Area Forecast Discussion
Issued by NWS Bismarck, ND
FXUS63 KBIS 261352 CCA
Area Forecast Discussion...CORRECTED
National Weather Service Bismarck ND
852 AM CDT Sun Mar 26 2017
Issued at 851 AM CDT Sun Mar 26 2017
Latest webcams and surface observations show fog continuing
this morning across the James River Valley. Latest 5 minute
observations at KJMS indicate some improvement to around a
mile and one quarter. Webcam suggests the fog is beginning to
lift now that sunrise has commenced. That said, the dense fog
advisory remains in good standing through 15z/1000 CDT Sunday and
will revisit this in the next hour.
Looking ahead, a weak mid/upper level trough stretching from
western Saskatchewan into central Montana this morning will push
into western ND this afternoon/evening. With some sunshine and
temperatures rising to around 60F in the west this afternoon, high
resolution BUFKIT soundings, HRRR/RAP13 sampled from Crosby to
Williston and Watford City indicate weak CAPE (250-500 J/kg)
developing this afternoon, steep low level lapse rates at 9C/km,
and effective shear around/less than 20KT. The HRRR composite
reflectivities show popcorn type/convective showers developing
between 19z-00z /2PM-6PM CDT. Will re-evaluate this in the next
update for the possibility of adding in isolated showers in the
west this afternoon. Low confidence for any thunder at this time.
UPDATE Issued at 643 AM CDT Sun Mar 26 2017
After coordination with FGF, updated to issue a Dense Fog
Advisory for parts of the James River Valley. Surface observations
and local webcams show very low visibilities due to fog across
that area. We also made small adjustments to pops to account for
the latest radar trends. Short term models still support a
diminishing precipitation trend through the morning.
.SHORT TERM...(Today and tonight)
Issued at 305 AM CDT Sun Mar 26 2017
The main problems in the short term period surround light
precipitation chances today along with clouds and temperatures.
Early morning radar mosaic shows most returns stretching from
southwest North Dakota, though the central part of the state. Have
not seen very many locations report precipitation accumulations
with very dry air in the mid and low levels of the atmosphere
keeping much of the precipitation aloft in the form of virga.
Short term models (HRRR, RAP) suggests the main band of
precipitation / radar returns should diminish this morning and
eventually shrink south into South Dakota. Will continue to carry
mainly chance pops for light rain this morning.
Satellite imagery this morning shows quite a bit of mid and high
level clouds which are helping mask the north and west extent of
the stratus/fog. Observations show the stratus has made it into
Jamestown, and the HRRR would suggest it will spread north and
west a bit more before its progress is halted. Will generally
follow the HRRR and SREF`s idea which keeps the stratus in place
much of the morning across the James River Valley before gradually
eroding it from west to east. This could have some impact on
temperatures, so opted to bring highs a little closer to the more
conservative guidance where the stratus may linger.
.LONG TERM...(Monday through Saturday)
Issued at 305 AM CDT Sun Mar 26 2017
The longer term period will feature a progressive H5 flow with
periodic chances for light precipitation. The GFS and ECMWF
suggest the next best chance of light precipitation will come
Tuesday night into Wednesday, though the NAM keeps the chances
south of North Dakota. Temperatures through the period should
generally be a little above normal with highs in the 40s and 50s
and lows in the 30s.
.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 643 AM CDT Sun Mar 26 2017
IFR cigs and vis will slowly improve at KJMS this morning. There
could also be patchy fog or even a brief period of light rain
this morning at KBIS. Generally went VFR at the other TAF sites.
Dense Fog Advisory until 10 AM CDT this morning for NDZ025-037-