Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/30/20
Area Forecast Discussion
National Weather Service Caribou ME
1154 PM EDT Wed Jul 29 2020
A trough of low pressure will slowly move across the north through
Friday. High pressure will build in from the west on Saturday and
crest over the area Sunday. A trough of low pressure will cross the
region on Monday.
.NEAR TERM /THROUGH THURSDAY/...
1153 pm Update...
Adjustments were made to increase pops overnight, mainly North
of the Katahdin region. Rather vigorous short wave approaching
from Quebec will track east across Northern Maine around
daybreak. Showers already pushing into Northern and Western
Maine per latest radar reflectivity imagery, with some lightning
strikes already indicated per lightning detection. Latest runs
of the HRRR seems to be handling things well at this hour, and
does shows activity moving across Northern Maine by daybreak.
Based on this, have increased QPF in the 06z-12z for the North.
Showers and thunderstorms will continue into the day Thursday
with another shortwave rounding the upper level low and
providing lift. Mid-level lapse rates will be around or above 6
degrees C/km and more favorable for ascent. An isolated severe
weather threat may exist across southern and eastern parts of
the forecast area where bulk shear around 30 to 40 knots will
overlap with the greatest chances for SBCAPE of at least 1000
j/kg according to the 12z HREF. The threat will be dependent on
cloud cover and how much heating occurs. Gusty winds would be
the primary concern. High temperatures will be in the 80s across
the southern half of the forecast area, with 70s across the
north where thicker cloud cover is anticipated.
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
A trough of low pressure will be to our north Thursday night as very
weak surface low pressure drifts off to the northeast. Some showers
may remain across the north in the evening with any showers
dissipating overnight. Northern areas will remain mostly cloudy with
partial clearing Downeast. The upper trough will remain nearby to
the north on Friday as very weak surface low pressure stays just to
our northeast. With moisture over the area, mainly the north, and
low heights, some scattered showers and spotty thunderstorms may be
over the area, mostly central and northern spots. The upper trough
will lift away to the northeast Friday night followed by upper level
ridging and surface high pressure beginning to build in on Saturday.
A weak trailing shortwave may bring an isolated shower or
thunderstorm on Saturday across the north. Otherwise, Saturday will
turn out partly cloudy and warm.
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Upper level ridging across the area will bring a mostly clear night
Saturday night with weak surface high pressure to the south. The
weak flow and clear sky will likely allow some patchy valley fog to
form late. Sunday will begin mostly sunny. Some stray thunderstorms
are possible during the midday and afternoon, mainly across far
western areas, as a bit of moisture begins advancing north ahead of
a new trough approaching from the Great Lakes. Clouds will increase
late Sunday into Sunday night as the trough and frontal system
approach. Current guidance is showing potentially a lot of moisture
with this system but lifts most of that moisture to our northwest
ahead of the front. A cold front will then press across the area
Monday bringing some showers and isolated thunderstorms across the
region, mostly over the north. High pressure will then build in from
the west Monday night into Tuesday bringing clearing and some lower
humidity to the region. A weak trough lifting into the region
Wednesday may bring another chance for some showers with the best
chances for any showers again favoring far western parts of the
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
NEAR TERM: VFR for Downeast terminals next 24 hours. For PQI
terminal and north expected MVFR cigs to move in shortly after
daybreak. Cannot rule out IFR cigs at FVE after 09z. Showers and
possible thunderstorms expected overnight across the north and
again during the afternoon tomorrow with localized IFR
Thursday night: MVFR north VFR Downeast, but locally IFR in any fog
late at night. Light NW wind.
Friday: VFR. Light NW wind.
Friday night: VFR. Light NW wind.
Saturday: VFR. Light W wind.
Saturday night: VFR, but locally IFR in patchy fog late. Light W
Sunday: VFR. Light S wind.
Sunday night: MVFR lowering to IFR. S wind.
Monday: IFR. S wind, becoming N over the north. Showers.
