Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/03/19
Area Forecast Discussion
National Weather Service Denver/Boulder CO
902 PM MDT Thu May 2 2019
Issued at 902 PM MDT Thu May 2 2019
A couple bands of showers, driven by surface convergence and
modest upper level jet support, developed over the eastern plains
through the evening, affecting mostly eastern Adams, Lincoln and
Washington Counties. The storms were generally weak, with some
gusty winds and brief rain. Most shower activity has left the
forecast area, with just southeast Washington and southeast
Lincoln Counties receiving any precipitation at this point. Dry
and mostly clear skies are expected overnight and through most of
tomorrow. Updated the forecast package to clear out the evening
shower activity, but nothing else was changed.
.SHORT TERM...(This evening through Friday)
Issued at 323 PM MDT Thu May 2 2019
A broad upper trough pushing down over the northern Rockies and
into the Great Basin will slowly be moving east across the area
tonight. A speed max along the base has kept an area of light
showers moving across eastern plains most of the day today, and
will help in creating scattered showers and a few thunderstorms
this afternoon into the evening. Strong southerly winds over the
eastern plains are carrying higher dew points, with a Denver
Cyclone just south of DIA wrapping some of the moisture in.
Modeled CAPE isn`t impressive, with warmer air aloft in the west-
southwesterly flow. Shear will be better out east though, with the
HRRR keying in on some weak updraft helicity. With not a lot of
CAPE to work with and downward QG motions, not expecting much
more than some gusty winds and small hail from thunderstorms that
Showers and storms will focus on a line from the Palmer Divide
northeast to near Sterling then push east through the rest of the
evening, with activity done or east of the area right around
midnight. Some isolated to scattered activity over the mountains
will have snow levels around 9Kft, with less than an inch expected
up there by midnight tonight. Lows tonight will be warmer than
this morning, with winds staying breezy over the eastern plains
and some cloud cover, as well as warm advection from the west.
The trough axis will pass after midnight with warmer and drier air
moving in on northwesterly flow aloft for Friday. Look for
temperatures about 3 to 6 degrees warmer coming up to about normal
for early May. Besides a few clouds, expect a dry day.
.LONG TERM...(Friday night through Thursday)
Issued at 323 PM MDT Thu May 2 2019
After a weak disturbance passes across the northern rockies and
northern plains Friday, a cool front pushes southward onto the
central US plains Friday night and early Saturday. With weakening
flow aloft over CO into Saturday, return southerly flow at the
surface develops behind the cool front. This return flow
eventually draws slightly higher dew points and capes northward
across the ern plains by Saturday afternoon. ML capes Saturday
aftn and evening are scant along urban corridor, with around 200
j/kg in the AKO vicinity. Much stronger ML capes in the 500-800
j/kg range with SB 1200-1500 j/kg capes stay out east along the
CO/KS border. Will have isolated pops for the eastern Palmer Ridge
region and points east of a Limon to Akron to Julesburg line.
By early Sunday, a drier upper level ridge is in strengthening mode
over the region ahead of a Pacific trough which moves onto the
southern CA coast. Will expect no pops for Sunday through Monday
as partly to mostly sunny skies look to be the rule as temps rise
into the mid to upper 70s across the lower elevations for Sunday.
The upper level ridge peaks in amplification midday Monday as temps
reach near 80degF across the plains. The record high for Denver on
Monday is 86F, but at this time believe temps will stay under that
record mark. There will be two troughs of low pressure to keep an
eye on as the Tuesday through Thursday period approaches. A sharply
cooler change on the way. As the closed off upper trough spins
across the southern great basin, a fast moving wave drops southward
out British Columbia and Alberta dragging much colder into the
northern Rockies and high plains. The Canadian cold front looks to
cross the MT/WY border around 00Z Tuesday with the front entering
eastern CO in the early morning Tuesday. An environment of
increasing mid and upper level QG ascent begins at this time and
will persist all the way into Thursday. GFS surface omega shows the
cold easterly push and upslope conditions beginning from 09-12z
Tuesday and maintaining through Wednesday. Another wave of cold
northerly flow will keep the cool and unsettled trough over the
region. Bottomline, will expect moist and weak easterly surface flow
to persist through late Wednesday keeping the area cool and showery
with temps around 15degF below seasonal average.
At this time, looks like the snow level will drop down to the 6000-
7000ft level by early Wednesday, so precip is expected to be in the
form of rain and drizzle across the plains.
