Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/21/17
Area Forecast Discussion
National Weather Service Bismarck ND
951 PM CDT Thu Apr 20 2017
.UPDATE...
Issued at 951 PM CDT Thu Apr 20 2017
Forecast remains on track. Latest RAP run has backed off
considerably on fog coverage later tonight, much closer to HRRR
solution. Models still indicate good fog coverage across central
ND, but have backed off across the south. Light winds, clear skies
and recent rainfall across this area in particular should support
fog development overnight.
UPDATE Issued at 646 PM CDT Thu Apr 20 2017
No changes with the update other than to blend with latest obs.
Satellite imagery continues to show clearing from west to east.
Main concern for overnight will be fog development. RAP continues
to hit fog the hardest, while the latest HRRR has backed off
slightly southcentral, with most extensive coverage across the
southwest and James River valley.
&&
.SHORT TERM...(This evening through Friday)
Issued at 302 PM CDT Thu Apr 20 2017
Mid/upper level synoptic pattern favors a brief omega type block
forming over western and central North Dakota through the short
term period. Although this will result in a dry forecast, prospects
of fog formation will increase tonight into Friday morning.
For the near term, through this afternoon and early evening, popcorn
type/isolated rain showers remain on track this afternoon south
central into the James River Valley with a tail end shortwave
trough shifting through south central ND. Sufficient low to mid
level lapse rates will result in isolated showers until sunset.
Latest water vapor shows a closed upper level low in northeastern
Minnesota and another shortwave in western Idaho which is forecast
to develop into a closed low as it traverses into Wyoming later
tonight into Friday. A brief omega block pattern evolves across
western and central North Dakota. Main concern will be radiational
fog/possibly dense, developing after midnight especially in
central and southern North Dakota. Subsidence aloft with a clearing
sky in the west this afternoon will expand into central ND
tonight. Expecting to see a gradual clearing from west to east
this evening, however clouds in central ND may inhibit or delay
fog formation until late tonight. Low level moisture remains with
southeasterly winds developing as surface high pressure builds
into the Turtle Mountains. High resolution models in combination
with the BUFKIT Hydrolapse/CrossOver Temperatures and Modified
Richardson Number all point to fog. Expecting areas of
fog/possibly dense after midnight into Friday morning with
overnight lows in the 30s.
For Friday after the morning fog, blocking high pressure results
in subsidence and mostly sunny conditions with highs in the 60s.
.LONG TERM...(Friday night through Thursday)
Issued at 302 PM CDT Thu Apr 20 2017
Mid/upper level high is shunted south Friday evening as northwest
flow with an embedded shortwave trough and associated cold front
move into northern North Dakota. This front then sags to the
southern ND border Saturday afternoon. A chance of rainshowers
resides mainly across the north Saturday as depicted by the
alignment of synoptic scale forcing and low level frontogenesis.
There could be a period of rain/snow mix Saturday morning across
the north. Very cool in the north with high temperatures 40s to
lower 60s south. Frontal boundary stalls in northern South Dakota
Saturday evening with a chance of showers developing north of the
front, into southern North Dakota. Thereafter the pattern remains
progressive with a series of systems mostly tracking from west to
east across South Dakota. The GFS and ECMWF are not as wet with
the initial system slated for Sunday night and Monday across
central and southern ND. Still a high chance of pops to likely
pops remain in the gridded data. Periodic chances for precipitation
continue Tuesday through Thursday but confidence for anything
significant and organized remains low at this time. Highs will be
in the 40s and 50s through the period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 646 PM CDT Thu Apr 20 2017
Clouds continue to erode from west to east early this evening.
Expect fog development most areas overnight into Friday morning,
with IFR possible at most locations and LIFR currently in the
forecast from KDIK-KBIS-KJMS.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...JNS
SHORT TERM...KS
LONG TERM...KS
AVIATION...JNS
Area Forecast Discussion
National Weather Service State College PA
1115 PM EDT Thu Apr 20 2017
.SYNOPSIS...
A frontal system will move through the Commonwealth tonight and
early friday. A ridge of high pressure will then build into the
area Friday night. A new storm tracking across the southeast
states could potentially affect southern Pennsylvania this
weekend.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
The meso anal shows the main low over lower Michigan. A cold
front extends from the low and bisects Indiana off through
southern Illinois. A warm front extends from lake Erie east
along the NY/PA border then doglegs sharply south through the
Susq River Valley. This has moved little since this morning and
has helped enhance windshear over the north where several storms
have shown good rotation.
A line of convection is moving through the northern mountains as
of 10PM with isolated strong/severe storms embedded in the line.
The storms are moving into progressively more stable air so the
threat of damaging wind and hail should transition into briefly
heavy rain.
The HRRR shows the MCS continuing across the CWA overnight
with a line of showers marking the cold front finally moving
through the Central Mountains between 12-15Z Friday morning.
It will be another very mild overnight in the 50s region-wide.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
00Z models a bit slower with passage of cold front Friday, so
have held onto the chance of morning showers over all but the
northwest mountains. Pre-frontal heating across the southeast
counties will likely yield a few thunderstorms across that
portion of the state before the front finally exits the area by
late afternoon.
Friday will be another warm day with increasing sunshine and GEFS
925temps supportive of max temps well into the 70s southeast of
the Alleghenies.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
The extended period will begin dry as a shallow cold front
settles south of the region for Friday night and Saturday.
EFS trends for Saturday and Saturday night track moisture
farther south than previous runs...with showers brushing the
southern third to half of central PA Saturday afternoon and
evening before sliding south of the Mason Dixon line for Sunday
and Monday. With uncertainty remaining on the northern extent of
showers for this system...have maintained consistency in slight
chc to chc POPs during this time frame.
Baroclinic zone will be lurking south and southeast of the area
early to mid week...while a frontal system crosses the Great
Lakes and approaches by Wed-Thu. This should bring an increasing
chc of showers by Wed-Thu...but confidence in timing very much
in doubt by Days 6-7 as large scale height rises at the end of
this time period and beyond will hinder the eastward progress of
the Glaks frontal system.
The aforementioned height rises are a potentially important
signal for the beyond Day 7 timeframe of a large warmup for next
weekend.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Widely scattered showers and isolated storms over the east,
given southeast flow. Will adjust 03Z TAFS for this.
Left some showers in for later, given activity over the Ohio
Valley. However, activity to the west is spotty.
Should clear out behind the cold front by lunch time on
Friday.
Outlook...
Sat...Mainly VFR with chance of rain increasing by Sat night
over the southern airspace.
Sun...MVFR/IFR with rain mainly across southern PA. Mainly VFR
across the north.
Mon-Tue...No significant weather expected.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...Fitzgerald
LONG TERM...DeVoir
AVIATION...Martin
Area Forecast Discussion
National Weather Service Grand Forks ND
936 PM CDT Thu Apr 20 2017
.UPDATE...
Issued at 935 PM CDT Thu Apr 20 2017
No changes necessary.
UPDATE Issued at 633 PM CDT Thu Apr 20 2017
Although no returns as of yet from regional radars will keep isold
shras going for another hour or so but low confidence on anything
developing. Otherwise only changes were to adjust cloud cover to
allow for more clearing over Mn.
&&
.SHORT TERM...(This evening through Friday)
Issued at 258 PM CDT Thu Apr 20 2017
Any showers this evening and the possibility of fog tonight will
be the main issues for the period.
Water vapor loop shows the main upper low moving through eastern
MN, but another weak shortwave has been rotating along the
backside of it through eastern ND. Some of the clouds have taking
on a more cumuliform appearance on sat loops, and the SPC meso
analysis page shows some fairly steep low level lapse rates across
the northern Red River Valley. The HRRR and to a lesser extent the
RAP has some showers developing mainly along and west of the Red
as that shortwave moves through this evening. Will continue to
keep some low POPs going across much of the western counties into
the early evening before any showers dissipate after we lose
daytime heating. The rest of the night should remain dry as
surface high pressure builds into the region.
