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Area forecast discussion 
National Weather Service Grand Forks ND
1252 PM CDT Friday Jul 3 2015

Update...
issued at 1252 PM CDT Friday Jul 3 2015

Previous grid updates for areas of smoke continue to be
representative as most of the County Warning Area is seeing around 3 sm in haze
visibility right now...with exception of along and south of the I 94
corridor where patchy smoke is the wording. No forecast updates for
first three periods planned as this time.

Update issued at 947 am CDT Friday Jul 3 2015

Main adjustments for morning update concerns smoke. Issued a
Special Weather Statement as smoke is now at the
surface...reducing visibilities...and likely causing health
related irritations to people with those sensitivities. Changed
grids to spatial wording vice probability wording (definite to
areas of). Clear areas today will still appear "cloudy" so will
continue to communicate that to the public.

Update issued at 630 am CDT Friday Jul 3 2015

Most of the visibility restrictions across the region likely more due to
actual fog than smoke...at least looking out the window here at
the office. In fact...a few sites are 1/4sm or less. These
conditions should be short-lived as we are past sunrise.

&&

Short term...(today through saturday)
issued at 350 am CDT Friday Jul 3 2015

Thicker smoke...causing visibility restriction 1sm-3sm...moving into
the region. National oceanic and atmospheric administration air quality forecast guidance suggests thicker
smoke for much of the area today. Lowered maximum temperatures as a
result...and extended smoke in the weather grids through the day. Hrrr
not too excited about shower/thunder potential this
afternoon...and given expected lower maximum temperatures will lower probability of precipitation to
20% across the southern forecast area.

Saturday is still looking like dry weather and warmer...although
temperatures will be dependent on the smoke...which will likely
linger until the cold front moves though Sat night/Sunday.

Long term...(saturday night through thursday)
issued at 350 am CDT Friday Jul 3 2015

Saturday night-Sunday night...convection and severe potential on
Sunday will be the main concern. 00z models still show some
differences with regards to timing of the surface boundary and
instability values (and how quickly stronger deep layer shear will
overspread the region). Most guidance suggests middle to upper 60f
dewpoint values just ahead of the surface boundary...which appears
reasonable given the time of year (evapotranspiration)...and
would lead to MLCAPE 1500-2500 j/kg. Moderate instability will
lead to a marginal risk of severe storms...but widespread stronger
(organized) storms may be limited due to weaker deep layer shear
along and ahead of the surface boundary. The main threat may be heavy
rain with precipitable waters above 1.5 inches...and storms moving parallel to
the surface boundary. More details can be analyzed once this event
gets into the cam guidance timeframe.

Monday-Thursday...upper pattern depicts cutoff low spinning close
to California coast with absence of any long wave ridging over
Continental U.S. During the extended forecast period. Guidance products in
good agreement showing region under influence of zonal flow for
next week. Departing cold front early Monday will usher in
somewhat cooler air poised to keep temperatures about 5 degrees below
average through Thursday. High pressure will give Tuesday the best
shot at a totally dry day before a short wave (timed a bit
differently by GFS/ecmwf) enters the picture Wednesday into
Thursday. Best estimate brings renewed thunderstorms and rain chances to forecast
Wednesday into the first part of Thursday.

&&

Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1252 PM CDT Friday Jul 3 2015

Main issue for the period will be smoke from Canadian
wildfires that has become trapped under the surface high pressure. Visible
have been varying between 1 and 5sm across much of the region...and
think this will continue for a while longer. Have some tempo
improvement at times this afternoon...but think we will not see 3-
5sm or better until light and variable winds start to pick up from
the south later tonight. Air quality models have surface level smoke
hanging around until tomorrow afternoon...so will keep restricted
visible going throughout the period.

&&

Fgf watches/warnings/advisories...
ND...none.
Minnesota...none.
&&

$$

Update...speicher
short term...tg
long term...wjb/tg
aviation...Jr

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