Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/30/18
Area Forecast Discussion
National Weather Service Amarillo TX
636 PM CDT Sun Apr 29 2018
00Z TAF Cycle
Thunderstorms will be possible at the Amarillo and Dalhart TAF
sites between 00Z and 02Z to 03Z Monday. Otherwise, VFR conditions
are expected at all three TAF sites through 00Z Tuesday. The
Amarillo TAF site could possibly have some brief MVFR conditions
between 12Z and 16Z to 17Z Monday. Southerly winds will remain
gusty around 20 to 30 knots through 00Z Tuesday at all three TAF
.PREV DISCUSSION... /Issued 422 PM CDT Sun Apr 29 2018/
Noteworthy items for this forecast package still include the
chances for thunderstorms over the next several days.
Additionally, there is a small chance for the potential of fire
weather to develop, but it will all depend on rainfall and how the
fuels across the area react to any rainfall that does occur. For
now, will leave the mention of fire weather out of the forecast,
but tomorrow across the west behind the dryline there could
possibly be fire weather potential.
Small embedded pieces of energy are noted aloft in the 500mb pattern
where southwesterly flow exist. These small areas of vorticity along
with a dryline at the surface are helping to initiate storms in
eastern parts of New Mexico where an axis of instability exists.
The HRRR seems to have a good grasp on this and it brings
convection into the forecast area this afternoon and tonight.
Confidence is pretty good for this to occur and will maintain the
50-55 PoPs across western/southwestern parts of the Texas
Panhandle. Storms could be strong to marginally severe, but do not
anticipate widespread severe weather at this time. Hail around
the size of quarters with gusty winds of 50-60 mph are certainly
possible into the early evening hours until the environment
becomes less favorable. Am not expecting storms to last much past
midnight for our forecast area.
Tomorrow`s instability is strong with about the same shear of around
30-40 knots in the 0-6 km layer. One thing that is a problem for
tomorrow is the strong capping inversion. The layer of warm air
aloft is rather deep according to forecast soundings, so it may be
very difficult for storms to initiate and break this cap. That being
said, if any storms break the cap, severe will become increasingly
more favorable with hail around ping pong balls and wind gusts of 60-
70 mph. Low level helicity values are really weak in the afternoon
hours and values don`t get up to around 100-200 m^2/s^2 until early
evening. Storms will probably be sparse in coverage given the
strong cap, and it looks like wind and hail will be our main threats
Tuesday a small chance for thunderstorms will exists for mainly far
southeastern parts of the Texas Panhandle. Not expecting much across
our area on Tuesday at this time. Looks like initiation should keep
storms east of the forecast area.
Next chance for severe weather will be Wednesday for eastern parts
of the forecast area. Strong instability and strong bulk shear is
forecast, so rotating updrafts appear to have a good chance of
developing. Low level helicity values are somewhat low, so hail and
gusty winds speeds are probably going to be the main threats on
Wednesday for our area. Dryline is currently forecast to be pretty
far east, so we may miss out on any rainfall potential if that
dryline develops too far east.
Area Forecast Discussion
National Weather Service Cheyenne WY
918 PM MDT Sun Apr 29 2018
Issued at 915 PM MDT Sun Apr 29 2018
Isolated convection continues fire along a weak surface boundary
near the WY/NE border this evening. Most of the activity has been
high-based, producing strong outflow wind gusts and brief cloud-
to- ground lightning but little if any rainfall. Latest HRRR
guidance keeps isolated convection going until midnight before
exiting the northern NE Panhandle.
.SHORT TERM...(This evening through Tuesday night)
Issued at 315 PM MDT Sun Apr 29 2018
Warm temperatures this afternoon with readings in the mid 70s to
low 80s. A few records may be broken by the end of the day
although some high cloudiness has started to move over most of
southeast Wyoming. Current kcys radar loop shows isolated
thunderstorms developing along a line from near Torrington,
northward to Lusk and towards Newcastle. Activity is along a
dryline-like boundary which stretches from eastern Converse county
southward into southern Goshen county and then eastward into the
central Nebraska panhandle. Expect these thunderstorms to continue
to develop along this line and move northeast into this evening.
Do not expect coverage to become anything over isolated due a
relatively dry airmass aloft. Moisture should gradually increase
late this afternoon in the 700-500mb layer, but instability should
lower as it nears sunset. Thunderstorms will also move into an
environment with higher CIN over the next few hours, which should
at least suppress additional convection. Also noted that the
thunderstorms have struggled to increase in intensity this
afternoon, so severe thunderstorms containing hail appear highly
unlikely into this evening.