With the high coming in, winds will decrease overnight and become
light and variable. There will be at least some clearing after
sunset, and with recent rainfall, patchy fog formation will be
possible. Have a mention for most of the area. Temps tomorrow will
depend on exactly if and where fog forms and how fast it
dissipates. Not too much mixing tomorrow at least early on with
the surface high shifting only slowly eastward. However, think by
afternoon we will at least get some south to southwest winds, so
with sunshine late in the day think that highs will be in the
upper 50s to low 60s.
.LONG TERM...(Friday night through Thursday)
Issued at 258 PM CDT Thu Apr 20 2017
Friday night through Sunday...A backdoor cold front will move down
from Canada during Sat morn into the aftn with some light rain or
showers, freshening wind and falling temps behind the boundary.
Look for this feature to pause near the ND/SD border before slowly
moving back to the north as a warm front during Sun. The thrust
of the pcpn will most likely be Sun night into Mon where amounts
of between one quarter to one half inch of rain will be spread
throughout the region.
Monday through Thursday...Packages of ensemble guidance point toward
a cool week to come with average maximum temps in the upper 40s
to low 50s and lows dropping to near freezing most nights. Periods
of light pcpn could feature a wintry mix early in the morning,
especially across northern locations. Differences persist between
the GFS and ECMWF in timing and position/strength of shortwaves
and sfc systems. The GFS is weaker and farther south generally
affording the forecast area a drier solution.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 633 PM CDT Thu Apr 20 2017
Clouds looking pretty cellular so anticipate clearing through the
evening. With clearing...low level rh in place and diminishing
wind main concern tonight will be fog. With high center dropping
into the DVL basin this area looks to have the best potential for
fog supported by model fog guidance. Dropped vsby down in DVL but
with lower confidence to the east left out of TAFs but will
monitor. Otherwise expect VFR conditions through the period.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Voelker
SHORT TERM...JR
LONG TERM...WJB
AVIATION...Voelker
Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
923 PM MDT Thu Apr 20 2017
.UPDATE...
Issued at 920 PM MDT Thu Apr 20 2017
Updated the forecast through midnight tonight. Cold front will
continue moving through western CO this evening with a nice
vort max in the flow traveling just north of Grand Junction and
should track over Rifle and Eagle.
UPDATE Issued at 819 PM MDT Thu
Apr 20 2017
Winds have been dropping steadily in the zones impacted by the Red
Flag Warnings with relative humidity values climbing back up and
above 15 percent. With weather conditions improving in regards to
fire weather conditions, have allowed the Red Flag Warning to
expire for Colorado Fire Weather Zones 207 and 290. Now we turn
out attention to the increasing showers and isolated thunderstorms
across our central and northern zones. Expect snow levels to
slowly drop through the overnight period with light to moderate
snowfall accumulations across the northern and central mountains
above 9000 feet. Current Winter Weather Advisories remain on track
with the heaviest snowfall expected across the Park Range near
Steamboat Springs and over the Flat Tops. HRRR run has nudged
snowfall up a bit, but still within advisory criteria. Rabbit Ears
Pass and Vail Pass will be impacted by this passing system.
&&
.SHORT TERM...(Tonight through Friday night)
Issued at 333 PM MDT Thu Apr 20 2017
Isolated to scattered showers popping as expected in the
warm...highly mixed atmosphere this afternoon. Dry air really
infiltrating from the southwest is keeping most of the activity
limited to the central and northeast zones with a few strikes of
lightning in the mix. The warm temperatures and instability is
also helping mix winds down with Red Flag conditions being met
across SW.Colorado and the occasional strong gusts near showers.
The upstream system digging out of the PacNW has trended northward
the past 24 hours with the slower fropa of the GFS also
verifying better today. This front will be the focus for
organized precipitation moving across the northern half of the CWA
this evening with the large scale dynamics and orographic flow
keeping precipitation focused on the portions of the central and
northern Colorado mountains through Friday evening. The northward
trends of the models will not have a huge impact on the forecast
with the best accumulating snow favored over the higher terrain
from the Park to the Elk Ranges. Some snow likely to fall in the
upper Yampa...Colorado and Eagle Basins but temperatures do not
appear favorable for accums on the roadways at this time. The
pattern in the central CONUS takes on a mini-Rex pattern as the
negatively tilted trough over the Rockies undercuts the ridge of
high pressure it will be replacing. This allows a back edge energy
to rotate across the northern mountains to front range early
Saturday and may keep some snow showers going across the divide.
Temperatures on Friday can be expected to be some 10 to 15
degrees cooler than today behind the front with lows dipping in
into the mid to lower 30s in some of the western lower valleys.
.LONG TERM...(Saturday through Thursday)
Issued at 333 PM MDT Thu Apr 20 2017
A gradual warmup begins Saturday with warm and breezy conditions
setting up for Sunday as we get transitory short wave ridging
setting up over the Rockies. A pattern change does look to be on
the horizon after this as more amplified ridging in forecast to
develop in the northern Atlantic and central Pacific. This will
force the jet stream farther south leading to a general and
prolonged trough pattern over the West. As a result cooler and
more active weather will be impacting our region. Details still
fuzzy but appears a brush by system is likely Monday followed by a
more significant storm system by midweek. Downstream blocking
will allow this system to organize and wrap up farther west than
the past several storms. Temperatures stay seasonable up until
this possible scenario then would cool significantly to end the
week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 540 PM MDT Thu Apr 20 2017
Scattered showers and thunderstorms will continue through this
evening with showers becoming more widespread along and north of
Interstate 70 after 09Z tonight. Rain or a rain/snow mix will
changeover to all snow in the mountains overnight, favoring the
northern and central CO mountains for moderate to locally heavy
snowfall rates through Friday morning. CIGS will gradually lower
this evening with widespread MVFR to IFR CIGS/VSBYS over northern
and central CO mountains, through about 18Z Friday.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until 6 PM MDT Friday for COZ004-010-013.
UT...None.
&&
$$
UPDATE...CC
SHORT TERM...15
LONG TERM...15
AVIATION...JDC
Area Forecast Discussion
National Weather Service Grand Rapids MI
738 PM EDT Thu Apr 20 2017
LATEST UPDATE...
Aviation
.SYNOPSIS...
Issued at 322 PM EDT Thu Apr 20 2017
Showers and thunderstorms will end this evening as a cold front
moves across Lower Michigan. High pressure will then build into the
region providing sunshine from late Friday through the end of the
weekend. Night time tempeatures will be cool Friday night and
Saturday night and patchy frost is possible.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 322 PM EDT Thu Apr 20 2017
Forecast concerns deal with convection this evening and the
potential for frost Friday night and Saturday night.
Latest sfc obs shows low pressure over Lake Michigan with a warm
front extending southeast from near Grand Haven to just south of GRR
to north of Jackson. The cold front stretched from the low south to
near the Il/In border. An area of showers/storms was moving east
across the eastern cwa producing small to medium size hail. This
precipitation will move east of the cwa by 4 pm or so. Then what? It
appears as though we`ll have a couple of hours in which the
atmosphere may be able to destabilize again before the cold front
sweeps east. Latest hi res vis loop shows clearing skies developing
over far southwest Lower Michigan. If this continues the I-94
corridor may see storms redevelop in a couple of hours and these
storms could be strong/severe too. Moderate shear 40-50kts exists
along with 500-1000 j/kg sbcape in the warm sector. The HRRR indeed
shows storms developing over Calhoun county around 5 pm and moving
east by 7 pm. The current severe thunderstorm watch remains in
effect until 8 pm.
Mostly cloudy skies will continue tonight as the upper trough swings
through. Friday will be chilly with highs 45-50. Skies will
gradually clear Friday afternoon setting the stage for cold
temperatures Friday night. We expect temperatures to fall into the
mid 30s both Friday night and Saturday night. Given the abundant low
level moisture in place, frost seems like a real possibility
along/south of I-96; we added patchy frost to the grids both nights.