NEAR TERM: Winds and seas will remain below small craft criteria
through Thursday. Patchy fog is possible with visibility below 3
NM, mainly after midnight tonight.
Winds and seas are expected to be below SCA through the coming
weekend. Humid air will likely result in fog at times across the
waters, especially late at night and early mornings.
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
959 PM CDT Wed Jul 29 2020
Issued at 907 PM CDT Wed Jul 29 2020
Scattered thunderstorms will move across southeastern Missouri
and west-central Illinois overnight, with more stratiform showers
blanketing most of eastern and central Missouri. Several
vorticity maxima are passing around a mid-level trough, which
continues to support the showers and thunderstorms across the
area. Anomalously high PWATs of over 2 inches across Missouri will
lead to efficient rainfall rates where convection develops.
Abundant moisture, higher MUCAPE, and low-level convergence
overlap in southeastern Missouri. High rainfall rates in
thunderstorms could trigger flash flooding, warranting the
continuation of the Flash Flood Watch for the extreme southern
.SHORT TERM... (Through Late Thursday Afternoon)
Issued at 329 PM CDT Wed Jul 29 2020
A short wave trough over the eastern Plains has turned the low level
flow around to the southwest. Scattered showers and thunderstorms
are developing due to low level moisture convergence associated with
this southwesterly flow. As the mid-upper short wave digs east-
southeast tonight, the eastern lobe of low level vorticity
associated with the system is expected to drift into central/south
central Missouri. The 850mb gradient tightens substantially through
the evening as this occurs which ramps up the low level jet and
subsequently the moisture convergence. While most, if not all of
the area should see some rainfall tonight, short range guidance
targets northern Arkansas and south central into southeast Missouri
with the strongest low level moisture convergence. I`m inclined to
think the models which spread heavy QPF up into east central and
northeast Missouri tonight are overdone. With mass fields showing
the stronger forcing further south, I think the highest rainfall
amounts will generally be across the eastern Ozarks, along and south
of I-44 much like what the RAP is depicting. Ensemble guidance
shows anomalously high p-wats so these storms should be efficient
rainfall producers. Will therefore go ahead and issue a flash flood
watch for parts of southeast Missouri.
The shortwave deepens over the east central Plains Thursday and
Thursday night, with the low level reflection stretching out and
moving across Missouri. The primary area of low level moisture
convergence moves east slowly through Thursday morning as the low
level circulation stretches out. With the low level forcing moving
away, the showers and storms should become less widespread through
the day...with the possible exception of parts of southeast
Missouri. Guidance is indicating that another round of
thunderstorms will be possible in the afternoon across southeast
Missouri along the "cold" front associated with the surface low. The
increased surface convergence along the front combined with the very
moist atmosphere will likely be enough to kick off another round of
thunderstorms during the afternoon. P-wats remain high so have
continued the flash flood watch through Thursday afternoon.
.LONG TERM... (Thursday Night through Next Wednesday)
Issued at 329 PM CDT Wed Jul 29 2020
The upper level pattern shifts to a mean longwave trough over the
Mississippi Valley with a ridge out west over the Rockies for Friday
through at least early next week. With Missouri and Illinois right
in the trough axis, we should have relatively cool temperatures and
a continuing chance for showers and possibly a few thunderstorms.
This convection will likely be mainly diurnally driven, and by a
couple of vort maxes that move through, one on Sunday and another
.AVIATION... (For the 00z TAFs through 00z Thursday Evening)
Issued at 629 PM CDT Wed Jul 29 2020
Thunderstorms have largely left the vicinity of the terminals,
with the exception of UIN until 01Z. Otherwise, the threat for
VSBY restrictions due to heavy rain has diminished. A weak cold
front will stall across southeastern MO and southern IL Thursday
morning. Flight conditions will deteriorate to MVFR at all
terminals this evening, with all sites except UIN falling to IFR
by sunrise. Light showers will persist until the early afternoon
Thursday, but the heavier rain expected from that system should
evade the TAF sites.
