Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/11/18
Area Forecast Discussion
National Weather Service Bismarck ND
825 PM CDT Mon Sep 10 2018
Issued at 825 PM CDT Mon Sep 10 2018
Appears the latest HRRR and NAMNEST are initializing quiet well
with the current radar, and are similar to each others
reflectivities overnight, both in time and coverage. Isolated
showers/possible thunderstorms soon, in far northeastern Montana
are now beginning to push into Divide County. The HRRR and NAMNEST
take this activity along the border then into southern Canada.
Both models develop elevated isolated showers/thunderstorms within
Mountrail and Ward counties between 05z and 07z, then continue to
intensify and push the thunderstorms into Bottineau/McHenry/Pierce/
and Rolette counties between 07z-12z. It is during the 07z-12z
time period that the elevated thunderstorms will have their highest
probabilities for severe potential. During this time, elevated
0-3km Most Unstable (MU CAPE) ranges between 1500 J/Kg per GFS
to around 2500 J/Kg per NAM. This instability will be co-located
within 0-6km Deep Layer Shear of 45kt. Large hail to quarter size
(one inch diameter) will be the main threat.
For this update, will broaden the current areal coverage of PoPs
based on the latest HRRR/NAMNEST solutions and current trends, and
increase PoPs in the far north central/Turtle Mountains during
the 07z-12z timeframe.
UPDATE Issued at 533 PM CDT Mon Sep 10 2018
Latest satellite imagery shows mid/high clouds overspreading
southern Saskatchewan, with low level southerly winds advecting a
cumulus now over eastern Montana northward. This is indicative of
the stronger low level winds that will quickly spread across
western and central ND this evening through the overnight period.
Warm air advection/elevated convection will develop at some point
this evening, most likely between 03z and 06z, reaching peak
intensity between 06z-12z as the whole thunderstorm area scoots
into the Turtle Mountains. CAM`s agree with the above trend later
tonight, but initial development early tonight, both in timing
and location could be in several different locations across
portions of western and north central ND. Previous gridded
forecast elements has these ideas handled well, and will not make
any changes at this time. Large hail remains as the primary threat
which is generally the case with elevated convection at night.
.SHORT TERM...(This evening through Tuesday)
Issued at 134 PM CDT Mon Sep 10 2018
Main forecast issue in the short term period will be Thunderstorm
Sunny skies across western and central North Dakota this afternoon
with upper level ridging over the area, ahead of a shortwave
trough and associated cold front that move into the region tonight
and exit the area Tuesday.
The shortwave, currently located along the British
Columbia/Alberta border north of Washington, will track across
southern Canada tonight, In response, a strong low level jet will
develop across western and central North Dakota. Strong warm
advection associated with the low level jet, combined with
moderate to strong instability aloft, will provide a focus for
thunderstorm development mostly after midnight over north central
ND. Current suite of CAMS show a general area of convection
confined to areas east of a line from Kenmare to Garrison, with
the strongest convection over the Turtle Mountains into the Devils
Lake Basin. Given the amount of instability aloft, stronger cells
would have the potential for some large hail. Being the storms
will be elevated, that is expected to be the main threat late
tonight into early Tuesday morning.
The associated cold front moves into western-central ND by mid-
morning Tuesday and into eastern ND by Tuesday afternoon. The
atmosphere is expected to become quite unstable Tuesday afternoon
from eastern South Dakota into northern Minnesota, including
portions of south central and eastern ND. With the shortwave
lifting across southern Canada, the cold front will be the main
focus for thunderstorm development. We will be capped over the
eastern Dakotas, so the threat of severe weather looks minimal at
this time. Should the frontal boundary slow down and we get more
surface heating ahead of the front, the potential for
thunderstorms may increase. But even then, the greatest threat
looks to be for the James River Valley and especially points east.