.LONG TERM...(Sunday through Thursday)
Issued at 322 PM EDT Thu Apr 20 2017
The beginning of this period will have near normal temperatures and
dry weather. However toward the end of this period we get back into
a warm and wet period with thunderstorms likely.
The big picture is similar to yesterday, our East Asian Jet will be
weak early in the period. That allows the upper low over Hudson Bay
to dig just far enough south (southern edge of the upper level
circulation) into the Upper Great Lakes over this coming weekend so
as to blocks the next Pacific system to our south. This will also
allow dry weather with a warming trend early next week for Southwest
Michigan.
By early next week the East Asian jet feature comes back across most
of the Pacific and that digs a western trough. Over time that trough
slowly moves inland enough to bring showers and thunderstorms with
warmer temperatures to this area by Wednesday. This will be just
the begging of an extend wet period that will likely last more than
a week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 738 PM EDT Thu Apr 20 2017
Most of the region was VFR behind the thunderstorms, but some
areas across Central Lower still was seeing IFR conditions.
The ceilings will trend down overnight, with MVFR, fuel alternate
ceilings developing. At this point expect there will be enough
wind to help keep ceilings from falling into the IFR range.
Into Friday morning the ceilings will lift, expecting a return to
VFR by the 14-17Z time frame. The VFR should continue for the rest
of the day.
WNW winds will continue at 15 to 20 knots through the next 24
hours.
&&
.MARINE...
Issued at 322 PM EDT Thu Apr 20 2017
No changes to the headline. Waves will slowly diminish Friday as
high pressure builds over the lake.
&&
.HYDROLOGY...
Issued at 1142 AM EDT Thu Apr 20 2017
Thursday morning rain totals surpassed 1 inch in Mason, Ottawa,
and northern Kent counties. Generally two thirds of an inch fell
upstream of Croton and one third fell upstream of Evart.
Expecting only a slight additional rise at Evart, while Croton
could reach bankfull on Friday. Looking Glass and Sycamore avoided
the heaviest rain while Maple caught some of it. While flood
stage being reached is not the most likely scenario, Looking Glass
appears to be the most vulnerable of all the rivers if it gets
repeated storms Thursday afternoon. Fortunately, dry weather is
expected Friday into early next week.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 6 PM EDT Friday for LMZ844>849.
&&
$$
SYNOPSIS...04
SHORT TERM...04
LONG TERM...WDM
AVIATION...JK
HYDROLOGY...CAS
MARINE...04
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
947 PM EDT Thu Apr 20 2017
.SYNOPSIS...
An unsettled pattern will continue as a front stalls over our area,
with showers and thunderstorms possible each afternoon through the
weekend. A low pressure system will exit the area Sunday, with the
area drying out next week.
&&
.NEAR TERM /THROUGH FRIDAY/...
Evening Update...The area remains under broad high pressure while
areas of weak h5 energy traverse a flat ulvl ridge. This has
maintained a couple -shra across the far wrn zones. Expect this
activity to continue to wane during the overnight. Recent obs show
tdd/s ranging from 5-10 degrees F across FA. Think most locales will
struggle to reach crossover temps and llvl vert change of humidity
will remain negative per HRRR soundings overnight. Thus...not
anticipating much of a early morning fg threat outside of the NC mtn
valleys and fthills where most of the measurable precip occurred the
past 12 hrs.
730 PM Update...The fcst is in good shape. Conv activity continues
to wane due to loss of sfc heating...so adj pops down mainly over
the NC mtns. Expect mlvl debris clouds to hang around in weakening
flow with passing Ci thru most of the evening. Temps and td/s are
right on track.
500 PM Update...Made some minor tweaks to the hr/ly temps as the mtn
valleys are running about 5-7 degrees below the fcst curve. The
tstms developing are remaining quite shallow and short-lived
associated with a relatively weak passing h5 wave. Not anticipating
much more coverage or intensification thru the next update.
As of 230 PM EDT Thursday: The pattern aloft features weak ridging
across the southeast while split flow yields a closed northern
stream low over the Great Lakes, while another trof moves through
the southern stream atop the Desert Southwest. At the surface,
subtropical ridging dominates over the southeast leading to deep
ridging, while a cold front drives eastward out of the Plains into
the mid MS and OH River Valleys. Closer to home, ample diurnal
heating has allowed for modest instability, upwards of 1000j/kg
over the NC/GA and SC mtn regions, while tapering down to around
500j/kg eastward over the Piedmont. With that, any weaker CIN has
eroded, or continues to erode atop the mtns/escarpment as convection
prevails, while any CIN continues to hold for points east. Guidance
tends to favor continued growth of coverage through the afternoon as
heating peaks, with any mtn convection propagating slowly eastward
along the mean steering flow aloft. This warrants low likely to
high chances pops for the mtns through the afternoon, topping out at
high chances eastward across the northern NC Piedmont. Points south
into CLT metro as well as the I85 corridor regions of SC/GA will
be under the influence of the strongest CIN as mentioned above,
thus only slight chance pops were featured. Any convection should
remain below severe limits as mid lvl lapse rates are rather poor,
therefore only garden variety tsra is expected.
Pop will lower into the overnight hours as diurnal heating induced
instability wains, thus leading to non mentionable pops by NLT
midnight. Convective debris spread about the region will erode
with time yielding mostly clear skies, however with the exception
of the mtn valleys where low stratus is possible. Overall, not
expecting widespread fog issues tonight as Td depressions should
remain large enough to negate saturation, yet locations that
experience rainfall today/tonight will have a non zero chance of
patchy fog, especially in the aforementioned mtn valleys.
Otherwise for Friday, despite height falls aloft, H5 flow will
develop a more swly pattern therefore yielding warmer temperatures
through a deep layer. With that, guidance favors even poorer lapse
rates and thus less instability on Friday in the warm sector ahead
of the front, which should remain north of the fcst area through
the remainder of the the period. However, the fcst will still
feature healthy pops across the mtns, with near climo pops over
the lower terrain. Temperatures on Friday will be quite warm,
generally upper 60s to mid/upper 70s over the mtns, while reaching
into the mid 80s across the Piedmont amidst partly sunny skies.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 130 PM Thursday: A split flow regime will be in place across
the eastern Conus through the short term period, with an upper low
expected to drift from the mid-Mississippi Valley into the southeast
coastal states from Fri evening into Monday. There is some
controversy as to the location of an associated frontal zone at the
start of the period, as the NAM and a majority of mesoscale guidance
tends to keep the boundary north and west of our forecast area,
while the global models generally depict it as having moved into the
area by Saturday evening. Considering the orientation of the upper
flow pattern, the NAM and its cohorts probably have the right idea,
as I don`t see any mechanism, other than perhaps organized
convective outflow that would give the boundary a southward push
prior to Saturday night. (In fact, even the global models tend to
retreat the boundary north of our on Saturday). As such, we expect
convection to remain scattered and to be primarily driven by the
diurnal heating cycle through the day Saturday. Instability will be
adequate for strong updrafts Sat afternoon/evening, but shear won`t
support anything much more organized than perhaps a couple of
mesoscale clusters, so a severe weather threat exists, but appears
to be marginal.
The forecast gets a bit more interesting (and uncertain) beginning
Sat night and continuing through Sunday, as deep layer forcing
increases across the region, and the front begins sweeping across
the TN Valley and the southern Appalachians. Meanwhile, high
pressure building into the northeast Conus in the wake of a
transient northern stream short wave trough is expected to establish
cold air damming across the Eastern Seaboard Sat morning through
Sunday. As usual, the NAM is by far the most aggressive in the
timing and southward extent of the cool air wedge, although the
global models are also trending in the direction of developing CAD
over our area, albeit keeping it primarily confined to western NC.
Pops increase to likely to categorical across the area during this
time, but uncertainty regarding the surface pattern (including the
location of potential surface cyclogenesis) means there is also
considerable uncertainty regarding the degree of any severe weather
threat for the late weekend. It`s also worth noting that the NAM is
much more intense and slower with the upper low track, digging it
farther to the south than the global models. The result is a strong
upslope/ upglide response/heavy rain signal over the cold pool by
the end of the day Sunday. The NAM does have a habit of over-
intensifying upper lows, so this evolution seems dubious, but that`s
one more potential scenario to ponder.