For Monday, the upper level low, currently across the Pacific
northwest, will gradually elongate and drift south and east
during the day. Another shortwave disturbance aloft will impact
the area during the day as a surface front stalls across areas
north of I-80, bringing a higher potential for strong/severe
thunderstorms in addition to a higher coverage of precipitation
through the evening hours. Continued to increase POP, especially
north of I-80 which has the best chance to see light to moderate
rainfall amounts with daytime/evening convection. Instability not
quite as good as today, but with cooler air aloft moving into the
area through the day, some strong to borderline severe storms are
possible along and east of I-25.
As for Tuesday, the surface front will become stationary near the
mountains and Colorado/Wyoming border after slowly moving
southward Monday night. The I-80 corridor will be the main focus
for showers and thunderstorms, possibly as far north as the lower
North Platte River valley in central Nebraska. Increased POP above
50 percent in this area from Laramie, Cheyenne, and including the
central and southern Nebraska panhandle. Although thunderstorms
coverage may be scattered for a time Tuesday afternoon and
evening, do not expect strong or severe storms at this time due to
low instability parameters. Otherwise, an overall cooling trend
will begin on Monday with highs on Tuesday struggling to reach the
mid 50`s across most areas.
.LONG TERM...(Wednesday through Sunday)
Issued at 219 PM MDT Sun Apr 29 2018
Midweek looks fairly wet with high elevation snow and lower
elevation rains with overnight mixed precipitation Wednesday night
into Thursday. Models fairly consistent in bringing a positive
tilt trough and upper low eastward across the central Rockies,
with a band of heaviest precipitation across southeastern Wyoming
and western Nebraska Wednesday night into Thursday when snow
levels drop to about 7500 ft. We will have to monitor for
potential Winter Weather Advisories midweek for elevations above
7500 ft based on what we are seeing right now.
After a dry period Thursday and Friday, showers return for next
weekend as another Pacific shortwave moves into the area.
.AVIATION...(For the 00Z TAFS through 00Z Monday afternoon)
Issued at 545 PM MDT Sun Apr 29 2018
Isolated convection developing across eastern/southeastern WY and
northwestern NE will linger through 03Z before dissipating. This
activity will avoid KBFF, KCDR and KAIA. Otherwise, VFR with mainly
high cloud CIGS will prevail. CIGS will lower to 5000 ft AGL with
showers in the vicinity of KRWL and KSAA after 15Z.
Issued at 228 PM MDT Sun Apr 29 2018
Elevated Fire Weather concerns today mainly west of Interstate 25
with gusty winds and low relative humidities being observed
across the lower elevations of Carbon and Albany county. However,
spring green-up appears underway in these areas based on area
webcams and observations, so do not expect conditions favorable
for rapid fire growth at this time. Fire weather concerns will
trend lower next week with daily chances of wetting rainfall and
widespread light to moderate rains.
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
915 PM CDT Sun Apr 29 2018
Based on the latest radar trends and the last few runs of the HRRR
PoPs for the overnight period have been trimmed back slightly towards
the Rio Grande River. Convection has not been able to make it off the
mountains of Mexico this evening and the dryline storms from earlier
this afternoon and evening are slowly drying across the Big Bend.
While a few showers and possibly a rumble of thunder could make it
into far northwestern Val Verde County most areas should stay dry
Patchy fog has been added for parts of the Coastal Plains as well.
Model soundings show a saturated surface layer with plenty of Gulf
moisture coming into Central Texas with the southeast flow at the
surface. The big question will be whether that wind at the surface
will decrease enough for fog formation. Based off the high resolution
models there will be areas where the winds will slack off just
enough for fog to form.
.PREV DISCUSSION... /ISSUED 625 PM CDT Sun Apr 29 2018/
Southerly flow continues across the region this evening. This will
continue to transport moisture north across the area. This moisture
combined with a trof to the west will lead to increasing SHRA/TSRA
chances throughout the upcoming week. KDRT could see some convection
move into the area between 02Z-05Z and have maintained the VCSH. VFR
conditions will become MVFR after 06Z across the area. Guidance
continues to indicate IFR conditions by morning, but at this time
feel higher wind speeds should reduce the chance for IFR conditions.
