40 degrees west of Lake Okeechobee to the mid 40s rest
of interior and Gulf coast, to the lower 50s SE Florida metro
area. Some moderation in temperatures is expected for Friday and
the upcoming weekend, but still mainly below normal with low
SE to S winds continue this afternoon, highest over the Atlantic
waters, will increase out of the SW tonight as the low pressure
area shifts into the Atlantic and deepens. A Small Craft Advisory
will be in effect for the Atlantic waters and Gulf waters continuing
through Tuesday night. Expect periods of winds in the 20-25 knots
range and seas in excess of 7 feet. Conditions gradually subside
through Friday as the high pressure area moves over North Florida
and winds begin to subside.
Latest model data suggest a little push back of the expected
showers and possible thunderstorms to later tonight, thus VCTS
starts now around 22Z and continues through 06z for all terminals.
Breezy periods are possible through the evening hours with overall
speeds in the 12-15 kt range with higher gusts. MVFR is possible
at time with the heaviest showers or with passing thunderstorms
tonight, especially over the Atlantic terminals. Once a frontal
passage moves across the area, VFR and drier conditions will
begin establishing on Tuesday.
.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach 67 81 52 69 / 70 20 0 0
Fort Lauderdale 71 82 54 71 / 50 20 0 0
Miami 72 81 56 72 / 50 20 0 0
Naples 69 73 51 68 / 60 10 0 0
AM...Small Craft Advisory until 8 AM EDT Wednesday for AMZ650-651-670-
GM...Small Craft Advisory from 4 AM to 8 PM EDT Tuesday for GMZ656-
Area Forecast Discussion
National Weather Service Nashville TN
723 PM CDT Mon Mar 13 2017
FOR EVENING DISCUSSION.
Shower activity now located over only the Plateau portion of
middle TN. Upstream shortwave axis is located over western TN at
this time. This feature will reach our Plateau around midnight.
Thus, the deeper moisture will quickly move east. However, weak
impulses upstream may carry some pva across our eastern half of
the cwa after midnight. Furthermore, freezing levels will be
dropping and should be in the 700 ft to 1000 ft agl range after
midnight across northern areas, and then southern areas after 09z.
Hrrr does show some patchy areas of precipitation late, so there
lies the light snow potential. Lower level vv`s are generally
negative so precip amounts, if any, will be very light.
Current fcst appears to be on track with a low chance of rain and
snow after midnight. Will likely rerun zone formatter just to
clean up wording as we move toward the 9pm or 10pm hour.
00Z TAF DISCUSSION.
Rainfall will gradually end at CSV around 03Z, then a brief period
of MVFR VIS and CIGS with possible IFR CIGS is expected to develop
at all three TAF sites. Any VIS or CIG reduction should begin lift
after 08Z as a tightening pressure gradient causes northwest winds
to intensify, with peak wind gusts near 20kts possible after 15Z.
Freeze Warning from 7 PM Tuesday to 10 AM CDT Wednesday FOR
Area Forecast Discussion
National Weather Service Blacksburg VA
1044 PM EDT Mon Mar 13 2017
Moisture should increase ahead of a developing coastal low
pressure system this evening. This complex winter storm will
impact much of the region through tonight into Tuesday. Colder
air with gusty northwest winds should follow later this week.
.NEAR TERM /THROUGH TUESDAY/...
As of 1020 PM EDT Monday...
No changes planned to the headlines, though confidence is
falling on snow amounts, especially in the valleys. Latest
mesoanalysis shows 1007 mb low southeast of Cape Fear NC, with a
1012 low near Bristol VA. The models have been overdoing the
warm nose a bit over the NC mountains and up the Blue Ridge as
temperatures are below freezing in the 900-850 mb level, as seen
in places like Bent Mountain VA, Silverstone and Boone, NC.
Still warmer air aloft is occurring west of Bluefield as
Richlands south to Chilhowie are running in the mid to upper
30s. Temperatures elsewhere were generally in the lower 30s.