Temps will remain much above normal through at least Saturday, then
are expected to fall to near or even a few degrees below climo
Sunday, as cold air damming will likely become established across at
least part of the forecast area.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 200 PM EDT Thursday: Medium range picks up 12Z Monday AM just
as the the surface low is sliding off the Atlantic coast to exit our
area. The upper low may linger over the Carolinas for another 24
hours or so with Atlantic moisture wrapping around the back side in
the cyclonic flow...so pops were tapered off gradually through
Monday PM. A wedge of surface high pressure will build over the
Appalachians in the wake of the surface low late Monday and through
Tuesday. The parent high is progressive and will shift off the
northeast coast by late Tuesday, allowing the surface ridge to break
down as another low pressure system sweeps across the central
plains. Global models are showing different solutions as far as the
track of this low, though they both come to a similar conclusion as
far as sensible weather. The ECMWF, with the more southerly low
track, brings a surface cold front through the area Wednesday
afternoon, though anemic deep layer moisture greatly limits any QPF
response. The more amplified GFS swings the low up towards the
northeast, sweeping the front northward before it can make it into
our area. Though the upper flow amplifies considerably towards the
end of next week, any issues should remain past the end of the
current extended forecast. A slight increase in cloud cover is the
only sensible weather advertised through the end of the medium range
on Thursday. Temperatures will begin the period near average and
gradually rise to above average through Thursday.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
At KCLT and Elsewhere: Mainly VFR conds thru the period. The pattern
doesn`t change much over the next 18 hrs with a broad sfc high
engulfing the region. Ongoing isol -shra/tstms will continue to
diminish thru 06z...with mainly debris clouds persisting thru
daybreak. KHKY and KAVL could see early morning VSBY
restrictions...likely remaining in the MVFR range. A weak cold
front works in and stalls near the NC/SC line aft 18z which will
spawn sct -shra/tstms. Thus...have prob30 thunder for all sites
except KAND late in the period.
Outlook: Another backdoor cold front is expected to settle over the
fcst area this weekend, with restrictions and precipitation likely.
Confidence Table...
01-07Z 07-13Z 13-19Z 19-00Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 100% High 100% High 100% High 100%
KHKY High 100% High 93% High 100% High 100%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 100% High 100% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...LEV
NEAR TERM...CDG/SBK
SHORT TERM...JDL
LONG TERM...LEV
AVIATION...SBK
Area Forecast Discussion
National Weather Service Huntsville AL
943 PM CDT Thu Apr 20 2017
.NEAR TERM...(Rest of tonight)
Issued at 943 PM CDT Thu Apr 20 2017
GOES-16 imagery shows a band of mostly mid-level clouds gradually
drifting into the HUN CWFA from the north, while area radars show
showers rapidly diminishing as they approach the TN-AL state line. A
few showers have been persisting along the AL-GA state line but these
are drifting into Georgia. Area temperatures are mostly in the low-
mid 70s with a few cooler exceptions.
Short-range and convection-allowing models are in solid agreement on
keeping the area dry until after 09-10Z, although the HRRR does bring
in a stray shower or two at times along the NW state lines. Forecast
PoPs will be tweaked but the general trends will stay the same with
20-30% mainly north and west of Huntsville. Sky cover will need to
be adjusted slightly to match the approaching cloud bands mentioned
above. Temperatures are on track to reach the low-mid 60s, although
some minor adjustments may be needed for cooler spots. A little bit
of fog is possible where rainfall occurred earlier (as evidenced by
the Scottsboro observation) but it should not be widespread.
.SHORT TERM...(Friday through Saturday)
Issued at 106 PM CDT Thu Apr 20 2017
Forecast gets a bit interesting beginning on Friday. The aforementioned
frontal boundary or perhaps a prefrontal trough/outflow may help
spark convection across the area on Friday. Model progs show a
moderately unstable airmass with weak shear. With fairly dry air
aloft, expect some slow moving storms with gusty winds and locally
heavy rain the primary concern. Again, given the surface features the
highest pops will be positioned north.
May see another lull in the festivities Friday evening before the
the cold front finally makes its formal approach toward the region.
The 06z/12z model trends have been for a weaker low and more of an
open wave feature to move across on Saturday. In terms of
precipitation and convective potential that would spell a somewhat
downward trend in potential.
The 12z NAM has thrown us a hard curveball with the introduction of
additional northern stream energy into the trough and an eventual
cutoff low by Sunday. Not sure I`m exactly diving into the deep end
with that solution, but either way, the initial surge of energy on
Saturday will place the highest QPF along and north of I-40 to the
Appalachians. Our convective potential will be mostly convergence
driven with the front along with the diurnal forcing. Overall, that
doesn`t look overly impressive but sufficient for high chance to
likely pops. The upper flow does become increasingly divergent late
Saturday/Saturday evening which should help increase precip/QPF
potential. Based on the timing of the front will taper pops from
west to east on Saturday evening with perhaps some lingering showers
behind the front.
.LONG TERM...(Sunday through Wednesday)
Issued at 200 PM CDT Thu Apr 20 2017
There is quite a bit of disagreement between NAM12 and synoptic
models guidance concerning how quickly the surface and associated
upper low push east of Alabama. NAM12 seems to be an outlier and
keeps the surface low much further west. Therefore, it keeps high
precipitation chances over northern Alabama and Southern Middle
Tennessee. The synoptic models move the surface low much further east
into the Carolinas. Since the ECMWF does keep some precipitation
over northeastern Alabama on Sunday (and given how wet the NAM12 is),
forecast reflects Superblend model forecast of isolated to scattered
lingering showers on Sunday (~ 40 percent chance in eastern
counties/20 percent near the AL/MS border).
Even if we do not see as widespread shower activity, cloud cover and
cold air advection will make it seem very cool. Highs in the upper
50s to around 60 degrees will be a far cry from Saturday`s highs
(about a 25-30 degree difference probably). In fact given the 925 mb
temperature values forecast by models the highs on Sunday could even
be a bit cooler than that. By Sunday evening, models move any
lingering precipitation into northeastern Georgia and the Carolinas.
Clouds may not decrease until after midnight, except in locations
west of I-65. This should allow for slightly cooler low temperatures
in the mid to upper 40s in northwestern Alabama around daybreak on
Monday.
With abundant sunshine on Monday, believe highs should rebound into
the lower to mid 70s (925 mb temperatures climbing back into 15-17
degree range). This warming trend will continue as an area of high
pressure continues to hold in place over the Tennessee Valley. Expect
highs to climb back into the lower 80s by Tuesday and could be even
warmer later in the week. A strong storm system develops over the
upper Midwest towards the end of the week, but energy with this
system will remain too far north to affect northern Alabama and
southern middle Tennessee through Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 636 PM CDT Thu Apr 20 2017
VFR conditions are expected (with some confidence) through ~14Z
Friday. Confidence decreases afterward as showers/storms develop
near a cold front sagging into the region. Scattered showers/storms
could impact either KHSV or KMSL after 14Z, but impacts are more
likely after 16-17Z as the front gets closer and heating maximizes.
TAFs include VCTS at that point because details are difficult to
time at this range. Future TAF issuances will hone these details.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...BCC
SHORT TERM...15
LONG TERM...KTW
AVIATION...BCC
For more information please visit our website
at weather.gov/huntsville.
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1047 PM EDT Thu Apr 20 2017
.UPDATE...
Issued at 1047 PM EDT THU APR 20 2017
Only a few showers have popped up across eastern Kentucky thus far
this evening. The general trend in the HRRR has been for less
activity through first part of the overnight, before the cold
front gets closer towards dawn. This seems reasonable given the
current radar trends. As such, have delayed the better POPs later
still. Temperatures have cooled into the mid 60s in the valleys,
while broader valleys and ridges remain in the lower 70s. A modest
ridge/valley split should continue over the next few hours,
before thicker cloud cover moves in and mitigates the differences
a bit more. Updates have been sent.
