Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/05/18
Area Forecast Discussion
National Weather Service Bismarck ND
729 PM CDT Thu Oct 4 2018
.UPDATE...
Issued at 728 PM CDT Thu Oct 4 2018
Based upon radar trends, put the Winter Weather Advisory into
effect now instead of 1 AM CDT for Ward, McHenry, Bottineau
counties. Also added McLean county to the Advisory.
UPDATE Issued at 704 PM CDT Thu Oct 4 2018
Snow and fog tonight through Friday morning highlight this update.
A band of moderate snow in a zone of low level moisture transport
and ascent along isentropic surfaces continues across most of
central and into portions of southwest North Dakota as of 2345
UTC. At precipitation onset on the leading edge of the band, the
precipitation type is quickly changing to all snow with wet-bulb
cooling. Some sleet may mix in with the snow far south central
with partial melting with a weak warm layer aloft. The rapidly
updating guidance through the 22 UTC HRRR have a good handle on
this band of precipitation, and will follow their consensus for
PoPs through the night and into Friday. Do expect snow to
decrease across the south central into next 1-2 hours as
precipitation focuses generally north of I-94 and east of North
Dakota Highway 8. Snowfall amounts are relatively unchanged with
this update, with no change to the Winter Weather Advisory needed
at this time. A secondary band of mostly snow is expected to enter
western North Dakota late tonight, and move east through central
North Dakota Friday morning with a shortwave that is currently
across western Montana.
The HRRR/RAP/NBM/GFSLamp through their 22 UTC iterations favor fog
formation through the night across southwest North Dakota with
favorable southeasterly winds. A Dense Fog Advisory could be
needed late tonight into Friday morning. Will also monitor the
potential for light freezing drizzle southwest and south central
tonight into Friday morning with possible ice loss in the column.
&&
.SHORT TERM...(This evening through Friday)
Issued at 222 PM CDT Thu Oct 4 2018
The short term will be a bit more complex because of a two
pronged shortwave pattern expected to impact west and cental
North Dakota over the next 24 hours.
First, a warm advection pattern is currently supporting
precipiation moving into south central North Dakota. WAA pattern
associated with a shortwave, originally over northwest Arizona
this morning, now approaching the northern plains. A mix of rain
and snow is expected to start south and move north, changing to
mainly all snow this evening and overnight. Three to 5 inches of
snow still seems reasonable over the Devils lake Basin south
through the Northern James River Valley.
A second shortwave trough, over northern California, will track
northeast and spread snow over northwest and far north central
North Dakota, starting about 6 to 8 hours later or around
midnight. For this added a second area to the winter weather
advisory across the northern tier of counties, starting just after
midnight midnight through 11 am CDT Friday.
.LONG TERM...(Friday night through Thursday)
Issued at 222 PM CDT Thu Oct 4 2018
Friday night and Saturday will see a break in the wintry weather
for a short time, as the large upper level low slowly
consolidates across the western CONUS. Again, lowered minimum
temperatures across the region Saturday morning, with a surface
high moving over some fresh snow cover should be colder than the
SuperBlend guidance suggests.
While the global models seem to be slowly converging to a
solution, there are some differences on the scenarios. The GFS
continues to be a bit more intense than the ECMWF. Both models
agree on spreading snow and rain onto west and central North
Dakota Sunday night and through Tuesday. After which the ECMWF
becomes drier. Much uncertainty continues for the middle to later
part of next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 728 PM CDT Thu Oct 4 2018
Multiple aviation hazards across western and central North Dakota
tonight through Friday. A band of moderate snow with IFR/LIFR
visibility will impact most of central North Dakota this evening
and tonight. Sleet may mix with the snow south central this
evening. Widespread IFR/LIFR stratus will encompass all of the
west and central tonight through Friday morning. LIFR/VLIFR fog
may develop southwest and south central tonight into Friday
morning. Patchy freezing drizzle is also possible for these areas.