The latest RAP and HRRR showing the band of mainly rain, mixed
with sleet from the Triad of NC northward to Buckingham VA, with
next band of precip moving into SE WV to far SW VA as of 1015pm.
This is the band of precip we will have to rely on to give us
our accumulating snow. Models continue to show good lift and
frontogenetical forcing sliding to WV/VA highlands after 06z
tonight. However, this band will have to stay ahead of the dry
slot that is now moving toward SW North Carolina per WV loop.
Snow to liquid ratios will stay pretty much at 5 to 10:1 through
most of the overnight, then drop after 12z but by then the
synoptic portion of the system will be lifting out replaced by
upslope snow showers. Made some adjustments to the snow totals,
where the higher ridges will still see a few inches, but looking
less in the Roanoke Valley east Lynchburg. Some of the models
even are showing some pockets of freezing rain though given
ground temperatures, should only see a light glaze on metal
objects. This mainly will occur just along the eastern slopes of
the Blue Ridge from Patrick County northeast toward Buckingham.
Still looks like enough snow/sleet issues overnight to cause
travel headaches and greatest totals will be north of a line
from Hinton WV to Blacksburg to Lexington to Amherst, where 3 to
6 inches is likely. This is just for tonight, with more expected
in the upslope areas of SE WV to NW NC Tuesday.
Visit our winter weather page for snow graphics at
Previous early evening discussion...
A mixture of snow/sleet and rain ongoing from NC into VA mainly
east of the WV/VA border, with mainly rain in the piedmont.
Models are showing warm nose intruding this evening as low over
the low off the SC coast starts to lift north- northeast, along
with another warm nose over the southwest with front moving in
from far SW VA. This will lead to mixture of ptypes with
predominately staying snow over the Alleghanys, with mixture of
rain/snow/sleet elsewhere. The better lift and forcing arrives
around midnight and expect dynamical cooling to allow for more
snow in the west, with models showing a band of snow passing
from Srn WV into the New River and Southern Shenandoah valleys
after midnight. Will still be a battle between rain/sleet/snow
along and east of the Blue Ridge south of a Roanoke to Bedford
line, so not expecting much accumulation through early overnight
for places like Rocky Mount to Lynchburg, but more toward 4am.
Current headlines still seem in good shape, so no changes
Previous discussion from early afternoon...
An approaching clipper system with an associated upper level
trough over the Ohio River Valley will merge with a developing
coastal low pressure system along the North Carolina coast
tonight. At this moment, radar only shows precipitation
entering Southside Virginia and the North Carolina Piedmont.
With temperatures currently in the mid 30s to the mid 40s for
most locations, the boundary layer will not be able to allow any
frozen precipitation to stick. Most locations may see rain
mixing with sleet during the evening, but appreciable
accumulations will not materialize until later tonight. Based on
the latest snowfall amounts in this update, we will be adding
Tazewell and Smyth counties to the Winter Weather Advisory. No
other changes to the headlines are needed at this time.
As better isentropic lift arrives overhead, precipitation rates
should increase tonight enough to allow atmospheric cooling
aloft. This pattern supports a mix of sleet and snow for along
and west of the Blue Ridge with some mixing of sleet and rain to
the east. The coastal low pressure system should undergo
significant cyclogenesis overnight as it heads northeastward.
Eventually, most locations should see a mix of snow and sleet
toward Tuesday morning with temperatures near the freezing mark
in the Piedmont and lower into the 20s elsewhere. Although the
precipitation should gradually wane during the morning, upslope
snow showers will persist along southeast West Virginia through
the day. Northwest winds will become gusty by the afternoon,
and temperatures will struggle to reach the 40s in the Piedmont.
Some parts of southeast West Virginia may see temperatures
gradually fall during the day due to the strong cold air
advection and snow cover.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 200 PM EDT Monday...
Northwest flow will prevail in the wake of the strong cold front.