UPDATE Issued at 631 PM EDT THU APR 20 2017
A broken line of showers and thunderstorms is attempting to make
it in from central Kentucky. Most of this activity is diminishing
as it is heading east, and all of the convection across eastern
Kentucky has dried up, thanks to dew points in the lower to mid
50s, with a few upper 40 degree readings noted. As such, have
delayed the POPs somewhat in the east and kept it dry until the
cold front moves in closer later tonight. Skies have also
thinned, and will allow for a bit of decoupling in the eastern
valleys this evening. Updates have been sent.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 428 PM EDT THU APR 20 2017
Ongoing isolated showers and thunderstorms are expected to continue
to wain during the rest of the afternoon as we await an incoming
cold front overnight. It is along and just ahead of this cold front
that we will find our next best chances for precipitation across the
CWA, including thunderstorm potential. Latest NAM12 forecast
soundings are still showing soundings becoming saturated throughout
the column after 6Z (first in the north and a few hours later in the
south), giving good support for likely to numerous coverage. That
being said, CAPE values aren`t looking that great, generally between
400 and 700 j/kg overnight, with very little llvl wind shear and
moist upper levels that would deter any hail potential. As such,
expect this to be more of a localized heavy rain event, with some
good lightning based on the intensity of the rain...but otherwise
not expecting much in the way of high winds (wind speeds aren`t very
impressive aloft) or hail.
Thunderstorms may intensify slightly during the first half of the
day Friday across the southern CWA as the front continues southward
through the state. As temps warm through the morning with southerly
flow, this will help to boost CAPE values above 1000 j/kg, with LI`s
falling to -4 across the central and southern CWA. Some low level
wind shear will also be present with southerly winds near the
surface and westerly flow in the mid and upper levels. All together,
thunderstorms will likely be more prominent in coverage and strength
tomorrow with some gusty winds and small hail not to be ruled out.
However still think the main threat will be localized heavy rains
and lightning. In the northern CWA the front will have already
passed, so while showers and thunderstorms are still possible, they
will likely be elevated in nature given more northerly flow moving
in at the surface.
By the latter half of the day, the front will have sagged just south
of the state, where it will stall out through Friday night. This
will keep enough moisture over the region to promote continued
widespread precipitation. However, with northerly flow in the low
levels on the north side of the front, we will not see much in the
way of instability or thunderstorm potential. As such, have
thunderstorms decreasing Friday evening, and kept out all mention of
thunder from Friday night through Saturday morning. While
temperatures should still reach the upper 60s to mid 70s during the
day Friday despite cloud cover and precip in place, northerly winds
behind the system will cool the airmass down substantially, dropping
to the upper 40s to mid 50s for Saturday morning lows (coolest in
the north).
.LONG TERM...(Saturday through Thursday)
Issued at 430 PM EDT THU APR 20 2017
The period will begin with a trough extending from Quebec southwest
into the mid MS Valley and lower MO Valley region with riding
extending from parts of the Eastern Pacific north into the Western
Conus. At the surface, a wave of low pressure is expected to track
along a boundary that will have stalled out to the south of the
region during the near term period. This low will slowly track
toward the Carolinas through Sunday evening while the southwestern
end of the upper trough closes off into an upper level low and moves
across the Lower OH Valley and into the TN Valley and southern
Appalachians through the weekend. This upper low should meander into
the Southeast and finally off the southeast coast for Monday into
Tuesday. In its wake, an upper level ridge will build into the
Southern Plains and lower OH Valley Sunday night into Monday.
However, this ridge will dampen beyond Monday as a broad trough
develops from the Western Conus into the Central Conus through
midweek. Late in the period, a shortwave trough moving from the
Plains into the Great Lakes should generally track northwest of the
area with an associated surface boundary briefly approaching the OH
Valley at midweek. However, another shortwave moving through the
trough should lead to cyclogenesis to the Lee of the Rockies late in
the period with the low tracking toward the mid MS Valley late in
the period with the boundary returning north as a warm front.
Unsettled weather should persist over the weekend, with a steadier
rain or showers on Saturday as the shortwave approaches and surface
low tracks to the south. Limited instability in the south could lead
to isolated thunderstorms, but most locations should receive a good
soaking rain from Saturday into Saturday evening. Shower chances
will linger into the day on Sunday and possibly even Sunday evening
mainly in the southeast as the upper low moves across the area.
High pressure will bring drier weather and clearing skies by late
Sunday night and persisting into Tuesday evening. With the shortwave
passing northwest at midweek and the cold front dropping toward the
OH Valley isolated convection will be possible on Tuesday night or
early on Wednesday in the far north. At the next system nears late
in the period, additional showers and thunderstorms will be
possible. However, higher chances are possible after the period.
High temperatures and average temperatures will be below normal over
the weekend. However, with more sunshine and high pressure in place
high temperatures should moderate to above normal levels by Tuesday
through Thursday. The pattern from early to the middle of next week
should support rather strong nocturnal inversions and valley low
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 751 PM EDT THU APR 20 2017
An approaching cold front will bring scattered to numerous showers
and thunderstorms to the area overnight into Friday from northwest
to southeast. VFR conditions will generally prevail through 06z,
and then ceilings will lower down to MVFR/IFR from northwest to
southeast as the boundary sags southeast into the area early
Friday morning. The front will linger across southeastern Kentucky
during the day on Friday, with additional convection firing up,
likely sustaining the MVFR ceilings. Some ceiling improvement
looks to take place from the north by Friday afternoon. Southwest
winds at 5 to 10 kts, with some gusts to around 15 kts, through
early this evening, will gradually shift to the west and northwest
through Friday.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GEOGERIAN
SHORT TERM...JMW
LONG TERM...JP
AVIATION...GEOGERIAN
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
632 PM CDT Thu Apr 20 2017
.SHORT TERM...(This evening through Friday)
Issued at 325 PM CDT Thu Apr 20 2017
All models have shifted the storm track toward the wrn solns shown
by previous runs of the GFS and ECM. Thus measurable rainfall will
likely be along and west of a line from KAIA-KLBF-KLXN with amounts
increasing west. Dry air being drawn in from the east could shift
the rain line even farther west and the 18z RAP suggests the good
rain could be as far west as the Front Range in COLO. The series of
storms earlier this week appears to have taken a toll on moisture.
The shift west will delay the onset of rainfall across Southwest
Nebraska until late tonight and Friday morning.
Highs Friday remain in the 50s and widespread cloud cover is
expected.
.LONG TERM...(Friday night through Thursday)
Issued at 325 PM CDT Thu Apr 20 2017
Pacific high pressure moves overhead Saturday and another storm
system will enter the Nrn High plains Sunday. The models continue to
advertise a dry south wind Sunday increasing to 20 to 25 mph in the
afternoon. A fairly strong cold front will move off the Texas coast
and shut down moisture return.
Another Pacific cold front sweeps through Nebraska Monday. Modest
moisture return develops and rain chances are in the forecast
Tuesday through Thursday.
This morning`s run of the ECM...GFS...GEF and GEM models suggests a
series of disturbances will move through the Cntl Plains. This is a
favorable pattern for rain given that a stationary front should set
up on the cntl High plains which would draw moisture west for
thunderstorm initiation. The forecast is for showers with highs in
the 50s and 60s. The GFS and ECM suggest lapse rates could steepen
sufficiently across Wrn Neb for thunderstorms and later forecasts
will address this feature.
The WPC rainfall forecast has responded by wetting the region with a
1/2 to 3/4 of an inch of rainfall and the CPC has outlooked parts of
Neb for heavy rainfall Tuesday and Wednesday. The CPC outlook
suggests locally higher rainfall amounts could develop. POPs have
been limited to 30 to 50 percent given the uncertainty of the storm
tracks.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 628 PM CDT Thu Apr 20 2017
Visual flight rules expected tonight with light easterly winds
under 10kts over western Nebraska. Increasing high clouds late
tonight as showers try to move in from northeast Colorado. MVFR
cigs expected over southwest Nebraska towards sunrise with VCSH
showers being carried at KLBF.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Power
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
926 PM EDT Thu Apr 20 2017
.SYNOPSIS...