MO...Flash Flood Watch through Thursday evening for Crawford MO-Iron
MO-Madison MO-Reynolds MO-Saint Francois MO-Sainte
Genevieve MO-Washington MO.
Area Forecast Discussion
National Weather Service Pocatello ID
223 PM MDT Wed Jul 29 2020
.DISCUSSION...Radar shows a few thunderstorms have formed, mainly
from the Arco Desert northeast to the Divide and the Island Park
area. This region of convective initiation is well covered by the
high-resolution solutions. Of these, the AZ WRF is most
aggressive in pulling activity east to the Idaho Falls area later
this afternoon. The nested NAM is similar, but weaker and later in
the evening, while the rest keep the activity north or dissipate
it all together as it moves toward the middle of the Snake Plain.
Opted to split the difference and keep weak mention by early
evening. Although East Idaho generally under the influence of the
upper ridge, some of the high-resolution solutions are introducing
isolated convection during the day Thursday. There is a very weak
shortwave feature that tries to climb the ridge through Oregon
during the day, but the question is moisture availability. At this
time, if anything, would expect an isolated sprinkle at best. Much
bigger impact across the region will be the increasing
temperatures through the end of the week. Heat Advisories remain
in place for Thursday and Friday for heat related risks. The
latter should be the warmer day, with temperatures reaching 100 or
better across portions of the Eastern Magic Valley.
Ridge stays amplified into the weekend, but shows signs of
flattening somewhat Sunday. Models have been trending slower with
the deamplification of the ridge, which will have the tendency to
maintain the warmer temperatures longer. Guidance does start to
trickle lower Saturday and Sunday but if the trend continues,
expect a nudge upward and a potential extension of the heat risk
related headlines. Expectations are still for passage of dry cold
front early in the week. Models appear to be pinpointing late
Monday or Monday night. At this time, only impact still appears
to be an uptick in winds for Tuesday. If the feature can pick up
some additional moisture, we may have to adjust precipitation
chances upward. Until then, dry and continued warm/hot summer
conditions will be the theme. DMH
.AVIATION...With some left-over thunderstorms along the border
with Montana, as far south as Idaho Falls, although mostly in the
mountains and highlands, will occur this afternoon and evening. But
that will be the end of thunderstorms for a few days as a very
strong high pressure moves into the northern Great Basin. It will
bring very hot air into southern Idaho, and by Fri temperatures will
approach record territory, with some low elevations reaching 100
degrees F. With the ridge axis directly overhead, wind will be
nearly all diurnally and slope-driven and should remain light with
little to no upper level support. This all starts to change once the
upper level ridge axis slides eastward and allow a Pacific low to
move eastward. This will put stronger southwesterly flow overhead,
and on Mon or Mon night a very dry cold front may work its way
through the longwave ridge, breaking it down over eastern Idaho.
After the extreme warmth and drying, it will be very likely that
critical fire weather conditions should result. For the remainder of
the seven days, wind subsides and the high pressure returns. Only
the extreme northeast end of the Targhee NF has any threat of
convection on Tue/Wed. Messick
.FIRE WEATHER...TSRA expected to develop in the neighborhoods of KIDA
and KDIJ. The HRRR has been consistent in bringing thunderstorms
through the KIDA area around the 30/03Z timeframe, and 1 to 2 hours
later in the KDIJ vicinity. Otherwise, expect light wind and no CIG
with unlimited VSBY everywhere else under strengthening high
Heat Advisory from midnight Thursday night to midnight MDT
Friday night for IDZ052-054>057.
Heat Advisory from midnight tonight to midnight MDT Friday night
Area Forecast Discussion
National Weather Service Pueblo CO
756 PM MDT Wed Jul 29 2020
Issued at 753 PM MDT Wed Jul 29 2020
Updated forecast for the cancellation of the remaining counties in
Severe Thunderstorm Watch 404, which include Kiowa, Prowers, and
UPDATE Issued at 457 PM MDT Wed Jul 29 2020
Updated forecast for the removal of Bent County from the Severe
.SHORT TERM...(This evening through Thursday)
Issued at 245PM MDT Wed Jul 29 2020
An upper level ridge will remain centered over northwest AZ thru
Thu. This evening an upper trof is forecast to move from northeast
WY, into western NE, and then into western KS and far eastern CO Thu
Radar/satellite/lighting data are showing isolated showers and
storms across the area as of 2 PM, and unlike the last couple days,
there is less moisture to work with and storms are faster moving.