For Thursday...the cooler period begins to break as the trough
begins to move east and drier southwesterly flow develops across
the central rockies.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 902 PM MDT Thu May 2 2019
The evening shower activity over Denver remained to the south and
southeast of town, generating only a brief period of gusty winds
at KDEN and a 10 minutes of rain and a few lightning strikes at
KAPA. Clouds are now on the decrease as shower activity moves
eastward over northeast Colorado. Drier and more stable air will
continue moving in from the west overnight. Winds should turn to
light southerlies over the next couple hours. A mostly sunny day
is expected tomorrow with light and variable winds. Therefore, no
aviation impacts are expected.
Area Forecast Discussion
National Weather Service State College PA
1134 PM EDT Thu May 2 2019
An oscillating front will remain in the vicinity of Pennsylvania
through most of the weekend. A wave of low pressure on the front
will track south of the region Saturday night and Sunday, then high
pressure will work into the area early next week. A slow-moving
cold front will likely approach Pennsylvania from the west
during the second half of next week.
.NEAR TERM /UNTIL 8 AM FRIDAY MORNING/...
Tiny SHRA over the NE could continue, but not worth more than a
20 PoP. Stuff over PIT is weakening nicely, and slowing down
drastically. Will keep a low PoP in the Laurels, but looks like
the convection there will continue weaken as it creeps eastward.
Mild night in store as clouds do increase overnight.
SHRA/TSRA on the PA/OH border and making a run for the Laurels.
These are certainly driven by a coherent feature, and it is again
surprising just how poorly the HRRR and RAP are doing modeling
these showers. Frustrating. The southern cluster looks like a
bow and has recently gained a cold pool rain shield behind it.
This usually bodes well for continuing downstream. But, it is
also losing some of it`s lightning and there is not much
convergence with nil wind ahead of it.
If they do hold together, they could get into the Laurels in the
next 1-1.5 hrs. That is the only major change for the evening,
as the stability and niceness of the evening continues
A really nice evening underway. Have dropped PoPs for the next
many hours except over the SE and far eastern counties where the
tallest cu have congested over the Endless mountains and along
Blue mountain to the west of Harrisburg. Subsidence and
stability keeping the cu tiny across the rest of the state and
into eastern OH.
.SHORT TERM /8 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
Band of showers and storms in central Ohio will work into the
area later tonight. Coverage still expected to be less than more
and PoPs are 60-70 only in the NW and taper off to less than
20 for all the east for the balance of the night. Low clouds
will try to make a comeback in the east as flow comes off the
ocean later tonight and higher moisture slides northward into
the lower Susq and Poconos. It should not be as thick or
stubborn as what we had last night/this morning.
The sct SHRA will slide east across the area during the daylight
hours due to the vort max/short wave trough currently spinning
over MO/AR. Northern and eastern areas will likely be a little
cooler on Friday, given the position of the front.
Current day2 outlook by SPC for a MRGL risk across the srn half
of the area looks good as we should manage more early-day
sunshine than we did on Thursday.
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Line of showers/storms should continue to progress through the
region Friday night into very early Saturday (SE). These will be
associated with an approaching cold front. The mid range models
are in fair agreement and these could linger through the first
half of the overnight period. Have increased POPS accordingly.
Cold air will cool down temperatures Saturday. Saturday is
looking damp and cloudy across the forecast area, as the quasi-
stationary front dips south of the region. Model RH time
sections show abundant low level moisture (stratus), but little
chance of significant rain during the daylight hours. Medium
range guidance is lending increasing confidence in a rainy
Saturday night and early Sunday, as wave of low pressure tracks
south of the state.
The 12Z NAEFS continues to show drier weather early next week,
as surface high pressure builds into the state. Will then ramp
up the chance of rain by midweek associated with the approach of
a slow-moving cold front over the midwest.
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
Updated the TAFS late this evening.
Still a few showers just west of JST.
I did back off on the lower conditions some.
Early evening discussion below.
For 00Z TAF package, I did add TEMPO group in for JST this evening.
Cluster of showers and storms heading eastward from OH.
Late afternoon discussion below.
Obs coming in ok since 4 PM.
Not much on radar and all sites VFR now.
Thus minor adjustments to the TAFS late this aft.
Early afternoon discussion below.
Missing a lot of the obs from 1 PM.
Did edge down risk of thunder some this aft. Best chc to the
southeast based on temperatures and CU building at mid lvls.
Expect CIGs to drop later, especially across the east, where
winds could turn back more to the east.
Line of showers and storms just about western Ohio, so adjusted
Sat...AM low cigs trending VFR. Rain spreading SW to NE through
Sat night with deteriorating conditions .
Sun...Rain/restrictions with drying trend into Sunday night.
Mon...Chance of rain showers nrn tier.