A second band of snow will enter western North Dakota late tonight
and move east across central North Dakota Friday morning.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon CDT Friday for NDZ004-005-
011>013-021>023-025-036-037.
Winter Weather Advisory from 1 AM to noon CDT Friday for
NDZ001>003-009-010.
&&
$$
UPDATE...PA
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...PA
Area Forecast Discussion
National Weather Service San Francisco Bay Area
655 PM PDT Thu Oct 4 2018
.SYNOPSIS...Isolated showers will linger through late this afternoon
before dry conditions return to the region this evening. A further
drying and slight warming trend is forecast through the weekend with
the potential for offshore winds at times, especially in the hills.
Seasonable weather conditions are likely through the remainder of
the forecast period.
&&
.DISCUSSION...as of 01:53 PM PDT Thursday...Short term impacts
continue to be focused around the passing upper level
trough/shortwave and associated showers. Some afternoon clearing,
daytime heating and passing upper level disturbance has led to a
slightly unstable atmosphere with cumulus clouds on satellite.
KMUX imagery continues to indicated a few scattered convective
showers passing from west to east. Latest hi-res HRRR model output
continues convective showers through at least 00Z this evening
then diminishing as the sun sets. Current forecast reflects this
thinking. Given the hit or miss shower activity rainfall amounts
will vary greatly. Developed showers could produce a quick few
hundredths.
By tonight precip chances end with some clearing as the upper level
disturbance shifts eastward. Given the recent rains, moist low
levels and decreasing winds added some patchy fog to the forecast
around Monterey Bay coastline and the North Bay Valleys.
Warmer and drier conditions are expected on Friday with warming
850mb temps and rising 500mb heights as the trough exits to the
east. Highs will still be seasonably cool even with highs in the
70s and 80s for most locations.
Over the weekend model output continues to advertise an insider
slider scenario with an upper level trough sweeping through NE
NorCal. There could be a few showers over the Sierra, but at this
point the Bay Area looks dry. More importantly, this scenario
typically results in gusty north winds. Hi-res WRF model shows this
to be the case as N to NE winds of 15 to 30 mph develop over the
higher terrain with gusts up to 45 mph. Peak winds appear to be
Saturday night into Sunday morning. If this trend keeps up on the
model data a wind advisory may be need for portions of the North Bay
Mts and East Bay Hills. Additionally, the north winds will enhance
the warming and drying across the Bay Area for both Saturday and
Sunday. From a fire stand point, the recent rains have moistened
the finer fuels keeping the fire threat in check. If anything,
these winds will help to dry out the fine fuels.
Next week remains dry at this point as a trough remains over the
Great Basin and high pressure remains off the West Coast. Did trend
to warmer temperatures for much of next week.
&&
.AVIATION...as of 7:00 PM PDT Thursday...Upper level trough
moving through the area is bringing variable clouds to the area
this afternoon. Bases are generally around 4000 feet but a weak
front will bring brief MVFR cigs over SFO and OAK. These clouds
will dissipate after 03Z. Additional low cloud development is
less likely tonight as the airmass will be much drier. However
patchy fog could form around STS.
Vicinity of KSFO...SCT-BKN clouds around 4000 ft briefly lowering
to 1500 ft which may impact visuals approaching terminal through
03Z. West winds to 15 kt diminishing after 04Z. VFR after 03Z.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...Scattered cumulus clouds clearing out
after 03Z. IFR cigs return after 05Z.
&&
.MARINE...as of 06:51 PM PDT Thursday...Northwest winds will
steadily strengthen tonight and through the upcoming weekend.
Gale force winds will be possible by Saturday Afternoon into
Sunday as wind speeds peak. These winds will bring steep fresh
swell to the waters in the coming days. Otherwise, seas mixed
with moderate to longer period northwest and southerly swells.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm from 3 AM
SCA...Pt Arena to Pt Reyes 0-10 nm until 9 PM
&&
$$
PUBLIC FORECAST: MM
AVIATION: W Pi
MARINE: DRP
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