Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/02/19
Area Forecast Discussion...Updated
National Weather Service Billings MT
840 PM MDT Sun Sep 1 2019
Strong convection from late this afternoon and very early this
evening, has left the state. There were some lingering clouds over
the far southeast, indicative of some instability left over from
the convection. Shortwave energy has pushed east, but another wave
was in western Montana and progged to slide across the northern
half of the state overnight. Models were not very bullish on QPF,
especially some of the high resolution ones, but can see the
legitimacy of keeping some PoPs over parts of southeast Montana
tonight as mid level warm advection interacts with a fairly weak
low level jet. Have fine tuned the PoPs to account for less of a
risk of convection and confined it mostly to the far southeast.
HRRR still advertising the potential for some fog over eastern
parts of Fallon and Carter counties Monday morning, so will leave
that in. TWH
.SHORT TERM...valid for Mon and Tue...
Did not make any large changes to the previous forecast. An upper
ridge remains over the area tonight, with an inverted surface
trough over the eastern zones. A low-level jet develops over the E
this evening and shifts E overnight. MLCAPES will be around 1000
j/kg this evening in the E per SREF with effective Bulk Shear
greater than 40 kt. The high CAPES and shear shift E of the area
late tonight/early Monday. PWAT`s will also be over an inch in the
E. Kept chance PoPs in the E this evening, and shifted PoPs into
just KBHK area overnight per HREF QPF. Will keep mention of small
hail/gusty winds with storms through the night based on the above.
RH recoveries looked a little better than they did yesterday and
will range from the 40s W to the 80s E. After checking RAP
soundings and HRRR, cannot rule out patchy fog and stratus moving
into the KBHK and Ekalaka areas again late tonight.
The ECMWF ensembles showed uncertainty with the synoptic pattern
Monday through Tuesday, while GEFS spaghetti plots had spread Mon.
night through Tue. night. Thus timing, placement and strength of
features was a bit uncertain. In general, expect a weak trough to
move through the region on Mon. into Mon. evening, with ridging
rebuilding Tue. and Tue. night. A second trough may affect the
area late Tue. night. A cold front will drop S through the area
Mon. afternoon. It will be hot and dry on Mon. with RH`s in the
teens from KBIL-KSHR W...and 20s to 40s E of this line. Winds
still look to become gusty from the NW behind the front Mon.
afternoon and will continue to be strong in the evening. Raised
PoPs a bit Mon. evening with frontogenesis and moisture behind the
front. Shifted PoPs SE and decreased them overnight. Did not see
any CAPE Mon. night, so kept only a mention of thunder. RH`s will
come up during the evening hours. Since the fuels are not
critical, will continue to just headline the FWF with expected
Tuesday will be cooler with higher humidities. No precip.
expected, except a slight chance in the Beartooths/Absarokas. It
will be mostly dry Tue. night. Arthur
.LONG TERM...valid for Wed...Thu...Fri...Sat...Sun...
Wednesday and Thursday will generally warm and dry as a high
pressure builds back into the area. Highs will be in the upper 80s
to lower 90s. Friday will see flow aloft turn southwesterly as a
another wave moves into the Northern Rockies. Afternoon showers
and thunderstorms will develop as the energy and moisture move
into the area. For the weekend and into early next week the
pattern will turn towards a more unsettled and troughy pattern.
This will result in temperatures remaining generally in the mid to
upper 70s. Chances mainly in the afternoon and evening each day
for showers and thunderstorms remain. Reimer
VFR conditions will prevail through the period with passing mid
and high clouds. Overnight showers or thunderstorms are possible
east of a line from KMLS to 4BQ, but this activity will be
isolated to widely scattered. Patchy morning fog is also possible
around KBHK Monday, which would briefly limit conditions to MVFR
.PRELIMINARY POINT TEMP/POPS...
Mon Tue Wed Thu Fri Sat Sun
BIL 061/094 057/084 058/092 059/087 058/079 054/078 054/078
00/U 30/U 10/U 12/T 33/T 31/B 24/T
LVM 052/090 048/086 051/090 052/085 050/079 048/079 048/075
00/N 20/U 10/U 14/T 64/T 32/T 35/T
HDN 059/092 054/082 056/091 057/087 057/078 052/077 052/079
00/U 30/U 10/U 11/U 33/T 32/T 23/T
MLS 062/089 054/077 055/088 057/085 056/075 051/073 051/075
20/N 20/U 10/U 11/U 22/T 32/W 23/T
4BQ 061/091 054/078 055/089 056/086 056/076 051/072 050/075
10/U 20/U 00/U 11/U 23/T 42/T 23/T
BHK 058/087 052/075 050/085 054/083 052/073 047/069 046/071
31/B 10/U 00/U 10/U 22/T 42/T 23/T
SHR 058/093 053/082 055/090 055/087 055/078 050/076 050/079
00/U 31/U 10/U 12/T 43/T 42/T 34/T
Area Forecast Discussion
National Weather Service State College PA
1016 PM EDT Sun Sep 1 2019
Moist air is flowing into the area ahead of a cold front which
will push southeast through the area late Monday. A more
significant cold front will arrive Wednesday. High pressure is
likely to build southeast into the region late next week, as
Hurricane Dorian tracks along but just off the Mid Atlantic
.NEAR TERM /UNTIL 9 AM MONDAY MORNING/...