Tue...Mainly dry, but chc of showers across the NW.
Area Forecast Discussion
National Weather Service Paducah KY
1003 PM CDT Thu May 2 2019
Issued at 1002 PM CDT Thu May 2 2019
Just completed a quick grid, text, tabular update to reflect the
cancellation of Tornado Watch Number 122 and to remove some of the
southeast Missouri and southwest Illinois counties from the Flash
Flood Watch. The threat of any additional overland flooding will
be essentially non-existent for the rest of the night for the
counties removed from the Flash Flood Watch.
UPDATE Issued at 814 PM CDT Thu May 2 2019
Just amended the existing Flash Flood Watch to reflect the
excessive rain potential along the northwest semicircle of the
MCV currently moving into southeast Missouri and southwest
Kentucky at this time. The actual gradient and axis of the
excessive rain will remain wholly within the watch area.
At this point and most concerned with the Delta area of southeast
Missouri, then working across extreme southern Illinois, the
northern Purchase area and northern two thirds of Pennyrile region
of west Kentucky to the first tier of southwest Indiana counties
north of the Ohio River. Outside of this area, much less confident
of flooding rains, but kept in place for collaborative reasons.
May need to cancel portions of the flash flood watch, especially
north and west later tonight, as the threat area shifts northeast.
Also adjusted the expiration time from 12z (7 am CDT) to 15z (10
am CDT) Friday to account for the exit period of the heavy rain
from the WFO PAH CWA.
UPDATE Issued at 539 PM CDT Thu May 2 2019
Updated forecast products, gridded, and tabular data to reflect
the recently issued Tornado Watch 122 issued in coordination with
the Storm Prediction Center (SPC).
The MCV (Mesoscale Convective Vorticity) center that has been
moving northeast from central AR this afternoon continues to
maintain its identity late this afternoon into northeast AR. Given
the history of tornadoes with this mesoscale system, the decision
was made to extend the tornado threat into extreme southeast MO
and the Purchase area of west Kentucky.
The HRRR is providing a good initialization and short term
forecast on the direction and timing of the MCV this afternoon.
The atmosphere is quite moist and unstable in the lowest 0-3km.
Given the implied super-adiabatic lapse rate potential in the
Mississippi Delta area, would not be surprised to see some
convective wind gusts with showers even outside any identified
circulations. KNQA/TMEM/KPAH VAD winds at 850 mb running 35 knots
from the south, with 700 mb south-southwest winds near 35 knots,
and 500 mb southwest winds 45-50 knots, representing a fair
veering wind profiles.
Using the RAP guidance as a proxy, the northern end of the best
0-2km lapse rates (6.5C/km or higher) extend from near New Madrid
MO to Murray KY, shifting toward the southeast Calloway County
border between 01z-02z. At the same time, the axis of the highest
00-3km bulk shear move from northwest TN, onward to southern
Graves and Calloway county by 03z. Downdraft cape of 400 J/kg2 is
marginally expended during the same time and area, suggesting a
limited wind threat outside any identified circulations given the
lapse rates. There is some CAPE expenditure, but not ideal for
widespread convection. Some minor pressure falls are forecast by
the RAP, but no specific foci at this moment.
Since the RAP is only a proxy at this point, there could be as
much as a 25-30 mile variation of the lapse
rates/instability/etc., northwest or southeast his evening.
The the loss of diurnal insolation, there may be some
stabilization of the boundary layer, but without any sustained
cold pool potential from convection to aid in the stabilization,
the tornadic threat may extend a little beyond sunset and become
more contingent on the internal circulation of the MCV core.
.SHORT TERM...(Tonight through Friday night)
Issued at 205 PM CDT Thu May 2 2019
Clearing continues to work north into west KY. In fact there is a
generally thinning overall even into SEMO, southern IL. Not sure
how much we will destabilize as the MCV over AR pushes toward the
area. In terms of strong to possibly severe convection, will have
to keep an eye on west KY as upper 70s to lower 80s air is close
by, in W/NW TN. We anticipate a surface reflection will accompany
the MCV and back and possibly increase low level winds across the TN
line into west KY. A watch is being considered right up into the
MO Bootheel region. Otherwise issued a Flash Flood Watch earlier.
This can be expanded east with time. But FFG`s are higher into
west KY, where there has been much less in the way of rain, if
any. Seems like the best chance area for water concerns is along
the Ohio, far west KY, maybe parts of SEMO, southern tip of IL.
Categorical PoPs tonight. Another 1-2" of rain possible. This is
not a high end confidence call. More a function of playing it
safe. May be hard to pin down locations. Will depend on the
deformation aspect, as well as local convective trends.