This will yield upslope snow showers across the preferred locations
across portions of southeast West Virginia, south into the Northern
Mountains of North Carolina. Cold air advection will be significant
with the surge of air behind the front, with maximum pressure rises
occurring during the early morning hours of Wednesday. The area of
our region near the crest of the Blue Ridge from roughly Floyd, VA,
southwest into the Northern Mountains of North Carolina may be
candidates for a Wind Advisory during this time period. Also, the
combination of the strong gusty winds and decreasing temperatures
may yield wind chill values across the higher elevations in the Wind
Chill Advisory levels. Will continue to highlight both of these
scenarios within the Hazardous Weather Outlook. Scattered snow
showers across the western parts of the area will continue on
Wednesday, but gradually decrease in coverage as the day progresses.
Wednesday night into Thursday, anticipate a gradual decrease in wind
speed, with isolated snow showers becoming confined to western
Greenbrier County, WV.
Outside of the area of upslope snow showers, the vast majority of
the region will have little if no cloud cover Wednesday into
Temperatures during this portion of the forecast will average ten to
fifteen degrees below normal.
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 330 PM EDT Monday...
Upper trof moves offshore Thursday night with 500MB ridging on
Friday. An upper low develops over the Great Lakes on Saturday then
moves off the New England coast on Sunday. At the surface, the axis
of high pressure crosses the Mid Atlantic states on Thursday night.
A cold front will push across the area on Friday night. The high
that follows Friday night`s system will arrive in the area on Monday
The low level jet backs to the west southwest with 850 MB wind
speeds of 45 to 55 knots Friday night. Ahead of this system,
temperatures warm back above freezing. Then cold air advection
Friday night at Saturday low 850MB temperatures back below zero on
Saturday and continue to lower through Sunday morning. Persistent
northwest winds until Monday morning. May not erode all the 1ow
level moisture and upslope showers until that time.
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
As of 715 PM EDT Monday...
Expect deteriorating flying conditions this evening into
overnight with most if not all taf sites sinking to LIFR or
lower with mixture of rain/snow/sleet across ROA east to LYH/DAN
with more wintry wx in the BCB/BLF/LWB corridor.
All sites except DAN should see all snow toward daybreak.
The main system lifts out Tuesday morning then northwest flow
kicks in, which should keep BLF/LWB MVFR or worse through midday
then some VFR after 18z. Further east looking at improvements to
VFR between 13-17z. Winds will be gusty from the northwest.
Extended Aviation Discussion...
Gusty northwest winds along with upslope snow showers should
persist well after the winter storm heads toward the New England
coast. Periods of MVFR/IFR should linger at times over BLF/LWB
into Wednesday. Meanwhile, confidence is higher for VFR at the
other TAF sites by Wednesday afternoon. Eventually, all sites
should reach VFR on Thursday with northwest winds slowly
dissipating. High pressure builds overhead on Thursday night. A
weak low pressure system should arrive from the west by Friday
and Saturday. Although precipitation appears mainly liquid,
periods of MVFR/IFR ceilings should accompany this system.
Record mins and record low maxes are below for March 14th and
Site MinT Year LoMax Year
KBLF 8 1993 18 1993
KDAN 15 1960 34 1993
KLYH 17 1968 28 1993
KROA 16 1993 23 1993
KRNK 8 1998 32 1960
Site MinT Year LoMax Year
KBLF 6 1993 24 1988
KDAN 12 1993 34 1993
KLYH 7 1993 34 1937
KROA 9 1993 34 1988
KRNK 4 1993 22 1993
VA...Winter Weather Advisory until 2 PM EDT Tuesday for VAZ009>014-
Winter Storm Warning until 2 PM EDT Tuesday for VAZ019-020-024-
Winter Weather Advisory until 8 AM EDT Wednesday for VAZ007-
NC...Winter Weather Advisory until 2 PM EDT Tuesday for NCZ002.
Winter Weather Advisory until 8 AM EDT Wednesday for NCZ001-
WV...Winter Weather Advisory until 2 PM EDT Tuesday for WVZ044.
Winter Storm Warning until 2 PM EDT Tuesday for WVZ507.
Winter Weather Advisory until 8 AM EDT Wednesday for WVZ042-
Winter Storm Warning until 8 AM EDT Wednesday for WVZ508.