Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/18/18
Area Forecast Discussion
National Weather Service Bismarck ND
900 PM CDT Tue Apr 17 2018
Issued at 850 PM CDT Tue Apr 17 2018
Mesoscale models continue to trend farther west with snow. 18Z NAM
keeps any snow accumulation west of Bismarck and Minot. And the 18
April 00 UTC RAP and HRRR keep accumulations well west of Bismarck
and Minot. Utilized a blend which still kept a couple tenths in
Bismarck but kept Minot dry. Overall theme here is precipitation
remains confined to the vicinity of the inverted trough, which
continues to weaken overnight and Wednesday. Heaviest snow totals
remain in this area, from around Crosby and Tioga, through eastern
Dunn county and between Dickinson and Hebron and south into South
Dakota. Generally an inch amounts in this area, maybe up to 1.5
inches. Snowfall tapers quickly as you go east or west of this
line. Updated text products will be sent shortly.
UPDATE Issued at 540 PM CDT Tue Apr 17 2018
Quick update to update pops/qpf. Latest 18Z medium range model
guidance and latest mesoscale models continue to trim back on the
eastward extend of precipitation and total qpf with this system.
Utilized a blend of latest mesoscale guidance with current
Superblend and medium range models. This delays higher pops and
precip around Bismarck/Mandan until after midnight and knocks
back snow totals to around a half inch (in Bismarck/Mandan). This
may even be overdone if trends continue, but at least a good
start. Still may see an are of 1-2 inches but likely in a narrower
band. Updated text products will be sent shortly.
.SHORT TERM...(This evening through Wednesday)
Issued at 220 PM CDT Tue Apr 17 2018
Light rain will continue moving eastward from eastern Montana into
western and central North Dakota this evening. Expect light rain
to change over to light snow later this evening as the forecast
NAM BUFR soundings show temperatures falling below freezing
throughout the entire column with a saturated snow growth zone.
The forecast NAM sounding in Bismarck for 12z matches the observed
12z sounding very well, so confidence is high that the NAM will
continue performing well into tonight.
Light snow will likely continue through tonight and into tomorrow
morning as a convergence zone with associated mid-level
frontogenesis becomes nearly stationary over central North Dakota.
Any leftover snow will change back over to light rain during the
late morning and early afternoon tomorrow as surface temperatures
warm into the 40s for most spots. Expect a trace to an inch or two
of snow accumulation from most of western and central North Dakota
by tomorrow afternoon.
Conditions dry out tomorrow afternoon and evening as a surface
high pressure system begins building in from the west.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 220 PM CDT Tue Apr 17 2018
High pressure will dominate western and central North Dakota
Wednesday night through Thursday night, making for calm weather.
Some leftover clouds will keep temperatures in the 40s and lower
50s on Thursday. A split flow pattern with a large upper- level
low over the four-corners region will prevail on Friday, giving
southern North Dakota a slight chance of light rain for Friday
and Friday night.
A ridge will build over North Dakota on Saturday and Sunday,
leading to sinking motion and mostly clear skies. This will allow
for strong mid-April sunshine to warm western and central North
Dakota into the low to mid 60s on both Saturday and Sunday.
Although the latest suite of model guidance suggests colder
conditions mainly in the 50s, the bias-corrected models have been
about 5 to 10 degrees too cold in most spots the past couple of
days, likely due to a pattern change to warmer weather. The ECM
and MAV MOS guidance has been performing much better, suggesting
highs very close to what has been observed. For these reasons, the
high temperatures for Saturday and Sunday have been manually
increased by 5 degrees or more across all of western and central
North Dakota to account for model guidance likely being too cold.
Chances for light rain and snow return to southern North Dakota
for Monday through early Tuesday morning as a shortwave moves
through from the northwest. Conditions dry back out Tuesday
afternoon and evening as a ridge begins building back in from the
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 850 PM CDT Tue Apr 17 2018
Light rain will spread into central North Dakota this evening
while changing over to snow, leading to MVFR/IFR conditions for
KBIS by 07z and KMOT by 10z. Once MVFR/IFR conditions arrive at
any given terminal, expect those conditions to continue through
the morning with improving conditions in the afternoon. MVFR
conditions currently forecast to not quite reach KJMS.