However over the far southeast plains, dew points are in the upper
50s to lower 60s and the latest SPC mesoanalysis shows 2000-3000
J/kg of CAPE over that area. We have already seen a strong storm
over southern Baca County this afternoon, with more storms expected.
The HRRR and 4km NAM nest show the best potential for strong to
severe storms over the eastern border areas through about 23Z to 00Z
and then moves these east of the area. Hail up to ping pong ball
size and wind gusts in excess of 60 mph will be the main severe
risks in counties near the eastern CO border. Although it is drier
over the mtns today, if a stronger storm moves over a recent burn
scar, especially the Spring or Decker, there could be a flash flood
risk. The HRRR dries out the forecast area by 01Z this evening, and
the NAM nest is similar, maybe just some isolated light activity for
another hour or two longer than the HRRR indicates.
On Thu with the upper trof moving south into the area, breezy
northerly winds are expected, especially over the plains. The
morning looks dry in all areas, and then in the afternoon it looks
like storms could be seen over the eastern border areas where the
best moisture and instability will be. The GFS also shows good
chances for precip over the Pikes Peak/Palmer Divide regions in the
afternoon and evening, and then spreading along and adjacent to the
eastern mtns by evening. Western areas look dry on Thu
.LONG TERM...(Thursday night through Wednesday)
Issued at 245PM MDT Wed Jul 29 2020
.Friday through Monday...This period will have the upper ridge
west of Colorado, in the vicinity of the Great Basin, with an
upper trough over the Midwest. As a result, expect periodic
frontal passages over the eastern plains and eastern mountains
with upslope flow advecting moisture into the region from the
east. Northwest flow aloft will not tap the deeper subtropical
moisture to the south, but there will be some residual moisture in
the mid levels. The precipitable waters will range from 0.75 to
1.25 over the eastern mountains and eastern plains with daily
fluctuation depending on the amount of low level moisture.
Current models and ensembles suggest Saturday may be the drier day
in this period. The main question will be the amount of
instability for diurnal convection. Bufkit soundings suggest the
best chances for diurnal convection will be over the mountains
with chances decreasing to the east, where the atmosphere will be
more likely capped. The precipitable water amounts are high enough
for some locally heavy downpours, and there is a risk for burn
scar flash flooding from these stronger storms. Temperatures will
be cooler in the plains with the persistent upslope flow. Easterly
upslope may be deep enough for the low level moisture to reach
into the San Luis Valley and the Upper Arkansas River Valley,
increasing chances for convection and heavier rainfall in these
areas. Where the low level moisture does not reach, expect high
based convection with less rainfall.
.Tuesday and Wednesday...Models and ensembles suggest the upper
high will drift eastward with the flow aloft becoming more
westerly. The increased westerly flow will bring warmer and drier
air aloft into the region. In addition, this will lead to drying
of the lower levels on the plains with weakening of the upslope
flow. Grids show a general drying and warming trend for these
.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 245PM MDT Wed Jul 29 2020
VFR conditions are expected the next 24 hrs at KALS, KPUB and KCOS.
Gusty west to northwest, or north winds are expected into tonight at
KPUB and KCOS. There could be a couple showers/storms in the
vicinity of KPUB and KCOS this evening causing gusty erratic winds.
KALS could see showers and storms in the vicinity through about 02Z.
Isolated storms could develop in the late afternoon hours at KCOS
and KPUB on Thu. Gusty northerly winds are expected from the
morning through the afternoon Thu at KCOS and KPUB, and in the
afternoon at KALS.