First line of storms is much weaker now, but some heavy rain
concerns still exist with multiple clusters of moderate rain
with small pockets of heavy rain. Recent runs of the RAP and
HRRR have begun to move the precip along steadily, with the
heaviest associated with the first line. One bow echo starting
to form a county or two to our west, but some stabilization due
to light rain and loss of heating may be occurring before that
feature can move over the land in front of it. Wettest location
in the CWA is the NW where the precip will likely be heaviest
over the next 2-3 hrs. Will continue to monitor for minor
flooding problems, but FFG remains fairly high.
Very potent shortwave trough moving through OH seen on WV
imagery is driving clusters of thunderstorms, many of them have
been severe over Central OH and into ern OH, now. Earlier storms
have had the help of the daytime heating, but with sunset, that
is obviously not the only reason these things are still going
strong (and perhaps getting worse). Have only made tweaks to
the near term PoPs/Wx/QPF, but may have to add mentions of SVR
winds, too, for the western zones. May get busy before too long.
Might have a threat for flooding, too, as these storms would be
passing over ground wettened earlier today in our NWrn
Two persistent areas of showers have been maintained from the
late morning through mid afternoon hours, the first over the
Northwest Mountains and the other from the South Central
Mountains lifting into the Ridge and Valley Region. It has been
a wet day in both of these locations with some areas seeing in
excess of one half inch of rainfall. Elsewhere, skies have been
mostly cloudy with very little in the way of rain just yet. That
will be changing tonight, as the deepest moisture and forcing
coincide over Central PA.
Mid level shortwave and associated plume of anomalous PW and a
slow moving 850 mb jet traverse the area from late this evening
through 12z. This will keep the highest POPS of near 100pct
across the northwest mountains under axis of low level jet, with
the lowest chance across the southeast counties. Already seeing
some brief mdt-hvy downpours in some of the southern activity,
but cell motions so far have precluded any flooding concerns
(that and recent dryness). Still, as moisture flux continues and
additional instability is added to the mix, there is the
potential for localized one inch plus amounts (and some CAM
solutions show in excess of 2-3" in spots). Still believe the
threat for flooding is quite low given recent dry weather and
high FFG numbers.
Mins tonight will range from the upper 50s north to the mid 60s
.SHORT TERM /9 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
Best forcing for showers on Monday remains during the morning as
aforementioned shortwave and boundary layer jet at 12z push off
to the east by afternoon as surface warm front lifts northward
across the region. Brightening skies are anticipated by
afternoon, as we break into the warm sector. Scattered afternoon
thunderstorms will be possible in the increasingly unstable air
mass ahead of a weak cold front pressing southeast from the Grt
Lks. Moderate instability progged by both the GEFS and HREFV2,
combined with decent mid level flow has put parts of central and
eastern PA in MRGL Day 2 SPC Outlook on Monday. Maxes will range
from the lower 70s north to the lower 80s southeast.
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Made a few small changes to this part of the package.
Main thing was to go with dry conditions next Sunday, as wave
on the cold front is likely to stay just south of the area. Can
change this in the coming days if needed.
Other change was to push showers a tad further northwest later
Thursday into Friday, as moisture from the southeast could be
pulled across southeast PA.
First cold front moves east of the area by Tuesday morning.
Weak high pressure builds into the area with dry conditions for
A stronger cold front moves into the area from the upper Great
Lakes, as a strong upper level jet lifts northeast across
eastern Canada. Will have to look this over as we get closer to
Wednesday, as the combination of trailing jet max and timing of
the front could lead a a few strong storms.
Cooler air at low levels is advected from the northeast on
Thursday, as high pressure builds into the area. Temperatures
will run a few degrees below normal.
Another strong cold front moves across the area the first part
of next weekend, with limited moisture. Another large high
pressure builds into area behind this cold front. Temperatures
behind this front will be colder, upwards of 5 to 10 degrees
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Widespread restrictions are expected overnight, as ceilings are
expected to gradually drop to IFR. A more robust area of
showers will push into the area overnight as well. The breeze
will gradually veer from southeasterly to a more southerly
Unsettled weather will persist into Monday, as a weak cold
front crosses the area. Ceilings will slowly improve, but some
restrictions could persist through the day. Thunder is possible
by afternoon, especially across the south and east.