Area Forecast Discussion
National Weather Service Fort Worth TX
948 PM CDT Tue Apr 17 2018
The forecast is generally in good shape with just a few minor
tweaks to sky and wind grids for the overnight time period.
Satellite imagery at this hour revealed a decent plume of mid and
upper level moisture continued to stream overhead mainly for
locations near and north of I-20. A strong cold front was noted
plowing through the Oklahoma and Texas panhandles at this hour.
Based on pure extrapolation of this feature as well as the latest
3 km NAM, have bumped up the speed of FROPA across the area with
the front now forecast to near the I-20 corridor in the 9-10 UTC
Wednesday time frame and across Central Texas by around 12-13 UTC.
A majority of the colder air looks to lag behind the front
(though it`s likely that adiabatic compression behind the front is
modifying the cooler airmass) and as a result, I`ll not make any
noteworthy changes to overnight lows.
In terms of the sensible weather elements, there may be the
potential for a few sprinkles across the East and across Central
Texas. Low level moisture seems really scarce per our evening
weather balloon, but some of the clouds in the satellite imagery
do have some cumuliform elements so it (sprinkles) can`t be
completely ruled out. I`ve added in a silent 10 PoP across North,
East and Central Texas to account for this. The other element to
monitor during the overnight period into Wednesday morning will be
the possibility for patchy smoke/haze---especially along the Red
River. Experimental HRRR smoke products do suggest that the wind
shift associated with FROPA across Oklahoma will allow the plume
to become more oriented to the east and eventually southeast into
the area. The degree of mixing/dispersion at this time, however,
is unknown and precludes mention in the forecast at this time. If
HRRR guidance becomes more aggressive/consistent with greater
smoke/aerosol concentrations into North Texas, patchy smoke/haze
may be inserted into the forecast.
.AVIATION... /Issued 632 PM CDT Tue Apr 17 2018/
Concerns---Shift from S`ly to N`ly flow (all sites) and MVFR cigs
Visible satellite imagery shows high clouds beginning to
stream over North and Central Texas. These clouds are quite
high...at or above FL250 and should pose no operational impact.
S`ly flow persists this evening as a surface low develops over the
Great Plains. A few low clouds could develop, but moisture should
be sparse enough to preclude any MVFR cigs...but will mention
FEW018 for now. Cold front will approach the Metroplex TAF sites
around 18/1100Z. As front passes...winds will veer sharply out of
the NW at 15-20 KT and any low clouds that may be around will
clear out. High clouds should clear out by Wednesday afternoon
with winds subsiding after sunset.
As for the MVFR possibility at KACT...time-height cross-sections
as well as forecast soundings indicate that just enough boundary
layer moisture should be available for some cloud cover to develop
below FL020 by 18/0900Z. MVFR should not last long however as the
cold front should reach KACT by 18/1400Z...clearing out any low-
level moisture and bringing a return to VFR through the end of the
.SHORT TERM... /Issued 401 PM CDT Tue Apr 17 2018/
Temperatures this afternoon have risen into the lower 80s
southeast to lower 90s northwest as strong warm air advection
takes place across the Southern Plains. This warm air advection is
occurring in response to lee cyclogenesis underway along the Front
Range of the Central Rockies. In the upper-levels, a ridge axis is
making its way through the Central CONUS, with the next trough
axis located through the Great Basin as of this morning. Height
falls as this trough axis propagates eastward should push a cold
front through North and Central Texas late tonight and Wednesday
In the near-term (rest of today), the main concern will be for
elevated fire conditions in the far western counties (west of a
Bowie to Comanche line). Relative humidity values should bottom
out in the 20-25 percent range, along with south-southwesterly
winds of 15-20 MPH, and temperatures near (or even slightly
above) the 90-degree mark. These conditions combined with ERC
values near the 50th percentile suggest that conditions are
modestly favorable for wildfire spread. Strong caution is urged if
using flames outdoors.
Heading into tonight, model guidance is in good agreement with
the timing of the cold front. The cold front should enter our
northwestern counties by 4 AM, then reach the Dallas/Fort Worth
area by daybreak. Precipitation is not expected with this cold
front given the dry air mass that remains in place ahead of it.