Gusty S/SE winds will decrease to 8-12 knots after 03Z. SE winds will
increase in the 15Z-18Z time frame on Monday and be back in the 15
to 20 knot range with gusts to near 25 knots, especially along the
Rio Grande. Cigs will slowly climb back to MVFR around 18Z. After
15Z, SHRA are possible across the eastern portions of the area so
went ahead and put VCSH for KAUS, KSAT and KSSF. KDRT will see the
possibility of TSRA again after 00Z Tuesday.
PREV DISCUSSION... /ISSUED 311 PM CDT Sun Apr 29 2018/
SHORT TERM (Tonight through Monday Night)...
Breezy southerly winds continue this evening into the overnight
hours, specially along the Rio Grande Plains. Increased moisture
moving into the area this afternoon will result in more cloud
coverage for the evening period. Latest Doppler radar regional
mosaic images show thunderstorms firing up along a dry-line across
the Pecos area. This feature is expected to move to the east for the
next several hours before it pushes back to the west this evening.
Storms will continue to develop this afternoon and evening ahead of
the dry-line with some of them making forward progression to the
northwest part of the Rio Grande. Most of the Hi-res models bring
convection to the far northwest corner of Val Verde County this
evening with activity coming down to an end before midnight tonight.
This dry-line will be the weather maker for the next few days as it
moves back and forth over west Texas with storms developing ahead of
it. With that said, another line of storms is forecast to develop
Monday evening and once again affect the northwest part of the Rio
Grande. The storm Prediction Center Day 2 categorical outlook
highlights the potential for isolated strong to marginally severe
thunderstorms Monday evening across the far northwest corner of Val
Verde County with main hazard threats being large hail and damaging
LONG TERM (Tuesday through Sunday)...
Once again, the dry-line will aid storms to develop across west
Texas while others develop across the Mexican mountains Tuesday
evening into Wednesday. The Rio Grande and southern Edwards Plateau
areas will have the better chances for rain for that period.
The weather pattern becomes interesting and more active on Wednesday
night into Thursday as an upper level disturbance pushes across the
four corners region into the Southern Plains and the dry-line pushes
closer to Val Verde County. Then on Friday, a cold front is forecast
to move down to the northern part of the area and stalls over the
For the latter part of the forecast package, we could see strong to
severe thunderstorms in addition to episodes of heavy rains. Weather
models keep the area with chances for rain through the weekend. Make
sure you check us out frequently for updates and the latest
information on the wet pattern.
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 82 62 77 67 81 / 0 - 20 20 20
Austin Bergstrom Intl Airport 80 62 76 66 81 / 0 - 20 20 20
New Braunfels Muni Airport 81 63 77 67 81 / 0 - 20 20 20
Burnet Muni Airport 81 62 75 65 79 / 0 - 20 20 20
Del Rio Intl Airport 82 66 80 69 90 / 0 20 20 20 20
Georgetown Muni Airport 81 61 77 65 79 / 0 - 20 20 20
Hondo Muni Airport 82 65 77 67 83 / 0 10 20 20 20
San Marcos Muni Airport 82 63 77 67 81 / 0 - 20 20 20
La Grange - Fayette Regional 82 62 77 67 82 / 0 - 20 10 20
San Antonio Intl Airport 81 64 77 68 81 / 0 10 20 20 20
Stinson Muni Airport 82 65 78 69 82 / 0 10 20 20 20
Area Forecast Discussion
National Weather Service Jackson MS
856 PM CDT Sun Apr 29 2018
Updated for evening discussion.
Surface high pressure will continue to slide east from the Ohio
River Valley to the Central Appalachians overnight. This will
help relax the surface pressure gradient across the ArkLaMiss with
light to calm winds for most locations. Clear skies and a drier
airmass with large dewpoint depressions combined with the light to
calm winds will favor radiational cooling across much of the
area. Current observations as of 2z also indicate that the
boundary layer has already decoupled at multiple locations. The
main change to the forecast was to adjust overnight low
temperatures down a few degrees, especially across the
northeastern portion of the area. Otherwise, the ongoing forecast
remains on track and no further changes were needed. /TW/
Prior discussion below:
.Tonight through Monday...
Latest rap and satellite imagery showered upper level ridging
approaching from the plains as the upper trough was tracking east
across the eastern seaboard. High pressure was providing sunny skies
across the region. Mid afternoon readings were from the lower 70s to
the lower 80s. Expect quiet conditions to persist through Monday as
the upper ridge axis moves into the Mississippi Valley region.