.LONG TERM...(Tuesday night through Monday)
Issued at 134 PM CDT Mon Sep 10 2018
We remain within an active weather pattern through much of the
long term period. Initially we start out pretty quiet Tuesday
night as surface high pressure traverses the forecast area. By
Wednesday afternoon, a surface low pressure area develops over the
northern high plains with a broad southwest flow across all of
western and central ND. The surface low and associated warm front
will be a focus for showers and thunderstorms, especially
Wednesday afternoon through early Thursday morning. At this time
there are some model differences with where this boundary sets up,
but we should see abundant moisture and enough forcing to
initiate thunderstorms over the area. The threat of severe weather
is also possible along and north of the warm front but will
probably taper quickly the farther you go north into the cool
A cooler airmass builds over the area Thursday through the weekend
and even into early next week. Temperatures will be noticeably
cooler, especially north with a potential for frost not out of the
question northwest and north central. The threat of shower
activity will continue however, with the upper flow remaining out
of the southwest. Thunderstorm chances beyond Thursday appear
minimal at this time.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 533 PM CDT Mon Sep 10 2018
A warm front across southern Canada and strong low level southerly
winds will result in low level wind shear across KDIK/KBIS/KMOT
from approximately 05z-13z Tuesday. A vcsh was added to KMOT
between 06z-09z, and will be monitored for thunderstorm
development, although at this time the majority of thunderstorms
will favor locations outside of the northern terminals - but again
this will be watched closely early tonight for any changes.
Otherwise, a cold front will sweep from west to east late tonight
through Tuesday afternoon, prompting a wind shift from southwest
Area Forecast Discussion
National Weather Service State College PA
1113 PM EDT Mon Sep 10 2018
The remnants of Tropical Depression Gordon will move into
southern Ontario today, then down the St. Lawrence River valley
tonight and Tuesday. The trailing cold front will move through
the region tonight. High pressure and a period of drier weather
will follow for mid week.
There is the potential for the region to be impacted by
Hurricane Florence by the end of the week or next weekend,
though the biggest impacts look to remain south of the state.
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Sfc occlusion moving across the Alleghenies late this evening.
A persistent area of showers along and ahead of it extends from
southwest PA through the Endless Mountains of northeast PA.
Hourly amounts remain light, and are a far cry from the heavy
amounts the HRRR was pumping out late this afternoon and
evening. Allowed the Flood Watch to expire on time at 00z, with
non-waterway flooding slowly decreasing overnight. Aforementioned
front takes its time working eastward overnight, and may still
be over the Susq Valley early Tuesday morning. Rain showers
persist much of the night over the NE/E sections of CWA, while
tapering off to lighter rain/drizzle elsewhere as LLJ lifts
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
High pressure will begin to build in for Tuesday. Though we will
start off rather gray/damp and drizzly, the afternoon promises
to be brighter (though still mainly cloudy) and certainly warmer
than we have been for a couple of days. Could see scattered
showers lingering over the SE as frontal boundary lingers.
Heights build Tue night into midweek as ridge settles in over
PA with surface high located to our north.
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
After being mainly dry early, sprawling high pressure off to our
north promises to create a persistent easterly maritime flow of
moist air for mid week onward.
The strength of the upper ridge will be all important in how
far north and west Florence will go. With the wet summer we
have had, any additional heavy rains coming out of the tropics
would be a challenge for all involved.
Latest guidance has Florence going ashore near Wilmington NC
Thursday evening before slowing down as it moves inland. It
remains to be seen how much of a direct influence this will have
locally, or if some sort of frontal interaction with the
tropical moisture can develop north of the storm. All eyes will
certainly be on this potentially very dangerous hurricane.
Temperatures will begin to rebound by the Tuesday through
Thursday timeframe. As mentioned above, with the influence of
Florence so uncertain, the forecast for the end of the period is
a rather bland mention for small chances of showers.
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
A slow moving frontal boundary, combined with a moist easterly
flow off of the Atlantic Ocean, will result in widespread low
cigs, occasional drizzle and scattered showers tonight.
Observations at 03Z are showing cig heights mostly between
500-1000ft and model soundings support the idea of lowering
stratus overnight, with predominantly ifr/lifr conditions
Improving flying conditions are anticipated Tuesday, as high
pressure builds in from the Grt Lks. SREF/HREF prob charts
indicate improvement will come first across the central portion
of the state (KAOO/KUNV/KIPT), where cigs should improve to
mvfr or low vfr by late morning. Improvement could take longer
along the spine of the Appalachians (KBFD/KJST) and near the
exiting front over southeast Pa (KMDT/KLNS). However, even there
improvement appears likely by afternoon. Can`t rule out an
afternoon thunderstorm at KLNS in vicinity of stalled cold
Wed...AM low cigs/fog possible, mainly northern mountains.
Isold PM tsra impacts possible southeast Pa.