A cold front will drop into the Mid Atlantic Friday. Weak high
pressure builds over the area Friday night before low pressure
impacts the area Saturday night and Sunday.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Thunderstorms were able to feed off of steep low-level lapse
rates, decent CAPE (around 1000 j/kg), and 30-40 kt bulk shear
to organize into a line that crossed the forecast area late this
afternoon and evening. These storms entering a slightly more
hostile airmass (less CAPE and a bit of CIN), likely aided by
nightfall and the loss of daytime heating. Will be clearing the
forecast area by 10-11 pm. Database will follow suit.
The next area of thunderstorms are back in northwestern
Pennsylvania. This area pre-frontal as well. There should be a
weakening trend overnight, but the HRRR suggests echoes will
approach the northwestern corner of the forecast area after
midnight. Will have chance PoPs returning at that time. Most
likely just showers, but with a little lingering MUCAPE,
adequate shear and lapse rates...wouldn`t rule out an elevated
rumble.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
Cold front will push through the area Friday. Still some
uncertainty with regards to timing...which will have a large
impact on sensible weather across the area. Thunderstorms are
expected along/ahead of the front. A few of these storms could
become marginally severe...as instability increases compared to
today (e.g., MLCAPE ~1000-1400 J/kg). Latest SPC Day 2 Marginal
Severe risk was shifted further north into our area...which
makes sense considering the timing uncertainty of the frontal
passage and thus how much destabilization can occur. While
slightly better than today...strong wind field remains to the
north of the area...which results in only marginally favorable
shear profiles for storm organization.
Front will stall to our south late Friday into Saturday, leaving
us with extensive cloud cover as we remain in the cool sector.
Low pressure will approach the area from the SW during the day
Saturday...allowing for overrunning precipitation to develop
over the area during the afternoon and through the overnight.
Uncertainty remains in regards to how far north the greatest
QPF sets up...latest trends in the guidance continue to push the
highest totals south...keeping them over central VA. 1-2 inches
of rain are possible across central VA...with generally less
than an inch expected north of I-66.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
Low pressure at the surface will likely sink south of the area
Sunday as the upper level low forcing it becomes cutoff from the
westerlies. The low may meander off the coast for a couple days with
high pressure building to the north. This would result in a cool and
dreary pattern into the first half of next week.
By the middle of next week, the low should move away and high
pressure rebuilds to the southeast of the area, resulting in
southwesterly flow and a marked increase in temperatures.
&&
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
Thunderstorms over BWI/MTN at this time. Otherwise, all activity
has pushed east of the area. In metro Baltimore, activity will
push east by 10pm. No additional storms anticipated tonight. Fog
is another story. There is now sufficient low level moisture.
Will be adding MVFR to TAFs shortly, and will reassess to see if
IFR warranted. There is certainly a chance at that.
Thunderstorms with gusty winds are possible Friday...with flight
restrictions possible in any stronger thunderstorms...VFR
expected outside of thunderstorm activity.
Low clouds and periods of rain could impact the terminals
Saturday afternoon through Sunday morning...with sub-VFR
possible.
Sub-VFR likely in low clouds/onshore flow (generally
northeasterly around 10 knots) Sunday into Monday.
&&
.MARINE...
Weakening showers and thunderstorms reaching the Bay at this
hour. We believe that gusts will be under 30 kt, but are
monitoring in case additional Marine Warning will be warranted.
A cold front will cross the waters Friday. Additional
showers/storms...some with gusty winds...will again be a
consideration. All should monitor in case another round of
Marine Warnings are issued.
Rain is expected for the waters Saturday.
Generally sub-SCA conditions expected Saturday night and Sunday. SCA
conditions possible Monday with increasing northeasterly flow.
Northeasterly flow between high pressure to the north and
low pressure to the south may push gusts into Small Craft Advisory
territory early next week.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.
&&
$$
SYNOPSIS...MSE
NEAR TERM...HTS
SHORT TERM...MSE
LONG TERM...DFH
AVIATION...HTS/MSE/DFH
MARINE...HTS/MSE/DFH
Area Forecast Discussion
National Weather Service Memphis TN
941 PM CDT Thu Apr 20 2017
.UPDATE...
A few storms continue across the northern portion of the CWA this
evening, in proximity to the surface cold front that will be
moving slowly south overnight. However, with the loss of surface
heating, waning instability and an overall increase in convective
inhibition should limit the intensity of any thunderstorms that
develop. The greatest rain chances will be north of I-40 during
the overnight hours. On Friday, showers and thunderstorms will
increase in coverage by mid/late morning as the boundary layer
destabilizes. There will be sufficient shear and instability to
support organized storms, but forecast parameters don`t jump off
the chart. Abundant cloud cover and scattered to numerous showers
and thunderstorms may limit the amount of instability that is
realized. That said, a few strong to severe storms are certainly
possible. The marginal risk continues for nearly all of the Mid-
South to cover this potential.
There is also a risk for locally heavy rainfall across the CWA.
The deep-layer shear vector is forecast to parallel the low-level
boundary orientation, enhancing the potential for training
storms. Precipitable water values are progged to be on the order
of 1.2 to 1.5 inches. While not extreme, this is roughly 150% of
normal for mid April.
PoPs were adjusted during the overnight period, focused more north
of the TN/MS line. Otherwise, tweaks were made to other forecast
parameters were minor.
Johnson
&&
.PREV DISCUSSION... /issued 312 PM CDT Thu Apr 20 2017/
Skies remain partly cloudy over much of the forecast area this
afternoon with temperatures ranging from the mid 70s to mid 80s.
Scattered showers and thunderstorms were found over portions of
northwest Mississippi and much of west Tennessee at this time. A
cold front currently extends from northwest Indiana through
southeast Missouri and into southwest Texas.
The front will drop south into northern sections of the forecast
area tonight. As it does, more thunderstorms are expected over the
region tonight. There is a marginal risk of severe weather over
northern portions of the forecast area with large hail and
damaging winds as the main threat. Temperatures will remain on
the warm side with lows Friday morning in the low to mid 60s. The
cold front will continue to push slowly south into north
Mississippi on Friday with more thunderstorms expected. There will
be a marginal risk of severe weather during the day on Friday over
the entire forecast area with large hail and damaging winds as the
main threats. The air will be a little cooler behind the front so
temperatures will vary some depending on where the front is in
the afternoon with highs ranging from the upper 60s to lower 80s.
By Friday night, low pressure will develop along the front over
north Texas and track into northeast Arkansas by Saturday morning.
This will lift the cold front back north as a warm front Friday
night with more thunderstorms expected. There will still be a
marginal threat of severe weather Friday night as well. Rainfall
could become heavy at times starting Friday night and continuing
into Saturday. Temperatures will remain a little cooler than the
past few days with lows Saturday morning in the mid 50s to mid
60s. The surface low will track through the region on Saturday
bringing a cold front along with it. This will mean more
thunderstorms are expected on Saturday with some severe storms
still possible during the day. Temperatures will cooler on
Saturday with highs in the lower 60s to mid 70s. The cold front
will be moving out of the forecast area by Saturday night with
rain starting to end from west to east. Temperatures will be on
the cool side with lows Sunday morning from the mid 40s to lower
50s.
High pressure will start to build into the region on Sunday
bringing a period of dry weather for Sunday through Wednesday.
Temperatures will be on the cool side Sunday but gradually warm
for Monday through Wednesday. By Wednesday night, a new storm
system will be moving into the central plains bringing more
thunderstorms to the region for Wednesday night and next Thursday.
ARS
&&
.AVIATION...