While precipitation is not expected, enough low-level moisture
will be in place for some cloud cover to develop ahead of the
front, particularly in our eastern and southeastern counties where
moisture is more abundant (though still shallow). Time-height
cross-sections as well as forecast soundings indicate shallow,
but rich moisture settling in late tonight ahead of the frontal
passage. This should allow for mostly cloudy to overcast skies
generally east of a Sulphur Springs to Hillsboro to Lampasas line.
As the cold front passes, winds will veer out of the northwest at
10-15 MPH. With the exception of the northwestern counties, most
locations should hit their low temperature prior to to the arrival
of the cold front (and even then, cold air advection behind the
cold front should not be particularly robust). Because of this,
most areas will see low temperatures tonight near to slightly
above where they were Tuesday morning. Over the northwest, the
frontal passage will result in lows being about five degrees lower
than last night.
.LONG TERM... /Issued 401 PM CDT Tue Apr 17 2018/
A dry cold will sweep through the region on Wednesday. Veering
surface winds will reduce the already thin moisture across our
southeastern zones, which should have northwest winds by midday,
and no rain chances are expected. Breezy north winds will result
in a noticeably cooler day, but the sunshine should still allow
temperatures to reach the 70s Wednesday afternoon. Dew points will
plunge behind the boundary, and even with the cooler temperatures,
afternoon relative humidity values will likely fall below 25
percent in areas west of the I-35 corridor. But if the vegetation
is green enough to fight off fire initiation today, with
temperatures in the 90s, near normal daytime temperatures are even
less likely to cause fire weather concerns. A seasonally cool
night will follow, and northeast winds should prevent Thursdays`
highs from exceeding Wednesdays`.
The storm system that brought rare hail to the San Francisco Bay
area and is now dropping snow on the Rockies will transit the
Plains well to our north. Our next rainmaker is still over the
Pacific Ocean, dropping south out of the Gulf of Alaska. Though
not yet sampled by the North American RAOB network, satellite data
confirm that is moving equatorward. While it`s still near the 49th
parallel, this motion is improving confidence in the more
southerly track guidance is advertising. There is fairly good
agreement with this upper low becoming separated from the polar
flow. This would tend to slow its eastward progress significantly,
but the progressive pattern overall should prevent it from
As this system crosses the Continental Divide, spreading lift
across eastern New Mexico and West Texas, a fetch of 850mb
moisture will feed afternoon convective development along a
sharpening dryline. It now appears that Friday`s activity may be
west of the New Mexico border, reducing the chances that any of
this will reach North Texas late Friday night. However, as the
upper low spreads large-scale forcing for ascent downstream of
the ongoing convection, a complex of storms will likely survive
overnight into Saturday morning as it invades North and Central
Texas. Additional rounds of rain may significantly disrupt outdoor
activities throughout the day Saturday, and we will prevail
extraordinarily high PoPs for a day 4 forecast. While embedded
strong storms will still appear possible during the day Saturday,
the widespread rainfall should limit the available instability.
For much of the region, the rather dry start to the spring means
that, even with multiple rounds of rainfall during the event,
significant flooding concerns are unlikely. However, the
likelihood of training echoes and the slower speed of the system
overall means that heavy rain may continue into Saturday night in
areas east of the I-35 corridor.
A cold front will invade on Saturday and result in a chilly,
breezy spring day on Sunday. Some postfrontal rain chances will
linger east of I-35 as the upper system plods eastward. Northerly
flow on the backside of the exiting low will maintain below normal
daytime temperatures into the upcoming workweek.
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 61 77 52 76 52 / 10 10 0 0 0
Waco 62 78 50 77 52 / 0 5 0 0 5
Paris 60 73 45 71 47 / 10 10 0 0 0
Denton 58 75 46 74 49 / 10 10 0 0 0
McKinney 60 75 46 73 49 / 10 10 0 0 0
Dallas 62 77 53 76 52 / 10 10 0 0 0
Terrell 61 76 50 74 50 / 10 10 0 0 0
Corsicana 61 76 52 75 51 / 0 10 0 0 0
Temple 61 79 52 77 52 / 0 10 5 0 5
Mineral Wells 58 77 46 77 49 / 0 10 0 0 5