The surface high will track east of the region as we start to get
some low level return flow. Look for unseasonable lows with readings
from the lower 40s to the middle 50s. For Monday temperatures will
rebound into the upper 70s to the lower 80s./17/
Monday night through next weekend...
Relatively quiet weather conditions will exist through the work
week. The main weather story of the upcoming week will be the
return of summer-like temperatures, the likes of which we haven`t
seen so far this year.
A steep upper level ridge will begin to build over the MS River
Valley region during the beginning of the week as a broad surface
high centered near coastal Carolina continues to strengthen.
Return flow from this surface high will provide the ArkLaMiss with
warm, moist air from the Gulf for most of the week. A few showers
and weak thunderstorms can`t be ruled out on Tuesday and
Wednesday as moisture and cloud cover continue to build. Highs
will reach the upper 80`s by Wednesday. 925 mb temps in excess of
21 degrees and decreasing cloud cover on Thursday will lead to
highs of 90 degrees not out of the question. Although we`ve been
cooler than average over the last month or so, if we reach 90
degrees on Thursday(5/3) in Jackson, it`ll be the earliest of such
an occurrence since 2006. The average 1st 90 degree day for
Jackson is May 13th.
The ridge will begin to decay as the we get closer to the weekend,
allowing a front to approach the region from the northwest. Rain
chances will begin to increase on Friday. Models agree on the
front stalling and continuing to impact the regions weather
through at least Saturday. Model solutions begin to diverge as we
get into the end of the weekend.
00Z TAF discussion:
VFR conditions are prevailing this afternoon and expected to
prevail for the rest of the TAF period. Winds will remain light
tonight and out of the north/northeast or variable at times.
Winds will turn out of the southeast tomorrow around 10kts. /28/
.PRELIMINARY POINT TEMPS/POPS...
Jackson 50 80 55 82 / 0 0 1 11
Meridian 45 81 54 82 / 0 0 2 13
Vicksburg 52 81 56 83 / 0 0 0 12
Hattiesburg 49 81 56 81 / 0 0 5 17
Natchez 54 82 57 81 / 0 0 3 12
Greenville 50 80 56 82 / 0 0 0 3
Greenwood 47 80 55 83 / 0 0 0 3
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
851 PM CDT Sun Apr 29 2018
851 PM CDT
Have made some adjustments to dewpoints tomorrow. Day shift went
solidly above guidance for high temps Monday and latest RAP/HRRR
runs strongly support this adjustment and in fact is coming in
even a couple degrees warmer still. The RAP/HRRR tend to perform
quite well with 2m T/Td forecasts in situations like tomorrow with
late moisture return and strong WAA. Have adjusted dewpoints down
Monday, but am still a good 5F+ higher than latest RAP guidance
These changes support support issuance of a red flag warning, for
further details see the Fire Weather section of the AFD below and
the RFWLOT and FWFLOT.
214 PM CDT
The main forecast concern is warm, dry and breezy conditions for
Monday which will bring elevated fire danger to the area.
High pressure is moving off to the east late this afternoon while
an upper ridge axis across the mid and upper Mississippi River
Valley follows suit. Clear skies will be in place tonight but
winds will turn southerly, though remain on the light side.
Overnight lows will fall into the upper 30s to around 40, though a
few isolated spots could be cooler should winds go calm for a
little while this evening.
The surface high will be to the east Monday with the upper ridge
cresting the area. This will allow for breezy south to south-
southwest winds gusting 20-25 kt during the afternoon. A much
warmer airmass will build in and combine with abundant sunshine
and the gusty winds to propel temps into the mid and maybe even
upper 70s. Have increased highs temps and wind gusts slightly and
lowered dewpoints. The combination of dry conditions and gusty
winds will bring an elevated concern for quick fire growth/spread.
Conditions remain just below Red Flag Warning criteria but will
need to continue to assess the potential for drier/breezier
243 PM CDT
Monday night through Sunday...
A mild but increasingly active weather pattern is expected across
the region this week as a larger scale weather pattern shifts into a
negative PNA type pattern (a mean trough across the western CONUS
and downstream upper ridging over the central and eastern CONUS).
This type of larger scale weather pattern is one that is favorable
for a producing a period of active weather midweek, with a couple of
rounds of convection looking likely for much of the area especially
Wednesday night through Thursday night.