00Z TAF Set
Convection along and east of the MS River is quickly dying due to
the loss of daytime heating. Meanwhile, convection ahead of an
approaching front has begun to push into NE AR. Models indicate
KJBR could be impacted around 2Z. Models diverge on what exactly
happens with the convection overnight. The NAM keeps most of the
activity across NE AR while the RAP bring convection south into
the Memphis Metro area. For now have leaned toward the NAM. Thus
have kept vicinity and tempo wording in KJBR through 10Z. Expect
redevelopment of convection to begin along the front around 13-15Z
near Memphis. Low clouds and VSBYS will likely be confined to the
convection through at least sunrise except for KMKL where some fog
may develop due to rain that occurred today. S winds around 6-8KTS
will occur ahead of the front. Winds will turn around to the N-NE
behind the front.
KRM
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Nashville TN
850 PM CDT Thu Apr 20 2017
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Cold front currently located from central IL southwestward across
central MO. Mosaic depicts an area of shower and tstm activity
just south of the boundary. Models in agreement with moving the
front into our area by 12z. However, forcing and the area of
higher moisture depth are both expected to decrease with time.
Thus, I am in agreement with both ISC grids and Hrrr data which
suggests that the greatest pops will be oriented from north to
south after midnight. Will therefore go ahead and leave likely
pops across the north but lower the southern pops. Otw,
overnight lows of 60 to 65 still looks reasonable. Update out
shortly.
&&
.AVIATION...
00Z TAF DISCUSSION.
Uncertain terminal forecasts thru 21/24Z. Several adms possible,
especially 21/09Z-21/24Z. Divergent model solutions, took mean.
Sfc front near BNA 21/12Z. South of CSV after 21/18Z. Initial
zonal upper level pattern becoming progressively swly thru
21/24Z. Can not rule out VFR VCSH all terminals thru 21/09Z.
MVFR vsbys with increasing chances of light to mdt shwrs/tstms
thru 21/24Z with predominate MVFR ceilings. Veering sfc winds SW
to NW CKV per most post frontal, with persistent SW sfc winds
BNA/CKV. 5kt-10kt speed range, 10kt-15kt CSV 21/19Z-21/24Z.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......21
AVIATION........31
The remainder of the short term forecast discussion is unchanged...
An upper level trough will push the upper ridge further east Friday
night. A surface front will reach the central Oregon coast early
Saturday morning, but dry weather and east winds will persist to the
north. Clouds and rain will return to areas south of Salem Saturday
morning, but north of Salem may stay dry and possibly even be sunny
in spots til close to noon. By the afternoon cloudy skies and rain
will return to the entire Portland forecast area. The rain will be
rather light, and the front will be out of the area early Saturday
evening. An upper trough will maintain post-frontal showers through
Sunday with snow levels settling close to the Cascade Passes (around
4500 feet). ~TJ
.LONG TERM...No Changes. Previous discussion follows...Sunday night
through Thursday...Next week will be marked by a continuation of a
cool and wet weather pattern. A series of fronts will move across the
region bringing periods of steady stratiform rain, followed by
abundant showers in the onshore flow behind each disturbance.
Forecast models remain in fairly good agreement with respect to the
overall pattern through about Tuesday, when they suggest a low
pressure system may develop and move north through the coastal
waters. Depending on the orientation and track of this disturbance,
breezy conditions are possible later Tuesday across the coastal areas
and in the Coast Range. Showers may begin to taper off briefly late
Wednesday as models suggests weak shortwave ridging moves over the
region, but weakly onshore flow aloft may maintain precipitation in
the higher terrain. Forecast models do begin to diverge a bit for the
second half of the week, but the biggest net disagreement is more
regarding the timing of brief dry periods. The GFS would suggest a
bit of a longer dry period with flow turning more northwesterly,
compared to the more zonal flow pattern in the ECMWF. However, plenty
of spread among NAEFS members keep at least chance PoPs in the
forecast through each 12-hour period in the extended. Likewise,
temperatures next week look to remain several degrees below seasonal
normals. Cullen
&&
.AVIATION...Any lingering showers will come to an end later this
evening, with skies clearing overnight. Expect predominately VFR
conditions the next 24 hours. However, there could be a brief
period of patchy fog or low stratus between 12Z and 16Z due to
light winds, mostly clear skies and lingering surface moisture.
Any fog or low stratus that develops Fri morning will burn off
quickly, yielding mostly clear skies through Fri night.
KPDX AND APPROACHES...Predominately VFR the next 24 hours. A few
hours of patchy fog or low stratus possible between 12Z and 16Z.
/64
&&
.MARINE...Winds will be generally 15 kt or less through Fri
morning as high pres builds over the coastal waters. The high
pres will move inland during the day Fri, which will allow
offshore winds to develop late. Models continue to suggest that
the offshore winds may reach borderline advisory speeds late in
the afternoon and into Fri night, but confidence is low. A
weakening occluded front will move across the waters Sat,
bringing a period of solid small craft advisory southerly winds
and possibly even some brief low-end gales. A weak trough will
move across on Sun, but expect winds to remain 20 kt or less. A
progressive weather pattern appears to set up over the region for
most of next week, with numerous frontal systems modeled to move
across the waters.
Seas are currently around 8 ft this evening and will continue to
gradually subside, falling to around 5 ft by Fri afternoon. The
Sat frontal system will likely push seas back around 10 ft for a
short period. They should then drop back below 10 ft for Sun into
early next week. /64/Pyle
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&
$$
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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. The area is
commonly referred to as the forecast area.
Area Forecast Discussion
National Weather Service Charleston WV
1018 PM EDT Thu Apr 20 2017
.SYNOPSIS...
More widespread storms late tonight as a cold front crosses the
region. Front lifts back north late Friday night/Saturday.
System exits Sunday. Dry early next week.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 1015 PM Thursday...
Updated POPs based on current radar, then blended toward the
HRRR and RAP through the night. Still showing a line of likely
POPs moving through overnight. Also updated temperatures based
on current obs and trends.
As of 230 PM Thursday...
Surface boundary with associated surface trough acting as a
trigger for some convective development this afternoon with a
thin line of thunderstorms extending from just south of KPKB to
KBLF. Also still seeing some isold redevelopment in eastern KY.
Will keep at least isold POPs through this evening with higher
values to the east. Front approaches from the west tracking
through from the 06Z-12Z timeframe. Have not strayed far from
inherited forecast in terms of timing the line that will be
associated with front as it moves through. For temps...went
with model blend with generous nod toward inherited forecast.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 245 PM Thursday...
Focus remains on the front lifting back to the north, providing
a focus for an extended period of showers and storms through
Saturday night. GFS is more generous in terms of holding the
higher PWATS through Saturday into Saturday night, which would
lend to higher QPF, whereas the NAM is a bit quicker in pulling
the mid level moisture out of the area. Regardless, will need to
watch areas for repetitive rounds of showers and storms once the
frontogenetic zone lifts back north into our CWA, as highlighted
by the update to the HWO this morning. Ground conditions are
currently still being set up with convection today and the cold
front tonight.
Lingering on the colder side of the boundary keeps temperatures
below normal for much of the CWA in the short term.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 245 PM Thursday...
Long range models now strengthening the short wave trough
affecting the Great Lakes and its southern extent of rain into
the northern half of the CWA. However, blended guidance still
keeps not only the values of these POPs low, but the area
remains contained as well. Until then, drier conditions prevail
for the beginning of the week as temperatures rebound again
under increasing thicknesses and 850mb temperatures.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
As of 715 PM Thursday...
Tricky forecast with multiple lines of broken thunderstorms
approaching from the west. Think there will be some
consolidation of these, but still rather difficult to time out
restrictions to any individual airport. Did not include IFR
right off the bat due to broken nature of the lines, but am
fairly confident that IFR tempos will be needed as things
progress. Cold front will sink through overnight with showers
and thunderstorms lingering across the south much of Friday.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z SATURDAY...
FORECAST CONFIDENCE: Medium.