Thu-Fri...Patchy AM fog possible. Isold PM tsra impacts
Sat...Patchy AM fog possible. PM rain/low cigs possible southern
Long duration rain event bringing significant rises on area
streams/rivers filling them to bankfull. Many small streams and
creeks are experiencing at least minor flooding, with even some
of the larger rivers seeing notable rises as well.
LONG TERM...La Corte/Tyburski
Area Forecast Discussion
National Weather Service Glasgow MT
916 PM MDT Mon Sep 10 2018
Going forecast was generally in good shape. Some showers this
evening in Sheridan County got some low-end POPs, and the RAP
seems to want to develop some showers in western Roosevelt and
Daniels Counties tonight, so I covered those with low-end POP as
well. Added some POPs early following radar trends for showers
moving out of Blaine into Phillips Counties as well.
Previous discussion follows...
Afternoon Update (230pm MDT): The story remains generally similar
to that of the morning forecast. Some uncertainty is present yet
in timing and placement of the expected consecutive precipitation
systems from late Tuesday night through the weekend. Some model
solutions are putting out much higher QPF numbers than this
morning, so the forecast was upped somewhat to match. Otherwise,
much of the rest of the forecast consisted of minor tweaks to
already established grids including the morning and midday model
PREVIOUS DISCUSSION: Upper ridging will help guide warm and dry
conditions across the region for today. Large scale subsidence and
height rises will be the force behind highs in the 80s and partly
to mostly sunny skies through the afternoon, however, as the
ridge axis slides downstream of the CWA clouds could begin to
increase. Additionally, a very subtle shortwave is evident in some
of the height field analysis shown in the latest 00z model runs.
This could locally increase clouds near the Montana/North Dakota
border for a time this afternoon and evening. While Bufkit
soundings show a little CAPE, overall there is very little
moisture in the vertical column available and the thinking is
shower development should be kept at a minimum. That said, the GFS
would support isolated coverage, but for now decided to play it
safe and trend toward consensus guidance.
For tonight, a dry cold front will slide through the region
leading to a wind switch to the northwest and an increase in
speeds to a 10 to 20 mph range. While breezy, conditions should
remain shy of Lake Wind Advisory criteria out on Fort Peck Lake.
Tuesday night and onward: models show an overall more active
pattern setting up across the region. With a trough deepening over
the western U.S., southwest upper flow will help guide more
frequent shortwaves toward and through northeast Montana. Timing
and placement/track of these specific shortwaves at larger time
scales is difficult at best. Thus, while chances for
showers/thunder may begin to increase for the second half of the
week, there is yet very little confidence on coverage,
precipitation amount, location, etc. at this time. Early signs
seem to point most favorably across the northwest zones or
locations along the Canadian border, but this very well could be
adjusted in the coming days. For now, consensus blends produced
pops that capture these ideas while underscoring the inherent
uncertainty rather well. Thus, little deviation from the models
was needed at this point for the longer range. As confidence
increases and targets of opportunity more clearly present
themselves, more details will be able to be better reflected in
future forecasts. Maliawco
FLIGHT CAT: VFR
DISCUSSION: A dry cold front pushes through tonight, with erratic
winds being the main potential impact.
WIND: The cold front will shift winds to the northwest after
midnight and speeds are expected to remain generally 7-12 kts but
gusty at times. Winds will generally be out of the northwest on
Area Forecast Discussion
National Weather Service Midland/Odessa TX
605 PM CDT Mon Sep 10 2018
Please see the 00Z aviation discussion below.
At issuance, thunderstorms are ongoing across SE NM and affecting
HOB. High-res models do not have a good handle on these storms,
though expect activity to remain east of CNM, thus will monitor
trends and amend as needed this evening. Variable, gusty winds and
MVFR/IFR conditions in heavy rain are possible with storms the
next couple of hours, with weakening expected after sunset. VFR
conditions will otherwise prevail, with light southeasterly winds
through the forecast period.
.PREV DISCUSSION... /issued 245 PM CDT Mon Sep 10 2018/
WV imagery shows an upper-lvl trough extending from the Great Lakes
region down into central Texas. To the west, an elongated ridge
extends from the ern Pacific into the SW CONUS, leaving meridional
flow aloft over West Texas and Southeast New Mexico. A trough moved
thru this flow last night, bringing a batch of convection down into
SE NM overnight, and is over the South Plains as of 18Z, about to
merge w/the larger trough over central Texas. Both the NAM and GFS
place these features well, but both suggest ongoing convection over
nrn Lea County...which is not happening. However, hi-rez models
such as the HRRR and WRF suggest a slight chance of convection
cannot be ruled out later this afternoon and into the overnight
hours. Latest mesoscale analysis shows a bullseye of 2000 J/kg
sbcape and radar has faint activity trying to get going invof KHOB.