Tuesday is likely to be the warmest day of the year thus far across
the region, with any shower and thunderstorm activity likely to
remain west of the area across IA in closer proximity to the
better moisture and the perturbed mid-level flow. Cloud cover is
likely to be on the increase across the area during the day, but
with breezy southwest winds gusting up to 35 mph, expect
temperatures to top out around 80 in most areas. The winds will be
stronger on Tuesday then they are on Monday, and this may result in
some increased fire weather concerns over the area. However, the
main difference over the area Tuesday will be increased low-level
moisture, which should keep minimum RH levels from dropping much
below 30 percent. However, with the dry conditions of late, if dew
points are able to mix out lower then current forecast, then fire
weather concerns could increase on Tuesday.
Mild weather will continue on Wednesday, though with more cloud
cover around. A quasi-stationary surface frontal boundary is
expected to set up over the IA and WI Tuesday night, and this
boundary is likely to move little through Wednesday as southwest
flow aloft remains parallel to the orientation of this boundary. As a
result, the main focus for showers and thunderstorms will likely
continue to be to our northwest on Wednesday as low amplitude mid-
level disturbances continue to track northeastward across the upper
Midwest and interact with this surface boundary.
Mid-level heights are expected to begin to fall across the region
Wednesday night as the main southwestern upper trough/low begins
to eject out over the Plains and the upper ridge shifts east. As
this occurs, expect the perturbed southwest mid-level flow,
initially to our northwest, to sag southward into northern IL late
Wednesday night. This will result in a probable threat for a
period of thunderstorms over the area Wednesday night into
Thursday. Another round of more widespread convection then looks
to be a good likelihood late Thursday into Thursday night as main
upper-level disturbance shifts across the area. Moderate to heavy
rainfall will be possible with these storms Wednesday night
through Thursday night, and this may result in 1 to 3 inches of
rain for the area. We also can not rule out the potential for some
strong to severe storms during this period due to the increased
deep layer sheared environment expected over the area.
A bit cooler, more seasonal conditions are expected to set up over
the area in the wake of this system Friday into Saturday. Highs
will likely be mainly in the 60s, to around 70.
851 PM CDT
Exceptionally dry conditions continue across the region with RH
values dropping into the 12-20% range across the CWA today.
Majority of forecast models continue to struggle with a high bias
in dewpoint forecasts, the 00z runs from both GFS and NAM last
night had an avg low bias of 15-20F with Tds verifying at 21z
Sunday. The RAP/HRRR guidance have been performing far superior
and have no reason to believe that won`t be the case again
tomorrow. Have adjusted forecast dewpoints/RH downward for Monday
and now have RH values over the the entire area now bottoming out
between 15-25% (lowest SE and highest far west). It is worth
noting that some of the best performing models actually suggest RH
could be a bit lower still.
The US Forest Service Wildfire Assessment System forecasts 10-hour
fuel moisture values tomorrow afternoon to drop to 5-6% over NW
CWA and 7-8% SE, indicative of exceptionally dry fuels. This isn`t
surprising, given the observed precipitation over the past 30 and
60 days over these areas being less than 50% of normal over
western areas of CWA and not much over 50% east.
The strongest winds should be over north central IL and have
issued a red flag warning for these areas where winds are likely
to reach ref flag criteria. Farther east winds are forecast to be
a bit lower and leads to slightly lesser confidence in reaching
strict red flag warning criteria. Later shifts may well need to
expand the red flag warning farther east, but opted to start
conservatively with this evening update to the forecast. Even east
of the red flag warning area, conditions will support potentially
large and fast spreading fires.
For the 00Z TAFs...
Gusty SSW winds are expected to develop Monday, otherwise VFR
through the period with weather likely to have minimal adverse
effects on aviation operations.
243 PM CDT
Surface high pressure is centered over southern Lake Michigan this
afternoon and this is resulting in light and variable flow over
southern parts of the lake and southerly flow over the north. This
surface high will gradually shift southeastward and set up over
the southeastern CONUS by Monday. As this occurs, a more active
weather pattern is expected to set up over the Central U.S., and
this looks to result in a couple of low pressure systems shifting
northward across the Upper Midwest through late week. The
pressure gradient between these pressure systems will likely
support a period of enhanced southerly winds (25 to 30 kt) over
the lake Monday through Wednesday. However, increased stability
over the lake will likely limit the potential for gales.
IL...Red Flag Warning...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ019-ILZ020...noon Monday to 8 PM Monday.
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