High pressure will provide improved conditions for Tuesday,
before another cold front approaches on Wednesday.
Mon...Reduced cigs/vsbys in scattered SHRA/TSRA.
Tue...AM low cigs/fog possible, then becoming VFR.
Wed...Reductions possible by aftn in scattered SHRA/TSRA.
Thu-Fri...Generally VFR, although showers could sneak into the
Area Forecast Discussion
National Weather Service San Diego CA
100 PM PDT Sun Sep 1 2019
High pressure aloft will continue very warm conditions most of this
week. Monsoonal flow and warm coastal waters will result in
generally humid conditions as well, and the monsoonal flow will
bring chances of mainly afternoon and evening thunderstorms over the
mountains and deserts, especially Monday through Wednesday when a
few storms could drift west of the mountains. Night and morning low
clouds will mainly be less extensive most of the rest of the week. A
trough of low pressure off the coast will likely bring drier air and
some cooling though also an increase in the marine layer low clouds
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
Stratus was still widespread over the coastal waters and beaches but
have cleared over land. Some mid-high clouds from the southeast were
drifting over land as well. Cumulus was forming over the mountain
crests, but no thunderstorms had formed yet. Models do not have much
explicit precipitation for this afternoon, with some HRRR runs even
keeping us dry, but a few thunderstorms should form this afternoon,
mainly over the mountains and desert slopes in San Diego and
Riverside County where SPC mesoanalysis shows some CAPE over 1000
The upper high will continue roughly over the Four-Corners region
through Thu or Fri, with a weak inverted trough moving west to our
south Monday. Most ensemble solutions show Tropical Storm Juliette
staying well to the south, except for a few GEFS solutions showing
remnants approaching from the south next weekend when a Pacific
trough moves into California from the west. NHC guidance keeps it
south of the Tropic of Cancer through Friday, and this should have
little or no impact here. What we will have is high amounts of
moisture (RH > 70%) in the 700-500 MB layer especially Mon/Tue and
moderate amounts of moisture (RH > 50% at times) even below that,
with some decreases Wed, especially below 700 MB. Total precipitable
water could exceed 2 inches both along the coast and in the lower
deserts. Instability will be sufficient for thunderstorm
development, with surface-based CAPE over 1000 J/kg at times. With
all the moisture and instability, there is a concern of local flash
flooding from heavier rains either Monday or Tuesday. Mid-level
winds will be moderate, 10-20 knots, which won`t be enough to
inhibit heavy rains. A few storms could drift west of the mountains
Monday or Tuesday, but this mostly will be confined to the Elsinore
Convergence Zone, especially since any upper level trigger would
appear to weak to spark the moderate amounts of elevated CAPE in the
700-500 MB layer. Some thunderstorm chances will remain through
Friday but should diminish by Saturday as the trough moving into
California will bring drier southwest flow. The marine layer
stratus, after its stronghold this morning, should be less notable
Monday and Tuesday due to the moisture aloft increasing the long
wave radiation reflected back to the surface. Temperatures should
decrease slightly Monday, though only by a few degrees, and the heat
advisory for the Inland Empire and excessive heat warning for the
high deserts will be allowed to expire tonight. Some renewed warming
west of the mountains Tue/Wed may be enough to require an excessive
heat advisory again in the Inland Empire as a lot of areas will
likely be over 100.
012000Z...Coast...VFR conditions should prevail at the terminals
through midnight tonight, however patchy stratus will linger on the
beaches and may generate brief periods of BKN CIGS at any of the
coastal terminals. SCT-BKN high clouds AOA 15,000 FT MSL and a
decrease in onshore flow will help suppress stratus coverage
tonight. Leaning toward prevailing VFR at the terminals overnight,
but periods of BKN CIGS with bases 400-900 FT MSL cannot be ruled
out. CIGS most likely in coastal San Diego County, and between 10-
Mountains/Deserts...Scattered Cu over the mtns this PM with bases
near 10,000 FT MSL. Slight chance of SHRA/TSRA through 02Z, mainly
for SD and RIV County mtns. Otherwise, SCT-BKN clouds AOA 15,000 FT
MSL through Monday AM.
No hazardous marine conditions expected through Friday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
CA...Excessive Heat Warning until 8 PM PDT this evening for Apple and
Heat Advisory until 8 PM PDT this evening for San Bernardino and
Riverside County Valleys-The Inland Empire.