ALTERNATE SCENARIOS: Brief MVFR and maybe IFR could occur with
showers and thunderstorms tonight and tomorrow.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE FRI 04/21/17
UTC 1HRLY 00 01 02 03 04 05 06 07 08 09 10 11
EDT 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07
CRW CONSISTENCY H H H H H H M M M M H M
HTS CONSISTENCY H H H H H H M L L H H L
BKW CONSISTENCY H H H H H H H H H H M M
EKN CONSISTENCY H H H H H H H M H H H M
PKB CONSISTENCY H H H H H M M L M H H M
CKB CONSISTENCY H H H H H H M M H L H M
AFTER 00Z SATURDAY...
IFR possible Saturday into Sunday with another wave of low pressure.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...None.
OH...None.
KY...None.
VA...None.
&&
$$
SYNOPSIS...KMC/26
NEAR TERM...KMC/MZ
SHORT TERM...26
LONG TERM...26
AVIATION...MZ
Area Forecast Discussion
National Weather Service Blacksburg VA
955 PM EDT Thu Apr 20 2017
.SYNOPSIS...
High pressure over the Southeast States will move east and weaken
this evening into tonight. A cold front will approach from the west
tonight and enter the mountains Friday morning. This front will
stall near the NC/VA border Saturday, with a secondary low moving
across the area Sunday. This will keep us in a wetter pattern
through the weekend.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 955 PM EDT Thursday...Comparatively quieter weather at
this point in the evening under weak/relative surface ridge.
Across a large part of the Piedmont, current T/Td spreads are
rather narrow with dewpoints in the low 60s and winds being
light to calm. There`s been periods of mist and fog that have
developed in some locales, such as Farmville and into central
and eastern Campbell County. I suspect that areal coverage may
expand further as we progress into the overnight in the Piedmont
and Southside given relatively wet soil and little significant
change in dewpoints projected through overnight. It`s slightly
drier along and west of the Blue Ridge, and so I kept this
confined to the NC foothills, Piedmont and Southside areas. Not
thinking dense fog but enough to cause some reduced visibility
in patchy areas. Expect a continued dry forecast until after 2
am when threat of showers begins to intrude into our far western
counties from a pre-frontal trough in the eastern Ohio Valley.
Previous near term discussion issued at 400 PM follows...
Scattered showers and thunderstorms have develop this afternoon in
the unstable warm airmass. Surface boundary with associated surface
trough acting as a trigger for storms with best coverage in
Southeast West Virginia. The combination of orographic lift and
instability creating convection along the Blue ridge mountains. The
Day One convective outlook places the threat for severe weather to
our northwest with the better instability closer to the cold front.
An isolated strong storm may be possible this afternoon into this
evening. Shaped pops this afternoon into tonight towards a blend of
the HRRR and NAM.
With the loss of solar heating this evening, expect showers and
thunderstorms to dissipate. A cold front in the Ohio Valley will
move east tonight and reach the Central Appalachians and Mid-MS
Valley by Friday morning. Ahead and along the cold front, scattered
showers and isolated thunderstorms will move into the mountains
Friday morning. Low temperature tonight will range from the mid 50s
in the mountains to the lower 60s in the Piedmont.
A wet Friday is expected for our region as a cold front pushes east
with scattered showers and thunderstorms. The Day 2 Convective
Outlook has place the entire forecast area in a marginal threat for
severe weather Friday. There is a severe weather potential with
possible thunderstorm activity along/ahead of the southward
advancing surface cold front. The main threat is for damaging winds
and hail. High temperatures Friday will vary from the mid 60s in the
northwest mountains to the mid 80s in the Piedmont.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 400 PM EDT Thursday...
The need for an umbrella or a raincoat may be an understatement
this weekend. Potential for 1 to 1.5 inches of rain is high,
with moderate confidence for 2 to 2.5 inches of rain from Friday
night through Sunday night inclusive.
A stalled surface front is forecast to bisect the Mid-Atlantic
Region through the weekend, extending from the North Carolina
Coast Saturday into an area of low Pressure over western
Tennessee. This area of low pressure is forecast to slowly move
east along the stalled front providing a focus for occasional
showers and thunderstorms which may morph into an all out period
of rain or periods of rain at times through the weekend.
Our forecast area is expected to be on the cooler, north side of
the front, thus resulting in cooler than normal temperatures,
winds primarily out of the north or northeast. The only
exception may be Saturday when strong southwest wind flow aloft
across the mountains battles with the impinging northeast low
level flow coming in from northern WV/VA resulting in
potentially warmer conditions for the higher elevations and into
far southwestern VA and NC. The more dense cooler air will
eventually win out by Saturday night with the entire CWA
succumbing to the cooler temperatures by Sunday.
The severe weather threat at the present time looks marginal
per abundant cloud cover which is forecast to limit
instability. Of greater concern will be the potential for
runoff issues per increasing confidence for repetitive rainfall
and long duration which could linger into Monday. Model Median
forecasts for some of the Rivers, such as the Dan River, are
indicating at least 50 percent chance for area rivers to
experience a rise of half bank to three quarters bank full, and
a 30 percent chance for near bankfull or minor flooding. This
introduces the potential need for a Flood threat headline at
some point for the weekend, and will continue to highlight this
in the Hazardous Weather Outlook. Folks that have plans that
involve area streams and rivers this weekend should pay close
attention to the forecast and potential changes which may occur
with respect to the river stage forecasts.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 850 PM EDT Thursday...
Recent model runs of the 18Z GFS and 12Z ECMWF still trend towards a
wetter Monday. The exiting low pressure system will be slower than
previously thought. Further analysis has shown a gradual increase in
precipitation chances from the Piedmont to the Blue Ridge Mountains.
Southeastern West Virginia and neighboring Virginia counties still
show little, if any, chance of precipitation. While observing the
models, neighboring forecast offices` trends for higher
precipitation chances were also considered.
As of 420 PM EDT Thursday...
Low pressure will linger along the Mid Atlantic coast Monday,
the models trending slower with its departure. This suggests
Monday may turn out to be a wetter day than currently forecast
with potential for clouds to linger into Tuesday before any sort
of drying trend becomes established. For now will trend pops
upward for Monday and hang onto some cloud cover for Tuesday.
With an east or northeast wind, temperatures will be slow to
recover until the sun returns for mid Week.
A dry forecast is currently being entertained for Wednesday and
and Thursday. A surface front is forecast to move into the Ohio
Valley from the Great Lakes, but think this front will stall
north of the area as High pressure amplifies over the
southeastern CONUS.
Temperatures Monday will be cooler than normal, trending closer
to normal Tuesday, and then above normal for the second half of
the week.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
As of 745 PM EDT Thursday...
Earlier scattered to numerous showers and storms have dissipated
and/or shifted eastward into eastern Virginia. This leaves the
TAFs in VFR conditions that should continue through much of the
overnight. Will be watching for development of IFR visibility
fog at Lynchburg and Danville given recent rain and that
dewpoint/moisture values are currently highest. Winds generally
southwest 4-6 kts, lightest with eastern extent.
A pre-frontal trough, and later a cold front, will focus additional
showers into southeast West Virginia by 08-10z. Expect a
deterioration in ceilings toward VFR/MVFR from west to east with
increasing coverage of showers. Development of scattered
thunderstorms mainly during the afternoon, though a rough timing
would be toward the mid to late Friday afternoon hours per the
3-km NAM. Kept either VCSH and/or unrestricted showers due to
low confidence at this time range. Winds southwest around 6-10
kts, veering westerly slightly during the afternoon.
Extended Aviation Discussion...
VFR to MVFR cigs into Friday night with this front. As front
moves south Saturday morning, will see more coverage and this is
especially true Sunday. During this time, expect cigs/vsbys to
be highly variable but most of the time should be sub-VFR.
Front moves east Sunday night, with some lingering sub-VFR
possible over the mountains, but mainly VFR Monday with high
pressure nosing in from the northeast.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...KK
NEAR TERM...AL/KK
SHORT TERM...PM
LONG TERM...DS/PM
AVIATION...AL/KK/WP