Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service New Orleans la
700 am CST Friday Mar 6 2015

..sounding discussion...

Much drier air has moved over the central Gulf Coast states with
the 24 precipitable water /pw/ change being about -1.4 inches.
Based off the Storm Prediction Center sounding climatology...our precipitable water was near the record
low precipitable water for this date/time. As was the case since yesterday's 12z
sounding...much colder air has arrived...especially below 8000
feet. Overall...the temperature is lower at any given level
compared to 24 hours ago. In fact...the 24 hour temperature change
graph only displays +/-15 celsius. So the 24 hour temperature
change from the surface to 2400 feet is not shown on the graph
since it is in excess of -15. For example...the surface
temperature is 23 degrees celsius lower than yesterday at this
time! Quite impressive. Last thing to mention on temperature is
the elevated inversion from about 1500 to almost 6900 feet. Winds
from the north and northeast prevail below 3000 feet...then winds
rotate around to from the west and west-southwest above that. A
peak wind speed of 118 knots was at 38300 feet.

12z balloon info: no issues with the morning flight which lasted 87
minutes and traveled 81 miles downrange from the office. The
balloon attained a height of 19.5 miles above the ground before
bursting near Helena MS.

Ansorge

&&

Previous discussion... /issued 341 am CST Friday Mar 6 2015/

Synopsis...

Yesterdays cold front is well out into the Gulf of Mexico this
morning with Arctic high pressure extending from Ohio into Texas.
Cold air advection cloudiness is limited to far lower Plaquemines
Parish...and over the Gulf of Mexico. Otherwise...just some
occasional cirrus moving through the upper level southwest flow
across the area. As expected...much of the area away from the
lower Louisiana coast has dropped to near or below freezing this
morning. Current freeze warning looks fine. Still rather
breezy/blustery with 15-20 miles per hour winds being common. This is
producing wind chill values in the upper teens and lower 20s in
many places.

Short term...

High pressure at the surface will sink slowly southward and extend
from Georgia to Texas by Sunday morning. Upper low over Baja California
California will begin to open up and lift eastward on Sunday.
Isentropic upglide will commence during the day Sunday...with
enough moisture available for a chance of rain by late Sunday
afternoon.

With plenty of sunshine expected today into Sunday...will trend
high temperature forecast toward the warmer end of the guidance
envelope. This continues the trend over the last several weeks for
sunny days to be warmer than most guidance. Lighter winds tonight
should allow temperatures to drop to near or just below this
mornings readings. It does appear that any subfreezing lows should
be mainly along and north of the Interstate 10/12 Corridor North
of Lake Pontchartrain. Day shift is likely to reissue freeze
warning for this area for tonight. Threat of a hard freeze is low.
Temperatures Saturday night should remain above freezing across
the entire area. 35

Long term...

European model (ecmwf) and GFS are in fairly decent agreement on the large scale
upper pattern for much of next week...but that does not really
help much in the day to day portion of the forecast. Upper
troughing over Texas will produce south to southwest upper flow
over our area. This will be a rather moist flow with precipitable
water values in the 1.50-1.75 range for much of next week.
Impulses will rotate through the base of the trough and move across
our area. This will produce periods of rain for much of the week.
Timing of individual impulses this far out is rarely consistent
in the medium range models. Will take a blended approach for now
regarding probability of precipitation and quantitative precipitation forecast...with the expectation of being able to
refine timing in later packages. Expect little...if any...sunshine
during the work week next week. Rain amounts during the week next
week are likely to total several inches for much of the area.

Will go with a blend on temperature forecasts...trending toward
the warmer readings until we can refine individual features.
Temperatures will average somewhat below normal...but not the
abnormally cold weather we are currently seeing. No signs of
additional cold snaps through 10 days. 35

Aviation...

VFR conditions through 12z Saturday. Gusty winds south of Lake
Pontchartrain affecting kmsy and knew should abate this afternoon. 35

Marine...

Will keep current advisories in place...and anticipate a gradual
easing of hazardous conditions today. Anticipate exercise caution
headlines across much of the open waters beyond the advisory
period into Saturday morning. A lull in the gusty conditions until
about Monday as easterly surface flow increases with the upper
trough to the west. 35

Decision support...

Dss code...blue.
Deployed...none.
Activation...none.
Activities...slurry support
Small Craft Advisory for marine areas
freeze warning entire area away from la coast

Decision support services (dss) code legend
green = no weather impacts that require action
blue = long fused watch/warning/advisory in effect or high
visibility event
yellow = heightened impacts with short fused
watch/warning/advisory issuances; radar support
Orange = high impacts - slight to moderate risk severe; nearby
tropical events; hazmat or other large episodes
red = full engagement for moderate to high risk severe
and/or direct tropical threats; events of National
significance.

&&

Preliminary point temps/pops...
mcb 52 26 63 40 / 0 0 0 10
btr 54 28 64 40 / 0 0 0 10
asd 55 28 64 41 / 0 0 0 10
msy 52 37 60 47 / 0 0 0 10
gpt 55 31 63 44 / 10 0 0 10
pql 56 28 64 41 / 10 0 0 10

&&

Lix watches/warnings/advisories...
la...freeze warning until 9 am Friday for the following zones:
Ascension...Assumption...East Baton Rouge...East
Feliciana...Iberville...Livingston...northern
Tangipahoa...Pointe Coupee...southern Tangipahoa...St.
Helena...St. James...St. John The Baptist...St.
Tammany...Washington...West Baton Rouge...and West
Feliciana.

Freeze warning until 7 am Friday for the following zones:
Orleans...St. Charles...upper Jefferson...upper
Lafourche...upper Plaquemines...upper St. Bernard...and
upper Terrebonne.

GM...Small Craft Advisory until noon Friday for the following zones:
Breton Sound...Chandeleur Sound...coastal waters from
Boothville la to the Southwest Pass of the Mississippi
River out 20 nm...coastal waters from Pascagoula MS to
Stake Island la from 20 to 60 nm...coastal waters from
Pascagoula MS to Stake Island la out 20 nm...coastal waters
from Port Fourchon to lower Atchafalaya River from 20 to 60
nm...coastal waters from Port Fourchon to lower Atchafalaya
River out 20 nm...coastal waters from Stake Island la to
the Southwest Pass of the Mississippi River from 20 to 60
nm...coastal waters from the Southwest Pass of the
Mississippi River to Port Fourchon from 20 to 60 nm...and
coastal waters from the Southwest Pass of the Mississippi
River to Port Fourchon out 20 nm.

MS...freeze warning until 9 am Friday for the following zones:
Amite...Hancock...Harrison...Jackson...Pearl
River...Pike...Walthall...and Wilkinson.

GM...Small Craft Advisory until noon Friday for the following zones:
Breton Sound...Chandeleur Sound...coastal waters from
Boothville la to the Southwest Pass of the Mississippi
River out 20 nm...coastal waters from Pascagoula MS to
Stake Island la from 20 to 60 nm...coastal waters from
Pascagoula MS to Stake Island la out 20 nm...coastal waters
from Port Fourchon to lower Atchafalaya River from 20 to 60
nm...coastal waters from Port Fourchon to lower Atchafalaya
River out 20 nm...coastal waters from Stake Island la to
the Southwest Pass of the Mississippi River from 20 to 60
nm...coastal waters from the Southwest Pass of the
Mississippi River to Port Fourchon from 20 to 60 nm...and
coastal waters from the Southwest Pass of the Mississippi
River to Port Fourchon out 20 nm.

&&

$$

National Weather Service Glossary of Abbreviations