Over the next few days, the upper trough is forecast to drift se
into south Texas, to be replaced by the ridge nosing in from the
WSW. This will result in thicknesses/temps increasing to above-
normal by Wednesday, where they should remain AOA normal thru the
extended. Models are coming into better agreement in bringing an
inverted trough onshore and under the ridge thru south Texas,
introducing a chance of convection into the se zones beginning
Saturday. POP blends still look a little high, and we`ll continue
toning them down some. Some of the longer range models hint at
bringing a cold front into the area Sunday night or so but,
considering the time of year, we`d like to see a bit better
agreement before jumping on that.
.PRELIMINARY POINT TEMPS/POPS...
Big Spring 61 85 65 88 / 0 0 0 0
Carlsbad 62 86 62 90 / 10 0 0 0
Dryden 67 85 68 87 / 0 0 0 0
Fort Stockton 62 86 63 88 / 0 0 0 0
Guadalupe Pass 60 82 62 86 / 10 0 0 0
Hobbs 58 83 60 86 / 20 0 0 0
Marfa 55 81 55 85 / 0 0 0 0
Midland Intl Airport 63 85 65 88 / 0 0 0 0
Odessa 62 85 65 88 / 10 0 0 0
Wink 63 87 64 90 / 10 0 0 0
Area Forecast Discussion
National Weather Service Melbourne FL
911 PM EDT Mon Sep 10 2018
Fairly warm temperatures aloft along with substantial high
cloudiness limited overall convective coverage for most of the day
across east central Florida. However, a late day collision
between the east and west coast sea breezes resulted in scattered
lightning storms across the interior.
For the rest of this evening into tonight...interactions from
various outflow boundaries could result in additional storms
mainly across the interior, but with the loss of daytime heating
showers and storms will be on the downward trend. Previous forecast
in good shape with the HRRR and local WRF showing some storms
sticking around through late evening with some lingering debris rain
through midnight or so. Only minor changes made based on radar
trends. Overnight lows will be once again in the low to mid 70s.
Tuesday (previous)...A deep layer high pressure ridge will extend
over the Florida peninsula and the Bahamas while Hurricane
Florence transits the Atlantic between Bermuda and the Bahamas.
Moisture is still progged to be quite high with precipitable water
1.8 to 2.0 inches. 500mb temps still look to be around -7C, so
these parameters should usually produce above climo PoPs. However,
forecast soundings show that there will be considerable cirrus
debris clouds streaming across the area from a tropical
disturbance in the northwest Caribbean. These clouds are already
evident over far south Florida and appeared to be stunting
convection. For now, will stick with the previous forecast of 40%
interior and 30% along the coast, though MOS values are only
VCTS across interior terminals through late evening with some
lingering debris through midnight/04Z or so. VFR conditions for
the rest of tonight. Weak pressure gradient will again allow for
fairly light winds on Tuesday. VCSH during the afternoon along the
coast and VCTS for interior sites with the west and east coast
sea breezes meeting up across the interior.
Tonight-Tuesday...A weak high pressure ridge to our south will
result in a light southwest-west flow before the ridge builds to
the north on Tuesday. The weak pressure gradient will keep winds
below 10 knots with winds turning easterly in the nearshore waters
as the sea breeze forms in the afternoon hours. There will be
negligible wind waves and distant long period swells from Florence
will continue 3-4 feet over the waters.
.HYDROLOGY...The Saint Johns River at Geneva and Astor will remain
above action stage this week.
.PRELIMINARY POINT TEMPS/POPS...
DAB 74 89 75 88 / 20 30 10 30
MCO 75 91 75 90 / 40 40 20 40
MLB 74 89 76 88 / 20 30 10 30
VRB 74 89 74 88 / 20 30 20 30
LEE 75 92 75 91 / 20 40 30 30
SFB 75 92 75 91 / 40 40 20 30
ORL 75 91 75 90 / 40 40 20 40
FPR 73 88 74 88 / 20 30 20 30
ZCZC WRKAFDMLB ALL
TTAA00 KWRK 020201