Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
FXUS64 KLIX 230446
Area Forecast Discussion
National Weather Service New Orleans LA
1146 PM CDT Wed Mar 22 2017
Some fog noted at KHUM and KGAO but all other locations are VFR at
this time. Low level winds are expected to not fully decouple to
maintain at least some low level mixing that should curtail
widespread fog developments though locally some patchy radiational
fog may occur briefly before becoming a canopy level stratus deck.
These conditions should burn off by 15Z for VFR conditions through
about 00Z before response to cyclonic sytem in the central Plains
States brings deeper low level moisture and MVFR cloud bases to
the region after 00Z, potentially lowering to IFR in some
locations after 24/06Z. 24/RR
.PREV DISCUSSION... /issued 412 PM CDT Wed Mar 22 2017/
Latest surface analysis showed a weak cold front from North
Florida to Mississippi Coast to west central Louisiana. Surface
dewpoint readings were in the mid to upper 50s north of the
boundary and 60 to 65F south of the boundary. Drying and north
winds have allowed temps to climb especially along the Mississippi.
Surface flow was generally from the northwest. Upper air analysis
showed a general northwest flow from East Coast to the
Mississippi Valley, ridge axis over the Plains and vigorous wave
approaching the West Coast. Isotach at 250mb initialized jet max
of 120 knots on the back side of the wave or off the West Coast.
Frontal zone across the forecast area will become stationary
through Thursday. At the same time, surface trough/low will deepen
as the upper level moves across the Rockies Thursday into Friday.
These features will create a general southeast flow across the
forecast area by mid day Thursday and increase Thursday night into
Upper level wave/trough will track across the Rockies and
evolve into a closed low late Thursday. Max jet streak of 100 to
110 knots will migrate to the base of the trough. While no true
negatively tilt occurs with this system, one strong disturbance
will rotate around the low and across Louisiana and Mississippi.
Surface base cape will increase across the west zones Friday
afternoon with values 300 to 600 j/kg. Will insert slight chance
of showers in the morning and add slight chance of thunderstorms
Low level southeast to south flow and southwest flow aloft will
increase 0-3km helicity values 200 to 350 m/s Friday evening
through early Saturday mainly across the north half of the
forecast area. Cape values do increase with values of 300 j/kg
across southwest Mississippi to 1000 j/kg along the Louisiana.
With the disturbance rotating southeast through the forecast area
Friday night a few storms may contain damaging winds and/or one or
two tornadoes. As for hail, 500mb temps may dip to -17F across
northwest zones by Saturday. As a result, a few storms may contain
hail, but cold core lags behind the disturbance but forcing may
yield a few hail storms ahead of the cold core.
With no true frontal passage over the weekend, low level moisture
will remain in play. However, mid layer moisture will be pushed
east provide a break on Sunday. A short wave will rake across the
north zones on Monday yielding a few storms, but these storms
should remain below severe limits. Meanwhile in the latter part of
the forecast, a very strong system will approach the Lower
Mississippi Valley late Wednesday into Thursday. While 7 to 8 days
away, the pattern does support a round of strong to severe across
the forecast area late next week. It is that time of year.
VFR conditions are expected to prevail through most of the period.
Lower cigs and vsbys will be possible near daybreak, resulting in
mvfr or even ifr conditions for a few hours.
Wind field should remain quiet for about the next 24 hours. Once
the next system moves out of the Rockies sometime Thursday, the
pressure gradient will tighten. Winds are expected to become
southeasterly by late Thursday, and we will likely need Small
Craft Exercise Caution headlines in at least our far eastern
waters at that point. By sunrise Friday, most all waters should
have the SCEC headline or a Small Craft Advisory. These conditions
likely to continue into Saturday before easing.
Decision Support Service (DSS) Code Legend:
GREEN = No weather impacts that require action
BLUE = Long fused Watch/Warning/Advisory in effect or high
YELLOW = Heightened impacts with short fused
Watch/Warning/Advisory issuances; Radar support
ORANGE = High Impacts - Slight to Moderate risk of severe weather;
Nearby tropical events, HAZMAT or other large episodes
RED = Full engagement for moderate risk of severe weather; Direct
tropical threats; events of national significance.
.PRELIMINARY POINT TEMPS/POPS...
MCB 57 83 63 77 / 0 10 10 20
BTR 58 84 66 80 / 0 10 10 20
ASD 60 79 65 78 / 0 10 10 20
MSY 63 79 67 79 / 0 10 10 20
GPT 61 76 65 73 / 0 10 10 20
PQL 60 75 63 74 / 0 10 10 20