Expect a lull Friday, in the wake of the MCV/S-WV, then another
round of showers and storms late Friday moving into our west
counties, spreading across the area Friday night. All of this in
advance of s/wv energy approaching from the southern Plains.
.LONG TERM...(Saturday through Thursday)
Issued at 205 PM CDT Thu May 2 2019
Confidence remains good with rain chances through the extended
portion of the forecast. The timing is still in flux among the model
solutions. However they all show similar synoptic scale solution
with different timing and in some cases slightly different paths
with surface lows.
The cold front that moves through Friday night will stall just south
of the region and then try to meander or lift north into the area
Saturday. This will be in tandem with a weak upper level trough
rotating around the upper low in Canada. All the models agree on
rain Saturday. We will likely have some thunder with weak CAPE`s
around 300 and LI`s of negative one. K index values reach into the
lower 30s as well. So a clap of thunder will not be out of the
Saturday night high pressure will build in at the surface with a
near zonal flow aloft. The high will suppress precipitation for most
of the area through Monday night. It will also start a warming trend
as the high drifts east and a southerly flow returns to the area.
Tuesday the upper low over the southwest will eject several short
wave or spokes of energy into the region. This will bring storm
chances back into the forecast for the middle of next week. Finally
by Thursday a surface low will phase with the upper level energy to
keep showers and possibly thunderstorms in the forecast
Issued at 627 PM CDT Thu May 2 2019
Hodge podge of ceiling and visibility conditions will be likely
for the WFO PAH TAF sites through at least 12z Friday, before
ceilings drop to IFR/VLIFR conditions behind the slowly moving
The small elevated circulation moving through northeast AR at the
moment is expected to shift northeast through west KY/TN this
evening. On the northwest side of this circulation, ceilings will
move through the range of MVFR ceiling conditions with time,
working northeast into parts of southwest IN later this evening.
Given the shear in the lowest 0-3km, aviation interests may need
to be watchful for wind changes, especially near the KPAH TAF
To complicate matters, moderate to heavy rain, as well as a
saturated boundary layer will generate temporary MVFR/IFR
visibilities this evening and overnight.
By the time the front moves into the area most areas should see
predominant IFR ceilings for the remainder of the forecast period.
IL...Flash Flood Watch through Friday morning for ILZ077-078-082-083-
MO...Flash Flood Watch through Friday morning for MOZ110>112-114.
IN...Flash Flood Watch through Friday morning for INZ081-082-085>088.
KY...Flash Flood Watch through Friday morning for KYZ001>022.
Area Forecast Discussion
National Weather Service Blacksburg VA
859 PM EDT Thu May 2 2019
The area will remain in a warm and humid air mass with scattered
showers and storms across the area until a cold front crosses
the region late Saturday into Saturday night. High pressure will
start to build into the area, and be in place across the region
through at least Wednesday. The chance of showers and storms
will start to increase again Thursday into Friday with the
approach of another cold front.
.NEAR TERM /THROUGH FRIDAY/...
As of 855 PM EDT Thursday...
Earlier bands of convection mainly along the Blue Ridge have
faded with loss of heating. However still have added upstream
coverage just west of the area associated with a faint wave
aloft and associated surface trough. This also where some
residual instability and deeper moisture remain. Latest HRRR
shifts some of these showers northeast into northwest sections
through midnight while weakening, so included some higher pops
northwest of I-81 for a few more hours. Otherwise appears will
see more clouds north and west, with mainly clear conditions
continuing south. Expect fog to be a bit more widespread
overnight given moist dewpoints and espcly in spots that saw
heavy rain from this afternoon/evening. Lows still on track with
50s mountains to low 60s east.
Previous discussion as of 300 PM EDT Thursday...
Scattered showers and storms will continue the remainder of the
afternoon hours and into the early evening hours across the same
general region as they exist currently. The bulk of the activity was
along and perhaps one tier of counties east of the crest of the Blue
Ridge. Another cluster of showers and storms were generally along
and south of Route 460 between Blacksburg and Bluefield and points
south. Additional migration of the activity farther east into the VA
and NC Piedmont region is also expected. Limited if any showers and
storms are expected in the Danville, VA area and points south and
east of there.
This activity was situated within a warm and humid airmass in
advance of an approaching shortwave trough. This feature is expected
to sharpen in amplitude heading through tonight and into Friday.
This translation will have the effect of creating a temporary
shortwave ridge across our region later tonight into at least the
first half of Friday. This will place the region within a less
favorable regime for shower and storm development on Friday morning.
However, development is expected Friday afternoon in advance of
the approaching cold front, however, coverage will be focused
more across the southwestern and western sections of the area as
compared to today`s activity. As evening approaches the
activity will be heading eastward through the area in advance of
the associated front.
The Storm Prediction Center has placed roughly the western half of
the region tomorrow and tomorrow night with a Marginal risk of
severe weather. Damaging winds are the greatest threat.
Temperatures will remain on the mild side. Low temperatures tonight
will range from the mid to upper 50s across the mountains with
readings around 60 to the lower 60s across the Piedmont. High
temperatures on Friday will range from the upper 70s to around 80
across the mountains with low to mid 80s across the Piedmont.
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 254 PM EDT Thursday...
Generally should be unsettled most of this period as slow moving
front edges east and southeast from the mid-Atlantic to central MS
Valley Friday evening to east of the piedmont by Sunday evening.
Several waves of low pressure and upper vorts will bring periodic
episodes of showers and thunderstorms. The models are showing better
clustering toward high pops in the mountains Friday evening, the
somewhat drier late Friday night into early Saturday morning, as one
vort axis moves east of the piedmont by 8am Sat. The next arrives
across the mountains by midday, with a better shortwave along the
front moving across the Ohio Valley into PA by Sat afternoon. Some
upper divergence and stronger low level forcing. Mid level lapse
rates are not overly impressive, but low level lapse rates should be
fairly steep Saturday afternoon especially along/east of the Blue
Ridge. SBCapes will be around 1000 or more in the piedmont, and
marginal risk per SPC looks fine for now, so expect some gusty winds
and marginally severe hail potential east of the Blue Ridge Sat
Surface wave along the front will slide into northern VA by Sunday
morning with continued high pops into Sat night/Sunday morning, with
drier air starting to work into the mountains late in the day,
though upper trough axis may stay west of the area into Sunday
night, the deeper moisture should be east of us.
Temps will stay above normal through the period, though lows may
close in toward normal Sunday night.
Confidence is good for shower and storm chances through the period,
with Saturday looking like the more active day.
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 125 PM EDT Thursday...
High pressure settles over the area Monday into Tuesday with
building 5h heights. Ridge breaks down midweek with approach of a
front and strong trough in the middle of the country. Will see pops
increasing but temps will stay above normal.
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
As of 720 PM EDT Thursday...
Mainly VFR conditions to prevail into this evening as convection
slowly fades with loss of heating. However cant totally rule out
showers to the west working into the KBLF/KLWB region through
the evening where MVFR cigs will be possible. Main concern
overnight outside of any western showers will be with patchy
dense fog espcly where earlier rainfall occurred. Think clouds
may limit coverage over the far west although KLWB may see just
enough clearing to drop down to MVFR/IFR late tonight into early
Friday morning. Also with showers having passed near KBCB/KLYH,
will add in a period of MVFR fog which could drop down to IFR if
more clearing does occur.
Showers and storms will be at a minimum through Friday morning
and early afternoon. At best isolated showers are possible
along and west of a KLWB-KTNB line. Most ceilings through the
morning will be low end VFR with patchy MVFR conditions,
especially across the mountains. Winds through the forecast
period will be light from the south or southwest during the
daylight hours and light and variable overnight.
EXTENDED AVIATION DISCUSSION...
A weak cold front will cross the area Friday night. Look for
increased coverage of showers and storms with localized sub- VFR
conditions with the associated cloud cover, showers and storms.
A stronger cold front will cross the region Saturday night.
Anticipate another round of showers and storms with a greater
coverage of sub-VFR conditions.
Sunday, winds will be gusty from the northwest behind the
exiting cold front, and most locations will return to VFR. The
exception of will be some upslope clouds/scattered showers
across the southeast West Va mountains.
Monday and Tuesday VFR conditions and lighter and variable
winds are expected as high pressure builds into the area. Late
in the day Tuesday, winds will start to increase from the south
as the center of the high shifts east.
Area Forecast Discussion
National Weather Service Tulsa OK
949 PM CDT Thu May 2 2019
The main change to the going forecast is to lower pops for later
tonight. Recent runs of the HRRR and the new 00Z NAM suggest that
precipitation will be slower to spread into the area than earlier
expected, with the majority of the rainfall now likely to occur
Friday afternoon and evening. Isolated showers and thunderstorms
will still be possible in the western part of our forecast area
late tonight, but most places will remain dry until the daylight
Update on the way.
OK...Flash Flood Watch from 7 AM CDT Friday through Saturday morning
AR...Flash Flood Watch from 7 AM CDT Friday through Saturday morning